EP0110592A1

EP0110592A1 - Granular detergents containing pyrophosphate and tripolyphosphate processing aid

Info

Publication number: EP0110592A1
Application number: EP83306758A
Authority: EP
Inventors: Linda Ann Ross; John Edward Morrow
Original assignee: Procter and Gamble Co
Current assignee: Procter and Gamble Co
Priority date: 1982-11-08
Filing date: 1983-11-07
Publication date: 1984-06-13
Also published as: MA19946A1; GR79391B

Abstract

@ Granular detergents containing organic surfactant, pyrophosphate and tripolyphosphate builders at a weight ratio of pyrophosphate to tripolyphosphate of from about 50:1 to about 1:1, and low levels of silicate are disclosed. The compositions are prepared by drying an aqueous slurry of the components, and exhibit improved structure, physical properties and whiteness maintenance due to the incorporation of the tripolyphosphate.

Description

The present invention relates to granular detergents containing an organic surfactant, pyrophosphate and tripolyphosphate builders at a weight ratio of pyrophosphate to tripolyphosphate of from about 50:1 to about 1:1, and low levels of alkali metal silicate. The compositions herein are prepared by drying an aqueous slurry of the components, and exhibit improved granule structure and physical properties due to the incorporation of the tripolyphosphates. The compositions are substantially free of polyacrylate polymer structural aids having a weight average molecular weight of from about 10,000 to about 200,000. While the compositions are also preferably substantially free of orthophosphates, they can contain minor amounts of such material provided the weight ratio of pyrophosphate to orthophosphate is at least about 5:1.
Pyrophosphates are known to be potentially more efficient builders than the tripolyphosphates commonly used in detergents due to their ability to remove more calcium and magnesium ions from the laundering solution per unit of P₂O₅. They do so, however, by precipitating these ions as insoluble phosphates (e.g., dicalcium pyrophosphate), whereas the tripolyphosphates retain them in solution as complex ions. These precipitates can build up on fabrics over a period of time and cause undesirable effects, such as greyness and harshness of feel, unless antiredeposition agents are added to detergents containing pyrophosphates.
Pyrophosphate-built granular detergents have often contained high levels (e.g., 10% by weight) of alkali metal silicates to provide optimum granule structure and processing. It is believed that when a crutcher mix containing silicate is spray-dried, the silicate dries to a tough film capable of cementing finely crystalline granule walls together. This results in granules having very desirable physical properties, i.e., crisp, durable and free-flowing granules. Silicates having lower SiO to alkali metal oxide molar ratios (e.g., 1.6-2.0) are usually selected because they are more water-soluble than the higher ratio silicates. However, exposure of the silicate to carbon dioxide during drying and storage can shift its ratio to a higher value, reducing silicate solubility and resulting in detergent. granules which do not completely disintegrate in the laundering solution.
High levels of silicate in detergents can thus cause an unacceptably high- level of insoluble material being deposited on fabrics. It is apparent that there is a continuing need for the development of pyrophosphate-built granular detergents having acceptable granule structure and solubility, and capable of maintaining fabric whiteness.
U.S. Patent 4,116,852, Bailey et al, issued September 26, 1978, discloses the addition of tripolyphosphates, at levels up to about 15% by weight of the total phosphate, to pyrophosphate-built detergents to improve whiteness maintenance.
Pending U.S. Patent Application, Serial No. 415,098, Morrow et al, filed September 7, 1982, discloses granular detergents containing pyrophosphate, low levels of silicate and a polyacrylate polymer as a structural aid and antiredeposition agent.
Pending U.S. Patent Applications 256,454, Murphy, and 256,453, Kassamali et al, both filed April 22, 1981, disclose the use of film-forming. polymers, including polyacrylates, as structural aids to replace all or part of the silicate in low-phosphate granular detergents containing aluminosilicates.
The present invention encompasses a granular detergent composition comprising:

(a) from about 5% to about 50% by weight of an organic surfactant selected from the group consisting of anionic, nonionic, zwitterionic, ampholytic and cationic surfactants, and mixtures thereof;
(b) from about 5% to about 80% by weight of an alkali metal pyrophosphate builder;
(c) an alkali metal tripolyphosphate builder present at a level such that the weight ratio of pyrophosphate to tripolyphosphate is from about 50:1 to about 1 :1; and
(d) from about 0.5% to about 3% by weight of an alkali metal silicate having a molar ratio of SiO₂ to alkali metal oxide of from about 1.0 to about 3.2;

The granular detergent compositions of the present invention contain, as essential components, an organic surfactant, pyrophosphate and tripolyphosphate builders at a weight ratio of pyrophosphate to tripolyphosphate of from about 50:1 to about 1:1, and an alkali metal silicate. The- compositions herein are substantially free of polyacrylate polymer structural aids having a weight average molecular weight of from about 10,000 to about 200,000. White the compositions can contain minor amounts (e.g., less than about 3%, preferably less than abut 2%, by weight) of other film-forming polymer structural aids, they preferably are substantially free of such materials. In addition, the amount of orthophosphate in the compositions should be limited such that the weight ratio of pyrophosphate to orthophosphate is at least about 5:1, preferably at least about 10:1, and more preferably at least about 20:1. The compositions are most preferably substantially free of orthophosphates because they tend to form coarse precipitates which more readily deposit on fabrics than the pyrophosphate precipitates.
The compositions herein 'are prepared by drying an aqueous slurry comprising the components. The slurry generally contains from about 25% to about 50% water, whereas the dried granules contain from about 2% to about 10%, preferably from about 2% to about 5%, water. The drying operation can be accomplished by any convenient means, such as by -using spray-drying towers, both counter-current and co-current, fluid beds, flash-drying equipment, or industrial microwave or oven-drying equipment. These are more fully described in U.S. Patent 4,019,998, Benson et al, issued April 26, 1977 (particularly from Column 14, line 19 to Column 15, line 9), incorporated herein by reference..
The granular detergents obtained exhibit very desirable structure and physical properties, including improved structural integrity and free-flowing characteristics, and reduced caking tendencies, due to the incorporation of the tripolyphosphates. White not intending to be limited by theory, it is believed that the tripolyphosphates are highly effective moisture sinks which form stable crystalline hexahydrates during drying of the aqueous crutcher-mix slurry. This promotes structural integrity and granule crispness by taking up free moisture, which can otherwise cause sticky or mushy granules. In contrast, pyrophosphates form unstable hydrates that are typically destroyed during the drying operation, freeing moisture to adversely affect granule structure and physical properties. The low level of silicate in the present compositions also contributes to the desired granule structure, and also aids processing and inhibits metal corrosion, without causing excessive insoluble silicate deposition. Finally, the tripolyphosphate contributes to maintaining the whiteness of fabrics laundered using the present compositions.

