DK158155B - DISHES OF THE GEL TYPE WITH THIXOTROP PROPERTIES - Google Patents

Description

in

DK 158155 B

The invention relates to detergents having thixotropic properties, improved chemical and physical stability, and which are readily dispersible in the washing medium to provide effective cleaning of cutlery, glassware, porcelain and the like.

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Commercially available detergent for household dishwashers provided in powder form has several drawbacks, e.g. non-uniform composition; costly work processes necessary for their manufacture; tends to clump together at high humidity, resulting in the formation of lumps that are difficult to disperse, and dust, a source of particular irritation for users suffering from allergies. In addition, liquid forms of such agents generally cannot be used in automatic dishwashers due to high foams, unacceptably low viscosities and extremely high alkalinity.

Recent research and development activity has gathered on the gel or "thixotropic" form of such agents, e.g. scouring and cleaning products and products for automatic washing characterized as thixotropic pastes. Detergents thus provided are, first of all, unfortunate in that they are insufficiently viscous to remain "attached" in the dispensing compartment of the dishwasher, and furthermore provide stain-like residues on cutlery, glassware, porcelain and the like. Thixotropic cleansers should ideally be high viscous in calm state, Bingham plastic by nature, and have relatively high utilization rates. However, when subjected to shear stresses, such as being shaken in a container or squeezed through an orifice, they must quickly become liquid and upon cessation of the applied shear stress quickly return to the high viscous / Bingham plastic state. Stability is also of great importance, ie. there should be no clear sign of phase shading or leakage after long standing.

The provision of gel detergents for automatic dishwashers having the properties described previously has

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2 to prove problematic, especially with respect to agents for use in household dishwashers, for effective use, it is generally recommended that the automatic dishwashing detergent, hereinafter also referred to as ADD, contain (1) sodium tri-polyphosphate (NaTPP) to soften or bond. minerals in hard water and emulsifying and / or peptizing pollution; (2) sodium silicate to impart the necessary alkalinity for effective cleaning and to provide protection of fine porcelain glaze and pattern; (3) sodium carbonate, usually considered optional, to improve the alkalinity; (4) a chlorine release agent to aid in the removal of contaminant stains leading to water stains; and (5) foaming agent / surfactant to reduce foam thereby improving machine efficiency and providing necessary cleaning. See, e.g. SDA Detergents in Depth, "Formulation Aspects of Machine Dishwashing", Thomas Oberle (1974). Detergents that approximate the previously described agent are mostly liquids or powders. Combining such ingredients in a gel form effective for use in home appliances has proved troublesome. Usually, such agents omit hypochlorite bleaching as it tends to react with other chemically active ingredients, especially surfactant, thereby degrading the suspending or thixotropic agent and reducing its effectiveness. U.S. Patent No. 4,115,308 discloses thixotropic pastes for automatic washing containing a suspending agent, e.g. CMC, synthetic clays or the like; inorganic salts including silicates, phosphates, polyphosphates, etc., a small amount of surfactant and an antifoaming agent. Bleaching is not described.

U.S. Patent No. 4,147,650 is similar to this, but further includes a hypochlorite bleach. However, the product is described as detergent slurry.

U.S. Patent No. 3,985,668 discloses abrasive, cleansing gels of gel-like consistency containing (1) suspending agent, preferably the smectite and attapulgite types of the colloid-forming clays; (2) abrasive, i.e. silica sand

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3 or perlite; and (3) filler comprising low density crushed polymers, expanded perlite and the like having a lightness and thus stabilizing effect on the agent in addition to serving as a filler, thereby replacing water otherwise available to form undesirable supernatant layers. due to leakage and phase distabi1 in se ing. The foregoing are essential constituents. Optional agents include hypochlorite bleach, bleach stable surfactant and buffer, e.g. silicates, carbonates, monophosphates, etc .. A builder such as NaTPP may be included as an additional optional means of delivering or supplementing the builder function not provided by the buffer, the amount of such builder not exceeding 5% of the total. agent according to the invention. The preservation of the desired levels with pH> 10 is made possible by the buffer / builder components. A high pH is said to minimize the degradation of chlorine bleach and undesirable reaction between surfactant and bleach. When present, NaTPP is limited to 5¾ as indicated.

A foam-destroying agent is not disclosed.

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According to the invention, it has been found that improved cleaners, adapted for use in automatic dishwashers, especially of the type found in the home, are provided with the properties desirable to provide thixotropic, gel-like structure and include each of the various components, it is necessary for effective cleaning in such an automatic dishwasher.

