EP0591282B1 - Method for the production of cleaning-agent tablets for machine dishwashing - Google Patents

Abstract

Disclosed is a method of producing phosphate-free and metasilicate-free low-alkali cleaning-agent tablets for machine dishwashing, the tablets consisting of solid alkali salts of at least one homopolymer or copolymer of (meth)acrylic acid, which may be in the form of granules, builders, low-foam surfactants, bleaching agents and, optionally, enzymes, bleach activators, fragrances and colourings. In this method, the sodium carbonate acting as one of the builders is used in anhydrous form. It indergoes mixing, either alone or together with the other builders and the solid alkali salt of (meth)acrylic acid, with the quantity of water necessary for partial hydration of the anhydrous carbonate, i.e. approximately 5 to 40 % by weight. The remaining components of the mixture are then added and the mixture compressed into tablet form.

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 pre-rinse cycle that is running before is operated without any active substance, i.e. exclusively with the tap water that is to be run.

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-A-35 41 145. 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.

Tablets of this type have such a broad dissolving profile that they are dissolved by at least 10% by weight of tap water in the pre-rinsing phase of an HGSM, thereby developing a pH of at least 10.0 in the rinsing liquor and at least 60 with good hot water solubility % 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.

German patent application DE-A-40 10 524 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 German patent application DE-A -39 37 469 in the form of a granular, 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.

The present invention was based on a market trend, the task of producing a stable, bifunctional, phosphate and metasilicate-free, low-alkaline detergent tablet with a broad dissolution profile for automatic dishwashing, which is at least 10% by weight to approximately 10% by weight of tap water in the pre-rinsing phase of an HGSM 50% by weight is dissolved, a pH value of at most about 10.5 is developed in the washing liquor and at least 50% by weight to about 90% by weight is still 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 can not contain any of the raw materials mentioned above, they are not stable enough after breaking according to the prior art from powder mixtures or powder mixtures with a granular content.

It has now been found that stable, bifunctional, phosphate- and metasilicate-free, low-alkaline detergent tablets, which develop a pH value of at most about 10.5 in the washing liquor, for automatic dishwashing with a content of solid alkali salts of at least one homopolymer or copolymeric (meth) acrylic acid, builders, low-foam surfactants, bleaching agents, optionally enzymes, bleach activators, fragrances and dyes, if the sodium carbonate serving as part of the builders is used in anhydrous form, first in a mixing cycle, preferably alone or with the other builders and the solid alkali salts of at least one homopolymeric or copolymeric (meth) acrylic acid together with the amount of water required for the partial hydration of the anhydrous sodium carbonate of about 5-40, preferably about 7-20 wt .-%, based on the as Anhydrous sodium carbonate used as framework at, added, then the remaining substances are added to the mixture and the mixture thus obtained is compressed on a conventional tablet press. The storage-stable tablets produced in accordance with the invention have a high breaking strength (greater than 140 N with a diameter of about 30 to 40 mm and a density of about 1.4 to 1.7 g / cm 3), which also remain stable during storage and within a short time Time can still increase significantly.

The solid alkali salts of at least one homopolymeric or copolymeric (meth) acrylic acid can be used as commercially available powders or granules or as a so-called cleaning additive.

• (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, its production and its use in dishwashing detergents is the subject of the unpublished German patent application DE-A-39 37 469. 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-B-25 551, 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 be used with advantage, 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 be made, for example, from 10 to 50 wt % By weight of acrylic acid-maleic acid copolymers exist. 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 polycarboxylates are used as powder, but preferably as granules. The usable polyacrylates include, for example, Sokalane ^R CP 10, PA 10 and PM 10 from BASF, 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, Degapas ^R from Degussa: Degapas ^R 4104 N, Good-Rite ^R from Goodrich: Good-Rite ^R K-XP 18, K 739 and K 7200 N. Also copolymers (Polyacrylic acid and maleic acid) can be used, for example Sokalane ^R from BASF: Sokalan ^R CP 5, CP 7, Acrysole ^R from Norsohaas: Acrysol ^R QR 1014 and SP O2N, Alcosperse ^R from Alco: Alcosperse ^R 175. 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.

In addition to the alkali carbonates, sodium citrates, nitrilotriacetate, phosphonates and alkali disilicates can also serve as builders. You tie together with the polycarboxylate-containing cleaning additive component through complex formation or dispersion, hardness-forming agents such as calcium and magnesium ions from the water or from the food residues, 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. As alkali carbonate sodium carbonate of any quality is preferably used, such as. B. calcined soda, compressed soda and also sodium bicarbonate. 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). Dried water glass with the module SiO₂: 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 nonionic compounds are preferably used as low-foaming surfactants, which serve to better remove fatty food residues and as pressing aids. 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 include primarily sodium perborate mono- and tetrahydrate as well as sodium percarbonate and sodium caroate. Since active oxygen only develops its full effect on its own at elevated temperatures, so-called bleach activators are expediently used to activate it at about 60 ° C., the temperatures of the cleaning process in the HGSM. Serve as bleach activators preferably 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.

