CA2307276A1 - Effervescent tablets containing tabletting aids and a process for their production - Google Patents

Abstract

Effervescent tablets distinguished by good tablettability, high initial hardnesses and high edge fracture resistance contain one or more organic acids, one or more substances from the group of carbonates and/or hydrogen carbonates, optionally other ingredients of detergents and 2 to 20% by weight of one or more water-soluble substances with a melting point between 40 and 100°C. Preferably, they contain substances from the group consisting of 1,10-decanediol, trimethylol propane, .epsilon.-caprolactam, glutaric acid and sodium ammonium hydrogen phosphate tetrahydrate ("phosphorus salt").

Description

EFFERVESCENT TABLETS CONTAINING TABLETTING AIDS AND A
PROCESS FOR THEIR PRODUCTION
Field of the Invention This invention relates generally to compact shaped bodies (hereinafter referred to as tablets) with detersive properties and more particularly to tablets containing a so-called effervescent system, more especially descaling tablets.
Background of the Invention Detergent tablets are widely described in the prior-art literature and are enjoying increasing popularity among consumers because they are easy to dose. Tabletted detergents have a number of advantages over powder-form detergents: they are easier to dose and handle and, by virtue of their compact structure, have advantages in regard to storage and transportation. As a result, detergent tablets are also comprehensively described in the patent literature. One problem which repeatedly arises in the production of detergent tablets is the inadequate "tablettability" of certain mixtures, particularly when these mixtures contain large amounts of acids. If the premixes to be tabletted flow too poorly, for example, or if the individual particles are too hard or brittle, dosing of the premixes into the die of the tablet press is extremely difficult and the resulting tablets often have inadequate hardnesses or abrasion resistances and edge stabilities.
Effervescent tablets are widely described in the prior art because the incorporation of gas-evolving systems often leads to better disintegration and dissolving times.
Thus, International patent application WO 97143366 (Procter &
Gamble) describes a laundry detergent composition with improved dissolvability, even in the form of a detergent block or tablet, which contains 0.5 to 60% by weight of anionic surfactant, 0.01 to 30% by weight of cationic surfactant and an effervescent system of acid and alkali. The problem of unsatisfactory tablettability or descaling tablets are not mentioned in this document.
International patent application WO 87102052 (Ockhuizen et al.) describes a detergent in the form of an effervescent tablet containing 2 to 6% by weight of a laundry detergent concentrate, 40 to 60% by weight of hydrogen carbonate, 33 to 53% by weight of a solid organic acid (more particularly a 2:3 mixture of citric acid and tartaric acid), 1.5 to 2.5% by weight of binder (PVP), 0.1 to 1 % by weight of lubricant and additional quantities of colloidal silicon dioxide. Abrasion stability, edge fracture, poor tablettability or descaling tablets are not mentioned in this document either.
European patent application EP 687 464 (Allphamed Arzneimittel-Gesellschaft) describes an effervescent tablet which may also be used in the form of laundry detergent tablets and which consists of at least one active substance or a combination of active substances, at least one binder, optionally carriers, such as fragrances, dyes, perfumes, softeners, bleaching agents and effervescent additives, the binder used being propylene glycol or glycerol. A process for the production of these effervescent tablets is also claimed.
British patent application GB 2,096,162 (Warner-Lambert) describes an effervescent tablet containing 35 to 60% by weight of monopersulfate, up to 20% by weight of alkaline) (earth) metal halide, 0.5 to 20% by weight of perborate, 0.15 to 0.5% by weight of dye and potassium iodide andlor potassium bromide as indicators.
A perfume-containing effervescent tablet which additionally contains sorbitol as carrier material and carbonate andlor bicarbonate and an organic acid as the gas-evolving system is disclosed in German patent application DE 4133 862 (Henkel).
The problem addressed by the present invention was to minimize the above-mentioned problems in the production of effervescent tablets.

Tabletting aids were to be found, above all for high-acid premixes, that would provide for problem-free tabletting and would give tablets distinguished by high initial hardnesses after tabletting and by a distinctly reduced tendency towards edge breakage. Certain substances have been found to be particularly suitable for this purpose.
Description of the Invention The present invention relates to effervescent tablets containing one or more organic acids, one or more substances from the group of carbonates andlor hydrogen carbonates and optionally other ingredients of detergents, characterized in that they additionally contain 2 to 20% by weight, based on tablet weight, of one or more water-soluble substances with a melting point between 40 and 100°C.
In the context of the present invention, the term "melting point"
characterizes the temperature at which the liquid phase and the solid phase of a substance are in thermodynamic equilibrium at 1.013 bar pressure. Under this definition, the melting point is identical with the freezing point or the solidification point providing supercooling phenomena are disregarded in the latter case. In actual fact, however, the term "melting point" is generally used in practice only for the transition point from the solid to the liquid state, but not for the identical temperature at which the transition occurs in the opposite direction. Accordingly, at the melting point, a substance changes from the ordered solid state into the unordered liquid state (melting), i.e. the amplitude of vibration of the particles -which increases with increasing temperature - becomes so great at that temperature that the lattice structure is destroyed.
In the context of the present invention, the term "water-soluble"
characterizes the property of a substance whereby it dissolves in water.
For practical reasons, however, the "water-soluble" substances are preferably quantified in regard to that property. Accordingly, substances with a solubility in distilled water at 20°C of more than 100 grams per liter of water are preferred as tabletting aids for the purposes of the present invention. Particularly preferred tabletting aids with a melting point of 40 to 100°C have solubilities (in water at 20°C) above 125 g/l, preferably above 150 gll, more preferably above 175 gll and most preferably above 200 g/l.
Some examples of tabletting aids suitable for the purposes of the invention are set out in the following Table:
Melting Solubility point [C] [g/l H20]

