CH678336A5 - - Google Patents

Description

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CH 678 336 A5

description

The invention relates to a thixotropic composition for dishwashers, which contains a concentrated dispersion of solid particles in a liquid phase. Air bubbles are contained in this composition in an amount sufficient to make the specific gravity of the liquid phase equal to the bulk specific gravity of the overall composition, thereby improving the physical stability of the thixotropic composition for dishwashers. The composition according to the invention can also be perfumed. The invention also relates to a method for producing the said thixotropic composition.

Recent research has focused on pasty, gel-like, and thixotropic forms of liquid detergents for dishwashers because they have desirable advantages over conventional powder detergents. These advantages are, for example, easy dispensing from the container, lower volume consumption per wash load due to the higher concentrations of active ingredients and long-term storage without loss of moisture.

The development of liquid dishwashing detergents has posed problems because of the need to incorporate numerous ingredients into these formulations that are generally incompatible, i.e. they tend to react with each other before use in the dishwasher. In addition, a liquid detergent for dishwashers should also show thixotropic behavior, i.e. it should be highly viscous at rest and have relatively high flow limits (Bingham-plastic character), but if subjected to shear forces, such as when squeezing through an opening, it should have flow properties similar to a viscous liquid, so that it easily fits into a distribution compartment for the detergent in an automatic dishwasher. Once in the manifold, it should quickly return to the high viscosity Bingham plastic state.

Another common problem with liquid detergents for dishwashers is that they easily separate into essentially solid and liquid phases during their storage time. Additives have improved the phase stability, but there is a disadvantage that any addition to detergents can adversely affect the theological properties of the composition.

Similarly, adding a fragrance to an automatic dishwasher liquid detergent to give it a desirable odor has also been problematic because of its effect on the complex balance of ingredients within the composition required to achieve the desired theological and other physical properties to obtain. For example, it would be expected that the presence of a chlorine releasing compound would adversely affect an oil type fragrance that is easily oxidized. In addition, it can be assumed that the presence of oily fragrances, because of their tendency to act as defoamers, has an adverse effect on the phase stability of this composition.

The invention provides scented and unscented thixotropic liquid detergents for automatic dishwashers with improved physical stability and a new process with which liquid detergents with thixotropic properties for automatic dishwashers can be produced which are physically stable and do not tend to separate during a longer storage period .

The invention also makes available a new method by which air can be introduced into a thixotropic liquid detergent for automatic dishwashers in order to maintain stability during extended storage times.

A fragrance can be incorporated into the thixotropic composition to give it a pleasant smell without affecting its stability or theological properties.

The invention provides a thixotropic composition for dishwashers containing a concentrated dispersion of solid particles in a liquid phase, which is characterized in that air bubbles are introduced into the composition in an amount sufficient to equal the specific weight of the liquid phase to the specific bulk weight of the composition to make and thereby improve the physical stability of the thixotropic dishwasher detergent.

According to the invention, the specific liquid detergents for dishwashing machines, which can also be scented, can contain several or all of the following substances:

1. Alkali tripolyphosphates to soften or bind the minerals of the hard water and to emulsify and / or peptize dirt;

2. Sodium silicate to supplement the alkalinity required for effective cleaning and to protect the glaze and pattern of fine porcelain;

3. alkali carbonate, which is generally considered optional to increase alkalinity;

4. a chlorine-releasing agent to help eliminate stains that lead to water stains;

5. chlorine bleach resistant defoamers to reduce foam, which enhances machine efficiency and provides additional cleaning power;

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6, chlorine bleach-resistant surfactant, sometimes referred to as a cleaning active material, compatible with the other ingredients and ensuring detergency;

7. thixotropic thickeners in an effective amount to provide the composition with a thixotropy index of 2.0 to 10;

5 8. alkaline (caustic) substances, if necessary, to adjust the pH within a range of 10 to 14;

9. a long chain fatty acid or a salt of a long chain fatty acid as a physical stabilizer in an amount effective to increase the physical stability of the composition;

10. Fragrance in an effective amount to impart a pleasant smell to the composition without impairing its stability or thixotropic properties;

11. Water in an amount sufficient to avoid destroying the desired thixotropic properties; and

12. Air in the form of bubbles of 5 to 80 microns in diameter in an amount in the range of about 2 to 10% by volume which is effective in that it is specific to the composition

15 gives bulk weight from about 1.20 to about 1.35 and improves the physical stability of the composition.

In particular, the invention provides a method for producing liquid detergents for automatic dishwashers with a specific bulk weight which is approximately equal to the specific weight of the liquid phase, which show improved physical stability and theological behavior. It comprises the following levels:

a) preparing a pre-dispersion mixture containing water, physical stabilizer, defoamer and surfactant;

B) preparation of a thickener premix containing the predispersion mixture from stage a), water and a thixotropic thickener and mixing the thickener premix until the thixotropic thickener is hydrated and deagglomerated;

c) Mixing, preferably with strong shearing, the thickener premix from stage b) with additional water, while adding the other desired detergent components, in order to

To produce 30 siger dishwasher detergent, which contains about 2 to 10 vol .-% air, and d) homogenizing the liquid detergent for dishwasher to balance the specific weights of the bulk phase and the liquid phase of the composition or equalize .

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The process of the invention can be carried out under conditions which ensure that the thixotropic liquid composition for automatic dishwashers reaches a highly stable state. It has been found that this condition is reached when 2 to about 10 vol% air is trapped in the composition and the bulk specific gravity of the composition is approximately equal to the specific gravity of the liquid phase of the composition.

In a preferred embodiment, a fragrance is added to the liquid dishwasher detergent under conditions and in an amount such that the thixotropic properties or the physical stability of the composition are not impaired. For example, a process in which the liquid detergent for automatic dishwashers of stage d) above 45 is first cooled to a maximum temperature below about 29.4 ° C. and then the liquid detergent for automatic dishwashers and the desired fragrance are introduced into a mixer in which the Fragrance is evenly dispersed in the liquid end product, namely the detergent for dishwashers.

The invention thus provides a method for combining components in such amounts that a liquid detergent for automatic dishwashers is obtained which has an improved combination of properties, especially with regard to thixotropy and phase stability.

The drawing shows a schematic for the preferred method of the invention.

The term “bulk specific gravity” used here denotes the specific weight of a liquid detergent for dishwashing machines, which contains all the necessary components. The expression “specific weight of the liquid phase” here denotes the specific weight of a deaerated liquid, measured in a manner known per se, which is centrifuged by the liquid detergent for automatic dishwashers, i.e. the «Buik composition» is removed.

The term "thixotropy index" is the ratio of the viscosities measured at 3 rpm and at 30 rpm at room temperature after 3 minutes using a Brookfield HATDV II viscometer with a No. 4 spindle. .