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 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 usually be omitted if the tablet mixtures contain nonionic surfactants which essentially take on this task. Na-hydrogen carbonate is preferably used to set the desired pH.

The following areas are possible 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 - 45% 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 - 10% 4 - 6%

The average grain size of the granular cleaning additives is usually 0.2 to 1.2 mm, the proportion of the grains below 0.1 mm advantageously 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 weight is about 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. 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 counter-current dry gases in the entrance zone of the spray tower, ie 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 to less is reduced as 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 was mixed with the other tablet components as described, if necessary after cooling with flowing air, and then in total on conventional tablet presses with a compression 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 about 1.2 and 2 g / cm³, preferably between about 1.4 to 1.8 g / cm³. The compression during the pressing process caused changes in the density, which from about 0.4 to 1.2 g / cm³, preferably about 0.6 to 1.0 g / cm³ to about 1.2 to 2.0 g / cm³, preferably about 1.4 to 1.6 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 reasons of stability, cylindrical compacts with a diameter / height ratio of approximately 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 about 20 to 40 g in weight and a diameter of about 35 to 40 mm are preferred, of which one must be used in each case.

If sodium carbonate was not hydrated or used as a full hydrate, the quality of the tablets obtained from the mixture was unusable for the trade, since it could. 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 (C₁₂C₁₈) polyethylene glycol (<8 EO) polybutylene glycol (<8 BuO) ether
Plurafac LF 403: alkyl (C₁₂C₁₈) polyethylene glycol (<8 EO) polypropylene glycol - (<8 PO) ether
Fatty alcohol ethoxylates from Henkel:
Dehypon LT 104: fatty alcohol (C₁₂C₁₈) * 9EO-butyl ether
Dehypon LS 54: fatty alcohol (C₁₂C₁₄) * 5EO * 4PO
* = implemented with
Turpinal ^R 4 NZ = tetrasodium salt of 1-hydroxyethane-1,1-di-phosphonic acid from Henkel
TAED = tetraacethylethylenediamine
NTA = nitrilotrine sodium acetate
h = hours
The amounts in the examples below are percentages by weight.

Examples example 1

A 50 kg batch was prepared in a 130 l Lödige ploughshare mixer. For this purpose, 6.8 parts by weight of sodium carbonate anhydrous, 32.0 parts by weight of sodium bicarbonate and 4.0 parts by weight of water were first mixed with the chopper running and then immediately further with 20.0 parts by weight of a granular alkaline cleaning additive , consisting of 40.8% by weight sodium carbonate anhydrous, 5.0% by weight 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, 20.0 parts by weight of sodium citrate dihydrate, 2.0 parts by weight of Plurafac ^R LF 403 and 0.2 part by weight of fragrance. Without a chopper, 2.0 parts by weight of TAED, 7.0 parts by weight of sodium perborate monohydrate, 0.5 part by weight of BLAP ^R 140 and 0.5 part by weight of Termamyl ^R 60 T were then mixed in. The mixture was compressed into 25 g tablets with a diameter of 38 mm using a "Korsch PH 423" rotary press. The filling height in the matrices was 31 - 33 mm. Compression was carried out to a tablet height of 12.3 and 15 mm. Pressing directly directly n. 1 week Pressing forces: Upper stamp 115 KN 60 KN 65 KN Lower stamp 98 KN 42 KN 45 KN Tablet height 12.3 mm 15 mm 15 mm Hardness after manufacture > 500 N 230 N 110 N. Hardness after 72 hours > 500 N 300 N 110 N.

Compression with a deposited mixture resulted in less stable tablets.