Ammonium aluminium sulfate dodecahydrate93 150 Potassium aluminium sulfate dodecahydrate92 110 Aluminium sulfate monohydrate 90 600 Aluminium sulfate octadecahydrate 90 600 Sodium phosphinate monohydrate 90 1000 Sodium dihydrogen phosphate 100 1103 Sodium dihydrogen phosphate monohydrate100 1103 Sodium ammonium hydrogen phosphate 79 167 tetrahydrate Disodium hydrogen phosphate heptahydrate48 154 Trisodium phosphate dodecahydrate 75 258 Tripotassium phosphate heptahydrate 46 900 Ammonium iron(II) sulfate hexahydrate 100 269 Iron sulfate heptahydrate 64 400 Glucose 83 820 Magnesium acetate tetrahydrate 80 1200 Manganese(II) chloride tetrahydrate 58 1980 Sodium acetate trihydrate 58 762 Sodium hydrogen sulfate monohydrate 58 670 Sodium carbonate peroxohydrate 60 150 Sodium thiosulfate pentahydrate 48 680 Potassium sodium tartrate tetrahydrate70-80 630 D(+)-glucose monohydrate 83 820 Zinc acetate dehydrate 100 430 Zinc sulfate heptahydrate 40 960 The substances listed above may be used in accordance with the invention as tabletting aids. However, there are other, particularly preferred tabletting aids which are not included in the above Table. Thus, according to the invention, particularly preferred effervescent tablets are characterized in that they contain 2 to 20% by weight, preferably 3 to 17.5% by weight, more preferably 4 to 15% by weight and most preferably 5 to 12.5% by weight, based on tablet weight, of one or more substances 5 from the group of polyethylene glycols, alcohol alkoxylates, glycerol mono-and difatty acid esters, di-, tri- and polyols, carboxylic acids, lactams and ammonium phosphates as the water-soluble substances with a melting point between 40 and 100°C.
According to the invention, substances belonging to the above mentioned groups which are present in the effervescent tablets must satisfy the "water-soluble" criteria on the one hand and the melting point criterion on the other hand. Certain representatives of the groups mentioned have proved to be particularly suitable. Particularly preferred effervescent tablets contain one or more substances from the group consisting of 1,10 decanediol, trimethylol propane, s-caprolactam, glutaric acid and sodium ammonium hydrogen phosphate tetrahydrate ("phosphorus salt") in quantities of 2.5 to 18% by weight, preferably in quantities of 6 to 16% by weight and more preferably in quantities of 8 to 11% by weight, based on the weight of the effervescent tablet, as the water-soluble substances with a melting point of 40 to 100°C.
1,10-Decanediol (melting point 73°C) can be obtained, for example, by reduction of sebacic acid. Its use is preferred for the purposes of the present invention.
Like 1,1,1-tris-(hydroxymethyl)-propane, trimethylol propane is a trivial name for 2-ethyl-2-hydroxymethyl-1,3-propanediol, H5Cz-C(CH20H)3.
It is marketed in the form of a colorless hygroscopic mass with a melting point of 57-59°C and may also be used with advantage as a tabletting aid for the purposes of the present invention.
s-Caprolactam (6-aminohexanoic acid lactam, 6-hexane lactam, azepan-2-one) is marketed in the form of colorless hygroscopic lamellae with a melting point of 69°C. Caprolactam is readily soluble in water and, on an industrial scale, is produced from cyclohexanone oxime by Beckmann rearrangement. The cyclohexanone is prepared either by cyclohexane oxidation or by phenol nucleus hydrogenation and subsequent cyclohexanol dehydrogenation or by cyclohexylamine dehydrogenation and subsequent cyclohexylimine hydrolysis. The subsequent oximation of the cyclohexanone is carried out with hydroxylamine sulfate. Caprolactam is obtained from the cyclohexanone oxime formed by Beckmann rearrangement in sulfuric acid oleum. Caprolactam is used for the production of synthetic fibers and may also be used with advantage for the purposes of the present invention.
Glutaric acid (pentanedioic acid) is commercially obtainable in the form of large colorless monoclinic crystals and has a melting point of 97°C.
On an industrial scale, glutaric acid is produced by oxidative ring opening of cyclopentanone with 50% nitric acid in the presence of vanadium(V} oxide.
So far as its suitability as a tabletting aid is concerned, it is particularly preferred for the purposes of the present invention.
Sodium ammonium hydrogen phosphate tetrahydrate, which is known as "phosphorus salt" in qualitative chemical analysis, may also be used as a tabletting aid for the purposes of the present invention.
Besides the substances mentioned, glycerol mono- and difatty acid esters in particular may be used as tabletting aids. According to the invention, preferred effervescent tablets contain one or more substances corresponding to general formula I, 11, III or IV:
CH2-O-R' CH2-O-H CH2-O-R' CHZ-O-R' CH2-O-H CH2-O-R' CH2-O-R2 CH2-O-H
CHz-O-H CH2-O-H CH2-O-H CH2-O-R2 (I) (II) (III) (IV) in which the substituents R' and R2 independently of one another are selected from saturated, mono- or diunsaturated acyl groups containing 12 to 22, preferably 14 to 20 and more preferably 16 to 18 carbon atoms, preferably glycerol monostearate, as the water-soluble substances with a melting point of 40 to 100°C.
In formulae I to IV above, preferred fatty acid residues (acyl groups) are the residues of such fatty acids as dodecanoic acid (lauric acid), tetradecanoic acid (myristic acid), hexadecanoic acid (palmitic acid), octadecanoic acid (stearic acid), eicosanoic acid (arachic acid), docosanoic acid (behenic acid), tetracosanoic acid (lignoceric acid), hexacosanoic acid (cerotic acid), triacontanoic acid (melissic acid) and the unsaturated species 9c-hexadecenoic acid (palmitoleic acid), 6c-octadecenoic acid (petroselic acid), 6t-octadecenoic acid (petroselaidic acid), 9c-octadecenoic acid (oleic acid), 9t-octadecenoic acid (elaidic acid), 9c,12c-octadecadienoic acid (linoleic acid), 9t,12t-octadecadienoic acid (linolaidic acid) and 9c,12c,15c-octadecatrienoic acid (linolenic acid). For reasons of cost, technical mixtures of the individual acids obtainable from the hydrolysis of fats are used in preference to the pure species. Mixtures such as these are, for example, coconut oil fatty acid (ca. 6% by weight C8, 6% by weight Coo, 48% by weight C~2, 18% by weight C~4, 10% by weight C~6, 2% by weight C~B, 8% by weight C~B~, 1 % by weight C~B~~), palm kernel oil fatty acid (ca. 4% by weight C8, 5% by weight Coo, 50% by weight C~z, 15% by weight C~4, 7% by weight C~6, 2% by weight CAB, 15% by weight C~8~, 1 % by weight C~8~~), tallow fatty acid (ca. 3% by weight C~4, 26% by weight C~6, 2% by weight C~6~, 2% by weight C~~, 17% by weight C~8, 44%
by weight C~8~, 3% by weight C~s~~, 1 % by weight C~s~~~), hydrogenated tallow fatty acid (ca. 2% by weight C~4, 28% by weight C~6, 2% by weight C», 63% by weight C~8, 1 % by weight C~B~), technical oleic acid (ca. 1 % by weight C~2, 3% by weight C~4, 5% by weight C~s, 6% by weight C~s~, 1 % by weight C», 2% by weight C~8, 70% by weight C~B~, 10% by weight C~B~~, 0.5% by weight C~8~~~), technical palmitic/stearic acid (ca. 1 % by weight C~2, 2% by weight C~4, 45% by weight C~6, 2% by weight C~~, 47% by weight CAB. 1 % by weight C~B~) and soybean oil fatty acid (ca. 2% by weight C~a, 15% by weight C~6, 5% by weight C~8, 25% by weight C~B~, 45% by weight C~8~~, 7% by weight C~8~~~). Partly hydrolyzed native fats and oils may of course also be used as glycerol mono- and diesters providing they meet the above-mentioned criteria in regard to melting point and solubility in water.
