NO173612B - CURRENT, TIKSOTROP, Aqueous, Liquid Dishwashing Mixture - Google Patents

Description

The present invention relates to a gel-like, thixotropic, aqueous, liquid detergent mixture for dishwashers, with improved anti-film formation and anti-stain properties for use in washing crockery, glassware, porcelain and the like. The washing-up liquid contains alumina or titanium dioxide as an anti-film-forming agent, polyacrylic acid polymer builder, inorganic builder salts, chlorine bleach, bleach-stable detergent and a thixo-

tropted thickener.

The dishwashing liquid according to the present invention reduces film formation and spotting on tableware,

glassware, porcelain and the like, especially in hard water, and remains stable against phase separation.

More specifically, the invention involves application

of aluminum or titanium dioxide as anti-film-forming

agent and polyacrylic acid polymer builder in thixotropic, aqueous, liquid dishwashing detergents to reduce film formation and staining.

The detergents do not require an added rinse aid, are stable when stored, do not precipitate and are easily redispersible and are pourable.

The detergent mixture according to the invention is a thixotropic, aqueous suspension with improved physical stability. The invention involves the use of long-chain fatty acids with 8-22 carbon atoms or metal salts thereof as thixotropic agents for the formation of stable, gel-like, liquid suspensions suitable for use as liquid detergents in automatic dishwashers.

The present invention relates in particular to

aqueous, liquid detergents for automatics

dishwashers that have thixotropic properties, improved anti-film formation and anti-spotting properties, and improved properties with regard to physical stability, which are easily dispersible in the washing medium so that crockery, glassware, porcelain and the like are effectively cleaned.

Commercially available detergents for household machines, supplied in powder form, have several disadvantages, e.g. non-uniform composition; expensive operations necessary in the manufacture; tendency to agglomerate when stored at high humidity, which results in the formation of lumps which are difficult to disperse; dustiness, a source of particular irritation for users suffering from allergies; and propensity for clumping in the dishwasher dispenser. However, liquid forms of such mixtures cannot generally be used in automatic dishwashers due to high foam levels, unacceptably low viscosities and very high alkalinity. In addition, the currently used powder detergents often require a separate step of towel rubbing and drying of crockery, glassware, porcelain and the like to avoid unwanted traces or film of precipitated calcium and magnesium salts being left behind. The use of liquid detergent mixtures presents other problems. The building salts precipitate during storage and are not easily redispersed. The mixtures often also thicken during storage and are not easy to pour.

Recent research and development activity has focused on the gel form or "thixotropic" form of such mixtures, however, such mixtures have generally been found to be insufficiently viscous to remain "anchored" in the dispenser container of the dishwasher, and also produce stain residues on crockery, glassware, porcelain and the like. Ideally, thixotropic cleaning compositions should be highly viscous in a quiescent state, Bingham plastic in nature and have relatively high yield stresses. However, when subjected to shear stress, such as being shaken in a container or squeezed out through an orifice, they should rapidly fluidize and, upon cessation of the applied shear stress, rapidly return to the highly viscous/Bingham plastic state. Stability is also of primary importance, i.e. there should be no significant signs of phase separation or leaching after a long standstill.

For effective use, it is generally recommended that the detergent for automatic dishwashers, hereinafter also referred to as ADD, contain (1) sodium tripolyphosphate (NaTPP) to soften or dissolve hard water minerals and to emulsify and/or peptize soil; (2) sodium silicate to provide the necessary alkalinity for effective washing action, and to provide protection for glaze and pattern on fine porcelain; (3) sodium carbonate, generally considered to be an eventuality, to increase alkalinity; (4) a chlorine-releasing agent to aid in the elimination of dirt stains that lead to water staining; and (5) defoamer/surfactant to reduce foam, thereby increasing machine efficiency and providing required washing performance. See e.g. SDA Detergents in Depth, "Formulations Aspects of machine Dishwashing", Thomas Oberle (1974). Cleaning agents that come up against the above-described mixtures are mostly liquids or powders. In general, hypochlorite bleach is omitted in such mixtures as it tends to react with other chemically active ingredients, particularly surfactant, thereby breaking down the suspending or thixotropic agent and reducing its effectiveness.

In US Patent No. 3,985,668, abrasive scouring agents of a gel-like consistency are thus described which contain (1) suspending agent, preferably clay of the smectite and attapulgite types; (2) abrasive, e.g. silica sand or perlite; and (3) fillers comprising powdered low-density polymers, expanded perlite, and the like, which have a buoyancy and thereby stabilizing effect on the mixture in addition to serving as a bulking agent, thereby replacing water that would otherwise be available to unwanted supernatant layer formation due to leaching and phase destabilization. The above mentioned are the essential components. Optional ingredients include hypochlorite bleach, bleach-stable surfactant and buffer, e.g. silicates, carbonates and monophosphates. Builders, such as NaTPP, may be included as further possible components to provide or supplement building function not provided by the buffer, as the amount of such builders does not exceed 5% of the total mixture, according to the patent document. Maintenance of the desired levels of (greater than) pH 10 is achieved by means of the buffer/builder components. High pH is said to minimize decomposition of chlorine bleach and unwanted reaction between surfactant and bleach. When NaTPP is present, it is limited to 5% as indicated. Defoamer is not described.

