US3494868A - Dishwashing composition and method of using same - Google Patents

Description

United States atent U.S. Cl. 25299 11 Claims ABSTRACT OF THE DISCLOSURE This invention relates to water-soluble alkaline. detergent composition which is useful for washing dishes, The composition comprises alkali metal phosphate as an inorganic detergent, alkali metal silicate as a corrosioninhibiting agent and boric acid and/or boric acid anhydride as an overglaze protector on dishes and the like. Boric acid anhydride, when employed, is particularly effective in inhibiting caking of the detergent composition.

This application is in part a continuation of Ser. No. 527,500 filed on Feb. 15, 1966 and 595,356 filed on Nov. 18, 1966 both now abandoned.

This invention relates to alkaline water-soluble dishwashing, glass-washing and silverware-washing compositions and to methods of washing with such compositions which are particularly useful in automatic dishwashing machines.

In accordance with the present invention, a water-soluble alkaline detergent composition for automatic dishwashing comprises an alkali metal phosphate as an inorganic detergent, an alkali metal silicate as a corrosioninhibiting agent and a material selected from the group consistinug of boric acid, boric acid anhydride and mixtures of same in a small but efficient amount to act as an overglaze protector on dishes.

The inclusion of boric acid or boric acid anhydride in the instant dishwashing compositions results in a formulation which, even though highly alkaline, provides a relatively corrosion-free environment together with the fortunate additional characteristic of the substantial elimination of the tendency of such compositions to cause fading of designs and patterns on china. Boric acid and boric acid anhydride are particularly desirable in this connection in that the instant composition is substantially completely water soluble leaving no residue or deposit either on the detergent dispenser or the china and like items in the automatic dishwashing machines in which these compositions are employed. Further, boric acid anhydride is also particularly desirable because its presence tends to markedly inhibit and prevent caking of the detergent composition during storage in a container, While the proportion of the boric acid or boric acid anhydride in a detergent formulation may be varied, a desirable range is from a small but perceptible quantity suflicient to diminish substantially fading of designs and patterns on china to about 20% by weight of the total formulation; a preferred range being from approximately by weight thereof.

The boric acid and boric acid anhydride may be used singly, in mixture with one another or in mixture with other boron-containing compounds, preferably dehydrated borates, such as anhydrous sodium tetraborate, Undoubtedly, the utilization of boric acid (H BO or boric acid anhydride (B 0 in other dishwashing formulations will ice be found desirable and the present inventive concept should be considered in its widest aspects.

Typically, the compositions of the present invention are composed of (-a) at least one detergent builder salt in a major amount comprising an alkali metal phosphate, wherein the ratio of Me O to P 0 is from 1 to 3:1, Me being sodium or potassium, including pentasodium tripolyphosphate, tetrasodium pyrophosphate and tetrapotassium pyrophosphate, trisodium orthophosphate, tripotassium orthophosphate and sodium hexametaphosphate; (b) at least one anhydrous solid, water-soluble alkali metal silicate wherein the ratio of SiO to Me O is from about 0.511 to 3.22:1, Me being sodium or potassium, and (c) boric acid or boric acid anhydride, preferably boric acid anhydride.

The detergent builder salt generally comprises from about 40 to about 90% by weight of the final composition and the silicate material generally comprises from about 5 to about 25% by weight of the final composition. Preferably the phosphate material comprises from about to about by weight of the final composition and preferably the silicate material comprises from about 18 to about 22% by weight of the final composition.

The phosphate detergent builder salt when hydratable may be employed in hydrated form, such as pentasodium tripolyphosphate hexahydrate, tetrasodium pyrophosphate decahydrate, tetrapotassium pyrophosphate trihydrate and trisodium orthophosphate dodecahydrate. In order to inhibit the tendency of the detergent composition to cake, it may be desirable to control the amount of moisture present so that little if any excess moisture is present which is not employed in the hydration of the phosphate. The most highly preferred detergent builder salt is pentasodium tripolyphosphate hexahydrate. This salt is substantially stable at temperature as high as 60 C.

The preferred detergent builder salt, pentasodium tripolyphosphate hexahydrate, is particularly effective in detergent composition also including borac acid when the hydrate contains but a small amount of extra water so that it releases no more than 1% of its weight of moisture at 60 C. When the extra water content is such that more than 1% of moisture by weight of the builder salt is released at 60 C., desirable overglaze protection is still obtained, but the composition may have a tendency to cake. This tendency may be controlled when pentasodium tripolyphosphate hexahydrate and boric acid are employed by using a hexahydrate which initially contains extra water in such amount that no more than 1% of moisture is released at 60 C. and by protecting the composition from contact with moisture in an appropriate container during its shelf life.