Besides the tabletting aids, the effervescent tablets according to the invention contain a gas-releasing system of organic acids and carbonateslhydrogen carbonates.
Suitable organic acids which release carbon dioxide from the carbonateslhydrogen carbonates in aqueous solution are, for example, the solid mono-, oligo- and polycarboxylic acids. Preferred members of this group are citric acid, tartaric acid, succinic acid, malonic acid, adipic acid, malefic acid, fumaric acid, oxalic acid and polyacrylic acid. Organic sulfonic acids, such as amidosulfonic acid, may also be used. The mixture of succinic acid (max. 31 % by weight), glutaric acid (max. 50% by weight) and adipic acid (max. 33% by weight) commercially obtainable as Sokalan~
DCS (Trade Mark of BASF) may also be used with advantage as an acidifying agent for the purposes of the present invention. According to the invention, preferred effervescent tablets contain 10 to 80% by weight, preferably 20 to 75% by weight and more preferably 30 to 70% by weight of one or more organic acids from the group consisting of adipic acid, amidosulfonic acid, succinic acid, citric acid, fumaric acid, malefic acid, malonic acid, oxalic acid and tartaric acid.
The acids mentioned do not have to be used in a stoichiometric ratio to the carbonateslhydrogen carbonates present in the tablets. In the preferred application of the effervescent tablets according to the invention as descaling tablets, it is even desirable in many cases to use the acids) in excess. Amidosulfonic acid is particularly preferred by virtue of its good descaling effect. Amidosulfonic acid, which is often also referred to as amidosulfuric acid or sulfamic acid, is marketed in the form of colorless, odorless, noninflammable, nonhygroscopic, nonvolatile orthorhombic crystals and, on an industrial scale, is obtained from urea, sulfur trioxide and sulfuric acid or from ammonia and sulfur trioxide.
In another preferred embodiment, the effervescent tablets according to the invention contain more than 40% by weight, preferably more than 50% by weight and more preferably more than 60% by weight, based on tablet weight, of amidosulfonic acid.
In the effervescent tablets according to the invention, the gas-releasing effervescent system consists of carbonates andlor hydrogen carbonates in addition to the organic acids mentioned. Of the various representatives of this class of substances, the alkali metal salts are distinctly preferred for reasons of cost. Among the alkali metal carbonates and/or hydrogen carbonates, the sodium and potassium salts are distinctly preferred to the other salts for reasons of cost. The pure alkali metal carbonates andlor hydrogen carbonates do not of course have to be used, instead mixtures of different carbonates and hydrogen carbonates may be preferred.
Sodium carbonate forms a white powder with a density of 2.532 gcm-3, a distinction being drawn between light calcined soda with a bulk density of 0.5 to 0.55 kgll and heavy calcined soda with a bulk density of 1.0 to 1.1 kgll. Sodium carbonate forms three hydrates with water: sodium carbonate decahydrate (crystal soda), Na2C03 ~ 10H20, colorless, monoclinic crystals ice-like in appearance with a density of 1.44 gcm-3, melting point 32-34°C; sodium carbonate heptahydrate, Na2C03 ~ 7H20, rhombic crystals with a density of 1.51 gcm-3, melting point 32-35°C;
sodium carbonate monohydrate, Na2C03 ~ H20, rhombic crystals with a density of 2.25 gcm-3, melting point 100°C.
Sodium hydrogen carbonate is a white, alkaline-tasting, odorless powder (monoclinic crystals) stable in dry air with a density of 2.159 gcm-3 which decomposes into C02, H20 and sodium carbonate on heating to 5 >65°C.
Potassium carbonate (potash) is a white, nontoxic, hygroscopic granular substance with a density of 2.428 gcm-3 which forms various hydrates. If large amounts of carbon dioxide are introduced into concentrated potassium carbonate solution, the poorly soluble potassium 10 hydrogen carbonate is precipitated. For the rest, potassium carbonate is very similar in its properties to its close relation soda. Potassium carbonate-1.5-water ("potash hydrate") is the stable phase of potassium carbonate in contact with the saturated solution in the range from 0°C
to about 110°C and can be recovered by crystallization from supersaturated potassium carbonate solutions. It crystallizes in the form of substantially dust-free crystals which sparkle like glass, has a density of 2.155 gcm-3 and completely loses its water of crystallization at temperatures of 130 to 160°C. Most industrial processes for the production of potassium carbonate lead first to the potassium carbonate-1.5-water which is calcined at 200 to 350°C in a revolving tube furnace to form 98 to 100%
potassium carbonate. In the absence of this calcination step, the crystallized potassium carbonate-1.5-hydrate is dried at 110 to 120°C and sold as potash hydrate. Standard industrial processes for producing the products mentioned are, for example, the process with continuous crystallization (starting materials: KOH and C02), the fluidized bed process (starting materials: KOH and C02), the amine process (KOHICOz in the presence of isopropylamine: Mines de Potasse d'Alsace or KOH/C02 in the presence of triethylamine: Kali-Chemie AG) or the Nephelin digestion process (mainly former USSR). Of minor importance or of purely historical interest are the ion exchanger process (starting materials: KCI and (NH4)zC03), the magnesia process (Engel-Precht process, Neustaf3furter process; starting materials: KCI, MgC03 3 H20 and C02), the formate-potash process (starting materials: potassium sulfate, calcium hydroxide and carbon monoxide), the Piesteritz process (starting materials: potassium sulfate and calcium cyanamide) and the Le Blanc process (starting materials:
potassium sulfate, calcium carbonate and carbon).
According to the invention, trona - a mixed salt of sodium carbonate and sodium hydrogen carbonate which is also known as sodium sesquicarbonate or sodium carbonate sesquihydrate - may also be used as the second component of the effervescent system. Sodium carbonate sesquihydrate occurs naturally as a mineral (trona) and is described by the formula Na2C03 ~ NaHC03 ~ 2 H20. Large occurrences of trona can be found, for example, in the USA (Green River, Wyoming), Kenya (Lake Magadi) and the Republic of Sudan (Dongola). Whereas the occurrences in Africa can be extracted by quarrying, in the USA trona is mined. Trona has a density of 2.17 gcm-3 and a Mohs' hardness of 2.5. Normally, trona is used for the production of pure soda. However, it is also possible using the sodium sesquicarbonate process to obtain pure Na2C03 ~ NaHC03 ~ 2 HZO which is marketed. Pure sodium sesquicarbonate is also formed from sodium hydrogen carbonate by allowing it to stand in moist air with elimination of carbon dioxide or by introducing carbon dioxide into a sodium carbonate solution.
Preferred effervescent tablets contain 5 to 30% by weight, preferably 10 to 25% by weight and more preferably 12.5 to 20% by weight, based on tablet weight, of alkali metal carbonates and/or hydrogen carbonates, preferably sodium carbonate.
