addition of water to HAA at room temperature has traditionally not been convenient because of the high viscosity of the HAA at room temperatures and (b) most customers for the surfactant product are not conveniently availed of a blending environment for safe handling of hot HAA. Speculated benefits, therefore, of efficiency in shipping and handling and the benefits in safety from an HAA which could be blended into water at room temperature have not been realized. What is needed is an HAA having a useful viscosity at room temperature which can be added to water. The present invention solves this problem by providing HAA formulation embodiments and methods for their formulation so that an HAA having a relatively low viscosity at room temperature is provided.

The room temperature viscosity of an alkyl diphenyl oxide sulfonic acid blend is beneficially controlled according to the invention by admixing a fatty acid having a carboxylic chain length between 1 and 12 into the alkyl diphenyl oxide sulfonic acid blend to provide between 5 weight percentage and 50 weight percentage of fatty acid in the admixture. In further detail, the preferred embodiments are described as: 1-A method for viscosity control in an alkyl diphenyl oxide sulfonic acid, characterized by the step of: admixing a fatty acid having a carboxylic chain length between 1 and 12 into the alkyl diphenyl oxide sulfonic acid blend to provide between 5 weight percentage and 50 weight percentage of fatty acid in the admixture.

2-A method for preparation of an alkyl diphenyl oxide sulfonic acid blend characterized by the steps of: admixing formic acid, acetic acid, propionic acid, butanoic acid, pentanoic acid, valeric acid, hexanoic acid, heptanoic acid, octanoic acid, nonanoic acid, decanoic acid, undecanoic acid, or dodecanoic acid to provide between 5 weight percentage and 50 weight percentage of fatty acid in an admixture with an alkyl diphenyl oxide characterized by

where R is an alkyl radical having between 6 and 16 carbon atoms; and sulfonating said admixture with a sulfonating agent.

3-An alkyl diphenyl oxide sulfonic acid blend having between 5 weight percentage and 50 weight percentage of a fatty acid with a carboxylic chain length between 1 and 12.

4-An admixture composition of: formic acid, acetic acid, propionic acid, butanoic acid, pentanoic acid, valeric acid, hexanoic acid, heptanoic acid, octanoic acid, nonanoic acid, decanoic acid, undecanoic acid, or dodecanoic acid to provide between 5 weight percentage and 50 weight percentage of fatty acid in the admixture composition; and alkyl diphenyl oxide characterized by where R is an alkyl radical having between 6 and 16 carbon atoms.

Turning now to an overview of the Figures, Figure 1 shows the impact of various levels of octanoic acid upon the viscosity of a DOWFAX alkyl diphenyl oxide sulfonic acid surfactant blend.

Figure 2 shows the impact of various levels of octanoic acid upon the viscosity of a DOWFAX alkyl diphenyl oxide sulfonic acid surfactant blend in the high viscosity range.

Figure 3 shows the comparative impact of acetic, valeric, octanoic, and decanoic fatty acids on the viscosity of a DOWFAX alkyl diphenyl oxide sulfonic acid surfactant blend.

Figure 4 shows a ternary phase diagram showing significant liquid crystal phase regions for water, DOWFAX Detergent Acid, and fatty acid (acetic acid and octanoic acid).

In further discussion of details in the preferred embodiments, alkyl diphenyl oxide sulfonate surfactants are a Friedel-Crafts reaction product of an olefin and diphenyl oxide using AICI3 as a catalyst as indicated in Formula I. Formla I A1C13 R + + Olefin R Diphenyl oxide is present in excess and is recycled. The reaction yields a mixture of monoalkyl diphenyl oxide and dialkyl diphenyl oxide. The ratio of monoalkylation to dialkylation can be optimized depending on the end use of the products.

The next step in the process is the reaction of the alkylate with a sulfonating agent. This reaction (Formula II) is conducted in a solvent to dilute the reactant and to act as a diluent for the S03 used in the reaction.

Formuhn------SCH Formula II S03H R +--- RO S03 RCS03H +---0, Solvent S03H R R RX3 eR S03H S03H S03H R The reaction generally yields a mixture of monosulfonates and disulfonates according to Formulas III-VI. The level of disulfonation is determined by the end use of the product.

