WO1996030484A1

WO1996030484A1 - Alkaline isotropic liquid detergent with peroxide

Info

Publication number: WO1996030484A1
Application number: PCT/GB1996/000643
Authority: WO
Inventors: Michael John Day; Carey James Walsh
Original assignee: Warwick International Group Limited
Priority date: 1995-03-24
Filing date: 1996-03-18
Publication date: 1996-10-03
Also published as: GB9506093D0; AU5114796A

Abstract

Aqueous alkaline isotropic liquid detergent composition comprising a mixture of nonionic and anionic surfactants and hydrgen peroxide. The composition is suitable for use as a laundry detergent and is characterised in that it contains a mixture of two hydrotropes, one of which is an aryl sulphonate hydrotrope. The use of the specific combination of two hydrotropes in these compositions results in reduced pH drift without compromising peroxide stability. This feature of reduced pH drift is unexpected since when used individually in a complete formulation, the hydrotropes promote pH drift towards the acid.

Description

AT.KA TNE ISOTROPIC LIQUID DETERGENT WITH PEROXIDE

This invention relates to aqueous alkaline isotropic liquid detergent compositions particularly to compositions containing hydrogen peroxide and a surfactant system including an anionic surfactant.

A problem with formulating an aqueous isotropic liquid containing surfactant and peroxide is that the pH of the composition tends to drift towards the acid range with time. This loss of alkalinity reduces the detergency and bleaching of the composition. It would therefore be advantageous if such isotropic liquids could be stabilised at an alkaline pH.

W093/14183 describes liquid detergent compositions containing anionic and/or nonionic surfactant, oxygen bleach and a metal sequestering agent to prevent discoloration with time. The composition may also contain a hydrotrope. Useful hydrotropes are stated to be alcohols such as ethyl alcohol and propylene glycol at a level of 0 to 15%; sodium and potassium toluene, xylene or cumene sulphonate at levels from 0 to 10%; and urea at a level of 0 to 10%. Example 1 uses a mixture of amπonium xylene sulphonate (4%) and ethanol (5.5%). However the level of peroxide is only 0.18% and the pH is stated to be 7.1. The same pH is mentioned for the other examples in this patent specification. All examples are rich in anionic surfactant.

WO 92/02607 describes an aqueous liquid bleaching composition with good storage characteristics. It contains a surfactant system comprising a mixture of soap, alkyl polyglucoside and sodium fatty - 9 -

alkyl sulphate with a major part of C, fatty substituent. The formulations also include ethanol, propane-1,2-diol (propylene glycol) and diethylenetriaminepentarrtethylene phosphonate. The pH of the formulations is about 7.

US 4 507 219 describes heavy duty liquid detergents in the form of isotropic liquids. A chlorine bleach can be added and the compositions are stated to be compatible with the bleach. A preferred solvent system is said to be a mixture of ethanol, a polyol and water. Propylene glycol is the preferred polyol. It is stated that the composition may also contain hydrotropes. There is no suggestion to use an oxygen bleach.

US 4 470 919 describes a liquid detergent composition containing hydrogen peroxide, surfactant, fatty acid and a calcium salt. Preferred anionic surfactants include alkylbenzene sulphonates, alkyl sulphates and alkyl ether sulphates. The pH of the composition must be less than 9. The compositions may contain a phase regulator such as ethanol, n-propanol, isopropanol, butanol, propane-1,2-diol, propane-1,3-diol, n-hexanol; 2-methyl,2,4- pentanediol, monomethyl-, ethyl and propyl and monobutyl- ethers and diethylene glycol. The composition may also include known detergent hydrotropes e.g. sodium, potassium and ammonium salts of xylene, toluene, ethyl benzene and cumene sulphonic acids. Examples use only ethanol and propane-1,2-diol.

EP 0 037 184 describes an aqueous detergent composition containing peroxide and an alcohol stabiliser system. Built anionic rich and unbuilt nonionic rich compositions are disclosed. Ethanol is always used, along with a sodium xylene sulphonate (SXS) hydrotrope for these compositions. In related patent specification EP 0 076 166 isopropanol is stated to be preferred over ethanol because of its higher flashpoint. The examples disclose the use of 6% anionic surfactant (linear alkylbenzene sulphonate) , 4% nonionic surfactant (primary alcohol ethαxylate) and 6% of the sulphonate hydrotrope ELTESOL SX30 (SXS) in addition to the peroxide and isopropanol. This example was not adjusted to an alkaline pH.