Besides the effervescent system, the additional organic acids and the tabletting aids, the effervescent tablets according to the invention may contain other important detergent ingredients, more particularly builders.
Preferred effervescent tablets according to the invention additionally contain one or more substances from the groups of builders, complexing agents, bleaching agents, bleach activators, enzymes, dyes and perfumes.
The effervescent tablets according to the invention may contain any of the builders typically used in detergents, i.e. in particular ~eolites, silicates, carbonates, organic cobuilders and also the phosphates.
Suitable crystalline layered sodium silicates correspond to the general formula NaMSixO2X+~A y H20, where M is sodium or hydrogen, x is a number of 1.9 to 4 and y is a number of 0 to 20, preferred values for x being 2, 3 or 4. Crystalline layered silicates such as these are described, for example, in European patent application EP-A-0 164 514. Preferred crystalline layered silicates corresponding to the above formula are those in which M is sodium and x assumes the value 2 or 3. Both ~- and 8-sodium disilicates Na2Si205A y H20 are particularly preferred, (3-sodium disilicate being obtainable, for example, by the process described in International patent application WO-A- 91108171.
Other useful builders are amorphous sodium silicates with a modulus (Na20:Si02 ratio) of 1:2 to 1:3.3, preferably 1:2 to 1:2.8 and more preferably 1:2 to 1:2.6 which dissolve with delay and exhibit multiple wash cycle properties. The delay in dissolution in relation to conventional amorphous sodium silicates can have been obtained in various ways, for example by surface treatment, compounding, compacting or by overdrying.
In the context of the invention, the term a morphous i s also understood to encompass "X-ray amorphous". In other words, the silicates do not produce any of the sharp X-ray reflexes typical of crystalline substances in X-ray diffraction experiments, but at best one or more maxima of the scattered X-radiation which have a width of several degrees of the diffraction angle. However, particularly good builder properties may even be achieved where the silicate particles produce crooked or even sharp diffraction maxima in electron diffraction experiments. This may be interpreted to mean that the products have microcrystalline regions between 10 and a few hundred nm in size, values of up to at most 50 nm and, more particularly, up to at most 20 nm being preferred. So-called X-ray amorphous silicates such as these, which also dissolve with delay in relation to conventional waterglasses, are described for example in German patent application DE-A-44 00 024. Compacted amorphous silicates, compounded amorphous silicates and overdried X-ray-amorphous silicates are particularly preferred.
The finely crystalline, synthetic zeolite containing bound water used in accordance with the invention is preferably zeolite A and/or zeolite P.
Zeolite MAP~ (Crosfield) is a particularly preferred P-type zeolite.
However, zeolite X and mixtures of A, X and/or P are also suitable.
According to the invention, it is also preferred to use, for example, a co-crystallizate of zeolite X and zeolite A (ca. 80% by weight zeolite X) which is marketed by CONDEA Augusta S.p.A. under the name of VEGOBOND
AX~ and which may be described by the following formula:
nNa20 ~ (1-n)K20 ~ AI203 ~ (2 - 2.5)Si02 ~ (3.5 - 5.5) H20.
Suitable zeolites have a mean particle size of less than 10 pm (volume distribution, as measured by the Coulter Counter Method) and contain preferably 18 to 22% by weight and more preferably 20 to 22% by weight of bound water.
The generally known phosphates may of course also be used as builders providing their use should not be avoided on ecological grounds.
Among the large number of commercially available phosphates, alkali metal phosphates have the greatest importance in the detergent industry, pentasodium triphosphate and pentapotassium triphosphate (sodium and potassium tripolyphosphate) being particularly preferred.
"Alkali metal phosphates" is the collective term for the alkali metal (more particularly sodium and potassium) salts of the various phosphoric acids, including metaphosphoric acids (HP03)~ and orthophosphoric acid (H3P04) and representatives of higher molecular weight. The phosphates combine several advantages: they act as alkalinity sources, prevent lime deposits on machine parts and lime incrustations in fabrics and, in addition, contribute towards the cleaning effect.
Sodium dihydrogen phosphate (NaH2P04) exists as the dihydrate (density 1.91 gcm3, melting point 60°) and as the monohydrate (density 2.04 gcm3). Both salts are white readily water-soluble powders which, on heating, lose the water of crystallization and, at 200°, are converted into the weakly acidic diphosphate (disodium hydrogen diphosphate, Na2H2P207) and, at higher temperatures, into sodium trimetaphosphate (Na3P309) and Maddrell's salt (see below). NaH2P04 shows an acidic reaction. It is formed by adjusting phosphoric acid with sodium hydroxide to a pH value of 4.5 and spraying the resulting "mash". Potassium dihydrogen phosphate (primary or monobasic potassium phosphate, potassium biphosphate, KDP), KH2P04, is a white salt with a density of 2.33 gcm3, has a melting point of 253° [decomposition with formation of potassium polyphosphate (KP03)x] and is readily soluble in water.
Disodium hydrogen phosphate (secondary sodium phosphate), Na2HP04, is a colorless, readily water-soluble crystalline salt. It exists in water-free form and with 2 moles (density 2.066 gcm3, water loss at 95°), 7 moles (density 1.68 gcm3, melting point 48° with loss of 5 H20) and 12 moles of water (density 1.52 gcm3, melting point 35° with loss of 5 H20), becomes water-free at 100° and, on fairly intensive heating, is converted into the diphosphate Na4P207. Disodium hydrogen phosphate is prepared by neutralization of phosphoric acid with soda solution using phenol-phthalein as indicator. Dipotassium hydrogen phosphate (secondary or dibasic potassium phosphate), K2HP04, is an amorphous white salt which is readily soluble in water.
Trisodium phosphate, tertiary sodium phosphate, Na3P04, consists of colorless crystals which have a density of 1.62 gcm3 and a melting point of 73-76° (decomposition) as the dodecahydrate, a melting point of 100° as the decahydrate (corresponding to 19-20% P205) and a density of 2.536 gcm3 in water-free form (corresponding to 39-40% P2O5). Trisodium 5 phosphate is readily soluble in water through an alkaline reaction and is prepared by concentrating a solution of exactly 1 mole of disodium phosphate and 1 mole of NaOH by evaporation. Tripotassium phosphate (tertiary or tribasic potassium phosphate), K3P04, is a white deliquescent granular powder with a density of 2.56 gcm3, has a melting of 1340° and is 10 readily soluble in water through an alkaline reaction. It is formed, for example, when Thomas slag is heated with coal and potassium sulfate.
Despite their higher price, the more readily soluble and therefore highly effective potassium phosphates are often preferred to corresponding sodium compounds in the detergent industry.

