US3382178A - Stable alkaline detergents - Google Patents

Description

United States Patent 3,382,178 STABLE ALKALINE DETERGENTS Kenneth J. Lissant and Frederick J. Ludwig, Sr., St. Louis, Mo., assignors to Petrolite Corporation, Wilmington, DeL, a corporation of Delaware No Drawing. Filed Feb. 1, 1965, Ser. No. 429,639 1 Ciaim. (Cl. 252135) ABSTRACT OF THE DISCLOSURE Stable alkaline detergent compositions for use in machine dishwashing, machine bottle washing and in general purpose heavy duty cleaners including inorganic alkali metal detergent salts selected from the group consisting of alkali metal carbonates, alkali metal borates, alkali metal polyphospates, alkali metal hydroxides, alkali metal silicates, and mixtures thereof, in combination with (1) defoaming nonionic surfactants such as oxyalkylated compounds of the general formuia Z[(OA),,OH] where in Z is the oxyalkylatable material, A is the radical derived from the alkylene oxide, which can be, for example, ethylene, propylene, butylene oxide, etc., and the like, n is a number determined by the moles of alkylene oxide reacted, for example to 2000 or more and z is a whole number determined by the number of reactive oxyalkylatable groups, and (2) a small but effective amount of antioxidant etfective to reduce, inhibit and/or prevent the degradation of the nonionic surfactant thereby rendering the nonionic surfactant stable in the stable alkaline detergents.

This application is copending with application Ser. No. 429,620, filed on Feb. 1, 1965, now US. Patent No. 3,356,612 and this application and said copending application have a common assignee.

This invention relates to stable detergents, including stable detergent compositions for use in machines dishwashing, machine bottle washing and in general purpose heavy duty cleaners.

Machine dishwas'hing is used in connection with practically all commercial and institutional dining facilities as Well as in a rapidly increasing proportion of private homes. In commercial machines, the dishes to be washed are introduced into a zone where detergent solution is sprayed over them, the detergent solution :being recycled and used repeatedly and fortified and replenished intermittently. In home machines the detergent is used for only one load of dishes and is then discarded although it too is recirculated during the washing operation. Hence in both types of machines, food soil concentrations in the wash solution of 0.05 to 0.1% or higher are considered to be moderate under average conditions.

It has been the practice in formulating machine dishwashing detergents to use in the main various combinations of inorganic sodium and potassium salts, such as polyphosphates, silicates, carbonates and basic materials such as sodium and potassium hydroxides. It has not been possible to use effective amounts of well-known organic detergents such as the alkyl aryl sulfonates, alkyl sulfonates, alkanol amides or alkyl aryl polyethers in spraytype mechanical dishwashing detergents because of the foam these detergents develop during the washing operation. This foam causes over-flow and loss of the wash solution, impairs the mechanical operation of the machine, and lowers the pressure at which the washing fluid is impelled against the utensils to be cleaned. The in0rganic materials themselves do not foam and, at low concentrations of food soil (less than 0.01%), perform satisfactorily in mechanical dishwashers. However, with increases in food soil concentration to greater than about 0.03%, foaming becomes a serious problem even with the use of purely inorganic detergent system. This is because the inorganic detergent systems, being alkaline, can cause some saponification of fatty food soils. This, plus the natural foaming properties of protein food soils, tends to produce foam in the wash tank.

Recently, certain low foaming, organic, non-ionic detergents have been made available commercially which can be incorporated in small amounts with inorganic materials in mechanical dishwashing formulations without seriously increasing their foaming tendency. These materials add somewhat to the detergency efficiency of the compound formulation. In addition, compounds of this type have been found to have pronounced effect of inhibiting foam where heavy food soil loads are present, or in maintaining internal Wash pressure at a high level under these conditions.

Wash pressure is defined herein as the pressure registercd on a manometer or pressure gauge by a Pitot tube set at the outlet of the wash nozzle. The force of the wash spray against a dish surface is directly proportional to this wash pressure. Since it has been shown that the wash action of the wash spray contributes most to gross soil removal, maintenance of the original wash pressure built into the machine is very important.

Excessive foaming in machine dishwas-hing has long been a recognized problem; and, although billowing foam is an obvious indication of trouble, a real wash pressure problem may exist even without this obvious symptom. For example, an aerated wash solution, though not so easily detected, may be as serious a problem from the standpoint of washing eificiency as billowing foam. An aerated wash solution, as used herein, is defined as a liquid with many small air occlusions or bubbles dispersed in it as contrasted with foam which, as used herein, is defined as a colloidal dispersion of air in liquid floating on top of the wash solution.