The object of the invention is therefore to provide a thixotropic cleaning agent which is advantageously adapted for use in an automatic dishwasher.

According to the invention, such a means of good physical stability is provided without clearly significant phase separation after standing for prolonged periods.

According to the invention, there is provided such an agent in which problems associated with undesirable reaction between chemical

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active ingredients are removed or at least substantially diminished.

According to the invention, there is provided such an agent having the aforementioned stability under the strong alkaline conditions necessary for effective purification.

According to the invention, there is provided such an agent with improved rheological properties which exhibits high viscosities at low shear rates and lower viscosities at high shear rates - thus advantageously adapted for use in the dispensing vessels of automatic dishwashers.

According to the invention, there is provided such agent having 15 l ave foam characteristics, improved cleaning performance and which are easily dispersible in the dishwasher.

Other advantages of the invention will be apparent from the following description.

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These advantages are obtained according to the invention which, in its wider aspects, provides a usually gelatinous aqueous detergent with thixotropic properties comprising by weight of: (a) 5 to 35% water soluble alkali metal tripolyphosphate 25 having an average degree of hydration from 1 to 5; (b) 2.5 to 20% sodium silicate; (c) 0 to 9% of water-soluble alkali metal carbonate; (d) 0.1 to 5% bleach-stable, water-dispersible organic surfactant; (e) 0.1 to 0.5% mono- or di- (C1-C18) alkyl ester of phosphoric acid decomposer; (f) 3-20% NaOCl solution with 13% available Cl; (g) 1.5 to 10% inorganic, colloid-forming clay thickener; and (h) sufficient sodium hydroxide to achieve a pH of 10.5-13.5, said agent having a thixotropy index of about 2.5 to 10.

Thus, ADD composites are de-foaming; stable, both chemically and physically; are readily soluble in the washing medium and most effective

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effective at pH values that best contribute to improved purifying effect, namely pH 10.5-13.5. The agents usually have gel consistency, ie. a high-viscosity, opaque jelly-like material with Bingham plastic character and thus 5 relatively high utilization rate. Therefore, a certain displacement force is needed to start or increase the flow, which can be achieved by a moving automatic dishwasher's moving dosing container. Under such conditions, the agent is rapidly liquidized and readily distributed. When the shear force is interrupted, the agent quickly regains a high viscosity,

Bingham plastic mode that closely approximates its previous past texture.

In general, the ADD efficiency is directly associated with (a) ten 1-15 commonly available chloride amounts; (b) alkalinity; (c) solubility in a washing medium; and (d) the antifoaming efficiency, it being important herein that the pH value of the ADD be from about 10.5 to 13.5 and preferably at least approx. 11.5. The use of NaOH herein is therefore significant as the pH of ADD is below 10.5 without NaOH.

At this pH, the ADD product is for viscous, i.e. solids-like, and therefore cannot be readily liquidized under the shear stress levels formed in the metering vessel under normal machine operating conditions. Actually, the drug loses much, if not all, of its thixotropic character.

Thus, in this case, addition of NaOH is essential to increase the pH and flowability properties. The presence of carbonate is often necessary herein as it acts as a buffer which allows the maintenance of the required pH value. However, excess carbonate must be avoided as it may cause the formation of needle-like carbonate crystals and thereby impair the stability and / or functional iona 1 of the density of the ADD product. Caustic soda serves the additional essential function of neutralizing the phosphoric acid ester foam exchanger.

Other criteria governing the selection of constituents herein and essential for providing a stable effective ADD product with thixotropic properties are as follows; NaTPP must be 6

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free of heavy metal, as it tends to degrade sodium umhypochl or in t. On average, NaTPP contains approx. 1-15% by weight of water, corresponding to an average degree of hydration of approx. 1 to 5. If only the hexahydrate is used, the detergent product is liquid and has little or no thixotropic character. ter. If only anhydrous NaTPP is used, the product is too thick and therefore unsuitable. Effective agents contain, for example, using a 0.5: 1 to 2: 1 weight ratio anhydrous to hexahydrated NaTPP; values of approx. 1: 1 is particularly preferred. Foam-10 dampening agents are needed to increase the efficiency of the dishwashers and to reduce the ustabi1 in serous effects that may occur due to the presence of excess foam in the washing machine during use. Available amounts of chloride are added thereto by means of sodium hypochlorite, rather than e.g. dichloroisocyanurates used in common powder detergents.

