US3527707A - Liquid detergent composition - Google Patents

Abstract

1,054,217. Detergent compositions ESSO. RESEARCH & ENGINEERING CO. April 17, 1964 [June 5, 1963], No.16017/64. Heading C5D. A liquid heavy-duty detergent composition comprises a homogeneous solution of 5-20% C 12- C 22 alkane sulphonate, particularly sodium alkane sulphonate, 10-30% poly- or pyrophosphate builder, particularly tetrapotassium pyrophosphate, 1-8% sodium xylene or toluene sulphonate as hydrotrope and 40-85% water, all by weight. Potassium, ammonium and triethanolamine alkane sulphonates are less preferred. The composition may also contain sodium sulphate, anticorrosion agents such as sodium or potassium silicates, anti-redeposition agents such as carboxymethyl cellulose and its sodium salt, viscosity reducers such as ethanol or isopropanol and further detergents such as the anionics sodium lauryl or hexadecyl sulphate sodium sulphates of oxo alcohols, alkyl phenol polyether sulphates, polyether sulphates, fatty acidsoaps or alkylaryl sulphonates, and the non-ionics alkylphenol polyethenoxy compounds and fatty alkanolamides.

Description

United States Patent 3,527,707 LIQUID DETERGENT COMPOSITION James H. McAteer, Cranford, and Joseph F. Nelson,

Westfield, NJ., assignors to 'Esso Research and Engineering Company, a corporation of Delaware No Drawing. Filed June 5, 1963, Ser. No. 285,606 Int. Cl. C11d 3/065 US. Cl. 252138 6 Claims ABSTRACT OF THE DISCLOSURE The present invention relates to novel liquid synthetic detergent compositions. More particularly, this invention relates to built liquid alkane sulfonate detergent compositions of improved solubility having attractive biodegradation characteristics.

It is another object of this invention to provide homogeneous built liquid synthetic detergent compositions of increased organic and inorganic actives content.

Yet another object of this invention is to provide an inexpensive homogeneous liquid detergent composition of high solids content which utilizes minimal amounts of hydrotropes.

A further object of this invention is to provide synthetic liquid detergent compositions having improved biodegradation characteristics.

These and other objects are accomplished by utilizing alkane sulfonates as a major organic surfactant component of the built liquid detergent formulation. It has been discovered surprisingly that alkane sulfonates have superior compatibility with conventional builders when com pared with the extensively utilized alkylaryl sulfonates such as dodecylbenzene sulfonate. This superiority is evidenced by the fact that significantly smaller amounts of hydrotrope are required to obtain homogeneous, clear, liquid heavy-duty formulations containing amounts of g sodium alkane sulfonate equivalent to the amounts of The convenience afforded by built heavy-duty deterfactants. This is a consequence of the limited solubility of the sodium salts of such anionic surfactants in the presence of the required high concentrations of condensed phosphate builders. For example, sodium tetrapropylbenzene sulfonate, a commercial detergent, has such poor solubility in the presence of required builders that the detergent composition must be altered by expensive modifications to render it useful.

Various proposals have been made to overcome this serious solubility limitation. In one approach the sodium salt is replaced by the more soluble, but more expensive, potassium, ammonium or triethanol amine salts in order to obtain the requisite surfactant concentration. An alternate device is to utilize large amounts of hydrotropes, for example, xylene sulfonates, which act as coupling agents or co-solvents for surfactant salt. Thus, liquid formulations containing, for example, 845% of dodecylbenzene sulfonate salt commonly contain as much as 5- 15 hydrotrope, or expressed more commonly 60 to 100% or more of the organic surfactant content. The hydrotrope contributes to the cost of the final formulation but not to its detergency. Indeed, under some circumstances the hydrotrope may exert an adverse effect on detergency.

The class of surfactants known as alkylaryl sulfonates, examples of which have been discussed above, constitute the most extensively utilized active surfactant in modern detergent formulations. The present use of these surfactants for the formulation of detergents introduces the further disadvantages that such detergents as now constituted are resistant to biodegradation due to their branchy structure. The continued increase in use of non-biodegradable synthetic detergents is creating increasing concern on the part of public health authorities and the general public.

It is an object of this invention to provide built liquid synthetic detergent compositions having high water solubility.

alkylaryl sulfonates now being employed commercially. This result is completely unexpected in view of the fact that the water solubility of sodium alkane sulfonates and sodium dodecylbenzene sulfonate is very nearly identical at room temperature. Sodium alkane sulfonates may also be utilized in the manufacture of bar soaps and solid detergents in granular flake form. However, the instant invention is concerned only with the unexpected advanages obtainable from employing the sodium alkane sulfonate in the form of a heavy duty liquid detergent.

