SE453834B - GEL TYPE COMPOSITION WITH TIXOTROPIC PROPERTIES INTENDED FOR AUTOMATIC DISHWASHERS - Google Patents

Description

20 25 30 35 453 854 opening, however, they should be rapidly fluidized and when the shear stress ceases, they should quickly return to the high viscosity / Bingham plastic state. Likewise, stability is of primary importance, i.e. there must be no clear sign of phase separation or sweating after a long standstill.

The preparation of compositions in gel form with the properties described above and intended for automatic dishwashers has thus far been problematic, especially when it comes to compositions suitable for household dishwashers. For effective action, it is generally recommended that the automatic dishwasher detergent, hereinafter referred to as ADD, contain (1) sodium tripolyphosphate (NaTPP) to soften or bind the mineral hardness of the water and to emulsify and / or peptize the contaminants; (2) sodium silicate to achieve the alkalinity required for efficient cleaning and to protect fine porcelain glaze and patterns; (3) sodium carbonate, which is generally considered arbitrary, to increase the alkalinity; (4) a chlorine-releasing agent that helps to remove dots of contaminants that can lead to water stains; and (5) defoamer / surfactant to reduce foaming, thereby improving the efficiency of the machine and the supply of the required amount of detergent. See, for example, SDA Detergents in Depth, "Formulations Aspects of Machine Dishwashing" Thomas Oberle (1974). Detergents of about this composition are usually in the form of liquids or powders. In general, the hypochlorite bleach is excluded from such compositions because it tends to react with the other chemically active ingredients, especially the surfactant, thereby degrading the suspending agent or the thixotropic agent and thus weakening its effectiveness. U.S. Pat.

CMC, synthetic clays and the like; inorganic salts including silicates, phosphates, polyphosphates, etc., a small amount of surfactant and defoamers. Bleach is not included. U.S. Patent 4,147,650 is similar to the previous one but also includes a hypochlorite bleach. However, the product is described as a detergent slurry.

U.S. Patent No. 3,985,668 discloses abrasive gels having a gel-like consistency which contain (1) suspending agents, preferably the smectite and attapulgite types of the colloidal clays; (2) abrasives, for example quartz sand or perlite; and (3) fillers comprising low density polymer powder, expanded perlite and the like, which have buoyancy and thus a stabilizing effect on the composition, in addition to serving as fillers, thereby replacing water which would otherwise be available and form an undesirable excess layer due to sweating and phase destabilization. The above ingredients are necessary. Possible ingredients are hypochlorite bleach, bleach stable surfactants and buffering agents, e.g. Silicates, carbonates, monophosphates, etc. Detergent salts such as NaTPP may be included as an additional optional component to provide or increase the detergent function not obtained by the buffering agent, the amount of the detergent salt not exceeding 5% of the total composition. according to the patent specification. The maintenance of the desired pH 10 levels is made possible by the buffer / wash support components. High pH is said to minimize the decomposition of the chlorine bleach and undesired interaction between surfactant and bleach. When NaTPP is present, the amount is limited to 5%, according to information. Defoamer not included. According to the present invention, it has now been found that improved detergent compositions, especially adapted for automatic dishwashers, in particular of the type found in homes, can be prepared which have the desirable properties which characterize thixotropic structures of gel type and which include each of the various components required for efficient cleaning in such automatic dishwashers.

Thus, a primary object of the present invention is to provide a detergent composition having thixotropic properties and adapted for advantageous use in an automatic dishwasher. Another object of the invention is to provide such a composition with good physical stability without any clear phase separation occurring after long periods of stagnation.

Another object of the invention is to provide such a composition in which the problems of undesired interaction between chemically active components are eliminated or at least for the most part solved. Yet another object of the invention is to provide such a composition which has the said stability under the highly alkaline conditions necessary for the detergent to have an effective action. Yet another object of the invention is to provide such a composition with improved rheological properties, which exhibits higher viscosities at low shear values and lower viscosities at high shear values, and thus is adapted so that it can be used to advantage in the dosing bowl of an automatic dishwasher. A further object of the invention is to provide such a composition with low foaming ability, improved cleaning ability and which is easily dispersed in the dishwasher.

Other objects and advantages of the invention will become apparent from the following.