In GB Patent Applications Nos. 2,116,199A and 2,140,450A

liquid ADD mixtures have been described with properties which are desirably characteristic of gel-type thixotropic structure and which comprise each of the various components which are necessary for effective washing action in a

automatic dishwasher. The normally gel-like, aqueous detergent for automatic dishwashers with thixotropic properties comprises the following components by weight:

(a) 5 - 35% alkali metal tripolyphosphate,

(b) 2.5 - 20% sodium silicate,

(c) 0-9% alkali metal carbonate,

(d) 0.1 - 5% chlorine bleach stable, water dispersible, organic, detergent active material,

(e) 0 - 5% chlorine bleach stable antifoam,

(f) chlorine bleach compound in an amount to provide 0.2 - 4% available chlorine, (g) thixotropic thickener in an amount sufficient to give the mixture a thixotropy index of 2.5 - 10, and (h) sodium hydroxide as needed to adjust pH .

ADD mixtures prepared in this way are low-foaming, easily soluble in the washing medium and most effective at pH values that best provide improved cleaning effect, i.e. pH 10.5-13.5. The mixtures normally have a gel consistency, i.e. a highly viscous, opaque, gel-like material with a Bingham-plastic character and thus relatively high yield stresses. Consequently, a certain shear force is required to start up or increase flow, such as would be achieved in the agitated dispenser container of an activated automatic dishwasher or a stream of water. Under such conditions, the mixture fluidizes quickly and dispenses easily. When the shearing force is interrupted, the liquid,^ mixture rapidly returns to a highly viscous, Bingham-plastic state close to its former consistency.

US Patent No. 4,511,487 describes a low-foaming detergent paste for dishwashers. The agent is based on a mixture of finely divided, hydrated sodium metasilicate, an active chlorine compound and a thickener which is a shale silicate of the hectorite type. A small amount of nonionic surfactants and alkali metal carbonates and/or hydroxides may be used.

Reference is made to a related Norwegian patent document

No. 167,517. This patent document describes a thixotropic, aqueous detergent for automatic dishwashers which contains a long-chain fatty acid as a thixotropic thickener.

Reference is also made to US Patent No. 4,857,226. This patent document describes an aqueous, liquid, thixotropic, clay-containing washing-up agent which comprises a metal salt of a long-chain fatty acid and a polyacrylic acid polymer or a salt thereof as a stabilizer.

The thixotropic detergent mixtures according to

within the state of the art associated with powder and liquid detergents. Due to the addition of a small effective amount of an alumina or titanium dioxide anti-filming agent, and polyacrylic acid polymer or salt builder to the mixture, no added rinse aid is required, and towel rubbing and drying is not required to achieve dry, shiny , clean crockery, glasses, cups and cutlery. The thixotropic, aqueous, liquid detergent has the further advantages of being stable, non-precipitating during storage and easily redispersible. The liquid mixtures according to the present invention are easy to pour, easy to measure out and easy to place in dishwashers.

A further and unexpected advantage of adding the alumina or titanium dioxide anti-film forming agent to the detergent mixture is that the aluminum or titanium dioxide inhibits the formation of brown color in the dishwasher. The brown color is formed by the deposition in the dishwasher of iron and/or manganese oxides. The formation of tan is a particularly serious problem in areas with hard water. Alumina or titanium dioxide in the mixture acts on the iron and/or manganese in the washing water so that their deposition in the dishwasher as iron and/or manganese oxides is prevented.

It is an object of the present invention to provide a thixotropic, aqueous, liquid detergent for automatic dishwashers which has improved anti-film formation and anti-staining properties.

It is another object of the invention to provide a thixotropic, aqueous, liquid detergent which is stable during storage, easily pourable and easily dispersible in the washing-up water.

Crockery, glassware, porcelain and the like are washed in an automatic dishwasher using a thixotropic, aqueous, liquid detergent where a separate rinsing aid is not added or required.

Crockery, glassware, porcelain and the like are washed in an automatic dishwasher using an aqueous, liquid detergent, as the crockery, glassware, porcelain and the like are machine dried without leaving traces or a film.

It is a further object of the invention to provide stable, aqueous, thixotropic, liquid detergent compositions for automatic dishwashers, by incorporating into the aqueous suspension a small, effective amount of an alumina or titanium dioxide anti-film forming agent and polyacrylic acid polymer or salt builder. A smaller amount of a fatty acid, a metal salt of a fatty acid and/or clay is also added as a thixotropic thickener which effectively inhibits the precipitation of the suspended particles and prevents phase separation.

