WO1996030486A1

WO1996030486A1 - Alkaline isotropic liquid detergent with peroxide

Info

Publication number: WO1996030486A1
Application number: PCT/GB1996/000655
Authority: WO
Inventors: Michael John Day
Original assignee: Warwick International Group Ltd
Current assignee: Warwick International Group Ltd
Priority date: 1995-03-24
Filing date: 1996-03-18
Publication date: 1996-10-03
Anticipated expiration: 1997-09-24
Also published as: AU5115796A

Abstract

Non-ionic rich concentrated aqueous alkaline isotropic liquid detergent composition, suitable for use as a laundry detergent and comprising a mixture of non-ionic surfactant and anionic surfactant, together with a hydrotrope and hydrogen peroxide. The composition additionally contains citrate and the total surfactant level is at least 30 %, preferably 35 %. The use of citrate in the composition is found to give reduced downward pH drift compared to the corresponding non-citrate formulations. Peroxide stability in both types of formulation is similar.

Description

ALKALINE ISOTROPIC LIQUID DETERGENT WITH PEROXIDE

This invention relates to aqueous alkaline isotropic liquid detergent compositions particularly to concentrated compositions containing hydrogen peroxide and a surfactant system including a major part of a nonionic surfactant and a minor part of an anionic surfactant

Aqueous alkaline isotropic liquids containing surfactant and peroxide suffer from the problem of the pH drifting towards the acid which can result in a loss of detergency and variable washing characteristics depending on the age and storage history of the product This is not acceptable in a coommercial product The prior art contains many attempts to obtain analkaline isotropicheavy duty liquid detergent with peroxide. All fail to provide the required combination of physical stability, and storage chararteristics. In particular they lose peroxide to an unacceptable degree during storage, or they change their pH to an unacceptably high degree. Often they fail on each of these criteria.

Among such prior art compositions there may be mentioned:

WO93/14183 which 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. The examples in this patent specification use a level of peroxide of only 0.18% and a low pH of 7.1. Al examples are rich in anionic surfactant Some contain low levels (0.4%) of sodium citrate, along with the same level of citric acid.

US 4 470 919 which describes a liquid detergent composition containing hydrogen peroxide, surfactant fatty add and a calcium salt Preferred anionic surfactants include alkylbenzene sulphenates, alkyl sulphates and alkyl ether sulphates. The pH of the composition must be less than 9. There are both nonionic rich and anionic rich examples but neither contain citrate.

EP 0 037 184, which describes an aqueous detergent composition containing peroxide and an alcohol stabiliser system Formulations built with sodium citrate are all anionic rich. EP 0076 166 describes a non-concentrated aqueous detergent composition containing peroxide and an alcohol stabiliser system The examples disclose the use of 6% anionic surfactant (linear alkylbenzene sulphαnate), 4% nonionic surfactant (primary alcohol ethoxylate) and 6% of a sodium xvlene sulphonate (SXS) hydrotrope in addition to peroxide and isopropyl alcohol Some of these anionic rich examples contain a builder which is either potassium tetrapyrophosphate or sodium citrate. Nonionic rich examples do not contain sodium citrate as they are stated to contain no builder. Citrate in the form of sodium citrate is often used as a builder in liquid detergent formulations containing relatively high levels of anionic surfactant There is no prior art teaching of such a builder being used for nonionic rich formulations which also contain hydrogen peroxide.

WO 92/02607 has examples which contain H₂O₂ in a surfactant system which is nonionic rich and further contains an alkyl polyglucoside surfactant The total surfactant level is less than 30% in all cases. Citric acid is included as sodium or potassium citrate in an amount of 0.5-0.7%. Surprisingly we have found that use of sodium citrate reduces the problem of pH drift which occurs when peroxide is incorporated into a nonionic rich concentrated liquid detergent formulation.

A concentrated peroxide liquid is desirable because of the consequent reduction in transport and storage costs. The problem of how to formulate a concentrated liquid with peroxide has eluded those skilled in the art for many years. Inclusion of peroxide can destabilise an otherwise stable liquid formulations and there is therefore no guarantee of success if one simply takes a known concentrated liquid detergent formulations and adds peroxide. We have found a range of formulations which give surprisingly good stability combined with low odour and which can be used neat for pretreatment of soiled clothing. According to the present invention there is provided a nonionic rich concentrated aqueous alkaline isotropic liquid detergent composition with a pH greater than 7.5 comprising a mixture of nonionic surfactant and amionic aurfactant to gether with a suitable hydrotrope and at least 0.2% by weight of hydrogen peroxide characterised in that the composition comprises citrate and at least 30% preferably at least 35%, total surfactant

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 and avoids the problem of pressure build-up in the container or the need to provide the container with a vented cap.

The total surfactant level lies in the range 30 to 60%by weight. The anionic surfactant is preferably a linear alkylbenzene sulphonic acid (LAS) or alternatively lauryl ether sulphate (LES). Preferably the total surfactant level is 35% or more. 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.

