EP0523095B1 - Stable, bifunctional, phosphate-free detergent tablets for use in dishwashing machines - Google Patents

Abstract

Stable, bifunctional, phosphate-free detergent tablets for use in dishwashing machines contain silicate, low-foam nonionic tensides, organic complex builders, bleaches and water. The organic complex builder is a granular alkaline detergent additive, consisting of (a) sodium salts of at least one (meth)acrylic acid homopolymer or copolymer, (b) sodium carbonate, (c) sodium sulphate, and (d) water. The silicate is anhydrous sodium metasilicate and its penta- and/or nonahydrate.

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 is carried out without any active substance, i.e. exclusively with the cold 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 pre-clearing zone cleaning from GGSM has already been transferred to HGSM and dosing of cleaning agents has already been made possible for the pre-rinse cycle by dosing cleaning agents in tablet form and one or more suitable tablets, for example in a free part of the cutlery basket, but also in others Positioned 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-OS 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.

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.

However, 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 as far as possible, even completely, during the pre-rinse cycle, so that no cleaning agents are left in the actual cleaning cycle Available. In addition, the stability of these tablets is unsatisfactory.

The present invention was therefore based on the object of developing a stable, bifunctional, phosphate-free detergent tablet with a broad dissolving profile for machine dishwashing, which in the pre-rinse cycle of an HGSM from the incoming cold tap water to at least 10% by weight to about 40% by weight is dissolved, thereby developing a pH value of at least 10.0 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.

• (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),
• (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.-%,
• (d) 2 bis 6 Gew.-%, insbesondere 3 bis 5 Gew.-%,

und 30 bis 80 Gew.-% Silikat, berechnet als Na₂SiO₃, als wasserfreies Natriummetasilikat und dessen Penta- und/oder Nonahydrat im Gewichtsverhältnis von 1 : 0,1 bis 1 : 1,0, vorzugsweise von 1 : 0,15 bis 1 : 0,8 enthalten.The object was achieved by stable, bifunctional, phosphate-free detergent tablets for machine dishwashing containing silicate, low-foam nonionic surfactants, organic complexing agents, bleaching agents and water, which are characterized in that they contain the organic complexing agents in the form of 10 to 40, preferably 15 to 35 wt .-%, based on the total mixture of the tablet components, a spray-dried granular, alkaline cleaning additive consisting 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 of sodium sulfate (calculated as anhydrous),
• (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,
• (d) 2 to 6% by weight, in particular 3 to 5% by weight,

and 30 to 80 wt .-% silicate, calculated as Na₂SiO₃, as anhydrous sodium metasilicate and its penta- and / or nonahydrate in a weight ratio of 1: 0.1 to 1: 1.0, preferably from 1: 0.15 to 1: 0.8 included.

"Pentahydrate" is understood here and below to mean a compound of the formula Na₂H₂SiO₄.4H₂O, and "nonahydrate" is a compound of the formula Na₂H₂SiO₄.8H₂O.

This cleaning additive and its preparation and its use in dishwashing detergents is the subject of the unpublished EP-A-0432437. The use in tablets is not mentioned there.

The tablets of the invention have a particularly high breaking strength at a sodium metasilicate nonahydrate content (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 can be stored within increased significantly in a short time. They can be easily manufactured on eccentric, hydraulic or rotary presses and solve well when used as intended.

If the components of the spray-dried granular cleaning additive are added individually to the mixture of the components to be tabletted, for example in accordance with DE 2 435 479 A1, the quality of the tablets obtained therefrom is unusable for the trade since they u. a. have an insufficient breaking strength. The tablets also bake on the mixtures on the upper ram of the presses.

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, such as are characterized for example in EP 25 551 B1, 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. Your 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 detergents 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 compositions. On the other hand, sodium sulfate is ineffective fiber when using the agents, which is why its proportion should be as low as possible. It is very surprising that fractions of 5 to 6 wt.% (C) are sufficient to contain agents with a content of approx. 50 wt.% (A), approx. 40 wt.% (B) and approx Stabilize 4% by weight (d) and ensure good pouring properties.

The agents may also contain minor constituents such as dyes and color pigments and may be colored uniformly or speckled. The proportion of such minor components is well below 1% by weight.

The average grain size of the agent 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 being 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 not more than 20% by weight, in particular not more than 10% by weight % is. The bulk density is 350 to 550 g / l.

The granules 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 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 can, if necessary after cooling with flowing air, be mixed directly with the other tablet components and compressed with them.

