Powder Detergent Compositions

The present invention relates to powder detergent compositions adapted for machine dish washing and which are effective in hard water. These compositions are significant in that they perform in the absence of phosphates.

Detergent compositions in powder form and which are adapted for machine dish washing are usually based on the presence of a large proportion of a phosphate component and frequently possess considerable alkalinity providing a pH above 8.5. This invention is concerned with providing a powder detergent composition which exhibits a pH not in excess of pH 8.5 and which does not require the presence of any phosphate component, but which is nonetheless capable of removing foods and leaving the dishes and glasses unspotted while being safe for the dishes which are washed.

In accordance with this invention, a powder detergent composition which does not require the presence of phosphates and which is effective at a pH in the range of pH 7.8 to pH 8.5 (measured in 1% water solution) consists essentially of the following components by weight:

1. FROM 2-8% OF LOW FOAMING NONIONIC SURFACTANT USEFUL FOR MACHINE DISH WASHING,

2. FROM 0.5-5% OF A CHLORINE OR OXYGEN-SUPPLYING BLEACHING AGENT,

3. FROM 15-85% OF BORAX,

4. SOLID PARTICULATE ORGANIC OR INORGANIC BUFFERING AGENT WHICH WILL NOT PRECIPITATE CALCIUM OR MAGNESIUM SALTS AT USE CONCENTRATION, SAID BUFFERING AGENT PROVIDING THE NECESSARY PH in the range of pH 7.8- pH 8.5, and

5. ANY BALANCE OF SAID DETERGENT CONSISTING ESSENTIALLY OF INERT PARTICULATE FILLER WHICH DOES NOT PRECIPITATE CALCIUM OR MAGNESIUM SALTS AT USE CONCENTRATION.

The heart of the low pH nonionic surfactant system is the employment of borax in a buffered environment having the narrow range of pH specified. Sodium bisulfate is the preferred buffer, but citric acid will further illustrate appropriate buffers. In the presence of borax in an amount of 15-85%, it is found that the nonionic surfactant-borax based detergent system when buffered to the required narrow range of pH will provide good detergency while eliminating filming and spotting. While ammonium compounds do not disturb this system, they are not needed.

As a result, an effective powder detergent composition adapted for machine dish washing is provided which is capable of performing in hard water, and in the absence of phosphates. In the preferred compositions, sequestrants are also omitted, and this is also significant because sequestrants add considerably to the expense of the composition. However, small amounts of a sequestrant, such as ethylene diamine tetraacetic acid which has an affinity for iron, may be present in an amount up to about 1% to avoid iron staining in those communities where significant amounts of iron are present in the water supply.

It should be observed that borax is a known cleaner, but it is not normally applicable to machine dish washing because it normally provides a pH above pH 8.5 (typically pH 9.2) and at such elevated pH, an undesirable film forms on dishes and glasses when hard water is used for washing. This disadvantage is sometimes countered by the use of large amounts of sequestrants. In this invention, contra to the concepts of the prior art, filming and spotting are avoided in a nonionic system buffered for a pH in 1% water solution in the narrow range of pH 7.8- pH 8.5.

Insofar as we are aware, none of the commercially available dish washing detergents now in use in the United States possess a pH below about 9.2. Current thinking is that a high pH and a high alkalinity are desirable for effective dish washing. A crucial finding in this invention is that this general perspective of the art is not correct in certain limited areas.

In contrast with the knowledge of the art, when the compositions of this invention possess a pH above 8.5, then the calcium and magnesium salts in the water are precipitated and water spotting is encountered. Thus, at customary pH, the compositions of this invention are ineffective.

While the upper limit of pH is critical as noted hereinbefore, the lower limit of pH is also important since, below pH 7.8, cleaning efficiency falls off.

Referring more particularly to the low foaming nonionic surfactants adapted for machine dish washing, these constitute a recognized class of materials, and while specific types of nonionic surfactants and blends thereof are preferred, the entire class is useful. The nonionic surfactant may be liquid or solid, the former being preferred. These liquid products are easily absorbed on the remaining components of the composition which are primarily solids, and do not interfere with the desired dry powder characteristic because the proportion of surfactant is small.

Ethylene oxide adducts of hydrophobic organic compounds, containing from about 3 to about 30 mols of adducted ethylene oxide per mol of hydrophobic organic compound, constitute the preferred nonionic surface active agent. The hydrophobic organic compound is subject to variation in known fashion, but it usually has a hydrocarbon portion with at least 8 carbon atoms and a single reactive group, either SH or more usually OH. Polyoxypropylene can also provide a hydrophobic base, but it carries two OH groups.

As examples of nonionic surface active agents which may be used and which are formed by reacting about 3 to about 30 mols of ethylene oxide with 1 mol of hydrophobic organic compound, there may be noted the adducts of alkyl phenols with ethylene oxide, e.g., isooctyl phenol or nonyl phenol; the adducts of the corresponding alkyl thiophenols with ethylene oxide; the ethylene oxide adducts with higher fatty alcohols of monoesters of hexahydric alcohols and inner ethers thereof such as sorbitan monolaurate, sorbitol monooleate and mannitan monopalmitate, and the adducts of polypropylene glycols with ethylene oxide. Solid surfactants in this category are illustrated by polyoxypropylene glycol of molecular weight 1700 adducted with ethylene oxide to provide a flake product containing 80% reacted ethylene oxide to provide a molecular weight of 7500.