In accordance with certain preferred aspects of this invention, boric acid anhydride is employed rather than boric acid. In this situation, even pentasodium tripolyphosphate hexahydrate that releases more than 1% of moisture by weight of the phosphate at 60 C. may be employed and the desired overglaze protection attainedwhile the composition remains substantially free of caking.

The preferred silicate corrosion-inhibiting agent is sodium metasilicate where the ratio of SiO to Na O is 1:1. The silicate is preferably maintained in anhydrous condition.

Additional optional, but desirable constituents include an anti-spotting agent and a low foaming organic wetting agent or detergent. I

As a suitable anti-spotting agent, it is preferred to use a dry water-soluble compound which, on contact with Water, liberates hypochlorite chlorine, that is, those watersoluble dry solid materials which generate hypochlorite ions on contact with, or dissolution in water. Examples thereof are the dry, particulate heterocyclic N-chlor imides such as trichlorocyanuric acid, dichlo-rocyanuric acid, and salts of dichlorocyanuric acid such as sodium dichlorocyanurate and potassium dichlorocyanurate. Other imides may also be used such as N-chlorosuccinimide, N-chloromalonimide, N-chlorophthalimide, and N-chloronaphthalimide. Additional suitable imides are the hydantoins such as 1,3-di-chloro-5,S-dimethylhydantoin; N- monochloro-S,S-dirnethylhydantoin; methylene bis (N- chloro-S,S-dimethylhydantoin; 1,3-dichloro 5 methyl-5- isobutyl hydantoin, 1,3-dichloro-5-methyl-5-ethylhydantoin, 1,3-dichloro 5,5 diisobutylhydantoin, 1,3-dichlo-ro- S-methyl-S-n-amylhydantoin, and the like. Other useful hypochlorite-liberating agents are trichloromelamine and dry, particulate, watersoluble anhydrous inorganic salts such as lithium hypochlorite and calcium hypochlorite.

These chlorine-liberating anti-spotting agents are employed in small but perceptible amount, such as on the order of about 0.5 to about 5% by weight of the final composition, preferably about 0.5 to 3% and more preferably about 1.5 to 2%.

As organic wetting agent or detergent it is preferred to use the low-foaming ethylene oxide condensate type of nonionic detergents. Examples thereof are the reaction products of benzyl chloride and ethoxylated alkyl phenol having the formula R-Q-(O omomgornoQ where R is an alkyl chain having from 6 to 12 carbon atoms and X is a whole number of 12 to 20 carbon atoms, polyether esters of the formula where x is an integer from 4 to 20 and R is a lower alkyl group of not over four carbon atoms, for example, a compound of the formula (ClC H CHCO CH CH O CH and polyalkylene oxide condensates of an alkyl phenol, such as the polyglycol ethers of alkyl phenols having an alkyl group of at least about 6 and usually about 8 to 20 carbon atoms and an ethylene oxide ratio (number of ethenoxy groups per mole of condensate) of about 7.5, 8.5, 11.5, 20.5, 30, and the like. The alkyl substituent on the aromatic nucleus may be di-isobutylene, diamyl, polymerized propylene, isooctyl, nonyl, dimerized C C olefin, and the like. Among other condensates With phenols is the alkylated O-naphthol condensed with 8 moles of ethylene oxide, the alkyl group having 6 to 8 carbon atoms.

Further suitable detergents are polyoxyalkene esters of organic acids, such as the higher fatty acids, rosin acids, tall oil, or acids from the oxidation of petroleum, and the like. The polyglycol esters will usually contain from about 8 to about 30 moles of ethylene oxide or its equivalent and about 8 to 22 carbon atoms in the acyl group. Suitable products are refined tall oil condensed with 16 or 20 ethylene oxide groups, or similar polyglycol esters of lauric, stearic, oleic and like acids.

Additional suitable non-ionic detergents are the polyalkylene oxide condensates with higher fatty acid amides, such as the higher fatty acid primary amides and higher fatty acid monoand di-ethanol-amides. Suitable agents are coconut fatty acid amide condensed with about to 30 moles of ethylene oxide. The fatty acyl group will similarly have about 8 to 22 carbon atoms, and usually about 10 to 18 carbon atoms in each product. The corresponding sulphonamides may also be used if desired.

Other suitable polyether non-ionic detergents are the polyalkylene oxide ethers of higher aliphatic alcohols.