The invention relates to thixotropic detergents for dishwashers with thixotropic properties and long-term phase stability, which may contain a fragrance which does not impair the properties of the composition. The invention also relates to a method for producing liquid cleaning agents for automatic washing machines with thixotropic properties and improved

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Long-term phase stability, in which air can be introduced into the composition in an amount of 2 to 10% by volume in such a way that a balance is established between the specific weights of the bulk and the liquid phase of the composition.

A preferred example of the invention for a composition that may be perfumed with perfume contains the following ingredients on a weight basis unless otherwise stated:

(a) 5 to 35% alkali tripolyphosphate;

(b) 2.5 to 20% sodium silicate;

(c) 0 to 9% alkali carbonate;

(d) 0.1 to 5% chlorine bleach-resistant, water-dispersible organic cleaning active material;

(e) 0.01 to 5% chlorine bleach resistant foam damper;

(f) chlorine bleach in an amount that provides 0.2 to 4% chlorine;

(g) thixotropic thickener in an amount sufficient to provide the composition with a thixotropy index of 2.0 to 10;

(h) alkali hydroxide, if necessary, to adjust the pH to 10-14;

(i) a long chain fatty acid or its salt as a physical stabilizer in an effective amount to increase the physical stability of the composition;

(j) an optional amount of fragrance to provide the composition with a fragrance and to avoid destroying the desired thixotropy and physical stability;

(k) water in an amount sufficient to avoid destroying the desired thixotropic properties; and

(I) air in an amount in the range of 2 to 10% by volume to impart a bulk specific gravity of 1.20 to 1.35 to the composition.

According to the method of the invention, a phase-stable, thixotropic, preferably liquid, cleaning agent for automatic dishwashers is obtained by introducing or introducing or introducing air into the composition, so that a balance is established between the specific weights of the bulk and liquid phases of the composition .

It has been found that concentrated dispersions containing both liquid and solid phases, such as the liquid detergent for dishwashers, can be stabilized by dispersing an appropriate amount of air in the form of micrometer-sized bubbles throughout the liquid phase of the composition. It has also been found that the air can be dispersed and stabilized in the form of bubbles in the entire liquid phase by using a multi-part stabilization system consisting of two or more, preferably three, components, which generally fall into the "physical stabilizers" category. , “Foam suppressor” or “defoamer” and “surfactants” fall. Without wishing to be bound by any theory as to how the stabilizing system and air interact in the liquid dishwasher detergent, it is believed that the stabilizing components at the air / liquid interface interact such that the hydrophobic groups of these components are directed towards on the air bubbles, the hydrophilic groups are oriented towards the aqueous phase. The hydrophilic groups in turn influence the solid particles of the suspension either via hydrogen bonds or hydrogen bonding or through electrostatic interaction. In other words, the liquid / air interface consists of the components of the stabilization system and solid particles, which cause the interface to swell or become a liquid-crystalline structure type.

According to the preferred method of the invention, a three-part stabilization system produces a highly resistant liquid detergent for automatic dishwashers by stabilizing air bubbles in the micrometer size in the entire composition such that the specific bulk weight of the liquid detergent for automatic dishwashers is approximately equal to the specific weight of the liquid phase alone in that liquid detergent for dishwashers. In this state, the liquid detergent for automatic dishwashers shows high stability, i.e. there is little or no tendency towards phase separation due to density changes or deviations in the composition.

In order to effectively disperse the air in the entire liquid detergent for dishwashing machines, it has been found that the size of the air bubbles introduced must be larger than the size of all dispersed solid particles. The bubble size can generally vary from 5 to 80 microns, preferably from 20 to 60 microns. The air bubble size can generally be controlled by varying the blade tip speed of the dispersers or stirrers during the mixing process. Air induction was also found to produce 2 to 10 volume percent phase stable compositions, with the preferred range being 4.0 to 9.0 volume percent, the most preferred range being 6.5 to 8, 5 vol .-% was.

As can best be seen from the drawing, the method of the invention can be carried out in a mixing system which comprises a predispersion vessel 2, a premixing vessel 4, a main mixing vessel 6, homogenizers 8, 10, 19 and 21, heat exchanger 12, an intermediate one

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Mixer 14 and the storage tank 16 comprises. As can be seen from the drawing, all vessels are open to the atmosphere.

In the predispersion vessel 2, a predispersion mixture is prepared which comprises the stabilization system, which is then fed through line 18 and the homogenizer 19 through the pump 20 into the 5 premixing vessel 4, where it is added to a thixotropic mixer to form a thickener premix. The thickener premix is then brought through line 22 and the homogenizer 21 through the pump 24 into the main mixing vessel 6, in which the remaining constituents of the liquid detergent for automatic dishwashers are added.

The cleaning agent is then passed from the vessel 6 through the homogenizers 8 and 10 and then cooled in the exchanger 12. If a perfumed dishwashing detergent is desired, the chilled product is passed through an intermediate static mixer 14 where a fragrance is added. The liquid dish detergent is then placed in the tank 16 in which it is stored.

According to the preferred method of the invention, a predispersion mixture of the liquid detergent is first prepared which contains the selected physical stabilizer, foam suppressant and surfactant components of the liquid detergent for dishwashing machines, as well as part of the total water content of the liquid dish detergent. Depending on the choice of stabilizing components, one or more of them may initially be solid, requiring either the addition of heat to form a melt or the addition of water to form a solution or emulsion. The amount of water added to the predispersion mixture should be limited in order to maintain a highly viscous mixture. The predispersion mixture is subjected to a mixing process, preferably with strong shearing, for about 5 minutes; during this time the temperature of the predispersion mixture can exceed 37.8 ° C. Mixing under strong shear, as used here, is expressed in terms of shear rates and depends on numerous variables, the most important of which are the design of the mixing vessel and the speed of the stirrer ends. For example, the predispersion mixture is preferably mixed in a Myers HSD ™ with strong shearing, a stirrer (20.32 cm) using a stirring speed of about 4500 1373 m / minutes. Under these conditions, the "high shear rate" is of the order of 100 s_1. 30 The predispersion mixing stage can be carried out in other customary mixing devices or high-shear mixers, for example in roller mills, colloid mills and premier mills.

A second mixing stage follows the predispersion mixing stage, during which a thixotropic thickener, e.g. Clay, and a further part of the total water content of the liquid dishwashing detergent is added to the predispersion mixture to form a thickener premix. The thickener premix is preferably subjected to low shear stirring for about 20 minutes. During this time, the thickener is hydrated, deagglomerated and dispersed in the entire thickener mixture. Mixing under low shear, as used here, is also defined in terms of shear rates and, as discussed above in connection with strong shear, is dependent on a number of variables including the design of the mixing bowl and the stirrer tip speed. A suitable device for mixing the thickener premix under low shear comprises conventional paddle mixers or paddle mixers in which the average shear rates are of the order of about 10 s -1.