Sodium metasilicate, in anhydrous and in the form of penta- and / or in particular nonahydrate, can be used as the silicate. The total alkali metal silicate content of the tablets, calculated as Na₂SiO₃, is 30 to 80, preferably 55 to 65% by weight. The tablets are particularly easy to compress if 5 to 30, preferably 5 to 25 and in particular 10 to 25% by weight, calculated as anhydrous alkali metasilicate, in the form of sodium metasilicate pentahydrate and / or 5 to 30, preferably 8 to 25 and in particular 12 to 25% by weight, calculated as anhydrous alkali metasilicate, in the form of sodium metasilicate nonahydrate, the weight ratio of sodium metasilicate pentahydrate to sodium metasilicate nonahydrate being used can be around 1: 1 to 1: 1.5. The total amount of hydrates is the same as the amount when using the individual hydrates.

The dissolution profile can be varied within wide limits by varying the ratio of sodium metasilicate, anhydrous, to nonahydrate. The weight ratio of anhydrous sodium metasilicate to nonahydrate is between 1: 0.1 to 1: 1.0 and in particular between 1: 0.15 to 1: 0.8.

Extremely low-foaming compounds are preferably used as nonionic surfactants. 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 chlorine carriers and active oxygen carriers are common components of cleaning agents for HGSM as bleaching agents.

Trichloroisocyanuric acid is preferred as the active chlorine carrier, but also other known solid compounds, such as. B. sodium dichloroisocyanurate, its dihydrate and potassium chloroisocyanurate can be used in the marketable form without impairing the tablettability. Your quantities are 0.5 to 5.0, preferably 1.0 to 2.5% by weight, based on the active chlorine content and the total tableting mixture.

But active oxygen carriers can also be used particularly advantageously. These primarily include sodium perborate mono- and tetrahydrate as well as sodium percarbonate. Their share in the total weight of the tablets is 3 to 20, preferably 5 to 18%.

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 because the tablet mixtures contain nonionic surfactants.

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.

If necessary, anhydrous sodium carbonate can also be added in order to set a desired pH value; the amount can be 2 to 20% by weight and preferably 4 to 16% by weight.

The cleaning additives were then mixed in an amount of 10 to 40, preferably 15 to 35,% by weight in a Lödige mixer with the remaining constituents of the formulations, and the resulting tablet mixture was then subjected to a tablet pressure of 200 to 1 on conventional tablet presses 500. 10⁵, preferably 300 to 600 · 10⁵ Pa pressed.

The mixture of the cleaning additives, the anhydrous sodium metasilicate, the corresponding hydrates, the nonionic surfactants and the bleaching agents could be pressed 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 must be optimized with a view to setting the desired dissolution profile while at the same time having 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). Tablets with a bending strength greater than 120 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 dissolving speed of the surface exposed to the H₂O attack. For stability reasons, cylindrical compacts with a diameter / height ratio of 0.6 to 3.0: 1 were produced.

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. Prefers are tablets of 30 to 40 g in weight and a diameter of 35 to 40 mm, one of which must be used. 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.

Examples

• 1. 16 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 Molar mass of 70,000 (Sokalan CP 5 from BASF) and 4.2% by weight of water were placed in a Lödige mixer with 2 parts by weight of anhydrous sodium carbonate, 42.4 parts by weight of anhydrous sodium metasilicate, 30.6 parts by weight. Parts of sodium metasilicate pentahydrate, 7 parts by weight of sodium perborate monohydrate and 2 parts by weight of C₁₂-C₁₄ fatty alcohol + 5 moles of ethylene oxide (EO) + 4 moles of propylene oxide (PO) mixed and compressed to tablets on a rotary tablet press. 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 1.71 g / cm³, the breaking strength of the tablet was over 137.2 N (14 kg).
• 2. There were 16 parts by weight of a cleaning additive according to Example 1 with 9 parts by weight of anhydrous sodium carbonate, 55 parts by weight of anhydrous sodium metasilicate, 12 parts by weight of sodium metasilicate pentahydrate, 7 parts by weight of sodium percarbonate and 1 part by weight C₁₂-C₁₈ fatty alcohol + 9 EO-butyl ether mixed and compressed into 35 g tablets (tablet diameter 38 mm, tablet height 18.35 mm, density 1.68 g / cm³, breaking strength greater than 137.2 N (14 kg)).
• 3. Again 16 parts by weight of the alkaline cleaning additive according to Example 1 were mixed with 3 parts by weight of anhydrous sodium carbonate, 46.9 parts by weight of anhydrous sodium metasilicate, 26.1 parts by weight of sodium metasilicate pentahydrate, 7 parts by weight of sodium percarbonate and a part by weight of C₁₂-C₁₈ fatty alcohol + 9 EO-butyl ether mixed and compressed to form 35 g tablets (tablet diameter 38 mm, tablet height 18.3 mm, density 1.69 g / cm³` breaking strength greater than 137.2 N (14 kg)).
• 4. 16 parts by weight of an alkaline cleaning additive according to Example 1 were mixed with 55 parts by weight of anhydrous sodium metasilicate, 12 parts by weight of sodium metasilicate pentahydrate and 16 parts by weight of sodium percarbonate and 1 part by weight of C₁₂-C₁₄ fatty alcohol + 4 EO + 5 PO mixed and compressed (tablet weight 35 g, tablet diameter 38 mm, tablet height 18.15 mm, density 1.70 g / cm³, breaking strength greater than 137.2 N ( 14 kg)).

