| PATENT NUMBER | This data is not available for free |
| PATENT GRANT DATE | 09.05.00 |
| PATENT TITLE |
Mid-chain branched alkyl sulfate surfactants |
| PATENT ABSTRACT |
Mixtures of mid-chain branched primary alkyl sulfate surfactants useful in cleaning compositions, especially for lower water temperature applications, alone or formulated with other surfactants for the purpose of modifying the low temperature cleaning properties of the cleaning formulations. The present invention also relates to novel mid-chain branched primary alkyl sulfate surfactants suitable for use in surfactant mixtures. |
| PATENT INVENTORS | This data is not available for free |
| PATENT ASSIGNEE | This data is not available for free |
| PATENT FILE DATE | October 13, 1998 |
| PATENT REFERENCES CITED |
Finger, et al., "Detergent Alcohols--the effect of alcohol structure and molecular weight on surfactant properties", J. Amer. Oil Chemists' Society, vol. 44, (1967), p. 525. NWA. K. R. Wormuth, et al., "Phase Behavior of Branched Surfactants in Oil and Water", Langmuir, vol. 7, (1991), pp. 2048-2053. *NWA. R. Varadaraj, et al., "Fundamental Interfacial Properties of Alkyl-Branched Sulfate and Ethoxy Sulfate Surfactants Derived from Guerbet Alcohols. 1. Surface and Instantaneous Interfacial Tensions", J. Phys. Chem., vol. 95 (1991), pp. 1671-1676. *NWA. R. Varadaraj, et al., "Relationship between Fundamental Interfacial Properties and Foaming in Linear Branched Sulfate, Ethoxysulfate, and Ethoxylate Surfactants", Journal of Colloid and Interface Science, vol. 140, No. 1 (Nov. 1990), pp. 31-34. R. Varadaraj, et al., "Micropolarity and Water Penetration in Micellar Aggregates of Linear and Branched Hydrocarbon Surfactants", Langmuir, vol. 6 (1990), pp. 1376-1378 *NWA. R. Varadaraj, et al., "Relationship between Dynamic Contact Angle and Dynamic Surface Tension Properties for Linear and Branched Ethoxylate, Ethoxysulfate, and Sulfate Surfactants", Journal of Colloid and Interface Science, vol. 147, No. 2 (Dec. 1991), pp. 403-406. CEH Marketing Research Report "Detergent Alcohols" by R.F. Modler, et al., Chemical Economics Handbook, (1993), pp. 609.5000-609.5002 *NMA. "Alcohols, Higher Aliphatic", Kirk Othmer's Encyclopedia of Chemical Technology, 4.sup.th Ed., Wiley, N.Y., (1991), vol. 1, pp. 865-913. * NWA. "Liquid Fuels", Kirk Othmer's Encyclopedia of Chemical Technology, Wiley, N.Y., (1989), vol. 11, pp. 447-489. * NMA. "Oxo Process", Kirk Othmer's Encyclopedia of Chemical Technology, Wiley, N.Y., (1989), vol. 16, pp. 637-653. *NWA. "Sasol Detergent Alcohols", R&D Technical Bulletin, Sasol Alpha Olefins, (Oct. 1, 1996), pp. 1-12. |
| PATENT PARENT CASE TEXT | This data is not available for free |
| PATENT CLAIMS |
What is claimed is: 1. A surfactant composition comprising from about 0.001% to about 100% of a mixture of two or more mid-chain branched primary alkyl sulfates having the formula: ##STR39## wherein the total number of carbon atoms in the branched primary alkyl moiety of this formula, including the R, R.sup.1, and R.sup.2 branching, is from 14 to 20, and wherein further for this surfactant mixture the average total number of carbon atoms in the branched primary alkyl moieties having the above formula is within the range of greater than 14.5 to about 17.5, R, R.sup.1, and R.sup.2 are each independently selected from hydrogen and C.sub.1 -C.sub.3 alkyl, provided R, R.sup.1, and R.sup.2 are not all hydrogen and, when z is 1, at least R or R.sup.1 is not hydrogen; M is one or more cations; w is an integer from 0 to 13; x is an integer from 0 to 13; y is an integer from 0 to 13; z is an integer of at least 1; and w+x+y+z is from 8 to 14. 2. A composition according to claim 1 wherein at least 0.001%, of the mixture comprises one or more mid-chain branched primary alkyl sulfates having the formula ##STR40## wherein the total number of carbon atoms, including branching, is from 15 to 18, and wherein further for this surfactant mixture the average total number of carbon atoms in the branched primary alkyl moieties having the above formula is within the range of greater than 14.5 to about 17.5; R.sup.1 and R.sup.2 are each independently hydrogen or C.sub.1 -C.sub.3 alkyl; M is a water soluble cation; x is from 0 to 11; y is from 0 to 11; z is at least 2; and x+y+z is from 9 to 13; provided R.sup.1 and R.sup.2 are not both hydrogen. 3. A composition according to claim 1 wherein M is selected from the group consisting of sodium, potassium, calcium, magnesium, quaternary alkyl amines having the formula ##STR41## wherein R.sup.3, R.sup.4, R.sup.5 and R.sup.6 are independently selected from hydrogen, C.sub.1 -C.sub.22 alkylene, C.sub.4 -C.sub.22 branched alkylene, C.sub.1 -C.sub.6 alkanol, C.sub.1 -C.sub.22 alkenylene, C.sub.4 -C.sub.22 branched alkenylene, and mixtures thereof. 4. A composition according to claim 1 wherein M is sodium, potassium, and mixtures thereof. 5. A composition according to claim 1 wherein at least 5%, preferably at least about 20%, of the mixture comprises one or more mid-chain branched primary alkyl sulfates wherein x+y is equal to 9 and z is equal to 2. 6. A composition according to claim 1 wherein at least 5%, preferably at least about 20%, of the mixture comprises mid-chain branched primary alkyl sulfates wherein x+y is equal to 9 and z is equal to 2. 7. A composition according to claim 1 wherein at least 5%, preferably at least about 20%, of the mixture comprises mid-chain branched primary alkyl sulfates wherein x+y is equal to 10 and z is equal to 2. 8. A surfactant composition comprising a mixture of branched primary alkyl sulfates having the formula ##STR42## wherein the total number of carbon atoms per molecule, including branching, is from 14 to 20, and wherein further for this surfactant mixture the average total number of carbon atoms in the branched primary alkyl moieties having the above formula is within the range of greater than 14.5 to about 17.5; R, R.sup.1, and R.sup.2 are each independently selected from hydrogen and C.sub.1 -C.sub.3 alkyl, provided R, R.sup.1, and R.sup.2 are not all hydrogen; M is a water soluble cation; w is an integer from 0 to 13; x is an integer from 0 to 13; y is an integer from 0 to 13; z is an integer of at least 1; and w+x+y+z is from 8 to 14; provided that when R.sup.2 is a C.sub.1 -C.sub.3 alkyl the ratio of surfactants having z equal to 1 to surfactants having z of 2 or greater is at least about 1:1. 9. A surfactant composition according to claim 8 wherein the amount of branched surfactants, when R.sup.2 is a C.sub.1 -C.sub.3 alkyl, comprises less than about 20%, of branched primary alkyl sulfates having the above formula wherein z equals 1. 10. A detergent composition comprising: (a) from about 0.001% to about 99% of a mixture of mid-chain branched primary alkyl sulfate surfactants, said mixture comprising at least about 5% by weight of two or more mid-chain branched alkyl sulfates having the formula: ##STR43## or mixtures thereof; wherein M represents one or more cations; a, b, d, and e are integers, a+b is from 10 to 16, d+e is from 8 to 14 and wherein further when a+b=10, a is an integer from 2 to 9 and b is an integer from 1 to 8; when a+b=11, a is an integer from 2 to 10 and b is an integer from 1 to 9; when a+b=12, a is an integer from 2 to 11 and b is an integer from 1 to 10; when a+b=13, a is an integer from 2 to 12 and b is an integer from 1 to 11; when a+b=14, a is an integer from 2 to 13 and b is an integer from 1 to 12; when a+b=15, a is an integer from 2 to 14 and b is an integer from 1 to 13; when a+b=16, a is an integer from 2 to 15 and b is an integer from 1 to 14; when d+e=8, d is an integer from 2 to 7 and e is an integer from 1 to 6; when d+e=9, d is an integer from 2 to 8 and e is an integer from 1 to 7; when d+e=10, d is an integer from 2 to 9 and e is an integer from 1 to 8; when d+e=11, d is an integer from 2 to 10 and e is an integer from 1 to 9; when d+e=12, d is an integer from 2 to 11 and e is an integer from 1 to 10; when d+e=13, d is an integer from 2 to 12 and e is an integer from 1 to 11; when d+e=14, d is an integer from 2 to 13 and e is an integer from 1 to 12; wherein for this surfactant mixture the average total number of carbon atoms in the branched primary alkyl moieties having the above formulas is within the range of greater than 14.5 to about 17.5; and (b) from about 1% to about 99.999% of detergent composition adjuct ingredients. 