Further suitable nonionic surfactants are polyoxyethylene esters of organic acids, such as the higher fatty acids, resin acids, tall oil, or acids from the oxidation of petroleum, and the like. The polyglycol esters will usually contain from about 3 to about 30 moles of ethylene oxide or its equivalent and 8 to 22 carbon atoms in the acyl group of the fatty acid. 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 nonionic surfactants are the polyethylene oxide condensates with higher fatty acid amides, such as the higher fatty acid primary amides and higher fatty acid mon- and diethanol-amides. Suitable agents are coconut fatty acid amide condensed with about 10 to about 30 mols of ethylene oxide. The fatty group will contain 8 to 22 carbon atoms, usually 10 to 18 carbon atoms. The corresponding sulphonamides may also be used.

Particularly suitable polyether nonionic surfactants are the polyethylene oxide ethers of higher aliphatic alcohols. Suitable alcohols are those having from 8 to 22 carbon atoms in the molecule, preferably from 10 to 18 carbon atoms. Examples thereof are iso-octyl, nonyl, decyl, dodecyl, tridecyl, tetradecyl, hexadecyl, octadecyl and oleyl alcohols which may be condensed with from 3-30 mols, preferably from 3-6 mols, of ethylene oxide. Commercial products of this type are illustrated by BASF Wyandotte products Plurafac RA-43 and RA-435. The corresponding alkyl mercaptans or thioalcohols condensed with ethylene oxide are also suitable for use in compositions of the present invention.

As previously indicated, the nonionic surfactant is used in an amount of from 2-8% of the powder composition, preferably 3-6%.

It is particularly preferred to employ as the nonionic surfactant straight C.sub.8 - C.sub.18 primary alcohols which have been adducted with from 3-6 mols of ethylene oxide per mol of alcohol. This type of nonionic surfactant is particularly desirable in combination with liquid nonionic surfactants in which ethylene oxide is adducted onto a poly(oxypropylene) base, termed a hydrophobe, and having a molecular weight in the range of about 900 to about 4000. The ethylene oxide adduction is carried out to provide from about 5 to about 55% of poly(oxyethylene). These liquid products are commonly known as Pluronic polyols, and the preferred products have a hydrophobe molecular weight of from 2100 to 3600 and contain from 5-45% of poly(oxyethylene). BASF Wyandotte products Pluronic L81, L92, and L101 are preferred, but the other liquid Pluronic polyols are also useful, ranging from L31 and L35 to L121 and L122.

When these two types of nonionic surfactants are used in combination, they may be used in a weight ratio of from 1:5 to 5:1, but are preferably used in a weight ratio of 1:2 to 2:1.

The chlorine or oxygen-supplying bleaching agent is entirely conventional, it being customary to employ such agents in dish washing compositions. The chlorine bleaching agents are more usual, these being illustrated by chlorinated trisodium phosphate, trichlorocyanuric acid, the sodium or potassium salt of dichlorocyanuric acid, and dichlorodimethylhydantoin. Inorganic hypochlorites such as lithium, potassium, and magnesium hypochlorites are also useful. The oxygen-supplying bleaching agents which may be used are also conventional, such as alkali metal persulfates, percarbonates, perborates, and the like, typically illustrated by sodium perborate.

The term "borax" is intended to identify alkali metal (primarily sodium) borate hydrates, typically the decahydrate. These borates have the formula Na.sub.2 B.sub.4 O.sub.7.xH.sub.2 O, and when proportions are given herein for borax, it will be understood that while one is not restricted to the decahydrate, it is the decahydrate which is normally used, and it is the decahydrate which is used as the basis for calculation.

On this basis, the borax component will constitute from 15-80% of the powder composition, preferably from 30-75%, and most preferably about 50%.

Typical buffering agents have been noted hereinbefore, and these are used in an amount to provide the desired pH, this usually requiring an amount of from 10-30% of the powder composition.

The inert particulate filler is subject to wide variation, sodium sulfate and potassium chloride being suitable. The filler is not necessary, but normally it is present in an amount of at least 15% of the composition.

Other inert fillers are illustrated by urea and sodium chloride, though urea is more costly.

Various materials may optionally be present, and some of these are noted below.

Anionic surfactants, such as dodecyl hydrogen phosphate, methyl naphthalene sulfonate, sodium-2-acetamidohexadecane-1-sulfonate, and the like, may be included in amounts up to about 2%, but the essential surfactant in this invention must be nonionic.

Ammonium compounds, such as ammonium sulfate or ammonium borate may be present, but they are not needed.

Enzymes are a desirable adjunct when it is desired to maximize the capacity to solubilize proteins. In such instance, the chlorine bleach should be avoided, and an oxygen bleach used in its place. The low pH which characterizes the compositions proposed herein eases the burden of incorporating enzymes.

Various other auxiliary agents may be present up to a total of about 5%, preferably up to about 1%. These are illustrated by perfumes, flow control agents, colorants, moisture absorbents, carriers for the nonionic surfactant (if liquid), antifoam agents, and the like.

In this specification, examples, and claims, all proportions are by weight unless otherwise specified.

The invention is illustrated in the examples which follow.

All of the above examples provided powdered detergent compositions which were effective machine dish washing detergents which could be used in hard water.

The invention is defined in the claims which follow.