CA2311482A1 - Storage-stable effervescent tablets - Google Patents

Abstract

Storage-stable effervescent tablets comprise one or more organic acids, one or more substances from the group of the carbonates and/or hydrogen carbonates, and, if desired, further ingredients of laundry detergents and cleaning products and comprises as stability enhancer, based on the tablet weight, from 2 to 20% by weight of one or more substances having a water absorption level of less than 0.5 g of water per 1 g of substance, the water absorption level of the substance being measured during one week of open storage at 30°C and 80% relative atmospheric humidity.

Description

"Storage-stable effervescent tablets"
Field of the Invention The present invention is situated in the field of compact tablets having detersive properties. The invention relates in particular to tablets comprising a so-called effervescent system, and among these relates in particular to descaler tablets.
Background of the Invention Laundry detergent and cleaning product tablets have been described widely in the prior art and are enjoying increasing popularity with users owing to the ease of dosing. Tableted laundry detergents and cleaning products have a number of advantages over their powder counterparts: they are easier to dose and to handle and have storage and transport advantages owing to their compact structure. Consequently, laundry detergent and cleaning product tablets have also been described extensively in the patent literature. One problem which occurs again and again, especially with tablets containing effervescent systems, is the inadequate storage stability, since the tablets tend to absorb moisture from the air and, on so doing, to break down to a greater or lesser extent. To date, therefore, effervescent tablets have been packaged in airtight packs immediately following their production or have been produced at great technical expense from anhydrous substances, whereas the use of standard industrial grades would be more economic.
Effervescent tablets have been widely described in the prior art, since the incorporation of gas-evolving systems often leads to better disintegration times and dissolution times.
For instance, International Patent Application WO 97/43366 (Procter & Gamble) describes a laundry CA 02311482 2000-06-12' detergent composition having improved dispensability, also in the form of a laundry detergent piece or a tablet, which comprises from 0.5 to 60% by weight of anionic surfactant, from 0.01 to 30% by weight of cationic surfactant, and an effervescent system comprising acid and alkali. This document mentions neither the problem of inadequate storage stability, nor descaler tablets.
International Patent Application WO 87/02052 (Ockhuizen et al.) describes a laundry detergent and cleaning product in the form of an effervescent tablet which comprises from 2 to 6% by weight of a laundry detergent concentrate, from 40 to 60% by weight of hydrogen carbonate, from 33 to 53% by weight of a solid organic acid (in particular a 2:3 mixture of citric acid and tartaric acid), from 1.5 to 2.5% by weight of binder (PVP), from 0.1 to 1% by weight of lubricant, plus additional amounts of colloidal silica. Here again, neither storage stability nor descaler tablets are mentioned.
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, consisting of at least one active substance or active substance combination, at least one binder, optionally excipients such as aromas, colorants, fragrances, plasticizers, bleaches and effervescent additives, the binder used being propylene glycol or glycerol. Likewise claimed is a process for producing these effervescent tablets.
British Patent Application GB 2 096 162 (Warner-Lambert) describes an effervescent tablet comprising from 35 to 60% by weight of monopersulfate, up to 20%
by weight of alkaline earth) metal halide, from 0.5 to 20% by weight of perborate, from 0.15 to 0.5% by weight of colorant, and also potassium iodide and/or potassium bromide as indicator substances.
A fragranced effervescent tablet further comprising sorbitol as carrier material and also carbonate and/or bicarbonate and an organic acid as gas-evolving system is disclosed in German Patent Application DE 4 133 862 (Henkel) .
It is an object of the present invention to minimize the problems depicted in connection with effervescent tablets. For effervescent tablets which are not to be produced from completely anhydrous raw materials, in particular, the intention was to discover formulation alternatives which provide tablets featuring high storage stability and the possibility of doing away with packaging. For this purpose, certain substances have proven particularly suitable.
Description of the Invention The present invention provides effervescent tablets comprising one or more organic acids, one or more substances from the group of the carbonates and/or hydrogen carbonates, and, if desired, further ingredients of laundry detergents and cleaning products, and as stability enhancer, based on the tablet weight, from 2 to 20% by weight of one or more substances having a water absorption level of less than 0.5 g of water per g of substance, the water absorption level of the substance being measured during one week of open storage at 30°C and 80% relative atmospheric humidity.
The water absorption levels of the substances added to the effervescent tablets in the context of the present invention may be determined experimentally by one-week open storage of a weighed amount of the substance at 30°C and 80% relative atmospheric humidity, subsequent . 4 weighing, and calculation of the difference in the mass values. The water absorption levels are stated in grams of weight increase (water absorption) per gram of substance.
In the context of the present invention it is not only preferred for the stability enhancers to possess a low water absorption capacity; rather, it is additionally preferred to use substances which in addition have a high water binding capacity. The water binding capacity is the ability of a substance to absorb water in chemically stable form, and ultimately indicates the amount of water which can be bound in the form of stable hydrates of a substance. The dimensionless value of the water binding capacity (WBC) is calculated from:
n~18 WBC = , M
where n is the number of water molecules in the corresponding hydrate of the substance and M is the molar mass of the unhydrated substance. For the water binding capacity of anhydrous sodium carbonate (formation of sodium carbonate monohydrate), for example, this gives a value of WBC = - 0.17.
223+12+316 In preferred effervescent tablets, the substances) present in the tablets, with a water absorption level of less than 0.5 g of water per g of substance, has/have a water binding capacity of more than 0.1 g of water per g of substance.
In preferred embodiments of the present invention, the two parameters of water absorption capacity and water binding capacity are not viewed in isolation from one another. In particular it is preferred to use substances governed by the following relationship:
water absorption capacity Lin g per g of substances -water binding capacity < 0.1 In effervescent tablets which are preferred in the context of the present invention, for the substances) present in the tablets and having a water absorption level of less than 0.5 g of water per g of substance, the difference between the value of the water absorption capacity (stated in grams per gram of substance) and the water binding capacity is less than 0.1, preferably less than 0.05, with particular preference less than 0.01, and in particular less than 0.
In other words, in particularly preferred embodiments of the present invention, for the stability enhancers present in accordance with the invention in the effervescent tablets, the water binding capacity should always be greater than the water absorption capacity.
Suitable stability enhancers include a range of substances, which are required primarily to satisfy the criterion "water absorption level < 0.5 g per g of substance". In addition to carbonates, especially sodium carbonate (water absorption capacity 0.39 g per g), examples of suitable stability enhancers include phosphates, especially sodium tripolyphosphate (water absorption capacity 0.2 g per g). sulfates, especially sodium sulfate (water absorption capacity 0 g per g), citrates, especially sodium citrate (water absorption capacity 0 g per g), and hydrogen carbonates, especially sodium hydrogen carbonate (water absorption capacity 0 g per g).