15 Tetrasodium diphosphate (sodium pyrophosphate), Na4P207, exists in water-free form (density 2.534 gcm3, melting point 988°, a figure of 880°
has also been mentioned) and as the decahydrate (density 1.815 - 1.836 gcm3, melting point 94° with loss of water). Both substances are colorless crystals which dissolve in water through an alkaline reaction. Na4P207 is formed when disodium phosphate is heated to >200° or by reacting phosphoric acid with soda in a stoichiometric ratio and spray-drying the solution. The decahydrate complexes heavy metal salts and hardness salts and, hence, reduces the hardness of water. Potassium diphosphate (potassium pyrophosphate), K4P207, exists in the form of the trihydrate and is a colorless hygroscopic powder with a density of 2.33 gcm3 which is soluble in water, the pH value of a 1 % solution at 25° being 10.4.
Relatively high molecular weight sodium and potassium phosphates are formed by condensation of NaH2P04 or KHZP04. They may be divided into cyclic types, namely the sodium and potassium metaphosphates, and chain types, the sodium and potassium polyphosphates. The chain types in particular are known by various different names: fused or calcined phosphates, Graham's salt, Kurrol's salt and Maddrell's salt. All higher sodium and potassium phosphates are known collectively as condensed phosphates.
The industrially important pentasodium triphosphate, Na5P30~o (sodium tripolyphosphate), is a non-hygroscopic white water-soluble salt which crystallizes without water or with 6 H20 and which has the general formula Na0-[P(O)(ONa)-O]~-Na where n = 3. Around 17 g of the salt free from water of crystallization dissolve in 100 g of water at room temperature, around 20 g at 60° and around 32 g at 100°. After heating of the solution for 2 hours to 100°, around 8% orthophosphate and 15% diphosphate are formed by hydrolysis. In the preparation of pentasodium triphosphate, phosphoric acid is reacted with soda solution or sodium hydroxide in a stoichiometric ratio and the solution is spray-dried. Similarly to Graham's salt and sodium diphosphate, pentasodium triphosphate dissolves many insoluble metal compounds (including lime soaps, etc.). Pentapotassium triphosphate, K5P30~o (potassium tripolyphosphate), is marketed for example in the form of a 50% by weight solution (> 23% P205, 25% K20).
The potassium polyphosphates are widely used in the detergent industry.
Sodium potassium tripolyphosphates, which may also be used in accordance with the invention, also exist. They are formed for example when sodium trimetaphosphate is hydrolyzed with KOH:
(NaP03)3 + 2 KOH -~ Na3K2P30~o + H20 According to the invention, they may be used in exactly the same way as sodium tripolyphosphate, potassium tripolyphosphate or mixtures thereof. Mixtures of sodium tripolyphosphate and sodium potassium tripolyphosphate or mixtures of potassium tripolyphosphate and sodium potassium tripolyphosphate or mixtures of sodium tripolyphosphate and potassium tripolyphosphate and sodium potassium tripolyphosphate may also be used in accordance with the invention.
Organic cobuilders suitable for use in the effervescent tablets according to the invention are, in particular, polycarboxylateslpolycarboxylic acids, polymeric polycarboxylates, aspartic acid, polyacetals, dextrins, other organic cobuilders (see below) and phosphonates. These classes of substances are described in the following.
Other useful organic builders are, for example, the sodium salts of the polycarboxylic acids mentioned above as part of the effervescent system. Examples of such sodium salts are those of citric acid, adipic acid, succinic acid, glutaric acid, malic acid, tartaric acid, malefic acid, fumaric acid, sugar acids, aminocarboxylic acids, nitrilotriacetic acid (NTA), providing their use is not ecologically unsafe, and mixtures thereof.
Preferred salts are the salts of the polycarboxylic acids, such as citric acid, adipic acid, succinic acid, glutaric acid, tartaric acid, sugar acids and mixtures thereof.
Other suitable builders are polymeric polycarboxylates such as, for example, the alkali metal salts of polyacrylic or polymethacrylic acid, for example those with a relative molecular weight of 500 to 70,000 glmole.
The molecular weights mentioned in this specification for polymeric polycarboxylates are weight-average molecular weights MW of the particular acid form which, basically, were determined by gel permeation chromatography (GPC) using a UV detector. The measurement was carried out against an external polyacrylic acid standard which provides realistic molecular weight values by virtue of its structural similarity to the polymers investigated. These values differ distinctly from the molecular weights measured against polystyrene sulfonic acids as standard. The molecular weights measured against polystyrene sulfonic acids are generally higher than the molecular weights mentioned in this specification.
Particularly suitable polymers are polyacrylates which preferably have a molecular weight of 2,000 to 20,000 g/mole. By virtue of their superior solubility, preferred representatives of this group are the short-chain polyacrylates which have molecular weights of 2,000 to 10,000 g/mole and, more particularly, 3,000 to 5,000 g/mole.
Also suitable are copolymeric polycarboxylates, particularly those of acrylic acid with methacrylic acid and those of acrylic acid or methacrylic acid with malefic acid. Acrylic acid/maleic acid copolymers containing 50 to 90% by weight of acrylic acid and 50 to 10% by weight of malefic acid have proved to be particularly suitable. Their relative molecular weights, based on the free acids, are generally in the range from 2,000 to 70,000 g/mole, preferably in the range from 20,000 to 50,000 g/mole and more preferably in the range from 30,000 to 40,000 glmole.
The (co)polymeric polycarboxylates may be used either in powder form or in the form of an aqueous solution. The content of (co)polymeric polycarboxylates in the detergent is preferably from 0.5 to 20% by weight and more preferably from 3 to 10% by weight.
In order to improve solubility in water, the polymers may also contain allyl sulfonic acids, such as allyloxybenzene sulfonic acid and methallyl sulfonic acid, as monomer.
Other particularly preferred polymers are biodegradable polymers of more than two different monomer units, for example those which contain salts of acrylic acid and malefic acid and vinyl alcohol or vinyl alcohol derivatives as monomers or those which contain salts of acrylic acid and 2-alkylallyl sulfonic acid and sugar derivatives as monomers.
Other preferred copolymers are those which are described in German patent applications DE-A-43 03 320 and DE-A-44 17 734 and which preferably contain acrolein and acrylic acidlacrylic acid salts or acrolein and vinyl acetate as monomers.
Other preferred builders are polymeric aminodicarboxylic acids, salts or precursors thereof. Particular preference is attributed to polyaspartic acids or salts and derivatives thereof which, according to German patent application DE-A-195 40 086, are also said to have a bleach-stabilizing effect in addition to their co-builder properties.
Other suitable builders are polyacetals which may be obtained by reaction of dialdehydes with polyol carboxylic acids containing 5 to 7 carbon atoms and at least three hydroxyl groups. Preferred polyacetals are obtained from dialdehydes, such as glyoxal, glutaraldehyde, terephthal-aldehyde and mixtures thereof and from polyol carboxylic acids, such as gluconic acid and/or glucoheptonic acid.
Other suitable organic builders are dextrins, for example oligomers or polymers of carbohydrates which may be obtained by partial hydrolysis of starches. The hydrolysis may be carried out by standard methods, for example acid- or enzyme-catalyzed methods. The end products are preferably hydrolysis products with average molecular weights of 400 to 500,000 glmole. A polysaccharide with a dextrose equivalent (DE) of 0.5 to 40 and, more particularly, 2 to 30 is preferred, the DE being an accepted measure of the reducing effect of a polysaccharide by comparison with dextrose which has a DE of 100. Both maltodextrins with a DE of 3 to 20 and dry glucose sirups with a DE of 20 to 37 and also so-called yellow dextrins and white dextrins with relatively high molecular weights of 2,000 to 30,000 glmole may be used.
The oxidized derivatives of such dextrins are their reaction products with oxidizing agents which are capable of oxidizing at least one alcohol function of the saccharide ring to the carboxylic acid function. Dextrins thus oxidized and processes for their production are known, for example, from European patent applications EP-A-0 232 202, EP-A-0 427 349, EP-A-0 472 042 and EP-A-0 542 496 and from International patent applications WO 92118542, WO 93/08251, WO 93116110, WO 94128030, WO 95107303, WO 95112619 and WO 95120608. An oxidized oligosaccharide corresponding to German patent application DE-A-196 00 018 is also suitable. A product oxidized at C6 of the saccharide ring can be particularly advantageous.
Other suitable co-builders are oxydisuccinates and other derivatives of disuccinates, preferably ethylenediamine disuccinate. Ethylenediamine 5 N,N'-disuccinate (EDDS) is preferably used in the form of its sodium or magnesium salts. Glycerol disuccinates and glycerol trisuccinates are also preferred in this connection. The quantities used in zeolite-containing andlor silicate-containing formulations are from 3 to 15% by weight.
Other useful organic co-builders are, for example, acetylated 10 hydroxycarboxylic acids and salts thereof which may optionally be present in lactone form and which contain at least 4 carbon atoms, at least one hydroxy group and at most two acid groups. Co-builders such as these are described, for example, in International patent application WO-A-95120029.
Another class of substances with co-builder properties are the 15 phosphonates, more particularly hydroxyalkane and aminoalkane phos phonates. Among the hydroxyalkane phosphonates, 1-hydroxyethane-1,1 diphosphonate (HEDP) is particularly important as a co-builder. It is preferably used in the form of the sodium salt, the disodium salt showing a neutral reaction and the tetrasodium salt an alkaline reaction (pH 9).