Organic Surfactant

The detergent compositions herein contain from about 5% to about 50% by weight of an organic surfactant selected from the group consisting of anionic, nonionic, zwitterionic, ampholytic and cationic surfactants, and mixtures thereof. The surfactant preferably represents from about 10% to about 30% by weight of the detergent composition. Surfactants useful herein are listed 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, both incorporated herein by reference. Useful cationic surfactants also include those described in U.S. Patent 4,222,905, Cockrell, issued September 16, 1980, and in U.S. Patent 4,239,659, Murphy, issued December 16, 1980, both incorporated herein by reference.
Water-soluble salts of the higher fatty acids, i.e., "soaps", are useful anionic surfactants in the compositions herein. This includes alkali metal soaps such as the sodium, potassium, ammonium, and substituted ammonium salts of higher fatty acids containing from about 8 to about 24 carbon atoms, and preferably from about 12 to about 18 carbon atoms. Soaps can be made by direct saponification of fats and oils or by the neutralization of free fatty acids. 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 soap.
Useful anionic surfactants also include the water-soluble salts, preferably the alkali metal, ammonium and substituted ammonium salts, of organic sulfuric reaction products having in their molecular structure an alkyl group containing from about 10 to about 20 carbon atoms and a sulfonic acid or sulfuric acid ester group. (Included in the term "alkyl" is the alkyl portion of acyl 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 about 9 to about 15 carbon atoms, in straight chain or branched chain configuration, e.g., those of the type described in U.S. 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 about 11 to 13, abbreviated as C11-13LAS.
Other anionic surfactants herein are the sodium alkyl glyceryl ether sulfonates, especially those ethers of higher alcohols derived from tallow and coconut oil; sodium coconut oil fatty acid monoglyceride sulfonates and sulfates; sodium or potassium salts of alkyl phenol ethylene oxide ether sulfates containing from about 1 to about 10 units of ethylene oxide per molecule and from about 8 to about 12 carbon atoms in the alkyl group; and sodium or potassium salts of alkyl ethylene oxide ether sulfates containing about 1 to about 10 units of ethylene oxide per molecule and from about 10 to about 20 carbon atoms in the alkyl group.
Other useful anionic surfactants include the water-soluble salts of esters of alpha-sulfonated fatty acids containing from about 6 to 20 carbon atoms in the fatty acid group and from about 1 to 10 carbon atoms in the ester group; water-soluble salts of 2-acyloxy-alkane-1-sulforiic acids containing from about 2 to 9 carbon atoms in the acyl group and from about 9 to about 23 carbon atoms in the alkane moiety; alkyl ether sulfates containing from about 10 to 20 carbon atoms in the alkyl group and from about 1 to 30 moles of ethylene oxide; water-soluble salts of olefin sulfonates containing from-about 1.2 to 24 carbon atoms; and beta-alkyloxy alkane sulfonates containing from about 1 to 3 carbon atoms in the alkyl group and from about 8 to 20 carbon atoms in the alkane moiety.
Water-soluble nonionic surfactants are also useful in the compositions _of the invention. Such nonionic materials include compounds produced by the condensation of alkylene oxide groups (hydrophilic in nature) with an organic hydrophobic compound, which may be aliphatic or alkyl aromatic in nature. The length of the polyoxyalkylene group which is condensed with any particular hydrophobic group can be readily adjusted to yield a water-soluble compound having the desired degree of balance between hydrophilic and hydrophobic elements.
Suitable nonionic surfactants include the polyethylene oxide condensates of alkyl phenots, e.g., the condensation products of alkyl phenols having an alkyl group containing from about 6 to 15 carbon atoms, in either a straight chain or branched chain configuration, with from about 3 to 12 moles of ethylene oxide per mole of alkyl phenol.
Preferred nonionics are the water-soluble condensation products of aliphatic alcohols containing from 8 to 22 carbon atoms, in either straight chain or branched configuration, with from. 3 to 12 moles of ethylene oxide per mole of alcohol. Particularly preferred are the condensation products of alcohols having an alkyl group containing from about 9 to 15 carbon atoms with from about 4 to 8 moles of ethylene oxide per mole of alcohol.
Semi-polar nonionic surfactants useful herein include water-soluble amine oxides containing one alkyl moiety of from about 10 to 18 carbon atoms and two moieties selected from the group consisting of alkyl groups and hydroxyalkyl groups containing from 1 to 3 carbon atoms; water-soluble phosphine oxides containing one alkyl moiety of about 10 to 18 carbon atoms. and two moieties selected from the group consisting of alkyl groups and hydroxyalkyl- groups containing from about 1 to 3 carbon atoms; and water-soluble sulfoxides containing one alkyl moiety of from about 10 to 18 carbon atoms and a moiety selected from the group consisting of alkyl- and hydroxyalkyl moieties of from about 1 to 3 carbon atoms.
Ampholytic surfactants include derivatives of aliphatic or aliphatic derivatives of heterocyclic secondary and tertiary amines in which the aliphatic moiety can be straight chain or branched and wherein one of the aliphatic substituents contains from about 8 to 18 carbon atoms and at least one aliphatic substituent contains an anionic water-solubilizing group.
Zwitterionic surfactants include derivatives of aliphatic quaternary ammonium, phosphonium, and sulfonium compounds in which one of the aliphatic substituents contains from about 8 to 13 carbon atoms.
Particularly preferred surfactants herein are anionic surfactants selected from the group consisting of the alkali metal sa!ts of C_11-13 alkylbenzene sulfonates, C_14-18 alkyl sulfates, C_14-18 alkyl linear polyethoxy sulfates containing from about 1 to about 4 moles of ethylene oxide, and mixtures thereof.

