GB2193505A - Detergent compositions - Google Patents

Abstract

A liquid detergent composition for washing vehicles comprises:- a) from 5 to 30% by weight of a nonionic surfactant; b) from 1 to 15% by weight of caustic material; c) from 1 to 15% by weight of organic solvent; d) from 1 to 10% by weight of nitrilotriacetic acid or a salt thereof; and e) from 0.1 to 2.5% by weight of thickening agent; the balance being water; the composition being thixotropic when diluted with water to a concentration at which it has a pH of 12 or less.

Description

SPECIFICATION Detergent compositions The present invention relates to thixotropic detergent compositions, their manufacture and their use in cleaning, particularly in the cleaning of vehicles such as automobiles.

In the cleansing of hard surfaces, the cleaning of vehicle exteriors is recognised as being particularly difficult. The difficulty arises from a thin layer of soiling which adheres tenaciously to the outer surface of vehicles; in particular soiling such as petrol stains, oil and diesel fuel presents problems. This strongly'absorbed layer is known as traffic film.

Industrial cleaning of vehicles is generally carried out using a detergent composition, aided by use of rotating brushes or high-pressure sprays.

Alkaline products containing a sequestrant, surfactant and a particulate material have been used for this purpose but it has been found that their frequent use can result in damage to paintwork.

Another major drawback of such products is the formation of thin draining films on application to the vehicle surface to be cleaned, thus providing inadequate contact time and insufficient detergency to emulsify the high levels of soiling encountered. To overcome this disadvantage, it has been proposed to employ thixotropic detergent compositions, as described in UK Patent Specification GB 2 134 132 A, which have an increased detergent residence time on nonhorizontal surfaces and sufficient detergency to emulsify gross soiling. However, these thixotropic compositions have been found to have a problem of instability. In part, it is thought that the instability may arise because the compositions require a hydrotrope to ensure solubility of all constitutents. The hydrotrope disrupts structuring mechanisms within the composition and so detracts from the thixotropic properties.A further problem arises in that the compositions are only effective down to aqueous dilutions of about 15%, which is disadvantageous in terms of practicality and cost effectiveness.

We have now found that the instability and dilution problems referred to above can be overcome by providing a liquid detergent composition comprising: a) from 5 to 30% by weight of a nonionic surfactant system; b) from 1 to 15% by weight of caustic material; c) from 1 to 15% by weight of organic solvent; d) from 1 to 10% by weight of at least one sequestering agent selected from nitrilotriacetic acid and salts thereof; and e) from 0.1 to 2.5% by weight of thickening agent; the balance being water; said composition being thixotropic when diluted with water to a predetermined concentration at which it has a pH of 11 or less.

Patent Specification GB 965,215 describes liquid detergent compsitions for machine warewashing, e.g. bottle washing, which comprise a nonionic surfactant system in- combination with a high level of caustic material and a polymer thickening agent. Optionally, sequestrant such as EDTA is also included. However, the compositions described there are too aggressively alkaline and do not have the necessary thixotropic properties to be in any way suitable as vehicle cleaning agents.

Specification US 3,591,508 describes heavy duty liquid detergent compositions containing a nonionic active, alkaline material, nitrilotriacetic acid (or acetate) sequestrant and sodium carboxymethylcellulose anti-redeposition agent. The molecular weight of the latter agent is unspecified but it will be clear to those skilled in the art that such agents would be used at molecular weights ow enough to have a negligible effect on viscosity (high viscosity being a common problem in heavy duty liquids). Indeed, a small amount of a copolymer is also included to lower the viscosity. Moreover, the liquids described in the aforementioned US specification would also not have the required thixotropic properties to be effective vehicle cleaning compositions.

The term thixotropic is often used loosely to refer to a variety of properties. As used herein, thixotropic means shear thinning with slow recovery. That is to say that on being subjected to high shear rates, the viscosity of a thixotropic liquid will be reduced significantly but on cessation of the shear, the viscosity will only return to its original value after a finite period. This property enables a vehicle cleaner according to the invention at its working concentration to be thinner by high pressure application and to run over a large surface area before the viscosity rises again so that it remains on the surface to continue emulsification of soil, before being rinsed off.