Conventional machine dishwashing detergent systems originally were dry, inorganic systems and consisted entirely of mixtures of alkaline salts. The detergent system is required to perform three essential functions: (1) soften the water so that the detersive action can take place more effectively; (2) remove the soil from the dishes thoroughly, completely and rapidly; and (3) leave the dish surface in a state where the water drains in a continuous film without breaking into little hanging drops or streams. Many of the alkaline salts act as both water softeners and soil removers but will be discussed on the basis of their primary function.

Sodium carbonate, although it is among the least effective water-softening agents, together with its sesquicarbonate, is almost universally used as a component in dishwashing compounds, because of its low cost. The detergent compositions of this invention can contain from 099% by weight sodium or potassium carbonate.

The best and most efficient water-softening ingredients are the condensed polyphosphates, including the tripolyphosphates and the pyrophosphates. The detergent cornpositions of this invention can contain from O70% by weight sodium or potassium polyphosphates. Othersequestering agents, including organic materials such as ethylenediamine-tetracetic acid and sodium gluconate, can also be employed in compositions of this invention, particularly in formulations for dairy use containing high percentages of caustic.

Polyphosphates have been shown to promote corrosion of certain metal parts of dishwashing machines but this corrosive effect can be overcome by including a relatively large proportion of a silicate in the composition. In this connection, metasilicate is important, not only from the standpoint of the machine itself, but also from the standpoint of the utensils washed. For instance, regardless of whether polyphosphate is present in a solution or not, highly alkaline dishwashing detergents containing no silicates can attack, etch, and darken aluminum utensils. Some of these formulations also have a destructive action on the over-the-glaze dish patterns. Suitable proportions of silicates in the formulation help overcome these difficulties.

The soil-removing ingredients commonly employed in dishwashing compounds include borates and carbonates, which are relatively ineffective, and orthophosphates and metasilicates, both of which are highly effective. The detergent compositions of this invention can include 70% by weight of trisodium or tripotassium phosphate and 050% by weight of sodium or potassium metasilicate.

More recently small amounts of synthetic organic surfactants or Wetting agents have been incorporated into machine dishwashing formulations to promote smooth drainage drying, i.e., to prevent water break. Some formulations include from 1% to 5% or more of a low foaming, polyethenoxy type nonionic surfactant. The detergent compositions of this invention can include 050% by weight of such synthetic, organic, low foaming polyethenoxy type nonionic surfactants.

Conventional machine dishwashing compositions employed for glass and bottle washing normally contain caustic soda as the major cleaning ingredient. Alkalies tend to attack glass surfaces but this can be inhibited by zincates, beryllates, or aluminates. As stated above, sodium gluconate and ethylenediaminetetracetic acid can be used as sequestering agents for high caustic content solutions. The detergent compositions of this invention can include 43-99% sodium or potassium hydroxide.

Hence the conventional detergent systems into which the polyoxyalkylene glycol mixture is incorporated contain as the principal detersive agent widely varying proportions of sodium or potassium polyphosphates, i.e., 0.70%, sodium or potassium silicates, i.e., 050%, sodium or potassium carbonates, i.e., 2-99%, sodium or potassium hydroxides, i.e., 0-100% and trisodium or tripotassium phosphates, i.e., O-70%. The amount of the polyoxyalkylene glycol mixture ordinarily constitutes about 0.5 to by weight of the final deter-gent composition.

In addition to using highly alkaline compositions containing sodium hydroxide in bottle washing compositions, similar types of alkaline compositions also are employed in the cleaning of stainless steel equipment, utensils and piping which are used in all types of food processing industries (such as milk products, bakery products and various protene concentrates) and related industries, for example where materials such as glues are used. The washing operations usually involves spraying, vigorous agitation, or vigorous recirculation or combinations thereof; and as a result considerable foaming develops. Controlling foam in these applications is important toward achieving thorough cleaning.

The duration of storage for dishwashing compositions, bottle washing compositions and metal cleaning compositions, before they are used, may be three to six months or even longer. Therefore, the defoaming surfactants must be protected during this time against degradation by the alkaline constituents in the composition to assure the consumer that an adequate amount of defoaming agent is present at the time of washing the equipment, utensils and piping in order for the foam to be controlled effectively.

This problem of formulating machine dishwashing compositions, bottle washing compositions and metal-washing compositions and the like is complicated by the fact that nonionics are degraded by alkaline constituents of the formulations.

Stated another way, oxyalkylated compounds of the nonionic type are unstable in the presence of alkaline materials. When nonionics of this type are employed in alkaline compositions, they tend to degrade upon storage. Thus, alkaline compositions do not have sufficient shelf-life to yield completely satisfactory products. For example, when certain defoaming nonionic detergents are employed and formulated in alkaline compositions, they tend to degrade and result in losing their ability to defoam; and as a result, the alkaline composition becomes unsatisfactory because the amount of defoarning surfactant remaining is unable to control the natural foaming tendency which develops when proteinaccous soil is in contact with the alkaline constituents. This increase in foaming is extremely detrimental to machine operations. For example, in dishwashing machines foam prevents pumps and sprays from operating properly and heavy duty metal cleaners from cleaning thoroughly.

