AU623961B2

AU623961B2 - Bleaching composition

Info

Publication number: AU623961B2
Application number: AU47271/89A
Authority: AU
Inventors: David Ellis Clarke
Original assignee: Unilever PLC
Current assignee: Unilever PLC
Priority date: 1988-12-28
Filing date: 1989-12-22
Publication date: 1992-05-28
Anticipated expiration: 2009-12-22
Also published as: AU624209B2; NO172354C; EP0376706A1; ES2067558T3; JP2562064B2; NO895261D0; IN170708B; AU4727289A; EP0376706B1; CA2006530C; IN171127B; CA2006531C; DE68921182T2; DE68921181D1; BR8906844A; ZA899843B; JPH0735520B2; NO895260L; NO172354B; CA2006530A1

Description

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AUSTRALIA

PATENTS ACT 1952 Form COMPLETE SPEC iCATION

(ORIGINAL)

FOR OFFICE USE Short Title: Int. Cl: Application Number: Lodged: S396 9 8a 8 8 88 *8u 88 8a 8 Complete Specification-Lodged: Accepted: Lapsed: Published: Priority: Related Art: TO BE COMPLETED BY APPLICANT 800 8 0 8 8 8 0 C Name of Applicants Address of Applicant: UNILEVER PLC UNILEVER HOUSE

BLACKFRIARS

LONDON EC4

ENGLAND

Actual Inventor: Address for Service: GRIFFITH HACK CO., 601 St. Kilda Road, Melbourne, Victoria 3004, Australia.

Complete Specification for the invention entitled: BLEACHING COMPOSITION.

The following statement is a full description of this invention including the best method of performing it known to me:- 1A.

C3290 BLEACHING COMPOSITION This invention relates to thickened liquid bleach compositions which may be suitable for sale and use as a domestic bleach. Pourable domestic bleach is frequently thickened by including one or more surfactants which, in the presence of electrolyte, act to thicken the solution rendering it more viscous than water. Thickening of a pourable domestic bleach helps the user to control 0 0 dispensing of the composition and retards drainage from 0 0 0 0.09 surfaces to which it is applied. This invention relates to such compositions which include surfactant and electrolyte to increase the viscosity. The compositions of the invention may be pourable or may be even more viscous so as not to be poured easily.

A domestic bleach needs to be adequately stable so that a substantial proportion of the bleaching agent I survives during storage between manufacture and use. Prior to this invention commercial liquid bleach products have frequently utilised hypochiorite as bleaching agent.

It is well known that hydrogen peroxide is unstable unless stabilising agents are present. These counteract decomposition catalysed by transition metal ions. Hydrogen peroxide gives better bleaching action if used under alkaline conditions. However, stabilisation of hydrogen peroxide under alkaline conditions is difficult and in consequence commercial solutions of 1,ydrogen peroxide 2 have generally been acidic for the sake of stability.

Certain phosphonates able to stabilise hydrogen peroxide in alkaline solution are disclosed in EP-B-9839 (Unilever).

The presence of electrolyte tends to cause decomposition of alkaline hydrogen peroxide solution. For instance, we have found that a 4% by weight solution of hydrogen peroxide, made alkaline to pH 10 and containing 0.25% of ethylene diamine tetramethylene phosphonic acid as stabiliser (which is not as effective as the phosphonates 10 in accordance with EP-B-9839) was found to retain 95% of its t hydrogen peroxide after two weeks storage at 37°C. By 9a t t contrast, 85% or less of the hydrogen peroxide was retained o if the solution also contained 1% by weight of sodium oa chloride, while only about 50% of the hydrogen peroxide was retained if the solution contained 10% by weight of sodium 99: chloride. Similar results were observed using sodium a 4 S.t, tripolyphosphate rather than sodium chloride as the added 1 9 electrolyte. Doubling the quantity of the phosphonate 9 C' stabiliser had little effect on the rate of decomposition.

I 20 Thus, any attempt to make a surfactant-thickened, alkaline domestic liquid bleach product using hydrogen 'peroxide as the bleaching agent would encounter the potential problem that the thickening of the solution would require the presence of some electrolyte but that this electrolyte would serve to accelerate decomposition of the peroxide.

We have now found, however, that it is possible to formulate an aqueous alkaline solution of hydrogen peroxide 3 which is thickened with surfactant and electrolyte yet does have sufficient stability to be useful as a commercial product.

According to the present invention there is provided a liquid bleaching composition comprising an aqueous alkaline solution containing hydrogen peroxide, a stabiliser therefor, electrolyte other than surfactant, and surfactant selected from: a) an alkyl ether sulphate of the formula: 0 o" o 10

R(OC

2

H

4 )n -OS0 3

M

O. 0 where R is an alkyl group containing 8 to 20 carbon atoms, 0 n has an average value in the range 0.5 to 12, preferably 1 9o9 to 6, and M is a solubilising cation.