20 Preferred aminoalkane phosphonates are ethylenediamine tetramethylene phosphonate (EDTMP), diethylenetriamine pentamethylenephosphonate (DTPMP) and higher homologs thereof. They are preferably used in the form of the neutrally reacting sodium salts, for example as the hexasodium salt of EDTMP or as the hepta- and octasodium salts of DTPMP. Of the phosphonates, HEDP is preferably used as a builder. In addition, the aminoalkane phosphonates have a pronounced heavy metal binding capacity. Accordingly, it can be of advantage, particularly where the detergents also contain bleach, to use aminoalkane phosphonates, more particularly DTPMP, or mixtures of the phosphonates mentioned.
In addition, any compounds capable of forming complexes with alkaline earth metal ions may be used as co-builders.
Among the compounds yielding H202 in water which serve as bleaching agents, sodium perborate tetrahydrate and sodium perborate monohydrate are particularly important. Other useful bleaching agents are, for example, sodium percarbonate, peroxypyrophosphates, citrate perhydrates and H202-yielding peracidic salts or peracids, such as perbenzoates, peroxophthalates, diperazelaic acid, phthaloiminoperacid or diperdodecanedioic acid. Cleaning compositions according to the invention may also contain bleaching agents from the group of organic bleaching agents. Typical organic bleaching agents are diacyl peroxides, such as dibenzoyl peroxide for example. Other typical organic bleaching agents are the peroxy acids, of which alkyl peroxy acids and aryl peroxy acids are particularly mentioned as examples. Preferred representatives are (a) peroxybenzoic acid and ring-substituted derivatives thereof, such as alkyl peroxybenzoic acids, but also peroxy-a-naphthoic acid and magnesium monoperphthalate, (b) aliphatic or substituted aliphatic peroxy acids, such as peroxylauric acid, peroxystearic acid, s-phthalimidoperoxycaproic acid [phthaoiminoperoxyhexanoic acid (PAP)j, o-carboxybenzamidoperoxycaproic acid, N-nonenylamidoperadipic acid and N-nonenylamidopersuccinates, and (c) aliphatic and araliphatic peroxydicarboxylic acids, such as 1,12-diperoxycarboxylic acid, 1,9-diperoxyazelaic acid, diperoxysebacic acid, diperoxybrassylic acid, diperoxyphthalic acids, 2-decyldiperoxybutane-1,4-dioic acid, N,N-terephthaloyl-di(6-aminopercaproic acid).
Other suitable bleaching agents in the effervescent tablets according to the invention are chlorine- and bromine-releasing substances. Suitable chlorine- or bromine-releasing materials are, for example, heterocyclic N-bromamides and N-chloramides, for example trichloroisocyanuric acid, tribromoisocyanuric acid, dibromoisocyanuric acid andlor dichloro-isocyanuric acid (DICA) andlor salts thereof with cations, such as potassium and sodium. Hydantoin compounds, such as 1,3-dichloro-5,5-dimethyl hydantoin, are also suitable.
Bleach activators which support the effect of the bleaching agents can also be part of the effervescent tablets. Known bleach activators are compounds which contain one or more N- or O-acyl groups, such as substances from the class of anhydrides, esters, imides and acylated imidazoles or oximes. Examples are tetraacetyl ethylenediamine (TAED), tetraacetyl methylenediamine (TAMD) and tetraacetyl hexylenediamine (TAHD) and also pentaacetyl glucose (PAG), 1,5-diacetyl-2,2-dioxohexaydro-1,3,5-triazine (DADHT) and isatoic anhydride (ISA).
In addition to or instead of the conventional bleach activators mentioned above, so-called bleach catalysts may also be incorporated in the effervescent tablets. These substances are bleach-boosting transition metal salts or transition metal complexes such as, for example, manganese-, iron-, cobalt-, ruthenium- or molybdenum-salen or -carbonyl complexes. Manganese, iron, cobalt, ruthenium, molybdenum, titanium, vanadium and copper complexes with nitrogen-containing tripod ligands and cobalt-, iron-, copper- and ruthenium-ammine complexes may also be used as bleach catalysts.
The effervescent tablets may of course also contain enzymes.
Suitable enzymes in the basic tablets are, in particular, those from the classes of hydrolases, such as proteases, esterases, lipases or lipolytic enzymes, amylases, glycosyl hydrolases and mixtures thereof. All these hydrolases contribute to the removal of stains, such as protein-containing, fat-containing or starch-containing stains. Oxidoreductases may also be used for bleaching. Enzymes obtained from bacterial strains or fungi, such as Bacillus subtilis, Bacillus licheniformis, Streptomyces griseus, Coprinus cinereus and Humicola insolens and from genetically modified variants are particularly suitable. Proteases of the subtilisin type are preferably used, proteases obtained from Bacillus lentus being particularly preferred. Of particular interest in this regard are enzyme mixtures, for example of protease and amylase or protease and lipase or lipolytic enzymes or of protease, amylase and lipase or lipolytic enzymes or protease, lipase or lipolytic enzymes, but especially protease- andlor lipase-containing mixtures or mixtures with lipolytic enzymes. Examples of such lipolytic enzymes are the known cutinases. Peroxidases or oxidases have also been successfully used in some cases. Suitable amylases include in particular a-amylases, isoamylases, pullanases and pectinases. The enzymes may be adsorbed to supports or encapsulated in membrane materials to protect them against premature decomposition.
