GB2319536A - Hydroperoxide bleaching - Google Patents

Abstract

A method of bleaching comprises reaction of a hydroperoxide, preferably primary or secondary, characterised in that the hydroperoxide is formed, without the use of an oxidant other than atmospheric oxygen, in situ in a buffered alkaline aqueous liquor. The method may be used in laundry bleaching where the elimination of a chemical source of oxygen such as sodium perborate gives the advantage that the composition is more compact. The reaction may be hydroperoxydeamination of an N-tosylated hydrazine. A laundry detergent composition capable of being added to water to generate an alkaline wash liquor includes 0.001-5% of an N-tosyl hydrazine.

Description

BLEACEDNG USING HYDROPEROXIDES This invention relates to a method of bleaching which uses hydroperoxide formed in situ.

Bleaching using hydroperoxides such as cumene and tbutyl hydroperoxide is knowrL These processes often require high temperatures and are unsuitable for many bleaching applications, for example low ten laundry washing. Furthermore, these hydroperoxides and the more reactive primary and secondary types are not sufficiently storage stable for a consumer product.

US 3746646 (Colgate) proposes use of a sodium salt of cumene hydroperoxide in a boil wash laundry detergent composition DE 2128723 (Atlantic Richfield Co) proposes use of tertiary butyl hydroperoxide for pulp bleaching.

Papeterie (1969), 91(6), 558-62 descnbes the use of cumene hydroperoxide for pulp bleaching.

Results from in situ preparation of this hydroperoxide are said to be variable compared with addition of hydroperoxide prepared extemaXy by autooxidation of cumene in alkaline emulsion A paper by Collazo, L., Guziec, F.S., Hy W-X Munoz, A, Wei D. and Alvarado, AL, (1993). J Org. Chem 58. 6169-6170 proposes conversion of N substituted N-Sulphonylhydrazines to hydroperoxides by hydroperoxydeamination. This is done by treatment with a strong base (potassium ethoxide - KOEt) in ethanol at 12 C for 17 hours. The source of oxygen is air diffilsing into the reaction mixture.

In order for this reaction to be of use in many of the common bleaching processes, particularly domestic processes such as laundry washing, it is necessary to generate the hydroperoxide bleaching species at a lower temperature and under conditions of lower alkalinity. The timescale for generation of sufficient bleach to provide a detectable effect must also be much shorter than 17 hours for most processes.

According to the present invention there is provided a method of bleaching comprising reaction of a hyperoxide, viably primary or secondary, characterised in that the hydroperoxide is formed, without the use of an oxidant other than atmospheric oxygen, in situ in a bred alkaline aqueous liquor.

Preferably the hydroperoxide is formed by hydroperoxydeamination, more preferably using the corresponding N substituted NSulphonylhydrazines by air oxidation in basic aqueous conditions at a temperature in the range of from about 20 C to about 50 C. Most preferred among the N substituted N-Sulphonylhydrazines are N-tosyl hydrazines.

Acryl hydrazines are prepared over aByl hydrazines for stability reasons. Although the alkyl hydrazines, such as Mosyl dodecyl hydrazine, may be successfully converted to the hydroperoxide it completely decomposes within 24 hours and would appear to be unsuitable for a commercial product. Two prior art aryl hydroperoxides viz. 2,(4'-chlorophenyl)ethyl hydroperoxide and 2,(4' rinhoxyp-)- hydroperoxide use expenxve, class 1 compounds as starting materials. Hence, the less expensive, unclassified benzyl product is preferred.

The pH of the buffered alkaline aqueous liquor advantageously lies in the range 7 to 12 and a particularly useful liquor comprises a solution or dispersion of a detergent base. A solvent, such as an organic solvent, may be used for some applications.

Also according to the present invention there is provided a method of bleaching a substrate comprising the reaction of a hydroperoxide, preferably primary or secondary, formed insane by alkaline catalysed hydroperoxydeanination of an N-tosylated hydrazine. The substrate may with advantage be laundry or other textile goods.

The hydroperoxide bleaching may be boosted by the use of transition metal catalysts as oxygen transfer agents.

The invention also comprises a laundry detergent composition capable of being added to water to generate an alkaline wash liquor characterised in that the composition includes from 0.001 to 5 % of an N-tosyl hydrazine.

This novel bleaching system is capable of working in aqueous solution at alkaline p, using atmospheric oxygen as oxidant and without an activator being present This provides advantages over the known bleaching systems which use a bulky combination of a persalt such as perborate or the rively less stable percarbonate in combination with a bleach activator such as TAED to give low temperature bleaching performance.