We have now discovered that, when nonionics are employed in conjunction with an antioxidant, the degradation of nonionics in such alkaline compositions can be reduced, inhibited and/ or prevented. Stated another way, the nonionics are rendered much more stable in alkaline systems when in contact with an antioxidant. For example during storage degradation of the nonionic is greatly minimized by incorporating an antioxidant in the system. This invention is applicable to all formulations in which alkaline materials are employed with nonionics.

A small but effective amount of antioxidant is employed in this invention, i.e., effective in reducing, inhibiting and/or preventing the degradation of nonionics.

Since a wide variety of nonionics and antioxidants and other components can be employed in the detergent system, the effective amount of antioxidant will vary widely. In practice we employ one or more antioxidants in at least about 0.01% by weight such as from about 0.1 to 10.0%, for example from about 0.3 to 5.0%, but preferably from about 0.5 to 2.0% based on weight of the nonionic surfactant in the formulation.

In general, the nonionic employed in the formulation is less than about 5% by weight of the total formulation, but more can be employed if desired.

A wide variety of nonionics can be employed in this invention. In general, the nonionics employed are oxyalkylatcd compounds of the general formula wherein Z is the oxyalkylatable material, A is the radical derived from the alkylene oxide which can be, for example, ethylene, propylene, butylene oxide, etc, and the like, 22 is a number determined by the moles of alkylene oxide reacted, for example 10 to 2000 or more and z is a whole number determined by the number of reactive oxyalkylatable groups. Where only one group is oxyalkylatable as in the case of a substituted or unsubstituted monofunctional phenol, a straight chain biodegradable alcohol, or a branched-chain alcohol, then z=1. It is known that normal alcohols are biodegradablesuch as, those obtained by saponification of natural waxes such as sperm oil, those obtained by reduction of fatty acids derived from coconut oil, palm kernel oil, or tallow and those obtained from petroleum sources, such as for example, the mixtures of C through C straigh -chain primary alcohols now commercially available from Con tinental Oil Co. Where Z is water, or a glycol, z=2. Where Z is glycerol, z=3, etc.

As is well known, alkylene oxides can be reacted with various oxyalkylatable materials (i.e. materials which contain hydrogen atoms capable of reacting with a 1,2- alkylene oxide) to form polyalkylene oxide derivatives thereof. Thus, where an oxyalkylatable material of the formula ZH is reacted with an alkylene oxide such as ethylene oxide, there is obtained a compound of the formula where n is a number determined by the moles of alkylene oxide reacted and z is a number determined by the compounds oxyalkylatable hydrogens.

Many polyalkylene oxide block polymers have been prepared containing definite homogeneous block units or segments of ethylene oxide, propylene oxide, butylene oxide, etc., such as disclosed in U.S.P. 2,674,619, 2,677, 700 and elsewhere.

Where ethylene oxide is reacted with water, a polymeric polyethylene glycol of the type is formed. Similarly, where propylene oxide is reacted with water, a polymeric polypropylene glycol of the type H(OPr) O(PrO) H is formed. When water is first reacted with ethylene oxide followed by reaction with propylene oxide, a polymer containing blocks of ethylene oxide units and blocks of propylene oxide are formed, H(OPr). (OEt) O(EtO) (PrO) I-I, or when added in the reverse order the following block polymer is formed:

Block polymers of this type can be formed by adding infinite numbers of block units, for example This block-wise or sequential addition could be continued infinitely. Since only two types of alkylene oxides are employed, these polymers are (ii-block polymers.

Where three or more different types of alkylene oxides are employed, ter-block polymers are formed as illustrated by sequentially adding ethylene oxide, propylene oxides, and butylene oxides to water to form:

These tor-block units may also be continued infinitely. Where, for example, other alkylene oxides are used in addition to ethylene, propylene, and butylene oxides, a higher type of block polymer is formed, such as when octylene oxide or styrene oxide are additionally reacted. It is to be noted the block units of these polymers within themselves are homogeneous units, i.e., each block is derived from a single alkylene oxide.

Polyalkylene oxides have also been prepared by reacting mixtures of alkylene oxide such as when a mixture of ethylene oxide and propylene oxide are reacted. When this is done, a random of hetero-polymer is obtained. Thus, for example, where a 50/50 molar mixture of EtO and PrO are reacted with an oxyalkylatable material, such as water, one obtains a polymer having no orderly arrangement of the alkylene oxide units since the distribution of EtO and P units in the molecule is random may be designated by Carbide & Carbon sells these mixed glycols under the Ucon trademark.