The ADD product exhibits improved rheological properties as assessed by testing the product viscosity as a function of shear rate. Investigation confirms that the agents exhibit higher viscosity at low shear rate and lower viscosity at high shear rate, the data indicating effective fluidization and gelation within the shear rates existing in the dishwasher. In practice, this means improved flow and machining characteristics as well as less outflow in the machine's distributing space, compared to commonly used liquid ADD products. For shear rates used corresponding to 3 to 30 rpm. per minute, viscosities (Brookfield) equal to approx. 15,000-30,000 cps to approx. 3000-5000 30 cps measured at room temperature using a LVT Brookfield viscometer after 3 minutes using a # 4 spindle. A shear rate of 7.4 sec. * Corresponds to one spindle rotation per minute of approx. 3. An increase of approx. ten times the shear rate provides a six to seven times the viscosity reduction. With commonly used ADD gels, the corresponding reduction in viscosity is only approx. twice. By such means the initial viscosity is taken at 7

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ca. 3 rpm minute, moreover only approx. 2500-2700 cps.

Thus, the instant acting agents exhibit initial fluctuations at lower shear rates and of significantly greater expression in incremental increases in shear rate versus stepwise decrease in viscosity. This property of immediate-acting ADD products is summarized in terms of a thixotropy index (TI), which measures the ratio of (a) apparent viscosity at 3 rpm. and (b) apparent viscosity at 30 rpm. minute. The present agents have a TI of from ca.

2.5 to 10 and preferably 6 to 8. Each of the tested ADD agents showed significant and rapid return to consistency in a previously calm state when the shear force was interrupted.

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When making the ADD product, one must first dissolve or disperse all the inorganic salts, ie. carbonates, silicates and tripolyphosphates in the aqueous medium. Thickener is finally added. The antifoaming phosphoric acid ester 20 is initially provided as an aqueous dispersion, as is the thickener. The ester dispersion, caustic soda, and inorganic salts are first mixed at elevated temperatures in aqueous solution (deionized water) and then cooled, using stirring constantly.

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Bleach, surfactant and thickener dispersion at room temperature are then added to the cooled (25-35 ° C) solution. The amount of water used is such that an A.I. concentration in the ADD product from about 30 ca. 35-75%, with an interval of approx. 50-65% is preferred.

The inorganic salts herein include by weight of the total product: (a) 5 to 35% and preferably about 20 to 30% NaTPP; (b) 2.5 to 20% and preferably approx. 10 to 15% sodium silicate with a Na 2 O: SiO 2 ratio of approx. 0.3 to 0.5%, and (c) 0 to 9%, preferably approx. 4 to 7%, alkali metal carbonate, preferably sodium carbonate. These salts should cause a total salt concentration of approx. 20 to 50% and preferably approx. 35 to 45%.

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The bleach comprises sodium hypochlorite (NaOCl) solution with 13% available Cl in amounts of 3-20%, preferably approx. 7-12%.

Caustic soda should, as mentioned, be sufficient to maintain a pH of 10.5 to approx. 13.5 and preferably 11.5 to approx. 12.7. In general, these quantities will be approx. 0.5 to 3%, and in all cases at least sufficient to neutralize the antifoaming phosphoric acid ester.

The preferred antifoaming agent comprises mono- and / or di-C 16 -C 18 alkyl esters of phosphoric acid in a range of 0.1 to 0.5% and preferably about 0.15 to 0.3%, with specific amounts depending in part on the amount of the surfactant present.

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Surfactants useful herein must be stable in the presence of hypochlorite bleach and preferably include agents of the anionic, amine oxide, phosphine oxide, sulfoxide and betaine types, the first being the most preferred. They are used in amounts ranging from 0.1 to 5% and preferably about

0.3 to 0.8%. To ensure sufficient foam suppression, it is generally advisable to maintain a surfactant: antifoam, weight ratio of approx. 10: 1 to 1: 1 and preferably approx. 1.5: 1 to 4: 1. Particularly preferred surfactants herein are the similar or branched alkali metal mono- and / or di-C8-4 alkyldiphenyloxide mono- and / or disulfonates which are commercially available, e.g. such as D0WFAX 3B-2 and D0WFAX 2A-1. Usually, the paraffin sulfonates tend to attenuate, if not degrade, thixotropy, as they have been shown to inappropriately increase viscosity, which. causing serious shear force problems. In addition, the surfactant must be compatible with the other constituents of the agent. Other suitable surfactants include primary alkyl sulfates, alkyl sulfonates, alkylarylsulfonates and secondary alkyl sulfates. Examples thereof are sodium C 10 -C 18 alkyl sulfates such as sodium dodecyl sulfate, sodium tallow alcohol sulfate, sodium C 1 -C 8 alkanesulfonates such as sodium hexadecyl-1-sulfonate; sodium C12- C18 alkylbenzenesulfonates such as sodium docecylbenzenesulfonate and the corresponding potassium salts.