N-tosyl hydrazines can be formed from amines as described in the prior art. The general reaction mechanism scheme for the generation of hydroperoxides starting from amines is also described in the prior art. The amines used in the prior art include:

We prefer

Detection of Hydroperoxides Infra-Red spectroscopy can be used to detect the OH and O-O stretches at approximately 3300 and 830 cm-l respectively and also to prove that the tosyl group has been removed (loss ofthe stretch at 1335 cm present in the tosylated hydrazine). Hence this technique can be used to indicate the presence of a hydroperoxide.

TLC detection methods were also used. Using a solvent phase of 2:1 toluene to ethyl acetate fbllowed by dipping the plate in Wurste?s reagent results in pink spots for the hydroperoxide. The hydrazine product also gives a sligtit pink spot which disappears on wangling (up to 1000C), whereas the hydroperoxide spot becomes more intense.

HPLC analysis was performed on samples of benzyl hydroperoxide from different synthetic route, and the resulting profiles compared The spectra of a peak at 3.0 minutes common to all samples were compared and found to match This peak was assumed to be that of benzy1 hydroperoxide.

This seems a reasonable assumption to make since a standard of cumene hydroperoxide elutes at 3.15 minutes. Idenntication ofthe benzyl hydroperoxide peak in HPLC analysis makes it possible to quantify yields ofthe hydroperoxide formed via the hydroperoxydeamination route.

Peroxide detection sticks (Trade name: Quantofix Peroxide 25: manured by Macherey-Nagel D52348, Düren and available from Aldrich) turn blue (corresponding to values of 10-25 mg/L of peroxide) when dipped into the solution of the hydroperoxide product prior to extraction with CH These sticks rely on a chemical test and are suitable for hydrogen peroxide and for organic hydsperoxides. Although not precise, they provide a means of estimating how much hydroperoxide has be generated in the reaction Ihey are suitable for the determination of hydrogen peroxide and organic hydroperoxides in the concentration range 1-25 mg/L and over a pH range of 2-12 (over which they are independent of pH). The test involves dipping the stick into the test solution for 1 second, shaking off excess solution and waiting for a father 15 seconds before comparing the colour ofthe test paper zone with a calibration scale. A blue colour represents a positive test. When the test solution is in an organic solvent, this is first evaporated off before 1 drop ofwater is added to the test zone and the colour that develops after 15 seconds isjudged as before.

The invention will now be desabed by way of example only and with reference to the following non limiting examples.

Example 1- Reduced Reaction times and Hither Temperatures IR spectral analysis of aliquots taken at 15 minute intervals during the conversion of N-tosyl-2-(4'- chloropheny)ethyl hydrazine into hydroperoxide using the prior art 120C process scaled up to a total volume 600 aif showed that the hydroperoxide was present at 15 minutes.

The experiment was then repeated at the higher temperatures of 25 C and 40 C (possible bleaching process temeatres). For these experiments the N-tosyl-2-(4'-methoxyphenyl)ethyl hydrazine was used at double the previous scale (i.e. 3.2 x 10-3 mole). The experiment was run over 1 hour and samples were removed for TLC analysis every 5 minutes. After 1 hour the reaction was quenched and worked up. IR spectra of the final products from the reaction at both temperature showed them to be the hydroperoxide. For the experiment at 25 C, the TLC plates showed that hydroperoxide was present after 5 brutes and the final 1 hour sample did not show any signs of residual hydrazine.

Similar results were found at 40 C and the increased temperature did not seem to decompose the hydroperoxide over the course ofthe reaction This shows that the reaction is possible within useful timescales at the higher temperatures and that a filler conversion and therefore cleaner product might result.

Example 2 - Incolporaton of Water Into the System This example investigates the effect of water on the conversion of hydrazines to hydroperoxides.

Since the hydizines are only sparingly soluble in water, it was decided to do an initial experiment in a 50% ethanolic solution at 40 C. The hydrazine (N-tosyl-2*'-methoxyphenyl)ethyl hydrarrne) was dissolved up in ethanol whilst the potassium ethoxide was dissolved in the water faction and added over a 10 minute period; some of the potassium ethoxide will be present as potassium hydroxide under these conditions. The hydrazine appeared to remain in solution throughout the experiment As before, samples were removed at 5 minute intervals for TLC analysis and after 1 hour the reaction was quenched and worked up. The results showed that hydroperoxide had been produced within 5 minutes ofthe addition of base.

