GB2187748A

GB2187748A - Bleaching fabrics

Info

Publication number: GB2187748A
Application number: GB08605733A
Authority: GB
Inventors: Geoffrey Newbold; Douglas Wraige
Original assignee: Unilever PLC
Current assignee: Unilever PLC
Priority date: 1986-03-07
Filing date: 1986-03-07
Publication date: 1987-09-16
Also published as: GB8605733D0

Abstract

Fabrics in an automatic washing machine are bleached by means of peroxomonosulphate, or hypohalite generated by the reaction between peroxomonosulphate and halide, the bleaching agent being released into the wash liquor after a delay of at least 5 minutes and/or in a controlled gradual manner. Controlled and/or delayed release may be achieved by means of a sachet of suitable construction, e.g. a sachet having two compartments, the first of which contains a halide and, optionally detergent components such as an enzymatic detergent, and the second compartment containing peroxymonosulphate. Alternatively, the peroxomonosulphate or halide may be coated or encapsulated with a sparingly soluble or temperature-sensitive coating or encapsulant prior to its incorporation into a detergent powder.

Description

SPECIFICATION Process and product for bleaching fabrics in a washing machine Technical field of invention The present invention relates to a process for bleaching fabrics during the laundering process in a washing machine. The bleaching agent employed is a peroxomonosulphate, or hypohalite (preferably hypobromite) generated by the reaction between peroxomonosulphate and halide (preferably bromide), and according to the invention the bleaching agent is released into the wash liquor after a delay, or in a controlled gradual manner, resulting in reduced dye damage to the fabrics.

Background and prior art Peroxomonosulphate, also known as monopersulphate or MPS, is a known bleaching agent for fabrics. The bleaching of fabrics with products containing MPS together with alkali metal halide (chloride or bromide) is disclosed, for example, in GB 1 477 546 (Unilever) and US 4 028 263 (Gray/Colgate-Palmolive Co).

In such products, MPS reacts with alkali metal halide (bromide being preferred) in the wash liquor to generate hypohalite which is a more powerful bleach than MPS itself, but which is liable to cause fabric and dye damage, especially at high local concentrations. According to the abovementioned GB 1 477 546, such damage is reduced by including in the product a minor amount of a nitrogen-containing compound, for example, urea, as a hypobromite scavenger. According to US 4 028 263 mentioned above, certain sulphonamides are present as hypobromite scavengers.

MPS itself can also cause dye damage at pH values above about 9. Another problem which has to be considered when MPS is incorporated in detergent compositions is that it deactivates enzymes. The MPS/bromide system is an even more powerful enzyme deactivator.

The present invention represents a route by which MPS, with or without halide, can be utilised effectively in the wash process, even when enzymes are present, without giving rise to unacceptable levels of dye or fabric damage.

Summary of invention In a first aspect, the invention provides a process for bleaching fabrics in a washing machine, wherein fabrics in an aqueous wash liquor having detergent components dispersed or dissolved therein are treated with water-soluble peroxomonosulphate, or with hypohalite (preferably hypobromite) generated by reaction between peroxomonosulphate and a water-soluble halide (preferably bromide), the peroxomonosulphate or hypohalite being delivered to the wash liquor after a delay of at least 5 minutes, preferably at least 10 minutes, from the start of the wash process and/or being delivered gradually to the wash liquor.

In accordance with a preferred embodiment of the invention, peroxomonosulphate (MPS) and/or halide is delivered to the wash liquor from a sachet or sachet compartment so constructed as to deliver its contents gradually and/or after a delay of at least 5 minutes from the start of the wash process.

An especially preferred embodiment of the invention is a product for bleaching fabrics in an automatic washing machine, the product comprising a sachet having at least two compartments, including (a) a first compartment containing a water-soluble halide and optionally detergent components, the first compartment being capable of releasing its contents into the wash liquor of a washing machine within a period of 3 minutes, preferably within 1 minute, from the start of the wash process; and (b) a second compartment containing a water-soluble peroxomonosulphate, the second compartment being so constructed as to release its contents gradually and/or after a delay of at least 5 minutes, preferably at least 10 minutes, from the start of the wash process.