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Examples of other suitable surfactants may be mentioned amine oxide surfactants having the structure F 1 R 2 NO wherein each R is a lower alkyl group, e.g. is a long chain alkyl group having from 8 to 22 carbon atoms, e.g. a lauryl, myristyl, palmityl or cetyl group. Instead of an amino oxide, a corresponding surfactant phosphine oxide R2R * PO or sulfoxide RRlSO can be used. Betaine surfactants typically have the structure R2R1N + R "C00- wherein each R is a lower alkyl group, R 1 is a long chain alkyl group, and R" is an alkylene group having from 1 to 5 carbon atoms. Specific examples of these surfactants are lauryl dimethyl amine oxide, myristyldimethyl amine oxide, coconut dimethyl amine oxide, cured tallow dimethyl amine oxide, the corresponding phosphine oxides and sulfoxides, and the corresponding betaines including dodecyl dimethyl ammonium diacetamethyl acetate similar. For the biodegradability, the alkyls in these surfactants must be straight-chain and preferred.

Surfactants of the type mentioned are all known and are e.g. disclosed in U.S. Patent Nos. 3,985,668 and 4,271,030.

Thickening or suspending agents useful herein usually include the inorganic colloid-forming clays 30 of smectite and / or attapulgite type, the first being preferred. These materials affect the rheological properties of the agent and are used in amounts ranging from approx. 2.5 to 4%, the amount selected being sufficient in all cases to impart the desired Bingham plastic character. Smecti tier species include montmoronite (bentonite), the preferred species of hectorite, saponite and the like. Materials of this type are available under the trademarks such as "Thixogel" # 1 and "Qelwhite" GP from 10

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Georgia Kaolin Company (both are montmorillonites). Attapul gratings include the materials commercially available under the trademark "Attagel", i.e. "Attagel" 40, "Attagel" 50, and "Attagel" 150 from Engelhard Minerals and Chemicals Corporation.

Mixtures of smectite and attapulgite in the 4: 1 to 1: 5 weight ratio are useful herein.

Suspension agents of the aforementioned type are known and are e.g. disclosed in said United States Patent No. 3,985,668.

Other ingredients useful in the immediate-acting ADD agents include dyes to provide a pleasantly colored agent. Particularly preferred are chlorinated phthalocyanines and polysulfides of aluminum silicates, which provide green and blue hues, respectively.

The following example illustrates the invention. Percentages 20 herein are by weight and are based on the total product unless otherwise stated.

Example 25 A first dispersion of an antifoaming agent comprising a 2: 1 mixture of mono- and di- (C 1 -C 3 g) alkyl ester of phosphoric acid, 0.16 g, in 6 g of water is prepared by mixing at 60 30 minutes using a plate-shaped stirrer. This dispersion is referred to as Part I.

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A first dispersion of GELWHITE GP (hydration) thickener, 3 g in 17 g of water, is prepared by mixing at 70 ° C for 10 minutes using a mixer with Z-shaped stirrer. This dispersion is referred to as Part 2.

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The following ingredients are mixed in a Giusti blend at 50-60 ° C: 11

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_% _ AI%

Deionized water 16.9

Part I 6.16 0.16

Caustic soda solution, 49% NaOH 2.40 1.2 5 Sodium carbonate 7.00 7.0

Sodium silicate (1: 2.4) solution - 47.5% solid 13.74 6.5

Sodium TPP (mainly anhydrous) * 12.00 11.54

Sodium TPP (hexahydrate) 12.00 9.36 10

The mixture is cooled to 25-30 ° C with continuous stirring and the following ingredients are added at room temperature.

Sodium hypochlorite solution - 13 13% to gtchlorine in gtchlor 7.615 1.0

Part 2 (dispersed with high speed turbine) 20.00 3.0

Dowfax 3B-2 ** 0.80 0.36 * ie. containing 0-5%, especially 3%, moisture.

20 ** sodium monodecyl / didecyl disulfonated diphenyloxide, 45% AI.