Particularly preferred stability enhancers further satisfy the criterion "water binding capacity > 0.1".
Suitable substances here are again the phosphates, especially sodium tripolyphosphate (water binding capacity 0.29), sulfates, especially sodium sulfate (water binding capacity 1.27), and citrates, especially sodium citrate (water binding capacity 0.138).
In the particularly preferred effervescent tablets of the invention, the stability enhancers used satisfy the abovementioned mathematical relationship "water absorption capacity (in g per g of substance] - water binding capacity < 0.1, preferably < 0.05, with particular preference < 0.01, and in particular < 0".
With the abovementioned values, particularly preferred stability enhancers are found to be, in particular, hydrogen carbonates, especially sodium hydrogen carbonate (WAC - WBC = 0 - 0 - 0), phosphates, especially sodium tripolyphosphate (WAC - WBC = 0.2 -0.29 = -0.09), citrates, especially trisodium citrate (WAC - WBC = 0 - 0.138 = -0.138), and sulfates, especially sodium sulfate (WAC - WBC = 0 - 1.27 =
-1.27) .
Particularly preferred effervescent tablets comprise as stability enhancer from 2 to 20% by weight, preferably from 3 to 15% by weight, and in particular from 4 to 10% by weight, of phosphate(s), preferably alkali metal phosphate(s), with particular preference pentasodium and/or pentapotassium triphosphate (sodium and/or potassium tripolyphosphate).
Among the large number of commercially available phosphates, the alkali metal phosphates, with particular preference pentasodium and/or pentapotassium triphosphate (sodium and potassium tripolyphosphate, respectively), are of the greatest importance in the laundry detergents and cleaning products industry.