We have discovered that certain hydrotropes when used in combination give a surprising degree of pH stability to a fully formulated aqueous alkaline isotropic liquid detergent formulation containing hydrogen peroxide.

According to the present invention there is provided an aqueous alkaline isotropic liquid detergent composition comprising a mixture of nonionic and anionic surfactants and at least 0.2% by weight hydrogen peroxide characterised in that it also comprises a mixture of two hydrotropes selected to reduce the downward pH drift of the composition with time and wherein one of the hydrotropes is an aryl, preferably alkylaryl sulphonate.

The surfactant part of the composition is preferably nonionic rich and contains an anionic co-surfactant. In this specification the term nonionic rich means that the proportion of nonionic surfactant is greater than 50% by weight of the total of all anionic and nonionic surfactants in the composition. Anionic rich means that the amount by weight of nonionic surfactant makes up less than or equal to 50% of the total of all anionic and nonionic surfactants. The anionic co-surfactant may be a linear alkylbenzene sulphonic acid (LAS) . A preferred anionic co-surfactant is lauryl ether sulphate (LES) . The total amount of surfactant in the composition will be in the range 20 to 70% by weight, preferably 30 to 50%. The nonionic surfactant preferably forms a major part of the total amount of surfactant. Preferred nonionic surfactants are alcohol ethoxylates such as C_β-24, preferably _₀._16l alcohols which have been ethoxylated using l to 20 moles, preferably 3 to 12 moles of ethylene oxide per irole of .alcohol; alk lphenol ethoxylates; alkyl polyglycosides, particularly alkyl polyglucosides,- amine oxides and mixtures thereof. The composition may additionally contain other surfactants chosen from amphoteric, zwitterionic and cationic surfactants.

The first hydrotrope is preferably an alkylaryl sulphonate selected from the group comprising ammonium, sodium and potassium salts of toluene, xylene and cumene sulphonate at levels up to about 20%. SXS is a preferred first hydrotrope.

When the composition has LAS as the co-surfactant the second hydrotrope is selected from the group comprising: propane-1,2-diol also known as propylene glycol; 2-methyl-2,4-pentanediol also known as hexylene glycol; and 2- (2-butoxyethoxy) ethanol also known as butyl carbitol or di(ethylene glycol) butyl ether. Preferably propylene glycol is used. When the composition has LES as the co- surfactant the second hydrotrope is selected from the group comprising hexylene glycol and butyl carbitol, preferably hexylene glycol. The second hydrotrope is preferably present at a level of from 5% to 25% by weight.

Advantageously the composition is substantially free from ethanol or other lower C_1-4 monohydric alcohols as this reduces the danger of explosion from the mixture of low flashpoint alcohol and peroxide. It also reduces the amount of odour due to evaporation of volatile material.

There are many problems to overcome before a hydrogen peroxide aqueous detergent is sufficiently stable to be commercially viable. Because detergency is best under alkaline conditions loss of alkalinity means that the composition is no longer very efficient as a detergent.

For concentrated liquid detergents with more than about 20% total surfactant it is conventional to employ a hydrotrope to ensure that the liquid has a suitable viscosity. Surprisingly, we have found that the use of specific combination of two hydrotropes which used individually in a complete formulation gave pH drift towards the acid, results in slower pH drift. The choice of the second hydrotrope depends on the surfactant system used. The person skilled in the art of liquid detergent formulations will know, or can readily determine by simple experimentation, which hydrotropes are suitable for a given surfactant system. The ratio of first to second hydrotrope may be from 4:1 to 1:4, preferably 3:1 to 1:3 and most preferably about 1:1 by weight.

The pH of the composition will normally be alkaline, preferably 9 to 11, most preferably around 9.5. The pH after storage at 25°C for 12 weeks should not have dropped more than 1.5 pH units, preferably not more than 1 pH unit, and should not be acid.

The hydrogen peroxide is preferably present in an amount by weight in the range 0.2 to 15% more preferably 0.2 to 8% and most preferably around 5%. The composition may also comprise minor components conventionally found in a heavy duty liquid detergent composition. These include, perfume, enzymes, optical brighteners, preservatives, thickeners, colorants, builders, anti-redeposition agents or anti-dye transfer agents, such as polyvinylpyrrolidone (PVP) and other conventional additives.

The coπposition preferably contains sequestrants. Preferred sequestrants are sodium diethylenetriaminepentamethylene- phosphonate, sold as Dequest 2066 by Monsanto, 2,2' -dipyridylamine (DPA) and 1,2' -diaminocyclohexyl tetrakis methylene phosphonic acid. Other sequestering agents for iron, cobalt, copper and manganese ions may be used instead of or in addition to these preferred sequestrants.