The alkane sulfonates employed in this invention may be in various salt forms, e.g., their potassium, ammonium or triethanol amine salts. Most preferred are the sodium salts due to their economic advantage. The alkane sulfonates are prepared from C to C and preferably C to C alkanes. These alkanes are preferably unbranched normal paraflins since excellent yields of highly biodegradable detergents are obtained from the straight chain paraffin. One to two methyl side chains per molecule are permissible but a high amount of branching is quite undersirable since it tends to increase the detergents resistance to biodegradation.

The alkane sulfonates employed in the detergent compositions of this invention may be prepared by a variety of techniques. In one method the normal paraflin feed may be reacted with sulfur dioxide and chlorine whereby the sulfochloride initially produced is converted to the desired alkane sulfonate by treatment with a base, e.g. NaOH. This process produces minor amounts of organic chlorides which tend to remain in the final product as an undesirable impurity. Another method of producing the desired alkane sulfonates is by the reaction of sodium bissulfite with a straight chain alkyl halide or by addition to a normal alpha olefin. This latter process yields primary sulfonates whose properties, e.g., solubility, limit their utility as detergent components. Yet another method for producing alkane sulfonates is by sulfoxidation of straight chain paraffins in the presence of ultra violet radiation.

A particularly preferred method of preparing the alkane sulfonates is by a self-sustaining sulfoxidation process. This process involves the over-all reaction after initiation, is continuously reacted with 0.2 to 4.0 moles of free sulfur dioxide per mole of parafiin and 0.01 to 2.0 moles of free oxygen per mole of paraflin at temperatures in the range of 30 to 160 F.

The alkane sulfonic acid obtained from the radiosulfoxidation or peroxide catalyzed process described above is then neutralized with an appropriate base, such as sodium or potassium hydroxide or carbonate, utilizing well-known techniques to obtain the corresponding alkane sulfonate surfactant. The resulting sulfonate salt will typically contain 25% of inorganic sulfate which results from the formation of sulfuric acid in the sulfoxidation reaction.

The preparation of alkane sulfonic acid and its sodium salt via the radio-sulfoxidation process may be subject to a wide variety of modifications. A more detailed description of the process may be found in copending, commonly assigned application Ser. No. 118,221, filed May 15, 1961 now abandoned.

The heavy-duty liquid detergents of this invention may contain any of the various types of builders and other adjuvants which are conventionally found in detergent formulations. Examples of useful builders include ethylene diamine tetraacetic acid salts, polyphosphates and pyrophosphates, particularly tetrapotassium pyrophosphate. Anticorrosion agents, such as sodium or potassium silicates, may be added to the formulation. In addition, anti-redeposition agents, such as sodium carboxymethyl cellulose may be present in the formulation. The formulation may also contain viscosity reducers, such as ethanol or isopropanol. Various optical bleaches, perfumes, dyes or other coloring agents may also be added. In addition, the formulation may at times contain other detergents in combination with the alkane sulfonate when specific results are desired. For example, sodium alcohol sulfates such as sodium lauryl sulfate, sodium hexadecyl sulfate or sodium sulfates of oxo alcohols may be added to the formulation.

The relative amounts of each component in the liquid detergent formulation may vary over broad limits. A typical detergent formulation may contain from to 20, preferably 5 to 15, and more preferably to parts by weight of the alkane sulfonate per 100 parts of solution of the sulfonate surfactant as well as 0 to 5 parts of the inorganic sulfate produced concurrently with the sulfonate. In addition, the formulation man contain from 5 to 25 parts by weight of building agent, such as a condensed phosphate, 1 to 5 parts by weight of an anticorrosion agent, such as a metasilicate, and 0.2 to 1.0 part of an anti-redeposition agent, such as sodium carboxymethyl cellulose. A viscosity reducer such as isopropanol may be present in amounts varying from 0 to 10 parts by weight per 100 parts of solution.

The weight ratio of sulfonate surfactant to the other components of the liquid detergent formulation may similarly vary over Wide ranges. Typically the composition may contain 0.5 to 4 and preferably 1 to 3 parts by weight of condensed phosphate builders per part of sulfonate surfactant; 0.2 to 0.5 and preferably 0.3 to 0.4 part per part of an anticorrosion agent, 0.02 to 0.10 part per part of anti-redeposition agent, and 0 to 1 part per part of a viscosity reducing agent.