These and other objects of the invention will be more easily understood from the detailed description of the invention below, and preferred embodiments thereof are achieved by incorporating into an aqueous, liquid detergent mixture a small but effective amount of an alumina or titanium dioxide anti-film forming agent and polyacrylic acid polymer - or salt builder. The physical stability of the mixture is improved by adding a fatty acid, a metal salt of a fatty acid and/or a clay as a thixotropic thickener. More specifically, the invention provides a normal gel-like detergent for automatic dishwashers in which from 0.5 to 5% of an alumina or titanium dioxide anti-film forming agent and 2 - 14% of a water-soluble polyacrylic acid polymer or salt builder are incorporated. The alumina or titanium dioxide anti-film forming agent has a particle size of 0.1 - 10 micrometers. The water-soluble polyacrylic acid or its salt has a molecular weight of 1,000 - 100,000. According to the invention, a sufficient amount of a fatty acid with 8-22 carbon atoms or a polyvalent metal salt thereof is added to the mixture as a thixotropic thickener to give a thixotropy index of 2.5 - 10, and to inhibit precipitation of the suspended particles, such as alkali metal building salts, etc. .

Thus, the present invention provides a gel-like, thixotropic, aqueous, liquid dishwashing detergent mixture which is characterized by the fact that, based on weight, it comprises:

(a) 5 - 35% detergent builder,

(b) 2.5 - 40% sodium silicate,

(c) 0.5 - 5% of an alumina or titanium dioxide antifilm forming agent with a particle size of 0.1 - 10 µm, (d) 2 - 14% polyacrylic acid polymer or polyacrylic acid polymer salt builder of the formula

where Rlf R2 and R3 can be the same or different, and is hydrogen or Cx-C« lower alkyl, M is hydrogen or an alkali metal, n = 5 - 1000, and the polymer has a molecular weight of 1000 - 100000,

(e) 0 - 9% alkali metal carbonate,

(f) 0.1 - 5% chlorine bleach stable, water dispersible, organic, detergent active material,

(g) 0 - 5% chlorine bleach stable antifoam,

(h) chlorine bleach compound in an amount providing 0.2 - 4% available chlorine, (i) a sufficient amount of a thixotropic fatty acid of 8-22 carbon atoms or polyvalent metal salt thereof, to give a thixotropy index of 2.5 - 10,

(j) 0 - 8% sodium hydroxide, and

(k) the rest water.

In connection with the application, dishes are washed in an automatic dishwasher with an aqueous wash bath containing an effective amount of a liquid detergent mixture for automatic dishwashers (LADD) as described above. In use, the LADD mixture can be easily poured into the dispenser container of the automatic dishwasher and will, within a few seconds, instantly thicken to its normal gel-like or paste-like state, remaining securely within the dispenser container until shear forces are re-applied, such as with the water jet from the dishwasher.

The invention will now be described in more detail by

using certain embodiments thereof.

The LADD products according to e.g. the earlier disclosures in the aforementioned GB Patent Applications Nos. 2,116,199A and 2,140,450A exhibit rheological properties as evaluated by testing product viscosity as a function of

of shear rate. The mixtures showed higher viscosity at a lower shear rate and lower viscosity at a high shear rate, the data indicating effective fluidization and gelation well within the shear rates found in a standard dishwasher. In practice, this means improved properties with respect to slope and

processing, as well as less leakage in the machine's dispenser container, compared to previously known liquid or gel ADD products. For applied shear rates corresponding to 3-30 rpm, viscosities (Brookfield) ranged correspondingly from 10,000 - 30,000 eps to 3,000 - 7,000 eps, measured at room temperature using an LVT Brookfield viscometer after 3 minutes using a No. 4 spindle. A shear rate of 7.4 sec<-1> corresponds to a spindle rpm of approx. 3. An approximate 10-fold increase in cutting speed gives approx. a 3- to 9-fold reduction in viscosity. The mixtures according to the state of the art thus exhibit threshold fluidizations at lower shear rates and to a significantly greater extent with respect to stepwise increases in shear rate in relation to stepwise decreases in viscosity. This property of the LADD products according to the previous invention is summarized as a thixotropy index (TI) which is the ratio between apparent viscosity at 3 rpm and at 30 rpm. The previously known mixtures have a TI of 2 - 10. The LADD mixtures should exhibit significant and rapid return to the previous consistency in the resting state when the shear force is interrupted.

With respect to apparent viscosity, it has been confirmed that as long as the viscosity at room temperature (22° - 1°C) measured in a Brookfield viscometer HATD using a No. 4 spindle at 20 rpm, is less than approx. 20,000 eps, the mixture can be easily shaken so that a thixotropic mixture can be easily "fluidized" or "liquefied" to enable the product to be dispensed through a conventional squeeze bottle or other suitable dispenser.