The invention will now be further described with reference to the following non-limiting examples:

In the examples the nonionic surfactant used was SYNPERONIC A7 a 90% solution C_13-1S 7EO primary alcohol ethoxylate ex Cargo Fleet. The anionic surfactant was either MARLON AS3 a C_10-13 linear alkylbenzene sulphonic acid ex Huls, or NEOPON LOS 3N 70 a sodium lauryl ether sulphate ex Baxenden chemicals. The initial %H-0₂ was 5.0 and the initial pH was ca. 9.4. A mixed sequestrant system of Dequest 2066 and DPA was used. All formulations contain sodium hydroxide to adjust the final pH of the composition and also to neutralise the LAS in situ where it is used. Formulations also included PVP as an anti-redeposition and anti-dye transfer agent and TINOPAL CBS-X, a fluorescer ex Ciba Geigy.

All the formulations were made using the same basic process. To water at 25°C is added sodium hydroxide, hydrotrope(s) , surfactants, sequestrant(s) , PVP and fluorescer before addition of the peroxide. The liquid is mixed and the pH is adjusted with sequestered sodium hydroxide. For processing reasons ingredients are preferably added as liquids. Solid ingredients such as SXS could be added directly in order to reduce the water contribution from an aqueous solution additive, however, this would only be preferred for very high levels of surfactant. The coπposition of examples in % by weight of the active ingredient, or % solids is given in Table 1. Minors includes the sequestrants (Dequest 2066 and DPA) , PVP and TINOPAL CBS-X.

Table 1 - Composition of Examples

Component (wt.%) A B 1 D c 2 3 4 E 5

Nonionic 24.5 24.5 24.5 31.5 31.5 31.5 31.5 31.5 31.5 30.0

Anionic 10.5 10.5 10.5 13.5 13.5 13.5 13.5 13.5 13.5 10.0

Sodium 1.3 1.3 1.3 1.7 1.7 1.7 1.7 1.7 0.2 0.2 hydroxide

SXS - 12.5 S.25 - 12.5 6.25 3.1 9.4 - 9.0

Propylene 12.5 6.25 12.5 6.25 9.4 3.1 ~ ~ glycol ^" ^"

Hexylene - — ID 9.0 glycol ^" ^" ^' ^' ^" ^"

H 5

Minors 1.16

Water to 100 Comparar.-vp examples A and B and Example 1

These examples each contained 35% total surfactant and were formulated with a 70/30 ratio of nonionic to anionic. The anionic surfactant was LAS. In comparative example A the hydrotrope was propylene glycol alone, in comparative example B the hydrotrope was SXS alone and in exanple 1 the hydrotrope system was a 50/50 mixture, by weight, of propylene glycol and SXS. The % H,0₂ was measured by permanganate titration initially and after storage for specified periods of time at constant temperature. Results are given in Table 2 for extended storage at 25°C and storage at 37°C.

Table 2 - pH/f-H.Q, loss

Eg(°C) Initial 1 week 2 weeks 4 weeks 8 weeks 12 weeks

A(25) 9.4/0.0 9.5/2.2 9.3/2.7 8 .3 /3. 6 7.4/9.4 1 .2/10. 6

B(25) 9.4/0.0 9.5/1.8 9.4/3.2 9 . 0/5. 8 7.8/10.7 1 . 6/16. 9

1(25) 9.5/0.0 9.4/0.3 9.4/- 9.4/2.1 9.2/8.1 8 . 8/8. 8

A(37) 9.4/0.0 9.0/7.4 1 .1/8.9 6.8/10.1

B(37) 9.4/0.0 9.3/5.8 8 .2/9. 1 6.8/15.5

1(37) 9.5/0.0 9.3/2.3 9.1/- 8.9/11.0

It can be seen that for exanple 1 the pH remains more alkaline for longer and the peroxide loss is slower, thus showing that use of the mixed hydrotrope system gives pH stability without compromising peroxide stability. Comparative examples C and D and Examples 2. 3 and 4 These are essentially a repeat of examples 1, A and B but with different total levels of surfactant and different ratios of the two hydrotropes. The same surfactants were used. Storage data for pH and %H-0₂ lost is given in Table 3.