Example 3 - Totally aqueous Next, a totally aqueous system was employed, again at a tempure of 40 C. 6.6 x 10-3 moles of N-tosyl-2-(4'-methoxyphenyl)ethyl hydrazine was suspended in 250 cm3 water and to this a solution of 5.3 g (0.06 moles) ofpotassium ethoxide dissolved in 150 cm3 water was added over a 10 minute period. The hydrazine only partially dissolved. Samples were removed at 5 minute intervals for TLC analysis and after 1 hour the reaction was quenched and worked up. Unrelated hydrazine was filtered off prior to the chloroform extraction The results indicated that the hydroperoxide had been formed in the system after just 5 minutes. The major finding of this experiment was that the reaction will proceed in water. Potassium ethoxide will exist almost entirely as the less poweiThi potassium hydroxide base in this system, although at 14 the pH will still be higher than that used in most bleaching processes.

Example 4 - Use of TEC Base as a Source of Alkaline Conditions A typical European aqueous alkaline fabric washing liquor can be produced using IEC base (total dosage 124.5 g), equating to 6.225 g IEC base per litre. Such a liquor would normally also contain a persalt and a bleach activator to provide the bleaching system. The pH of the liquor is approximatey 10 which can simulate any aqueous bleaching system with a moderately alkaline pH The composition of lEC base is: COMPONENT Parts Linear alkybenzene sulphonate (n=11.5) 8.0 Tallow alcohol ethoxylate (14 EO) 2.9 Sodium soap of mixed fatty acids 3.5 Ethylene divine tetraacetate tetrasodium salt 0.25 Sodium tripolyphosphate 43.7 Sodium silicate 7.5 Magnesium silicate 1.9 Sodium caitoxymethyl cellulose 1.25 Sodium sulphate 21.0 Water 9.75 Stilbene based optical brightener 0.25 A stodc solution of lEC base was prepared at this concentration and 500 cm ofthis were added to 6.6 x 103 moles of N-tosyl-2-(4'-chlorophenyl)ethyl hydrazine at 40 C. The mixture was stirred mechanically for 1 hour during which samples were removed for TLC analysis. After 1 hour the reaction was quenched and worked up as before. All analysis methods gave positive results for hydroperoxide with evidence of hydroperoxide after 5 minutes. The synthesis of benzyl hydroperoxide by reaction of N-tosylbenzylhydrazine was also shown to be possible within 5 minutes at 40 C in aqueous systems by reaction with lEC base. The HPLC peak of benzyl hydroperoxide was conciusively identified. This allows quantification of yield ofthe hydroperoxide formed. The oil formed was determined to contain 6% benzyl hydroperoxide. This represents a 50% conversion Example 5 - Bleaching by Hydroperoxides Both cumene and t-butyl hydroperoxides (purchased from Aldrich Chemical Co.) are effective in bleaching beetroot and carminic acid solutions at room temperature. A sample of benzyl hydroperoxide was also shown to be a bleach Bleaching using hydroperoxides formed by the hydroperoxydearnination route was investigated.

Canninic acid solutions at a concentration of 1x10tM were used because they are deeply colored at basic pHs. Patter a reaction time of 30 minutes the species formed by base catalysed (potassium ethoxide) hydroperoxydeamination of N-tosyl benny1 hydrazine in ethanolic solution was shown to give immediate bleaching of the carminic acid solution. After 24 hours at room temperature the solution was bleached so that the absorbance at 519nm had fallen from 0.72 to 0.15. No such alteration in absorbance was exhibited by the control.

Bleaching under laundry conditions was then investigated. N-tosyl benzyl hydrazine was treated with EC base (pH10) in aqueous solution Again the system was found to generate an effective bleach

Claims (9)

1. CLAIMS 1. A method of bleaching comprising of reaction of a hydroperoxide, preferably primary or secondary, ialatiF in that the hydroperoxide is formed, without the use of an oxidant other than atmospheric oxygen, in situ in a buffered alkaline aqueous liquor.
2. 2. A method according to claim 1 in which the hydroperoxide is formed by hydroperoxydeamination .
3. 3. A method according to claim 1 in which alkyl or aryl hydroperoxides, preferably aryl, are made from the corresponding N substituted N-Sulphonylhydrazines by air oxidation in basic aqueous conditions at a temperature in the range of from about 20"C to about 500C.
4. 4. A method according to claim 3 in which the corresponding N substituted N Sulphonyihydrazines is an N-tosyl hydrazire.
5. 5. A method according to claim 3 in which the pH lies in the range 7 to 12.
6. 6. A method of bleaching according to claim 1 in which the buffered alkaline aqueous liquor comprises a solution or dispersion of a detergent base.
7. 7. A method of bleaching a substrate comprising the reaction of a hydroperoxide, preferably primary or secondary, fbrmed m situ by alkaline catalysed hydroperoxydeamation of an N-tosylated hydrazine.
8. 8. A method according to claim 7 in which the substrate is laundry.
9. 9. A laundry detergent composition capable of being added to water to generate an alkaline wash liquor characterised in that the composition includes from 0.001 to 5 % of an N-tosyl hydrazine.