11. A mid-chain branched primary alkyl sulfate having the formula ##STR44## wherein R.sup.1 and R.sup.2 are each independently hydrogen or C.sub.1 -C.sub.3 alkyl; M is a water soluble cation; x is an integer from 0 to 12; y is an integer from 0 to 12; z is an integer of at least 2; and x+y+z is from 11 to 14; provided: a) R.sup.1 and R.sup.2 are not both hydrogen; b) when one R.sup.1 or R.sup.2 is hydrogen and the other R.sup.1 or R.sup.2 is methyl, then x+y+z is not 12 or 13; and c) when R.sup.1 is hydrogen and R.sup.2 is methyl, x+y is not 11 when z is 3, and x+y is not 9 when z is 5. 12. A compound according to claim 11 wherein M is selected from the group consisting of sodium, potassium, calcium, magnesium, quaternary alkyl amines having the formula ##STR45## wherein R.sup.3, R.sup.4, R.sup.5 and R.sup.6 are independently selected from hydrogen, C.sub.1 -C.sub.22 alkylene, C.sub.4 -C.sub.22 branched alkylene, C.sub.1 -C.sub.6 alkanol, C.sub.1 -C.sub.22 alkenylene, C.sub.4 -C.sub.22 branched alkenylene, and mixtures thereof. 13. A compound according to claim 11 wherein M is sodium, potassium, and mixtures thereof. 14. A compound according to claim 11 wherein R is methyl, R.sup.1 is hydrogen, x is from 0 to 10, y is from 0 to 10, z is 2, x+y+z is equal to 11. 15. Alkyl sulfate compounds of formula: ##STR46## wherein: a and b are integers and a+b is 12 or 13, a is an integer from 2 to 11, b is an integer from 1 to 10 and M is selected from sodium, potassium, ammonium and substituted ammonium. 16. Alkyl sulfate compounds of formula: ##STR47## wherein: d and e are integers and d+e is from 10 or 11; and wherein further when d+e=10, d is an integer from 2 to 9 and e is an integer from 1 to 8; when d+e=11, d is an integer from 2 to 10 and e is an integer from 1 to 9; and M is selected from sodium, potassium, ammonium and substituted ammonium. 17. Mono-methyl branched primary alkyl sulfates selected from the group consisting of: 3-methyl pentadecanol sulfate, 4-methyl pentadecanol sulfate, 5-methyl pentadecanol sulfate, 6-methyl pentadecanol sulfate, 7-methyl pentadecanol sulfate, 8-methyl pentadecanol sulfate, 9-methyl pentadecanol sulfate, 10-methyl pentadecanol sulfate, 11-methyl pentadecanol sulfate, 12-methyl pentadecanol sulfate, 13-methyl pentadecanol sulfate, 3-methyl hexadecanol sulfate, 4-methyl hexadecanol sulfate, 5-methyl hexadecanol sulfate, 6-methyl hexadecanol sulfate, 7-methyl hexadecanol sulfate, 8-methyl hexadecanol sulfate, 9-methyl hexadecanol sulfate, 10-methyl hexadecanol sulfate, 11-methyl hexadecanol sulfate, 12-methyl hexadecanol sulfate, 13-methyl hexadecanol sulfate, 14-methyl hexadecanol sulfate, and mixtures thereof. 18. Di-methyl branched primary alkyl sulfates selected from the group consisting of: 2,3-methyl tetradecanol sulfate, 2,4-methyl tetradecanol sulfate, 2,5-methyl tetradecanol sulfate, 2,6-methyl tetradecanol sulfate, 2,7-methyl tetradecanol sulfate, 2,8-methyl tetradecanol sulfate, 2,9-methyl tetradecanol sulfate, 2,10-methyl tetradecanol sulfate, 2,11-methyl tetradecanol sulfate, 2,12-methyl tetradecanol sulfate, 2,3-methyl pentadecanol sulfate, 2,4-methyl pentadecanol sulfate, 2,5-methyl pentadecanol sulfate, 2,6-methyl pentadecanol sulfate, 2,7-methyl pentadecanol sulfate, 2,8-methyl pentadecanol sulfate, 2,9-methyl pentadecanol sulfate, 2,10-methyl pentadecanol sulfate, 2,11-methyl pentadecanol sulfate, 2,12-methyl pentadecanol sulfate, 2,13-methyl pentadecanol sulfate, and mixtures thereof. -------------------------------------------------------------------------------- |
| PATENT DESCRIPTION |
FIELD OF THE INVENTION The present invention relates to mixtures of mid-chain branched primary alkyl sulfate surfactants useful in laundry and cleaning compositions, especially granular and liquid detergent compositions. These surfactant mixtures are also suitable for formulation with other surfactants for the purpose of providing improved surfactant systems, especially for use in detergent compositions which will be used in laundry processes involving low water temperature wash conditions. The present invention also relates to novel mid-chain branched primary alkyl sulfate surfactants suitable for use in the surfactant mixtures. BACKGROUND OF THE INVENTION Conventional detersive surfactants comprise molecules having a water-solubilizing substituent (hydrophilic group) and an oleophilic substituent (hydrophobic group). Such surfactants typically comprise hydrophilic groups such as carboxylate, sulfate, sulfonate, amine oxide, polyoxyethylene, and the like, attached to an alkyl, alkenyl or alkaryl hydrophobe usually containing from about 10 to about 20 carbon atoms. Accordingly, the manufacturer of such surfactants must have access to a source of hydrophobe groups to which the desired hydrophile can be attached by chemical means. The earliest source of hydrophobe groups comprised the natural fats and oils, which were converted into soaps (i.e., carboxylate hydrophile) by saponification with base. Coconut oil and palm oil are still used to manufacture soap, as well as to manufacture the alkyl sulfate ("AS") class of surfactants. Other hydrophobes are available from petrochemicals, including alkylated benzene which is used to manufacture alkyl benzene sulfonate surfactants ("LAS"). The literature asserts that certain branched hydrophobes can be used to advantage in the manufacture of alkyl sulfate detersive surfactants; see, for example, U.S. Pat. No. 3,480,556 to deWitt, et al., Nov. 25, 1969. However, it has been determined that the beta-branched surfactants described in the '556 patent are inferior with respect to certain solubility parameters, as evidenced by their Krafft temperatures. It has further been determined that surfactants having branching towards the center of carbon chain of the hydrophobe have much lower Krafft temperatures. See: "The Aqueous Phase Behavior of Surfactants", R. G. Laughlin, Academic Press, New York (1994) p. 347. Accordingly, it has now been determined that such surfactants are preferred for use especially under cool or cold water washing conditions (e.g., 20.degree. C.