Table 3 - pH/3-tf₂0₂ loss

Eg(°C) Initial l week 2 weeks 4 weeks 8 weeks 12 weeks

C(25) 9.4/0.0 9.1/1.2 8.8/1.2 8.5/5.2 8.1/9.1 7.6/13.9

D(25) 9.5/0.0 9.0/0.0 8.6/- 7.9/4.7 7.4/7.8 7.1/12.1

2(25) 9.6/0.0 9.6/1.4 9.5/5.0 9.3/3.4 9.2/9.5 9.0/20.3

3(25) 9.6/0.0 9.7/2.2 9.5/3.1 9.5/2.9 9.3/9.8 9.0/11.4

4(25) 9.5/0.0 9.5/3.2 9.5/4.0 9.5/6.4 9.4/15.0 9.2/21.5

C(37) 9.4/0.0 8.4/2.4 7.5/8.5 7.2/10.7

D(37) 9.5/0.0 8.2/4.5 7.5/7.2 6.6/8.2

2(37) 9.6/0.0 9 .2/3. 6 9.0/7.3 7.6/11.7

3(37) 9.6/0.0 9 .5/6.1 9 .2/6.9 1 .5/10. 6

4(37) 9.5/0.0 9 .5/6.4 9 . 1/10. 4 1 . 6/15. 6

Comparative example E and Example 5

Comparative example E uses the single hydrotrope hexylene glycol with a 70/30 ratio of nonionic to anionic in a composition comprising 45% total surfactant. The anionic surfactant was LES. Hexylene glycol was used instead of propylene glycol with this anionic surfactant. Exanple 5 contained 40% total surfactant and was formulated with a 75/25 ratio of nonionic to LES anionic. In exanple 5 the hydrotrope system was a 50/50 mixture, by weight, of hexylene glycol and SXS. pH and %H₂0₂ loss data for 25°C and 37°C are given in Table 4. Table 4 - pH/ %H₂0₂ loss

Eg(°C) Initial 1 week 2 weeks 4 weeks 8 weeks 12 weeks

E(25) 9.4/0.0 8.9/0.0 8.7/1.0 8.4/0.0 8.2/5.5 7.9/7.9

5(25) 9.5/0.0 9.5/4.1 9 .5/1 . 6 9.4/4.3 9.4/7.7 9.2/12.0

E(37) 9.4/0.0 8.4/0.6^" 8 . 0/1 . 6 7.6/2.0

5(37) 9.5/0.0 9.4/4.7 9 .2/5.3 9.0/8.4

In both the nonionic/LAS and nonionic/LES formulations, peroxide stability in the mixed hydrotrope formulations at a pH of around 9.5 is coπparable to that in single hydrotrope less alkaline formulations. Some of the single hydrotrope formulations exhibit better peroxide retention as evidenced by lower %H-0₂ loss data, but this is always accompanied by an undesirable drop in the pH. Use of the mixed hydrotrope system again gives pH stability without compromising peroxide stability.

Claims

________

1. An aqueous alkaline isotropic liquid detergent coπposition comprising a mixture of nonionic and anionic surfactants and at least 0.2% by weight of hydrogen peroxide characterised in that it also comprises a mixture of an aryl, preferably alkylaryl, sulphonate hydrotrope and a second hydrotrope selected to reduce the downward pH drift of the composition with time.

2. An aqueous alkaline isotropic liquid detergent formulation according to claim 1 wherein the total surfactant level is greater than 25% and comprises a major part of nonionic surfactant.

3. An aqueous alkaline isotropic liquid detergent formulation according to claim l or 2 wherein the first hydrotrope is selected from the group comprising ammonium, sodium and potassium salts of toluene, xylene and cumene sulphonate at levels up to 20%.

4. An aqueous alkaline isotropic liquid detergent formulation according to any preceding claim wherein the composition is nonionic rich and contains an anionic co-surfactant, which is a linear alkylbenzene sulphonic acid (LAS) .

5. An aqueous alkaline isotropic liquid detergent formulation according to any preceding claim wherein the composition is nonionic rich and contains an anionic co-surfactant, which is lauryl ether sulphate (LES) . An aqueous alkaline isotropic liquid detergent formulation according to claim 4 wherein the second hydrotrope is selected from the group comprising propane-1,2-diol, 2- methyl-2,4-pentanediol, and 2- (2-butoxyethoxy)ethanol.

An aqueous alkaline isotropic liquid detergent formulation according to claim 5 wherein the second hydrotrope is selected from the group comprising 2-methyl-2,4-pentanediol, and 2- (2-butoxyethoxy)ethanol.

An aqueous alkaline isotropic liquid detergent formulation according to any preceding claim wherein the coπposition is substantially free from ,., monohydric alcohols.