Generally, the disulfonation level is above 80 percent. The predominant component in the commercial reaction mixture is the monoalkyl diphenyl oxide disulfonate (MADS) of Formula IV, with monoalkyl diphenyl oxide monosulfonate (MAMS) of Formula III, dialkyl diphenyl oxide monosulfonate (DAMS) of Formula V, and dialkyl diphenyl oxide disulfonate (DADS) of Formula Vi essentially providing the remainder. <BR> <BR> <P>Formulain

Formula IV Formula V S03H RX3R FormulaVIS03H RQS03H R Alkyl diphenyloxide sulfonates and their traditional methods of preparation are well-known and reference is made thereto for purposes of describing this invention. Representative methods of preparation and handling are disclosed in U. S. Patents 2,990,375; 3,264,242, 3,634,272; 3,945,437; and 5,015,367. The commercially available species are predominantly (greater than 85 percent) disulfonates (the DADS and MADS described above) and are a mixture of mono-and di-alkyl with the percentage of dialkylation (the DADS and DAMS described above) being 5 to 25 and the percentage of monoalkylation (the MAMS and MADS described above) being 75 to 95 percent. Most typically, the commercially available species are 85 percent monoalkyl and 15 percent dialkyl.

The traditional method taught by Steinhauer et al. (U. S. Pat. No. 2,990,375) outlines a series of steps, the first step comprising preparing an alkyldiphenyl ether by reacting an olefin or an

olefin halide, such as tripropylenes, tetrapropylenes, pentapropylenes or dodecyl bromide, with diphenyl ether at a temperature between 50° C and 100° C in the presence of the Friedel-Crafts catalyst. The reaction mixture is washed with water to remove the catalyst, the phases separated, and the organic-rich phase subjected to distillation to obtain a fraction consisting of a mixture of monoalkylated diphenyl ether and dialkylated diphenyl ether. The number of alkyl substituents per diphenyl ether molecule can be controlled by adjusting the relative proportions of the reactants. Alternatively, the distillation can be performed so as to separate the monoalkylated and dialkylated diphenyl ethers from one another and from lower or higher boiling ingredients after which the monoalkylated and dialkylated diphenyl ether fractions can be combined at a desirable ratio.

The mixture of monoalkylated and dialkylated diphenyl ethers is subsequently reacted with a sulfonating agent, such as chlorosulfonic acid, sulfuric acid, or sulfur trioxide, in an inert solvent.

The general process of today uses reaction of an unsaturated hydrocarbon such as an alpha-olefin in the range of 6 to 16 carbons with diphenyl oxide in the presence of AICI3.

Reaction of alpha-olefins in the higher range of 18-30 carbons with diphenyl oxide in the presence of AICI3 holds some promise for fulfilling future surfactant needs. The ratio of mono-to dialkylation is controlled by the ratio of olefin to diphenyl oxide. Recycled excess diphenyl oxide is purified and reused. The rate of the reaction and the yield are controlled by the amount of catalyst and temperature of the alkylation. Excessively high temperatures as well as excessive amounts of catalyst yield higher levels of dialkylation and trialkylation. Low temperatures result in a low conversion of olefin. The ratios of concentration, catalyst and temperature are critical in keeping the reaction products consistent throughout the production cycle. The catalyst is removed from the process stream and the crude reaction mixture is then stripped of excess diphenyl oxide. Additional purification is optionally effected prior to the sulfonation reaction.

Sulfonation is generally carried out in a solvent. The solvent provides value in distributing the sulfonating agent, preventing localized burning and yield loss of the reaction product, and acting as a heat removal medium in control of the reaction process temperature. Current commercial process routes use sulfur dioxide, methylene chloride, or air as reaction solvents. The air sulfonation process eliminates the need for the removal and recycle of the liquid reaction solvent and is amenable to onsite generation of S03. Liquid solvents require

the use of liquid S03 that is diluted into the solvent prior to addition to the sulfonation reactors. Sulfur trioxide and chlorosulfonic acid are the two most common sulfonating agents.

After sulfonation, (1) the sulfonic acid is separated from its diluent, (2) the anhydrous acid (HAA) is diluted with water, and (3) neutralization of the diluted acid is optionally executed with an alkaline base such as sodium hydroxide. The material is packaged and sold in drums or bulk shipments as the customer requires.

