Liquid abrasive cleaner compositions

Abstract

 The invention relates to liquid abrasive cleaning compositions containing particulate abrasive materials stably suspended therein. Increased classification of the particulate abrasive materials allows the use of particle size distributions with higher mean size, resulting in very good cleaning performance. By classification to a particle size distribution such that the classification ratio between the upper cut-off particle size and the mean particle size is equal to or below 2.5:1, products are obtained with very good cleaning properties and reduced surface damage.

Description

[0001] The present invention relates to liquid abrasive cleaner compositions comprising particulate abrasive material stably suspended in an aqueous liquid medium.

[0002] Liquid abrasive cleaners have been known in the art for many years. They are widely used in the ordinary household cleaning of hard surfaces as they provide a convenient means for the elimination of stubborn soils, greases, burnt-on materials and stains which are not removed or not completely removed by abrasive-free cleaning products.

[0003] Over the last two decades a multitude of publications have dealt with the formulating of liquid abrasive cleaners. A majority of these publications focus on the stability and suspending properties of the aqueous liquid medium. Suspending media have e.g. been described in the British patent specifications Nos 1 167 597, 1 181 607, 1 262 280, 1 303 810, 1 308 190 and 1 418 671. Other disclosures are concerned with the stability of the suspending media under high shear rates during processing, such as the European patent specifications Nos 0 050 887 and 0 080 221.

[0004] Over recent years liquid abrasive cleaners have become increasingly more sophisticated, the in-use properties other than straightforward cleaning efficiency becoming relevant factors in the consumer appreciation. Accordingly, the art is aiming at liquid abrasive cleaner products which display a combination of properties such as cleaning efficiency, non-scratching behaviour, rich foaming, a non-gritty creamy appearance, good rinsability, etc.

[0005] Unfortunately, various of these properties prove to be difficult to combine in one product. Good cleaning efficiency is difficult to achieve simultaneously with non-scratching behaviour and/or non-grittiness. The same applies e.g. to a combination of rich foaming and easy rinsability.

[0006] Although it has long been recognised that the size of the abrasive is of the greatest importance for an effective cleaner, only in the recent art has it been indicated that the specific particle size distribution of the abrasive material may play an important rôle in the formulation of liquid abrasive cleaner products which, to an acceptable extent, satisfy a number of the desired properties simultaneously.

[0007] In the British patent specification N^o 1 581 433 it has been disclosed that rinsing properties are considerably improved if the amount of finest particles in the abrasive powder used in making the cleaner is reduced. In preferred particle distributions less than 20% by weight of the particles are of size below 10 micrometres and substantially no particles are of size above 125 micrometres.

[0008] In the United States patent N^o 4 181 633 there are disclosed liquid abrasive cleaner compositions comprising calcium metasilicate as sole abrasive, or in conjunction with calcium carbonate, which are stated to yield abrasive cleaners of superior cleaning action and reduced abrasion. The abrasive material should have a mean particle size in the range of about 5.5 to 16 micrometres and substantially no particles above 40 micrometres.

[0009] In the United States patent N^o 4 302 347 all-purpose liquid abrasive cleaners are disclosed comprising from 1 to 20% by weight of water-insoluble particulate abrasive of particle sizes in the range of 1 to 40 micrometres. Compositions are stated to have a creamy consistency and to exhibit effective removal of grease and other soils with effective polishing action and virtually no scratching.

[0010] In the British patent specification N^o 2 125 428 liquid scouring cleanser compositions are described comprising an abrasive powder of mean particle size between 4 and 17.5 micrometres with substantially no particles of size above 75 micrometres. An improved soft and smooth consistency is combined with acceptable cleaning performance.

[0011] Compared to the conventional household liquid abrasive cleaners comprising abrasive powders with particle sizes ranging from 1 to about 150 micrometres and mean particle size of between 10 and 50 micrometres, recent prior art suggests a considerable shift to lower particle size ranges and sharper distributions, thereby improving consistency and rinsing properties without unacceptable loss of cleaning performance.

[0012] Although the shift to lower mean particle sizes does not result in unacceptable cleaning efficiency on, in particular, the softer soils, hitherto no liquid abrasive cleaners have been formulated which combined the cleaning performance of the conventional coarse-­sized abrasive cleaners and the creamy texture, the non-grittiness and the non-damaging behaviour to substrates of the fine-sized abrasive cleaners recently suggested in the art.