MO as employed herein refers to mixtures of ethylene oxide in conjunction with a hydrophobic alkylene oxide, i.e., an alkylene oxide having more than two carbon atoms. Thus, the hydrophobic alkylene oxides include propylene oxide, butylene oxide, amylene oxide, octylene oxide, styrene oxide, methylstyrene oxide, cyclohexene oxide, etc. However, in practice we prefer to employ ethylene oxide in conjunction with propylene and/ or butylene oxide.

The alkylene oxides employed herein are 1,2-alkylene oxides of the formula wherein R R R and R are selected from the group consisting of hydrogen, an aliphatic, cycloaliphatic, aryl, etc. group for example ethylene oxide, propylene oxide, butylene oxide, amylene oxide, octylene oxide, styrene oxide, methylstyrene oxide, cyclohexene oxide, (where R and R are joined to make a ring), etc.

Equivalents of alkylene oxides can also be employed, for example alkylene carbonates, i.e. ethylene carbonate, propylene carbonate, butylene carbonate, etc. In addition, alkylene oxides of the glycide, methyl glycide type can also be employed.

Since the products of this invention are preferably block polymers containing blocks or segments of alk lene oxide units which are added sequentially, the reaction is in essence a stepwise procedure. For the sake of simplicity of presentation, the invention will be illustrated by employing as a base oxyalkylatable compound ZI-I and by employing only ethylene, propylene, and butylene oxides with the understanding that other hydrophobe oxides can be used in place of propylene and butylene oxides such as amylene oxide, octylene oxide, styrene oxide, etc. These are shown in the following table.

The products formed are represented by means of a statistical formula and are often referred to as cogeneric mixtures. This is for the reason that if one selects any oxyalkylatable material and subjects it to oxyalkylation, particularly where the amount of oxide added is comparatively large, for example 30 units of EtO, it is well known that one does not obtain a single constituent such as RO(C H O) H. Instead one obtains a cogeneric mixture of closely related homologous compounds in which the formula may be shown as the following: RO(C H O),,H where X as far as the statistical average goes, is 30, but the individual members present insignificant amounts may vary from compounds where x has a value of 25 and perhaps less to a point where x may represent 35 or more (see Flory Chemical Reviews, vol. 30, No. 1, page 137). Thus, the formulae presented herein are statistical formulae.

TABLE 1 Step I zruno m )n 1z Z[(Buo),,H Z[(MO),,H],, Z[(Pro rxuo),,rr

Step 11 Reaction of the Step I product with one of the five oxides or mixtures employed in Step I, which oxide had not been reacted in the immediately preceding step. For example:

Step IV involves the oxyalkylation of the products of Step III. Step V involves the oxyalkylation of Step IV. Further oxyalxylations involve Steps VI-X or higher. This process can be continued ad infinitum.

Where Z is derived from ZH which is H O, 2:2. Where Z is derived from ZAH, Z is the moiety of an alcohol or a phenol and 2:1. Where Z is derived from a polyol such as glycerol, z 2. Examples of ZOH include the following:

(1) Oxyalkylatable monofunctional compounds such as alcohols of the C H OH series for example methanol, propanol, butanol, pentanol, hexanol, octanol, nonanol, decanol, undecanol, dodecanol, tridecanol, tetradecanol, pentadecanol, hexadecanol, heptadecanol, octadecanol, etc. (2) Corresponding unsaturated alcohols, for example oleyl, linoleyl alcohols, (3) phenolic compounds ineluding those of the general formula Where R is hydrogen or a substituted group for example those of the C H series, i.e. methyl, ethyl, propyl, butyl, etc., corresponding unsaturated radicals: phenyl, substituted phenyl, etc., and m is an integer for Examples 13, but preferably 1.

In addition condensed ring aromatic compounds can be employed, for example, naphthol, substituted naphthol, etc.

Polyols can also be employed as exemplified by the following:

Polyhydric alcohols Ethylene glycol Propylene glycol Diethylene glycol Trimethylene glycol 2,3-3utanediol l,4-r'iihydroxy-2-butene 1,12-dihydroxy octadecane 9 1,4-dihydroxy cyclohexane 2,2-dimethyl-1,3-propanediol 2-ethyl-2-butyl propanediol-1,3 Glycerol Eryth-ritol Sorbitol Mannitol Inositol Trimethylol propane Pentaerythritol Polyallyl alcohol Bis (4-hydroxycyclohexyl) dimethyl methane 1,4-dimethylol benzene 4,4'-dimethylol diphenyl Dimethylol xylenes Dimethylol naphthalenes, etc.

Beta hydroxyethyl ethers of glycerol, pentaerythritol,

" sorbitol, mannitol, etc.