Detailed description of invention The essential feature of the invention is that MPS, or hypohalite (preferably hypobromite) generated in situ by the MPS/halide (preferably bromide) reaction, is delivered to the wash liquor either gradually or after a delay, or both. For the purposes of the present invention the start of the wash process should be understood as the time at which the water fill is substantially complete and full agitation commences. Any period of static heat-up, and any short bursts of agitation before water fill is complete, are regarded as occurring before the start of the wash process.

When no halide is present, the component that is delivered gradually and/or after a delay is MPS. In a system utilising both MPS and halide, these materials are segregated until the point of use, and then either or both can be delivered gradually and/or after a delay so that hypohalite, formed in situ from the reaction between them, is generated only gradually and/or after a delay.

In principie either halide or MPS can be delivered gradually and/or after a delay, but in practice it is usually preferred that the MPS be delivered in this manner while the halide is present ab initio in the wash liquor. The reason for this preference will be discussed in more detail below.

The MPS may be in the form of any water-soluble salt: alkali metal salts, especially the potassium salt, are preferred. The potassium MPS/potassium sulphate/potassium bisulphate triple salt commercially available from Interox is conveniently used.

In embodiments of the invention in which a halide is present, this is preferably the bromide, although other halides may in principle be used. The halide may be in the form of any watersoluble salt, for example, an alkali metal, ammonium, magnesium or calcium salt Alkali metal (preferably sodium or potassium) and ammonium salts are especially preferred.

The delay or retardation of the delivery of the MPS (or bromide) may be achieved, for example, by coating or encapsulating that component with a sparingly soluble or temperaturesensitive coating or encapsulant. The coated or encapsulated component can then be included in a detergent powder.

According to a preferred embodiment of the invention, however, delayed or retarded delivery is achieved by means of a sachet of suitable construction. Thus the simplest possible embodiment of the invention is a single sachet containing MPS, the sachet being so constructed as to release the MPS gradually and/or after a delay of at least 5 minutes after the start of the wash process. Sachet constructions capable of giving such delayed and/or retarded release will be discussed in more detail below.

An especially preferred embodiment of the invention is a sachet having at least two compartments, one of which contains the component whose release is to be delayed or retarded, and another containing other components: the two compartments will be of different construction so as to ensure different release characteristics.

This sachet product may be a wash adjunct intended to boost the cleaning performance of a conventional detergent powder which is dosed into the machine via the dispenser.

In its simplest form, the wash adjunct of the invention will contain two compartments, a first compartment constructed so as to give immediate release and a second compartment constructed so as to give delayed or retarded release. One compartment contains MPS and the other alkali metal bromide, and it is immaterial which component is released first.

A variant of this concept is a wash adjunct that also includes enzyme. As mentioned previously, enzymes are deactivated by MPS, so the enzyme must be segregated from the MPS, i.e.

packed together with the bromide in a two-compartment product or located in a third compartment. In this variant, the enzyme should be released rapidly; the bromide can also be released rapidly (optionally from the same compartment) or its delivery can be delayed or retarded (obviously from a different compartment); and the delivery of the MPS must be delayed or retarded.

Another two-compartment wash adjunct within the scope of the invention could simply contain enzyme in a rapid release compartment and MPS in a delayed or retarded release compartment.

Also within the scope of the invention are sachet products intended entirely to replace conventional detergent powders, and thus containing in effect a fully formulated detergent powder. In this case, the main detergent components should be located in one or more rapid release compartments while the component or components whose release is or are to be delayed and/or retarded is or are located in one or more separate, suitably constructed compartments.

In a whole wash sachet product of this type it is important to keep the MPS segregated from the main detergent powder, because, as previously mentioned, MPS at high pH causes dye damage, and there will be a region of localised high pH at the area of delivery of the main detergent powder. If enzymes are present, it is also highly desirable that the delivery of MPS to the wash liquor- (whether or not bromide is also involved) be delayed until the enzymes have had time to work on the soiled fabrics. Thus when enzymes are involved, a delay or induction period of at least 5 minutes is strongly preferred: retardation alone may not be sufficient to prevent enzyme deactivation.Furthermore, MPS in solution is acidic but is an effective bleach only at high pH, so its entry into the wash liquor is best delayed until the main detergent components have had time to raise the pH of the wash liquor to the usual value of 9-10. For all these reasons, it is preferred that, in a whole wash product involving both MPS and bromide, the component to be delivered after a delay be the MPS. Of course the bromide could also be delivered in this manner if desired, but there is no reason why the bromide should not be mixed with the main detergent components and delivered rapidly with them to the wash liquor.