_ 7 Alkali metal phosphates is an umbrella term for the alkali metal (especially sodium and potassium) salts of the various phosphoric acids, among which meta-phosphoric acids (HP03)n and orthophosphoric acid H3P04 may be distinguished alongside higher molecular mass representatives. The phosphates combine a plurality of advantages: they act as alkali metal carriers, prevent lime deposits on machine components and lime incrustations in fabrics, and, furthermore, contribute to the cleaning performance.
Sodium dihydrogen phosphate, NaHzP04, exists as the dehydrate (density 1.91 g cm-3, melting point 60°) and as the monohydrate (density 2.04 g cm-3). Both salts are white powders, very readily soluble in water, which lose the water of crystallization on heating and undergo transition at 200°C into the weakly acidic diphosphate (disodium dihydrogen diphosphate, Na2H2P207) , and at higher temperature into sodium trimetaphosphate (Na3P309) and Maddrell's salt (see below) . NaH2P04 reacts acidically; it is formed when phosphoric acid is adjusted to a pH of 4.5 using sodium hydroxide solution and the slurry is sprayed. Potassium dihydrogen phosphate (primary or monobasic potassium phosphate, potassium biphosphate, PDP), KHzP04, is a white salt of density 2.33 g cm-3, 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, crystalline salt which dissolves very readily in water. It exists in anhydrous form and with 2 mol (density 2.066 g cm-3, water loss at 95°). 7 mol, (density 1.68 g cm-3, melting point 48°C with loss of 5 H20), and 12 mol of water (density 1.52 g cm~3, melting point 35° with loss of 5 Hz0), becomes anhydrous at 100°, and on more severe _ 8 heating undergoes transition to the diphosphate Na4P20~.
Disodium hydrogen phosphate is prepared by neutralizing phosphoric acid with sodium carbonate solution using phenolphthalein as indicator. Dipotassium hydrogen phosphate (secondary or dibasic potassium phosphate), K2HP04, is an amorphous white salt which is ready soluble in water.
Trisodium phosphate, tertiary sodium phosphate, Na3P04, comprises colorless crystals which as the dodecahydrate have a density of 1.62 g cm-3 and a melting point of 73-76°C (decomposition), as the decahydrate (corresponding to 19-20% P205) have a melting point of 100°C, and in anhydrous form (corresponding to 39-40%
Pz05) have a density of 2.536 g cm-3. Trisodium phosphate is readily soluble in water with an alkaline reaction and is prepared by evaporative concentration of a solution of precisely 1 mol of disodium phosphate and 1 mol of NaOH. Tripotassium phosphate (tertiary or tribasic potassium phosphate), K3P04, is a white, deliquescent, granular powder of density 2.56 g cm-3, has a melting point of 1340° and is readily soluble in water with an alkaline reaction. It is formed, for example, on heating Thomas slag with charcoal and potassium sulfate. Despite the higher price, the cleaning products industry often prefers the more readily soluble and hence highly active potassium phosphates over corresponding sodium compounds.
Tetrasodium diphosphate (sodium pyrophosphate), Na4P20~, exists in anhydrous form (density 2.534 g cm-3, melting point 988°, 880° also reported) and as the decahydrate (density 1.815-1.836 g cm-3, melting point 94° with loss of water). Both substances are colorless crystals which dissolve in water with an alkaline reaction. Na4Pz0, is formed when disodium phosphate is heated at >200°C or by reacting phosphoric acid with sodium carbonate in a stoichiometric ratio and dewatering the solution by spraying. The decahydrate complex is heavy metal salts heating undergoes transition to the diphosphate Na4P20,.
Disodium hydrogen phosphate is prepared by neutralizing phosphoric acid with sodium carbonate solution using phenolphthalein as indicator. Dipotassium hydrogen phosphate (secondary or dibasic potassium phosphate), K2HP04, is an amorphous white salt which is ready soluble in water.
Trisodium phosphate, tertiary sodium phosphate, Na3P04, comprises colorless crystals which as the dodecahydrate have a density of 1.62 g cm-3 and a melting point of 73-76°C (decomposition), as the decahydrate (corresponding to 19-20% P205) have a melting point of 100°C, and in anhydrous form (corresponding to 39-40%
P205) have a density of 2.536 g cm-3. Trisodium phosphate is readily soluble in water with an alkaline reaction and is prepared by evaporative concentration of a solution of precisely 1 mol of disodium phosphate and 1 mol of NaOH. Tripotassium phosphate (tertiary or tribasic potassium phosphate), K3P04, is a white, deliquescent, granular powder of density 2.56 g cm-3, has a melting point of 1340° and is readily soluble in water with an alkaline reaction. It is formed, for example, on heating Thomas slag with charcoal and potassium sulfate. Despite the higher price, the cleaning products industry often prefers the more readily soluble and hence highly active potassium phosphates over corresponding sodium compounds.
Tetrasodium diphosphate (sodium pyrophosphate), Na4P20~, exists in anhydrous form (density 2.534 g cm-3, melting point 988°, 880° also reported) and as the decahydrate (density 1.815-1.836 g cm-3, melting point 94° with loss of water). Both substances are colorless crystals which dissolve in water with an alkaline reaction. Na4P20., is formed when disodium phosphate is heated at >200°C or by reacting phosphoric acid with sodium carbonate in a stoichiometric ratio and dewatering the solution by spraying. The decahydrate complex is heavy metal salts and water hardeners and therefore reduces the hardness of water. Potassium diphosphate (potassium pyro-phosphate), K4Pz0." exists in the form of the trihydrate and is a colorless, hygroscopic powder of density 2.33 g cm-3 which is soluble in water, the pH of the 1%
strength solution at 25° being 10.4.
Condensation of NaH2P04, and, respectively, of KH2P04 produces higher molecular mass sodium and potassium phosphates, among which cyclic representatives, the sodium and potassium metaphosphates, and catenated types, the sodium and potassium polyphosphates, may be distinguished. For the latter in particular a large number of designations are in use: fused or calcined phosphates, Graham's salt, Kurrol's salt and Maddrell's salt. All higher sodium and potassium phosphates are referred to collectively as condensed phosphates.