Condensates of alkylene oxides such as ethylene oxide; propylene oxides; butylene oxide; isobutylene oxide; glycidol; glycid ethers, etc. with polyhydric alcohols such as the foregoing.

Polyhyd-ric phenols Hyd-roquinone Resorcinol Pyrogallol Bisphenol (predominantly 4,4'-dihydroxy diphenyl dimethyl methane) Dihydroxy diaryl sulfones Phenol-aldehyde resins (See US. Patent 2,499,365)

The molecular weight of the nonionics of this invention can vary widely from such as 500 to 100,000, or higher, for example a range of 1,000 to 25,000, preferably 1,500- 7,000 with an optimum of 2,0005,000. However, the specific preferred and optimum molecular weight will vary with each particular application.

The moles of alkylene oxide on each block unit can also vary widely, such as from 520() moles, or more, of alkylene oxide, for example, a range of 150 moles with an optimum of -60 moles per block unit. However, the range of the specific preferred block unit will vary with the specific surfactant molecule and with the system in which the surfactant is employed.

In general the nonionics which are most effective in the practice of this invention are those which contain more than one kind of alkylene oxide, either in random distribution, in block formation or both. Where the nonionic is a block polymer, it is preferred that the terminal group be derived from a hydrophobe alkylene oxide, i.e. one other than EtO, preferably PrO. If the terminal block is derived from ethylene oxide, then the block so derived preferably should contain less alkylene oxide molar units than the immediately preceding hydrophobe alkylene oxide block.

Preferably, the nonionics should be a low foaming surfactant. In uses where biodegradability is important, it is preferable that the nonionic be biodegradable.

One class of defoaming nonionics useful in this invention comprises a polyoxyalkylene glycol mixture consisting of a product which statistically represented ha a plurality of alternating hydrophobic and hydrophilic polyoxyalkylene chains or segments, the hydrophilic chains (segments) consisting of oxyethylene radicals linked one to the other, said statistically represented product having five such chains (segments) comprising three hydrophobic chains (segments) linked by two hydrophobic chains, the central hydrophobic chain (segment) constituting 30% to 34% by weight of the final product, the terminal hydrophobic chains (segments) togehter constituting 31% to 39% by weight of the final product, the linking hydrophilic chains (segments) constituting 31% to 35% by Weight of the final product, the intrinsic viscosity of the final product being from about 0.06 to 0.09 and the molecular weight of the final product being from about 3,000 to 5,000.

The polyoxyalkylene glycol mixture is prepared by condensing propylene oxide with water or propylene glycol to form a polyoxypropylene glycol, condensing ethylene oxide with the resulting polyoxypropylcne glycol, and then condensing propylene oxide with the resulting oxyethylated polyoxypropylene glycol. The preparation must be carried out in the above order to yield products having the required alternating hydrophobe-hydrophile structure.

These are described in US. Patents 3,048,548 and 3,082,172 which are by reference incorporated into this application.

The compositions of this invention can also be employed as rinse agents for use in machine dishwashing as described in US. Patent 3,082,172.

Another class of defoaming nonionic surfactant useful in this invention comprises a polyoxyalkylene glycol mixture consisting of a product which, statistically represented, has three or more alternating hydrophobic and hydrophilic segments. In this class of surfactant the first segment is hydrophobic such as that derived from a dior multi-substituted phenol, for example, a didodecyl phenol. The first hydrophilic segment of polyoxyethylene units is attached thereto and may be as low as weight percent of the starting hydrophobe. Then the second hy drophobic segment (such as that derived from polyoxypropylene units) is attached thereto and may be as low as weight percent of the starting hydrophobe. In such an example, the step of alternating first with a polyoxyethylene segment and then a polyoxypropylene segment may be carried out eight times. On the other hand, where only one hydrophilic segment of polyoxyethylene units is attached to the starting hydrophobe, the ethylene oxide employed may be as high as 460-625 weight percent of the starting hydrophobe and the final hydrophobic seg ment of polyoxypropylene units attached thereto may be as high as 675 900 Weight percent of the starting hydrophobe.

Still another class of defoaming nonionic surfactant useful in this invention comprises a polyoxyalkylene glycol mixture consisting of a product which, statistically represented, has three or more alternating hydrophobic and hydrophilic segments such as the first hydrophobic segment is derived from a biodegradable straight-chain primary alcohol, for example, nC H OH. Then, the first hydrcphilic segment of polyoxyethylene units is attached thereto and may be as low as 94 weight percent of the starting hydrophobe. Then the second hydrophobic segment (such as that derived from polyoxypropylene units) is attached thereto and may be as low as 200 Weight percent of the starting hydrophobe. In such an example, the step of alternating first with a polyoxyethylene segment and then a polyoxypr opylene segment may be carried out at least six times. On the other hand, when only one hydrophilic segment of polyoxyethylene units is attached to the starting hydrophobe, the ethylene oxide employed may be as high as 565-850 weight percent of the starting hydrophobe and the final hydrophobic segl 1 meat of polyoxypropylene units attached thereto may be as high as 124048.50 Weight percent of the starting hydrophobe.