Suitable alcohols are those having a hydrophobic character, and preferably 8 to 22 carbon atoms. Examples thereof are iso-octyl, nonyl, decyl, dodecyl, tridecyl, tetradecyl, hexadecyl, octadecyl and oleyl alcohols which may be condensed with an appropriate amount of ethylene oxide, such as at least about 6, and preferably about 10-30 moles. A typical product is tridecyl alcohol, produced by the Oxo process, condensed with about 12, 15 or 20 moles of ethylene oxide. The corresponding higher alkyl mercaptans or thioalcohols condensed with ethylene oxide are also suitable for use in compositions of the present invent1on.

The Water-soluble polyoxyethylene condensates with polyoxypropylene polymers may likewise be employed in compositions of the present invention. The polyoxypropylone polymer, which is prepared by condensing propylene oxide with an organic compound containing at least one reactive hydrogen, represents the hydrophobic portion of the molecule, exhibiting sufficient water insolubility per so at a molecular weight of at least about 900, such as about 900 to 2400, and preferably about 1200 to 1800. The increasing addition or condensation of ethylene oxide on a given water insoluble polyoxypropylene polymer tends to increase its water solubility and raise the melting point such that the products may be Water soluble, and normally liquid, pasty or solid in physical form. The quantity of ethylene oxide varies with the molecular weight of the hydrophobic unit but will usually be at least about 20% and preferably at least about 40% by weight of the product. With an ethylene oxide content of about 40 up to 50%, there are usually obtained normally liquid products, above 50% soft wax-like products, and from about 90% normally solid products may be obtained which can be prepared in flake form if desired. These condensates may be designated by the following structures:

Y is the residue of an organic compound which contained at active hydrogen atoms,

n is an integer,

x is an integer, the values of n and x being such that the molecular weight of the compound, exclusive of E, is at least 900, as determined by hydroxy number,

E is a polyoxyethylene chain and constitutes 2090%,

by weight of the compound, and

H is hydrogen.

It is preferred to use products of the type just described having a total molecular Weight within the range 2000 to 10,000, and preferably about 4000 to 8000. A suitable material is a condensate having a typical average molecular weight of about 7500, the hydrophobic polypropylene glycol being condensed with sufficient ethylene oxide until a normally solid water-soluble product is obtained which has an ethyene oxide content of about and a melting point usually of about 5154 C. Another material is a liquid condensate having an ethylene oxide content of 40-5 0% and a molecular weight of about 4500.

Examples of other suitable wetting agents include low foaming anionic materials such as dodecyl hydrogen phosphate, methyl naphthalene sulfonate, sodium Z-acetamidohexadecane-l-sulfonate, and mixtures thereof. Mixtures of the foregoing wetting agents may also be employed, and, if desired, foam-reducing additive may be added as appropriate to minimize undesirable foaming tendencies of these wetting agents under conditions of use.

The organic wetting agent may be employed in the instant formulations in amounts up to 3% by weight of the final composition, typically up to about 2% by weight, and preferably about 0.1 to 1% by weight thereof. Preferably the Wetting agent used would be characterized by a foam height of less than about 50 mm. in the Ross- Miles pour foam test described by Ross and Miles in Oil and Soap, May 1941, pages 99 to 102.

Sodium sulfate suitably may be present in the instant compositions in an amount up to about by weight thereof. As a further ingredient in the formulation a suitable perfume may be included to give the formulation a pleasant odor. Since most non-ionic detergents have some odor, the choice thereof should take into consideration the odor of the non-ionic detergent so that it does not unduly conflict with the perfume.

A quantity of a coloring material may also be considered as yet a further ingredient. For instance, acceptable coloring materials are ultramarine blue and heliogen green, a phthalocyanine green pigment. Naturally, the quantities employed are quite small. Other suitable additives may include small quantities, e.g., 02%, of other types of glaze attack inhibitors such as compatible proportions of sodium berylliate, aluminum acetate, sodium aluminate, and the like.

The solid materials utilized desirably should be granular preferably having a mesh size of approximately the same size (and within the range of about 20 to 200 mesh, that is, about 0.074 to 0.84 mm.) in order to prevent stratification. In formulating the detergent compositions, it is important that all the ingredients be kept dry as possible prior to mixing. The ingredients should preferably be of anhydrous grade taken from sealed containers or, in the case of the phosphate builder salt, hydrated but protected from contact with additional moisture. When anhydrous phosphate is initially employed, it should preferably be stoichiometrically hydrated prior to contact with the other ingredients. The ingredients should be charged directly to a mixer. It has been found efiicacious to add the anti-spotting agent to a sub-mixture of a portion of the sodium tripolyphosphate hexahydrate and all of the sodium sulfate when the latter is included. Since the quantity of the anti-spotting agent is relatively small, it is difficult to insure a complete distribution when added directly to the mixture of builder salts and boric acid unless a submixture is employed.