The nonionic surfactant system may comprise one or more nonionic detergent actives. The composition as a whole may further comprise other detergent active material selected from one or more anionic, cationic, zwitterionic or amphoteric agents. Such agents are commercially available and are fully described in the literature, for example in "Surface Active Agents and Detergents", Volumes I and II by Schwartz, Perry and Berch.

Preferably, in addition to the nonionic system, the composition further comprises at least one amphoteric agent.

Suitable non-ionic detergent agents are the condensation products of alcohols having from 8 to 16 carbon atoms, and alkylphenols with alkylene oxides including ethylene oxide, propylene oxide, butylene oxide and mixtures thereof. Preferably the alcohols are linear, having from 12 to 15 carbon atoms, and are condensed with 2 to 10 moles of ethylene oxide. Particularly preferred are the commercial products sold under the trade names of Dobanol 25-3EO and Synperonic 7EO (ex Shell Chemicals and ICI, both UK, respectively). For ideal rheological and detergency properties it is preferred that the average HLB of the nonionic surfactant system is less than 12, especially around 10.

By amphoteric agent is meant an agent possessing both a quaternary ammonium and anionic (for example carboxy, sulphonate or sulphate) radicals. One suitable such agent is that sold by ABM Chemicals under the Tradename Amphionic XL. When one or more amphoteric agents are present, the total amphoteric content of the composition preferably is from 2 to 7% by weight.

Suitable anionic detergent materials are of the sulphate or sulphonate type. Examples thereof are salts (including sodium, potassium, ammonium and substituted ammonium salts, such as mono-, di- and tri-ethanolamine salts) of Cg-C20 alkyl benzenesulphonates, C8-C22 primary or secondary alkanesulphonates, C8-C24 olefinsulphonates, C8-C22 alkylsulphates, C8-C24 alkyl polyglycolethersulphates, containing up to 10 moles of ethylene oxide; further examples are described in "Surface Active Agents and Detergents" (vide supra) Preferred are alkylpolyglycolether sulphates having from 12 to 15 carbon atoms in the alkyl radical and containing from 2 to 8 moles of ethylene oxide.When present the anionic detergent material is normally present in an amount of 2 to 4% by weight of the total composition.

Preferably, the caustic agent is selected from one or more alkali metal hydroxides and/or alkaline salts of alkali metals. Preferred alkali metal hydroxides are sodium hydroxides (caustic soda) and potassium hydroxide (sodium potash). Preferred alkaline salts are sodium metasilicate, sodium ash, trisodium phosphate, sodium tripolyphosphate, sodium orthosilicate, tetrasodium pyrophosphate and tetrapotassium pyrophosphate. When the caustic agent comprises an alkali metal hydroxide, it is very desirable also to include a metasilicate, e.g. sodium, to protect any aluminium which comes into contact with the compositions during use. Although the pH of the composition in aqueous dilution at the working concentration is 11 or less, preferably it should be below 10.

According to the present invention an organic solvent should be included, which may be any such solvent suitable for solving greasy soiling. Preferably the organic solvent is selected from the group of water-soluble glycolethers having the general formula: R[O(CH2)x]yOH in which x=2 to 4; y=1 to 4 and R is an aryl group or an alkyl group having from 1 to 4 carbon atoms.

Particularly preferred is diethyleneglycolmonobutylether, commercially available under the Tradename of Carbitol. The organic solvent is preferably included in an amount of from 2 to 10% by weight of the total composition.

The salts of nitrilotriacetic acid which are especially preferred are the trisodium, tripotassium, triammonium, trimonoethanolammonium, tridiethanolammonium and tri-triethanolammonium salts.

One preferred such agent is that sold by BASF under the Tradename 'Trilon A'. The total nitrilotriacetic acid and (when present) nitrilotriacetate content of the composition is preferably from 2 to 7% by weight.

