GRANULAR DETERGENTS WHICH CONTAIN HIGH LEVELS OF ANIONIC SURFACTANT

Abstract: Detergent granules containing more than about 18% of anionic surfactant that forms a sticky middle phase are surface treated with a small amount of water soluble quaternary ammonium salt in an aqueous solution to improve the dissolving characteristics of the composition.

Description: TECHNICAL FIELD The present invention relates to granular detergent compositions containing high levels of anionic surfactant which form a middle phase. Preferably the detergent composition is spray-dried. The compositions are prepared by forming an aqueous slurry of anionic surfactant and inorganic salts and then spray-drying the slurry. The granules are then sprayed with aqueous solutions of the indicated surface modifier, which allows the granular detergent compositions to dissolve or disperse more rapidly in a laundering solution. Granular detergents made using conventional spray-drying processes generally have satisfactory solubility, if the individual components are soluble or dispersible in water, due to their substantial porosity. However, spray-dried detergents containing high levels of anionic surfactants often have low solubility rates because anionic surfactants tend to form a sticky middle-phase when they contact the laundering solution. This can result in noticeable undissolved detergent globs on fabrics. The primary object of the present invention is to improve the solubility of spray-dried granular detergents containing high levels of anionic surfactants which form a middle-phase. The invention is, however, also applicable to granular detergents made by agglomerating high levels of the same anionic surfactants with a neutral or alkaline salt. SUMMARY OF THE INVENTION According to the present invention there is provided a particulate detergent composition comprising (a) from 18% to 50% by weight of anionic surfactant which forms a sticky middle-phase; and (b) from 50% to 82% by weight of other detergent ingredients, including a water soluble quaternary ammonium surfactant salt; wherein said anionic surfactant and detergent components other than the quaternary ammonium surfactant salt comprise a granulate and in that the surfaces of said granulate bear from 0.1% to 2% by weight of the particulate composition of a surface modifier consisting of one or more water soluble quaternary ammonium salts each containing one C₁₀₋C₁₄ alkyl group and three each containing one C₁₀₋C₁₄ alkyl group and three methyl, ethyl or hydroxyethyl groups, the total number of carbon atoms in the salt being from 13 to 17, said surface modifier being applied to the surfaces of said granulate as an aqueous solution. DETAILED DESCRIPTION OF THE INVENTION The granular detergent compositions of the present invention contain at least 18% of at least one anionic surfactant that forms a sticky middle phase and a major portion of water-soluble neutral or alkaline salt. The compositions are preferably prepared by forming a slurry of the anionic surfactants and neutral or alkaline salts and spray drying. Granule formation can also be accomplished by agitating in the presence of a suitable binder or by mechanically mixing under pressure (e.g., extruding, pressing, milling, compacting or pelletizing). Anionic Surfactant The detergent compositions herein contain from 18% to 50% by weight of anionic surfactant, or mixtures thereof. The anionic surfactant preferably represents from 18% to 40%, and more preferably from 20% to 30%, by weight of the detergent composition. Anionic surfactants useful herein are disclosed in U.S. Patent 3,664,961, Norris, issued May 23, 1972, and in U.S. Patent 3,919,678, Laughlin et al, issued December 30, 1975. Useful anionic surfactants include the water-soluble salts, particularly the alkali metal, ammonium and alkylolammonium salts, of organic sulfuric reaction products having in their molecular structure an alkyl group containing from 10 to 20 carbon atoms and a sulfonic acid or sulfuric acid ester group. (Included in the term "alkyl" is the alkyl portion of aryl groups.) Examples of this group of synthetic surfactants are the sodium and potassium alkyl sulfates, especially those obtained by sulfating the higher alcohols (C₈-C₁₈ carbon atoms) such as those produced by reducing the glycerides of tallow or coconut oil; and the sodium and potassium alkylbenzene sulfonates in which the alkyl group contains from 9 to 15 carbon atoms, in straight chain or branched chain configuration, e.g., those of the type described in United States Patents 2,220,099 and 2,477,383. Especially valuable are