EP0512371B1 - Granular phosphate-free agents for automatic dishwashing - Google Patents

Abstract

An environmentally friendly, granular, phosphate-free dishwashing agent for automatic dishwashers is proposed with alkali metal gluconate as phosphate substitute. It contains: 10 - 70% by weight of water-soluble alkali metal silicate with a ratio of silicon dioxide to alkali metal oxide greater than 1:1; 0 - 50% by weight of alkali metal carbonate; 2 - 15% by weight of polymeric sequestrants or dispersants, preferably of the polycarboxylate type, especially homopolymers of acrylic acid or copolymers with other organic acids or ethers which contain vinyl groups, especially maleic acid; 3 - 15% by weight of alkali metal salts of acids obtained from sugars by fermentation, especially of Glu acid or lactobionic acid; 2 - 15% by weight of an oxygen-based bleach from the group of peroxo compounds or peroxohydrates or mixtures thereof, which liberate hydrogen peroxide in water; 0 - 15% by weight of a bleach activator from the group of compounds which liberate reactive peracids, especially peracetic acid, on exposure to hydrogen peroxide; 0 - 2% by weight of an alkali metal salt of a phosphonic acid to stabilise the bleach during storage; 0 - 5% by weight of enzymes or enzyme mixtures from the group of hydrolases, especially proteases, amylases and lipases; 0.5 - 5% by weight of a low-foam nonionic surfactant. d

Description

The invention relates to a granular phosphate-free agent for automatic dishwashing.

Conventional dishwashing detergents for the dishwasher essentially consist of the components alkali tripolyphosphate, alkali metasilicate and alkali carbonate. In addition, organic additives such as non-foaming surfactants, polycarboxylates (homopolymers of acrylic acid or copolymers with maleic acid), chlorine releasers (e.g. sodium dichloroisocyanurate) are used.

Recent developments aim to replace phosphate in order to reduce the eutrophication of surface waters.

In addition to this ecological side, toxicology is also important. Legal measures mean that from the middle of 1991, highly alkaline products in Germany may only be brought onto the market in child-resistant packaging. In other countries, this law was passed some time ago. This led to the development of dishwashing detergents with reduced alkalinity in order to reduce the risk to consumers, especially children, without, on the other hand, increasing the waste problem due to the more complex packaging. At the same time, the new cleaners do without chlorine compounds.

DE-AS 21 49 251, DE-OS 21 62 673 and DE-OS 24 35 479 already describe phosphate-free compositions for automatic dishwashing, which include as important components polycarboxylates and polycarboxylic acids, e.g. Citric acid or tartaric acid, and some are phosphate-free.

The new generation of dishwashing detergents that have recently been on the German market are based on trisodium citrate combined with polycarboxylates as the most important phosphate substitute. The use of citrate became possible because its calcium binding power is much better in combination with sodium disilicate than with the more alkaline sodium metasilicate. In addition, these dishwashing detergents contain nonionic non-foaming surfactants, polycarboxylates, enzymes, oxygen-based bleaches (for example sodium perborate) and bleach activators such as TAED.

Agents that contain zeolite A as a replacement for the phosphate are also recommended as environmentally friendly alternatives. However, these insoluble substances can lead to the formation of white deposits. In addition, the problem of cooking on the dishes made of crystallized calcium carbonate cannot be solved, since the insoluble zeolite A acts as an ion exchanger and can only bind the dissolved water hardness. Precipitated calcium carbonate cannot be brought back into solution sufficiently.

Furthermore, complexing agents such as e.g. NTA or EDTA, recommended as a hardness binder. The present test material shows that formulations containing these substances actually show excellent properties in the removal of tea. Here it is particularly important to destroy the complex of the tea dye with calcium ions. However, the use of these compounds is ecologically questionable, since there is a fear of remobilization of heavy metals from the sediments of surface waters. The use of larger amounts of phosphonates as complexing agents is also not advisable from an ecological point of view.

The present invention has for its object to provide a granular, phosphate-free dishwashing detergent for the dishwasher, the phosphate substitutes of which contribute as little as possible to water pollution. In addition, with reduced hazard potential for the consumer, the flushing performance according to DIN 44 990 should at least correspond to the IEC standard cleaner.

According to the invention, this object is achieved by the characterizing features of claim 1. Due to the low proportion of organic compounds, the pollution of the water by the detergent according to the invention is extremely low.

The use of sodium gluconate in a highly alkaline medium is known. In highly alkaline industrial cleaners, e.g. used in bottle washing, polyphosphates are subject to strong hydrolysis, especially at elevated temperatures; at the same time, the complex formation constant with calcium ions drops drastically, so that the effects of phosphates are severely impaired. Here the sodium gluconate shows very strong advantages because it is not hydrolyzed and its complex formation constant with calcium ions increases with increasing pH. At pH values below 12.5, the stability of the complex is reduced, and below this, calcium salts precipitate in the temperature range of 65 ° C of interest.

