Detergent tablets

Abstract

The invention relates to a detergent tablet comprising from 5 to 20 percent by weight citric acid or a salt thereof and from 3 to 25 percent by weight sodium benzoate and a surfactant. The invention also relates to a method of forming a wash liquor by combining a detergent tablet with water in a container. The invention also relates to the use of a detergent tablet to create a washing liquor for cleaning surfaces.

Description

[0001] DETERGENT TABLETS

[0002] Field of the Invention

[0003] The field of the invention concerns detergent tablets suitable for dilution to form a wash liquor.

[0004] Background of the Invention

[0005] Detergent tablets are a known means of allowing an end user to form a ready to use liquid wash liquor, simply by the addition of a water to the detergent tablet (and optionally by agitating the mixture of water and the detergent tablet). They provide a convenient means of reducing storage space (during processing, distribution and at the point of sale) and allowing ingredients with a limited shelf life in liquid form to be incorporated into the solid and only converted into a wash liquor at the point of use.

[0006] One such use is in the formation of a multi-purpose spray cleaner. Such a product can be used to clean a variety of surfaces, for example a table, cooker or a tiled surface. In such an instance the tablet can be added directly to an empty bottle, mixed with water and then released from the bottle, for example via a trigger spray. Such bottles can be reused multiple times. Such a use is particularly common in industrial cleaning (e.g. hotel or restaurant kitchen cleaning), whereby large surface areas need to be cleaned relatively quickly, and so the ability to simply reuse the bottle and quickly refill it using a source of water and another detergent tablet is extremely useful. In this way employees working in such sectors are saved significant time and effort over the course of a shift, as effort is saved in having to dispose of and seek a fresh bottle multiple times.

[0007] Another example use is in the formation of a floor cleaning wash liquor. In such an instance the tablet is typically added to a bucket of water and allowed to dissolve. The wash liquor is then applied to directly to the floor, typically via a mop or sponge. Cleaning a large area often results in the end user needing to fill the bucket multiple times. This is made easier through the use of detergent tablets. As these are relatively portable the end user can carry multiple with them as they clean, this is easier than carrying out a concentrated bottle of liquid detergent ingredients which can be quite heavy. When forming a wash liquor it is important that the wash liquor is clear. This is because a clear liquid acts as a signal to the end user that the formation of the wash liquor is complete - in other words the tablet is fully dissolved and the liquor is ready to use.

[0008] It is also important that such wash liquors are adequately preserved from microbial contamination. This is because in many circumstances the wash liquor may be formed and stored in a container for use on several distinct occasions.

[0009] Despite the prior art there exists the need for a tablet comprising a preservative that when mixed with water provides sufficient preservation for the subsequently created wash liquor and secondly behaves such that the wash liquor created is clear.

[0010] Summary of the Invention

[0011] In a first aspect of the invention, there is disclosed a tablet comprising citric acid and / or a citrate salt and from 3 to 25 percent by weight sodium benzoate. Without wishing to be bound by theory, it is believed that the presence of citric acid and I or sodium citrate facilitates the dissolution of sodium benzoate in such a way as to promote transparent solutions of detergent tablets comprising sodium benzoate.

[0012] In a second aspect of the invention a method of forming a wash liquor comprising combining the detergent tablet with water is provided.

[0013] In a third aspect of the invention use of the tablet of the first aspect of the invention is provided to create a washing liquor for cleaning surfaces.

[0014] These and other aspects, features and advantages will become apparent to those of ordinary skill in the art from reading of the following detailed description. For the avoidance of doubt, any feature of one aspect of the present invention may be utilized in any other aspect of the invention. The word “comprising” is intended to mean “including” but not necessarily “consisting of” or “composed of.” In other words, the listed steps or options need not be exhaustive. It is noted that the examples given in the description below are intended to clarify the invention and are not intended to limit the invention to those examples per se. Similarly, all percentages are weight / weight percentages unless otherwise indicated. Except in the operating and comparative examples, or where otherwise explicitly indicated, all numbers in this description indicating amounts of material or conditions of reaction, physical properties of materials and / or use are to be understood as modified by the word “about”. Numerical ranges expressed in the format “from x to y” are understood to include x and y. When for a specific feature multiple preferred ranges are described in the format “from x to y”, it is understood that all ranges combining the different endpoints are also contemplated.