The amount of water added in each of the first two mixing stages is more or less arbitrary within the 45 limits of the total water content of the finished liquid dish detergent. However, it has been found that the amount of water added to the predispersion mixture is said to be less than that which would result in an impermissibly low viscosity and high fluidity of the mixture, as such a condition would interfere with mixing, particularly under high shear conditions.

A second mixing step is followed by a main mixing step or main mixing step in which the thickener premix, the remainder of the total water content of the liquid dishwashing detergent and other desired constituents thereof are admixed, preferably under conditions of high shear, in order to produce the main mixture. During this stage, the remaining ingredients of the liquid dish detergent are preferably added. In the 55 main mixing step, shear rates in the order of 100 s-1 are achieved. The remaining ingredients of the liquid dishwashing detergent that can be added include the following: sodium hydroxide, sodium carbonate, silicates, alkali metal triphosphates, chlorine bleach, and other suitable ingredients that make up the desired liquid dishwashing detergent. A suitable device for performing the mixing under strong shearing are, for example, roller 60 mills, colloid mills, premier mills and Myers HSD.

The main mixture from the mixing stage working under strong scissors is then subjected to a series of coarse and fine homogenization steps until the solid and liquid phases of the liquid detergent for automatic dishwashers are thoroughly homogenized. The homogenization stages take place under conditions of strong shear, shear rates in the order of magnitude 65 of about 10 * s_1 being achieved. The homogenization stage is complete when the specific bulk

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Weight (density according to the definition above) of the liquid dishwashing detergent for automatic dishwashers is approximately equal to the specific weight of the liquid phase of the dishwashing detergent alone. The homogenization of the liquid dishwashing detergent for dishwashing machines can be carried out in conventional homogenizers such as a high-speed Dispax ™, which is available from IKA-Works, Inc. is available.

According to the invention, the dishwashing detergent is preferably subjected to mixing at a speed and duration which ensure that air is drawn into the dishwashing detergent in an amount of about 2 to about 10, preferably 4 to 9 and particularly preferably 6.5 to 8.5% by volume . In the preferred embodiment of the invention, the air is introduced into the composition while mixing the ingredients of the dishwashing detergent with strong shearing. However, according to the invention, air can be introduced into the process at any point or time in a manner known per se in order to obtain a phase-stable composition.

If the specific bulk weight is approximately equal to the specific weight of the liquid phase, this is an indication of air intake and higher product stability. It has been found that, in general, densities or specific weights in the range from 1.20 to 1.35 result in a phase-stable liquid dishwashing detergent, the preferred specific weight being in the range from 1.26 to 1.32.

According to a more preferred embodiment of the invention, a fragrance is added to the liquid dishwashing detergent following the coarse and fine homogenization stages described above. In this embodiment, the liquid dish detergent is cooled and then the fragrance (s) are mixed in, preferably in a static mixer, in order to obtain a physically stable and uniformly dispersed liquid dish detergent for automatic dishwashers.

According to an optiomal embodiment of the invention, the liquid dishwashing detergent is preferably cooled to a temperature below 29.4 ° C. before the desired fragrance is added. It has been found that the addition of the desired fragrance before cooling adversely affects the specific weight of the liquid dish detergent, which in turn affects the phase stability of the composition. It has also been found that the introduction of the fragrance prior to homogenization, i.e. during the preparation of the main mixture leads to a product with poor physical stability, i.e. the liquid dish detergent begins to separate into phases almost immediately when standing. It has also been found that the addition of the fragrance in amounts of about 0.01 to about 0.4% by weight creates a desired fragrance without degrading the theological properties or phase stability of the composition, with a preferred range of fragrance addition is about 0.02 to 0.2% by weight.

In an alternative embodiment of the invention, the liquid and solid components of the thixotropic detergent are gradually added as described above to a high shear mixer with continuous mixing until all of the desired components are included. The detergent mixture is then subjected to high shear mixing for about 15 minutes in order to obtain a homogeneous thixotropic detergent composition with air introduced. The high shear mixing stage is complete when the specific bulk weight of the composition is approximately equal to the specific weight of the liquid phase.

Although the method of the invention has been described in terms of preferred ingredients and amounts, it will be apparent to those skilled in the art that a highly stable thixotropic detergent composition can be obtained in the absence of one or more of the ingredients by appropriately adjusting the remaining ingredients. For example, a phase stable composition can be formulated in the absence of a foam suppressor by minimizing the surfactant concentration and increasing the amount of physical stabilizer in the composition.

The liquid detergents for automatic dishwashers produced by the process of the invention are generally formulated with the amounts of the components described in detail below.

Any linear, branched, polymeric or polybasic, saturated or unsaturated long-chain fatty acid can serve as a physical stabilizer according to the invention. Preferably the fatty acid is linear and saturated, has 10 to 22, preferably 10 to 20 and most preferably 14 to 18 carbon atoms including the carbon atom of the carboxyl group of the fatty acid. Fatty acid mixtures can be used, for example those of natural origin such as tallow oil fatty acid, coconut fatty acid, soybean fatty acid etc., or synthetic fatty acids from industrial production processes.

Examples of fatty acids that can be used as physical stabilizers include, for example, decanoic acid, dodecanoic acid, palmitic acid, myristic acid, stearic acid, behenic acid, oleic acid, eicosanoic acid, tallow fatty acid, coconut fatty acid, soy fatty acid, etc., and mixtures thereof. Behenic acid, stearic acid and mixed fatty acids are preferred. In liquid compositions for automatic dishwashers and in any other application in which the compositions prepared according to the invention come or can come into contact with objects which are used for handling, storage or offering food or which can come into contact with or in some other way can be consumed by humans or animals, is the user6

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tion of the fatty acids as a physical stabilizing agent because of their known low toxicity particularly advantageous. For this purpose, stearic acid and behenic acid are especially preferred. Another major advantage of using fatty acids as stabilizers is their low cost compared to the fatty acid metal salts.

The amount of physical stabilizer required to achieve the desired increase in physical stability depends on such factors as the type of fatty acid, the type and amount of thixotropic agent, the detergent active compounds (surfactants), inorganic salts, in particular the tripolyphosphate (TPP) and other components of the liquid detergent for dishwashing machines, as well as the intended storage and shipping conditions.