linear straight chain alkylbenzene sulfonates in which the average number of carbon atoms in the alkyl group is from 11 to 13, abbreviated as C₁₁₋₁₃LAS. Water-soluble salts of 2-acyloxy-alkane-l-sulfonic acids containing from 2 to 9 carbon atoms in the acyl group and from 9 to 23 carbon atoms in the alkane moiety; water-soluble salts of olefin sulfonates containing from 12 to 24 carbon atoms; and β-alkyloxy alkane sulfonates containing from 1 to 3 carbon atoms in the alkyl group and from 8 to 20 carbon atoms in the alkane moiety. Water-soluble salts of the higher fatty acids, i . e., "soaps", also are useful anionic surfactants herein. Soaps can be made by direct saponification of fats and oils or by the neutralization of free fatty acids. Examples of soaps are the sodium, potassium, ammonium, and alkylolammonium salts of higher fatty acids containing from 8 to 24 carbon atoms, and preferably from 12 to 18 carbon atoms. Particularly useful are the sodium and potassium salts of the mixtures of fatty acids derived from coconut oil and tallow, i. e., sodium or potassium tallow and coconut soaps. Particularly preferred anionic surfactants are the alkali metal (especially sodium) salts of C₁₁₋₁₃ alkylbenzene sulfonates, C₁₄₋₁₈ alkyl sulfates, and mixtures thereof. The Quaternary Ammonium Salt The quaternary ammonium salt is one which dissolves readily in water and comprises one alkyl group containing from 10 to 14 carbon atoms, and the three shorter alkyl groups contain no more than 2 carbon atoms, the total number of carbon atoms being from 13 to about 17. The ethyl group can also contain a hydroxy group in place of a hydrogen atom. Suitable examples of quaternary ammonium salts are coconut alkyl trimethyl ammonium chloride, acetate, or sulfate and dodecyl trimethyl ammonium chloride, acetate or sulfate. Mixtures of salts are useful and desirable. Water-Soluble Neutral or Alkaline Salt The granular detergents of the present invention also contain from 30% to 75%, preferably from 40% to 60% , and more preferably from 45% to 50%, by weight of one or more water-soluble neutral or alkaline salts. Neutral or alkaline salts have a pH in solution of about seven or greater, and can be either organic or inorganic in nature. The salt assists in providing the desired density and bulk to the detergent granules herein. While some of the salts are inert, many of them also function as detergency builder materials in the laundering solution. Preferably, the salts are inorganic. Examples of neutral water-soluble salts include the alkali metal, ammonium or substituted ammonium chlorides and sulfates. The alkali metal, and especially sodium, salts of the above are preferred. Sodium sulfate is typically found in detergent granules and is a preferred salt herein. It is usually formed during the sulfation/sulfonation and neutralization steps in the production of anionic synthetic surfactants. Other useful water-soluble salts include the compounds commonly known as detergent builder materials. Builders are generally selected from the various water-soluble, alkali metal, ammonium or substituted ammonium phosphates, polyphosphates, phosphonates, polyphosphonates, carbonates, silicates, borates, polyhydroxy sulfonates, polyacetates, carboxylates, and polycarboxylates. Preferred are the alkali metal, especially sodium, salts of the above. Specific examples of inorganic phosphate builders are sodium and potassium tripolyphosphate, pyrophosphate, polymeric metaphosphate having a degree of polymerization of from 6 to 21, and orthophosphate. Examples of polyphosphonate builders are the sodium and potassium salts of ethylene diphosphonic acid, the sodium and potassium salts of ethane 1-hydroxy-1, 1-diphosphonic acid and the sodium and potassium salts of ethane, 1,1,2-triphosphonic acid. Other phosphorus builder compounds are disclosed in U.S. Patents 3,159,581; 3,213,030; 3,422,021; 3,422,137; 3,400,176; and 3,400,148. Examples of nonphosphorus, inorganic builders are sodium and potassium carbonate, bicarbonate, sesquicarbonate, tetraborate decahydrate, and silicates having a weight ratio of SiO₂ to alkali metal oxide of from 0.5 to 4.0, preferably from 1.0 to 2.4. Water-soluble, nonphosphorus organic builders useful herein include the various alkali metal, ammonium and substituted ammonium polyacetates, carboxylates, polycarboxylates and polyhydroxy sulfonates. Examples of polyacetate and polycarboxylate builders are the sodium, potassium, lithium, ammonium and substituted ammonium salts of ethylenediaminetetraacetic acid, nitrilotriacetic acid, oxydisuccinic acid, mellitic