Cleaning compositions

Abstract: A homogenous thickened cleaner for hard surfaces comprises a water soluble abrasive, a surfactant and a thickener in an aqueous base and the suspension of the abrasive is achieved without using a high concentration of surfactant despite the high ionic strength contributed by the abrasive through the use of an polyacrylate with anionic side chains as the thickening agent. Typical compositions comprise 20 to 50 wt% sodium bicarbonate or other abrasive, up to 5 wt% alkyl benzene sulphonate surfactant and 1 to 8 wt% anionic polyacrylate.

Description: The present invention relates to detergent compositions, including cream cleaners. Cream cleaners are aqueous cleaning liquids with a creamy consistency which are used to clean hard surfaces. They are typically pourable homogeneous liquids and generally contain an abrasive component. One type of abrasive cleaner contains a water insoluble abrasive component. Typical water-insoluble abrasives are insoluble carbonates, e.g. calcite and dolomite. Cream cleaners of this type are mentioned in EP 0 334 566A. As explained in this specification it is difficult to remove the insoluble particles by rinsing. This is because the suspending agent used to hold the abrasive in suspension in the cleaner becomes ineffective on dilution. Attempts have been made to overcome the problems resulting from the use of insoluble abrasive particles by the use of abrasive materials which are water soluble but under the conditions of use as a cleaner are present at sufficiently high concentrations to give a solid having abrasive properties. In theory it should be possible to dissolve any residual abrasive left on a surface after use by rinsing with sufficient water. EP 0 193 375 discloses a cleaner which contains a hydrated crystalline solid in an amount greater than that required to form a saturated solution. Several different water soluble salts are listed namely sodium bicarbonate, sodium tripolyphosphate pentahydrate, and sodium tetraborate decahydrate. EP 0 334 566 mentioned above proposes to use potassium sulphate to provide the abrasive solid. WO 91/08282 also discloses a hard surface cleaner containing water soluble solids as abrasives. A minimum detergent concentration of 1.5% by weight is specified although the minimum concentration exemplified is over 5%. The use of certain structuring agents to provide appropriate rheological properties is disclosed, including the use of Carbopol cross linked acrylic acid polymers and of copolymers of ethylene and maleic acid, to quote two of several examples. No compositions of this kind are exemplified. It is said that the detergent concentration should be sufficient to make the composition self thickening, i.e. to thicken the composition without the use of other thickening agents. The compositions based on water soluble abrasives have the problem that they require high levels of surfactants in order to maintain the abrasive in suspension. The amount of surfactant required for this purpose is well in excess of that required to provide a cleaning action. The presence of large amounts of anionic and nonionic surfactants gives rise to problems of foam formation which hinders effective rinsing of the surfaces which have been cleaned. EP 0 193375 mentions the problem of foam formation and refers to the addition of a suds regulating material such as soap. However the suds regulating ability of soap is limited. Cream cleaners currently on the market contain soap but still have problems with rinsability because of persistent and excessive foam. EP-A-301885 discloses aqueous cleaning compositions comprising 0.3 to 20% surfactant, 0.05 to 25% water soluble inorganic or organic salt, 25 to 70% abrasive and 0.01 to 0.5% polyacrylate. However, the polyacrylate is not present as a thickening agent and is not present in a thickening amount. EP-A-1242697 describes aqueous cleaning compositions comprising 0.25 to 12% surfactant, abrasive and 0.1 to 1% polyacrylate. The abrasive is not water soluble. There is a need for an alternative cleaner formulation. According to the present invention there is provided a homogeneous, thickened, abrasive aqueous detergent composition comprising one or more surface active compounds, and a water soluble abrasive component, said composition containing sufficient of the abrasive component for this to be present as a solid suspended in a saturated solution of itself, characterised in that the composition contains less than 1.5 percent by weight of a non-ionic or anionic surface active compound and as a thickening agent comprises from 1 to 8 percent by weight of an anionic polymer composition capable of stabilising and thickening the suspension of said abrasive component in said saturated solution in the presence of said surface active compound or compounds. The abrasive is a water soluble particulate material which is present in sufficient amounts to be present as undissolved solid in the composition. Examples