The industrially important pentasodium triphosphate Na5P301o (sodium tripolyphosphate) is a nonhygroscopic, white, water-soluble salt which crystallizes in anhydrous form or with 6 H20 and has the general formula Na0- [P (O) (ONa) -O] n-Na where n=3 . About 17 g of the water-of-crystallization-free salt dissolve in 100 g of water at room temperature; at 60° about 20 g, and at 100° around 32 g; after two hours of heating of the solution at 100°, hydrolysis produces about 8%
orthophosphate and 15% diphosphate. In the preparation of pentasodium triphosphate, phosphoric acid is reacted in stoichiometric ratio with sodium carbonate solution or sodium hydroxide solution and the solution is dewatered by spraying. Similarly to Graham's salt and sodium diphosphate, pentasodium triphosphate dissolves many insoluble metal compounds (including lime soaps, etc . ) . Pentapotassium triphosphate, KSP301o (Potassium tripolyphosphate), is commercialized, for example, in the form of a 50% strength by weight solution (> 23%
P205, 25% K20) . The potassium polyphosphates find broad application in the laundry detergents and cleaning products industry. Furthermore, there are also sodium potassium tripolyphosphates in existence, which may likewise be used in the context of the present invention. These are formed, for example, when sodium trimetaphosphate is hydrolyzed with KOH:
(NaP03) 3 + 2 KOH ~ Na3K2P301o + H20.
They can be used in accordance with the invention in exactly the same way as sodium tripolyphosphate, potassium tripolyphosphate or mixtures of these two; in addition, mixtures of sodium tripolyphosphate and sodium potassium tripolyphosphate, or mixtures of potassium tripolyphosphate and sodium potassium tripolyphosphate, or mixtures of sodium tripoly-phosphate and potassium tripolyphosphate and sodium potassium tripolyphosphate, may be used in accordance with the invention.
In addition to the stability enhancers, the effervescent tablets of the invention comprise a gas-releasing system comprising organic acids and carbonates/hydrogen carbonates.
Organic acids which release carbon dioxide from the carbonates/hydrogen carbonates in aqueous solution and may be used are, for example, the solid mono-, oligo-and polycarboxylic acids. Among this group, preference is given in turn to citric acid, tartaric acid, succinic acid, malonic acid, adipic acid, malefic acid, fumaric acid, oxalic acid, and also polyacrylic acid.
Organic sulfonic acids such as amidosulfonic acid may likewise be used. Commercially available and likewise suitable for use with preference as an acidifier in the context of the present invention is Sokalan~ DCS
(trademark of BASF), a mixture of succinic acid (max.
31% by weight), glutaric acid (max. 50°s by weight), and adipic acid (max. 33% by weight). Effervescent tablets containing from 10 to 80% by weight, preferably from 20 to 75% by weight, and in particular from 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, are preferred in accordance with the invention.
The abovementioned acids need not be used stoichio-metrically to the carbonates and/or hydrogen carbonates that are present in the tablets. In the light of the preferred field of use of the effervescent tablets of the invention as limescale remover tablets, indeed, it is often desirable to use the acids) in excess.
Particular preference is given in this case, owing to its good limescale removal action, to amidosulfonic acid. Amidosulfonic acid, which is often also referred to as amidosulfuric acid or sulfamic acid, is commercialized in the form of colorless, odorless, nonflammable, nonhygroscopic, nonvolatile, orthorhombic crystals and is obtained industrially from urea, sulfur trioxide and sulfuric acid or from ammonia and sulfur trioxide.
An effervescent tablet which is preferred in the context of the present invention comprises, based on the tablet weight, more than 40% by weight, preferably more than 50% by weight, and in particular more than 60% by weight, of amidosulfonic acid.
In addition to said organic acids, the gas-evolving effervescent system in the effervescent tablets of the invention consists of carbonates and/or hydrogen carbonates. Among the representatives of this class of substance, the alkali metal salts are distinctly preferred on grounds of cost. In the case of the alkali metal carbonates and hydrogen carbonates, in turn, the sodium and potassium salts are distinctly preferred over the other salts on grounds of cost. Of course, it is not necessary to use the relevant single alkali metal carbonates or hydrogen carbonates; rather, mixtures of different carbonates and hydrogen carbonates may be preferable.
Sodium carbonate forms a white powder of density 2.532 g cm-3, a distinction being made between light calcined soda with a bulk density of 0.5-0.55 kg/1 and heavy calcined soda at 1.0-1.1 kg/1. With water, sodium carbonate forms three hydrates: sodium carbonate decahydrate (crystal soda), Na2C03-lOHzO, colorless, monoclinic crystals of icelike appearance with a density of 1.44 g cm-3, melting point 32-34°; sodium carbonate heptahydrate, Na2C03-7H20, rhombic crystals of density 1.51 g cm-3, melting point 32-35°; and sodium carbonate monohydrate, Na2C03-H20, rhombic crystals of density 2.25 g cm-3, melting point 100°.
Sodium hydrogen carbonate is a white odorless powder (monoclinic crystals) with an alkaline taste which is stable in dry air, has the density of 2.159 g cm-3, and on heating to above 65° breaks down into CO2, H20 and sodium carbonate.
Potassium carbonate (potash) is a white, nontoxic, hygroscopic powder of density 2.428 g cm-3 which forms various hydrates. If a large amount of carbon dioxide is passed into concentrated potassium carbonate solution, the less readily soluble potassium hydrogen carbonate is precipitated. Otherwise, the properties of potassium carbonate show great similarity with those of the closely related sodium carbonate. Potassium carbonate 1,5-hydrate ("potash hydrate") is the stable phase of potassium carbonate in contact with the saturated solution in the range from 0°C up to about 110°C, and may be obtained by crystallization from supersaturated potassium carbonate solutions. It crystallizes in glassy, virtually dust-free crystals, has a density of 2.155 g cm-3, and loses its water of crystallization entirely at temperatures from 130 to 160°C. The majority of industrial production processes for potassium carbonate lead initially to potassium carbonate 1,5-hydrate, which is calcined in rotary tube furnaces at from 200 to 350°C to give potassium carbonate with a purity of 98 to 100%. Without this calcining, the crystallized potassium carbonate 1,5-hydrate is dried at from 110 to 120°C and sold as potash hydrate. Examples of industrially practiced production processes for the abovementioned products are the continuous crystallization process (starting materials: KOH and C02), the fluid bed process (starting materials: KOH and C02), the amine process (KOH/COz in the presence of isopropylamine: Mines de Potasse d'Alsace, or KOH/COZ in the presence of triethylamine:
Kali-Chemie AG) or the nepheline digestion process (primarily former USSR). Of minor importance, or now only of historical interest, are the ion exchanger process (starting materials: KC1 and (NH4)ZC03), the magnesia process (Engel-Precht process, Neustai3furter process; starting materials: KC1, MgC03~3H20 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).
Also possible for use as the second component of the effervescent system, in accordance with the invention, is trona, a mixed salt of sodium carbonate and sodium hydrogen carbonate that is also known as sodium sesquicarbonate or sodium carbonate sesquihydrate.
Sodium cabonate sesquihydrate occurs in nature as a mineral (trona) and is described by the formula NazC03 ~ NaHC03 ~ 2H20. Maj or deposits of trona are located, for example, in the USA (Green River, Wyoming), Kenya (Lake Magadi), and the Republic of Sudan (Dongola).
Whereas the deposits in Africa can be worked in open mining, the trona in the USA is obtained by underground mining. Trona has a density of 2.17 g cm-3 and a Mohs hardness of 2.5. Trona is normally used to obtain pure sodium carbonate; by the sodium sesquicarbonate process, however, it is also possible to produce pure Na2C03 ~ NaHC03 ~ 2H20, which passes into commerce . Pure sodium sesequicarbonate is also formed from sodium hydrogen carbonate left to stand in humid air, with elimination of carbon dioxide, or by introducing carbon dioxide into a solution of sodium carbonate.
In preferred effervescent tablets, based on the tablet weight, from 5 to 30% by weight, preferably from 10 to 25% by weight, and in particular from 12.5 to 20% by weight, of alkali metal carbonates and/or hydrogen carbonates are used, sodium carbonate being preferred.
In addition to the effervescent system, the additional organic acids, and the stability enhancers, the effervescent tablets of the invention may include further important ingredients of cleaning products, especially builders. Effervescent tablets of the invention further comprising one or more substances from the groups of the builders, complexing agents, bleaches, bleach activators, enzymes, dyes, and fragrances are preferred.
Builders that may be present in the effervescent tablets of the invention are all those commonly used in laundry detergents and cleaning products, i.e., in particular, zeolites, silicates, and organic cobuilders.
Suitable crystalline, layered sodium silicates possess the general formula NaMSiXO2X+uYHz~, where M is sodium or hydrogen, x is a number from 1.9 to 4, y is a number from 0 to 20, and preferred values for x are 2, 3 or 4.
Crystalline phyllosilicates of this kind are described, for example, in European Patent Application EP-A-0 164 514. Preferred crystalline phyllosilicates of the formula indicated are those in which M is sodium and x adopts the value 2 or 3. In particular, both ~i-and 8-sodium disilicates Na2SizO5~yH20 are preferred, (3-sodium disilicate, for example, being obtainable by the process described in International Patent Application WO-A-91/08171.
It is also possible to use amorphous sodium silicates having an NazO:SiOa modulus of from 1:2 to 1:3.3, preferably from 1:2 to 1:2.8, and in particular from 1:2 to 1:2.6, which are dissolution-retarded and have secondary washing properties. The retardation of dissolution relative to conventional amorphous sodium silicates may have been brought about in a variety of ways - for example, by surface treatment, compounding, compacting, or overdrying. In the context of this invention, the term "amorphous" also embraces "X-ray-amorphous". This means that in X-ray diffraction experiments the silicates do not yield the sharp X-ray reflections typical of crystalline substances but instead yield at best one or more maxima of the scattered X-radiation, having a width of several degree units of the diffraction angle. However, good builder properties may result, even particularly good builder properties, if the silicate particles in electron diffraction experiments yield vague or even sharp diffraction maxima. The interpretation of this is that the products have microcrystalline regions with a size of from 10 to several hundred nm, values up to max.
50 nm and in particular up to max. 20 nm being preferred. So-called X-ray-amorphous silicates of this kind, which likewise possess retarded dissolution relative to the conventional waterglasses, are ~ 16 described, for example, in German Patent Application DE-A-44 00 024. Particular preference is given to compacted amorphous silicates, compounded amorphous silicates, and overdried X-ray-amorphous silicates.
The finely crystalline, synthetic zeolite used, containing bound water, is preferably zeolite A
and/or P. A particularly preferred zeolite P is Zeolite MAP~ (commercial product from Crosfield). Also suitable, however, are zeolite X and also mixtures of A, X and/or P. A product available commercially and able to be used with preference in the context of the present invention, for example, is a cocrystallizate of zeolite X and zeolite A (approximately 80°s by weight zeolite X), which is sold by CONDEA Augusta S.p.A.
under the brand name VEGOBOND AX~ and may be described by the formula nNa20~ (1-n) Kz0~A1203~ (2-2 . 5) SiOz~ (3 . 5-5. 5) H20.
Suitable zeolites have an average particle size of less than 10 ~m (volume distribution; measurement method:
Coulter counter) and contain preferably from 18 to 22%
by weight, in particular from 20 to 22°s by weight, of bound water.
Organic cobuilders which may be used in the effervescent tablets of the invention are, in particular, polycarboxylates/polycarboxylic acids, polymeric polycarboxylates, aspartic acid, polyacetals, dextrins, further organic cobuilders (see below), and phosphonates. These classes of substance are described below.
