GB2234980A - Detergent composition for machine dishwashers - Google Patents

Abstract

A detergent composition suitable for machine dishwashing contains a builder which comprises a mixture of a high molecular weight polymer and a low molecular weight polymer. The builder system, which may be polyacrylic polymers of maleic anhydride and acrylic acid, reduces deposits found in other non-phosphate built systems.

Description

DETERGENT COMPOSITION FIELD OF INVENTION The present invention relates to a detergent composition and, more particularly, to a very low or zero phosphate containing detergent composition suitable for use in a machine dishwasher.

BACKGROUND OF INVENTION Currently marketed detergent compositions contain as a builder large amounts of phosphate salts, e.g.

polyphosphates and orthophosphates. However, such phosphates are thought to be harmful to the environment.

They cause accelerated eutrophication of water, leading to ecological imbalances. Accordingly there is now a demand for detergent compositions which are low in or, preferably free of phosphates.

Builders are necessary in detergent compositions to sequester excess Ca2+ ions found in hard water. Ca2+ ions interfere with cleaning through interaction with certain ingredients of a dishwashing composition and through interaction with certain soils. Phosphate ions are very successful at this sequestration, but less harmful builders are required. Examples include zeolites, carbonates and polymers. In CA 1 007 948 (Colgate) there is a description of a builder system comprising alkali metal carbonate and citrate builder salts. US 4 244 832 (Kaneko) describes an automatic dishwashin composition which also involves carbonate and citrate.

One problem which arises from the use of carbonate in detergent formulations is the deposition of calcium carbonate on washed substrates. Even in formulations which contain only a low level or are free from carbonate, soluble bicarbonate present in the wash and rinse water can precipitate and deposit as carbonate as a result of heating or increasing the pH of the wash or rinse water.

Phosphates are very effective at preventing the growth of calcium carbonate crystals not only in the main wash but also in the intermediate and final rinses.

SUMMARY OF INVENTION We have now found that an effective builder for detergent compositions and in particular for machine dishwashing detergent compositions comprises a mixture of a high molecular weight polymer (i.e. MWt > 20,000) and a low molecular weight polymer (i.e. MWt < 10,000). The high molecular weight polymer functions to sequester Ca2+ ions and the low molecular weight polymer functions to prevent calcium carbonate crystal growth. The builder system may or may not contain another cobuilder such as zeolite, citrate, polyer or a carbonate salt and does not result in crystal formation.

DESCRIPTION OF INVENTION The builder system according to the present invention essentially comprises a mixture of two polymers types, one of high and one of low molecular weight. The polymers in each category may themselves be mixtures of other polymers. The high molecular weight polymer type has a molecular weight above 20,000, preferably 50-70,000.

Examples include polyacrylic copolymers of maleic anhydride and acrylic acid. Particularly preferred copolymers having a mixture of maleic anhydride and acrylic acid in ratios ranging from 20:80 to 80:20 % by weight.

The low molecular weight polymer type has a molecular weight below 10,000, preferably in the range of 1-5,000.

Examples include low molecular weight polyacrylates or copolymers as in the high molecular weight polymer.

The composition of the invention may furthermore comprise the usual ingredients of detergent compositions.

It may contain one or more non-phosphate alkali salts commonly used in dishwashing compositions. Thus, it may contain organic and/or inorganic builders such as the zeolites, silicates, carbonates, borates, citrates, carboxymethyloxysuccinates, nitrilotriacetates and ethylene diamine tetraacetates, polymeric polyelectrolytes such as polyacrylates, polymaleates, and other known organic and inorganic builder compounds, together with combinations thereof.

Usually, the amount of builders in the composition varies from 5-90% by weight, generally from 20-70% by weight in a solid composition, from 5-10% by weight in a liquid.

The composition may also contain a detergent-active compound. If a detergent-active compound is included, it is usally in an amount of from 0.5-10%, usually 1-5%. Any well-known type of detergent-active compound may be used, such as soaps, synthetic anionic, nonionic, or amphoteric detergent surfactants and mixtures thereof. Preferably, a nonionic detergent surfactant is used, especially a low-foaming one. Suitable examples of such nonionic detergent surfactants can easily be found in M Schick, "Nonionic Surfactants" (1967).