A particularly preferred detergent composition, based on 100 parts of solution, consists of 10 to 15 parts of sodium alkane sulfonate as well as O to 3 parts of the sodium sulfate. In addition, the formulation contains 10 to 30, preferably to 25, parts of tetrapotassium pyrophosphate. Optionally there may also be present 2 to 4 parts, of a silicate, e.g., sodium metasilicate, 0.1 to 0.8 part of carboxymethyl cellulose, and also 2 to 5 parts of isopropyl alcohol.

Ideally, a liquid detergent composition combines a high solids content consisting of both organic surfactant and inorganic builder in a clear, homogeneous solution. It is essential that all of the ingredients in the formulation are fully solubilized since otherwise they will settle out and their utility and appeal as detergents will be lost. As mentioned earlier in this specification, the solids content of detergent formulations is conventionally increased by employing coupling or solubilizing agents known as hydrotropes. These materials function to increase the maximum solids content of the formulation but also increase the cost. It is a surprising feature of this invention that although conventional hydrotropes, such as sodium xylene and toluene sulfonates, are utilized in the novel formulations claimed herein, experimental data indicate that the amounts of these materials may be reduced by as much as 75% as compared to amounts utilized in alkylaryl sulfonate liquid detergents of a similar solids content.

In a preferred embodiment sodium xylene sulfonate is utilized in limited amounts as a hydrotrope for the sodium alkane sulfonate liquid detergent formulation. It has been discovered that as low as 1 part (by weight) per parts of solution will completely solubilize over 30 parts of solid sodium alkane sulfonate surfactant and builder.

Although the amount of hydrotrope needed for complete solubilization of the alkane sulfonate detergent is a complex function of the ratio of organic surfactant to builders and the total solids content and therefore is not capable of definition with exact certainty, it has been determined that the amount of hydrotrope needed is, at all points, significantly lower than would be expected in view of the vast experience with commercial alkylaryl formulations. Hence, utilizing an optimum ratio of about 2 parts of pyrophosphate builder per part of alkane sul fonate surfactant the amount of hydrotrope needed per 100 parts of detergent solution will vary from 1 to 8 as the total solids level varies from about 35 to 55 parts per 100 parts of solution. Expressed in other terms the amount of hydrotrope present in the detergent formulation will be 10 to 50 weight percent of the sodium alkane sulfonate in the formulation. It is to be understood that the amount of hydrotrope needed will increase as the total solids level increases and that therefore the maximum and minimum amounts specified are utilized with the maximum and minimum solids content respectively.

The invention may be further understood by reference to the following examples.

EXAMPLE 1 A series of detergent formulations was prepared in order to determine solubility limits of the solid surfactants in liquid compositions. All data are in terms of parts by weight per 100 parts of solution. The formulations are tabulated below.

1 Average carbon number: range= 013-026.

Formula I, containing sodium alkane sulfonate, was a clear, homogeneous solution although it contained only 1% of the sodium xylene sulfonate hydrotrope. Formula II which differs from Formula I in that commercial tetrapropylene benzene sulfonate is utilized in similar proportions contained in soluble solids. Formula III is similar to Formula II except for the large increase in the hydrotrope concentration and yet was nonetheless an opaque solution.

These results indicate the striking increase in compatibility of the sodium alkane sulfonate formulation as compared to commercial alkyl benzene sulfonate formulations. The results further show the decrease in hydrotrope utilization realized with the alkane sulfonate formulation.

EXAMPLE 2 A series of detergent formulations was prepared simrlar to Example 1 except that a much higher proportion of SOlldS was employed in the solutions. As before, all

compositions are shown as parts by weight per 100 parts by weight of solution. The sodium alkane sulfonate employed had an average carbon number of 15. The formulations are tabulated below.

Tetrapro- Tetra- Sodium pylene potassium Sodium alkane benzene pyrophosxylene Formula. sulfonate sulfonate phate sulfonate II- 1 0 so I 7 Formula I, containing sodium alkane sulfonate, was a EXAMPLE 3 A detergent formulation having the following composition in parts per 100 parts of solution by weight was analyzed for solubility.

Sodium nonodecane sulfonate 10 Sodium sulfate 2.5 Tetrapotassium pyrophosphate 20 Sodium xylene sulfonate l Isopropyl alcohol 2 The resulting composition was a clear homogeneous solution of reduced viscosity indicating that the addition of a viscosity reducing agent does not adversely affect solubility of the sodium alkane sulfonate liquid detergent formulation.

EXAMPLE 4 A C average paraifin feed consisting of a range of C to C was subjected to 'y radiation-initiated sulfoxidation followed by treatment with NaOH to yield sodium octadecane sulfonate and sodium sulfate. The sulfonate product was then mixed in a liquid detergent composition.

