Opinion
Patent Appeal No. 75-612.
February 12, 1976.
Daniel S. Ortiz, atty. of record, Dobbs Ferry, N.Y., for appellants. Richard P. Fennelly, Paul J. Juettner, Dobbs Ferry, N Y, Lloyd L. Mahone, Westport, Conn., Charles B. Rodman, Dobbs Ferry, N.Y., Robert C. Sullivan, New York City, of counsel.
Joseph F. Nakamura, Washington, D.C., for the Commissioner of Patents. Fred W. Sherling, Washington, D.C., of counsel.
Appeal from the Board of Appeals of the United States Patent Office.
Before MARKEY, Chief Judge, and RICH, BALDWIN, LANE and MILLER, Associate Judges.
This appeal is from the decision of the Patent and Trademark Office Board of Appeals affirming the examiner's rejection of claims 1 and 3 to 6 in application serial No. 824,358, filed April 30, 1969, entitled "Methane Sulfonyl Chloride and Process of Preparation." We affirm in part and reverse in part.
The Invention
Appellants' invention comprises a continuous process for producing methane sulfonyl chloride by the simultaneous hydrolysis and chlorination of methyl mercaptan (methane thiol). Claim 1 is illustrative:
1. A continuous process for producing methane sulfonyl chloride comprising:
(a) maintaining a liquid bath consisting essentially of saturated aqueous hydrochloric acid with methane sulfonyl chloride dispersed therein at a temperature between about 30°C. and about 85°C.;
(b) continuously introducing gaseous methyl mercaptan, chlorine and a liquid consisting essentially of water or aqueous hydrogen chloride into said bath for reaction to produce methane sulfonyl chloride and hydrogen chloride;
(c) withdrawing gaseous material consisting essentially of hydrogen chloride formed by the reaction;
(d) withdrawing substantially continuously a portion of the liquid from said bath and isolating methane sulfonyl chloride therefrom.
Claim 3 is directed to a process carried out over a preferred temperature range from about 40°C. to about 75°C., and claims 4 to 6 are directed to variations in methods of handling the streams associated with operation of the process. Claims 3 to 6 are individually dependent upon claim 1.
Appellants stress that the present process is continuous and provides methane sulfonyl chloride in a high yield (92% of theoretical) and high purity (99%) when carried out in the claimed temperature range between about 30 to 85°C., preferably between about 40 to 75°C., in the presence of excess water (the "excess water" being the result of a maintained liquid bath of saturated aqueous hydrochloric acid).
The Prior Art
Gilbert, Sulfonation and Related Reactions, 202-08 (1965), discloses that thiols react with chlorine and water to form the corresponding sulfonyl chlorides and that cooling requirements for this reaction are "greatly" reduced when concentrated hydrochloric acid is employed as the reaction medium. The reference states that "[t]he sulfonyl chloride group is often susceptible to easy hydrolysis" and suggests various methods for dealing with this problem, including "conducting the reaction at a low temperature (i. e., 0-20°C)."
Gilbert is otherwise silent concerning temperature control. Also, Gilbert does not disclose the use of methane thiol as a reactant but does list a number of thiol (RSH) reactants among which is ethane thiol.
Park (United States Patent No. 2,772,307) discloses the preparation of ethylene sulfonyl chloride from divinyl disulfide, chlorine, and water at temperatures from as low as -100 to as high as 150°C., preferably "from about 0 to 40°C." Park teaches that the "yield will be decreased if the ethylene sulfonyl chloride is permitted to remain in contact with the by-products of the reaction for any substantial period of time." Furthermore, it is disclosed that ethylene sulfonyl chloride is sensitive to the presence of water and that "the sensitivity is much reduced at low temperatures." Example 1 discloses that when 60 parts of water are reacted with chlorine and 100 parts of divinyl disulfide in glacial acetic acid at ice bath temperatures, the yield is 80% of theoretical. Example 3 discloses that when 75 parts of water are reacted with chlorine and 100 parts of divinyl disulfide in glacial acetic acid at ice bath temperatures, the yield is 40% of theoretical.
Fusco et al. (G.B. Patent 801,037, hereinafter Fusco) discloses the preparation of sulfonyl chlorides by reacting chloric acid or a salt of chloric acid with a thiol or the corresponding disulfide in a 15 to 40% aqueous hydrochloric acid solution at an internal temperature between 5 to 30°C. All the specific examples are directed to preparation of the sulfonyl chlorides at temperatures of 15°C. or below. Furthermore, the reference states that the "operation should be carried out at such temperatures that the sulfonyl chloride is not subjected to appreciable hydrolysis by the water present in the reaction mixture."
Hougen, Chemical Process Principles, Part I, 222 (2d ed. 1959), discloses the removal of inert products which are formed during a reaction. There is also disclosed the coincident recycling of solvent in a closed system. Douglass et al., 60 J.Amer.Chem.Soc. 1486 (1938), is cited in Gilbert as reference 57 and discloses the preparation of various sulfonyl chlorides by chlorination of sulfur compounds in an aqueous medium. Each experimental run was carried out at a temperature below 20°C. Harris et al., 26 J.Org.Chem. 354 (1961), is cited in Gilbert as reference 90 and discloses that sulfonic acid may be prepared by chlorination of a thiol in the presence of excess water if the reaction mixture is not cooled.