Salts of the above fatty acids can also be used as physical stabilizers, such as the salts of alkali, alkaline earth and polyvalent metals. The alkali salts include the sodium, potassium and ammonium salts of fatty acids. The alkaline earth salts include the calcium, barium and strontium salts of the fatty acids. Examples of the fatty acids with which salts of polyvalent metals can be formed as stabilizers include decanoic acid, dodecanoic acid, palmitic acid, myristic acid, stearic acid, oleic acid, eicosanoic acid, tallow fatty acid, coconut fatty acid, soy fatty acid and mixtures thereof. Stearic acid and mixed fatty acids are the preferred fatty acids from which salts of polyvalent metals can be formed as stabilizers.

The preferred multivalent metals are Group IIA, IIB and HIB metals, especially magnesium, calcium, aluminum and zinc, although other multivalent metals including those of Groups IIIA, IVA, VA, IB, IVB, VB, VIB, VlIB and VIII des Periodic table of the elements can also be used. Specific examples of such other polyvalent metals are Ti, Zr, V, Nb, Mn, Fe, Co, Ni, Cd, Sn, Sb, Bi etc. As stated above with regard to the choice of harmless free fatty acids, the metal salts should also their toxicity should be considered. For this reason, the calcium and magnesium salts are particularly preferred since they are generally considered to be harmless food additives.

The metal salts described above are generally commercially available; however, they can also be easily manufactured, for example by saponification of fats and oils, e.g. of animal fat, or by neutralizing free fatty acids with a hydroxide or oxide of polyvalent metal such as alumina, aluminum, etc. Alternatively, metal salts of fatty acids can be obtained by reacting a soluble metal salt with a soluble fatty acid salt.

Calcium stearate, i.e. Calcium stearate, magnesium stearate, i.e. Magnesium distearate, aluminum stearate, i.e. Aluminum monostearate, aluminum distearate, aluminum tristearate and mixtures thereof, and zinc stearate, i.e. Zinc distearate are the preferred fatty acid salt stabilizers of polyvalent metals.

The amount of fatty acid or fatty acid salt stabilizers required to achieve the desired increase in physical stability depends on such factors as the type of fatty acid or its salt, the type and amount of the thixotropic agent, the surfactant, the inorganic salts , in particular of TPP, as well as the other components of the liquid detergents for automatic dishwashers and the intended storage and shipping conditions.

However, it has been found that in general long-term stability, i.e. the non-occurrence of phase separation at low and elevated temperatures is achieved by adding free fatty acids or the salts in amounts of from 0.01 to 1.0, preferably from 0.06 to 0.8 and most preferably from 0, 08 to 0.4% by weight. In addition, it has been found that free fatty acids are preferred over their salts mainly because they are easy to disperse.

Alternatively or in addition to the above physical stabilizers, small but effective amounts of polyacrylic acid polymers and copolymers and their salts can be added to improve the physical stability of the composition. These polymers and their salts are generally commercially available. Suitable polymers are the polyacrylic acids and their sodium salts, which are available from Rohm and Haas as ACRYSOL ™ LMW. The amounts of polymers can range from 0.01 to 3% by weight depending on the molecular weight of the polymers, the lower amounts being more suitable for the higher molecular weight polymers.

Foam inhibition during dish washing cycle is important to maximize dishwasher efficiency and minimize the destabilizing effects that can occur due to excess foam in the dishwasher. By selecting the type and / or amount of the surfactant, the main foam-producing component, foam can be reduced sufficiently. The degree of foaming is also somewhat dependent on the hardness of the washing water in the machine, with an appropriate adjustment of the amounts of water softening agents, e.g. of alkali tripolyphosphate, can ensure the desired level of foam inhibition. According to the invention, however, a chlorine bleach-resistant foam damper or defoamer is preferably installed as part of the stabilization system. Effective defoamers include the alkylphosphonic acid esters of the formula

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0

II

HO? R

1

OR

as well as the acidic alkyl phosphate esters of the formula

0

II

HO P OR

1

OR

which can be obtained, for example, from Hooker (SAP) or from American Hoechst such as Knapsack (LPKn-158), where one or both R groups in each ester type can independently mean a C12 to C20 alkyl group. Mixtures of the two types of esters or other types of chlorine bleach resistant or mixtures of mono- and diesters of the same type can also be used. The preferred inhibitor is a mixture of acidic mono- and di-Ci6- to Cia-alkylphosphate esters, for example acidic monostearyl / distearylphosphates 1.2 / 1 (Knapsack LPKn-158). In addition, it is an advantageous feature of the invention that many of the stabilizing long chain fatty acids such as stearic acid and behenic acid act as complementary foam killers.

The detergents of the invention generally contain an anti-foaming agent in an amount from G to 5, preferably from 0.01 to 5.0 and most preferably from 0.01 to 0.5% by weight. In addition, the weight ratio of surfactant to foam suppressor is preferably in the range of 10/1 to 1/1, particularly preferably 4/1 to 1/1.

The cleaning active material, i.e. Surfactant selected for use in the automatic dishwasher liquid detergent of the invention must be resistant to chemical degradation and oxidation by highly active chlorine bleach, which are also present in the automatic dishwasher liquid detergent.

Useful surfactants in the present invention are either of the anionic or nonionic type, or combinations of the two. Preferred surfactants are mono- or dianionic and contain sulfate, sulfonate or carboxylates such as amphiphiles. The most preferred surfactants according to the invention are the mono- and / or di- (Cs to Ci4) alkyldiphenlyoxide mono- and / or disulfonates, the alkyl group of which can be linear or branched, in the form of their alkali metal salts, which are commercially available from Dow Chemical are available, for example as DOWFAX ™ 3B-2 and DOWFAX ™ 2A-1. In addition, the surfactant is said to be compatible with the other components of the composition. Other preferred surfactants are, for example, the primary alkyl sulfates, alkyl sulfonates, alkylarylsulfonates, secondary alkyl sulfates and olefin sulfonates. Examples are sodium cio to cis alkane sulfonates such as sodium lauryl sulfonate, sodium hexadecyl I-1 sulfonate and sodium Ci2 to Cte alkyl benzene sulfonates such as sodium dodecyl benzene sulfonate. The corresponding potassium salts can also be used.

Other suitable useful surfactants or detergents include the amine oxide surfactants having the structure RgRWO, where each R is a lower alkyl group, e.g. methyl, and R1 is a long chain alkyl group having 8 to 22 carbon atoms, e.g. a lauryl, myristyl, palmityl or cetyl group . Instead of an amine oxide, a corresponding phosphine oxide surfactant R2R1PO or sulfoxide RR1SO can be used. Betaine surfactants mostly have the formula R2R1N-R'-COO-, where each R is a lower alkylene group with 1 to 5 carbon atoms. Specific examples of the amine oxide surfactants are lauryfdimethylamine oxide, myristyldimethylamine oxide, the corresponding phosphinoxides and sulfoxides and the corresponding betaines including dodecyldimethylammonium acetate, tetradecyldiethylammonium pentanoate, hexadecyldimeihylammonium hexanoate and the like. For reasons of biodegradability, the alkyl groups in these surfactants are preferably linear. Detergent compositions according to the invention may contain 0 to 5, preferably 0.1 to 5 and most preferably 0.3 to 2.0% by weight of surfactant.

