EP0579659B1 - Process for producing detergent tablets for dishwashing machines - Google Patents

Abstract

PCT No. PCT/EP92/00744 Sec. 371 Date Oct. 12, 1993 Sec. 102(e) Date Oct. 12, 1993 PCT Filed Apr. 3, 1992 PCT Pub. No. WO92/18604 PCT Pub. Date Oct. 29, 1992.A process for producing stable, bifunctional, phosphate- and metasilicate-free, low-alkali detergent tablets useful for dishwashing machines from granulated detergent additives consisting of sodium salts of at least one homopolymeric or copolymeric (meth)acrylic acid, comprising agglomerating the granulated detergent additives with builders and water to form an agglomerate, treating the agglomerate with hot air in a fluidized bed, mixing the agglomerate with a bleaching agent, and tabletting the mixture.

Description

Machine dishwashing generally consists of a pre-rinse cycle, a cleaning cycle, one or more intermediate rinse cycles, a rinse cycle and a drying cycle. This applies to machine washing both in the home and in business.

So far, it has been common practice in household dishwashers, hereinafter referred to as HGSM, to store the detergent in a metering box, which is usually located in the door of the machine and opens automatically at the start of the cleaning cycle. The previous pre-rinse cycle is operated without any active substance, i.e. only with the incoming cold tap water.

In a commercial dishwasher, hereinafter referred to as GGSM, the so-called pre-clearing zone corresponds in principle to the pre-wash cycle of an HGSM. When machine washing in commercial kitchens, the detergent added to the cleaning zone is used by overflow in the pre-clearing zone to support the cleaning of the adhering food residues. There are also GGSM in which the pre-clearing zone is only operated with fresh water, but a pre-clearing zone with detergent additive is more effective than pre-clearing with fresh water alone.

The principle of the pre-clearing zone cleaning from GGSM has already been transferred to HGSM and the addition of cleaning agents to the pre-rinse cycle has been made possible by dosing cleaning agents in tablet form and one or more suitable tablets For example, positioned in a free part of the cutlery basket, but also elsewhere in the machine, so that they could act both in the pre-rinse cycle and in the actual cleaning cycle, i.e. bifunctionally.

The use of such tablet-shaped cleaning agents is described for example in DE 35 41 145 A1. These are uniformly composed detergent tablets with a broad dissolution profile for machine dishwashing, which contain the usual alkaline components, in particular from the group of alkali metal silicates and pentaalkali metal phosphates, active chlorine compounds and tabletting aids, and in which the alkali metal silicates are made from a mixture of "sodium metasilicate nohydrate" .8H₂O) and anhydrous sodium metasilicate and the pentaalkali metal triphosphate consists of anhydrous pentasodium triphosphate, the weight ratio of anhydrous sodium metasilicate: sodium metasilicate nonahydrate being between 1: 0.3 and 1: 1.5 and the weight ratio of pentasodium triphosphate to sodium metasilicate: 1 to anhydrous 1: 2, preferably 1: 1 to 1: 1.7.

Such tablets have such a broad dissolution profile that at least 10% by weight of the tap water to be run in is already dissolved in the pre-rinse cycle of an HGSM, thereby developing a pH value of at least 10.0 in the rinsing liquor and, with good hot water solubility, too at least 60% by weight, preferably at least 70% by weight, are available for the cleaning cycle.

The dissolving profile is understood to mean the weight ratio of portions of the tablet, dissolved under the conditions of the pre-rinse cycle, of conventional HGSM to the entire tablet.

However, the known tablets still contain phosphates, which are known to be undesirable.

There are also phosphate-free detergent tablets for machine dishwashing on the market (eg Hui rinsing tabs from Roth GmbH, Bad Ems), which essentially contain silicates, nonionic surfactants, organic complexing agents and percarbonate. If these tablets are placed inside the machine (e.g. in the cutlery basket), however, they dissolve largely or completely even during the pre-rinse cycle, so that practically no detergent is available in the actual cleaning cycle. In addition, the stability of these tablets is unsatisfactory.

DE 40 10 524 A1 describes stable, bifunctional, phosphate-free detergent tablets for machine dishwashing containing silicate, low-foam nonionic surfactants, organic complexing agents, bleaching agents and water, the organic complexing agents according to DE 39 37 469 A1 in the form of a granular one , alkaline cleaning additive, consisting of sodium salts of at least one homopolymeric or copolymeric (meth) acrylic acid, sodium carbonate, sodium sulfate and water. In the manufacture of the tablets, the granular alkaline cleaning additives were mechanically mixed with the other mostly powdery recipe components and pressed in a manner known per se.