The present invention is based on the surprising discovery that substantially improved anti-film-forming and anti-staining properties can be achieved by adding to the thixotropic, aqueous, liquid detergent a small, effective amount of an alumina or titanium dioxide anti-f foaming agent and polyacrylic acid polymer or salt builder. The physical stability, i.e. resistance to phase separation, precipitation, etc., can be achieved by adding to the mixture a small, effective amount of a thixotropic thickener and stabilizer.

The alumina or titanium dioxide antifilm forming agent materials that can be used are readily available commercially. The alumina material which can be used as an anti-film forming agent is insoluble in water and has the formula Al,,)^. Suitable materials are available under the trade names "Aluminum Oxide C", Degussa and "Catapal D", Vista. A preferred alumina material is "Aluminum Oxide C".

The particle size of the alumina and titanium dioxide material used is important to achieve the desired anti-filming properties.

The alumina or titanium dioxide particles used are finely divided and can have a particle size of 0.10 - 10 micrometres, preferably 0.50 - 8 micrometres and preferably 1.0 - 5.0 micrometres.

The finely divided alumina or titanium dioxide material particles in the dishwater act to coagulate proteinaceous, particulate dirt and hold them in suspension, and the polyacrylic acid polymer or its salt acts as an anti-redeposition agent that prevents them from being deposited on the clean glassware and tableware.

Without it being intended to limit the invention to

somehow, the alumina and titanium dioxide anti-film forming agents are believed to work in the following manner. The glass surface of glassware contains negative charges on the surface through the Si-0 bonds. Normally the oxygen atoms carry these charges. It is postulated that these negatively charged ions will attract positively charged particles and thereby form a layer of "artificial dirt". The protective layer will then repel common food dirt and will increase the anti-redeposition properties of the detergent for automatic dishwashers. The alumina and titanium dioxide particles will generate positively charged particles that will bind to the glassware

the surface so that the artificial layer of dirt is formed which will prevent the formation of a film.

The amount of alumina and titanium dioxide anti-film forming agent that can be used to achieve the desired improvement in film formation and spot formation will depend on the hardness of the water, the detergent active compound, the inorganic salts and the other ADD ingredients.

The aluminum and titanium dioxide anti-film forming agent is particularly effective in hard washing water with e.g. 300 ppm hardness or more.

The amount of alumina or titanium dioxide anti-film forming agent used is 0.5-5% by weight, preferably 1-4% by weight, and most preferably 1.5-3% by weight based on the weight of the entire mixture.

Alumina and titanium dioxide can each be used alone or can be used mixed together. When the anti-film forming agents are used in a mixture, the weight percentage amounts mentioned above are the total weight percentage of the ingredients in the mixture.

The polyacrylic acid polymers and their salts that can be used are generally commercially available and are briefly described as follows:

The polyacrylic acid polymers and their salts used include water-soluble polymers of low molecular weight and with the formula

where R 1 R 2 and R 3 may be the same or different, and may be hydrogen, C 1 -C 2 lower alkyl or mixtures thereof. The value of n is 5 - 1,000, preferably 10 - 500, and preferably 20 - 100. M is hydrogen or an alkali metal salt such as sodium or potassium. The preferred substituent for M is sodium.

The preferred R 1 / R 2 and R 3 groups are hydrogen, methyl, ethyl and propyl. Preferred acrylic acid monomer is one where R 2 - R 3 are hydrogen, e.g. acrylic acid, or where Rj and R3 are hydrogen, e.g. acrylic acid, or where Ri and R3 are hydrogen and R2 is methyl, e.g. methylacrylic acid monomer.

The degree of polymerization, i.e. the value of n, is generally determined by the limit corresponding to the solubility of the polymer in water. The terminal groups or end groups of the polymer are not of decisive importance and can be H, OH, CH3 or a low molecular weight hydrocarbon.

The polyacrylic acid polymers and their salts have a molecular weight of 1,000 - 100,000, preferably 1,500 - 50,000 and particularly preferably 2,000 - 10,000.

Certain polyacrylic acid polymers which may be used include the "Acrysol LMW" acrylic acid polymers, such as "Acrysol LMW-45NX", a neutralized sodium salt having a molecular weight of about 4,500, and "Acrysol LMW-20NX", a neutralized sodium salt which has a molecular weight of approx. 2,000. The low molecular weight acrylic acid polymers can e.g. have a molecular weight of 1,000 - 10,000. Another polyacrylic acid polymer that can be used is "Alcosperse 110" which is a sodium salt of an organic polycarboxylate and which has a molecular weight of approx. 100,000.

The above-mentioned polyacrylic acid polymers and salts thereof can be prepared using methods known in the art, see e.g. US Patent No. 4,203,858.

The amount of polyacrylic acid polymer or polyacrylic acid polymer salt builder that can be used to achieve the desired improvement in anti-film forming and anti-staining properties will depend on the hardness of the water, the detergent active compound, the inorganic salts and the other ADD ingredients.