The mentioned objects are achieved with the present invention which broadly relates to a normally gel-like aqueous detergent composition for automatic dishwashers, which composition has thixotropic properties and contains between approx. (a) S-35% by weight of water-soluble alkali metal tripolyphosphate with an average degree of hydration of between approx. 1 and 5; (b) 2.5-20% by weight of sodium silicate; (c) 0-9% by weight of water-soluble alkali metal carbonate; (d) 0.1-5% by weight of bleach-stable dispersible organic surfactant: (e) 0.1-5% by weight of mono- or di- (C 16 -C 18) alkyl ester of phosphoric acid as defoaming agent; (f) 3-20% by weight of NaOCl solution with 13% available Cl; (g) 1.5-10% by weight of inorganic colloidal clay as a thickener; and (h) a sufficient amount of sodium hydroxide to obtain a pH of 10.5-13.5, which composition has a thixotropy index of approx. 2.5-10.

The ADD compositions so formulated are low foaming; stable both chemically and physically; are readily soluble in the washing liquid and most effective at pH values, leading to the best improved cleaning ability, i.e. pH 10.5-13.5.

The compositions normally have gel consistency, i.e. they are highly viscous, opaque, Vaseline-like materials with Bingham plastic character and thus have relatively high yield strengths. A marked shear stress is therefore necessary to initiate or increase the flow, such as that which occurs in the activated dosing bowl of a started automatic dishwasher. Under these conditions, the composition quickly liquefies and is easily dispersed. When the shear force ceases, the liquid composition rapidly returns to high viscosity, a Bingham plastic state close to its original consistency.

In general, the effectiveness of ADD relates directly to (a) the available chlorine content; (b) the alkalinity; (c) the solubility of the wash liquor; and (d) the action of the defoamer, it being important here that the pH of the ADD composition is between 10.5 and 13.5, and preferably at least about 11.5. The addition of NaOH is therefore necessary because ADD without NaOH has a pH below 10.5. At this pH, the ADD product is too viscous, i.e. resembles a solid, and thus does not easily become liquid at the shear stresses which occur in the metering shells when the machine is operating under normal conditions. In fact, the composition loses much, if not all, of its thixotropic Ikar character. An addition of NaOH is thus necessary to raise the pH and improve the leaching properties.

The presence of carbonate is often required as this acts as a buffer capable of maintaining the required pH. Excessive quantities of carbonate should be avoided, however, as this may cause the formation of needle-like crystals of carbonate, which impair the stability and / or function of the ADD product. The sodium hydroxide also has the important task of neutralizing the defoaming phosphoric acid ester.

Other crucial features that guide the choice of components and are necessary to obtain a stable, effective ADD product with thixotropic properties are the following: NaTPP must be free of heavy metals, as the latter tend to decompose sodium hypochlorite. On average, NaTPP should contain approx. S-15% by weight of water, corresponding to an average degree of hydration of approx. 1-5. If only the hexahydrate is used, the detergent product becomes liquid with little, if any, thixotropic character. If only anhydrous NaTPP is used, the product becomes too thick and therefore unsuitable. Effective compositions can be obtained, for example, from a spindle no. A shear rate gradient of 7.4 sec 453 834 with a weight ratio of 0.5: 1 to 2: 1 between anhydrous and hexahydrated NaTPP, wherein a ratio of approx. 1: 1 is especially preferred. The defoamer is necessary to increase the efficiency of the dishwasher and to reduce the destabilizing effects which may occur due to the presence of excessive foam in the dishwasher during washing. The amount of chlorine available is supplied here in the form of sodium hypochlorite, rather than in the form of, for example, dichloroisocyanurates which are included in commonly used powdered detergents.

The ADD product shows improved rheological properties, which was found when examining the product's viscosity as a function of the shear rate. The experiments show that the compositions have a higher viscosity at a low shear rate and a lower viscosity at a high shear rate, and the values indicate a good flow and gelation at the shear rates that occur in a dishwasher. In practice, this means improved dosing and washing process as well as less discharge from the machine's dosing container, compared with commonly used liquid ADD products. At shear speeds corresponding to 3-30 rpm, the corresponding viscosities (Brookfield) are in the range between approx. 15,000 - 30,000 cP and approx. 3000 - 5000 cP, measured at room temperature with an LVT Brookfield viscometer after 3 minutes using ay corresponds to a spindle speed of approx. 3 rpm. An approximately ten-fold increase in shear rate results in a six- to seven-fold decrease in viscosity. In commonly used ADD gels, the corresponding viscosity reduction is only about double. In these humxsitions, water is the original viscosity, measured at approx. 3 rpm, only approx. 2500 - 2700 cP. The limit values for the outflow in the case of the compositions according to the invention are thus at lower shear rates and comprise a markedly larger range, which can be expressed as increased values for the shear rate in relation to increasingly decreasing mp viscosity. This property of the ADD products of the invention is summarized in the term thixotropy index (TI) which denotes the ratio between (a) actual viscosity at 3 rpm and (b) actual viscosity at 30 rpm. The compositions in question have a TI of approx. 2.5 - 10, and preferably 6 - 8. each of the tested ADD compositions showed a marked and rapid return to the original sleep consistency when the shear stress ceased.