Although as implied above, according to the present invention it is preferred that a hydrotropic agent should not be included, in some compositions it may be desired to include some of such an agent. This can for example be chosen from the organic alcoholphosphate esters and the short alkyl chain aryl-sulphonates. Preferred are the phosphate esters of C10-C16 alcohols, such as the commercially available product of Triton H66 (ex Rhom & Haas Co., USA), and the toluene-, xylene- or cumene-sulphonates. However, when included, it is preferred that the amount of hydrotropic agent be kept as low as possible, for example from 0.5 to 2.5% by weight of the total composition.

Suitable thickening agents. are found among the alkali-stable thickening compounds, such as e.g. alkali-stable polymers and inorganic clay thickeners. Preferred are cellulosic polymers, such as e.g, hydroxyethylcellulose and magnesium silicate thickeners. Most preferred are polyacrylates, for example the product E2185 sold by Rhom & Haas. Preferably, they are included from 0.5 to 1.5% by weight of the total composition.

The composition may also contain other optional minor ingredients, such as dyes, the balance being water.

Preferably the compositions are applied in aqueous solutions having working strength concentrations ranging from about 1 to about 50% by weight, especially around 5% and the resulting in viscosities from about 1 to about 10 mPaS at 20"C and 165 sex~' shear rate. The recovery time after application of shear is typically in the order of 1-25 seconds, typically about 5 seconds. The viscosity of the undiluted composition at 21 sec-1 at 20"C is typically in excess of 500 mPaS.

Products according to the invention are of a thixotropic nature, which allows adhesion to vertical surfaces without draining off. Such behaviour ensures a sufficient concentration of detergent in contact with the soil for a period long enough for the detergent to act thereon.

Movement of the tenacious detergent layer by a water jet across the soiling creates a shear stress which disrupts the traffic film.

The shear-thinning property of the compositions of the invention allows application as a spray to the vehicle surface. Thus the product can be applied from a compressed air cylinder or via a pressure-washer fitted with the facility to apply a pre-diluted detergent solution instead of water, or with a post-pump injector which draws up the correct quantity of composition to make the solution in situ.

The invention is further illustrated by way of example, all percentages being by weight of the total composition, unless otherwise indicated.

EXAMPLE Ingredients C12-C,5 alcohol ethoxylate (3EO) 6.5 C12-C15 alcohol ethoxylate (7EO) 5.5 Amphionic XL 4.0 Caustic liquor (NaOH 47% active) 4.0 Sodium metasilicate 3.0 diethyleneglycolmonobutylether 5.5 Trilon A (40% active) 4.0 Water/20% polyacrylate (E2185) 6/12 Water, dye balance

Claims (11)

1. A liquid detergent composition comprising: a) from 5 to 30% by weight of a nonionic surfactant system; b) from 1 to 15% by weight of caustic material; c) from 1 to 15% by weight of organic solvent; d) from 1 to 10% by weight of at least one sequestering agent selected from nitrilotriacetic acid and salts thereof; and e) from 0.1 to 2.5% by weight of thickening agent; the balance being water; said composition being thixotropic when diluted with water to a predetermined concentration at which it has a pH of 12 or less.

2. A composition according to claim 1, further comprising one or more other detergent active agents.

3. A composition according to claim 2, wherein the one or more other detergent active agents comprises an amphoteric surfactant.

4. A composition according to any preceding claim, wherein the average HLB of the nonionic surfactant system is less than 12.

5. A composition according to claim 4, wherein the average HLB is around 10.

6. A composition according to any preceding claim, wherein the pH at the predetermined concentration is below 10.0.

7. A composition according to any preceding claim, wherein the predetermined concentration is from about 1 to about 50% by weight.

8. A composition according to any preceding claim, having a viscosity in excess of 500 mPaS at a shear rate of 21sex~' at 20"C.

9. An aqueous solution comprising about 5% by weight of a composition according to any preceding claim, having a viscosity of from about 1 to about 10 mPaS at 165sex~' shear rate at 200C. -

10. A solution according to claim 9, wherein the viscosity recovery time is from about 1 to about 25 seconds.

11. A solution according to claim 10, wherein the recovery time is about 5 seconds.