[0015] Detailed Description of the Invention

[0016] Detergent tablet

[0017] By “detergent tablet” as used herein, is meant a solid tablet suitable for dissolution in water to create a liquid wash liquor comprising detersive ingredients.

[0018] Preservative

[0019] The detergent tablet contains a preservative. The preferred preservative for use in the invention is sodium benzoate. Alternative preservatives may also be included in the detergent tablet. Suitable alternative preservatives include phenoxyethanol, dehydroacetic acid and isothiazolinone-based preservatives.

[0020] Sodium benzoate is included at from 3 to 25wt.% of the detergent tablet, more preferably at from 3 to 20wt.% of the detergent tablet, more preferably at from 3 to 15wt.% of the detergent tablet, more preferably at from 3 to 10wt.% of the detergent tablet and most preferably at from 3 to 5wt.% of the detergent tablet.

[0021] It is preferred that if alternative preservatives are present then they are included at a level of less than 1wt% of the detergent tablet, more preferably less than 0.5wt% of the detergent tablet, and most preferably less than 0.1 wt% of the detergent tablet.

[0022] Effervescent

[0023] The composition comprises an effervescent. By “effervescent” as used herein, is meant an ingredient that expediates the dissolution of the tablet in water, by releasing gas when it is brought into contact with water. The preferred effervescent for use in the invention is citric acid and / or a citrate salt. Alternative effervescents may also be included in the detergent tablet. Suitable alternative effervescents include organic acids such as tartaric acid, fumaric acid, malic acid, adipic acid, succinic acid, and a carbonate salt. Preferred carbonate salts include sodium carbonate, potassium carbonate, calcium carbonate, sodium bicarbonate, potassium bicarbonate, calcium carbonate, calcium bicarbonate and magnesium carbonate as well as mixtures thereof.

[0024] The level of effervescent is from 5 to 20wt.% of the tablet, preferably from 10 to 20wt% and most preferably from 15 to 20wt%. of the tablet.

[0025] Effervescent to preservative ratio

[0026] Preferably the effervescent to preservative ratio in detergent tablets according to the invention are from 6:1 to 1 :1 by weight, more preferably from 5:1 to 1 :1 , more preferably from 4:1 to 1 :1 , more preferably from 3:1 to 1 :1 and most preferably from 2:1 to 1 :1 by weight.

[0027] By “disintegrant” as used herein, is meant an ingredient present in a tablet to accelerate dissolution of the tablet in water. In contact with water such ingredients cause the tablet to break or disintegrate into smaller fragments thereby accelerating the dissolution.

[0028] The detergent tablet preferably comprises a soluble disintegrant and an insoluble disintegrant. The soluble disintegrant preferably comprises glucose monohydrate. The insoluble disintegrant preferably comprises polyvinyl polypyrrolidone.

[0029] By “polyvinyl polypyrrolidone” as used herein, is meant highly crosslinked polyvinyl pyrrolidone. Polyvinyl polypyrrolidone is water-insoluble, but it is water swellable.

[0030] EMDEX® - is a commercially available material. It is a combination of glucose monohydrate and various starch-derived polysaccharides at a 19:1 weight ratio. It provides a suitable soluble disintegrant. Surfactant

[0031] Tablets according to the invention comprise surfactant. Preferably the tablets comprise from 10 to 50wt% surfactant, more preferably from 12 to 40wt% surfactant and most preferably from 14 to 30wt% surfactant by weight of the tablet.

[0032] Preferably the surfactant comprises anionic surfactant. If present the anionic surfactant is present at from 1 to 100wt% of the total surfactant content.

[0033] Preferably the surfactant comprises nonionic surfactant. If present the nonionic surfactant is present at from 1 to 100wt% of the total surfactant content.

[0034] Most preferably the surfactant comprises both anionic and non-ionic surfactant.

[0035] Preferably the anionic surfactant is selected from alkyl sulphate, alkyl ether sulphate, linear alkyl benzene sulphonate (LAS), taurate and combinations thereof. Most preferably the anionic surfactant selected from linear alkyl benzene sulphonate and a taurate and combinations thereof. Preferably the taurate surfactant is sodium methyl cocoyl taurate.