acid, benzene polycarboxylic acids, and citric acid. Salts of nitrilotriacetic acid, such as sodium nitrilotriacetate, are particularly preferred. Polymeric polycarboxylate builders are set forth in U.S. Patent 3,308,067, Diehl, issued March 7, 1967. Such materials include the water-soluble salts of homo- and copolymers of aliphatic carboxylic acids such as maleic acid, itaconic acid, mesaconic acid, fumaric acid, aconitic acid, citraconic acid and methylenemalonic acid. Other useful builders herein are sodium and potassium carboxymethyloxymalonate, carboxymethyloxysuccinate, cis-cyclohexanehexacarboxylate, cis-cyclopentanetetracarboxylate, phloroglucinol trisulfonate, and the copolymers of maleic anhydride with vinyl methyl ether or ethylene. Other suitable polycarboxylates for use herein are the polyacetal carboxylates described in U.S. Patent 4,144,226, issued March 13, 1979 to Crutchfield et al, and U.S. Patent 4,246,495, issued March 27, 1979 to Crutchfield et al. These polyacetal carboxylates can be prepared by bringing together under polymerization conditions an ester of glyoxylic acid and a polymerization initiator. The resulting polyacetal carboxylate ester is then attached to chemically stable end groups to stabilize the polyacetal carboxylate against rapid depolymerization in alkaline solution and converted to the corresponding salt. The neutral or alkaline salt of the present invention is preferably selected from alkali metal polyphosphates, nitrilotriacetates, carbonates, silicates, sulfates, and mixtures thereof. Optional Components Other ingredients commonly used in detergent compositions can be included in the compositions of the present invention. These include auxiliary detergent surfactant and builder materials, color speckles, bleaching agents, and bleach activators, suds boosters or suds suppressors, anti-tarnish and anti-corrosion agents, soil suspending agents, soil release agents, dyes, fillers, optical brighteners, germicides, pH adjusting agents, non-builder alkalinity sources, enzymes, enzyme-stabilizing agents and perfumes. An optional builder herein is a water-insoluble crystalline or amorphous aluminosilicate ion exchange material. The preferred crystalline material useful herein is of the formula Na z [(AlO₂) z ·(SiO₂) y ]·xH₂O wherein z and y are at least 6, the molar ratio of z to y is from 1.0 to 0.5 and x is from 10 t o 264. Amorphous hydrated aluminosilicate materials useful herein have the empirical formula M z ( z AlO₂·ySiO₂) wherein M is sodium, potassium, ammonium or substituted ammonium, z is from 0.5 to 2 and y is 1, said material having a magnesium ion exchange capacity of at least 50 milligram equivalents of CaCO₃ hardness per gram of anhydrous aluminosilicate. The aluminosilicate ion exchange builder materials herein are in hydrated form and contain from 10% to 28% of water by weight if crystalline, and potentially even higher amounts of water if amorphous. Highly preferred crystalline aluminosilicate ion exchange materials contain from 18% to 22% water in their crystal matrix. The crystalline aluminosilicate ion exchange materials are further characterized by a particle size diameter of from 0.1 micrometers to 10 micrometers. Amorphous materials are often smaller, e.g., down to less than 0.1 micrometers. Preferred ion exchange materials have a particle size diameter of from 0.2 micrometers to 4 micrometers. The term "particle size diameter" herein represents the average particle size diameter of a given ion exchange material as determined by conventional analytical techniques such as, for example, microscopic determination utilizing a scanning electron microscope. The crystalline aluminosilicate ion exchange materials herein are usually further characterized by their calcium ion exchange capacity, which is at least 200 mg equivalent of CaCO₃ water hardness/g of aluminosilicate, calculated on an anhydrous basis, and which generally is in the range of from 300 mg eq./g to 352 mg eq./g The aluminosilicate ion exchange materials herein are still further characterized by their calcium ion exchange rate which is at least 130 mg equiv. of CaCO₃/litre/ minute/g/litre of aluminosilicate (anhydrous basis), and generally lies within the range of from 130 to 390 mg of CaCO₃/litre/ minute/g/litre based on calcium ion hardness. Optimum aluminosilicate for builder purposes exhibit a calcium ion exchange rate of at least 260 mg equiv. of CaCO₃/litre/minute/g/litre. The amorphous aluminosilicate ion exchange materials usually have a Mg⁺⁺ exchange capacity of at least 50 mg. eq. CaCO₃/g (12 mg Mg⁺⁺/g) and a Mg⁺⁺ exchange