In the preparation of the ADD product, all inorganic salts, i.e. carbonate, silicate and tripolyphosphate, are first dissolved or dispersed in the aqueous medium. The thickener is added last. The defoaming phosphoric acid ester was first prepared as an aqueous dispersion, as well as the thickener. The ester dispersion, sodium hydroxide and inorganic salts are first mixed at elevated temperature to an aqueous solution (deionized water) which is then cooled, constantly stirring. Bleach, surfactant and thickener dispersion are then added at room temperature to the cooled (25-35 ° C) solution. The amount of water used is such that a total salt content (AI) in the ADD product of approx. lo - 75% by weight, with 50 - 65% being preferred.

The inorganic salts used here constitute in% by weight of the total product approx .: (a) 5 - 35% and preferably approx. 20 - 30% NaTPP; (b) 2.5 - 20% and preferably approx. 10 - 15% sodium silicate with a Na 2 O: SiO 2 ratio of approx. 0.3-0.5, and (c) 0-9% and preferably approx. 4-7% alkali metal carbonate, preferably sodium carbonate. These salts should give a total salinity of approx. 20 - 50% by weight and preferably approx. 35 - 45% by weight.

The bleach consists of a solution of sodium hypochlorite, (NaOCl) with 13% available Cl in an amount of approx. 3 - 20% by weight, preferably approx. 7 - 12% by weight. Sodium hydroxide should, as mentioned, be present in an amount sufficient to maintain a pH of 10.5 to approx. 13.5 and preferably approx. 11.5 to approx. 12.7. In general, the amount thereof is approx. 0.5 to 3% by weight, and it should in any case be sufficient to neutralize the antifoam phosphoric acid ester compound.

The preferred defoamers are mono- and / or di-C 16 -C 18 alkyl esters of phosphoric acid in an amount of about 0.1-05,% by weight and preferably approx. 0.15 - 0.3% by weight, the special amounts partly due to the quantity of surfactant present.

The surfactants useful herein must be stable in the presence of the hypochlorite bleach, and they preferably consist of the anionic types of amine oxides, phosphine oxides, sulfoxides and betaine, of which the former are preferred. They are used in amounts of between approx. 0.1 and 5% by weight, preferably approx. 0.3 - 0.8% by weight. To ensure a suitable defoaming effect, it is generally advisable to keep the weight ratio of surfactant defoamer at approx. 10: 1 to 1: 1 and preferably approx. 1.5: 1 to 4: 1. The especially preferred surfactants here are straight chain or branched alkali metal mono- and / or di-C 8 -C 14 alkyldiphenyloxide mono- and / or disuloxates which are commercially available, such as e.g. Dowfax 3B-2 and Dowfax 2A-1. In general, the paraffin sulfonates have a tendency to impair, if not destroy, thixotropin, as they inappropriately increase the viscosity, which has caused major shear force problems. The surfactant must furthermore be compatible with the other components of the composition. Other suitable surfactants are primary alkyl sulfates, alkyl sulfonates, alkyl aryl sulfonates and secondary alkyl sulfates. Examples which may be mentioned are sodium C10-C18-alkyl sulphates such as sodium dodecyl sulphate and sodium tallow alcohol sulphate, sodium C10-C18-alkane sulphonates such as sodium hexadecyl-1-sulphonate; sodium C12-C18-alkylbenzenesulfonates such as sodium dodecylbenzenesulfonate, and corresponding potassium salts.