Essential to all sachet embodiments of the present invention is a sachet construction that will give delayed or retarded release characteristics. Preferably this sachet or sachet compartment is of the non-opening porous water-permeable type, so that its contents are released by a leaching-out mechanism. This mechanism can be delayed or retarded by various means, in particular, the provision of a pore-occluding external coating or layer that will be disrupted by the wash liquor, and/or a double wall construction that ensures that leaching out must occur through two thicknesses of porous wall material. Suitable pore-occluding coatings include fatty acids, for example, stearic acid; fatty acid/polyethylene glycol mixtures; and long-chain nonionic surfactants, for example, tallow alcohol ethoxylates.The double wall construction may be achieved by enclosure within a further sachet (sachet-within-a sachet construction).

In multicompartment sachet embodiments of the invention, any compartments required to release their contents rapidly may of of an opening or non-opening type. They may, for example, be provided with seals sensitive to water, temperature or agitation, or they may be closed compartments of material highly permeable in the wet state to water.

Two-compartment sachet constructions highly suitable for use in the present invention are disclosed and claimed in our copending application of even date (Case C.3105).

Description of preferred embodiments Embodiments of the invention will now be described, by way of example only, with reference to the accompanying drawings in which: Figure 1 is a plan view of a sachet product in accordance with the invention; and Figure 2 is a section, on a larger scale, along the line ll-ll of Fig. 1.

Referring now to Fig. 1 of the accompanying drawings, a two-compartment sachet 1 has a large first compartment 2 and a smaller second compartment 3. The sachet is made of Crompton (Trade Mark) 784 tea bag paper, which is a cellulosic material containing thermoplastic (polypropylene) fibres to render it heat-sealable. The second compartment 3 is bounded by strong heat-seals 4 that will not open in the wash liquor, while the remaining three edge seals 5 of the first compartment 2 are formed by a water-soluble adhesive, sodium carboxymethylcellulose.

The second compartment 3 contains an inner sachet 9 of water-permeable material, Kimtex (Trade Mark) polypropylene nonwoven fabric.

Referring now to Fig. 2, the inner sachet 9 is coated externally with a pore-occluding layer 6 of water-soluble or water-dispersible material, for example, a coating of tallow alcohol 18 EO.

The first compartment 2 contains a first powdered composition 7, comprising, for example, a non-bleaching enzymatic detergent base powder and sodium bromide, and the inner sachet 9 contains powdered potassium peroxomonosulphate triple salt (MPS) 8. In use the sachet is placed together with the load in a washing machine. The first compartment opens very rapidly along the edges 5 and releases its contents within 1 to 3 minutes from the start of the wash process. The base powder, enzymes and bromide are released to give a non-bleaching wash liquor, and the enzymes are free to act on the soiled fabrics without interference from a bleach.

In the meantime the coating 6 on the inner sachet 9 gradually dissolves and after a delay of about 5-15 minutes from the start of the wash process the walls are sufficiently exposed for leaching out of the MPS to begin. The MPS enters the wash liquor and reacts with the sodium bromide to generate sodium hypobromite without the build-up of high local concentrations, so that effective bleaching occurs without significant dye damage.

The sachet product described above is of such a size than a single unit will deliver an appropriate quantity of ingredients for a single washload. Greater flexibility for the consumer may, however, be achieved if smaller sachets are produced in groups, for example, of two to six units, readily separable by tearing along perforated marginal regions.

EXAMPLE 1 An experiment was carried out to determine the release times of the two compartments of the sachet described above with reference to Figs. 1 and 2 of the accompanying drawings. The main sachet 1 was made of Crompton (Trade Mark) 784 tea bag paper ex Crompton, and had overall dimensions of 15 cmx 15 cm. The first compartment contained 107 g of non-bleaching detergent powder and 3.6 g of sodium bromide, and was sealed with detergent-grade sodium carboxymethylcellulose. The inner sachet 9, of Kimtex (Trade Mark) polypropylene nonwoven fabric ex Kimberly-Clark, had dimensions of 13 cmx5 cm and contained 18 g of potassium peroxomonosulphate triple salt ex Interox. The inner sachet 9 had an outer coating of 200 g/m2 (2.6 g in total) of tallow alcohol 18 EO (Lutensol (Trade Mark) AP 18 ex BASF).