Dyes and perfumes may be added to the effervescent tablets according to the invention in order to improve the aesthetic impression created by the products and to provide the consumer not only with the required performance but also with a visually and sensorially "typical and unmistakable" product. Suitable perfume oils or perfumes include individual perfume compounds, for example synthetic products of the ester, ether, aldehyde, ketone, alcohol and hydrocarbon type. Perfume com-pounds of the ester type are, for example, benzyl acetate, phenoxyethyl isobutyrate, p-tert.butyl cyclohexyl acetate, linalyl acetate, dimethyl benzyl carbinyl acetate, phenyl ethyl acetate, linalyl benzoate, benzyl formate, ethyl methyl phenyl glycinate, allyl cyclohexyl propionate, styrallyl propionate and benzyl salicylate. The ethers include, for example, benzyl ethyl ether; the aldehydes include, for example, the linear alkanals containing 8 to 18 carbon atoms, citral, citronellal, citronellyloxyacetal-dehyde, cyclamen aldehyde, hydroxycitronellal, lilial and bourgeonal; the ketones include, for example, the ionones, a-isomethyl ionone and methyl cedryl ketone; the alcohols include anethol, citronellol, eugenol, geraniol, linalool, phenyl ethyl alcohol and terpineol and the hydrocarbons include, above all, the terpenes, such as limonene and pinene. However, mixtures of various perfumes which together produce an attractive perfume note are preferably used. Perfume oils such as these may also contain natural perfume mixtures obtainable from vegetable sources, for example pine, citrus, jasmine, patchouli, rose or ylang-ylang oil. Also suitable are clary oil, camomile oil, clove oil, melissa oil, mint oil, cinnamon leaf oil, lime blossom oil, juniper berry oil, vetiver oil, olibanum oil, galbanum oil and labdanum oil and orange blossom oil, neroli oil, orange peel oil and sandalwood oil. In order to improve their aesthetic impression, the tablets according to the invention (or parts thereof) may be colored with suitable dyes. Preferred dyes, which are not difficult for the expert to choose, have high stability in storage, are not affected by the other ingredients of the tablets or by light and do not have any pronounced substantivity for the substrates treated with the tablets, such as glass, ceramics or plastic tableware, so as not to color them.
To protect the tableware or the machine itself, the effervescent tablets according to the invention may contain corrosion inhibitors, especially in the basic powder, silver protectors being particularly important for dishwashing machines. Known corrosion inhibitors may be used.
Above all, silver protectors selected from the group of triazoles, benzotriazoles, bisbenzotriazoles, aminotriazoles, alkylaminotriazoles and the transition metal salts or complexes may generally be used.
Benzotriazole andlor alkylaminotriazole islare particularly preferred. In addition, dishwashing formulations often contain corrosion inhibitors containing active chlorine which are capable of distinctly reducing the corrosion of silver surfaces. Chlorine-free dishwashing detergents contain in particular oxygen- and nitrogen-containing organic redox-active compounds, such as dihydric and trihydric phenols, for example hydroquinone, pyrocatechol, hydroxyhydroquinone, gallic acid, phloro-glucinol, pyrogallol and derivatives of these compounds. Salt-like and complex-like inorganic compounds, such as salts of the metals Mn, Ti, Zr, Hf, V, Co and Ce are also frequently used. Of these, the transition metal salts selected from the group of manganese andlor cobalt salts and/or complexes are preferred, cobalt(ammine) complexes, cobalt(acetate) complexes, cobalt(carbonyl) complexes, chlorides of cobalt or manganese and manganese sulfate being particularly preferred. Zinc compounds may 5 also be used to prevent corrosion of tableware.
The effervescent tablets according to the invention may be obtained by tabletting particulate premixes in known manner. Accordingly, the present invention also relates to a process for the production of effervescent tablets by tabletting a particulate premix in known manner, 10 characterized in that one or more water-soluble substances with a melting point between 40 and 100°C islare applied in the form of a melt to the remaining particulate ingredients of the premix and the premix as a whole is then tabletted.
To produce the tablettable premixes, the solid ingredients are 15 introduced into a mixer and the tabletting aid is then added in the form of a melt. After leaving the mixer, the mixture may be tabletted. What was said in the foregoing in regard to preferred embodiments of the effervescent tablets according to the invention also applies to preferred embodiments of the process according to the invention (preferred tabletting aids, quantities 20 of substances used, etc.). In particularly preferred processes according to the invention, one or more substances from the group of polyethylene glycols, alcohol alkoxylates, glycerol mono- and difatty acid esters, di-, tri-and polyols, carboxylic acids, lactams and ammonium phosphates islare applied in quantities of 2 to 20% by weight, preferably in quantities of 3 to 25 17.5% by weight, more preferably in quantities of 4 to 15% by weight and most preferably in quantities of 5 to 12.5% by weight, based on the weight of the premix.
The present invention also relates to the use of 1,10-decanediol, trimethylol propane, s-caprolactam, glutaric acid, sodium ammonium hydrogen phosphate tetrahydrate ("phosphorus salt") or glycerol mono- or difatty acid esters for improving the tablettability and the hardness and abrasion stability of tablets, preferably effervescent tablets. The novel use of these substances leads to advantages in regard to the tablettability and the physical properties of the tablets, as the following Examples which are not to be construed as limiting, show.
Examples Effervescent tablet formulations E1 to E4 were prepared by applying a melt of the tabletting aid to a mixture of the other ingredients. In Comparison Example C, the tabletting aid used had too high a melting point and was added in very fine-particle form.