Parts (-wt.)/1 00 parts (wt.) of solution:

Sodium alkane sulfonate 10 Sodium sulfate 3.0 Tetrapotassium pyrophosphate 20 Sodium xylene sulfonate 1 The composition was a clear, homogeneous solution. Substitution of tetrapropylene benzene sulfonate in place of the alkane sulfonate gave an incompletely soluble system.

EXAMPLE 5 Parts (wt.)/100 parts (wt.) of solution Tetrapro Tetrapo- Sodium Sodium pylene tassium dimethyl 1 octadebenzene pyrophosbenzene Isopropyl cane sulfonate phate sulfonate alcohol sulfonate S1- 0 2D 5 5 S2. 0 10 20 5 5 1 High concentration used to solubilize tetrapropyl benzene sulfonate active.

The results of the laundering test are tabulated below.

Increase in Percent Reflectance of Cloth After Laundering Liquid Formulation, wt. percent 0.2 0.4

Water hardness, grJgal. 2 15 2 15 S1- 11. 31 6.75 16. 3s 14. 75 S2 16. 44 6. 00 16.25 15.31

The results indicate that the built sodium alkane sulfonate detergents are comparable to the commercially known tetrapropylene benzene sulfonate detergents. The excess hydrotrope utilized in the alkane sulfonate detergent had no beneficial eifect on the detergency values since hydrotropes do not improve laundering ability, per se.

EXAMPLE 6 Percent dis- Percent disappearance appearance of surfactant surfactant molecules fragments Tetrapropylene benzene sulfonate 0 0 Sodium octadecane sulfonate 100 76 (Substantially linear olefin based) alkyl benzene sulfonate 94 69 The results indicate the complete superiority of the alkane sulfonate detergents. Even when compared with alkyl benzene sulfonates based on fairly linear olefins, the alkane sulfonates show a superiority.

The advantages gained by the use of alkane sulfonates in liquid heavy-duty formulations are not restricted to those containing them as the sole surfactant. Thus the sodium alkane sulfonates are compatible with nonionic and anionic surfactants employed for the production of liquid heavy-duty detergents. These include, but are not limited to: alkylphenol polyethenoxy nonionics, alkylphenol polyether sulfates, polyethenoxy nonionics, polyether sulfates, fatty acid soaps, alkylaryl sulfonates and acid amino-alcohol condensation products.

Although the present invention has been described with reference to particular embodiments and examples it will be apparent to those skilled in the art that variations and modifications can be substituted therefor without departing from the true spirit of the invention which is limited only by the appended claims.

What is claimed is:

1. A liquid detergent composition consisting essentially of a homogeneous solution of 5 to 20 wt. percent of a C to C sodium alkane sulfonate, 10 to 30 wt. percent of a condensed phosphate selected from the group consisting of polyphosphate salts and pyrophosphate salts, 1 to 8 wt. percent of a hydrotrope selected from the group consisting of sodium xylene sulfonate and sodium toluene sulfonate and 40 to 85 wt. percent water.

2. A liquid detergent composition consisting of a homogeneous solution of 5 to 15 wt. percent of a C to C sodium alkane sulfonate, 10 to 30 Wt. percent of tetrapotassium pyrophosphate, up to 5 wt. percent sodium sulfate, 1 to 8 wt. percent sodium xylene sulfonate and 40 to 80 wt. percent water.

3. The composition of claim 1 wherein tetrapotassium pyrophosphate is the condensed phosphate builder and the sodium alkane sulfonate present is 50 wt. percent of the tetrapotassium pyrophosphate.

4. A liquid detergent composition consisting of a homogeneous solution of 10 wt. percent of a C to C sodium alkane sulfonate, 20 Wt. percent of tetrapotassium pyrophosphate, 2.5 Wt. percent sodium sulfate, 1 wt. percent sodium Xylene sulfonate, and 66.5 wt. percent water.

5. A liquid detergent composition consisting of a homogeneous solution of 15 wt. percent of a C to C sodium alkane sulfonate, 30 wt. percent of tetrapotassium pyrophosphate, 7 wt. percent sodium Xylene sulfonate and 48 wt. percent water.

6. A heavy duty liquid detergent composition consisting essentially of a phase stable solution of 5 through 20 wt. percent of sodium C to C n-alkane sulfonate wherein the sulfo group is attached to a secondary carbon References Cited UNITED STATES PATENTS 2,679,482 5/1954 Ross 252138 2,956;026' 10/1960 Lew- 252138 2,999,068 9/1961 Pilcher et al. 252-138 3,101,324 8/1963 Wixon 252138 3,085,982 4/1963 Steer et al. 252137 HERBERT B. GUYNN, Primary Examiner US. Cl. X.R.