-5.degree. C.). Generally, alkyl sulfates are well known to those skilled in the art of detersive surfactants Alkyl sulfates were developed as a functional improvement over traditional soap surfactants and have been found to possess improved solubility and surfactant characteristics. Linear alkyl sulfates are the most commonly used of the alkyl sulfate surfactants and are the easiest to obtain. For example, long-chain linear alkyl sulfates, such as tallow alkyl sulfate, have been used in laundry detergents. However, these have significant cleaning performance limitations, especially with the trend to lower wash temperatures. Also, as noted hereinbefore, the 2-alkyl or "beta" branched alkyl sulfate are known. In addition to U.S. Pat. No. 3,480,556 discussed above, more recently EP 439,316, published Jul. 31, 1991, and EP 684,300, published Nov. 29, 1995, describe these beta-branched alkyl sulfates. Other recent scientific papers in the area of branched alkyl sulfates include R. Varadaraj et al., J. Phys. Chem., Vol. 95, (1991), pp 1671-1676 which describes the surface tensions of a variety of "linear Guerbet" and "branched Guerbet"--class surfactants including alkyl sulfates. "Linear Guerbet" types are essentially "Y-shaped", with 2-position branching which is a long straight chain as in: ##STR1## wherein Z is, for example, OSO.sub.3 Na. "Branched Guerbet" types are likewise 2-position branched, but also have additional branching substitution, as in: ##STR2## wherein Z is, for example, OSO.sub.3 Na. See also Varadaraj et al., J. Colloid and Interface Sci., Vol. 140, (1990), pp 31-34 relating to foaming data for surfactants which include C12 and C13 alkyl sulfates containing 3 and 4 methyl branches, respectively (see especially p. 32). Known alkyl sulfates also include: 1. Primary akyl sulfates derived from alcohols made by Oxo reaction on propylene or n-butylene oligomers, for example as described in U.S. Pat. No. 5,245,072 assigned to Mobil Corp. 2. Primary alkyl sulfates derived from oleic-containing lipids, for example the so-called "isostearyl" types; see EP 401,462 A, assigned to Henkel, published Dec. 12, 1990, which describes certain isostearyl alcohols and ethoxylated isostearyl alcohols and their sulfation to produce the corresponding alkyl sulfates such as sodium isostearyl sulfate. 3. Primary alkyl sulfates, for example the so-called "tridecyl" types derived from oligomerizing propylene with an acid catalyst followed by Oxo reaction; 4. Primary alkyl sulfates derived from "Neodol" or "Dobanol" process alcohols: these are Oxo products of linear internal olefins or are Oxo products of linear alpha-olefins. The olefins are derived by ethylene oligomerization to form alpha-olefins which are used directly or are isomerized to internal olefins and metathesized to give internal olefins of differering chain-lengths; 5. Primary alkyl sulfates derived from the use of "Neodol" or "Dobanol" type catalysts on internal olefins derived from feedstocks which differ from those normally used to make "Neodol" or "Dobanol" alcohols, the internal olefins being derived from dehydrogenation of paraffins from petroleum; 6. Primary alkyl sulfates derived from conventional (e.g., high-pressure, cobalt-catalyzed) Oxo reaction on internal olefins, the internal olefins being derived from dehydrogenation of paraffins from petroleum; 7. Primary alkyl sulfates derived from conventional (e.g., high-pressure, cobalt-catalyzed) Oxo reaction on alpha-olefins; 8. Primary alkyl sulfates derived from natural linear fatty alcohols such as those commercially available from Procter & Gamble Co.; 9. Primary alkyl sulfates derived from Ziegler alcohols such as those commercially available from Albermarle; 10. Primary alkyl sulfates derived from reaction of normal alcohols with a Guerbet catalyst (the function of this well-known catalyst is to dehydrogenate two moles of normal alcohol to the corresponding aldehyde, condense them in an aldol condensation, and dehydrate the product which is an alpha, beta- unsaturated aldehyde which is then hydrogenated to the 2-alkyl branched primary alcohol, all in one reaction "pot"); 11. Primary alkyl sulfates derived from dimerization of isobutylene to form 2,4,4'-trimethyl-1-pentene which on Oxo reaction to the aldehyde, aldol dimerization, dehydration and reduction gives alcohols; 12. Secondary alkyl sulfates derived from sulfuric acid addition to alpha- or internal-olefins; 13. Primary alkyl sulfates derived from oxidation of paraffins by steps of (a) oxidizing the paraffin to form a fatty carboxylic acid; and (b) reducing the carboxylic acid to the corresponding primary alcohol; 14. Secondary alkyl sulfates derived from direct oxidation of paraffins to form secondary alcohols; 15. Primary or secondary alkyl sulfates derived from various plasticizer alcohols, typically by Oxo reaction on an olefin, aldol condensation, dehydration and hydrogenation (examples of suitable Oxo catalysts are the conventional Co, or more recently, Rh catalysts); and 16. Primary or Secondary alkyl sulfates other than of linear primary type, for example phytol, farnesol, isolated from natural product sources. Beyond such known alkyl sulfates, however, is a vast array of other possible alkyl sulfate compounds and mixtures whose physical properties may or may not make them useful as laundry detergent surfactants. (I)-(XI) display just some of the possible variations (the salts are depicted only as the common sodium salts). ##STR3## These structures are also useful to illustrate terminology in this field: thus, (I) is a "linear" alkyl sulfate. (I) is also a "primary" alkyl sulfate, in contrast with (VII) which is a "secondary" alkyl sulfate. (II) is also a "primary" alkyl sulfate--but it is "branched". The branching is exclusively in the "2-position" as in the so-called "linear Guerbet" alkyl sulfates: carbon-counting by convention starts with C1, which is the carbon atom covalently attached to the sulfate moiety. (III) can be used to represent any one of a series of branched alkyl sulfates which, when e is an integer having the value 1 or greater, have only "non-2-position branching". According to conventional wisdom, at least for linear surfactant compounds, the hydrocarbon portion needs to have at least 12 carbon atoms, preferably more, to acquire good detergency. The indices a,b,c,d,e,f,g,h,i,j,k,l,m,n,o,p,q can, in principle, be adjusted to accommodate this need. Compound (VIII) is the alkyl sulfate derived from a naturally occurring branched alcohol, phytol. Compound (IX) is a highly branched alkyl sulfate, which can, for example, be made by sulfating an alcohol derived from dimerizing isobutylene and performing an Oxo reaction on the product. Compound (X), when q=14, is an isostearyl alkyl sulfate; another so-called "isostearyl" alkyl sulfate has the general structure (III)--such compounds can be made by sulfating an alcohol derived from a monomeric by product of the dimerization of oleic acid having 18 carbon atoms, i.e., d+e=14 in (III). Compound (XI) is a "neo" alkyl sulfate. (XII) and (XIII) are substructures depicting "vicinal" (XII) and "geminal" or "gem" (XIII) dimethyl branching, respectively. Such substructures can, in principle, occur in alkyl sulfates and other surfactants. Conventional alkyl sulfates can, moreover, be either saturated or unsaturated. Sodium oleyl sulfate, for example, is an unsaturated alkyl sulfate. Unsaturated alkyl sulfates such as oleyl sulfate can be relatively expensive and/or relatively incompatible with detergent formulations, especially those containing bleach. In addition to the above structural variations, complex, highly branched primary alkyl sulfate mixtures having quaternary carbon atoms in the hydrophobe are producible, for example by sulfation of Oxo alcohol made via acid-catalyzed polygas reaction; moreover stereoisomerism, possible in many branched alkyl sulfates, further multiplies the number of species; and commercial alkyl sulfates can contain impurities including the corresponding alcohols, inorganic salts such as sodium sulfate, hydrocarbons, and cyclic byproducts of their synthesis. One known material is sodium isostearyl sulfate which is a mixture of methyl and/or ethyl branches distributed along an otherwise linear alkyl backbone wherein