The polyacrylic acid or polyacrylic acid salt builder is particularly effective when it comes to reducing staining in hard water with e.g. 300 ppm hardness or more.

In general, the amounts of the polyacrylic acid polymer or its salt that can be used are in the range from 2.0 to 14%, preferably from 3.0 to 12%, particularly preferably 4 - 10%.

The thixotropic thickeners or suspending agents which can be used according to the present invention for providing the aqueous medium with thixotropy properties are fatty acid or polyvalent metal salts of fatty acid. The thixotropic thickeners should be stable to high alkalinity and stable to chlorine bleach compound, such as sodium hypochlorite. The thixotropic thickeners include the fatty acids and the polyvalent metal salts of the fatty acids. The amount of thixotropic thickener used will depend on the particular thickener used, but sufficient thickener is added to the mixture to give it a thixotropy index of 2.5 - 10.

The fatty acids used as thixotropic thickeners are the higher aliphatic fatty monocarboxylic acids with from 8 to 22 carbon atoms, preferably from 10 to 20 carbon atoms, and particularly preferably from 12 to 18 carbon atoms, including the carbon atom in the carboxyl group of the fatty acid. The aliphatic radical can be saturated or unsaturated and can be straight chain or branched. Straight-chain, saturated fatty acids are preferred. Mixtures of fatty acids may be used, such as those obtained from natural sources, such as tallow fatty acid, coconut fatty acid, soy fatty acid, etc., or from synthetic sources available from industrial manufacturing processes.

Examples of the fatty acids that can be used as thickeners include e.g. decanoic acid, lauric acid, dodecanoic acid, palmitic acid, myristic acid, stearic acid, oleic acid, eicosanoic acid, tallow fatty acid, coconut fatty acid, soya fatty acid and mixtures of these acids. Stearic acid and mixed fatty acids, e.g. coconut fatty acid, is preferred.

The amount of the fatty acid thickener required to achieve the desired thixotropy values and the desired physical stability will depend on such factors as the type of fatty acid, the detergent-active compound, the inorganic salts, especially TPP, the other LADD constituents, as well as the expected storage and transport conditions.

In general, however, amounts of fatty acid as thixotropic agent that can be used are in the range from 0.03 to 0.5%, preferably from 0.03 to 0.2%, particularly preferably from 0.05 to 0.15%, which gives the desired long-term stability and absence of phase separation.

The polyvalent metal salts of the above-mentioned fatty acids can also be used in the present invention as thixotropic thickeners. Suitable metal salts as thixotropic thickeners are described in US Patent No. 4,752,409.

The preferred metals are the polyvalent metals such as magnesium, calcium, aluminum and zinc.

In general, the metals can be present in the divalent to the pentavalent state. The metal salts are preferably used in their higher oxidation states. For the LADD mixtures as well as all other applications where the mixture according to the invention will or may come into contact with objects used for handling, storing or serving food products, or which may otherwise come into contact with or be consumed by people or animals , the metal salt should naturally be selected taking into account the metal's toxicity. For this purpose, the calcium and magnesium salts are particularly preferred as generally safe food additives.

Many of these metal salts are commercially available. E.g. are the aluminum salts available in the triacid form, e.g. aluminum stearate as aluminum tristearate, Al(C27<-H>35COO)3. The monoacid salts, e.g. aluminum monostearate, Al (OH) 2 (0-^71135000) and the diacid salts, e.g. aluminum distearate, Al (0H) (C-L7H35COO) 2 1 and mixtures of two or three of the mono-, di- and tri-acid salts can be used for the metals, e.g. Al, with valence +3, and mixtures of the mono- and diacid salts can be used for the metals, e.g. Zn, with valence +2. The diacids of the metals with valence +2 and the triacids of the metals with valence +3, the tetraacidmethylmetals with valence +4 and the pentaacids of the metals with valence +5 are preferably used in predominant quantities. E.g. at least 30%, preferably at least 50%, particularly preferably from 80 to 100%, of the total metal salt should be in the highest possible oxidation state, i.e. that each of the possible valence sites is occupied by a fatty acid residue.

The metal salts are, as mentioned above, generally commercially available, but can be easily prepared by e.g. saponification of a fatty acid, e.g. animal fat, stearic acid, etc., or of the corresponding fatty acid ester followed by treatment with a hydroxide or oxide of the polyvalent metal, e.g. in the case of the aluminum salt with alum, alumina, etc.

Calcium stearate, i.e. calcium distearate, magnesium stearate, i.e. magnesium distearate, aluminum stearate, i.e. aluminum tristearate, and zinc stearate, i.e. zinc distearate, are the preferred multivalent fatty acid salt stabilizers. Mixed fatty acid metal salts, such as the naturally occurring acids, e.g. coconut acid, as well as the mixed fatty acids that result from the commercial manufacturing process, are also used with advantage as a cheap but effective source of the long-chain fatty acid.