The tablets produced according to the above examples were used in a Miele G 590 dishwasher in the 55 ° C. program by placing them in the cutlery basket. The following results were achieved: Examples 1 2nd 3rd 4th Detachment in the pre-wash program at 20 ° C% 33 31 37 27 Dissolved after cleaning program% 100 100 100 100

The following examples serve to demonstrate that the breaking strength of the tablets, when using or using sodium metasilicate nonahydrate, automatically doubles or triples even after short storage times. If this event can be taken into account, the compression of the raw material mixtures into tablets with lower pressing forces can be achieved.

Measurement of breaking strength

The tablet is loaded by a wedge. The breaking strength corresponds to the weight of the wedge-shaped load that causes the tablet to break. example 5 6 7 8th Sodium metasilicate, anhydrous% 47.9 46.0 49.0 49.7 Netrium metasilicate pentahydrate% - 20.5 7.5 - Sodium metasilicate nonahydrate% 18.6 - 10.0 18.8 Cleaning additive% 16.5 16.5 16.5 16.5 acc. example 1 Soda, anhydrous% 9.0 9.0 9.0 9.0 Perborate monohydrate% 7.0 7.0 7.0 - Trichloroisocyanuric acid% - - - 5.0 C₁₂-C₁₄ fatty alcohol + 4 EO + 5 PO% 1.0 1.0 1.0 - Paraffin oil% - - - 1.0 Tablet diameter mm 20th 20th 20th 20th Weight g 5 5 5 5 Density g / cm³ 1.46 1.47 1.47 1.56 Breaking strength directly N 369 251 332 367 after 1 hour N 468 300 418 495 after 48 hours N 764 287 674 833

Claims (10)

1. Stable bifunctional phosphate-free detergent tablets for dishwashing machines containing silicate, low-foaming nonionic surfactants, organic complexing agents, bleaching agents and water, characterized in that they contain the organic complexing agents in the form of 10 to 40% by weight - based on the mixture of tablet constituents as a whole - of a spray-dried, granular alkaline detergent additive consisting 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 (counted as anhydrous),

   (c) 4 to 20% by weight of sodium sulfate (counted as anhydrous),

   (d) 1 to 7% by weight of water,

   and 30 to 80% by weight of silicate, calculated as Na₂SiO₃, as anhydrous sodium metasilicate and its penta- and/or nonahydrate in a ratio by weight of 1:0.1 to 1:1.0.
2. Tablets as claimed in claim 1, characterized in that they contain a spray-dried granular alkaline detergent additive consisting of

   (a) 40 to 55% by weight and more particularly 45 to 52% by weight,

   (b) 30 to 45% by weight and more particularly 30 to 40% by weight,

   (c) 5 to 15% by weight and more particularly 5 to 10% by weight,

   (d) 2 to 6% by weight and more particularly 3 to 5% by weight.
3. Tablets as claimed in claims 1 and 2, characterized in that they contain 15 to 35% by weight of the spray-dried granular alkaline detergent additive.
4. Tablets as claimed in claims 1 to 3, characterized in that they contain 30 to 80% by weight of alkali metasilicate, including 5 to 30% by weight of sodium metasilicate pentahydrate, expressed as anhydrous alkali metasilicate, as the silicate.
5. Tablets as claimed in claims 1 to 4, characterized in that they contain 5 to 30% by weight, based on the alkali metasilicate as a whole, of sodium metasilicate nonahydrate, expressed as anhydrous alkali metasilicate.
6. Tablets as claimed in claims 1 to 5, characterized in that the ratio by weight of anhydrous sodium metasilicate to its penta- and/or nonahydrate is between 1:0.15 and 1:0.8.
7. Tablets as claimed in claims 1 to 6, characterized in that they contain 0.2 to 5% by weight of low-foaming nonionic surfactants.
8. Tablets as claimed in claims 1 to 7, characterized in that they contain 0.5 to 5.0% by weight of active chlorine donors as the bleaching agent.
9. Tablets as claimed in claims 1 to 8, characterized in that they contain 3 to 20% by weight of active oxygen carriers as the bleaching agent.
10. Tablets as claimed in claims 1 to 9, characterized in that they additionally contain 0.2 to 2% by weight of foam inhibitors.