As other suitable surfactants or surfactants may be mentioned surfactant amine oxide substances with the typical structural formula R R 1 NO, in which each R represents a lower alkyl group, e.g. methyl, and R represents a long chain alkyl group having 8-22 carbon atoms, e.g. a lauryl, myristyl, palmityl or cetyl group. Instead of an amine oxide, a corresponding surface-active phosphinoxia can. 11211190, or sulfoxia, m g scg, is used. Surfactant betaine substances typically have the structural formula R R1N + R "COO-, in which each R represents a lower alkyl group, 2R1 is a long chain alkyl group as above and R" is an alkylene group having 1-5 carbon atoms. Specific examples of these surfactants are lauryl dimethylamine oxide, myristyl dimethylamine oxide, coconut dimethylamine oxide, cured tallow dimethylamine oxide, the corresponding phosphine oxides and sulfoxides, and the corresponding betaines, including dodecyldimethylmethylammonium methacetylmethane-methamethylammonium ammonium hexanoate and the like. In order to be biodegradable, the alkyl groups in these surfactants must be straight chain, and these are preferred.

Surfactants of the above type are all well known in the art and are described, for example, in U.S. Pat. Nos. 3,985,668 and 4,271,030. The thickeners or suspending agents useful herein generally consist of inorganic, colloidal clays of smectite and / or attapulgite type, the former being preferred. These materials affect the rheological properties of the composition, and they are used in an amount of between approx. 2.5 and 4% by weight, selecting an amount which in any case is sufficient to achieve the desired Bingham plastic character. The smectite clays include montmorillonite (bentonite) with the preferred types being hectorite, saponite and the like. Materials of this type can be obtained under trademarks such as Thixogel fr) No 15 and Gelwhite GP from Georgia Kaolin Company ( both are montmorillonites) Attapulgite clays include materials available under the brand name Attagel, ie Attagel 40, Attagel 50 and Attagel 150 from Engelhard Minerals and Chemicals Corporation.

Mixtures of smectite and attapulgite in weight ratios of 4: 1 to 1: 5 are useful here.

Suspending agents of the above type are all well known in the art and are described, for example, in the aforementioned U.S. Pat. No. 3,985,668.

Other components that can be included in the ADD compositions according to the invention are dyes, in order to obtain a composition with an attractive color. Particularly preferred are chlorinated phthalocyanines and polysulfides of aluminum silicate which give green and blue color, respectively.

The following examples are given for illustrative purposes only and should not be construed as limiting the invention. The percentages refer to weight and are based on total product, unless otherwise stated.

Example 1 A preparative dispersant of antifoam, consisting of a 2: 1 mixture of mono- and di- (C 16 -C 18) alkyl ester of phosphoric acid, 0.16 g in 6 g of water, was prepared by mixing at 60 ° C for 30 minutes, using a disc propeller mixer. This dispersion was named Part 1.

A preparative dispersion of Gelwhite GP thickener (hydration), 3 g in 17 g of water, was prepared by mixing at 70 DEG C. for 10 minutes using a Z-blade mixer. This dispersion was shown in Part 2.

The following components were mixed together in a Giusti mixer at 50 ° C =% Al% Deionized water 16.9 Part 1 6.16 0.16 Sodium hydroxide solution, 49% NaOH 2.40 1.2 Sodium carbonate 7.00 7.0 Sodium silicate (1: 2.4) solution, 47.5% solids 13.74 6.5 Sodium TPP (mainly anhydrous 1 * 12, oo 11.54 Sodium TPP (hexahydrate) 12.00 9.36 Blamkángen was cooled to 25-30 ° C, constantly stirring, and the following components were added at room temperature: Sodium hypochlorite solution - 13% available chlorine 7.615 1.0 Dei 2 (aisperge: with high speed turbine) 2o, oo 3.0 oøwfax ss-2 ** 0.80 0.36 X ie containing 0-5%, in particular 3% water xx sodium monodecyl / didecyl-disulfonated diphenyl oxide, 45% Al.

An opaque composition (about 40% AI) with gel-like consistency was obtained. It was determined that the composition had a TI of approx. 7, in accordance with the previously described procedure, based on the actual viscosity values of 28,000 cP and 4,000 cP at 3 rpm and 30 rpm, respectively. When tested in an automatic dishwasher equipped with a dosing container, the composition according to the above gave excellent dish results and it was dispensed easily and quickly. The compositions l fi 10 15 20 25 30 35 453 834 13 were sufficiently non-foaming. Little or no phase separation was observed after long-term storage in a closed vessel. The pH of the composition, measured as a 1% aqueous solution, was 11.6. In performing the shear tests, it was observed that the composition quickly returned to its original consistency at rest, without showing any appreciable lowering of the yield strength when tested within the above limits, i.e. within the shear force limit values that occur at least in a working automatic dishwasher. No noticeable difference was observed when the ADD product was portioned out by squeezing out of a tube, instead of from a dosing container.