The Rejection
Claims 1 and 3 to 6 were rejected by the examiner under 35 U.S.C. § 103 over Gilbert alone, Gilbert in view of Park and Fusco, and Gilbert in view of Park, Fusco, and further in view of Hougen. The board, in its decision, appears to have relied upon Gilbert, Park, and Fusco. The boards' position appears to be that 1) Gilbert suggests the conversion of mercaptans to their corresponding sulfonyl chlorides by reaction with chlorine gas in a concentrated hydrochloric acid medium, and 2) both Park and Fusco indicate that sulfonyl chlorides may be formed, and therefore would be presumed to be stable, at temperatures within appellants' claimed range.
The board was of the opinion that nothing in the art of record would lead one skilled in the art to believe that there would be any appreciable hydrolysis of the sulfonyl chloride within the claimed temperature range.
While the references set forth contain certain advantages for using the lower temperatures, one cannot reasonably conclude therefrom that there would be any appreciable hydrolysis in concentrated hydrochloric acid as suggested in Gilbert. While it is true that the references indicate instability at higher temperatures, such "higher temperatures" must be construed to be in the neighborhood of 150°C. Appellants attempt to support their argument of expected hydrolysis by referring to reference 90 in Gilbert wherein hydrolysis is said to occur by heating in aqueous suspension. Appellants, on page 4 of their reply brief, contend that as reference 90 (Harris et al) does not specify a temperature "one would be lead [sic] to believe that the reaction was done at room temperature"; such is not the case. On page 358, referred to by appellants, the chloride was distilled through a distillation column at 138° to 139°C.; this can hardly be construed to constitute room temperature nor can it be construed to suggest to one skilled in the art that sulfonyl chlorides would hydrolyze in concentrated hydrochloric acid at temperatures of 30° or 40°C., which temperatures are within the claimed range.
The claimed process is therefore not considered to constitute a sufficient departure from that disclosed in the art. While appellants may have determined optimum conditions for the production of methane sulfonyl chloride, the results they have obtained are not seen to be unexpected in light of the evidence presented in this record.
OPINION
At the outset, we note that the primary reference, Gilbert, teaches that sulfonyl chlorides may be hydrolyzed to the corresponding sulfonic acids by "heating." Gilbert also discloses that sulfonyl chlorides are often susceptible to "easy hydrolysis" and notes various methods for decreasing the extent of hydrolysis such as the use of hydrophobic solvents or theoretical amounts of water, or "conducting the reaction at a low temperature (i. e., 0-20°C.)."
Fusco also recognizes the susceptibility of sulfonyl chlorides to hydrolysis when he states that the reaction "should be carried out at such temperatures that the sulfonyl chloride is not subjected to appreciable hydrolysis by the water present in the reaction mixture." However, Fusco discloses a process for preparing sulfonyl chlorides in 15 to 40% hydrochloric acid at an internal temperature between 5 to 30°C., the latter being the lower limit of appellants' claimed temperature range.
We believe that it would have been obvious to one having ordinary skill in this art to employ the temperature range suggested by Fusco in the process described by Gilbert. Furthermore, we agree with the examiner and the board that there is nothing unobvious about the claimed process being continuous or the claimed methyl mercaptan starting material being a gas at the temperature and pressure conditions under which the claimed process is carried out.
We reject appellants' argument that the instant claims are allowable because similar claims have been allowed in a patent. It is immaterial whether similar claims have been allowed to others. See In re Margaroli, 50 CCPA 1400, 318 F.2d 348, 138 USPQ 158 (1963); In re Wright, 45 CCPA 1005, 256 F.2d 583, 118 USPQ 287 (1958); In re Launder, 41 CCPA 887, 212 F.2d 603, 101 USPQ 391 (1954).
Thus, we affirm the rejection of claims 1 and 4 to 6 under 35 U.S.C. § 103. However, the rejection of claim 3, which limits the reaction temperature to "from about 40°C to about 75°C," must be reversed. None of the references cited by the examiner or made of record by the appellants teaches or suggests that methane sulfonyl chloride may be prepared at temperatures between 40 to 75°C. in the presence of excess water. Park teaches that ethylene sulfonyl chloride may be prepared at temperatures up to 150°C. But Park does not encounter the hydrolysis problem since he requires the use of stoichiometric (i. e., substantially no excess) quantities of water. Park teaches that the "maximum yield of ethylene sulfonyl chloride will be obtained when divinyl disulfide is reacted with substantially 4 mols of water * * * per mol of divinyl disulfide" and that when "more or less than about 4 mols of water per mol of divinyl disulfide" are used, the "yield of ethylene sulfonyl chloride will * * * be lowered." Park does disclose a somewhat broader range of water that may be used (3.0 to 4.5 mols of water per mol of divinyl disulfide), but when slightly more water than that which is stoichiometrically necessary is employed, even at ice bath temperatures, the yield of sulfonyl chloride is decreased by 50% (see Examples I and III).
Thus Park has solved the hydrolysis problem by simply eliminating excess water from the reaction medium. Preparations which involve no excess water may be carried out at relatively high temperatures without encountering hydrolysis. Claim 3, however, is directed to a process for preparing methane sulfonyl chloride at temperatures of between 40 to 75°C. in the presence of excess water. Such a process is neither taught nor suggested by Park either alone or in combination with any other reference of record.
Accordingly, the rejection of claims 1 and 4 to 6 is affirmed and the rejection of claim 3 is reversed.
Modified.