rate of at least 65 mg equiv. of MgCO₃/litre/minute/g/litre. Amorphous materials do not exhibit an observable diffraction pattern when examined by Cu radiation (1.54 x 10⁻¹⁰m ). Aluminosilicate ion exchange materials useful in the practice of this invention are commercially available. The aluminosilicates useful in this invention can be crystalline or amorphous in structure and can be naturally-occurring aluminosilicates or synthetically derived. A method for producing aluminosilicate ion exchange materials is discussed in U.S. Patent 3,985,669, Krummel, et al., issued October 12, 1976. Preferred synthetic crystalline aluminosilicate ion exchange materials useful herein are available under the designations Zeolite A, Zeolite B, and Zeolite X. In an especially preferred embodiment, the crystalline aluminosilicate ion exchange material has the formula Na₁₂(AlO₂)₁₂(SiO₂)₁₂]·xH₂O wherein x is from 20 to 30, especially 27. The following non-limiting example illustrates the detergent compositions of the present invention. All percentages, parts, and ratios used herein are by weight unless otherwise specified. EXAMPLE Spray dried detergent granules were prepared containing 20% of a 1:1 mixture of sodium C₁₃ linear alkyl benzene sulfonate and sodium C₁₄₋₁₅ alkyl sulfate; 24.4% of hydrated sodium Zeolite A; 1.8% of 1.6 ratio sodium silicate; 5% sodium carbonate; 36.2% sodium sulfate; 1.5% sodium acrylate (4500 molecular weight); 1.1% sodium tallow soap; 1.5% polyethylene glycol (8000 molecular weight); and the balance moisture and minors. These granules (A) were the control. They were compared with granules that were surface treated with 0.1% (B); 0.25% (C); 0.5% (D) and 1% (E) aqueous solutions respectively of C₁₂ alkyl trimethyl ammonium chloride in a "pocket solubility" test. In this test, prewashed pockets containing approximately ¼ of the recommended usage were closed and placed in a washing machine containing 66 l (17.5 gal.) of city water. After the pockets sink, the washer is placed on the gently cycle for 10 minutes. The pockets are then opened, spread out to dry and evaluated using a scale in which 0 is fabric almost completely covered with undissolved detergent and 7 is fabric showing no evidence of undissolved detergent. The results were as follows:

Claims: A particulate detergent composition comprising (a) from 18% to 50% by weight of anionic surfactant which forms a sticky middle-phase; and (b) from 50% to 82% by weight of other detergent ingredients, including a water soluble quaternary ammonium surfactant salt; characterised in that said anionic surfactant and detergent components other than the quaternary ammonium surfactant salt comprise a granulate and in that the surfaces of said granulate bear from 0.1% to 2% by weight of the particulate composition of a surface modifier consisting of one or more water soluble quaternary ammonium salts each containing one C₁₀-C₁₄ alkyl group and three methyl, ethyl or hydroxyethyl groups, the total number of carbon atoms in the salt being from 13 to 17, said surface modifier being applied to the surfaces of said granulate as an aqueous solution. A composition according to claim 1 wherein said anionic surfactant is selected from alkali metal salts of C₁₁-C₁₃ alkyl benzene sulfonates, C₁₄-C₁₈ alkyl sulfates, and mixtures thereof. A composition according to either one of claims 1 and 2, containing from 18% to 40% of said anionic surfactant. A composition according to any one of claims 1-3 containing from 0.5% to 1% of said water soluble quaternary ammonium surfactant salt. A method of preparing a particulate detergent composition according to claim 1 comprising the steps of: (I) forming a granulate composed of (a) the anionic surfactant which forms a sticky middle-phase; and (b) the other detergent ingredients apart from the surface modifier; and (II) spraying the surfaces of said formed granulate with an aqueous solution of the surface modifier consisting of one or more water soluble quaternary ammonium salts each containing one C₁₀-C₁₄ alkyl group and three methyl, ethyl, or hydroxyethyl groups, the total number of carbon atoms in the salt being from 13 to 17, said aqueous solution containing from 25% to 70% by weight of said salt, and said spraying step being such as to apply from 0.1% to 2% of the surface modifier by weight of the particulate composition. A method according to claim 5 wherein the granulate is formed by spray drying.

Inventors: BLEIL, CHARLES FRANK, MORROW, JOHN EDWARD
Applicants: THE PROCTER & GAMBLE COMPANY
Application year: 1987
Main classification: C11D1
IPC codes: C11D17, C11D1