00o b) a combination of a nonionic or amphoteric surfactant and an anionic surfactant which is either a C8 to C20 alkane 0 00 sulphonate or a C8 to C20 alcohol sulphate.

00 We have found that use of a surfactant as 0 4 specified above is advantageous in achieving thickening with c a fairly low electrolyte concentration. This may make it possible for the electrolyte to be provided by ions which are in the composition for other reasons, without deliberate addition of salt for the sole purpose of enhancing ionic strength. Apart from considerations of peroxide stability, a benefit of a low electrolyte concentration is a reduced tendency for the product to leave streaks on a surface which is cleaned with it.

When the surfactant is a combination, in accordance with the alternative above, a preferred 11_3~ 4 possibility for the nonionic/amphoteric surfactant is an amine oxide surfactant, preferably a trialkyl amine oxide with one long chain alkyl of 8 to 20 carbon atoms and two alkyl groups of 1 to 4 carbon atoms. Then, if primary alcohol sulphate is the anionic surfactant the weight ratio of amine oxide:alcohol sulphate is preferably in the range from 82:18 to 65:35, better 80:20 to 65:35, even better 80:20 to 70:30.

Alkane sulphonate is preferred over alcohol 0 "S"2 10 sulphate because the viscosity is less sensitive to changes 00 0 000 in the composition, so making it easier to produce an end 00 0 0 0 0 "0 product with repeatable viscosity. The weight ratio of 00 0 amine oxide to alkane sulphonate (when this is used) is 0000 preferably in the range from 80:20 to 50:50 or better 65:35, and preferably in the narrower range from 70:30 to 65:35.

o,9o One or more further surfactants may also be o o included, within the scope of this invention. The total Q 00 concentration of surfactant may lie in a range from 0.75 to 00 0 0 0 0 6% by weight based on the whole composition and may lie in 20 the narrower range from 0.75 to especially if the S'composition is pourable. Concentrations above 6% by weight might be used but are less preferred.

The electrolyte concentration in a composition of this invention may be such that the total amount of salts other than surfactant is not more than 7% by weight, better not more than 5% or The electrolyte level may be such as to give a concentration of electrolyte in the range 0.05 to 0.30 molar, preferably 0.1 to 0.2 molar. Once again higher concentrations may be used but are less preferred.

Stabiliser for the hydrogen peroxide may be a phosphonate sequestrant in accordance with EP-B-9839, which defines the phosphonate compounds as of the general formula: (P0 3

X

2

)CH

2 CH 2

(PO

3

X

2

N-CH

2

-CH

2

-(N-CH

2

-CH

2 )n-N (P0 3

X

2

)CH

2 CH 2 (P0 3

X

2

CH

2

(PO

3

X

2 10 wherein n 1-4; and X is H or a water-soluble cation selected from the group consisting of alkali metals, ammonium, substituted ammonium and alkaline earth metals.

Such a sequestering agent may be used in an amount from 0.01 to 1% by weight. This is approximately 1.5 x 10 4 to 15 2 x 10 2 molar.

These compounds are effective to counter decomposition catalysed by iron but are less effective against manganese. We have found that it may be possible to prevent contamination by traces of manganese by use of sufficiently pure raw materials) so that a separate S" stabiliser against manganese may not be required. However, if required a separate stabilising agent to counteract manganese may be a phosphate salt used in an amount from up to 4% by weight, preferably 1 to 3% (reckoned as anhydrous salt). Tetrasodium pyrophosphate may be used as such a salt.

An appropriate viscosity for a pourable Scomposition having the appearance of a thick liquid is a dynamic viscosity in the range from 40 to 250 centipoise (0.05 to 0.25 Pa.sec), preferably about 100 centipoise (0.1 Pa.sec). More viscous liquids for example with viscosity in the range from 250 to 1000 centipoise or more are also within the scope of the invention.

Since the compositions of this invention are i 35 generally aqueous, they will usually have specific gravity close to unity. Consequently values of kinematic 6 viscosities (in stokes) will be numerically approximately the same as values of dynamic viscosity (in poise).

Dynamic viscosities expressed in Pascal.sec will be approximately 1000 times kinetic viscosities expressed in m 2 .sec 1 The pH of the solution is preferably in the range from 8.0 to 10.5, better 8.5 to 9.8 or 10.0. With a phosphonate stabiliser it is further preferred that the pH is in the narrower range from 9.2 to 9.8. A buffer may be included to maintain pH at the desired value, but this may not be necessary. A phosphate, if present, will give a buffering action. Another compound which may be used for this purpose is borax.

The concentration of hydrogen peroxide in 15 compositions of this invention, reckoned as pure H 2 0 2 desirably lies in the range from 1 to 15% by weight preferably 2 to 10% by weight.