[0036] Commercial LAS is a mixture of closely related isomers and homologues alkyl chain homologues, each containing an aromatic ring sulfonated at the “para” position and attached to a linear alkyl chain at any position except the terminal carbons. The linear alkyl chain typically has a chain length of from 11 to 15 carbon atoms, with the predominant materials having a chain length of about C12. Each alkyl chain homologue consists of a mixture of all the possible sulpho-phenyl isomers except for the 1 -phenyl isomer. LAS is normally formulated into compositions in acid (i.e. , HLAS) form and then at least partially neutralized in-situ. The counterion for anionic surfactants is generally an alkali metal such as sodium or potassium; or an ammoniacal counterion such as monoethanolamine, (MEA) diethanolamine (DEA) or triethanolamine (TEA), monoisopropanolamine (MIPA). Mixtures of such counterions may also be employed. Sodium and potassium are preferred. An example of a suitable commercial grade of LAS is Ufaryl DL 8, available from Unger Fabrikker AS.

[0037] If an alkyl ether sulphate is selected then preferably it contains from one to ten ethylene oxide or propylene oxide units per molecule, and more preferably it contains one to three ethylene oxide units per molecule. If an alkyl sulphate is selected then preferably it comprises an alkyl chain length of from 10 to 18, more preferably it comprises primary alkyl sulphate (PAS) with an average alkyl chain length of about 12.

[0038] Further anionic surfactants suitable for the present invention include salts of organic sulphates and sulphonates having alkyl radicals containing from about 8 to about 22 carbon atoms, the term “alkyl” being used to include the alkyl portion of higher acyl radicals. Examples of such materials include alkaryl sulfonates, alpha-olefin sulfonates and mixtures thereof. The alkyl radicals preferably contain from 10 to 18 carbon atoms and may be unsaturated.

[0039] Preferably the amount of the anionic surfactant is in the range up to 100% by weight of the total amount of the surfactant. More preferably, the amount of anionic surfactant is in the range 10 to 90%, even more preferably 20 to 80%, most preferably 30 to 70% by weight of the total amount of surfactant.

[0040] The tablet according to the present invention may comprise a non-ionic surfactant.

[0041] Suitable non-ionic surfactants include water soluble aliphatic ethoxylated non-ionic surfactants including the primary aliphatic alcohol ethoxylates and secondary aliphatic alcohol ethoxylates. This includes the condensation products of a higher alcohol (e.g., an alkanol containing about 8 to 16 carbon atoms in a straight or branched chain configuration) condensed with about 4 to 30 moles of ethylene oxide, for example, lauryl or myristyl alcohol condensed with about 10 moles of ethylene oxide (EO), tridecanol condensed with about 6 to 15 moles of EO, myristyl alcohol condensed with about 10 moles of EO per mole of myristyl alcohol, the condensation product of EO with a cut of coconut fatty alcohol containing a mixture of fatty alcohols with alkyl chains varying from 10 to about 14 carbon atoms in length and wherein the condensate contains either about 6 moles of EO per mole of total alcohol or about 9 moles of EO per mole of alcohol and tallow alcohol ethoxylates containing 6 EO to 11 EO per mole of alcohol.

[0042] An example of a suitable commercially available non-ionic is Genapol® T250 (available from Clariant). Another group of suitable non-ionic surfactants are alkyl polyglycosides(APG) which are sugar derivatives of fatty alcohol. Example of such surfactants are decyl glucoside, lauryl glucoside, myristyl glucoside.

[0043] The tablet may further comprise a cationic or an amphoteric surfactant in addition to the anionic and the non-ionic surfactant.

[0044] Suitable cationic surfactants are quaternary ammonium salts. According to the present invention quaternary ammonium salts are characterised in that the ammonium salt has the general formula: R1 R2R3R4N+X- wherein R1 is a C12 to C18 alkyl group, each of R2, R3 and R4 independently is a C1 to C3 alkyl group and X is an inorganic anion. R1 is preferably a C14 to C16 straight chain alkyl group, more preferably C16. R2, R3 and R4 are preferably methyl groups. The inorganic anion (X-) is preferably chosen from halide, sulphate, bisulphate or hydroxide.

[0045] For the purposes of this invention, a quaternary ammonium hydroxide is considered to be a quaternary ammonium salt. More preferably the anion is a halide ion or sulphate, most preferably a chloride or sulphate. Cetyl-trimethylammonium chloride is a specific example of a suitable compound and commercially abundantly available.