the total number of carbons in the entire molecule are about 18. This isostearyl "mixture" is prepared in low yield from natural source feedstocks (i.e. tall oil, soy, etc.) via a process which results in branching which occurs in an uncontrolled manner, and which can vary depending upon the source of the feedstock. EP 401,462, assigned to Henkel, published Dec. 12, 1990 describes certain isostearyl alcohols and ethoxylated isostearyl alcohols and their sulfation to produce the corresponding alkyl sulfates such as "sodium isostearyl sulfate" (CAS 34481-82-8, sometimes referred to as "sodium isooctadecyl sulfate"). Again, while R. G. Laughlin in "The Aqueous Phase Behavior of Surfactants", Academic Press, New York (1994) p. 347 describes the observation that as branching moves away from the 2-alkyl position towards the center of the alkyl hydrophobe there is a lowering of Krafft temperatures (for a 15% solution), such solubility observations teach nothing about the surfactancy of these compounds or their utility for incorporation into detergent compositions. In fact, both commercial practice and the published literature are equivocal on the desirability of branching in the mid-chain region. This includes the above-noted patent publications describing the beta-branched alkyl sulfates as the desired branching, as well as Finger et al., "Detergent alcohols--the effect of alcohol structure and molecular weight on surfactant properties", J. Amer. Oil Chemists' Society, Vol. 44, p. 525 (1967) or Technical Bulletin, Shell Chemical Co., South Carolina: 364-80. These references assert, with respect to deleterious structural changes possible in alcohol sulfates that "moving a CH3 has a small effect". Data presented in a table shows a decrease in cotton detergency of 29% and a decrease in foaming of 77% relative to unbranched primary alcohol sulfate at the C13 chainlength. Moreover JP 721232 describes a detergency negative for the replacement of C11 linear primary alkyl sulfate with branched primary alkyl sulfate of unspecified branching. In addition, K. R. Wormuth and S. Zushma, Langmuir, Vol. 7, (1991), pp 2048-2053 describes technical studies on a number of branched alkyl sulfates, especially the "branched Guerbet" type, derived from the highly branched "Exxal" alcohols made by Exxon. Phase studies establish a lipophile ranking, that is a hydrophobe ranking, as follows: highly branched.apprxeq.double tail>methyl branched> linear. Assertedly, branched surfactants mix oil and water less effectively than linear surfactants. The efficiency ranking is linear>double tail>>methyl branched.apprxeq.highly branched. From these results, it is not immediately evident which direction to take in the development of further improvements in branched alkyl sulfates. Thus, going beyond simple technical theories of how to achieve cleaning superiority of one pure surfactant compound versus another, the developer and formulator of surfactants for laundry detergents must consider a wide variety of possibilities with limited (sometimes inconsistent) information, and then strive to provide overall improvements in one or more of a whole array of criteria, including performance in the presence of complex mixtures of surfactants, trends to low wash temperatures, formulation changes including builders, enzymes and bleaches, various changes in consumer habits and practices, and the need for biodegradability. In the context provided by these preliminary remarks, the development of improved alkyl sulfates for use in laundry detergents and cleaning products is clearly a complex challenge. The present invention relates to improvements in such alkyl sulfate surfactant compositions. As will be seen from the disclosures hereinafter, it has now unexpectedly been determined that certain relatively long-chain alkyl sulfate compositions containing mid-chain branching are preferred for use in laundry products, especially under cool or cold water washing conditions (e.g., 20.degree. C.-5.degree. C.). Preferred are the combination of two or more of these mid-chain branched primary alkyl sulfate surfactants which provide a surfactant mixture that is higher in surfactancy and has better low temperature water solubility than any single branched alkyl sulfate. The mixtures as produced comprise the mid-chain branching desirable for use in the surfactant mixtures of the present invention or the surfactant mixtures disclosed herein can be formulated by mixing the desired amounts of individual mid-chain branched surfactants. Such superior mixtures are not limited to combinations with other mid-chain branched surfactants but (preferably) they can be suitably combined with one or more other traditional detergent surfactants (e.g., other primary alkyl sulfates; linear alkyl benzene sulfonates; alkyl ethoxylated sulfates; nonionic surfactants; etc.) to provide improved surfactant systems. These mid-chain branched surfactants are obtainable in relatively high purity making their commercialization cost effective for the formulator. Suitable product mixtures can be obtained from processes which utilize fossil-fuel sources. (The terms "derived from fossil fuels" or "fossil-fuel derived" herein are used to distinguish coal, natural gas, petroleum oil and other petrochemical derived, "synthetic" surfactants from those derived from living natural resources such as livestock or plants such as coconut palms). One such process is designed to provide branched reaction products which are primarily (85%, or greater) alpha-olefins, and which are then converted into hydrophobes in an Oxo-reaction sequence. Such branched alpha-olefins contain from about 11 to about 18 (avg.) total carbon atoms and comprise a linear chain having an average length in the 10-18 region. The branching is predominantly mono-methyl, but some di-methyl and some ethyl branching may occur. Advantageously, such process results in little (1%, or less) geminal branching, i.e., little, if any, "quaternary" carbon substitution. Moreover, little (less than about 20%) vicinal branching occurs. Of course, some (ca. 20%) of the overall feedstock used in the subsequent Oxo-process may remain unbranched. Typically, and preferably from the standpoint of cleaning performance and biodegradability, this process provides alpha-olefins with: an average number of branches (longest chain basis) in the 0.4-2.5 range; of the branched material, there are essentially no branches on carbons 1, 2 or on the terminal (omega) carbon of the longest chain of the branched material. Following the formation and purification of the branched-chain alpha-olefin, the feedstock is subjected to an Oxo carbonylation process. In this Oxo-step, a catalyst (e.g., conventional cobalt carbonyl) which does not move the double bond from its initial position is used. This avoids the formation of vinylidene intermediates (which ultimately yield less favorable surfactants) and allows the carbonylation to proceed at the #1 and #2 carbon atoms. It is therefore an object of the present invention to provide mid-chain branched primary alkyl sulfate surfactants with greater than 14.5 carbon atoms useful in cleaning compositions. It is also an object of the present invention to provide mixtures of the mid-chain branched primary alkyl surfactants which are formulatable with other surfactants to provide cleaning compositions having one or more advantages, including greater surfactancy at low use temperatures, increased resistance to water hardness, greater efficacy in surfactant systems, improved removal of greasy or body soils from fabrics, improved compatibility with