The composition may furthermore contain other useful additives such as bleaching agents, bleaching agent activators, hydrotropes, fillers, perfumes, colouring agents, germicides, soil-suspending agents, drainage-promoting agents, threshold agents, aminopolyphosphonic acids and alkali metal or alkaline earth metal salts thereof, clays such as hectorites, anti-corrosion agents such as fatty acids and benztriazole. Enzymes such as amylases, proteases, and lipases may also be included.

As bleaching agents the peroxygen type bleaching agents, preferably with a bleach precursor such as TAED are suitable for inclusion in the machine dishwashing compositions.

The composition of the present invention may be formulated as a powder, as a pourable aqueous or non-aqueous liquid or gel, as a tablet or cake, or in any other conventional form.

A typical example of a conventional powder machine dishwashing composition usually contains builders and co-builders in an amount of from 20-60%, an alkali metal metasilicate in an amount of from 40-80%, or an alkali metal disilicate in an amount of from 5-30% by weight, alkali metal carbonate 0-40% a peroxy type bleaching agent in an amount of from 1-15%, or a chlorine bleach in an amount equivalent to from 0.5-58 available chlorine a low-foaming detergent surfactant in an amount of from 0.5-5%, and minor ingredients such as perfumes, colouring agents, hydrotropes, fillers, etc.

A typical example of a conventional liquid machine dishwashing composition usually contains builder in an amount of from 5-10wt%, a bleach in an amount equivalent to from 0.5 to 5 wt% available chlorine and a thixotropic thickener in an amount of from 0.5 to 5 wt%, the balance being water. Minor ingredients as above may also be present.

The invention will now be further described with reference to the following non-limiting Examples.

Example 1 A machine dishwashing powder composition was formulated as follows: Wt % Sodium Metasilicate 52.0 Sodium Carbonate 31.0 High M.Wt Polymer 4.0 2 Low M.Wt Polymer 2.0 Sodium Chloride 6.5 Nonionic 0.5 Chlorine as NaDCCA 1.4 Clay 2.5 Salts to 100.0 High M.Wt Polymer : Sokalan CP5 (BASF) - a 70,000 M.Wt copolymer of maleic anhydride and acrylic acid (30:70 wt ratio) 2 Low M.Wt Polymer : Acrysol LMW 45D (Rohm & Haas) - a 4,500 M.Wt polyacrylate 3 Nonionic Dehypon LT 54 (EO/PO block nonionic from Henkel) Example 2 A liquid machine dishwashing composition was formulated as follows: Wt % Sodium Disilicate 20.0 Clay (Laponite RD or XLS) 3.5 High M.Wt Polymer4 4.0 5 Low M.Wt Polymer 2.0 Hypochlorite as Av. C1 1.2 Water to 100.0 High M.Wt Polymer : Sokalan CP5 as Example 1 Low M.Wt Polymer : Alcosperse 602N (Alco) - a 6,000 M.Wt Polymer Example 3 A machine dishwash powder formulation was formulated as follows: Wt % Sodium metasilicate 61.0 Trisodium citrate dihydrate 20.0 High M.Wt polymer 4.0 Low M.Wt polymer 2.0 KDCC 2.1 Nonionic LF403 1.0 Salts to 100.0 Example 4 A machine dishwash powder formulation was formulated as follows: Wt % Sodium disilicate 20.0 Trisodium citrate dihydrate 20.0 Hogh M.Wt polymer 4.0 Low M.Wt polymer 2.0 TAED 2.5 Perborate Mono 4.0 Enzymes 2.0 Nonionic LF403 1.0 Salts to 100.0

Claims (5)

1. CLAIMS: 1. A detergent composition adapted for use in a machine dishwasher and essentially free of phosphate builder comprises from 1 to 20 wt% of a polymer having a molecular weight above 20,000 and from 1 to 20 wt% of a polymer having a molecular weight below 10,000.
2. 2. A detergent composition as claimed in claim 1 wherein the high molecular weight polymer is a polyacrylic polymer of maleic anhydride and acrylic acid.
3. 3. A detergent composition as claimed in claim 1 or claim 2 wherein the low molecular weight polymer is a polyacrylic polymer of maleic anhydride and acrylic acid.
4. 4. A composition as claimed in any one of the preceding claims further comprising from 10 to 70 wtt of an alkali-metal carbonate.
5. 5. A composition as claimed in claim 1 substantially as hereinbefore described and with particular reference to the examples.