[0046] Another type of quaternary ammonium cationic surfactant is the class of benzalkonium halides, also known as alkyldimethylbenzylammonium halides. The most common type being benzalkonium chloride, also known as alkyldimethylbenzylammonium chloride (or ADBAC). Suitable amphoteric surfactants include derivatives of aliphatic quaternary ammonium, sulphonium and phosphonium compounds having an aliphatic radical of from 8 to 18 carbon atoms and an aliphatic radical substituted by an anionic water-solubilising group, for instance 3- (N-N-dimethyl-N-hexadecylammonium) propane-1 -sulphonate betaine, 3-(dodecyl methyl sulphonium) propane-1 -sulphonate betaine and 3- (cetylmethylphosphonium) ethane sulphonate betaine.

[0047] Examples of amphoteric surfactants suitable for the present invention include cocoamidopropyl betaine (CAPB), cocoamidopropyl amine oxide (CAPAO), cocodiethanol amide (CDEA) and cocomonoethanol amide (CMEA). Filler

[0048] Typically detergent tablets comprise one or more filler ingredients. Fillers suitable for use in the tablet include sodium carbonate, calcium carbonate, zeolite, clays such as bentonite, dolomite and combinations thereof. A preferred filler is sodium carbonate.

[0049] Hydrotrope

[0050] The tablet may comprise a hydrotrope. Hydrotropes are a class of low molecular weight compounds having a hydrophilic and hydrophobic part similar to surfactants. However, the hydrophobic part is much smaller compared to surfactants. Thus, they may not lead to spontaneous self-aggregation or micellar solubilization. It is also observed that the hydrotrope does not have a critical micellar concentration (CMC) or a critical vesicle concentration (CVC) like surfactants. It may possible that hydrotrope aggregates in a stepwise self-aggregation process, gradually increasing aggregation size. Preferably the hydrotrope comprises an alkyl aryl sulphonate having C1 to C5 alkyl chain.

[0051] The tablet preferably comprises 0.1 to 10% by weight of the hydrotrope. More preferably the tablet comprises 0.2 to 9% by weight, even more preferably 0.3 to 8% by weight and most preferably 0.3 to 7% by weight of the hydrotrope.

[0052] The hydrotrope may be selected from sodium xylene sulphonate, sodium toluene sulphonate, sodium cumene sulphonate, potassium xylene sulphonate, potassium toluene sulphonate, potassium cumene sulphonate and combinations thereof. Most preferred hydrotropes are sodium cumene sulphonate and / or sodium xylene sulphonate.

[0053] Dye

[0054] The composition may comprise one or more dyes to provide colour to the tablet.

[0055] Process of making a tablet

[0056] In the process a homogenised dry powder is prepared by mixing the ingredients in specified ratio. Subsequently, the powder is filled in a die-block and compressed to form the tablet. A rotary press or a hydraulic press maybe employed to compress the powder to tablet.

[0057] Preferably the pressure applied during the compression is in the range 1 to 100 kg-f / cm2, more preferably 2.5 to 75 kg-f / cm2, even more preferably 5 to 50 kg-f / cm2, and most preferably 7.5 to 30 kg-f / cm2. Mass of tablet

[0058] Tablets according to the invention can be manufactured in a variety of sizes. The preferred mass of a single tablet is from 2 to 20g, more preferably from 3 to 15g and most preferably from 4 to 10g. Such a size allows for a sufficient mass of surfactant to be included such that the resulting liquid wash liquor has sufficient surfactant to function in a plethora of applications, for example a floor cleaner or multi-surface spray, in particular such a floor cleaner or multi-surface spray suitable for use in an industrial cleaning context.

[0059] Compression strength

[0060] Preferably the tablet has a compression strength of from 50 to 300N, more preferably 60 to 270N, more preferably from 70 to 250N and most preferably from 80 to 240N.

[0061] Method of producing a liquid wash liquor

[0062] The tablet according to the present invention may be formulated for cleaning surfaces, in particular hard surfaces. Hard surface cleaning compositions are generally used for cleaning surfaces such as: kitchen utensils, dishes, kitchen platforms, tabletops, worktops, floors etc. One of such examples is a tablet for dishwashing. Another of such examples is a tablet for floor cleaning.