A Wide variety of antioxidants including both primary or donor type antioxidants and synergists can be employed l2 Amino compounds, such as diarylamines and t-alkyl primary amines examples of which are: mixed alkylated diphenylamines, wnaphthylamine,

i o phenyl-ct-naphthylamine, which are capable or inhibiting, preventing or reducing phenypflmaphthyiamine, degradation of the nonionic surfactant. The mechanism di scc butyl p pheny1ene diamine by Which this inhibition of degradation occurs in 1'lO \:/21Y N hsnyl-N'-cyclohexyl-p-phenylene diamine, limits the scope oi this invention. Heretofore published N7Nndiphanypp-phsnYlenc diamine mechanisms of antiox dant activity may or may not take 10 phenothiazine place under the conditions or this nvention because the gpzdi d l i customary concept about antiox dation is complicated by t d d l primary amine, and the presence of alkaline matl'1alS AIltlOX1dE lntS of the t t d l primary amine; primary and synergrst types are widely described in the dicyciohexylamine literature and are i W965 employfzd m w and miscellaneous antioxidants such as: stuffs, soaps and cosmetics, pharmaceuticals, essential oils, fats, petroleum, rubber and textile oils, etc. Antioxidants 3 "b1?(limethyl'z'tbutylphenyl) sulfide of these types are described in Antioxidation and Antioxii dlthwcafwbonates} dants, vols. I and II by Lundherg (liiterscience Publisher, Zmc 'Pi e ls and 1962) which are by reference incorporated into the pres- 9, gua'mgme denvalwesent application. The antioxidants permitted in foods by The f llowing table presents examples of commercial the Food and Drug Administration are suitable for use in an iox dants which are advantageously employed in this this invention. These include, for example, the following invention:

TABLE II Antioxidants Commercial or Trade Supplier time 1. Food Grade Antioxidants:

1. Dilauryl tliiodipropiouate Dillydap Carlisle Chem. Wks.

2. Distearyl tliiooiprop into 3. fifi-thiodipropionic 80K 4. Butylated hydroxy-anisole Butylated liydroxy-toluene 6. n-Propyl gallate 7. Mixtures of 4, 5 and 6 II. Animal Feed Grade: l,2-dil1ydr trimetiiyl quinoline.

III. F.D.A. Approved: 2,2-mctliylene bis(4-n1ethyl-G- t-butylplienol). IV. Rubber and Gasoline Grade:

. Dicyelolicggylamiuen Mixtures of 1 and 2 Plienotlziazine PlieziotiiiazinoCuClz Polybutylatcd bisplienol V. Miscellaneous:

sation product.

primary antioxidants: gum guaiac; tocophcrols and related compounds; NDGA (nordihydroguaiaretic acid); gallio acid and the gallates (such as propyl gallate); BHA {butylated hydroxyanisole); BHT (butylated hydroxytoluene). Also included, for example, are the synergists: phospolipids, such as lecithin; citric acid; phosphoric acid; monoisopropyl citrate; stearyl citrate; ascorbic acid and related compounds such as sodium ascorbate, isoascorbic acid, sodium isoascorbate and ascorbyl palmitate; and thiodipropionic acid and related compounds such as didodecyl and dioctadecyl thiodipropionate, etc.

In addition, the primary antioxidants employed in stabilizing petroleum and rubber compositions are suitable in the invention and include: the rnono-, diand trialkylphenols, alkylated bisphenols, alkylated dihydroxyaromatic compounds and amino-phenols such as, for example,

Eastman Chem. Prods. Eastman Chem. Prods. Hercules Powder.

Catalin Corp.

Eastman Chem. Prods. Grilfith Laboratory.

Disterdap B A Tenox BHT Dalpac 200. Food Grade BHT enox PG Griffith G-50.

Santoquim. Monsanto Chem. Co.

CAO 5, CA0 14 Catalin Corp.

Antioxidant 224G. American Cyanamld.

nol)

. Monsanto Chem. Co.

. Vanderbilt. Ethyl Corp.

........ Antioxidant 702 Monsanto Chem. Co. Petrolite Corp.

In addition to nonionics and antioxidants, other constituents employed in detergent compositions can be employed such as those described herein. These include carbonates, phosphates, silicates and other alkalinic components of dishwashing compositions.