The high viscosity of concentrated HAA derives from properties related to liquid crystal presence. This effect initiates at hydrophobe chain lengths above 6, is increasingly pronounced in observed samples to chain lengths of 16, and is expected to extend with greater significance to cases such as those which are contemplated via reaction of alpha- olefins in the higher range of 18-30 carbons with diphenyl oxide. Accordingly, a liquid crystal disrupter, or crystal structure breaker, is highly desirable as an additive for enabling useful viscosity in a useful HAA solids region (that is in an 60-95 percent solids range). In this regard, an additional component in the blend is most desirable which disrupts High Actives Acid (HAA) liquid crystal structure without imparting undesirable attributes to the resulting blend. In this regard, dimethylformamide (DMF) and methyl formamide (MF) effectively disrupt the liquid crystal structure in alkyl diphenyl oxide sulfonic acid blends used in deriving DOWFAX surfactants; but DMF and MF are not favored for use because of asserted health concerns.

It has been discovered that addition of fatty acids, for instance, caprylic (octanoic) or lauric acid, to highly concentrated surfactant sulfonic acid can greatly reduce the surfactant viscosity and improve handling characteristics of HAA. The use of such an additive to form particular blends enables the manufacture and use of concentrated acid forms of these surfactants.

In an alternative embodiment, admixing the fatty acid with the alkyl diphenyl oxide prior to sulfonation also provides reduction of surfactant viscosity and improved handling characteristics in the HAA material.

Formic acid, acetic acid, propionic acid, butanoic acid, pentanoic acid, valeric acid, hexanoic acid, heptanoic acid, octanoic acid, nonanoic acid, decanoic acid, undecanoic acid, and

dodecanoic (lauric) acid all provide benefit in low viscosity HAA formulations as further described with reference to the sample data in the Examples and Figures.

EXAMPLE 1: Samples containing straight-chain carboxylic acids from formic to lauric acid were blended with a representative alkyl diphenyl oxide sulfonic acid surfactant with a 16-carbon hydrophobe side chain (DOWFAX Detergent Acid, 94 wt percent concentration) at levels of 10 wt percent carboxylic acid based upon DOWFAX amount. The viscosities of these samples were measured at 40 °C. The results are listed in Table 1.

A Brookfield programmable rheometer, Model HDAV-III, was used to measure the viscosity of DOWFAX acid samples. The spindle size used was SC4-21. The viscosities of the samples were measured at 40 °C, a temperature at which the Thermosel temperature control stage was stable.

Approximately 8 mLs of sample were placed into the rheometer chamber. The spindle was inserted into the chamber so that the sample covered to 1/8 inch of the spindle shaft. The chamber was placed into the temperature control stage and the spindle connected to the rheometer. The rheometer was auto-zeroed. Stirring was started at 1 RPM and the sample was allowed to temperature equilibrate for ten minutes. After the ten minutes, the motor was stopped, the sample was allowed to sit for five minutes, then the motor was started again. A reading was taken after the spindle made 5 revolutions. The stirring was increased and the torque recorded until the allowable torque range on the instrument was exceeded. The equation below was used to convert torque to viscosity in units of cP: Viscosity = 100/RPM * TK * SMC * Torque Torque constant (TK) = 2 Spindle Multiply Constant (SMC) = 5

TABLE 1 Structure-Viscosity Modification Attributes of Carboxylic Acid Additives in DOWFAX Detergent Surfactant [9.1 wt percent carboxylic acid, 85.5 wt percent DOWFAX Detergent, 5.4 wt percent water] Carboxylic Acid Viscosity, cP Common (Svstematic (@ 40.8°C) Formic (methanoic) 7030 Acetic (ethanoic) 5847 Propanoic (propanoic) 4965 Butyric (butanoic) 5227 Valeric (pentanoic) 4970 Caproic (hexanoic) 6333 Enanthic (heptanoic) 6290 Caprylic (octanoic) 9360 Pelargonic (nonanoic) 9120 Capric (decanoic) 15820 Lauric (dodecanoic) 18040 EXAMPLE 2: Samples containing a variety of concentrations (from 2 to 50 wt percent based upon DOWFAX acid amount) of a representative carboxylic acid, octanoic acid, were blended with a representative alkyl diphenyl oxide sulfonic acid surfactant with a 16-carbon hydrophobe side chain (DOWFAX Detergent Acid, or DD-HAA in Figures 1 and 2) at a variety of aqueous dilution levels (from 44 to 94 wt percent DOWFAX acid). Each sample was blended until homogeneous. The viscosities of these samples were measured at 40 °C by the method indicated in Example 1. The results of these measurements are shown in Figures 1 and 2.