[0013] It has now been found that increased classification of the abrasive material surprisingly allows the use of particle distributions of higher mean size without adverse effects on the advantageous consistency and non-scratching properties of the fine-sized particle distributions. The use of higher mean-sized particle distributions results in very good cleaning performance also with respect to the harder soils.

[0014] Without being bound to any theory, it is believed that effective cleaning performance on, in particular, harder soils can only be established by particles having sizes which are comparable to the thickness of such hard soils. The increased risk of scratching behaviour can be minimised by using narrow size distributions, whereby, during application, the pressure exerted on the abrasive particles is equally distributed over all particles.

[0015] In accordance with these findings the present invention provides a liquid abrasive cleaner composition comprising particulate abrasive material stably suspended in an aqueous liquid medium, the particle distribution of the abrasive material being such that the ratio (classification ratio) between the upper cut-­off particle size and the mean particle size is equal to or below 2.5:1.

[0016] Suitable particle size distributions in accordance with the present invention are highly classified. They have a relatively low classification ratio between the upper cut-off particle size, i.e. the particle size substantially all abrasive particles have sizes below, and the mean particle size which is here to be understood as the size at which 50% by weight of the particles are larger and 50% are smaller. Suitable particle size distributions should have a classification ratio equal to or below 2.5:1. Preferred are classification ratios equal to or below 2.0:1, ratios equal to or below 1.8:1 being preferred most.

[0017] Particularly suitable have been found abrasive particle distributions which have cut-offs at both sides of the distribution. The classification at the upper side preferably results in particle size distributions substantially having no particles of size above 90 micrometres, preferably lacking any particles of size above 75 micrometres or even above 70 micrometres.

[0018] The classification at the lower side should result in particle size distributions having less than 10% by weight of particles with sizes below 20 micrometres, distributions having less than 10% by weight of particles with sizes below 25 or even 30 micrometres being preferred.

[0019] In accordance with the suitable range of classification ratios, the full benefits of the present invention are obtained by a mean particle size of above 40 micrometres, in particular within the range of from 40 to 65 micrometres. Preferably the mean particle size lies within the range of from 45 to 55 micrometres.

[0020] Suitable for use as the abrasive material are both natural and synthetic abrasives, for example dolomite, precipitated calcium carbonate (aragonite), feldspar, alumina, silica abrasives, such as quartz and quartzite; preferably an abrasive material is used with a hardness on Moh's scale of from 1 to 4. Particularly suitable is calcite, for instance limestone, chalk or marble, such as those forms of calcite referred to in UK Patent 1 345 119. The abrasive material is generally present in an amount of from 1 to 65%, preferably from 2 to 60%, and most preferably from 40 to 55% by weight of the final composition.

[0021] The liquid medium normally comprises an aqueous medium in which an anionic detergent material is present, preferably in combination with a nonionic or zwitterionic detergent material. Suitable anionic surfactants are alkali metal or alkanol amine salts of C₁₂-C₁₈ branched or straight chain alkylaryl sulphonates, of C₁₀-C₁₈ alkyl (EO)_1-10 sulphates, of C₁₀-C₂₄ fatty acid soaps etc. In general the amount of anionic surfactant will vary between 0.5 and 15%, preferably between 2 and 10% by weight of the final composition.

[0022] It is often desirable to include also a nonionic or zwitterionic detergent material in the aqueous medium in an amount of from 0.3 to 7%, preferably from 0.5 to 5% by weight. Suitable examples of nonionic detergents are water-soluble condensation products of ethylene and/or propylene oxide with linear primary or secondary C₈-C₁₈ alcohols, with C₈-C₁₈ fatty acid amides or fatty acid alkylolamides (both mono- and diamides), with C₉-C₁₈ alkyl phenols and so on. The alkoxylated C₈-C₁₈ fatty acid mono- and dialkylolamides should contain more than one alkylene oxide unit; for example, they should be condensed with e.g. 2-5 moles of alkylene oxide such as ethylene oxide. Fatty acid mono- or di-alkylolamides in which the fatty acid radical contains 10-16 carbon atoms are also suitable nonionics, such as for instance coco fatty acid mono- or diethanol amide. Suitable zwitterionic detergents are trialkyl amine oxides having one long alkyl chain (C₈-C₁₈) and two short (C₁-C₄) alkyl chains; betaines and sulphobetaines.