The following examples are presented for purposes of illustration and not of limitation. To demonstrate this invention under the extreme conditions of high alkalinity, a highly alkaline system was selected to illustrate the present invention, such as employed in cleaning ferrous metal equipment and utensils used in the food industry. To show the stabilizing eifect of antioxidants on defoaming surfactants under highly alkaline detergent conditions, the following formula was employed in the examples:

Percent Sodium hydroxide 30 Defoaming surfactant 5 Sodium metasilicate anhydrous 36 Sodium carbonate 30 Total 100 The procedure to study the stabilizing effect of antioxidants on defoaming surfactants in the above highly alkaline detergent composition was to mix the desired amount of surfactant with and Without antioxidants dircctly on the NaOH component. This direct contact With NaOH presented a very extreme test for alkaline stability. Samples of this composition with the various surfactants 13 to be tested were then stored in ovens to accelerate the aging process. At varying intervals samples were removed from storage and were tested in the Foam Retard Test for the defoaming ability of the defoaming surfactant remaining after extended storage.

The detergent compositions for storage testing were prepared in the following manner:

Step 1.The defoaming surfactants containing 1% antioxidant were prepared by dissolving g. antioxidant in 495 g. surfactant.

Step 2.A 2000-gram quantity of each test blend was made according to the proportions shown above, and the order of mixing was as listed. To a one gallon widemouth polyethylene jar with screw-cap lid were charged: 600 g. NaOH (as small flakes) 100 g. surfactant containing either 100 g. surfactant and no antioxidant; or 99 g. surfactant and 1 g. antioxidant.

These were then mixed well with a long handled spatula.

(Step 2, continued)-700 g. granular sodium metasilicate anhydrous was then charged thereto and mixed well with a spatula. 600 g. sodium carbonate was then charged and mixed well on a roller until thoroughly homogeneous. Portions of this final mixture were transferred into two one pint jars with screw-cap lids for storage in each of two ovens, one maintained at about 175 F. and the other at about 110 F.

Step 3.The jars were removed from the respective storage temperatures from time to time and mixed well. Samples of the contents were tested for their ability to retard the formation of foam according to the procedure for the Foam Retard Test.

FOAM RETARD TEST (1) Basis for test The typical amount of heavy-duty cleaning compound (containing about 5% defoaming nonionic surfactant) usually charged to a spraywashing machine is about /2 ounce/gallon of water. In brief, this is calculated as 2.84l4.2 g./ gallon for the detergent composition or 0.142 to 0.710 g./gallon (or 38-190 ppm.) for the defoaming nonionic surfactant (assuming that none has been lost by decomposition) in the wash water. The defoaming ability of the defoaming surfactant is tested in a foammaking machine. Since the foam machine employed in this test requires about 1.2 gallons water per wash, this is equivalent to using 3.4 to 17 g. of detergent composition.

The amount of food soil selected for this test (i.e. 5 cc. whole egg) is suflicient to cause a very rapid formation of foam, when exposed to the action of a detergent composition not containing defoaming nonionic surfactant. For example, a five-inch height of foam will develop within 30-60 seconds over a water surface area of 90 sq. inches.

As was previously explained, foaming must be suppressed in order to have adequate cleaning ability. In this test a drop in water pressure is observed when the foam height reaches 'two inches. Accordingly, we have arbitrarily set one inch of foam as the maximum amount of foam which can be tolerated while maintaining elfective cleaning ability.

(2.) Procedure Rinse foam machine well-twise with cold water and twice with the hot water as it is supplied from a hot water tank.

Drain well.

A heel of 65 0 ml. H O is left in the pump and piping of the system.

Charge detergent composition in quantities of 3 g., 4.5 g., -6 g., or 9 g. At the start of each stability test, these amounts of detergent composition contain undegnaded defoaming nonionic surfactant in amounts sufficient to supply the washwater with concentrations of 3 3, 50, 66 or 99 p.p.m. respectively.

Charge [i850 ml. hot 'water (temperature should be about 175" F). (The total water charge is about 4500 ml). T-urn pump on and recycle water until homogeneous. (Temperature of wash water should drop below F. and should be held above 140 F).

Foam height should be less than Mt inch. Charge 5 ml. of whole egg from a syringe and continue circulation through foam machine. Start stop watch as soon as egg is charged. Record foam height after 30 seconds and 1, 3, 5, 6, 7 and 8 minutes.

(3) Evaluation Readings below one inch after eight minutes is considered good retard action and is considered a passing or adequate performance. More than one-inch of foam after eight minutes is a failing retard action. (Readings of less than inch after eight minutes is excellent retard action).

The following surfactants with and without antioxidant were tested and compared:

(\A) Reaction pro-duct of one mole n-C H OH with 30 moles ethylene oxide and 50 moles propylene oxide.

(B) Reaction product of one mole didodecylphenol with 45 moles ethylene oxide and 50 moles propylene oxide.

(C) Reaction product of one mole water with about 45 moles propylene oxide, about 60 moles ethylene oxide and finally with about 60 moles propylene oxide.