An opaque agent (about 40% AI) with a gel-like consistency is obtained. The agent is intended to have a TI of approx. 7, in accordance with the method previously described herein, based on apparent viscosity values of 28,000 cps and 4000 cps at 3 rpm, respectively. per minute and 30 rpm. minute. When tested in an automatic dishwasher equipped with a distributor compartment, the above-mentioned agent exhibits an excellent purifying effect and is easily and quickly distributed. The agent is found to be satisfactory non-foaming. Little or no phase separation is observed after prolonged standing in a closed container. The pH of the agent, measured as a 1% solution in water, is 11.6. When performing the shear test assessments, it is noted that the agent quickly returns to the consistency of its previous resting state, giving rise to no appreciable loss of yield when 12

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it is tested within the limits previously described herein, i.e. within shear force limits, at least approximating those found in an activated automatic dishwasher. There is no noticeable difference when distributing the ADD product using a clamping tube, rather than a distribution room.

The example illustrating a total polyphosphate carbonate si 1 in cat concentrate in on of about 37% is repeated, but the total concentration of such salts is varied within the limits previously stated. The best results are obtained at a combined salt concentration of at least approx. 30% and especially when the sodium polyphosphate concentration is at least approx. 20%. Higher silicate concentrations are desirable to protect porcelain glaze and patterns, providing greater alkalinity, which can be appropriately compensated for by reducing the caustic soda concentration and / or controlling the sodium carbonate (buffer) concentration. As a result, the agent appears to be most sensitive to changes in NaTPP concentration (the higher concentration range is more effective) as well as its degree of hydration. Changes in surfactant concentration generally require similar and direct changes in the antifoam concentration to achieve the desired low foaming levels.

Lowering the pH of the agent to below 10.5 results in a noticeable decrease in the efficiency of the agent, as well as a corresponding decrease in the flowability.

Similar results are obtained when the procedure of the example is repeated, replacing corresponding constituents with alkyl sulfate surfactant, e.g. sodium cocosalkyl sulfate, attapulgitles, e.g. "Attagel" 50; and 2 ·. 1 mixture of montmoronite and "Attagel" 50. The addition of small amounts, e.g. 0.003-0.05% of chlorinated phthalocyanine and aluminum screen in cat dyes respectively of the example (including the first thickener dispersion or sat.

Claims (12)

1. Aqueous dishwashing detergent, characterized in that it contains, by weight: 1 to 5; (b) 2.5 to 20% sodium silicate; (c) 0 to 9% water-soluble alkali metal carbonate; (d) 0.1 to 5% bleach partially stable water dispersible organic surfactant; (e) 0.1 to 0.5% mono- and / or di- (C1-6-C1) alkyl ester of phosphoric acid antifoaming agent; (f) 3-20% NaOCl solution with 13% available Cl; (g) 1.5 to 10% inorganic, colloid-forming clay thickener; and (h) sufficient sodium hydroxide to provide a pH of 10.5 to about The phosphoric acid ester amount is sufficient to provide foaming properties, the sodium hydroxide amount is at least sufficient to neutralize said phosphoric acid ester, and the agent has a thixotropy index as defined in the description of ca. 2.5 to 10. Agent according to claim 1, characterized in that the weight ratio of surfactant to antifoaming agent is approx. 10: 1 - 1: 1. An agent according to claim 1, characterized in that the total concentration of tripolyphosphate, silicate and carbonate 30 is at least approx. 20%. An agent according to claim 3, characterized in that the concentration of tripolyphosphate is approx. 20 to 30%. An agent according to claim 1, characterized in that the tripolyphosphate comprises a mixture of the substantially anhydrous form and the hexahydrate in a weight ratio of approx. 1: 2 to 2: 1. DK 158155 B A composition according to claim 5, characterized in that said weight ratio is approx. 1: 1. Agent according to claim 1, characterized in that it further contains a tinting amount of dye. An agent according to claim 1, characterized in that said thickening agent is a smectite and / or attapulgit clay species. An agent according to claim 1, characterized in that the surfactant is an alkali metal Cq to C3 -alkyldi-phenyl oxide sulphonate. An agent according to claim 1, characterized in that the tri-polyphosphate is a sodium tripolyphosphate; the carbonate is sodium carbonate; the surfactant is a mixture of mono- and di-CC-C] alkyl alkyl) diphenyloxide disulfonates, and the thickener is bentonite. A composition according to claim 10, characterized in that it has a pH of approx. 11.5 to approx. 12.7. Agent according to claim 10, characterized in that it has a thixotropy index of approx. 6 to 8. 25 30 35