Surprisingly, an alkali metal gluconate, in particular sodium gluconate, can play a decisive role as a phosphate substitute in the compositions of the present invention in spite of the low pH (9.5-11) even in low doses. Similar effects can also be achieved with lactose derivatives, such as the salts of lactobionic acid. The combination according to the invention of a polycarboxylate (polyacrylate or copolymers with maleic acid), preferably copolymers with sodium disilicate (ratio SiO ₂ : Na ₂ O is 1.7: 1 to 2.3: 1) and sodium gluconate, shows a superior effect compared to formulations based on citrate . Likewise, the use of layered silicates known from DE-OS 36 27 773 is also possible since, apart from the lack of crystal water, they have a stoichiometry corresponding to the amorphous disilicate.

It is particularly surprising that the addition of sodium carbonate significantly improves the cleaning performance. To stabilize the active oxygen compound, a small proportion of phosphonate, e.g. HEDP, are used. In all sodium compounds, the sodium can of course also be replaced by other alkali metals. However, this is an economic question.

Biodegradable polypeptides that are obtained from natural sources are also used as the polymeric sequester. Such products derived from fishing waste, e.g. extracted from mussels are available under the trademark Cygnus from Cygnus Corporation, Illinois (USA).

In addition to the very good cleaning performance over the entire spectrum of the soiling of the composition according to DIN 44 990, the very good inhibition of deposit formation should also be emphasized. Fluctuating water quality and a water softener (ion exchanger) that is not always fully working in the dishwasher can lead to pronounced deposits of crystalline alkaline earth metal silicate, such as calcium and magnesium silicate, especially in detergent formulations that contain large amounts of alkali silicates. These white to gray deposits are particularly unpleasant on the inside of the dishwasher, on glasses and on stainless steel parts such as cutlery. Such deposits preferably occur in phosphate-free formulations if the calcium or magnesium is not sequestered sufficiently. The machine dishwashing detergent according to the invention surprisingly shows very good deposit prevention, although it contains neither hard complexing agents, such as NTA or EDTA, nor softer complexing agents, such as citric acid.

Since sodium citrate, like the complexing agent NTA already mentioned, forms a 1: 1 adduct with the calcium ions, equimolar amounts are necessary to bind the water hardness. Therefore sodium citrate is mostly used in higher percentages. Formulations up to more than 40% by weight of citrate are not uncommon. The biodegradation of citrate in the wastewater treatment plant is extremely quick, but the biological oxygen demand is high, especially with the necessary high proportions in the cleaners. In contrast, the dishwasher detergent according to the invention for the dishwasher manages with a fraction of sodium gluconate compared to citrate. With comparable degradability of the gluconate, which also occurs naturally, there is a significantly reduced oxygen requirement due to the lower amount used, since the wastewater pollution with organic substances is greatly reduced. The total proportion of organic substances, apart from the enzymes, is only a little more than 14% by weight in the formulation according to the invention. The inorganic substances sodium disilicate and sodium carbonate used can be regarded as ecologically harmless.

The cleaning effect can be very specifically improved in the combination of soda / disilicate / polycarboxylate / gluconate according to the invention with enzymes. In particular, hydrolases, preferably amylases and proteases, but also lipases, with very good activity are to be used in the composition according to the invention.

Since enzymes from active chlorine in the wash liquor are broken down very quickly and are therefore ineffective, the bleaching agent in the present cleaner consists of an active oxygen compound. Here e.g. Peroxo compounds or peroxohydrates, e.g. Alkali perborate, alkali carbonate, peroxohydrate, alkali peroxosulfate, hydrogen peroxide, urea, preferably sodium perborate monohydrate, are used. Since household dishwashers currently work in the range of 40 - 65 ° C, oxygen bleaching can be carried out by an activator, e.g. from the group of compounds, which split off peracetic acid under the action of hydrogen peroxide. The TAED is particularly worth mentioning here.

It is known that surfactants lower the surface tension and contribute to better wetting. Non-foaming or low-foaming surfactants are particularly advantageous in dishwashers because they suppress the foam generated by the spray arm. Biodegradable fatty alcohols with EO / PO chains have proven their worth here.

However, biodegradable anionic surfactants which are derived from glycine have also proven to be advantageous in the agent according to the invention. These polycarboxyglycinates of the general formula R- (N- (CH2) 3-CH2COONa) n-CH2COONa additionally contribute to the questing of the water hardness due to their nitrogen atoms. R here stands for a fatty alkyl residue, such as tallow fat.

Preferred recipes are the subject of the dependent claims. Regarding claim 2, it should be noted that the rate of dissolution in water can be delayed, as is the case with crystalline layered silicate. In particular, granular amorphous sodium disilicate shows a positive behavior.

Additives customary for such cleaners, such as e.g. Fragrances and dyes, defoamers, pouring aids, extenders and extenders are added. However, they do not contribute to the cleaning effect, but can influence consumer acceptance or improve the storage stability of the formulation.

Buffer substances can also be added to regulate the pH. The inorganic hydrogen carbonates or sesquicarbonates are particularly worth mentioning here. But also organic compounds, e.g. Alkaline acetates, which make little contribution to cleaning performance, can serve this purpose. These buffers can adjust the pH to a lower level so that the agent no longer has to be classified as an irritant or meets even the strictest legal requirements.