The inventive concept can best be seen in the following examples. (Unless otherwise indicated, all parts and percentages herein are by weight.)

6 mist to the Preblend I and the resulting mass is agitated for approximately 5 minutes. The solid materials are all within the particle size range of about 20 to 200 mesh (U.S. Sieve series), that is, about 0.074 to 0.84 mm.

The ingredients of Preblend III are suitably premixed and then are added to the mixture comprising Preblend I and Preblend (II. The mixture is agitated to insure good distribution of all of the components.

The density of the resultant is about 0.87:0.03 g. cc. and the available chlorine con-tent thereof is 0.8:0.2%. The pH of the product in water is about 11 (1% solution).

Anhydrous sodium tripolyphosphate may be employed in lieu of the hexahydrate of this example.

EXAMPLE II Preblend I: Parts by weight Sodium tripolyphosphate hexahydrate 60.45 Anhydrous sodium metasilicate (lNa O:1SiO 20.00 Boric acid 10.00 Preblend II Non-ionic detergent of Example I 1.5 Perfume liquid 0.02 Heliogen green pigment 0.005 Water 0.025 Preblend III Potassium dichloroisocyanurate 1.60 Sodium tripolyphosphate hexahydrate 2.40 Sodium sulfate 4.00

In formulating, the ingredients of Preblend I are mixed for approximately 10 minutes in a twin shell blender as in connection with Example I. Regarding Preblend II, the heliogen green is dispersed in the Water and is then mixed with the non-ionic detergent and perfume. The resultant is charged into the mixer as a mist. To insure even distribution the mixing is continued for approximately 5 minutes.

The Preblend III is handled as in Example I and is added to the mixture as before.

The product has the general characteristics as in Example I.

The following additional examples to show the range of ingredients in percentage by weight:

Example III V VI VII VII IX Sodium tripolyphosphate hexahydrate 62.68 0 69.0 55.0 64.5 62.5 Sodium metasilicate (anhydrous) 0 19.0 21.0 20.0 20.00

Nonionic detergent 13* Nonionic Wetting agent of Example I Methyl naphthalene sulfonate. Boric acid Potassium dichloroisocyanurate. Sodium dichloroisocyanurate--. Perfume Sodium sulfate Ultramarine blue The nonionie detergent is the product obtained by the condensation of one mole of a mixture of essentially straight chain, primary, fatty alcohols in the (7 -0 range with a mixture of about 5 moles of ethylene oxide and about seven moles of proyylene oxide.

Sodium tripolyphosphate hexahydrate 2.40 Sodium sulfate 4.00 Ultramarine blue 0.20

The non-ionic detergent is the product obtained by the condensation of about three moles of propylene oxide with the condensation product of one mole of a mixture of essentially straight chain, primary, fatty alcohols in the C1o-C1s range with about six moles of ethylene oxide.

In formulating, the ingredients of Preblend I are mixed for approximately 10 minutes in a twin shell blender.

Then the non-ionic detergent and perfume are added as a Example X XI XII XIII Sodium tripolyphosphate hexahydrate 64.45 42. 50 42. 50 Tetrasodium pyrophosphate decahydrate 55. 45 21.95 21.95 Sodium silicate (anhydrous) 20.00 13. 50 18.00 18.00 Potassium silicate (anhydrous) 8. 00 Nonionic detergent of Example II 1. 50 3 00 2 00 2.00 Boric acid anhydride 5. 3

Potassium dichloroisocyanurate Perimne Sodium sulfate. Ultramarine blue While the detergent composition of the present invention finds most efficacious utilization in connection with the washing of the dishes and the like in automatic dishwashers, naturally, the detergent may be utilized in other fashions as desired. Usually, however, the best mode of use will be in connection with automatic dishwashers which have the ability of dispensing the detergent of the present invention in one or more separate wash cycles. Accordingly, the detergent composition of the present invention is added to the two receptacles, if such are present, in an automatic dishwasher. When the dishwasher is set into operation, after the dishes have been suitably positioned there in, the automatic devices of the dishwasher permit the ad dition of sufficient water to produce a concentration of the detergent composition of approximately 0.3% by weight. The operation of the dishwasher results in treating, that is, washing of the dishes with the aqueous solution of the detergent composition. Usually, the sequence of operation in utilizing an automatic dishwasher results in one or more rinsing steps following the one or more washing cycles. In utilizing the detergent composition of the present invention it will be noted that even after use in a considerable number of washings there will be little or no attack on the overglaze of china or little or no tarnishing of silver or silver plate as a result of the use of the detergent composition.