Example 1 A range of formulations were prepared, all 20 containing: Hydrogen peroxide 5.0% reckoned as anhydrous Tetrasodium pyrophosphate 3.0% (approx 1.8% reckoned decahydrate as anhydrous) Phosphonate stabiliser 0.3% according to EP 9839 Perfume 0.1% Sodium hydroxide to pH 9.6 Thickening system variable Water balance to 100% The thickening systems used various constituents and varied both in the properties and total amounts of materials employed.

The thickening systems contained tallow R dimethylamine oxide (AO) together with sodium lauryl sulphate (SLS), or sodium alkane sulphonate (SAS), which r 7- 7 was a secondary alkane sulphonate derived from an n-alkane mixture which is principally

C

13 to C 18 Viscosities of the formulations were measured using a Ubbelohde capillary viscometer. The results obtained are shown in the accompanying Figures.

Figure 1 shows variation in viscosity with the proportion of SLS in an AO/SLS mixture, while the total amount of AO plus SLS is varied from 1.1% to 1.9% by weight of the composition.

Figure 2 shows variation in viscosity for AO/SAS mixtures while the total of AO plus SAS is varied from 1.2% to 2.6% of the composition. It can be seen that the viscosity maxima are broader peaks, while the maximum viscosity is less sensitive to variation in the total 15 amount of AO plus SAS. For instance in Figure 1 the S*concentration of surfactant to give a viscosity of 100cS is and an increase from this of up to would double the viscosity to 200cS. In Figure 2 1.4% total surfactant gives a viscosity of 100cS. Increasing by 0.2% t i 20 increases the viscosity to 150cS and a larger increase, to is required to achieve 200cS.

Example 2 A number of formulations were prepared using as surfactant a linear alkyl ether sulphate of general formula:

R(OC

2

H

4 )nOSO 3 Na where the alkyl group R was C 12 and C 13 linear alkyl groups, and n had an average value of 3, and including a phosphonate stabiliser according to EP 9838. Peroxide stability was monitored, as in Example 1. Viscosities were determined using a Haake RV2 roto-viscometer at a shear rate of 21sec-1 which is appropriate for determining viscosities of pourable domestic bleach products. The formulations were as follows: -'1 8 by weight Constituent Hydrogen peroxide (reckoned as anhydrous) Alkyl ether sulphate Sodium chloride Perfume Sodium hydroxide to give: variable 0.8 0.8 pH 9.6 pH 9.6 Water balance to 100%

H

2 0 2 remaining after 5 weeks at 37 0

C

80% 79% C ?r The amounts of alkyl ether sulphate and sodium chloride in various formulation, together with the results observed, are set out in the following Table.

Alkyl ether sulphate Sodium chloride Phosphate stabiliser according to EP 9839

H

2 0 2 remaining after weeks at 37 0

C

Viscosity (cP) 3% 5.5% 1.25% 0.15% 0.15% 0.15% 0.15% 75% 15 72% 200 71% 600 79% 100

Claims

44-- THE CLAIMS DEFINING THE INVENTION ARE AS FOLLOWS: 1. A liquid bleaching composition comprising an aqueous alkaline solution containing 1-15% by weight hydrogen peroxide, 0.01-4%wt of a stabiliser for hydrogen peroxide selected from phosphate, phosphonate, and mixtures thereof, 0.05-0.30 Molar electrolyte other than surfactant and 0.75-6% by weight of a combination of a non-ionic or amphoteric surfactant and an anionic surfactant which is either a C8-C20 alkane sulphonate or a C8-C20 alcohol sulphonate. 2. A composition according to claim 1 wherein the surfactant is a combination of a trialkyl amine oxide having one C s to C 20 alkyl group and two C, to C 4 alkyl groups and (ii) a said anionic surfactant. 0:00 15 3. A composition according to claim 1 or claim 2 °wherein the amount of electrolyte in solution is such that the total quantity of salts other than surfactant in the S" composition does not exceed 5% by weight based on the whole composition. o 4. A composition according to any one of the o0 preceding claims wherein the amount of surfactant present is in the range from 0.75 to 3% by weight based on the whole composition. A composition according to any one of claims 1 to 4 wherein the stabiliser is a compound of the formula: PO, X, )CHO CH (PO, X N-CH 2 -CH -(N-CH 2 -CH2 )n-N2 (PO X 2 )CH( CH (PO 3 X 2 CH 2 (PO 3 X wherein n 1-4; and X is H or a water-soluble cation selected from the group consisting of alkali metals, ammonium, substituted ammonium and alkaline earth metals. 6. A composition according to any one of the preceding claims having a pH in the range from 8.5 to DATED THIS 23RD DAY OF JANUARY 1992 UNILEVER PLC By its Patent Attorneys: GRIFFITH HACK CO S 10 Fellows Institute of Patent Attorneys of Australia. r C I 0 0 00 0 e C C