Amidosulfonic acid 65.0 65.0 65.0 65.0 65.0 Sodium carbonate, calcined 20.0 20.0 20.0 20.0 20.0 Citric acid, water-free 5.0 5.0 5.0 5.0 5.0 Caprolactam 10.0 - - - -1,10-Decanediol - 10.0 - - -Glutaric acid - - 10.0 - -Trimethylol propane - - - 10.0 -Maleic acid - - - - 10.0 Whereas premixes E1 to E4 were free-flowing and readily tablettable, premix C was difficult to dose and led to tablets with poor edge stability and initial hardnesses below 70 N. The initial hardnesses of the tablets produced from E1 to E4 were above 100 N.

Claims (24)

1. Effervescent tablets containing one or more organic acids, one or more substances selected from the group consisting of carbonates and/or hydrogen carbonates and optionally other ingredients of detergents, wherein said tablets contain 2 to 20% by weight, based on tablet weight, of one or more water-soluble substances with a melting point between 40 and 100°C.

2. Effervescent tablets as claimed in claim 1, containing 2 to 20% by weight, based on tablet weight, of one or more substances selected from the group consisting of polyethylene glycols, alcohol alkoxylates, glycerol mono- and difatty acid esters, di-, tri- and polyols, carboxylic acids, lactams and ammonium phosphates as the water-soluble substances with a melting point between 40 and 100°C.

3. Effervescent tablets as claimed in claim 2, wherein the water-soluble substances with a melting point between 40 and 100°C are present in the amount of 3 to 17.5% by weight.

4. Effervescent tablets as claimed in claim 3, wherein the water-soluble substances with a melting point between 40 and 100°C are present in the amount of 4 to 15% by weight.

5. Effervescent tablets as claimed in claim 4, wherein the water-soluble substances with a melting point between 40 and 100°C are present in the amount of 5 to 12.5% by weight.

6. Effervescent tablets as claimed in any one of claims 1 to 5, containing one or more substances selected from the group consisting of 1,10-decanediol, trimethylol propane, .epsilon.-caprolactam, glutaric acid and sodium ammonium hydrogen phosphate tetrahydrate ("phosphorus salt") in quantities of 2.5 to 18% by weight, based on the weight of the effervescent tablet, as the water-soluble substances with a melting point between 40 and 100°C.

7. Effervescent tablets as claimed in claim 6, wherein the water-soluble substances with a melting point between 40 and 100°C are present in the amount of 6 to 16% by weight

8. Effervescent tablets as claimed in claim 7, wherein the water-soluble substances with a melting point between 40 and 100°C are present in the amount of 8 to 11 % by weight

9. Effervescent tablets as claimed in any one of claims 1 to 8, containing one or more substances corresponding to general formula I, II, in which the substituents R1 and R2 independently of one another are selected from saturated, mono- or diunsaturated acyl groups containing 12 to 22 as the water-soluble substances with a melting point between 40 and 100°C.

10. Effervescent tablets as claimed in claim 9, wherein R1 and R2 independently of one another are selected from saturated, mono- or diunsaturated acyl groups containing 14 to 20 carbon atoms.

11. Effervescent tablets as claimed in claim 10, wherein R1 and R2 independently of one another are selected from saturated, mono- or diunsaturated acyl groups containing 16 to 18 carbon atoms.

12. Effervescent tablets as claimed in claim 10, wherein R1 and R2 are each glycerol monostearate.

13. Effervescent tablets as claimed in any one of claims 1 to 12, containing 10 to 80% by weight of one or more organic acids selected from the group consisting of adipic acid, amidosulfonic acid, succinic acid, citric acid, fumaric acid, malefic acid, malonic acid, oxalic acid and tartaric acid.

14. Effervescent tablets as claimed in claim 13, wherein said organic acid(s) is present in the amount of 20 to 75% by weight.

15. Effervescent tablets as claimed in claim 14, wherein said organic acid(s) is present in the amount of 30 to 70% by weight.

16. Effervescent tablets as claimed in any of claims 1 to 15, containing more than 40% by weight, based on tablet weight, of amidosulfonic acid.

17. Effervescent tablets as claimed in claim 16, containing more than 50% by weight, based on tablet weight, of amidosulfonic acid.

18 Effervescent tablets as claimed in claim 17, containing more than 60% by weight, based on tablet weight, of amidosulfonic acid.

19. Effervescent tablets as claimed in any one of claims 1 to 18, containing 5 to 30% by weight, based on tablet weight, of alkali metal carbonates and/or hydrogen carbonates.

20. Effervescent tablets as claimed in claim 19, containing 10 to 25% by weight, based on tablet weight, of alkali metal carbonates and/or hydrogen carbonates.

21. Effervescent tablets as claimed in claim 20, containing 12.5 to 20%
by weight, based on tablet weight, of alkali metal carbonates and/or hydrogen carbonates.

22. Effervescent tablets as claimed in any one of claims 19 to 21, wherein said carbonate is sodium carbonate.

23. Effervescent tablets as claimed in any one of claims 1 to 22, additionally containing one or more substances selected from the groups consisting of builders, complexing agents, bleaching agents, bleach activators, enzymes, dyes and perfumes.

24. A process for the production of effervescent tablets by tabletting a particulate premix in known manner, wherein one or more water-soluble substances with a melting point between 40 and 100°C is/are applied in the form of a melt to the remaining particulate ingredients of the premix and the premix as a whole is then tabletted.