The amount of the fatty acid salt stabilizers required to achieve the desired improvement in physical stability will depend on such factors as the properties of the fatty acid salt, the properties and amount of the thixotropic agent, the detergent-active compound, the inorganic salts, especially TPP, the other LADD- the components, as well as the expected storage and transport conditions.

In general, however, amounts of the polyvalent metal salts of fatty acids as stabilizers in the range from 0.02 to 1%, preferably from 0.06 to 0.8%, particularly preferably from 0.08 to 0.4%, provide the long-term stability and the absence of phase separation after standing or during transport at both low and elevated temperatures, which is required for a commercially acceptable product.

In general, LADD efficiency is directly related to (a) available chlorine amounts, (b) alkalinity, (c) wash medium solubility, and (d) foam inhibition. Here, it is preferred that the pH in the LADD mixture is at least approx. 9.5, preferably from 10.5 to 13.5 and most preferably at least approx. 11.5. At the relatively lower pH values, the LADD product is too viscous, i.e. solid-like, and thus does not fluidize easily under the shear force levels created in the dispenser container under normal operating conditions for the machine. Addition of NaOH is thus often required to increase the pH to the above-mentioned areas, and to increase the properties with regard to flowability. The presence of carbonate is also often required here as it acts as a buffer which helps to maintain the desired pH level. However, too much carbonate should be avoided as it can cause the formation of needle-like crystals of carbonate and thereby impair the stability, thixotropy and/or washing effect of the LADD product, as well as impair the dispensability of the product from e.g. squeeze bottles. Caustic soda (NaOH) serves the additional function of neutralizing phosphoric or phosphonic acid ester defoamers when present. It is common to have 0.5-3 wt% NaOH and 2-9 wt% sodium carbonate in the LADD mixture although it should be noted that sufficient alkalinity can be provided by NaTPP and the sodium silicate.

NaTPP can be used in the LADD mixture in a range from 8 to 35% by weight, preferably 20-30% by weight, and should preferably be free of heavy metals which tend to decompose or inactivate the preferred sodium hypochlorite and other chlorine bleach compounds. NaTPP can be anhydrous or hydrated, including the stable hexahydrate with a degree of hydration of 6 which corresponds to approx.

18% water by weight or more. In view of the stability of the hexahydrate, the presence of some water of hydration is actually very effective, as it is believed to serve to form crystals of the stable hexahydrate which accelerates hydration and solubilization of the remaining NaTPP particles. If only the hexahydrate is used, wash-

the intermediate product be too liquid. Conversely, if only the anhydrous NaTPP is used, the product may in some cases be too thick and therefore unsuitable. Particularly preferred LADD mixtures are obtained e.g. when a weight ratio between anhydrous and hexahydrated NaTPP of 0.5:1 - 2:1 is used, values of approx. 1:1 is particularly preferred. Foam inhibition is important to increase the dishwasher's efficiency and minimize destabilizing effects that can occur due to the presence of excessive foam in the dishwasher during use. Foam can be reduced to a sufficient extent by appropriate selection of the type and/or amount of detergent-active material, which is the most important foam-producing component. The degree of suds is also somewhat dependent on the hardness of the washing water in the machine, whereby appropriate regulation of the proportions of NaTPP which have a water softening effect can help to provide the desired degree of suds inhibition. It is taken with a chlorine bleach-stable defoamer or inhibitor. Particularly effective are the alkyl esters of phosphonic acid with the formula available* e.g. as "PCUK-PAE", and especially the alkyl esters of acid phosphate of the formula

available e.g. such as "SAP" and "LPKn-158", where one or both of the R groups in each ester type can independently be a C1-20 alkyl group. Mixtures of the two types, or any other chlorine bleach stable types, or mixtures of mono- and diesters of the same type, can be used. Particularly preferred is a mixture of

mono- and di-Cj_g_^g alkyl esters of acid phosphate, such as monostearyl/distearyl acid phosphates 1,2/1. When these are used, it is common with proportions of 0.01 to 5% by weight, preferably 0.1 - 5% by weight, especially 0.1 - 0.5% by weight, of anti-foam in the mixture, the weight ratio between detergent-active ingredient (d) and defoamer (e) are generally in the range of 10:1 - 1:1 and preferably 4:1 - 1:1. Other defoamers that can be used include e.g. the known silicones.

Although any chlorine bleach compound can be used in the compositions according to the invention, such as dichloroisocyanurate, dichlorodimethylhydantoin or chlorinated TSP, alkali metal hypochlorite, e.g. potassium, lithium, magnesium and especially sodium hypochlorite. The mixture contains sufficient chlorine bleach compound to provide 0.2 - 4.0% by weight available chlorine, determined e.g. by acidifying 100 parts of the mixture with excess hydrochloric acid. A solution containing 0.2 - 4.0% by weight of sodium hypochlorite contains or roughly gives the same percentage of available chlorine. A solution containing 0.8-1.6 wt% sodium hypochlorite contains 0.8-1.6 wt% available chlorine and is particularly preferred. E.g. sodium hypochlorite solution (NaOCl) with from 11 to 13% available chlorine in amounts of 3 - 20%, preferably 7 - 12%, can be advantageously used.