Pyrophosphate Builder

The compositions of the present invention also contain from about 5% to about 80%, preferably from about 10% to about 70%, and most preferably from about 15% to about 60%, by weight of an alkali metal pyrophosphate builder. Sodium and potassium, particularly sodium, pyrophosphates are preferred. The pyrophosphate salts useful herein can be obtained commercially or can be formed by neutralization of the corresponding pyrophosphoric acids or acid salts. The pyrophosphates can be anhydrous or hydrated, although anhydrous pyrophosphates in finely divided form are preferred for rapid dissolution in wash.
Readily available commercially are tetrasodium pyrophosphate Na₄P₂O₇ and its decahydrate Na₄P₂O₇.10H₂O, tetrapotassium pyrophosphate K₄P₂0_7' sodium acid pyrophosphate or "acid pyro" ^Na ₂ ^H ₂ ^P ₂ ⁰ ₇ and its hexahydrate Na₂H₂P₂O₇.6H₂O, and pyrophosphoric acid H₄P₂O₇. Monosodium pyrophosphate and trisodium pyrophosphate also exist, the latter as the anhydrous form or the mono-or nona-hydrate. The generic formula for the anhydrous forms of these compounds can be expressed as M_XH_YP₂P₇, where M is alkali metal and x and y are integers having the sum of 4.

Tripolyphosphate Builder

The compositions contain an alkali metal, preferably sodium, tripolyphosphate builder, at a weight ratio of pyrophosphate to tripolyphosphate of from about 50:1 to about 1:1, preferably from about 20: to about 2:1, and more preferably from about 10:1 to about 4:1. A particularly preferred mixture containing about 85% pyrophosphate and 15% tripolyphosphate provides important processing and whiteness maintenance benefits without significantly reducing the builder efficiency advantages provided by the pyrophosphates.

Alkali Metal Silicate

The compositions herein contain from about 0.5% to about 3%, preferably from about 1% to about 2.5%, and most preferably from about 1.5% to abut 2%, by weight of an alkali metal silicate having a molar ratio of SiO₂ to alkali metal oxide of from about 1.0 to abut 3.2, preferably from abut 1.6 to abut 2.4. Sodium silicate, particularly having a molar ratio of from about 1.8 to about 2.2, is preferred.
The alkali metal silicates can be purchased in either liquid or granular form. Silicate slurries can conveniently be used to avoid having to dissolve the dried form in the aqueous slurry (e.g., crutcher mix) of the components herein.

Optional Components

Other ingredients commonly used in granular detergent compositions can be included in the compositions of the present invention. These include cobuilders, color speckles, bleaching agents and bleach activators, suds boosters or suds suppressors, anti-tarnish and anti-corrosion agents, soil release agents, dyes, fillers, optical brighteners, germicides, non-builder alkalinity sources, enzymes, enzyme-stabilizing agents, and perfumes.
Preferred cobuilders for use herein are disclosed in U.S. Patent 4,019,998, Benson et al,. issued April 26, 1977 (particularly from Column 11, line 40 to Column 13, line 5), incorporated herein by reference. Particularly preferred are the aluminosilicates, carbonates and nitrilotriacetates, and mixtures thereof.
.The following non-limiting examples illustrate the detergent compositions of the present invention.
All percentages, parts, and ratios used herein are by weight unless otherwise specified.