In accordance with a market trend, the present invention was based on the object of producing a stable, bifunctional, phosphate- and metasilicate-free, low-alkaline detergent tablet with a broad dissolving profile for machine dishwashing, which at least 10 wt. up to about 40% by weight, thereby developing a pH value of at most about 10.5 in the rinsing liquor and at least 60% by weight to about 90% by weight being available for the cleaning cycle with good hot water solubility .

To produce the known detergent tablets, powder mixtures were pressed which, in addition to sodium metasilicate non-hydrate containing hydrate water, also contained anhydrous sodium metasilicate. This combination of water-containing substances and substances that can absorb water led to an increase in the breaking stability of the tablets during storage. Since the tablets of the invention because of the required low alkalinity cannot contain any of the above-mentioned raw materials, they are not sufficiently stable to breakage after being pressed in accordance with the prior art from powder mixtures or else powder mixtures with a granular content.

It has now been found that stable, bifunctional, phosphate- and metasilicate-free, low-alkaline detergent tablets for automatic dishwashing containing granular, alkaline detergent additives according to DE 39 37 469 A1, builders, bleaches, water and, if necessary, low-foam nonionic surfactants, Enzymes, bleach activators, fragrances and / or dyes come when the granular, alkaline cleaning additives together with the builders, water and optionally nonionic surfactant are again agglomerated in a manner known per se, the granules are subsequently treated in the fluidized bed with hot air, then with the bleach, and optionally a bleach activator, fragrance, enzymes and / or dye are mixed and the mixture obtained is compressed on a conventional tablet press. The tablets produced according to the invention have a high breaking strength (greater than 140 N with a diameter of 35 to 40 mm and a density of about 1.6 to 1.8 g / cm 3), which remains stable during storage and even remains within a short time can significantly increase. When used as intended, the tablets dissolve with a broad dissolution profile.

• (a) 35 bis 60 Gew.-% an Natriumsalzen mindestens einer homopolymeren bzw. copolymeren (Meth-)Acrylsäure,
• (b) 25 bis 50 Gew.-% Natriumcarbonat (wasserfrei gerechnet),
• (c) 4 bis 20 Gew.-% Natriumsulfat (wasserfrei gerechnet) und
• (d) 1 bis 7 Gew.-% Wasser,

vorzugsweise

• (a) 40 bis 55 Gew.-%, insbesondere 45 bis 52 Gew.-%,
• (b) 30 bis 45 Gew.-%, insbesondere 30 bis 40 Gew.-%,
• (c) 5 bis 15 Gew.-%, insbesondere 5 bis 10 Gew.-%, und
• (d) 2 bis 6 Gew.-%, insbesondere 3 bis 5 Gew.-% der genannten Verbindungen.

The cleaning additive and its production and its use in dishwashing detergents is the subject of the unpublished DE 39 37 469 A1. The use in tablets is not mentioned there. It consists of

• (a) 35 to 60% by weight of sodium salts of at least one homopolymeric or copolymeric (meth) acrylic acid,
• (b) 25 to 50% by weight of sodium carbonate (calculated as anhydrous),
• (c) 4 to 20% by weight sodium sulfate (calculated as anhydrous) and
• (d) 1 to 7% by weight of water,

preferably

• (a) 40 to 55% by weight, in particular 45 to 52% by weight,
• (b) 30 to 45% by weight, in particular 30 to 40% by weight,
• (c) 5 to 15% by weight, in particular 5 to 10% by weight, and
• (d) 2 to 6% by weight, in particular 3 to 5% by weight, of the compounds mentioned.

Component (a) consists of homopolymeric or copolymeric carboxylic acids in the form of the sodium salts. Suitable homopolymers are polymethacrylic acid and preferably polyacrylic acid, for example those with a molecular weight of 800 to 150,000 (based on acid). If only homopolymeric polyacrylic acids (in salt form) are used, their molecular weight is preferably 1,000 to 80,000 (based on acid) in the interest of good flowability and storage stability.

Suitable copolymers are those of acrylic acid with methacrylic acid and preferably copolymers of acrylic acid or methacrylic acid with maleic acid. Copolymers of acrylic acid with maleic acid, as are characterized, for example, in EP 25 551 81, have proven to be particularly suitable. These are copolymers which contain 50 to 90% by weight of acrylic acid and 50 to 10% by weight of maleic acid. Copolymers in which 60 to 85% by weight of acrylic acid and 40 to 15% by weight of maleic acid are present are particularly preferred. Their molecular weight, based on free acids, is generally 5,000 to 200,000, preferably 10,000 to 120,000.