Examples 2-4

Analogously to Example 1, tablets with different contents of sodium carbonate and sodium hydrogen carbonate with the same water content were produced (cf. Table 1), which showed similarly good results. Sokalan ^R CP 5 powder also gave stable, well-curing tablets. Table 1 Tablets with different soda / bicarbonate contents with the same water content raw material 2nd 3rd 4th Granular cleaning additive - 20.0 20.0 Sokalan ^R CP 5 powder 10.8 - - Sodium citrate dihydrate 20.0 20.0 20.0 Sodium carbonate, anhydrous 16.0 31.8 38.8 Sodium bicarbonate 32.0 7.0 - Sodium perborate monohydrate 7.0 7.0 7.0 TAED 2.0 2.0 2.0 Plurafac LF 403 2.0 2.0 2.0 BLAP 140 0.5 0.5 0.5 Termamyl 60 T. 0.5 0.5 0.5 Fragrance 0.2 0.2 0.2 water 9.0 9.0 9.0 pH 10% 9.2 9.9 10.3 Tablet weight 25th 25th 25th Tablet diameter (mm) 38 38 38 Tablet density g / ml 1.74 1.70 1.64 Tablet hardness direct (N) 388 478 440 Tablet hardness after 72 h (N) > 500 > 500 > 500 Tablet residue after pre-rinse (g) 18.0 19.8 19.5

Examples 5 and 6 (Comparative Examples)

Even when using pre-hydrated sodium carbonate decahydrate, post-curing unbreakable tablets were obtained, but sodium carbonate decahydrate is difficult to process because of its low melting point of 32 ° C. Baking and clumping occurred in the storage container. The decahydrate was mixed together with the remaining components in a Lödige ploughshare mixer. The mixture obtained in this way was compressed on a "Korsch EK IV" eccentric press to give tablets weighing 26 g. When using 38 mm tabletting tools and a filling height of 33 mm in the die, the compression to a tablet height of approx. 15 mm was carried out. The press forces required were 70 to 75 KN for the upper punch and 50 to 55 KN for the lower punch. See Table 2 for results. Table 2 Use of hydrated salts to improve resistance to breakage - sodium carbonate decahydrate raw materials 5 6 Granular cleaning additive 19.87 19.87 Sodium carbonate, anhydrous 35.93 25.93 Sodium carbonate decahydrate 12.00 12.00 Bicarbonate - 10.00 Turpinal ^R 4 NZ 2.00 2.00 Sodium citrate anhydrous 20.00 10.00 Sodium citrate * 2H₂O - 10.00 Sodium perborate monohydrate 7.00 7.00 TAED 2.00 2.00 Protease 0.50 0.50 Amylase 0.50 0.50 Fragrance 0.20 0.20 Bulk density g / l 625 680 Tablet weight g 24.0 26 Tablet height mm 14.75 14.9 Tablet diameter mm 38 38 Tablet density g / ml 1.43 1.54 Hardness immediately N 147 175 Hardness after 1 day N 284 265 Hardness after 2 days N 273 290 Hardness after 3 days N 273 358

Examples 7 and 8:

If the formulations contained sodium disilicate as an additional alkali carrier in addition to sodium carbonate, post-curing break-resistant tablets were also obtained (see Table 3). Table 3 Tablets with disilicate (Portil A) and different water contents raw material 7 8th Granulated cleaning additive 18.9 18.6 Tri-Na Citrate 9.4 9.3 Portile A 18.2 18.6 Sodium carbonate, anhydrous 35.4 35.0 Sodium perborate monohydrate 6.6 6.5 TAED 2.0 1.9 Termamyl 60 T. 0.5 0.4 BLAP 140 0.5 0.4 Plurafac LF 403 1.9 1.9 Fragrance 0.2 0.2 Paraffin oil 0.4 - water 6.0 7.2 pH 10% Tablet weight (g) 35 35 Tablet diameter (mm) 38 38 Tablet hardness direct (N) 440 240 Tablet hardness after 3 days (N) > 500 > 500

Claims (3)

1. A process for the production of stable, dual-function phosphate- and metasilicate-free, low-alkali detergent tablets, which develop a pH value of at most about 10.5 in the wash liquor, for dishwashing machines containing solid alkali metal salts of at least one homopolymeric or copolymeric (meth)acrylic acid, builders, low-foaming detergents, bleaching agents and optionally enzymes, bleach activators, fragrances and dyes, characterized in that the sodium carbonate serving as part of the builders is used in anhydrous form and is first mixed in a mixing step preferably on its own or with the other builders and the solid alkali metal salt of at least one homopolymeric or copolymeric (meth)acrylic acid together with water in the quantity necessary for partial hydration of the anhydrous sodium carbonate, i.e. in a quantity of around 5 to 40% by weight, based on the anhydrous sodium carbonate used as builder, after which the remaining constituents of the mixture are added and the mixture obtained is tabletted in a standard tablet press.
2. A process as claimed in claim 1, characterized in that the solid alkali metal salts of the at least one homopolymeric or copolymeric (meth)acrylic acid are used in powder or granular form.
3. A process as claimed in claim 1, characterized in that the solid alkali metal salts of the at least one homopolymeric or copolymeric (meth)acrylic acid are used as granular detergent additives in accordance with German patent application DE-A-39 37 469.