detergent enzymes, and the like. BACKGROUND ART U.S. Pat. No. 3,480,556 to deWitt, et al., Nov. 25, 1969, EP 439,316, published by Lever Jul. 31, 1991, and EP 684,300, published by Lever Nov. 29, 1995, describe beta-branched alkyl sulfates. EP 439,316 describes certain laundry detergents containing a specific commercial C14/C15 branched primary alkyl sulfate, namely LIAL 145 sulfate. This is believed to have 61% branching in the 2-position; 30% of this involves branching with a hydrocarbon chain having four or more carbon atoms. U.S. Pat. No. 3,480,556 describes mixtures of from 10 to 90 parts of a straight chain primary alkyl sulfate and from 90 to 10 parts of a beta branched (2-position branched) primary alcohol sulfate of formula: ##STR4## wherein the total number of carbon atoms ranges from 12 to 20 and R1 is a straight chain alkyl radical containing 9 to 17 carbon atoms and R2 is a straight chain alkyl radical containing 1 to 9 carbon atoms (67% 2-methyl and 33% 2-ethyl branching is exemplified). As noted hereinbefore, R. G. Laughlin in "The Aqueous Phase Behavior of Surfactants", Academic Press, New York (1994) p. 347 describes the observation that as branching moves away from the 2-alkyl position towards the center of the alkyl hydrophobe there is a lowering of Krafft temperatures. See also Finger et al., "Detergent alcohols--the effect of alcohol structure and molecular weight on surfactant properties", J. Amer. Oil Chemists' Society, Vol. 44, p. 525 (1967) and Technical Bulletin, Shell Chemical Co., South Carolina: 364-80. EP 342,917 A, Unilever, published Nov. 23, 1989 describes laundry detergents containing a surfactant system in which the major anionic surfactant is an alkyl sulfate having an assertedly "wide range" of alkyl chain lengths (the experimental appears to involve mixing coconut and tallow chain length surfactants). U.S. Pat. No. 4,102,823 and GB 1,399,966 describe other laundry compositions containing conventional alkyl sulfates. G.B. Patent 1,299,966, Matheson et al., published Jul. 2, 1975, discloses a detergent composition in which the surfactant system is comprised of a mixture of sodium tallow alkyl sulfate and nonionic surfactants. Methyl-substituted sulfates include the known "isostearyl" sulfates; these are typically mixtures of isomeric sulfates having a total of 18 carbon atoms. For example, EP 401,462 A, assigned to Henkel, published Dec. 12, 1990, describes certain isostearyl alcohols and ethoxylated isostearyl alcohols and their sulfation to produce the corresponding alkyl sulfates such as sodium isostearyl sulfate. See also K. R. Wormuth and S. Zushma, Langmuir, Vol. 7, (1991), pp 2048-2053 (technical studies on a number of branched alkyl sulfates, especially the "branched Guerbet" type); R. Varadaraj et al., J. Phys. Chem., Vol. 95, (1991), pp 1671-1676 (which describes the surface tensions of a variety of "linear Guerbet" and "branched Guerbet"--class surfactants including alkyl sulfates); Varadaraj et al., J. Colloid and Interface Sci., Vol. 140, (1990), pp 31-34 (relating to foaming data for surfactants which include C12 and C13 alkyl sulfates containing 3 and 4 methyl branches, respectively); and Varadaraj et al., Langmuir, Vol. 6 (1990), pp 1376-1378 (which describes the micropolarity of aqueous micellar solutions of surfactants including branched alkyl sulfates). "Linear Guerbet" alcohols are available from Henkel, e.g., EUTANOL G-16. Primary akyl sulfates derived from alcohols made by Oxo reaction on propylene or n-butylene oligomers are described in U.S. Pat. No. 5,245,072 assigned to Mobil Corp. See also: U.S. Pat. No. 5,284,989, assigned to Mobil Oil Corp. (a method for producing substantially linear hydrocarbons by oligomerizing a lower olefin at elevated temperatures with constrained intermediate pore siliceous acidic zeolite), and U.S. Pat. Nos. 5,026,933 and 4,870,038, both to Mobil Oil Corp. (a process for producing substantially linear hydrocarbons by oligomerizing a lower olefin at elevated temperatures with siliceous acidic ZSM-23 zeolite). See also: Surfactant Science Series, Marcel Dekker, New York (various volumes include those entitled "Anionic Surfactants" and "Surfactant Biodegradation", the latter by R. D. Swisher, Second Edition, publ. 1987 as Vol. 18; see especially p.20-24 "Hydrophobic groups and their sources"; pp 28-29 "Alcohols", pp 34-35 "Primary Alkyl Sulfates" and pp 35-36 "Secondary Alkyl Sulfates"); and literature on "higher" or "detergent" alcohols from which alkyl sulfates are typically made, including: CEH Marketing Research Report "Detergent Alcohols" by R. F. Modler et al., Chemical Economics Handbook, 1993, 609.5000-609.5002; Kirk Othmer's Encyclopedia of Chemical Technology, 4th Edition, Wiley, New York, 1991, "Alcohols, Higher Aliphatic" in Vol. 1, pp 865-913 and references therein. SUMMARY OF THE INVENTION The present invention relates to surfactant compositions comprising from about 0.001% to about 100% of a mixture of two or more mid-chain branched primary alkyl sulfates having the formula: ##STR5## wherein the total number of carbon atoms in the branched primary alkyl moiety of this formula (including the R, R.sup.1, and R.sup.2 branching) is from 14 to 20, and wherein further for this surfactant mixture the average total number of carbon atoms in the branched primary alkyl moieties having the above formula is within the range of greater than 14.5 to about 17.5 (preferably from about 15 to about 17); R, R.sup.1, and R.sup.2 are each independently selected from hydrogen and C.sub.1 -C.sub.3 alkyl (preferably methyl), provided R, R.sup.1, and R.sup.2 are not all hydrogen and, when z is 1, at least R or R.sup.1 is not hydrogen; M is one or more cations; w is an integer from 0 to 13; x is an integer from 0 to 13; y is an integer from 0 to 13; z is an integer of at least 1; and w+x+y+z is from 8 to 14. Preferably less than about 80% of the alkyl sulfates have a total of 18 carbon atoms in the alkyl chain. The present invention preferably further encompasses a detergent composition, for example one useful for laundering fabrics, comprising: (a) from about 0.001% to about 99% of a mixture of mid-chain branched primary alkyl sulfate surfactants, said mixture comprising at least about 5% by weight of two or more mid-chain branched alkyl sulfates having the formula: ##STR6## or mixtures thereof; wherein M represents one or more cations; a, b, d, and e are integers, a+b is from 10 to 16, d+e is from 8 to 14 and wherein further when a+b=10, a is an integer from 2 to 9 and b is an integer from 1 to 8; when a+b=11, a is an integer from 2 to 10 and b is an integer from 1 to 9; when a+b=12, a is an integer from 2 to 11 and b is an integer from 1 to 10; when a+b=13, a is an integer from 2 to 12 and b is an integer from 1 to 11; when a+b=14, a is an integer from 2 to 13 and b is an integer from 1 to 12; when a+b=15, a is an integer from 2 to 14 and b is an integer from 1 to 13; when a+b=16, a is an integer from 2 to 15 and b is an integer from 1 to 14; when d+e=8, d is an integer from 2 to 7 and e is an integer from 1 to 6; when d+e=9, d is an integer from 2 to 8 and e is an integer from 1 to 7; when d+e=10, d is an integer from 2 to 9 and e is an integer from 1 to 8; when d+e=11, d is an integer from 2 to 10 and e is an integer from 1 to 9; when d+e=12, d is an integer from 2 to 11 and e is an integer from 1 to 10; when d+e=13, d is an integer from 2 to 12 and e is an integer from 1 to 11; when d+e=14, d is an integer from 2 to 13 and e is an integer from 1 to 12; wherein for this surfactant mixture the average total number of carbon atoms