Mixtures of different homopolymers and copolymers can also advantageously be used, in particular mixtures of homopolymeric acrylic acid and the copolymers of 50 to 90% by weight of acrylic acid and 50 to 10% of maleic acid described above. Such mixtures, which are characterized by favorable grain properties and high storage stability, can consist, for example, of 10 to 50% by weight of homopolymeric acrylic acid and 90 to 50% by weight of acrylic acid-maleic acid copolymers. Highly polymeric polyacrylic acids can also be used in these mixtures which, when used alone, have a slightly greater tendency to stick or melt than the low molecular weight polyacrylates.

The sodium carbonate (b) and the sodium sulfate (c) are used in anhydrous form. With proportions of sodium carbonate of approx. 40% by weight and more, it is advisable to reduce the water content (d) of the additives to less than 6% by weight or to choose a somewhat higher proportion of sodium sulfate, for example in the range 8 to 15% by weight. Sodium sulfate contents of more than 10% by weight, preferably 15 to 20% by weight, fundamentally improve the grain properties and the shelf life of the additives. On the other hand, sodium sulfate is ineffective fiber when using the additives, which is why its proportion should be as low as possible. It is very surprising that fractions of 5 to 6% by weight (c) are sufficient to add additives with a content of approx. 50% by weight (a), approx. 40% by weight (b) and approx Stabilize 4% by weight (d) and ensure good pouring properties.

Furthermore, the cleaning additives can contain minor components such as dyes and color pigments and can be colored uniformly or speckled. The proportion of such minor components is well below 1% by weight.

Sodium citrates, nitrilotriacetate, phosphonates, alkali carbonates and alkali disilicates can serve as builders. Together with the polycarboxylate-containing cleaning additive, they bind hardening agents such as calcium and magnesium ions from the water or from the food residues through complex formation or dispersion, and thus prevent the formation of limescale deposits in the dishwasher and on the dishes. They can be used as anhydrous and / or as hydrate salts, it also being possible for hydrate salts to form in agglomerating granulation from about 5 to 10, preferably about 6 to 8 parts by weight of water and anhydrous salts.

The polycarboxylates are used as powder, but preferably as granules. The usable polyacrylates include Alcosperse ^R from Alco: Alcosperse ^R 102, 104, 106, 404, 406), Acrysole ^R from Norsohaas: Acrysole ^R A 1N, LMW 45 N, LMW 10 N, LMW 20 N, SP 02N, Degapas ^R from Degussa: Degapas ^R 4104 N, Good-Rite ^R from Goodrich: Good-Rite ^R K-XP 18. Copolymers (polyacrylic acid and maleic acid) can also be used, for example Sokalane ^R from BASF: Sokalan ^R CP 5, CP 7, Acrysole ^R from Norsohaas: Acrysol ^R QR 1014, Alcosperse ^R from Alco: Alcosperse ^R 175. Anhydrous trisodium citrate or trisodium citrate dihydrate are suitable as sodium citrate. The preferred phosphonate is the tetrasodium salt of 1-hydroxyethane-1,1-di-phosphonic acid (Turpinal ^R 4 NZ from Henkel). As alkali carbonate sodium carbonate of any quality is preferably used, such as. B. calcined soda, compressed soda and also sodium bicarbonate. Dried water glass with the module SiO ₂: Na₂O = 1: 2-2.5 is suitable as a disilicate (e.g. Portil ^R A or AW from Henkel, Britesil ^R H 24 or C 24 from Akzo).

Extremely low-foaming compounds are preferably used as nonionic surfactants, which serve to better remove fatty food residues and as a pressing aid. These preferably include C₁₂-C₁₈ alkyl polyethylene glycol polypropylene glycol ethers, each with up to 8 moles of ethylene oxide and propylene oxide units in the molecule. Their share in the total weight of the finished tablets is generally 0.2 to 5, preferably 0.5 to 3% by weight. But you can also use other non-foaming surfactants known as low foams, such as. B. C₁₂-C₁₈ alkyl polyethylene glycol polybutylene glycol ether, each with up to 8 moles of ethylene oxide and butylene oxide units in the molecule and then optionally 0.2 to 2, preferably 0.2 to 1 wt .-%, based on the entire tablet, of defoaming agents such as B. silicone oils, mixtures of silicone oil and hydrophobicized silica, paraffin oil / Guerbet alcohols and hydrophobicized silica.