(D) A highly branched amine oxyalky-late.

(E) A methyl ether derivative of .the reaction product of t-octyl-phenol and about 17 moles of ethylene oxide.

The antioxidants employed are as follows:

(1) 1$a11)toquin '(1,2-dihydro-6-ethoxy-2,2,4-trimethyl quin- (i l) Thenothiazine (HI) t-butylphenol-formaldehyde resin (IV) antioxidant 2246 2,2'-rnethylene bis-(4-methylo-t-b'utylphenol) (V) dicyolohexylamine (DOHA) The results of 'the Foam Retar-d Test are presented in Tables Jill and IV. The term Days of Adequate Defoaming refers to the number of days storage in which a fixed Weight of heavy duty alkaline detergent was able to suppress the foam height below one inch for 8 minutes.

Results of Foam Retard Test in which the heavy-duty formulation was stored at about F.

TABLE III AIzlays of e uate Surfactant Anti-oxidant Deio nnng with 9 g or less A 2246/DOHA a 36 A Santoquin 25 A. None i 21 25 25 15 22 C 21 25-29 17 a Wt. ratio was 40/60.

Results of Foam Retard Test in which the heavy-duty formulation was stored at about 110 F.

TABLE IV Da 5 of Ads uate Deioamin Surfactant Antioxidant With 3 g. With 4.5 g. or less or less A Santoquin 36 None 21 O. M75 30 [CL Phenoth 30 C None 11 E Phenothiazine.. 59 E None 29-36 As is quite evident, antioxidants and nonionics will be constantly developed which could be useful in this invention. It is, therefore, not only impossible to attempt a comprehensive catalogue of such compositions, but to attempt to describe the invention in its broader aspects in terms of specific chemical names of its components used would be too voluminous and unnecessary since one skilled in the art could by following the description of the invention herein select a useful composition. This invention lies in the use of suitable antioxidants in conjunction with nonionics and their individual compositions are important only in the sense that their properties can afiect this function. To precisely define each specific useful antioxidant, and nonionic in light of the present disclosure would merely call for chemical knowledge within the skill of the art in a manner analogous to a mechanical engineer who prescribes in the construction of a machine the proper materials and the proper dimensions thereof. From the description in this specification and with the knowledge of a chemist, one will know or deduce with confidence the applicability of specific antioxidants and nonionics, suitable for this invention by applying them in the compositions set forth herein. In analogy to the case of 'a machine, wherein the use of certain materials of construction or dimensions of parts would lead to no practical useful result, various materials will be rejected as inapplicable where others would be operative. One can obviously assume that no one will wish to employ a useless system nor will be misled because it is possible to misapply the teachings of the present disclosure to do so. Thus, any antioxidant and nonionic system that can perform the function stated herein can be employed.

Having thus described our invention what we claim as new and desire to obtain by Letters Patent is:

1. A stable alkaline detergent composition for use in machine dishwashing, machine bottlewashing and in general purpose heavy duty cleaners consisting essentially of (1) a mixture of sodium hydroxide, anhydrous sodium metasilicate and sodium carbonate, (2) a defoaming nonionic surfactant selected from the group consisting of (A) the reaction product of one mole n-C H OH with 30 moles ethylene oxide and 50 :moles propylene oxide,

(B) the reaction product of one mole didodecylphenol with moles ethylene oxide and moles propylene oxide,

(C) the reaction product of one mole water with about 45 moles propylene oxide, about moles ethylene oxide and finally with about 60 mole-s propylene oxide,

(D) a highly branched amine oxyalkylate, and

(E) a methyl ether derivative of the reaction product of t-octylphenol and about 17 moles ethylene oxide, and

(3) an antioxidant selected from the group consisting of (A) 1,Z-dihydro-6-ethoxy-2,2,4-trimethyl quinoline,

(B) Phenothiazine,

(C) t-butylphenol-formaldehyde resin,

(D) 2,2methylene bis-(4-methyl 6 t butylphenol),

and

(E) dicyclohexy-lamine,

(2) being present in an amount of 15% by weight of (1), said antioxidant being present in an amount suflicient to reduce, inhibit and prevent the degradation of said nonionic surfactant, whereby said nonionic surfactant is rendered stable thereby providing a stable alkaline detergent composition.

References Cited UNITED STATES PATENTS 3,168,478 2/11965 Stefcik 252-156 2,976,248 3/1961 Otrhalek 252-'156 3,078,230 2/1963 Cyba 25240'1 OTHER REFERENCES Arthur and Elizabeth Rose, The Condensed Chemical Dictionary, ninth edition, 1961, pp. 231, 391.

MURRAY KATZ, Primary Examiner.

L. D. ROSDOL, Examiner.

B. BETTIS, Assistant Examiner.