in the branched primary alkyl moieties having the above formulas is within the range of greater than 14.5 to about 17.5; and (b) from about 1% to about 99.999% of detergent composition adjuct ingredients. It is also an object of the present invention to provide novel mid-chain branched primary alkyl surfactants for use in the surfactant mixtures described herein. The invention therefore also preferably relates to novel alkyl sulfate compounds of formula: ##STR7## wherein: a and b are integers and a+b is 12 or 13, a is an integer from 2 to 11, b is an integer from 1 to 10 and M is selected from sodium, potassium, ammonium and substituted ammonium. More preferred embodiments of such compounds include an alkyl sulfate compound of said formula wherein M is selected from sodium, potassium and ammonium. Also preferred herein are alkyl sulfate compounds of formula: ##STR8## wherein: d and e are integers and d+e is from 10 or 11; and wherein further when d+e=10, d is an integer from 2 to 9 and e is an integer from 1 to 8; when d+e=11, d is an integer from 2 to 10 and e is an integer from 1 to 9; and M is selected from sodium, potassium, ammonium and substituted ammonium, more preferably sodium, potassium and ammonium, most preferably sodium. All percentages, ratios and proportions herein are by weight, unless otherwise specified. All temperatures are in degrees Celsius (.degree. C.) unless otherwise specified. All documents cited are in relevant part, incorporated herein by reference. DETAILED DESCRIPTION OF THE INVENTION The present invention relates to surfactant mixtures comprising branched alkyl sulfate surfactants. The branched surfactant compositions comprise two or more mid-chain branched primary alkyl sulfate surfactants having the formula ##STR9## The surfactant mixtures of the present invention comprise molecules having a linear primary alkyl sulfate chain backbone (i.e., the longest linear carbon chain which includes the sulfated carbon atom). These alkyl chain backbones comprise from 12 to 19 carbon atoms; and further the molecules comprise a branched primary alkyl moiety having at least a total of 14, but not more than 20, carbon atoms. In addition, the surfactant mixture has an average total number of carbon atoms for the branched primary alkyl moieties within the range of from greater than 14.5 to about 17.5. Thus, the present invention mixtures comprise at least one branched primary alkyl sulfate surfactant compound having a longest linear carbon chain of not less than 12 carbon atoms or more than 19 carbon atoms, and the total number of carbon atoms including branching must be at least 14, and further the average total number of carbon atoms for the branched primary alkyl chains is within the range of greater than 14.5 to about 17.5. For example, a C16 total carbon primary alkyl sulfate surfactant having 13 carbon atoms in the backbone must have 1, 2, or 3 branching units (i.e., R, R.sup.1 and/or R.sup.3) whereby total number of carbon atoms in the molecule is at least 16. In this example, the C16 total carbon requirement may be satisfied equally by having, for example, one propyl branching unit or three methyl branching units. R, R.sup.1, and R.sup.2 are each independently selected from hydrogen and C.sub.1 -C.sub.3 alkyl (preferably hydrogen or C.sub.1 -C.sub.2 alkyl, more preferably hydrogen or methyl, and most preferably methyl), provided R, R.sup.1, and R.sup.2 are not all hydrogen. Further, when z is 1, at least R or R.sup.1 is not hydrogen. Although for the purposes of the present invention surfactant compositions the above formula does not include molecules wherein the units R, R.sup.1, and R.sup.2 are all hydrogen (i.e., linear non-branched primary alkyl sulfates), it is to be recognized that the present invention compositions may still further comprise some amount of linear, non-branched primary alkyl sulfate. Further, this linear non-branched primary alkyl sulfate surfactant may be present as the result of the process used to manufacture the surfactant mixture having the requisite one or more mid-chain branched primary alkyl sulfates according to the present invention, or for purposes of formulating detergent compositions some amount of linear non-branched primary alkyl sulfate may be admixed into the final product formulation. Further it is to be similarly recognized that non-sulfated mid-chain branched alcohol may comprise some amount of the present invention compositions. Such materials may be present as the result of incomplete sulfation of the alcohol used to prepare the alkyl sulfate surfactant, or these alcohols may be separately added to the present invention detergent compositions along with a mid-chain branched alkyl sulfate surfactant according to the present invention. M is hydrogen or a salt forming cation depending upon the method of synthesis. Examples of salt forming cations are lithium, sodium, potassium, calcium, magnesium, quaternary alkyl amines having the formula ##STR10## wherein R.sup.3, R.sup.4, R.sup.5 and R.sup.6 are independently hydrogen, C.sub.1 -C.sub.22 alkylene, C.sub.4 -C.sub.22 branched alkylene, C.sub.1 -C.sub.6 alkanol, C.sub.1 -C.sub.22 alkenylene, C.sub.4 -C.sub.22 branched alkenylene, and mixtures thereof. Preferred cations are ammonium (R.sup.3, R.sup.4, R.sup.5 and R.sup.6 equal hydrogen), sodium, potassium, mono-, di-, and trialkanol ammonium, and mixtures thereof. The monoalkanol ammonium compounds of the present invention have R.sup.3 equal to C.sub.1 -C.sub.6 alkanol, R.sup.4, R.sup.5 and R.sup.6 equal to hydrogen; dialkanol ammonium compounds of the present invention have R.sup.3 and R.sup.4 equal to C.sub.1 14 C.sub.6 alkanol, R.sup.5 and R.sup.6 equal to hydrogen; trialkanol ammonium compounds of the present invention have R.sup.3, R.sup.4 and R.sup.5 equal to C.sub.1 -C.sub.6 alkanol, R.sup.6 equal to hydrogen. Preferred alkanol ammonium salts of the present invention are the mono-, di- and tri- quaternary ammonium compounds having the formulas: H.sub.3 N.sup.+ CH.sub.2 CH.sub.2 OH, H.sub.2 N.sup.+ (CH.sub.2 CH.sub.2 OH).sub.2, HN.sup.+ (CH.sub.2 CH.sub.2 OH).sub.3. Preferred M is sodium, potassium and the C.sub.2 alkanol ammonium salts listed above; most preferred is sodium. Further regarding the above formula, w is an integer from 0 to 13; x is an integer from 0 to 13; y is an integer from 0 to 13; z is an integer of at least 1; and w+x+y+z is an integer from 8 to 14. Certain points of branching (i.e., the location along the chain of the R, R.sup.1, and/or R.sup.2 moieties in the above formula) are preferred over other points of branching along the backbone of the surfactant. The formula below illustrates the mid-chain branching range (i.e., where points of branching occur), preferred mid-chain branching range, and more preferred mid-chain branching range for mono-methyl substituted linear alkyl sulfates of the present invention. ##STR11## It should be noted that for the mono-methyl substituted surfactants these ranges exclude the two terminal carbon atoms of the chain and the two carbon atoms immediately adjacent to the sulfate group. For surfactant mixtures comprising two or more of R, R.sup.1, or R.sup.2, alkyl branching at the 2-carbon atom is within the scope of the present invention. Surfactants having chains longer than ethyl (i.e. C.sub.3 alkyl substitutents) on the 2-carbon atom, however, are less preferred. The formula below illustrates the mid-chain branching range, preferred mid-chain branching range, and more preferred mid-chain branching range for di-methyl substituted linear alkyl sulfates of the present invention. ##STR12## When