Active oxygen carriers are now preferably bleaches which are customary constituents of cleaning agents for HGSM. These primarily include sodium perborate mono- and tetrahydrate as well as sodium percarbonate. Since active oxygen only develops its full effect on its own at elevated temperatures, so-called bleach activators are used to activate it at approx. 60 ° C, the temperatures of the cleaning process in the HGSM. Preferred bleach activators are TAED (tetraacetylenediamine), PAG (pentaacetylglucose), DADHT (1,5-diacetyl-2,4-dioxo-hexahydro-1,3,5-triazine) and ISA (isatoic anhydride).

Enzymes such as proteases and amylases can also be used to better remove protein or starch-containing food residues, for example proteases such as BLAP ^R from Henkel, Opitmase ^R -M-440, Optimase ^R -M-330, Opticlean ^R -M-375 , Opticlean ^R -M-250 from Solvay Enzymes, Maxacal ^R CX 450,000, Maxapem ^R from Ibis, Savinase ^R T from Novo or Esperase ^R T from Ibis and amylases such as Termamyl ^R 60 T, 90 T from Novo, Amylase-LT ^R from Solvay Enzymes or Maxamyl ^R P 5000 from Ibis.

The use of tabletting aids, such as mold release agents, for example paraffin oil, is not necessary for compressing the tablets according to the invention and can be omitted if the tablet mixtures contain nonionic surfactants which essentially take on this task. Customary oxidation-stable dyes and fragrances can also be added to the tablet mixtures. For aesthetic reasons, the tablets can also be pressed in colored layers with otherwise the same composition.

The following areas can be considered for frame formulations of the detergent tablets produced according to the invention: Components Area preferred area granular cleaning additive 5 - 30% 6 - 25% Trisodium citrate dihydrate 5 - 40% 9 - 30% Nitrilotrine sodium acetate 0 - 25% 0 - 20% Sodium phosphonate 0 - 10% 0 - 5% Sodium carbonate, anhydrous 5 - 60% 10 - 50% Sodium disilicate 0 - 60% 2 - 30% Sodium bicarbonate 0 - 60% 0 - 30% Sodium perborate monohydrate 3 - 15% 5 - 10% Tetraacetylethylenediamine 0.5 - 4% 1 - 2% nonionic surfactant 0 - 4% 1 - 2% Protease 0.1 - 1% 0.2 - 0.5% Amylase 0.1 - 1% 0.2 - 0.5% Fragrance 0 - 1% 0.1 - 0.5% water 3 - 15% 5 - 10%

The average grain size of the granular cleaning additives is usually 0.2 to 1.2 mm, the proportion of the grains being below 0.1 mm not more than 2% by weight and above 2 mm not more than 20% by weight. Preferably, at least 80% by weight, in particular at least 90% by weight, of the grains have a size of 0.2 to 1.6 mm, the proportion of the grains between 0.1 and 0.05 mm not more than 3% by weight .-%, in particular not more than 1% by weight and the proportion of the grains between 1.6 and 2.4 mm is not more than 20% by weight, in particular not more than 10% by weight. The bulk density is 350 to 550 g / l.

The granular cleaning additives are produced by spray drying an aqueous slurry. The slurry concentration is between 50 and 68% by weight (non-aqueous fraction), preferably between 55 and 60% by weight, the viscosity of the paste being decisive, which should not exceed 10,000 mPa · s and advantageously 2,500 to 6,000 mPa · S is. The temperature of the slurry is usually between 50 and 100 ° C. The pressure at the spray nozzles is generally 30 to 80 bar, preferably 40 to 70 bar. The temperature of the countercurrent dry gases in the entrance zone of the spray tower, i.e. H. in the so-called ring channel is advantageously between 200 and 320 ° C, in particular between 220 and 300 ° C. In the area of the tower outlet it should be between 100 and 130 ° C, preferably between 110 and 125 ° C. Such comparatively high operating temperatures are advantageous for the production of a perfect product and, despite the high proportion of combustible organic substance in the spray product, are not critical, since the self-ignition temperature is above 330 ° C. In the interest of favorable grain properties, the drying is preferably conducted so that the water binding is reduced to less than 1 mole of H₂O per mole of sodium carbonate. Conventional spray drying systems (spray towers) can be used for spray drying, it being possible for the spray nozzles to be arranged in one or more levels.