[0063] It may also be possible to formulate the tablet for providing a multi-use liquid detergent. The consumer may prepare a liquid detergent by dissolving the tablet in a secondary container and storing it for multiple uses.

[0064] There is provided a method for providing a liquid wash liquor comprising the steps of combining a tablet according to the present invention with water in a container, optionally agitating the mixture and waiting for 5 minutes or less for at least 80% of the tablet to have dissolved. Preferably the ratio of the tablet to water is in the range of 1 :10 to 1 :10,000 by weight. More preferably the ratio of the tablet to water is in the range 1 :15 to 1 :5,000 by weight, even more preferably 1 :20 to 1 : 1 ,000 and most preferably 1 :25 to 1 :500 by weight. P0000957WQ

[0065] 10

[0066] Use of a detergent tablet

[0067] Use of the detergent tablet disclosed in the first aspect of the invention is herein disclosed for the creation of a liquid wash liquor. A wash liquor is created when the detergent tablet is

[0068] 5 sufficiently dissolved such that the cleaning ingredients originally contained in the tablet are dissolved into the water. The liquor is then ready for use by an end user. Preferably such a wash liquor is formed in 5 minutes or less.

[0069] Methods of testing

[0070] 10 Several properties of the tablets produced were assessed by dissolving the tablets in water at 25°C.

[0071] Appearance on Dissolution

[0072] Tablets were dissolved in water. Dissolution was assessed by placing the 2 tablets at a time in

[0073] 15 750ml of water at 25°C. The water was then stirred gently and the time point at which no visible portions of solid material remained was recorded as the dissolution time. The appearance of the water was also noted at this point and characterized qualitatively as to whether the solution was transparent (clear) or hazy.

[0074] Examples

[0075] Table 1: Test tablets were produced using the following ingredients:

[0076] Fine grade of citric acid: particle size distribution: 90% of material is from mesh sizes 20 to 40.

[0077] Table 2: Resulting ratios of citric acid to sodium benzoate:

[0078] In each case 5 cylindrical-shaped tablets of 10-15 g with a diameter of 20mm and a height of 23mm were produced. The tablets were produced by adding the relevant ingredients one at a time into a suitable airtight container and the container was sealed (with sufficient headspace to allow mixing). The composition was then shaken vigorously for 2 minutes to ensure good mixing of the ingredients. The mixture was then filled into a die-block and compressed to form a tablet.

[0079] Results

[0080] The following results are the average results across 5 tablets for the compositions described in table 1.

[0081] Table 3 - performance data (for tablets compressed at 98N / cm2)

[0082] Discussion of results

[0083] As can be seen in the results in table 3, if the level of sodium benzoate is too high then the resulting wash liquor is hazy. If the sodium benzoate level is reduced too low then the wash liquor fails to be adequately preserved. However, the results demonstrate that a sodium benzoate weight percent inclusion of up to 29% is possible in such a detergent tablet without an ensuing hazy solution upon dissolution.

Claims

Claims1. A detergent tablet comprising from 5 to 20 percent by weight citric acid or a salt thereof, from 3 to 25 percent by weight sodium benzoate and surfactant.

2. A detergent tablet according to any preceding claim wherein the ingredient comprising citric acid or a salt thereof comprises sodium citrate.

3. The detergent tablet according to any preceding claim comprising an anionic surfactant.

4. The detergent tablet according to any preceding claim comprising a non-ionic surfactant.

5. The detergent tablet according to any preceding claim comprising a hydrotrope.

6. The detergent tablet according to any preceding claim comprising a fragrance.

7. The detergent tablet according to any preceding claim wherein the citric acid or a salt thereof is in particulate form.

8. The detergent tablet according to claim 7 wherein 90 percent or more by weight of the citric acid or a salt thereof has a particle size with a maximum dimension of from 0.425mm to 0.850mm.

9. The detergent tablet according to any preceding claim with a total mass of from 2 to 20g.

10. A method of forming a wash liquor comprising combining a detergent tablet according to any of claims 1-9 and water in a container.

11. A method according to claim 10 wherein the weight ratio of the detergent tablet to the water in the container is from 1 : 10 to 1 : 10,000.

12. Use of the tablet of a detergent tablet according to any of claims 1 to 9 to create a washing liquor for cleaning surfaces.

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