When the composition has LAS as the anionic co-surfactant from 5 to 25% of a hydrotrope 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, may be included. When the composition has LES as the anionic co-surfactant a hydrotrope selected from the group comprising hexylene glycol and butyl carbitol, may be included

The pH of the composition may lie in the range 7.5 to 12, preferably around 9.5. 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%.

Preferred nonionic surfactants are alcohol ethoxylates such as C_8-24, preferably C_10-16, alcohols which have been ethoxylated using 1 to 20 moles, preferably 3 to 12 moles of ethylene oxide per mole of alcohol; alkylphenol ethoxylates; alkyl polyglycosides, particularly alkyl polyghicosides; amine oxides and mixtures thereof The composition may additionally contain other surfactants chosen from amphoteric, zwitterionic and cationic surfactants.

The composition may also comprise minor components conventionally found in a heavy duty liquid detergent composition. These include, optical brighteners, preservatives, thickeners, colorants, builders, anti-redeposition agents or anti-dye transfer agents, such as polyvinylpyrrolidone (PVP) and other conventional additives.

The composition 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: Example 1 and Comparative example A

In these examples the nonionic surfactant used was SYNPERONIC A7 ex Cargo Fleet. It is a 90% solution C_13-15 primary alcohol ethoxylated with 7 moles of ethylene oxide. The anionic surfactant was MARLON AS3 a C_10-13 linear alkylbenzene sulphonic acid ex Huls. The pH was ca. 9.4. A sequestrant system of Dequest 2066 with or without DPA was used. AH formulations contained sodium hydroxide to adjust the final pH of the composition and also to neutralise the LAS in situ. Formulations also included PVP as an anti-redeposition and anti-dye transfer agent and TINOPAL CBS-X, a fluorescer ex Ciba Geigy. The nonionic/LAS ratio used was 70/30 (w/w). The total surfactant and hydrotrope levels were 35.0% (w/w) and 12.5% (w/w) respectively and the initial level of hydrogen peroxide was 5.0% (w/w).

Peroxide and pH stability data is given for accelerated storage at 37°C and 45°C of Formulation 1 which contains citrate (3.0% w/w) and for comparative formulation A which is the corresponding formulation without any citrate.

Formulations were manufactured using the following process. To Water at 25°C was added Sodium hydroxide, hydrotrope(s), optional citrate, surfactants, sequestrants), PVP and fluorescer before addition of the peroxide. The liquid was mixed and the pH adjusted with sodium hydroxide. For processing reasons ingredients are preferably added as liquids. The composition of the formulations in % by weight of the active ingredient, or % solids is given in Table 1. All ingredient levels are quoted on 100% basis. Minors includes the sequestrants (Dequest 2066 and DPA or just Dequest 2066 in the case of formulation 1), anti-redeposition agent (PVP) and TINOPAL CBS-X.

The %H₂O₂ was measured by permanganate titration. Measurements were made initially and then after storage for the specified periods of time at the specified constant temperature. Results are given in Table 3.

At both 37°C and 45°C the pH of the formulation 1 containing citrate decreases more slowly than that of the corresponding non-citrate comparative formulation A . Peroxide stability in both formulations is similar at both temperatures, thus showing that the stability is not adversely affected by the maintenance of a more alkaline pH.

Example 2 and Comparative Example B

Example 2 is a repeat of example 1 with the inclusion of the second (DPA) sequestrant. Comparative Example B has the same composition as Comparative Example A Results for pH stability and peroxide stability are given in Tables 4 and 5.

Example 3 and Comparative Example C

Examples 2 and B were repeated with the substitution of hexylene glycol for the propylene glycol hydrotrope, pH and %H₂O₂ remaining data is given in Tables 4 and 5.

Claims

1. A nonionic rich concentrated aqueous alkaline isotropic liquid detergent composition with a pH greater than 7.5 comprising a mixture of nonionic surfactant and anionic surfactant together with from 5 to 25% of a suitable hydrotrope and at least 0.2% by weight of hydrogen peroxide characterised in that the composition comprises at least 30% total surfactant and a citrate.

2. An aqueous alkaline isotropic liquid detergent formulation according to claim 1 wherein the citrate is 0.5 to 5 % by weight sodium citrate.

3. An aqueous alkaline isotropic liquid detergent formulation according to claim 1 or 2 wherein the composition is substantially free from C_1-4 monohydric alcohols,

4. A nonionic rich aqueous alkaline isotropic liquid detergent formulation according to any one of claims 1 to 3 wherein the anionic surfactant is a linear alkylbenzene sulphonic acid (LAS).

5. An aqueous alkaline isotropic liquid detergent formulation according to any preceding claim wherein the hydrotrope is selected from a first group comprising propane-1,2-diol, 2-methyl- 2,4-pentanediol, and 2-(2-butoxyethoxy) ethanol

6. An aqueous alkaline isotropic liquid detergent formulation according to any preceding claim wherein the hydrogen peroxide is present in an amount by weight in the range 0.2 to 15% preferably 0.2 to 8% and most preferably around 5%.

7. An aqueous alkaline isotropic liquid detergent formulation according to any preceding claim wherein the total surfactant level is at least 35%.