The spray material leaving the tower, optionally after cooling with flowing air, was mixed with the framework substances and water and, if appropriate, nonionic surfactant, again agglomerated in a manner known per se, for example in a Lödige mixer or also mixers from the companies Imatec, Unimix, Drais or Papenmeier, with the Bleach, optionally a bleach activator, colors and fragrances and / or enzymes mixed and then in total on conventional tablet presses with a pressure of 200 to 1500. 10⁵, preferably 300 to 1000. 10⁵ Pa pressed. The pressing could be carried out in a known manner without die lubrication using commercially available eccentric presses, hydraulic presses or rotary presses. No caking of the tablet mixture was observed on the pressing tools. Tools coated with hard plastic, as well as uncoated, supplied tablets with smooth surfaces, so that in most cases there was no need to coat the punches with soft plastic.

The pressing conditions were optimized with regard to the setting of the desired dissolution profile with sufficient tablet hardness. The flexural strength can serve as a measure of the tablet hardness (method: compare Ritschel. Die Tablette, Ed. Cantor, 1966, p. 313). According to this, tablets with a bending strength greater than 100 N, preferably greater than 150 N, are sufficiently stable under simulated transport conditions. The bending or breaking strength of the tablets, regardless of their format, can be determined by the degree of compaction, i. H. the baling pressure can be controlled.

Corresponding tablet hardnesses were achieved at the compression pressures given above. Differences in solubility can be compensated to a limited extent for different compositions by means of variations in the pressure.

The specific weight of the compacts was between 1.2 and 2 g / cm³, preferably between 1.4 and 1.8 g / cm³. The compression during the pressing process caused changes in the density, which from 0.6 to 1.2 g / cm³, preferably 0.8 to 1.0 g / cm³ to 1.2 to 2.0 g / cm³, preferably 1.6 to 1.8 g / cm³ rose.

The shape of the tablet can also influence the breaking strength and the rate of dissolution via the outer surface exposed to the H₂O attack. For stability reasons, cylindrical compacts with a diameter / height ratio of 0.6 to 4.0: 1 were produced.

The tablet was loaded with a wedge to measure the breaking strength. The breaking strength corresponds to the weight of the wedge-shaped load that causes the tablet to break.

The amounts of the substance mixture to be compressed for the individual tablets can be varied as desired within technically reasonable limits. Depending on their size, 1 to 2 or even more tablets per machine filling are preferably used in order to provide the entire cleaning process with the necessary active substance content of cleaning agent. Tablets of 20 to 40 g in weight and a diameter of 35 to 40 mm are preferred, one of which must be used in each case. Larger tablets are generally more sensitive to breakage and, moreover, are compressed at a slower rate. With smaller tablets, the handling advantage compared to granular or powder detergents would be reduced.

If the remaining constituents of the detergent mixture were added individually to the granular cleaning additive, the quality of the tablets obtained therefrom was unusable for the trade, since they u. a. had an insufficient breaking strength. The tablets also caked on the mixtures on the upper ram of the presses.

The following applies to the components of the following examples:

Nonionic surfactants:

Fatty alcohol ethoxylates from BASF:
Plurafac LF 221
Plurafac LF 223: alkyl (C₁₂-C₁₈) polyethylene glycol (<8 EO) polybutylene glycol (<8 BuO) ether
Plurafac LF 403: alkyl (C₁₂-C₁₈) polyethylene glycol (<8 EO) polypropylene glycol - (<8 PO) ether
Fatty alcohol ethoxylates from Henkel:
Dehypon LT 104: fatty alcohol (C₁₂-C₁₈) * 9EO-butyl ether
Dehypon LS 54: fatty alcohol (C₁₂-C₁₈) * 5EO * 4PO
TAED = tetraacethylethylenediamine
NTA = nitrilotrine sodium acetate
* = reacted with phosphonate = turpinal ^R 4 NZ = tetrasodium salt of 1-hydroxyethane-1,1-di-phosphonic acid from Henkel