di-alkyl substituted primary alkyl sulfates are combined with mono-substituted mid-chain branched primary alkyl sulfates, the di-alkyl substituted primary alkyl sulfates having one methyl substitution on the 2-carbon position and another methyl substitution in the preferred range as indicated above, are within the present invention. The preferred surfactant mixtures of the present invention have at least 0.001%, more preferably at least 5%, most preferably at least 20% by weight, of the mixture one or more branched primary alkyl sulfates having the formula ##STR13## wherein the total number of carbon atoms, including branching, is from 15 to 18, and wherein further for this surfactant mixture the average total number of carbon atoms in the branched primary alkyl moieties having the above formula is within the range of greater than 14.5 to about 17.5; R.sup.1 and R.sup.2 are each independently hydrogen or C.sub.1 -C.sub.3 alkyl; M is a water soluble cation; x is from 0 to 11; y is from 0 to 11; z is at least 2; and x+y+z is from 9 to 13; provided R.sup.1 and R.sup.2 are not both hydrogen. More preferred are compositions having at least 5% of the mixture comprising one or more mid-chain branched primary alkyl sulfates wherein x+y is equal to 9 and z is at least 2. Preferably, the mixtures of surfactant comprise at least 5% of a mid chain branched primary alkyl sulfate having R.sup.1 and R.sup.2 independently hydrogen, methyl, provided R.sup.1 and R.sup.2 are not both hydrogen; x+y is equal to 8, 9, or 10 and z is at least 2. More preferably the mixtures of surfactant comprise at least 20% of a mid chain branched primary alkyl sulfate having R.sup.1 and R.sup.2 independently hydrogen, methyl, provided R.sup.1 and R.sup.2 are not both hydrogen; x+y is equal to 8,9, or 10 and z is at least 2. Preferred detergent compositions according to the present invention, for example one useful for laundering fabrics, comprise from about 0.001% to about 99% of a mixture of mid-chain branched primary alkyl sulfate surfactants, said mixture comprising at least about 5% by weight of two or more mid-chain branched alkyl sulfates having the formula: ##STR14## or mixtures thereof; wherein M represents one or more cations; a, b, d, and e are integers, a+b is from 10 to 16, d+e is from 8 to 14 and wherein further when a+b=10, a is an integer from 2 to 9 and b is an integer from 1 to 8; when a+b=11, a is an integer from 2 to 10 and b is an integer from 1 to 9; when a+b=12, a is an integer from 2 to 11 and b is an integer from 1 to 10; when a+b=13, a is an integer from 2 to 12 and b is an integer from 1 to 11; when a+b=14, a is an integer from 2 to 13 and b is an integer from 1 to 12; when a+b=15, a is an integer from 2 to 14 and b is an integer from 1 to 13; when a+b=16, a is an integer from 2 to 15 and b is an integer from 1 to 14; when d+e=8, d is an integer from 2 to 7 and e is an integer from 1 to 6; when d+e=9, d is an integer from 2 to 8 and e is an integer from 1 to 7; when d+e=10, d is an integer from 2 to 9 and e is an integer from 1 to 8; when d+e=11, d is an integer from 2 to 10 and e is an integer from 1 to 9; when d+e=12, d is an integer from 2 to 11 and e is an integer from 1 to 10; when d+e=13, d is an integer from 2 to 12 and e is an integer from 1 to 11; when d+e=14, d is an integer from 2 to 13 and e is an integer from 1 to 12; wherein further for this surfactant mixture the average total number of carbon atoms in the branched primary alkyl moieties having the above formulas is within the range of greater than 14.5 to about 17.5. Further, the present invention surfactant composition may comprise a mixture of branched primary alkyl sulfates having the formula ##STR15## wherein the total number of carbon atoms per molecule, including branching, is from 14 to 20, and wherein further for this surfactant mixture the average total number of carbon atoms in the branched primary alkyl moieties having the above formula is within the range of greater than 14.5 to about 17.5; R, R.sup.1, and R.sup.2 are each independently selected from hydrogen and C.sub.1 14 C.sub.3 alkyl, provided R, R.sup.1, and R.sup.2 are not all hydrogen; M is a water soluble cation; w is an integer from 0 to 13; x is an integer from 0 to 13; y is an integer from 0 to 13; z is an integer of at least 1; and w+x+y+z is from 8 to 14; provided that when R.sup.2 is a C.sub.1 -C.sub.3 alkyl the ratio of surfactants having z equal to 1 to surfactants having z of 2 or greater is at least about 1:1, preferably at least about 1:5, more preferably at least about 1:10, and most preferably at least about 1:100. Also preferred are surfactant compositions, when R.sup.2 is a C.sub.1 -C.sub.3 alkyl, comprising less than about 20%, preferably less than 10%, more preferably less than 5%, most preferably less than 1%, of branched primary alkyl sulfates having the above formula wherein z equals 1. The present invention further relates to novel branched primary alkyl sulfate surfactants having the formula ##STR16## wherein R.sup.1 and R.sup.2 are each independently hydrogen or C.sub.1 -C.sub.3 alkyl; M is a water soluble cation; x is an integer from 0 to 12; y is an integer from 0 to 12; z is an integer of at least 2; and x+y+z is from 11 to 14; provided: a) R.sup.1 and R.sup.2 are not both hydrogen; b) when one R.sup.1 or R.sup.2 is hydrogen and the other R.sup.1 or R.sup.2 is methyl, then x+y+z is not 12 or 13; and c) when R.sup.1 is hydrogen and R.sup.2 is methyl, x+y is not 11 when z is 3, and x+y is not 9 when z is 5. R.sup.1 and R.sup.2 units are selected independently from hydrogen or C.sub.1 -C.sub.3 alkyl (preferably hydrogen or C.sub.1 -C.sub.2 alkyl; more preferably hydrogen or methyl) provided R and R.sup.1 are not both hydrogen. M is as defined hereinbefore. For mid-chain branched primary alkyl sulfates of the present invention having more than one alkyl branch chain, the alkyl chain backbones comprise from 12 to 18 carbon atoms. The maximum number of carbons that comprise the mid-chain branched primary alkyl sulfates of the present invention, including all branches, is 20 carbon atoms. Preferred novel mid-chain branched primary alkyl sulfate compounds have the formula: ##STR17## wherein: a and b are integers and a+b is 12 or 13, a is an integer from 2 to 11, b is an integer from 1 to 10 and M is selected from sodium, potassium, ammonium and substituted ammonium. More preferred embodiments of such compounds include an alkyl sulfate compound of said formula wherein M is selected from sodium, potassium and ammonium. Also preferred novel mid-chain branched primary alkyl sulfate compounds have the formula: ##STR18## wherein: d and e are integers and d+e is 10 or 11; and wherein further when d+e=10, d is an integer from 2 to 9 and e is an integer from 1 to 8; when d+e=11, d is an integer from 2 to 10 and e is an integer from 1 to 9; and M is selected from sodium, potassium, ammonium and substituted ammonium, more preferably sodium, potassium and ammonium, most preferably sodium. Preferred mono-methyl branched primary alkyl sulfates are selected from the group consisting of: 3-methyl pentadecanol sulfate, 4-methyl pentadecanol sulfate, 5-methyl pentadecanol sulfate, 6-methyl pentadecanol sulfate, 7-methyl pentadecanol sulfate, 8-methyl pentadecanol sulfate, 9-methyl pentadecanol sulfate, 10-methyl pentadecanol sulfate, 11-methyl pentadecanol sulfate, 12-methyl pentadecanol sulfate, 13-methyl pentadecanol sulfate, 3-methyl hexadecanol sulfate, 4-methyl hexadecanol sulfate, 5-methyl hexadecanol sulfate, 6-methyl hexadecanol sulfate, 7-methyl hexadecanol sulfate, 