of abrasives which can be used are sodium bicarbonate, sodium bicarbonate/carbonate mixtures, sodium carbonate, sodium tripolyphosphate pentahydrate, and sodium tetraborate decahydrate ( some of which are disclosed in EP 0 193 375A), and potassium sulphate as disclosed in EP 0 334 566. The preferred abrasive material is sodium bicarbonate or a mixture thereof with sodium carbonate. The quantity of abrasive used will depend on the water solubility of the materials used as abrasive in the cleaning composition and also on the suspending power of the composition but may for example be in the range 25 to 50 %, more preferably 30 to 40%, by weight of the total composition. The thickening agent is a polyacrylate. The anionic character may be conferred by the presence of anionic groups such as carboxylic acid groups, sulphate groups or sulphonic acid groups. Preferably, the anionic polyacrylate may be an acrylic acid homopolymer or copolymer, eg. a copolymer with a non-ionic comonomer such as an acrylic ester or amide. Other compatible non-ionic comonomers may be used. Other anion contributing monomers which may be employed include maleic acid and fumaric acid. A particularly suitable anionic acrylate polymer is Allied Colloids SALCARE SC91 (RTM). This is an off white, mobile liquid with a slight acrylic odour, a gravimetric solids content of 50%, a viscosity as supplied of 250cps(RVT Brookfield Spindle 2, 50 rpm at 25°C, a pH of 7 in 2% solution, a boiling point in excess of 100°C, a density at 20°C of 1.18g/cm 3 and a viscosity in 2% solution of 30,000 cps (RVT Brookfield Spindle 6, at 20 rpm). The molecular weight of the thickening agent is preferably from 1500 to 10,000. Various polymer thickening agents are known, including polyacrylates. However the presence of electrolyte (such as a salt such as sodium bicarbonate) usually results in complete loss of viscosity when attempts are made to use polyacrylates or other polymers to thicken aqueous solutions containing electrolyte. This phenomenon is experienced usually at electrolyte levels corresponding in ionic strength to from 0.01 to 0.1M and above, although it may be experienced below this range depending on the nature of the polymer and the electrolyte. We have found however that by using an anionic polyacrylate and small quantities of anionic or non-ionic surfactant thickened solutions containing electrolyte can be obtained. Without wishing to be bound by any theory we believe that the anionic side chains of the polyacrylate are incorporated into micelles of the surfactant to produce structure. Accordingly, the thickening agent/surface active combination employed is such as to be able to thicken in the presence of the saturated abrasive solution. The quantity of thickening agent such as polyacrylate will depend on the degree of thickening required but will be in the range 1 to 8% weight, based on weight of composition, more preferably 3 to 6% by weight. The composition contains one or more surfactants to interact with the polyacrylate to give the required degree of thickening. The surfactant is preferably anionic but nonionic surfactants or blends thereof with anionic surfactants may be used. Many different anionic detergents are known, and are discussed in for example EP O 334 566A. Examples of anionic surfactants which may be used are the alkyl benzene sulphonates such as dodecyl benzene sulphonate, and alkyl ether sulphates such as those containing from 1 to 3 ethylene oxide groups, and with alkyl groups containing from 12 to 20 carbon atoms. The cation may be an alkali metal or an ammonium or quaternary ammonium group. Suitable non-ionic surfactants are disclosed in W091/08282. The quantity of anionic surfactant is preferably kept at a low level. This reduces the need for expensive ingredients, and reduces the problem of excessive foaming when rinsing. The quantity of surfactant should be sufficient to interact with the polyacrylate or other thickening agent to give a thickened composition with adequate suspending power for the abrasive used. The optimum concentrations may be found by simple tests. The concentrations of surfactant are in the range of 0.5% to less than 1.5%., preferably 0.5 to 1% by weight of the total composition. Surprisingly, it has been found that the viscosity of the composition increases as the concentration of anionic surfactant is decreased. The composition preferably does not contain any cationic surfactant although these are not forbidden. Other ingredients may be present which are conventionally used in cream cleaners. However because the abrasive can be suspended without the need to use large quantities of surfactant it will not normally be necessary to use a suds regulator. The pH of the composition should preferably be in the range 7 to 10, eg. about 8.5. The pH may be adjusted using suitable bases such as triethanolamine, or sodium hydroxide. The abrasive material may itself contribute to or achieve pH adjustment, eg. if a mixture