The sodium silicate which provides alkalinity and protection for hard surfaces, such as glazes and patterns on fine porcelain, is used in an amount varying from 2.5 to 40% by weight, preferably 10 - 35% by weight, in the mixture. At the higher levels indicated here, e.g. at levels higher than 10% by weight, the silicate also provides an increased anti-stain effect. The sodium silicate is generally added in the form of an aqueous solution, preferably with a Na20:SiO2 ratio of 1:2.2 - 1:2.8, e.g. 1:2,4. Most of the other ingredients in the mixture, especially NaOH, sodium hypochlorite and anti-foam, can also be added in the form of an aqueous dispersion or solution.

Detergent-active material that can be used here must be stable in the presence of chlorine bleach, especially hypochlorite bleach, and it is preferred with those of the organic, anionic, amine oxide, phosphine oxide, sulfoxide or betaine types of water-dispersible, surface-active agents, as they the former anionic compounds are most preferred. They are used in amounts varying from 0.1 to 5%, preferably 0.3 to 2.0%. Particularly preferred surfactants here are the straight-chain or branched alkali metal mono- and/or di-((Cg^^) alkyldiphenyl oxide mono- and/or -disulphates, commercially available e.g. such as Dowfax 3B-2<®> and Dowfax 2A-1<®«>

In addition, the surfactant should be compatible with the other components in the mixture. Other suitable surfactants include the primary alkyl sulfates, alkyl sulfonates, alkyl aryl sulfonates and secondary alkyl sulfates. Examples include sodium C20_i8_<a>lky1_ sulfates, such as sodium dodecyl sulfate and sodium tallow alcohol sulfate, sodium C-L0_-j_g-alkanesulfonates, such as sodium hexadecyl-1-sulfonate, and sodium C-]_2_-Lg-alkylbenzene sulfonates , such as sodium dodecylbenzene sulfonates. The corresponding potassium salts can also be used.

Like other suitable surfactants or detergents, the surfactant amine oxides usually have the formula R2R"'"N0 where each R is a lower alkyl group, e.g. methyl, and R<1> is a long-chain alkyl group with from 8 to 22 carbon atoms, e.g. a lauryl, myristyl, palmityl or cetyl group. Instead of an amine oxide, a corresponding surface-active phosphine oxide R^-^PO or sulfoxide RR-^SO can be used. Surfactant betaines usually have the formula R2R<1>N - R"C00~, where each R is a lower alkylene group with from 1 to 5 carbon atoms. Certain examples of these surfactants are lauryldimethylamine oxide, myristyldimethylamine oxide, the corresponding phosphine oxides and sulfoxides , and the corresponding betaines, including dodecyldimethylammonium acetate, tetradecyldiethylammonium pentanoate, hexadecyldimethylammonium hexanoate and the like. For reasons of biodegradability, the alkyl groups in these surfactants should be straight chain, and such compounds are preferred.

Surfactants of the above-mentioned type, all of which are well known in the art, are described e.g. in US Patent Nos. 3,985,668 and 4,271,030.

The amount of water contained in these mixtures should of course be neither so high that it gives unreasonably low viscosity and fluidity, nor so low that it gives unreasonably high viscosity and low flowability, as thixotropy properties are reduced or destroyed in both cases. Such an amount is easily determined by routine testing in any particular case and generally ranges from 25 to 75% by weight, preferably 50-65% by weight. The water should also preferably be deionized or softened. These amounts of water in the mixture include the water added as part of the liquid solutions of other components, but do not include bound water, e.g. that present in NaTPP hexahydrate.

Other conventional ingredients may be included in these compositions in small amounts, generally less than about 3% by weight, such as perfume, hydrotropic agents, such as sodium benzene, sodium toluene, sodium xylene and sodium cumenesulfonates, preservatives, dyes and pigments and the like, all of which are of course stable against chlorine bleach compounds and high alkalinity (properties of all the components). Particularly preferred for dyeing are the chlorinated phthalocyanines and polysulphides of aluminum silicate, which give, respectively, appealing green and blue colors.

The liquid ADD mixtures according to the invention are easily used in a known manner for washing crockery, glasses, cups, cutlery and the like in an automatic dishwasher equipped with a suitable detergent dispenser, in an aqueous washing water containing an effective amount of the mixture.

In a preferred embodiment of the invention, the aqueous, liquid washing-up liquid is formulated using the ingredients specified below.