Organic builder substances which may be used are, for example, the sodium salts of the polycarboxylic acids mentioned above as a constituent of the effervescent system. Examples of these are the sodium salts of citric acid, adipic acid, succinic acid, glutaric acid, malic acid, tartaric acid, malefic acid, fumaric acid, sugar acids, amino carboxylic acids, nitrilotriacetic acid (NTA), provided such use is not objectionable on ecological grounds, and also 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 .
Also suitable as builders are polymeric poly-carboxylates; these are, for example, the alkali metal salts of polyacrylic acid or of polymethacrylic acid, examples being those having a relative molecular mass of from 500 to 70,000 g/mol.
The molecular masses reported for polymeric poly-carboxylates, for the purposes of this document, are weight-average molecular masses, M",, of the respective acid form, determined basically by means of gel permeation chromatography (GPC) using a W detector.
The measurement was made against an external polyacrylic acid standard, which owing to its structural similarity to the polymers under investigation provides realistic molecular weight values. These figures differ markedly from the molecular weight values obtained using poly-styrenesulfonic acids as the standard. The molecular masses measured against polystyrenesulfonic acids are generally much higher than the molecular masses reported in this document.
Suitable polymers are, in particular, polyacrylates, which preferably have a molecular mass of from 2000 to 20,000 g/mol. Owing to their superior solubility, preference in this group may be given in turn to the short-chain polyacrylates, which have molecular masses of from 2000 to 10,000 g/mol, and with particular preference from 3000 to 5000 g/mol.
Also suitable are copolymeric polycarboxylates, especially those of acrylic acid with methacrylic acid and of acrylic acid or methacrylic acid with malefic acid. Copolymers which have been found particularly suitable are those of acrylic acid with malefic acid which contain from 50 to 90% by weight acrylic acid and from 50 to 10% by weight malefic acid. Their relative molecular mass, based on free acids, is generally from 2000 to 70,000 g/mol, preferably from 20,000 to 50,000 g/mol, and in particular from 30,000 to 40,000 g/mol.
The (co)polymeric polycarboxylates can be used either as powders or as aqueous solutions. The (co)polymeric polycarboxylate content of the compositions is preferably from 0.5 to 20% by weight, in particular from 3 to 10% by weight.
In order to improve the solubility in water, the polymers may also contain allylsulfonic acids, such as allyloxybenzenesulfonic acid and methallylsulfonic acid, for example, as monomers.
Particular preference is also given to biodegradable monomers comprising more than two different monomer units, examples being those comprising, as monomers, salts of acrylic acid and of malefic acid, and also vinyl alcohol or vinyl alcohol derivatives, or those comprising, as monomers, salts of acrylic acid and of 2-alkylallylsulfonic acid, and also sugar derivatives.
Further preferred copolymers are those described in German Patent Applications DE-A-43 03 320 and DE-A-44 17 734, whose monomers are preferably acrolein and acrylic acid/acrylic acid salts, and, respectively, acrolein and vinyl acetate.
Similarly, further preferred builder substances that may be mentioned include polymeric amino dicarboxylic acids, their salts or their precursor substances.
Particular preference is given to polyaspartic acids and their salts and derivatives, which are disclosed in German Patent Application DE-A-195 40 086 to have not only cobuilder properties but also a bleach-stabilizing action.
Further suitable builder substances are polyacetals, which may be obtained by reacting dialdehydes with polyol carboxylic acids having 5 to 7 carbon atoms and at least three hydroxyl groups. Preferred polyacetals are obtained from dialdehydes such as glyoxal, glutaraldehyde, terephthalaldehyde and mixtures thereof and from polyol carboxylic acids such as gluconic acid and/or glucoheptonic acid.
Further suitable organic builder substances are dextrins, examples being oligomers and polymers of carbohydrates, which may be obtained by partial hydrolysis of starches. The hydrolysis can be conducted by customary processes; for example, acid-catalyzed or enzyme-catalyzed processes. The hydrolysis products preferably have average molecular masses in the range from 400 to 500,000 g/mol. Preference is given here to a polysaccharide having a dextrose equivalent (DE) in the range from 0.5 to 40, in particular from 2 to 30, DE being a common measure of the reducing effect of a polysaccharide in comparison to dextrose, which possesses a DE of 100. It is possible to use both maltodextrins having a DE of between 3 and 20 and dried glucose syrups having a DE of between 20 and 37, and also so-called yellow dextrins and white dextrins having higher molecular masses, in the range from 2000 to 30,000 g/mol.
The oxidized derivatives of such dextrins comprise 5 their products of reaction with oxidizing agents which are able to oxidize at least one alcohol function of the.saccharide ring to the carboxylic acid function.
Oxidized dextrins of this kind, and processes for preparing them, are known, for example, from European 10 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 92/18542, WO 93/08251, WO 93/16110, WO 94/28030, WO 95/07303, WO 95/12619 and WO 95/20608. Likewise suitable is an 15 oxidized oligosaccharide in accordance with German Patent Application DE-A-196 00 018. A product oxidized at C6 of the saccharide ring may be particularly advantageous.
20 Oxydisuccinates and other derivatives of disuccinates, preferably ethylenediamine disuccinate, are further suitable cobuilders. Ethylenediamine N,N'-disuccinate (EDDS) is used preferably in the form of its sodium or magnesium salts. Further preference in this context is given to glycerol disuccinates and glycerol trisuccinates as well. Suitable use amounts in formulations containing zeolite and/or silicate are from 3 to 15% by weight.
Examples of further useful organic cobuilders are acetylated hydroxy carboxylic acids and their salts, which may also be present in lactone form and which contain at least 4 carbon atoms, at least one hydroxyl group, and not more than two acid groups. Such cobuilders are described, for example, in International Patent Application WO 95/20029.