of sodium carbonate and bicarbonate is used. Although preferably a pourable composition suitable for use in cleaning hard surfaces, a composition according to the invention may be thicker in consistency, eg. being suitable to be squeezed through an orifice from a container such as a bottle or tube. Accordingly, such compositions may be formulated as dental cleaning compositions and the like. The present invention will now be described with reference to the following experiments in which examples of the invention are identified by number and comparative tests, not according to the invention, are identified by letter. Example 1 A formulation was prepared from the ingredients listed in the Table using conventional mixing equipment. The triethanolamine was added to an aqueous solution of the anionic surfactant (the sodium salt of alkyl benzene sulphonate) followed by the sodium bicarbonate, and the anionic polyacrylate. The quantities of ingredients are shown in the table. The concentration of sodium bicarbonate present in the solution phase was found to be approximately 1 M. Example 2 A formulation was prepared as in Example 1. The ingredients used are shown in Table 1. These formulations showed no sign of sedimentation after 3 months storage at ambient temperature. They were effective cleaners for hard surfaces and were easy to rinse off after use as they gave no problems of foaming or leaving mineral residues on cleaned surfaces. Component Example 1 Example 2 % weight % weight water 63.60 62.50 alkyl ether sulphate (Na) 0 1.00 alkyl benzene sulphonate 1.10 0 sodium bicarbonate 30.00 30.00 anionic polyacrylate 4.50 4.50 triethanolamine 1.80 2.00 The alkyl ether sulphate was a commercially available material sold under the trade name SYNPERONIC 3S27, supplied by Cargo Fleet. The alkyl benzene sulphonate which was neutralized with sodium hydroxide to form the alkykl benzene sulphonate was a commercially available material sold under the designation BP 1141 by Young's Detergents. The anionic polyacrylate was a material supplied by Allied Colloids under the designation DP6-5738 and which is more recently known as SALCARE SC91 (RTM). Comparative Test A A composition was prepared as in Example 1 except that it did not contain any alkyl ether sulphate. Comparative Test B A composition was prepared s in Example 1 except that it did not contain any alkyl benzene sulphonate. The compositions of Test A and B gave a thin (low viscosity) liquid with no suspending power for the sodium bicarbonate. Example 3 A composition was prepared by mixing the ingredients shown in Table 2 below: COMPONENT AMOUNT % weight water 62.49 non-ionic ethoxylated alcohol (100%) 0.9% triethanolamine (85%) 2.11 sodium bicarbonate 30 SALCARE SC91 (RTM) 4.5 The non-ionic ethoxylated alcohol was SYNPERONIC A7 which is a C 13 -C 15 alcohol ethoxylated with seven units of ethylene oxide. SYNPERONIC is a Registered Trade Mark. The resulting composition had a creamy, homogeneous consistency and was stable on storage. It had a pH of 8.4.

Claims: A homogeneous, thickened, abrasive aqueous detergent composition comprising one or more surface active compounds, and a water soluble abrasive component, said composition containing sufficient of the abrasive component for this to be present as a solid suspended in a saturated solution of itself, characterised in that the composition contains less than 1.5 percent by weight of a non-ionic or anionic surface active compound and as a thickening agent comprises from 1 to 8 percent by weight of an anionic polyacrylate polymer composition capable of stabilising and thickening the suspension of said abrasive component in said saturated solution in the presence of said surface active compound or compounds. A composition as claimed in claim 1, wherein said water soluble abrasive substance is sodium bicarbonate, sodium carbonate, a sodium bicarbonate/carbonate mixture, sodium tripolyphosphate pentahydrate, sodium tetraborate decahydrate or potassium sulphate or a mixture of two or more thereof. A composition as claimed in claim 1 or claim 2, wherein said abrasive component makes up from 20 to 50 percent by weight of the composition. A composition as claimed in any preceding claim, wherein said anionic polyacrylate is a homopolymer of acrylic acid or a copolymer of acrylic acid. A composition as claimed in claim 4, wherein said polyacrylate is a copolymer of acrylic acid and an acrylic ester, amide or other non-ionic acrylic monomer. A composition as claimed in any preceding claim, wherein said polyacrylate has a molecular weight in the range of from 1500 to 10,000. A composition as claimed in any preceding claim, containing from 0.5 to 1 percent by weight of said surface active compound, or of said surface active compounds in aggregate.

Inventors: NEIL THOMAS BRUCE, NEIL, THOMAS BRUCE
Applicants: MCBRIDE ROBERT GROUP LTD, THE ROBERT MCBRIDE GROUP LIMITED
Application year: 1993
Main classification: C11D3
IPC codes: C11D3, C11D17