The gel-like, thixotropic, aqueous, liquid dishwashing detergent mixtures according to the present invention may contain common additives for dishwashing detergents. The mixtures can be prepared with commercially available, solid powder builders, and/or the components can be mixed and the mixtures ground to a desired particle size.

The invention can be practiced in various ways, and certain specific embodiments will be described to illustrate the invention with reference to the accompanying examples.

All amounts and proportions shown here,

is the weight percent of the mixture unless otherwise stated.

The present invention is further illustrated by means of the following examples.

Example 1

A thixotropic, aqueous, liquid detergent for automatic dishwashers is made up of the following ingredients in the indicated amounts.

The components are mixed by following the method according to US patent no. 4,752,409.

(The ingredients are added to the water usually in the order given and it is stirred gently until a homogeneous mixture is obtained). The mixture is tested by washing glassware and crockery at a temperature of 49°C in hard water (300 ppm hardness) in an automatic dishwasher, and the clean and dried dishes are found to have no visible film and very few visible stains.

Example 2

To demonstrate the effect of adding the alumina and titanium dioxide anti-film forming agent, mixtures with and without the alumina and titanium dioxide anti-film forming agent are prepared and compared to a commercially available powder detergent.

The mixtures are designed so that they contain the following components.

The components are mixed in the usual way or can be mixed by following the method according to US patent document no. 4,752,409.

(The ingredients are added to the water usually in the order given and it is stirred gently until a homogeneous mixture is obtained). The mixture is tested by washing glassware at 49°C in hard water (300 ppm hardness).

The five above-mentioned compositions (A), (B), (C), (D) and (E) were tested and compared with a commercially available powder detergent F for automatic dishwashers. The blends were tested in a Kenmore automatic dishwasher using the procedure described in ASTMD 3566-79, except that only four wash cycles were used. The film formation and staining were assessed according to the following scales:

Film rating scale

1. Best, no visible film

2. Weak film formation, becomes visible

3. Noticeable film, increasing

4. Continued increase of significant film

5. Film formation becomes severe

6. High film formation, strong build-up

7. Continued increase in heavy film.

Stain Rating Scale

A. Best, no stains

B. Very few spots visible

C. Clearly

D. Substantial coverage, about 50%.

The results obtained are reproduced in table 11 below.

Products (A) and (C) left no stains on glassware, apart from one/two streak marks, and were rated (B). The product (E) without any anti-film forming agent, left a substantially uniform film B-C, 3-4 on glassware. However, significant improvement in staining and film formation was achieved with the compositions containing both anti-film forming agent and polyacrylate.

Example 3

A thixotropic, aqueous, liquid detergent for automatic dishwashers is made up of the following ingredients in the indicated amounts.

The ingredients are generally added to the water in the order indicated, and it is stirred gently until a homogeneous mixture is obtained.

The mixture is tested by washing glassware at 54°C in hard water (300 ppm hardness) in an automatic dishwasher. The washed and dried glassware is found to have no visible film and very few visible stains.

The thixotropic, aqueous, liquid detergents for automatic dishwashers according to the present invention provide improved film properties.

Claims (5)

1. Gel-like, thixotropic, aqueous, liquid detergent mixture, characterized in that, based on weight, it comprises: (a) 5 - 35% detergent builder, (b) 2.5 - 40% sodium silicate, (c) 0.5 - 5% of an alumina or titanium dioxide antifilm forming agent with a particle size of 0.1 - 10 ym, (d) 2 - 14% polyacrylic acid polymer or polyacryl acid polymer salt builder with the formula where R1r R2 and R3 may be the same or different, and are hydrogen or C^-C^ lower alkyl, M is hydrogen or an alkali metal, n = 5 - 1000, and the polymer has a molecular weight of 1000 - 100000, (e) 0 - 9% alkali metal carbonate, (f) 0.1 - 5% chlorine bleach stable, water dispersible, organic, detergent active material, (g) 0 - 5% chlorine bleach stable antifoam, (h) chlorine bleach compound in an amount that gives 0.2 - 4% available chlorine, (i) a sufficient amount of a thixotropic fatty acid of 8-22 carbon atoms or polyvalent metal salt thereof, to give a thixotropy index of 2.5 - 10, (j) 0 - 8% sodium hydroxide, and (k) the balance water . 2. Mixture according to claim 1, characterized in that the alumina or titanium dioxide antifilm forming agent is present in an amount of 1 - 4%, and polyacrylic acid polymers! or the salt thereof is present in an amount of 3 - 12%. 3. Mixture according to claim 1, characterized in that the thixotropic thickener comprises a fatty acid with 8-22 carbon atoms in an amount of 0.03 - 0.5%. 4. Mixture according to claim 1, characterized in that the thixotropic thickener comprises a polyvalent metal salt of a fatty acid with 8-22 carbon atoms in an amount of 0.02 - 1.0%. 5. Mixture according to claim 1, characterized in that the alumina or titanium dioxide antifilm forming agent has a particle size of 0.5 - 8.0 ym.