Below are examples of the formulations according to the invention in a table, a standard cleaner being specified under IEC. The compositions are given in% by weight. Example 1 is a known agent, while Examples 2-8 relate to compositions according to the invention.

As the examples given show, when the composition according to the invention is used with the same dosage of 25 g, a much better washing result is achieved than with the IEC standard cleaner. In particular, very stubborn, starchy dirt, such as oatmeal, is removed very well. But also the spinach, which can only be removed by sufficient dispersing and emulsifying effects of the cleaner, is removed very well.

In addition to the low content of organic compounds in the cleaner according to the invention, the environmental impact is reduced by a much lower dosage in the dishwasher. Depending on the degree of soiling, water quality and condition of the dishwasher, the amount used can be reduced by up to 50% compared to conventional cleaners.

It is found to be particularly advantageous in the dishwashing detergent according to the invention that the use of organic components for the dishwasher is considerably reduced with very good cleaning performance over all soiling in accordance with DIN 44990 and at the same time preventing deposits on machine parts and dishes. Since the present composition also contains no phosphate and shows very similar results with very low doses - up to 50% less than conventional cleaners - a noticeable environmental relief is achieved.

Claims (12)

1. Granular phosphate-free agents for automatic dishwashing, characterized by a combination of:

   10 - 70 % by weight   water soluble alkali silicate, with a silicium dioxide/alkali oxide ratio greater than 1:1;

   0 - 50 % by weight   alkali carbonate;

   2 - 15 % by weight   polymeric sequestering agents and/or dispersing agents, preferably of the polycarboxylate type, especially homopolymers of acrylic acid or copolymers with other organic acids or ethers containing vinyl groups, especially maleic acid;

   3 - 15 % by weight   alkali salts from acids prepared from sugars by fermentative action, especially glutamic acid or lactobionic acid;

   2 - 15 % by weight   of an oxygen-based bleaching agent from the group of peroxo compounds or peroxo hydrates or mixtures thereof that set free nitrogen peroxide in water;

   0 - 15 % by weight   of a bleaching activator from the group of compounds that set free reactive peracids, especially per-acetic acid, under the action of nitrogen peroxide;

   0 - 2 % by weight   of an alkali salt of a phosphonic acid to stabilise the bleaching agent during storage;

   0 - 5 % by weight   enzymes or enzyme mixtures from the group of hydrolases, especially proteases, amylases and lipases;

   0.5 - 5 % by weight   of a low-foam, non-ionic tenside.
2. Dishwashing agent according to claim 1, characterized by a content of alkali silicate with a silicium dioxide/alkali oxide ratio of 1.7:1 up to 2.3:1;
3. Dishwashing agent according to claim 1, characterized in that alkali perborate or alkali percarbonate is used as a bleaching agent.
4. Dishwashing agent according to claim 1, characterized in that the bleaching activator is TAED (tetraacetylethylene diamine).
5. Dishwashing agent according to claim 1, characterized in that copolymers of acrylic acid are used as polycarboxylates and maleic acid is used as sodium salt.
6. Dishwashing agent according to claim 1, characterized in that biologically degradable polypeptides are used as polymeric sequestering agents.
7. Dishwashing agent according to claim 1, characterized in that nonvolatile, highly active phlegmatising peroxocarbonic acids, especially diperoxododecanedioic acid, are used as oxygen-based bleaching agent.
8. Dishwashing agent according to claim 1, characterized in that for adjusting the pH value at least some of the alkali carbonate is used as sesquicarbonate or alkalihydrogen carbonate.
9. Dishwashing agent according to claims 1 to 5, characterized by:

   25 - 60 % by weight,   especially % 40 - 50 by weight, amorphous sodiumdisilicate with a SiO₂:Na₂O ratio of 1.9:1 to 2.1:1;

   10 - 40 % by weight,   especially 25 - 35 % by weight, sodium carbonate;

   3 - 10 % by weight,   especially 4 - 8 % by weight, polyacrylate maleinate (7:3) as sodium salt;

   3 - 10 % by weight,   especially 4 - 7 % by weight, sodium gluconate;

   5 - 15 % by weight,   especially 5 - 10 % by weight, sodium perborate-monohydrate;

   0 - 15 % by weight,   especially 3 - 7 % by weight, TAED (tetraacetylethylene diamine);

   0 - 2 % by weight,   especially 0.2 - 0.5 % by weight, HEDP (hydroxiethane-1, 1-diphosphonic acid) as sodium salt;

   0 - 5 % by weight   of a mixture of stabilised enzymes, especially proteases, amylases and lipases;

   0 - 5 % by weight   low-foam, non-ionic tensides.
10. Dishwashing agent according to claims 1 and 9, characterized in that fatty alcohols with EO/PO chains are used as low-foam, non-ionic tensides.
11. Dishwashing agent according to claims 1 and 9, characterized in that tensides of the fatty alkyl polycarboxyglycinate type, especially tallow alkyl polycarboxyglycinate, are used as sodium salt.
12. Dishwashing agent according to claims 1, 8 and 9, characterized in that the silicates and carbonates are used as mixed granulates (precompound).