Thixotropic substances, i.e. Thickeners or suspending agents which produce thixotropic properties in an aqueous medium are known. These thixotropic substances are water-soluble, water-dispersible or colloid-forming, organic or inorganic, monomeric or polymeric. They must be stable in the detergent compositions of the invention, i.e. resistant to high alkalinity and chlorine bleaches such as sodium hypochlorite. The preferred thixotropic substances are the inorganic, colloid-forming clays of the smectite and / or attapulgite type. These substances are generally used in amounts of 0.1 to 10% by weight in order to impart thixotropic properties or Bingham-plastic behavior to the liquid detergents for automatic dishwashers. Other suitable thixotropic substances include small but effective amounts of an aliphatic long chain fatty acid having 8 to 22 carbon atoms or the dimers or trimers thereof. These

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Substances are generally used in amounts of 0.2 to 0.5% by weight. An advantage of the liquid dishwashing detergents of the invention is that the desired thixotropic properties or Bingham plastic behavior can be obtained with smaller amounts of thixotropic thickeners in the presence of the physical stabilization system mentioned above. For example, inorganic colloid-forming clays of the smectite and / or atta pulgite type in the liquid detergents for automatic dishwashers of the invention in amounts of 0 to 3, preferably 0.2 to 2.5, most preferably 0.5 to 2, 2% by weight is generally sufficient to achieve the desired thixotropic properties and Bingham plastic character when used in combination with the physical stabilization system.

The smectite clays include montmorillonite (bentonite), hectorite, saponite and the like. Montmorillo-nittone are preferred and are available under trade names such as ThixogeP "M No. 1, and Gel White ™ GP, H, etc. from Georgia Kaolin Company and ECCAGUM ™ GP, H, etc. from Luthern Clay Products. Attapul-gittone include those Materials commercially available from Engelhard Minerals and Chemicals Corporation under the trade names Attagel ™, ie Attagel ™ 40, Attagel ™ 50 and Attagel ™ 150. Mixtures of smectite and attapulgite types in weight ratios of 4/1 to 1/5 Thickeners or suspending agents of the above types are well known and are described, for example, in US Pat. No. 3,985,668. Abrasives or polishing agents should be avoided in the liquid detergents for automatic dishwashers because they damage the surface of fine dishes, crystals and the like can.

As an alternative to the above thixotropic thickeners, small but effective amounts of high molecular weight polyacrylic acid polymers and copolymers and their salts can be added to improve the rheological properties and physical stability of the compositions. These polymers and their salts are usually commercially available and have the formula

C - C

R3 C00M

-J n wherein R 1, R 2 and R 3 can be the same or different and can be hydrogen, lower alkyl (C 1 to C 4) or combinations thereof. The value of n is 5 to 2000, preferably 10 to 1500 and most preferably 20 to 1000. M represents hydrogen or an alkali metal such as sodium or potassium, with sodium being preferred. The preferred Ri, R2 and R3 groups are hydrogen, methyl, ethyl and propyl. A preferred acrylic acid monomer is one in which R 1 to R 3 are hydrogen, e.g. Acrylic acid, or wherein Ri and R3 are hydrogen and R2 is methyl, e.g. Methyl acrylate monomer. Polyacrylic acid copolymers may include copolymers of, for example, acrylic acid or methacrylic acid and polycarboxylic acid anhydride or acid such as, for example, succinic anhydride, succinic acid, maleic acid, maleic anhydride, citric acid and the like.

Special applicable polyacrylic acid polymers and salts thereof are for example ACRY-SOl_ ™, acrylic acid polymers from Rohm and Haas, ALCOPERSE ™ 110 from Alco or CARBOPOL from B.F. Goodrich. An applicable polyacrylic acid copolymer is SOKALAN ™ CP5 from BASF.

The amount of polymer used in the compositions can range from 0 to 3% by weight, depending on the presence and amount of other stabilizing ingredients.

The detergents of the invention may also contain various inorganic builders such as alkali tripolyphosphates and silicates.

A preferred builder material is sodium tripolyphosphate (NaTPP), which serves to soften the water-hardening minerals and to emulsify and / or peptize dirt. The NaTPP used in the liquid detergent for dishwashers of the invention is usually present in an amount of 5 to 35, preferably 20 to 30% by weight. The NaTPP should preferably be free of heavy metal which tends to decompose or deactivate the preferred sodium hypochlorite and other chlorine bleaches. The NaTPP can be anhydrous or hydrated, including the stable hexahydrate with a degree of hydration corresponding to about 22% by weight of water or more. The NaTPP is commercially available in the anhydrous or hydrated forms under the trade names Thermphos NWM and Thermphos NH ™. Preferred liquid detergents for dishwashers were obtained, for example, if a weight ratio of anhydrous to hexahydrated NaTPP in the range from about 0.5 / 1 to about 2/1, preferably about 1/1, was used.

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The compositions in which little or no phosphate is desired can be used instead of other functionally equivalent builders. For example, 5 to 35% by weight aluminum silicate zeolite can be used in the compositions of the invention if the sodium silicate content is increased to 25% by weight or more.

It is preferred that the liquid detergents for automatic dishwashers according to the invention contain an alkali silicate, e.g. Contain sodium silicate to ensure alkalinity of the composition and protection of hard surfaces such as glaze and patterns of fine porcelain. The silicate component is generally present in the liquid dishwasher detergent in an amount of 0 to 50, preferably 2.5 to 20, and most preferably 5.0 to 15.0% by weight. The silicate is generally added in the form of an aqueous solution and preferably has a NagO / SiOa ratio of about 172.2 to 1 / 2.8.

A chlorine bleach can be used in the liquid detergent for automatic dishwashers produced according to the method of the invention. The chlorine supplier is preferably an alkali hypochlorite, for example potassium hypochlorite, lithium hypochlorite, calcium hypochlorite, magnesium hypochlorite and most preferably sodium hypochlorite. Other chlorine suppliers are compounds such as dichloroisocyanurate, dichlorodimethylhydantoin and chlorinated TSP, and others. The liquid dishwashing detergents of the invention should contain sufficient chlorine compounds to provide 0.2 to 4.0, preferably 0.8 to 1.6 weight percent chlorine, for example by acidifying 100 parts of the composition with excess hydrochloric acid is determined. A solution containing 0.2 to 4.0% by weight sodium hypochlorite contains or provides approximately the same percentage of available chlorine.