1 claim:

1. A water-soluble alkaline detergent composition consisting essentially of from about 40 to about 90% by weight based on the final composition of at least one alkali metal phosphate wherein the ratio of Me O to P is 1:1 to 3:1, Me being selected from the class consisting of sodium and potassium, from about 5 to about 25% by weight based on the final composition of at least one solid, water soluble alkali metal silicate wherein the ratio of SiO:; to Me O is from about 0.5:1 to 3.22: 1, Me being selected from the class consisting of sodium and potassium, from 0 to 5% by weight based on the final composition of an alkali metal sulfate, from a small but perceptible amount to about 20% by weight based on the final composition of a material selected from the group consisting of boric acid, boric acid anhydride and mixtures of same from a small but perceptible amount to about 5% by weight based on the final composition of an anti-spotting agent selected from the group consisting of sodium dichlocate is present in amount of from about 18 to about 22% i by weight based on the final composition, and said material selected from the group consisting of boric acid and boric acid anhydride is present in amount of from about 5 to about by weight based on the final composition and said anti-spotting agent is present in amount of from about 1.5 to about 2% by weight based on the final composition.

4. A water-soluble alkaline detergent composition as claimed in claim 3 wherein said material is boric acid anhydride.

5. A water-soluble alkaline detergent composition as claimed in claim 4 wherein said material is boric acid.

6. A method for treating dishes and the like to remove foreign bodies from the surfaces thereof without modifying the substrate, comprising treating said dishes and the like with a dilute aqueous solution of a water-soluble alkaline detergent composition consisting essentially of builder all) salts in major amount comprising about 40 to about by weight based on the final composition of at least one alkali metal phosphate wherein the ratio of Na O to P 0 is from 1 to 3:1, Me being selected from the class consisting of sodium and potassium, from about 5 to 25% by weight based on the final composition of at least one solid, water-soluble alkali metal silicate wherein the ratio of SiO to Me O is about 0.5 to 3.22:1, Me being selected from the class consisting of sodium and potassium, from 0 to 5% by weight based on the final composition of an alkali metal sulfate, from a small but perceptible amount to about 20% by weight based on the final composition of a material selected from the group consisting of boric acid, boric acid anhydride and mixtures of same, from a small but perceptible amount to about 5% by Weight based on the final composition of an anti-spotting agent selected from the group consisting of sodium dichloroisocyanurate and potassium dichloroisocyanurate and mixtures thereof, and from 0 to 3% by weight based on the final composition of a low-foaming nonionic wetting agent and thereafter rinsing said detergent composition from said dishes and the like.

7. The method of claim 6 wherein the detergent composition contains as the alkali metal phosphate, sodium tripolyphosphate hexahydrate and contains as alkali metal silicate, sodium metasilicate.

8. The method of claim 6 wherein said alkali metal sulfate is sodium tripolyphosphate hexahydrate and is present in amounts ranging from about 60 to about 65% by weight based on the final composition, said silicate is sodium metasilicate and is present in amounts ranging from about 18 to about 22% by weight based on the final composition and said material selected from the group consisting of boric acid, boric acid anhydride and mixtures of same are present in amounts ranging from about 5 to about 10% by weight based on the final composition, said anti-spotting agent is potassium dichloroisocyanurate and is present in amounts ranging from about 1.5 to 2% by weight based on the final composition.

9. A method for treating dishes and the like to remove foreign bodies from the surfaces thereof without modifying the substrate claimed in claim 8 wherein said material is boric acid anhydride.

10. A method for treating dishes and the like to remove foreign bodies from the surfaces thereof without modifying the substrate claimed in claim 8 where said material is boric acid.

11. The detergent composition of claim 1 wherein said material comprises a mixture of boric acid and boric acid anhydride.

References Cited UNITED STATES PATENTS 3,128,250 4/1964 Lintner 25299 3,211,659 10/1965 Oirar 252136 3,255,117 6/1966 Knapp et a1 25299 3,325,411 6/1967 Stepanek 25299 3,350,318 10/1967 Green 252 3,352,785 11/1967 Corliss et a1 25299 MAYER WEINBLATT, Primary Examiner US. Cl. X.R. 25297, 136, 187