A further class of substance having cobuilder properties is represented by the phosphonates. The phosphonates in question are, in particular, hydroxyalkane- and aminoalkanephosphonates. Among the hydroxyalkanephosphonates, 1-hydroxyethane-1,1-diphos-phonate (HEDP) is of particular importance as a cobuilder. It is used preferably as the sodium salt, the disodium salt being neutral and the tetrasodium salt giving an alkaline (pH 9) reaction. Suitable aminoalkanephosphonates are preferably ethylenediamine-tetramethylenephosphonate (EDTMP), diethylenetriamine-pentamethylenephosphonate (DTPMP), and their higher homologs. They are used preferably in the form of the neutrally reacting sodium salts, e.g., as the hexasodium salt of EDTMP or as the hepta- and octa-sodium salt of DTPMP. As a builder in this case, preference is given to HEDP from the class of the phosphonates. Furthermore, the aminoalkanephosphonates possess a pronounced heavy metal binding capacity.
Accordingly, and especially if the compositions also contain bleach, it may be preferred to use aminoalkanephosphonates, especially DTPMP, or to use mixtures of said phosphonates.
Furthermore, all compounds capable of forming complexes with alkaline earth metal ions may be used as cobuilders.
Among the compounds which are used as bleaches and which in water yield H202, sodium perborate tetrahydrate and sodium perborate monohydrate are of particular importance. Examples of further bleaches that may be used include sodium percarbonate, peroxypyrophosphates, citrate perhydrates, and also HZOZ-donating peracid salts or peracids, such as perbenzoates, peroxophthalates, diperazelaic acid, phthalo-iminoperacid or diperdodecanedioic acid. Cleaning products of the invention may also includes bleaches from the group of the organic bleaches. Typical organic bleaches are the diacylperoxides, such as dibenzoyl peroxide, for example. Further typical organic bleaches are the peroxy acids, examples being in particular the alkyl peroxy acids and the aryl peroxy acids. Preferred representatives are (a) peroxybenzoic acid and its ring-substituted derivatives, such as alkylperoxybenzoic acids, and also peroxy-a-naphthoic acid and magnesium monoperphthalate, (b) the aliphatic or substituted aliphatic peroxy acids, such as peroxylauric acid, peroxystearic acid, s-phthalimidoperoxycaproic acid [phthaloiminoperoxy-hexanoic acid (PAP)], o-carboxybenzamidoperoxycaproic acid, N-nonenylamidoperadipic acid and N-nonenylamido-persuccinates, and (c) aliphatic and araliphatic peroxydicarboxylic acids, such as 1,12-diperoxydicarboxylic acid, 1,9-diperoxyazeleic acid, diperoxysebacic acid, diperoxybrassylic acid, the diperoxyphthalic acids, 2-decyldiperoxybutane-1,4-dioic acid, and N,N-terephthaloyl-di(6-aminopercaproic acid) may be used.
As bleaches in the effervescent tablets of the invention it is also possible to use substances which release chlorine or bromine. Examples of suitable chlorine- or bromine-releasing materials include heterocyclic N-bromoamides and N-chloroamides, examples being trichloroisocyanuric acid, tribromoisocyanuric acid, dibromoisocyanuric acid and/or dichloro-isocyanuric acid (DICA) and/or their salts with cations such as potassium and sodium. Hydantoin compounds, such as 1,3-dichloro-5,5-dimethylhydantoin, are likewise suitable.
Bleach activators, which assist the action of the bleaches, may likewise be a constituent of the effervescent tablets. Known bleach activators are compounds which contain one or more N-acyl or O-acyl groups, such as substances from the class of the anhydrides, of the esters, of the imides and of the acylated imidazoles or oximes. Examples are tetraacetylethylenediamine TAED, tetraacetylmethylene-diamine TAMD and tetraacetylhexylenediamine TAHD, and also pentaacetylglucose PAG, 1,5-diacetyl-2,2-dioxohexahydro-1,3,5-triazine DADHT, and isotoic anhydride ISA.
In addition to the conventional bleach activators, or instead of them, it is also possible to incorporate what are known as bleaching catalysts into the tablets.
These substances are bleach-boosting transition metal salts or transition metal complexes such as, for example, Mn-, Fe-, Co-, Ru- or Mo-salen complexes or -carbonyl complexes. Other bleaching catalysts which can be used include Mn, Fe, Co, Ru, Mo, Ti, V and Cu complexes with N-containing tripod ligands, and also Co-, Fe-, Cu- and Ru-amine complexes.
The effervescent tablets may of course also comprise enzymes. Suitable enzymes in the base tablets include in particular those from the classes of the hydrolases such as the proteases, esterases, lipases or lipolytic enzymes, amylases, glycosyl hydrolases, and mixtures of said enzymes. All of these hydrolases contribute to removing stains, such as proteinaceous, fatty or starchy marks. For bleaching, it is also possible to use oxidoreductases. Especially suitable enzymatic active substances are those obtained from bacterial strains or fungi such as Bacillus subtilis, Bacillus licheniformis, Streptomyces griseus, Coprinus cinereus and Humicola insolens, and also from genetically modified variants thereof. Preference is given to the use of proteases of the subtilisin type, and especially to proteases obtained from Bacillus lentus. Of particular interest in this context are enzyme mixtures, examples being those of protease and amylase or protease and lipase or lipolytic enzymes, or protease and cellulase, or of cellulase and lipase or lipolytic enzymes, or of protease, amylase and lipase or lipolytic enzymes, or protease, lipase or lipolytic enzymes and cellulase, but especially protease and/or lipase-containing mixtures or mixtures with lipolytic enzymes. Examples of such lipolytic enzymes are the known cutinases. Peroxidases or oxidases have also proven suitable in some cases. The suitable amylases include, in particular, alpha-amylases, iso-amylases, pullulanases, and pectinases. The enzymes may be adsorbed on carrier substances or embedded in costing substances in order to protect them against premature decomposition.
Dyes and fragrances may be added to the effervescent tablets of the invention in order to enhance the esthetic appeal of the resultant products and to provide the user not only with performance but also with a product which, visually and sensorially, is "typical and unmistakable". As perfume oils and/or fragrances it is possible for the purposes of the present invention to use individual odorant compounds, examples being the synthetic products of the ester, ether, aldehyde, ketone, alcohol, and hydrocarbon types. Odorant compounds of the ester type are, for example, benzyl acetate, phenoxyethyl isobutyrate, p-tert-butylcyclohexyl acetate, linalyl acetate, dimethylbenzylcarbinyl acetate, phenylethyl acetate, linalyl benzoate, benzyl formate, ethyl methylphenylglycinate, allyl cyclohexylpropionate, styrallyl propionate, and benzyl salicylate. The ethers include, for example, benzyl ethyl ether; the aldehydes include, for example, the linear alkanals having 8-18 carbon atoms, citral, citronellal, citronellyloxy-acetaldehyde, cyclamen aldehyde, hydroxycitronellal, lilial and bourgeonal; the ketones include, for example, the ionones, a-isomethylionone and methyl cedryl ketone; the alcohols include anethole, citronellol, eugenol, geraniol, linalool, phenylethyl alcohol, and terpineol; the hydrocarbons include primarily the terpenes such as limonene and pinene.
Preference, however, is given to the use of mixes of 5 different odorants, which together produce an appealing fragrance note. Such perfume oils may also contain natural odorant mixtures, as obtainable from plant sources, examples being pine oil, citrus oil, jasmine oil, patchouli oil, rose oil or ylang-ylang oil.
10 Likewise suitable are clary sage oil, camomile oil, clove oil, balm oil, mint oil, cinnamon leaf oil, lime blossom oil, juniper oil, vetiver oil, olibanum oil, galbanum oil and labdanum oil, and also orange blossom oil, neroliol, orange peel oil, and sandalwood oil. In 15 order to enhance the esthetic appeal of the compositions of the invention, they (or parts thereof) may be colored with appropriate dyes. Preferred dyes, whose selection causes no difficulty whatsoever to the skilled worker, possess a high level of storage 20 stability and insensitivity to the other ingredients of the compositions, and toward light, and also possess no pronounced affinity for to the substrates to be treated with the compositions, such as glass, ceramic, plastic tableware, or textiles, so as not to stain them.
The effervescent tablets of the invention may contain corrosion inhibitors for protecting the articles to be treated, particular importance being possessed by silver protectants in particular. The known substances of the prior art can be used. In general, silver protectants in particular may be selected from the group of the triazoles, benzotriazoles, bisbenzotriazoles, aminotriazoles, alkylaminotriazoles, and transition metal salts or transition metal complexes. Particular preference is given to the use of benzotriazole and/or alkylaminotriazole. Also frequently encountered in cleaning formulations are agents containing active chlorine, which may greatly reduce the corrosion of the silver surface. In chlorine-free cleaners, use is made in particular of oxygen-containing and nitrogen-containing organic redox-active compounds, such as divalent and trivalent phenols, e.g., hydroquinone, pyrocatechol, hydroxyihydroquinone, gallic acid, phloroglucinol, pyrogallol, and derivatives of these classes of compound. Salt-type and complex-type inorganic compounds, such as salts of the metals Mn, Ti, Zr, Hf, V, Co and Ce, also find frequent application.
Preference is given in this context to the transition metal salts, which are selected from the group of the salts and/or complexes of manganese and/or cobalt, and particular preference to cobalt amine complexes, cobalt acetate complexes, cobalt carbonyl complexes, the chlorides of cobalt or manganese, and manganese sulfate. It is likewise possible to use zinc compounds in order to prevent corrosion on the ware.
The effervescent tablets of the invention may be obtained by conventional compression of particulate premixes. The present invention therefore further provides a process for producing effervescent tablets by compressing a particulate premix in conventional manner, wherein the premix for compression, based on its weight, is admixed with from 2 to 20% by weight of one or more substances having a water absorption level of less than 0.5 g of water per 1 g of substance, the water absorption level of the substance being measured during one week of open storage at 30°C and 80%
relative atmospheric humidity, and the entire premix is subsequently tableted.
To prepare the tableted premixes, the ingredients are mixed in a mixer. Following discharge of the mixture from the mixer, said mixture can be passed on for tableting. As regards preferred embodiments of the process of the invention (preferred stability enhancers, amounts of the substances used, etc.), the comments made above for the effervescent tablets of the invention apply analogously. In particularly preferred processes of the invention, the stability enhancer used comprises from 2 to 20% by weight, preferably from 3 to 15% by weight, and in particular from 4 to 10% by weight, of phosphate(s), preferably alkali metal phosphate(s), with particular preference pentasodium and/or pentapotassium triphosphate (sodium and/or potassium tripolyphosphate).
The present invention further provides for the use of phosphates for improving the tabletability and the hardness and abrasion stability of effervescent tablets.
The novel use of these substances leads to advantages in storage stability and other physical properties of the tablets, as the following non-limiting examples show.
Examples:
The effervescent tablet formulations E and V were prepared by tableting a mixture of the substances from the table below under climate-controlled conditions (maximum 30% relative atmospheric humidity). In the case of the example in accordance with the invention, E, sodium tripolyphosphate was added as stability enhancer, whereas the comparative example, V, contained no stability enhancer.
E V