8-methyl hexadecanol sulfate, 9-methyl hexadecanol sulfate, 10-methyl hexadecanol sulfate, 11-methyl hexadecanol sulfate, 12-methyl hexadecanol sulfate, 13-methyl hexadecanol sulfate, 14-methyl hexadecanol sulfate, and mixtures thereof. Preferred di-methyl branched primary alkyl sulfates are selected from the group consisting of: 2,3-methyl tetradecanol sulfate, 2,4-methyl tetradecanol sulfate, 2,5-methyl tetradecanol sulfate, 2,6-methyl tetradecanol sulfate, 2,7-methyl tetradecanol sulfate, 2,8-methyl tetradecanol sulfate, 2,9-methyl tetradecanol sulfate, 2,10-methyl tetradecanol sulfate, 2,11-methyl tetradecanol sulfate, 2,12-methyl tetradecanol sulfate, 2,3-methyl pentadecanol sulfate, 2,4-methyl pentadecanol sulfate, 2,5-methyl pentadecanol sulfate, 2,6-methyl pentadecanol sulfate, 2,7-methyl pentadecanol sulfate, 2,8-methyl pentadecanol sulfate, 2,9-methyl pentadecanol sulfate, 2,10-methyl pentadecanol sulfate, 2,11-methyl pentadecanol sulfate, 2,12-methyl pentadecanol sulfate, 2,13-methyl pentadecanol sulfate, and mixtures thereof. The following branched primary alkyl sulfates comprising 16 carbon atoms and having one branching unit are examples of preferred branched surfactants useful in the present invention compositions: ##STR19## wherein M is preferably sodium. The following branched primary alkyl sulfates comprising 17 carbon atoms and having two branching units are examples of preferred branched surfactants according to the present invention: 2,5-dimethylpentadecylsulfate having the formula: ##STR20## wherein M is preferably sodium. Preparation of Mid-Chain Branched Alkyl Sulfates The following reaction scheme outlines a general approach to the preparation of mid-chain branched primary alkyl sulfates of the present invention. ##STR21## An alkyl halide is converted to a Grignard reagent and the Grignard is reacted with a haloketone. After conventional acid hydrolysis, acetylation and thermal elimination of acetic acid, an intermediate olefin is produced (not shown in the scheme) which is hydrogenated forthwith using any convenient hydrogenation catalyst such as Pd/C. This route is favorable over others in that the branch, in this illustration a 5-methyl branch, is introduced early in the reaction sequence. Formylation of the alkyl halide resulting from the first hydrogenation step yields alcohol product, as shown in the scheme. This can be sulfated using any convenient sulfating agent, e.g., chlorosulfonic acid, SO3/air, or oleum, to yield the final branched primary alkyl sulfate surfactant. There is flexibility to extend the branching one additional carbon beyond that which is achieved by a single formylation. Such extension can, for example, be accomplished by reaction with ethylene oxide. See "Grignard Reactions of Nonmetallic Substances", M. S. Kharasch and O. Reinmuth, Prentice-Hall, New York, 1954; J. Org. Chem., J. Cason and W. R. Winans, Vol. 15 (1950), pp 139-147; J. Org Chem., J. Cason et al., Vol. 13 (1948), pp 239-248; J. Org Chem., J. Cason et al., Vol. 14 (1949), pp 147-154; and J. Org Chem., J. Cason et al., Vol. 15 (1950), pp 135-138 all of which are incorporated herein by reference. In variations of the above procedure, alternate haloketones or Grignard reagents may be used. PBr3 halogenation of the alcohol from formylation or ethoxylation can be used to accomplish an iterative chain extension. The preferred mid-chained branched primary alkyl sulfates of the present invention can also be readily prepared as follows: ##STR22## A conventional bromoalcohol is reacted with triphenylphosphine followed by sodium hydride, suitably in dimethylsulfoxide/tetrahydrofuran, to form a Wittig adduct. The Wittig adduct is reacted with an alpha methyl ketone, forming an internally unsaturated methyl-branched alcoholate. Hydrogenation followed by sulfation yields the desired mid-chain branched primary alkyl sulfate. Although the Wittig approach does not allow the practitioner to extend the hydrocarbon chain, as in the Grignard sequence, the Wittig typically affords higher yields. See Agricultural and Biological Chemistry, M. Horiike et al., vol. 42 (1978), pp 1963-1965 included herein by reference. Any alternative synthetic procedure in accordance with the invention may be used to prepare the branched primary alkyl sulfates. The mid-chain branched primary alkyl sulfates may, in addition be synthesized or formulated in the presence of the conventional homologs, for example any of those which may be formed in an industrial process which produces 2-alkyl branching as a result of hydroformylation. Mid-chain branched surfactant mixtures of the present invention are routinely added to other known commercial alkyl sulfates contained in the final laundry product formulation. In certain preferred embodiments of the surfactant mixtures of the present invention, especially those derived from fossil fuel sources involving commercial processes, comprise at least 1 mid-chain branched primary alkyl sulfate, preferably at least 2, more preferably at least 5, most preferably at least 8. Particularly suitable for preparation of certain surfactant mixtures of the present invention are "oxo" reactions wherein a branched chain olefin is subjected to catalytic isomerization and hydroformylation prior to sulfation. The preferred processes resulting in such mixtures utilize fossil fuels as the starting material feedstock. Preferred processes utilize Oxo reaction on linear olefins (alpha or internal) with a limited amount of branching. Suitable olefins may be made by dimerization of linear alpha or internal olefins, by controlled oligomerization of low molecular weight linear olefins, by skeletal rearrangement of detergent range olefins, by dehydrogenation/skeletal rearrangement of detergent range paraffins, or by Fischer-Tropsch reaction. These reactions will in general be controlled to: 1) give a large proportion of olefins in the desired detergent range (while allowing for the addition of a carbon atom in the subsequent Oxo reaction), 2) produce a limited number of branches, preferably mid-chain, 3) produce C.sub.1 -C.sub.3 branches, more preferably ethyl, most preferably methyl, 4) limit or eliminate gem dialkyl branching i.e. to avoid formation of quaternary carbon atoms. The suitable olefins can undergo Oxo reaction to give primary alcohols either directly or indirectly through the corresponding aldehydes. When an internal olefin is used, an Oxo catalyst is normally used which is capable of prior pre-isomerization of internal olefins primarily to alpha olefins. While a separately catalyzed (i.e. non-Oxo) internal to alpha isomerization could be effected, this is optional. On the other hand, if the olefin-forming step itself results directly in an alpha olefin (e.g. with high pressure Fischer-Tropsch olefins of detergent range), then use of a non-isomerizing Oxo catalyst is not only possible, but preferred. The scheme below summaries this process. ##STR23## The process described herein above gives the more preferred 5-methylhexadecyl sulfate in higher yield than the less preferred 2,4-dimethylpentadecyl sulfate. This mixture is desirable under the metes and bounds of the present invention in that each product comprises at total of 17 carbon atoms with linear alkyl chains having at least 13 carbon atoms. The following examples provide methods for synthesizing various compounds useful in the present invention compositions. |
| PATENT EXAMPLES | This data is not available for free |
| PATENT PHOTOCOPY | Available on request |
|
Want more information ? Interested in the hidden information ? Click here and do your request. |