Example 1, which shows a combined polyphosphate-carbonate-silicate concentration of approx. 37%, was repeated, however, the total content of these salts varied within the previously given limits. The best results were obtained with a combined salinity of at least approx. 30% and especially when the sodium tripolyphosphate content was at least approx. 20%. Higher silicate concentrations, which are desirable to protect porcelain glaze and patterns, also result in higher alkalinity, which can be compensated by appropriately reducing the sodium hydroxide content and / or adjusting the sodium carbonate (buffer) concentration. According to the results, the composition seems to be most sensitive to variations in the NaTPP concentration (the higher concentration range is more efficient) and its degree of hydration. Variations in the concentration of surfactant generally require corresponding and direct variations in the concentration of defoamers to obtain the desired low foam level.

A sum of the pH value of the composition during approx. 10.5 was followed by a marked reduction in the effectiveness of the composition, as well as a corresponding reduction in flowability.

I) Similar results were obtained when the procedure of Example 1 was repeated while exchanging the corresponding component for surfactant alkyl sulfate e.g. sodium coconut alkyl sulfate, attapulgite clay e.g. Attagel 50; and a 2: 1 mixture of montmorillionite and Attagel 50. Addition of small amounts, e.g. 0.003-0.05%, chlorinated phthalocyanine or aluminum silicate dye to the composition according to Example 1 (included together with the prepared dispersion of thickener or added afterwards to the cooled solution) gave compositions with appealing green and blue tones respectively.

The present invention has been described with reference to preferred embodiments, but one skilled in the art will of course recognize that modifications and variations thereof are included in the invention and are within the scope of the appended claims.

IT; ft

Claims (13)

10 15 20 25 30 453 834 15 P a t e n t k r a v The aqueous composition of the automatic dishwasher is characterized in that it contains: (a) 5-35% by weight of water-soluble alkali metal tripolyphosphate having an average degree of hydration of 1-5; (b) 2.5 - 20% by weight of sodium silicate; (c) 0-9% by weight of water-soluble alkali metal carbonate; (d) 0.1 ~ 5% by weight of bleach-stable water-dispersible organic surfactant; (e) 0.1 - 0.5% by weight of mono; and / or di (C 16 -C 18) alkyl ester of phosphoric acid as defoamers; (f) 3 - 20% by weight of NaOCl solution with 13% available Cl; (g) 1.5 - 10% by weight of inorganic colloidal clay as a thickener; and (h) sufficient sodium hydroxide to obtain a pH of 10.5 to about 13.5, the amount of phosphoric acid ester being sufficient to give low foaming properties, the amount of sodium hydroxide being at least sufficient to neutralize the phosphoric acid ester and the thixotropy index of the composition being 2 , 5 - 10. 2. A composition according to claim 1, characterized in that the weight ratio of surfactant to defoamer is 10: 1 to 1: 1. 3. A composition according to claim 1, characterized in that the total concentration of tripolyphosphate, silicate and carbonate is at least about 20%. Composition according to Claim 3, characterized in that the concentration of tripolyphosphate is 20 to 30% by weight. 5. A composition according to claim 1, characterized in that the tripolyphos æt net consists of a mixture of the substantially anhydrous form and the hexahydrated form thereof in a weight ratio of 1: 2 to 2: 1. 10 15 20 453 834 16 Composition according to Claim 5, characterized in that the weight ratio is 1: 1. 7. A composition according to claim 1, characterized in that it further contains a color-toning amount of a dye. Composition according to Claim 1, characterized in that the thickener is a smectite and / or attapulg clay. 9. A composition according to claim 1, characterized in that the surfactant is an alkali metal C8-C14-alkyl diphenyloxide sulfonate. 10. A composition according to claim 1, characterized in that tripolyphosphinate is a sodium tripolyphosphate, the carbonate is sodium carbonate, the surfactant is a mixture of mono- and di (C8-C14) -alkyldiphenyloxide disulfonates and bone thickening. . 11. A composition according to claim 10, characterized in that it has a pH value between 10.5 and 1.3. 12. A composition according to claim 10, characterized in that it has a pH value between 11.5 and 12.7. 13. A composition according to claim 10, characterized in that it has a thixotropy index of 6 - m8. W