Examples

• 1. 18.7 parts by weight of a granular alkaline cleaning additive consisting of 40.8% by weight of sodium carbonate anhydrous, 5.0% by weight of sodium sulfate, 50.0% by weight of the sodium salt of the copolymer of maleic acid and acrylic acid with a molecular weight of 70,000 (Sokalan CP 5 from BASF) and 4.2% by weight of water, 9.4 parts by weight of trisodium citrate. 2 H₂O, 18.7 parts by weight of sodium disilicate (1: 2), 35.0 parts by weight of anhydrous, compacted sodium carbonate, 0.47 parts by weight of enzyme (BLAP ^R ), 1.9 parts by weight of C₁₂ -C₁₈-alkyl-polyethylene glycol (≦ 8 EO) -polybutylene glycol (≦ 8 BuO) ether and 7.0 parts by weight of water were granulated in a Lödige ploughshare mixer and then aftertreated in a fluidized bed system with hot air. The resulting granules had a bulk density of 950 g / l. It was with 6.5 parts by weight of sodium perborate monohydrate, 1.9 parts by weight of tetraactylethylenediamine granules, 0.47 parts by weight of amylase (Termamyl 60 T ^R ), 0.47 parts by weight of protease (BLAP ^R ) and 0 , 56 parts by weight of perfume are mixed homogeneously in the Lödige mixer and the mixture is then compressed into tablets on a rotary tablet press with a pressing force of 35 KN. The tablet weight was set at 35 g. The tablets had a diameter of 38 mm and a height of 18.1 mm. The density was 1.75 g / cm³. The breaking strength of the tablets was 370 N immediately after production, 320 N after storage for 1 week at room temperature and 320 N after storage for 2 weeks. 12 to 13 g of the tablet were removed in the pre-rinse cycle. The pH of a 10% solution of the tablet was 10.4.
• 2. For comparison, two tablets were made from powder mixtures of the individual components. The solid raw materials were mixed in a Lödige ploughshare mixer and the liquid components were added at the end. The pressing was carried out on a Korsch EK IV eccentric press.

composition

example 2 A 2 B Cleaning additive (granular)% 22.0 19.87 Tri-Na citrate x 2H₂O% 5.0 20.00 Sodium disilicate% 20.0 - Sodium carbonate, anhydrous% 29.0 44.93 Sodium bicarbonate% 9.4 - Sodium perborate x 1H₂O% 7.0 7.00 % Tetraacetylethylenediamine 2.0 2.00 Termamyl ^R (amylase)% 0.5 0.50 BLAP ^R (protease)% 0.5 0.50 Plurafac LF 403% 4.0 2.00 Perfume % 0.6 0.20

Press data and tablet properties

example 2 A 2 B Bulk weight the mixture g / l 870 620 Tablet weight g 25th 25th Tablet diameter mm 38 38 Tablet density g / cm³ 1.57 1.39 * Press force KN 13.5 25th Breaking strength after manufacture N 140 90 after 1 week N 140 82 Detachment after pre-rinse g about 10 10th * A higher compression was not possible because the tablet was then "capped", which means that part of the tablet mass got stuck on the ram of the compact.

Analogously to example 1, tablets were pressed from the following recipes: raw materials 3rd 4th Granular cleaning additive 19.87 19.87 Turpinal 4 NZ 2.00 2.00 Sodium carbonate, anhydrous 45.93 45.93 Sodium citrate, anhydrous 20.00 20.00 Sodium perborate monohydrate 7.00 7.00 TAED 2.00 2.00 Termamyl 60 T (protease) 0.50 0.50 BLAP 140 (amylase) 0.50 0.50 Plurafac LF 403 2.00 2.00 Fragrance 0.20 0.20 water 2.88 6.88 Bulk density (g / l) 610 605 Tablet weight (g) 23.8 23.8 Tablet height (mm) 14.3 14.1 Tablet diameter (mm) 38 38 Tablet density (g / ml) 1.46 1.4g Hardness immediately (N) 220 285 Hardness after 1 day (N) 310 341 Hardness after 4 days (N) 270 390

Examples 3 and 4

Tablets with sufficient hardness at break, which also cure significantly after one day of storage, were obtained by re-granulating the raw materials: granular cleaning additive, sodium carbonate and Plurafac LF 403 with different amounts of water. The other raw materials: Turpinal 4NZ, citrate, perborate, TAED, protease, amylase and fragrance were added to the pre-granulate and the whole was then pressed.

Claims (1)

1. A process for the production of stable, dual-function, phosphate- and metasilicate-free, low-alkali detergent tablets for dishwashing machines containing granular, alkaline detergent additives, low-foaming nonionic surfactants, builders, bleaching agents, water and optionally bleach activators, perfumes, dyes and enzymes, characterized in that the granular alkaline detergent additives are resubjected to agglomerating granulation in known manner together with the builders, water and nonionic surfactant, if any, the granules formed are subsequently aftertreated with hot air in a fluidized bed and then mixed with the bleaching agent and optionally with a bleach activator, fragrance, enzymes and/or dye and the mixture obtained is tabletted in a standard tabletting press.