Some of the samples (a) exhibited liquid crystal behavior with very high viscosities and (b) turned solid-like in consistency. These samples typically exhibited viscosities exceeding the

upper measuring limit of the rheometer (1,000,000 cP), and these samples are shown as having viscosities of 1,000,000 cP in the Figures. The behavior of DOWFAX Detergent Acid containing no carboxylic acid ("0 wt percent OA") is shown for comparison purposes in both Figures 1 and 2.

The onset of the liquid crystal phase in Figure 1 is apparent at the rapid rise of viscosity with decrease of solids in the 69 percent to 90 percent solids range (depending on the particular concentration of octanoic acid). Only at 30 percent octanoic acid is the liquid crystal phase evidently suppressed.

EXAMPLE 3: Samples containing a variety of concentrations (from 2 to 30 wt percent) of four representative carboxylic acids (acetic, valeric, octanoic, and decanoic acids) each were blended with a representative alkyl diphenyl oxide sulfonic acid surfactant with a 16-carbon hydrophobe side chain (DOWFAX Detergent Acid, 94 wt percent concentration). Each sample was blended until homogeneous. The viscosities of these samples were measured at 40 °C by the method indicated in Example 1. The results of these measurements are shown in Figure 3. The behavior of DOWFAX Detergent Acid containing no carboxylic acid (at"0 wt percent additive concentration"on the graph) is shown for comparison.

Comparison of the data for all acids at concentrations above 0 percent in Figure 3 with the 0 percent case help to further illustrate the general viscosity reducing influence of fatty acids on an HAA such as the tested DOWFAX Detergent Acid.

The data of Figure 3 indicate a higher significance of fatty acid chain length toward viscosity reduction at the 5 weight percent fatty acid concentration.

EXAMPLE 4: Samples containing various ratios of either acetic or octanoic acid, as representative carboxylic acids, of a representative alkyl diphenyl oxide sulfonic acid surfactant with a 16- carbon hydrophobe side chain (DOWFAX Detergent Acid), and water were prepared. Each sample was blended until homogeneous. Gross visual examination of each sample was made to identify the presence of a solid-like, liquid crystal phase. Data defining the composition of samples exhibiting such a highly viscous phase were plotted on a ternary

phase diagram to ascertain the phase boundary. Boundary regions for blends with either acetic acid or octanoic acid are shown in Figure 4.

The ternary phase diagram of Figure 4 shows significant liquid crystal phase regions for water, DOWFAX surfactant acid, and two fatty acids (acetic acid and octanoic acid). The phase boundary is indicated where the viscosity measures 1 million centipoise or greater at room temperature and pressure. The high viscosity area underscores the importance of the method of addition in admixing the alkyl diphenyl oxide sulfonic acid surfactant and fatty acid blend of the described embodiments with water. It should be noted successful combination of HAA with water requires attentiveness to the issue of progression in component concentration with respect to phase control according to the depiction of Figure 4. In this regard, an alkyl diphenyl oxide sulfonic acid surfactant acid/fatty acid admixture should be added to water in use of the highly concentrated HAA in creating a surfactant for use and sale; water should not be added to the alkyl diphenyl oxide sulfonic acid surfactant acid/ fatty acid admixture in use of the highly concentrated HAA in creating a surfactant for use and sale. In this regard, with reference to Figure 4, the addition of water to the alkyl diphenyl oxide sulfonic acid surfactant acid/fatty acid admixture can function to induce substantive liquid crystal formation in the admixture and render the admixture too viscous for use since the dilution of HAA with water effects entry into the liquid crystal region.

EXAMPLE 5: Octanoic acid at a 10 weight percent concentration based upon expected levels of DOWFAX Detergent Acid was added to alkylate during a sulfonation reaction. A control reaction containing no octanoic acid under identical conditions yielded DOWFAX Detergent Acid exhibited a viscosity of 40,200 cP. The product of the sulfonation reaction containing the 10 weight percent octanoic acid had viscosity of 3,100 cP.

The beneficial results from use of fatty acids in the described embodiments indicate that fatty alcools, fatty amines, or even linear alkanes in the C6-C, 8 range warrant consideration and empirical study in contemplated embodiment blends.