Six washing machine experiments were carried out to determine the time taken for the inner sachet 9 to release its contents. A Miele (Trade Mark) De Luxe Electronic 756 washing machine set to the 40"C economy programme was used, with a mixed load of 2.5 kg of clean cotton and synthetic fabrics.

In each run the detergent powder was completely delivered from the first compartment within a period of 30 seconds to 1 minute from the start of the wash process. Delivery of substantially all of the MPS from the second compartment took place in each run after a delay of about 5 to 10 minutes, as can be seen from the Table below. This period can be lengthened or shortened by varying the type and level of coating on the inner sachet 9.

MPS released Time (Mins) (grams) 1 3 5 7 10 15 Run 1 0 0 1.4 15.6 18.0 Run 2 0 0.2 2.1 18.0 18.0 Run 3 0 0 4.0 12.8 18.0 Run 4 0 0 3.6 18.0 18.0 Run 5 0 0.4 1.7 18.0 18.0 Run 6 0 0 0.9 15.4 18.0 Run 7 0 0 0 2.4 15.6 18.0 Run 8 0 0 0 3.4 17.1 18.0 Run 9 0 0 0 2.1 13.0 18.0 EXAMPLE 2 An experiment was carried out to compare the dye damage obtained using a sachet product as described in Example 1, with that obtained using a control sachet product in which the same ingredients, in the same quantities, were mixed together in a single compartment.

Two identical wash loads were prepared, each containing four approximately 1 m2 red cotton test cloths mixed with clean white cotton towels to give a total load of 2.5 kg. The two loads were each placed in a Miele 423 washing machine, together with the relevant sachet product, and washed using a heat up to 40"C cottons programme (25 minutes' wash time) in 18 litres of 24"H water.

The control sachet delivered all its contents within 1 minute of the start of the wash process.

At the end of the wash, all four red test cloths showed visible heterogeneous dye damage.

The sachet product of the invention delivered the contents of the first (opening) compartment within 1 minute of the start of the wash process. The MPS in the second compartment was delivered after a delay of 5-10 minutes. At the end of the wash, no visible heterogeneous dye damage was detected on any of the four red test cloths.

Claims

1. A process for bleaching fabrics in a washing machine, wherein fabrics in an aqueous wash liquor having detergent components dispersed or dissolved therein are treated with a watersoluble peroxomonosulphate, or with a hypohalite generated by reaction between peroxomonosulphate and a water-soluble halide, the peroxomonosulphate or hypohalite being delivered to the wash liquor after a delay of at least 5 minutes from the start of the wash process and/or being delivered gradually to the wash liquor.

2. A process as claimed in claim 1, wherein the detergent components in the wash liquor include enzyme, and the peroxomonosulphate or hypohalite is delivered to the wash liquor after a delay of at least 5 minutes from the start of the wash process.

3. A process as claimed in claim 1 or claim 2, wherein peroxomonosulphate and/or halide is delivered to the wash liquor from a sachet or sachet compartment so constructed as to release its contents gradually and/or after a delay of at least 5 minutes from the start of the wash process.

4. A process as claimed in claim 3, wherein peroxomonosulphate and halide are delivered from different compartments of a sachet having at least two compartments.

5. A process as claimed in claim 4, wherein halide, optionally together with other detergent components, is delivered relatively rapidly from a first compartment of a sachet, and peroxomonosulphate is delivered, gradually and/or after a delay of at least 5 minutes from the start of the wash process, from a second compartment of the sachet.

6. A process as claimed in any preceding claim, wherein the halide comprises an alkali metal or ammonium bromide.

7. A product for bleaching fabrics in an automatic washing machine, the product comprising a sachet having at least two compartments, including (a) a first compartment containing a water-soluble halide and optionally detergent components, the first compartment being capable of releasing its contents into the wash liquor of a washing machine within a period of- 3 minutes from the start of the wash process; and (b) a second compartment containing water-soluble peroxomonosulphate, the second compartment being so constructed as to release its contents gradually and/or after a delay of at least 5 minutes from the start of the wash process.

8. A product for bleaching fabrics in an automatic washing machine, substantially as hereinbefore described with reference to, and as shown in, Figs. 1 and 2 of the accompanying drawings.