As an alternative to the chlorine bleach, a stabilized enzyme system can be used to give the dishwashing detergents proteolytic and amylolytic enzyme cleaning effects. The stabilized system preferably contains 0.5 to 2.0% by weight of enzyme, 1 to 4% by weight of a water-dispersible protein-containing material from the group consisting of casein and collagen, 0.75 to 2% by weight of a boron compound and 1.5 to 4 wt .-% of an alpha-hydroxycarboxylic acid.

It is preferred that the pH for the liquid detergents for automatic dishwashers produced according to the invention is at least 9.5, preferably 10 to 14.0 and most preferably 11.0 to 11.5, which is in a 1% aqueous solution is measured. The liquid detergents for automatic dishwashers can be brought to the desired alkali content by adding an alkali hydroxide, e.g. Sodium hydroxide can be adjusted. The typical concentrations of sodium hydroxide in the liquid dishwashing detergents are usually in the range of 0 to 6, preferably 0 to 3.0% by weight. The presence of sodium hydroxide has the further function of neutralizing the phosphate or phosphonic acid ester.

An alkali carbonate, for example sodium carbonate, can also be used in the liquid dishwashing detergents of the invention. The carbonate serves as a buffer to ensure the desired pH. Typical concentrations of sodium carbonate in the liquid dishwashing detergent are in the range of 0 to 9.0, preferably 2 to 9.0% by weight.

Fragrances useful in the invention must be resistant to chemical degradation and oxidation by the very active chlorine bleaches that are also present in the compositions. Useful fragrances include those of natural origin, such as plant extracts, e.g. essential oils or synthetic substances from industrial manufacturing processes. Examples of bleach-resistant fragrances are p-cresoimethyl ether, dihydrolimone epoxide, dodecene-1, 2-epoxide and n-undecyl nitrile and others. Further examples of suitable bleach resistant fragrances are disclosed in U.S. Patent 3,876,551.

Of course, the fragrance must be sufficiently stable in a bleaching environment, i.e. it should not be easily oxidized by the hypochlorite in the detergent. This is important for two reasons: first, the loss of hypochlorite would exceed the limits of what is permitted in a dishwashing detergent, and secondly, the oxidation of the fragrance would reduce the aromatic properties of the product and in some cases even give off an unpleasant smell. It has been found that adding the fragrance to the compositions in an amount of 0.01 to 0.40, preferably 0.02 to 0.2% by weight gives a desired fragrance without increasing the theological properties or the physical stability of the dish detergent damage.

The amount of water contained in these compositions is, of course, believed to be sufficient to provide the desired viscosity and fluidity without adversely affecting the thixotropic properties of the composition. The appropriate amount of water is easily determined by routine experimentation in each individual case and is generally about 30 to 75, preferably 35 to 65% by weight. In addition, the water is preferably demineralized or softened.

In addition to the components described above, the detergents of the invention may contain small amounts of other ingredients, generally less than 3% by weight of hydrotropic substances such as sodium benzene, toluene, xylene and cumene sulfonates, protective agents, dyes and pigments as well as enzymes, all of which must be resistant to chlorine bleach and high alkalinity. The chlorinated phthalocyanines and polysulfides of aluminum silicate, which in each case produce pleasant green and blue colors, are particularly preferred for dyeing. TÌO2 can be used to whiten and neutralize false colors.

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Low molecular weight polyacrylic acid polymers and their salts with molecular weights in the range from 2000 to 10,000, preferably 4000 to 6000, are particularly preferred for eliminating or minimizing film and stain formation on gias. Special usable polymers are the low molecular weight polyacrylic acids and their corresponding ones Sodium salts, which are available, for example, from 5 Rohm and Haas as ACRYSOLJM LMW.

The liquid dishwashing detergents of the invention are easily applied in a manner known per se for washing dishes, kitchen utensils and the like in automatic dishwashers which are equipped with a suitable distributor for the detergent, in an aqueous washing bath which contains an effective amount of the composition. Although the invention has primarily been described in terms of its application to liquid dishwashing detergents and methods of making the same, those skilled in the art will appreciate that the benefits of introducing air into a three part stabilization system are increased physical stability the thixotropic suspension, also occur in the same way with other thixotropic suspensions.

15 The following examples are intended to illustrate the invention.

example 1

A perfumed liquid detergent for dishwashing machines of the formulation given below was produced according to the preferred method of the invention, as outlined in the drawing.

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step

component

% By weight

Predispersion

0)

Water (softened)

acidic mono- and di-Ci6 to Ci8 phosphate esters (foam dampers)

Aluminum stearate (physical stabilizer) sodium mono- and didecyidisulfonated diphenyl oxide (surfactant)

41.44 8.84

5.52 44.20

Total

100.00

Premix

(II)

Water (softened) predispersion (I) Montmoriilonitton

82.37 10.43 7.20

Total

100.00

Main mix

(HI)

Water (softened) premix (II) sodium hydroxide (50% A.I.) sodium carbonate sodium silicate (43.5 A.I.) NaTPP hydrate NaTPP-anhydrous sodium hypochlorite (13% A.I.)

25.69 17.53 2.42 5.05 17.42 12.12 12.12 7.48

Subtotal

99.83

Homogenization, cooling and mixing (IV)

Fragrance

0.17

Total

100.00

According to the preferred method of the invention, a predispersion was prepared in a vessel (2), which was equipped with a high speed dispersing device, e.g. was equipped with a Myers HSD "™. The amount of water introduced into the predispersion vessel was limited so that the mixture remained viscous and susceptible to high-shear dispersion ) into a premixing vessel (4), in which the clay thickener and water were added to the predispersion mixture under conditions of low shear The preparation of the premix generally takes about 20 minutes, depending on the mixing speed. The premix obtained was removed and homogenized in the homogenizer (21), then added to the main mixing vessel (6) with water, where it was High shear dispersing under An using a Myers HSD ™ device. During the high shear mixing, the remaining liquid and solid components were gradually added to the main mixing vessel (6).

In particular, the solid ingredients were added as further ingredients, the mixture became more viscous, and the high-speed disperser ground the particles to a fine particle size, which in turn caused the temperature to rise, e.g. to about 51.7 to 65.6 ° C. The continuous high-shear dispersion also caused a substantial amount of atmospheric air to be introduced into the main mixing vessel (6), which is open to the atmosphere. The

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High shear dispersing was continued for a total of about 20 minutes, with visible clumps of solid material disappearing and the particle size of the undissolved particles reduced so that a phase stable dispersion was formed.