EXAMPLE I

The following composition, intended for usage at a level of 1t cups (129 g) in a normal capacity, top-loading washing machine, was prepared by admixing the carbonate and polyethylene glycol to base granules formed by spray-drying an aqueous curtcher-mix slurry of the remaining components.
Other compositions of the present invention are obtained when the 24.4% phosphate in the above composition is adjusted to provide a weight ratio of pyrophosphate to tripolyphosphate of 10:1, 4:1 or 2:1.
Other compositions of the present invention are obtained when in the above compositions the pyrophosphate and sulfate levels are each reduced by 5% and replaced with 10% of either hydrated sodium aluminosilicate Zeolite A (avg. dia. 3 microns) or sodium nitrilotriacetate.

EXAMPLE I

The following composition, intended for usage at a level of ½ cup (51.9 g) in a normal capacity, top-loading washing machine, is prepared by spray-drying an aqueous crutcher-mix slurry of the components.
The dispersibility of the above granular composition can be improved by intimately mixing about 1% by weight of sodium polyacrylate of m.w. 2000 with the anionic surfactant paste prior to adding the balance of the components to- the crutcher, as described in pending U.S. Patent Application Serial No. 321,516, Barford, filed November 16, 1981.

EXAMPLE III

The following composition is prepared by first intimately mixing the 2000 m.w. polyacrylic acid with the anionic surfactant paste, and then spray-drying an aqueous crutcher-mix slurry of the components.
The base granules obtained are then admixed, at a level of 52.1 parts, with 41.3 parts of tetrasodium pyrophosphate,. 5.2 parts of sodium carbonate, 0.6 parts of polyethylene glycol 6000, and minors to provide a finished granular detergent intended for usage at a level of ½ cup (51.9g) in a normal capacity, top-loading washing machine.

Claims

1. A granular detergent composition characterised by:

(a) from 5% to 50% by weight of an organic surfactant selected from anionic, nonionic, zwitterionic, ampholytic and cationic surfactants, and mixtures thereof;

(b) from 5% to 80% by weight of an alkali metal pyrophosphate builder;

(c) an alkali metal tripolyphosphate builder present at a level such that the weight ratio of pyrophosphate to tripolyphosphate is from 50:1 to 1:1; and

(d) from 0.5% to 3% by weight of an alkali metal silicate having a molar ratio of SiO₂ to alkali metal oxide of from 1.0 to 3.2;

said composition prepared by drying an aqueous slurry comprising the above components, and wherein said composition is substantially free of polyacrylate polymers having a weight average molecular weight of from 10,000 to 200,000, and the amount of orthophosphate is limited such that the weight ratio of pyrophosphate to orthophosphate is at least 5:1.

2. A composition according to Claim 1 characterised in that the organic surfactant comprises an anionic surfactant selected from alkali metal salts of C_11-13 alkylbenzene sulfonates, C_14-18 alkyl sulfates, C_14-18 alkyl polyethoxy sulfates containing from 1 to 4 moles of ethylene oxide, and mixtures thereof.

3. A composition according to Claim 1 or 2 characterised in that the weight ratio of pyrophosphate to tripolyphosphate is from 20:1 to 2:1.

4. A composition according to Claim 3 characterised in that the weight ratio of pyrophosphate to tripolyphosphate is from 10:1 to 4:1.

5. A composition according to any of Claims 1 to 4 characterised in that the silicate has a molar ratio of from 1.6 to 2.4.

6. A composition according to any of Claims 1 to 5 characterised by from 10% to 30% by weight of organic surfactant, from 15% to 60% by weight of pyrophosphate builder, the weight ratio of pyrophosphate to tripolyphosphate being from 10:1 to 4:1, and from 1.5% to 2% by weight of silicate having a molar ratio of from 1.6 to 2.4.

7. A composition according to any of Claims 1 to 6 characterised in that substantially all of the alkali metal cations are sodium.

8. A composition according to any of Claims 1 to 7 characterised by spray-drying an aqueous slurry of the components.