[0023] It is highly desirable that the liquid medium should exhibit Bingham plastic characteristics, thus forming a stable suspending medium for the abrasive material. Such media using the above-mentioned surfactants, possibly in combination with other surfactants, are described in British patent specifications 1 167 597, 1 181 607, 1 262 280, 1 303 810, 1 308 190 and 1 418 671. It is often desirable that a liquid abrasive cleanser also comprises an electrolyte or mixture of electrolytes, such as alkalimetal chlorides, -nitrates, -silicates, -borates, -carbonates, -sulphates, -ortho­phosphates, -pyro- and -polyphosphates, -citrates, -nitrilotriacetates and mixtures thereof. The level of electrolyte will range from 0 to 25 percent, preferably from 5 to 20 percent by weight of the liquid medium without the abrasive materials.

[0024] It may also be desirable to impart additional thickening by inclusion of a thickening agent. Suitable thickening agents for inclusion in the present compositions are natural or synthetic clays selected from the group of expandable layered clays such as the alumino and magnesium silicates. Examples thereof are the smectite clays such as montmorillonite (bentonite), hectorite and saparite, and the attagulgite clays such as those commercially available under the trade-name Attagel®.

[0025] Other adjuncts for liquid abrasive cleansers may be included, such as colouring agents, perfumes, fluorescers, hydrotropes, soil-suspending agents, bleaching agents, bleach precursors, enzymes, opacifiers, germicides, humectants, etc.

[0026] The invention will further be described by way of examples.

[0027] To illustrate the advantages of the invention, the results of comparative tests are presented in which the following liquid scouring composition was used:

[0028] Comparative tests were performed on liquid scouring cleaners according to the above formulation, only differing in their calcite particle size distributions. In Table 1 the tested distributions are characterised by their upper and lower end cut-offs and their mean particle size, those denoted by letters being conven-­tional distributions, whereas those denoted by numerals are in accordance with the present invention. Particle sizes were determined by the laser granulometer method using a Cilas granulometer®.

[0029] The following tests were carried out:

Cleaning efficiency

[0030] By means of a screen printing technique, a fat/flour mixture is applied as a thin layer to large titanium enamel or stainless steel test pieces. This soil is then pyrolysed at 250°C. The test pieces, after ageing for at least 48 hours, are secured by means of 2 clamps onto the "Sheen wet scrub tester". The burnt-on soil is rubbed off using the test product applied via a special cleaning head. The number of rubs taken to clean the test piece is then recorded.

Tactile feel of grittiness

[0031] The fingers can readily feel gritty particles when a cream scourer is rubbed between the thumb and fingers.

[0032] By asking a panel of people to feel product between their fingers and ranking them as smooth, slightly gritty - to considerably gritty, on a 0-4 scale, a Tactile Grittiness score can be obtained.

Surface damage

[0033] Testing was carried out on the Sheen Wet Abrasion Scrubber, using a soft sponge head at a surface pressure of 5-17 grams/cm² on Perspex® and on Formica®.

[0034] Assessments were made by specular reflection differences at an angle of 45°C using the Solartron®.

[0035] The following results were obtained:

Claims

1. A liquid abrasive cleaning composition comprising from 1-65% by weight of classified particulate abrasive material stably suspended in an aqueous liquid medium, said composition comprising from 0.5 to 15% by weight of an anionic detergent material and from 0.3 to 7% by weight of a nonionic or zwitterionic detergent material and from 0 to 25% by weight of an electrolyte, characterised in that the particle size distribution of the classified abrasive material is such that the classification ratio between the upper cut-off particle size and the mean particle size is equal to or below 2.5:1.

2. A composition according to claim 1, characterised in that the classification ratio is equal to or below 1.8:1.

3. A composition according to claim 1 or 2, characterised in that the classified particulate abrasive material does not have particles of a size of above 90 micrometres and does not contain more than 10% by weight of particles of a size of below 20 micrometres.

4. A composition according to claims 1-3, characterised in that the classified particulate abrasive material has a mean particle size of between 40 and 65 micrometres.

5. A composition according to claim 4, characterised in that the classified particulate abrasive material has a mean particle size of between 45 and 55.