The main mixture was then passed through a series of coarse and fine homogenizers (8 and 10) where the material was ground at high speeds for a relatively short period of time to further deagglomerate any remaining solid particles. The product obtained was a durable thixotropic liquid dishwasher detergent composition trapped in atmospheric air in bubbles ranging in diameter from 5 to 80 microns.

If it was desired to add a fragrance to the detergent composition, as in the present example, the main mixture was placed in a heat exchanger (12) from the temperature of the main mixture, generally above 37.8 ° C, usually 40.6 to 51.7 ° C is cooled to a temperature of about 29.4 ° C or less. The cooled main mixture and the fragrance were then passed through a series of static mixers (14) connected in series. The product obtained was a stable, perfumed, thixotropic liquid detergent for dishwashers.

It has been found that the addition of fragrance to the composition according to this method avoids an adverse effect on the theological properties and on the long-term phase stability of the composition. The specific weight, viscosity and phase stability, i.e. Phase separation, the perfumed detergent composition were measured (Example 1A). For comparison, a sample of the material of the main mixture (Example 1B) was taken for analysis before the fragrance was added. Measurements of the specific weight of the bulk phase and the liquid phase were carried out according to methods known per se. For example, the specific gravity of the bulk composition was determined by weighing a known volume of the bulk composition and an identical volume of water. The ratio of the weight of the bulk composition to the weight of the water is referred to as the "specific bulk weight" or bulk weight as defined by the invention.

The specific gravity of the liquid phase or the liquid phase specific gravity was determined by first placing a sample of the liquid dish detergent in a conventional centrifuge, e.g. Ivan Sorvall then spun the centrifuge at a speed of about 2000 rpm to remove a sufficient amount of the excess liquid (the clear deaerated liquid phase) for weighing.

The centrifugation step takes about 1 to 1 1/2 hours to separate a sufficient amount of the supernatant for several measurements. The specific gravity of the supernatant was then calculated by dividing the weight of an 8 ml sample of the supernatant by the weight of an identical volume of water, the ratio being defined as the "specific gravity of the liquid phase".

The viscosity of the compositions was determined using a Brookfield HATDV II Model II viscometer with a # 4 spindle (Brookfield Labs, Stoughton, Mass.). The viscosity was recorded after the compositions were sheared for 90 seconds at a shear rate of 20 rpm. The results are summarized below.

property

example 1

1A

1B

Specific weight (bulk)

1.28

1.28

Specific weight (liquid)

1.28

1.28

Viscosity (cP) - 1 day after production

5060

4760

Viscosity (cP) —12 weeks after manufacture

5150

6350

Separation (%), 12 weeks after production

0

0

The above data show that the process of the invention provides a thixotropic liquid dishwasher detergent that is highly stable and does not undergo phase separation after long periods of storage.

Example 2

The following liquid dishwashing detergents with the formulations given in Table I were prepared in a single open mixing vessel according to an alternative embodiment of the process of the invention.

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Table I

component

Example 2A

Example 2B

water

36.90

36.15

acidic mono- and di-Ci6- to cis-alkyl phosphate ester (foam damper), 5%

3.20

3.20

Natnum mono- and -didecyldisulfonieries diphenyl oxide (surfactant)

0.80

0.80

Stearic acid (physical stabilizer)

0.10

0.10

Montmorillonite clay

1.25

0

alkaline (caustic) compound (50% A.i.)

2.40

2.40

Soda ash

5.0

5.0

Silicate (45% A.L)

17.34

17.34

NaTPP hydrate

12.00

12.00

NaTPP anhydrous

12.00

12.00

Bleach (11% A.i.)

9.00

9.00

Acrylic acid polymer

0

2.00

Air (rest)

0.01

0.01

Total

100.00

100.00

All of the above were mixed in a Premier ™ mill mixer at room temperature. In the examples, a 5% aqueous defoamer (LPKn) dispersion was initially prepared by heating and mixing the defoamer in water until dispersed. Similarly, the surfactant (Dowfax ™) and a physical stabilizer (stearic acid) were heated to form an emulsion before and during the addition to the mixer.

After the addition of the surfactant and physical stabilizer, the mixture was allowed to cool and the remaining ingredients were gradually added in the order shown in Table I, subjecting the mixture to constant high shear mixing in the presence of atmospheric air.

Upon addition of the last ingredient, usually a bleach, the composition was subjected to further high shear mixing until atmospheric air was introduced into the thixotropic detergent in the form of countless bubbles having a diameter in the range of from about 2 to about 10% 5 to 8 microns, which equalized or balanced the bulk specific gravity of the product with the specific gravity of the deaerated liquid phase.

As can be seen from the above examples, an air stabilizing three component system, i.e. a physical stabilizer, foam suppressor (defoamer) and surfactant applied.

For each of the liquid cleaning compositions obtained, the specific gravity, degree of aeration and phase stability, i.e. Phase separation when standing, measured.

The degree of ventilation is calculated as follows:

Vented Product Density -

"", Density of the ventilated product "" "

e gsgra Density of the vented product x

The density of the deaerated product was determined by centrifuging the composition to remove all of the cracked or drawn air, then the density of the centrifuged composition was determined in the usual way. The results obtained are summarized below.

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property

Example 2

2A

2 B

Specific weight (bulk)

1.28

1.29

Specific weight (liquid)

1.28

1.28

Degree of ventilation (%)

7.91

7.20

Type of separation

0.00 *

0.00 *

* Eight weeks after sample preparation

It can be seen from the above data that liquid cleaning agents containing a three-component system as a stabilizing system according to the invention show excellent stability. As indicated, the air stabilized composition of Example 2A has a bulk specific gravity (1.28 g / cm3) that is identical to the liquid phase specific gravity (1.28 g / cm3) of the composition.

Under these circumstances, the composition shows excellent phase stability.

Substantially identical results were obtained with the composition of Example B in the absence of a thixotropic thickener, e.g. Clay, whereby a specific bulk weight of 1.29 g / cm 3 was achieved, which was almost identical to the specific weight of the liquid phase of the composition. Example 2B shows that clay is not required to make an acceptably stabilized composition. Such a composition is also advantageous in that all of its constituents are completely water-soluble, which leads to superior stain and film formation behavior compared to clay-based thixotropic cleaners.