Amidosulfonic acid 60.0 60.0 Sodium hydrogen carbonate 25.0 30.0 Citric acid, anhydrous 5.0 5.0 Sodium tripolyphosphate 4.0 -Salts, perfume, dye remainder remainder Directly following their production, the tablets were placed in blister packs and given an airtight seal. The peel-push foil (the foil through which the tabs are pressed prior to use? has a water vapor permeability of 1.2 g per square meter per day, while the water vapor permeability of the thermoformed film was 0.6 g per square meter per day.
The tablets of the invention were stored over a period of one month during which no formation of gas was observed. After just a few hours of storage, the tablets of the Comparative Example V had severely expanded packs, indicating the formation of gas and the inadequate storage stability.

Claims (30)

1. An effervescent tablet comprising one or more organic acids, one or more substances from the group of the carbonates and/or hydrogen carbonates, and, if desired, further ingredients of laundry detergents and cleaning products, which comprises as stability enhancer, based on the tablet weight, from 2 to 20% by weight of one or more substances having a water absorption level of less than 0.5 g of water per g of substance, the water absorption level of the substance being measured during one week of open storage at 30°C
and 80% relative atmospheric humidity.

2. The tablet as claimed in claim 1, wherein the substance(s) present in the tablet, with a water absorption level of less than 0.5 of water per g of substance, has (have) a water binding capacity of more than 0.1 g of water per g of substance.

3. The tablet as claimed in either of claims 1 and 2, wherein for the substance(s) present in the tablet and having a water absorption level of less than 0.5 g of water per g of substance the difference between the value of the water absorption capacity (stated in grams per gram of substance) and the water binding capacity is less than 0.1.

4. The tablet as claimed in claim 3, wherein the difference between the water absorption capacity and the water binding capacity is less than 0.05.

5. The tablet as claimed in claim 4, wherein the difference between the water absorption capacity and the water binding capacity is less than 0.01.

6. The tablet as claimed in claim 5, wherein the difference between the water absorption capacity and the water binding capacity is less than 0.

7. The tablet as claimed in any one of claims 1 to 6, which comprises at least one phosphate as stability enhancer.

8. The tablet as claimed in claim 7, wherein said Phosphate(s) is an alkali metal phospate(s).

9. The tablet as claimed in claim 8, wherein said phospate(s) is pentasodium and/or pentapotassium triphosphate (sodium and/or potassium tripolyphosphate).

10. The tablet as claimed in any one of claims 7 to 9, wherein said phospate(s) is present in an amount of from 2-20% by weight.

11. The tablet as claimed in claim 10, wherein said phospate(s) is present in an amount of from 3-15%
by weight.

12. The tablet as claimed in claim 11, wherein said Phospate(s) is present in an amount of from 4-10%
by weight.

13. The tablet as claimed in any one of claims 1 to 12, which comprises from 10 to 80% by weight, of one or more organic acids from the group consisting of adipic acid, amidosulfonic acid, succinic acid, citric acid, fumaric acid, maleic acid, malonic acid, oxalic acid, and tartaric acid.

14. The tablet as claimed in claim 13, which comprises from 20 to 75% by weight of said organic acids.

15. The tablet as claimed in claim 14, which comprises from 30 to 70% by weight of said organic acids.

16. The tablet as claimed in any one of claims 1 to 15, which comprises, based on the tablet weight, more than 40% by weight of amidosulfonic acid.

17. The tablet as claimed in claim 16, comprising more than 50% by weight of amidosulfonic acid.

18. The tablet as claimed in claim 17, comprising more than 60% by weight of amidosulfonic acid.

19. The tablet as claimed in any one of claims 1 to 18, which comprises, based on the tablet weight, from 5 to 30% by weight, of alkali metal carbonates and/or hydrogen carbonates.

20. The tablet as claimed in claim 19, which comprises, based on the tablet weight, from 10 to 25% by weight, of alkali metal carbonates and/or hydrogen carbonates.

21. The tablet as claimed in claims 20, which comprises, based on the tablet weight, from 12.5 to 20% by weight, of alkali metal carbonates and/or hydrogen carbonates.

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

23. The tablet as claimed in any one of claims 1 to 22, further comprising one or more substances from the groups of the builders, complexing agents, bleaches, bleach activators, enzymes, dyes, and fragrances.

24. A process for producing an effervescent tablet by compressing a particulate premix in conventional manner, which comprises admixing to the premix for compression, based on its weight, from 2 to 20% by weight of one or more substances having a water absorption level of less than 0.5 g of water per g of substance, the water absorption level of the substance being measured during one week of open storage at 30°C and 80% relative atmospheric humidity, and subsequently tableting the entire premix.

25. The process as claimed in claim 24, wherein the stability enhancer used comprises from 2 to 20% by weight of phosphate(s).

26. The process as claimed in claim 25, wherein the stability enhancer used comprises from 3 to 15% by weight of phosphate(s).

27. The process as claimed in claim 26, wherein the stability enhancer used comprises from 4 to 10% by weight of phosphate(s).

28. The process as claimed in any one of claims 25 to 27, wherein said phosphate(s) is an alkali metal phosphate(s).

29. The process as claimed in claim 28, wherein said alkali metal phosphate(s) is pentasodium and/or pentapotassium triphosphate (sodium and/or potassium tripolyphosphate).

30. The use of phosphates for improving the tabletability and the hardness and abrasion stability of effervescent tablets.