Claims (36)

Claims 1. Thixotropic composition for dishwashing machines containing a concentrated dispersion of solid particles in a liquid phase, characterized in that air bubbles are contained in the composition in a sufficient amount to make the specific weight of the liquid phase equal to the specific bulk weight of the total composition, thereby increasing the physical stability the thixotropic composition for dishwashers is improved. 2. Composition according to claim 1, characterized in that the concentrated dispersion contains a builder, an organic cleaning active material, a physical stabilizer and a thickener. 3. Composition according to claim 2, characterized in that the concentrated dispersion also contains a foam damper. 4. Composition according to claim 1, characterized in that the air makes up 2 to 10 vol .-% of the composition. 5. Composition according to claim 1, characterized in that the air makes up 4 to 9 vol .-% of the composition. 6. Composition according to claim 1, characterized in that the air makes up 6.5 to 8.5 vol% of the composition. 7. The composition according to claim 4, characterized in that the specific bulk weight is 1.2 to 1.35. 8. The composition according to claim 1, characterized in that the specific bulk weight is 1.26 to 1.32. 9. The composition according to claim 1, characterized in that the air bubbles are bubbles in the micrometer size range. 10. The composition according to claim 1, characterized in that the air bubbles are stabilized by a three-part system comprising a surfactant, a defoamer and a physical stabilizer. 11. The composition according to claim 4, characterized in that the air bubbles are larger than the solid particles. 12. The composition according to claim 7, characterized in that the air bubbles have a diameter of 5 to 80 microns. 13. The composition according to claim 1, characterized in that the air bubbles have a diameter of 20 to 60 microns. 14. The composition according to claim 8, characterized by a) 5 to 35% by weight of alkali metal tripolyphosphate in the concentrated dispersion; b) 0 to 50% by weight sodium silicate; c) 0 to 9% by weight of alkali carbonate; d) 0 to 5% by weight of chlorine bleach-resistant, water-dispersible organic cleaning material; 15 5 10th 15 20th 25th 30th 35 40 45 50 55 60 CH 678 336 A5 e) up to 5% by weight of chlorine bleach-resistant foam damper; i) a chlorine bleach in an amount that makes available 0.2 to 4% by weight of chlorine; g) a long chain fatty acid or its salt in an amount effective to increase the physical stability of the composition; h) air in an amount of 2 to 10% by volume; i) thixotropic thickener in an effective amount to provide the composition with a thixotropy index of 2.0 to 10.0; and j) water in an effective amount to avoid destroying the desired thixotropic properties. 15. The composition according to claim 14, characterized in that the cleaning active material is a compound of the group consisting of branched alkali mono- and -di-Cs- to Cu-alkyldiphenyloxide mono- and -disulfonates and linear alkali-mono- and -di-Cs- to Ci4-alkyldiphenyloxidemono - and is disulfonate 16. The composition according to claim 15, characterized in that the foam damper is from the group consisting of alkylphosphonic esters and acidic alkylphosphate esters. 17. Aqueous composition according to claim 1, characterized in that it contains a) 5 to 35% by weight of alkali metal tripolyphosphate; b) 2.5 to 20% by weight sodium silicate; c) 0 to 9% by weight of alkali carbonate; d) 0.1 to 5% by weight of chlorine bleach-resistant, water-dispersible, organic cleaning active material; e) 0.01 to 5 wt .-% chlorine bleach resistant foam damper; f) a chlorine bleach in an amount which makes available 0.2 to 4% by weight of chlorine; g) a long chain fatty acid or salt thereof in an effective amount to increase the physical stability of the composition; h) stabilized air bubbles in an amount of 2 to 10% by volume and a size in the range of 5 to 80 microns; i) a thixotropic thickener in an effective amount to provide the composition with a thixotropy index of 2.0 to 10.0; and j) water in an effective amount to avoid destroying the desired thixotropic properties. 18. The composition according to claim 17, characterized by a specific bulk weight of 1.20 to 1.35. 19. The composition according to claim 17, characterized in that the thickener (i) is a sodium salt of a polyacrylic acid. 20. The composition according to claim 17, characterized in that the physical stabilizer (g) is stearic acid or a salt thereof in an amount of 0.01 to 1.0 wt .-%. 21 »Composition according to claim 17, characterized in that the physical stabilizer (g) is the metal salt of the fatty acid. 22. The composition according to claim 17, characterized in that the thixotropic thickener (i) is present in an amount of 0.1 to 10 wt .-%. 23. The composition according to claim 17, characterized in that the foam damper is from the group consisting of alkylphosphonic esters and acidic alkylphosphate esters. 24. A method for producing a thixotropic composition for dishwashers according to claim 1, characterized by the steps; - producing a concentrated dispersion of solid particles in a liquid phase; and - Introduction of air bubbles in the micrometer range in the composition in a sufficient amount to make the specific weight of the liquid phase equal to the specific bulk weight of the composition and thereby improve the stability. 25. The method according to claim 24 for producing a thixotropic composition for dishwashers with improved phase stability, comprising a concentrated dispersion of solid particles in a liquid phase, which is characterized in that stabilizing air bubbles are introduced into the composition in a sufficient amount by the specific weight to equate the liquid phase to the specific bulk weight of the composition, characterized by the following stages: a) mixing a surfactant, a physical stabilizer and water to form a substantially smooth predispersion; b) forming a thickener premix containing the predispersion of step a), a thixotropic thickener and water and mixing the premix such that the thickener is substantially hydrated, deagglomerated and dispersed throughout the premix; c) mixing a main mixture containing the premix of stage b) and water with the addition of other constituents; d) introducing air into the composition in an amount of 2 to 10% by volume; and e) homogenizing the composition to deagglomerate all solid particles to produce a smooth, thixotropic composition for dishwashers. 16 5 10th 15 20th 25th 30th 35 40 45 50 55 60 65 CH678 336A5 26. The method according to claim 25, characterized in that the predispersion a) also contains a foam damper. 27. The method according to claim 25, characterized in that the predispersion a) is subjected to high shear mixing. 28. The method according to claim 26, characterized in that the premix b) is subjected to mixing with low shear. 29. The method according to claim 25, characterized in that 4 to 9 vol .-% air are introduced into the composition for automatic dishwashers. 30. The method according to claim 26, characterized in that 6.5 to 8.5% by volume of air are introduced into the composition. 31. The method according to claim 26, characterized in that the composition contains at least 0.1 wt .-% of a bleach-resistant surfactant. 32. The method according to claim 26, characterized in that the composition contains at least 0.01 wt .-% of a bleach-resistant foam damper. 33. The method according to claim 26, characterized in that the composition contains at least 0.01 wt .-% of a physical stabilizer from the group of long-chain fatty acids and salts thereof. 34. The method according to claim 26, characterized in that the composition contains 0.1 to 3 wt .-% thixotropic thickener. 35. The method according to claim 26, characterized in that the thixotropic thickener is a poly-acrylic polymer with a high molecular weight or copolymer or salts thereof. 36. The method according to claim 26, characterized in that the air introduced into the composition for automatic dishwashers is in the form of bubbles which are in the size range from 5 to 80 micrometers. 17th