United States Patent Office Patented Apr

3,438,959 United States Patent Office Patented Apr. 15, 1969 2 al pulping liquors which have been altered somewhat by 3,438,959 further processing or treatment such as an acid treatment, LGNOSULFONATE DERVATIVE AND A PROCESS FOR ITS PREPARATION alkaline treatment, heat treatment, oxidation with acids Chung Su Youn Kim, Belingham, Wash., assignor to as well as other oxidizing agents, and other treatments Georgia-Pacific Corporation, Portland, Oreg, a cor are operative as long as the lignin constituents retain poration of Georgia their basic phenylpropane polymeric structure to have No Drawing. Filed Oct. 1, 1965, Ser. No. 492,262 the general porperties and characteristics associated with Int. C. C07g 1/00; C11d 1/30 the lignin products. U.S. C. 260- 124 20 Cains In the separation of lignin from the lignocellulosic ma terials, other constituents besides lignin are generally ob O tained in the lignin-containing product. For example, ABSTRACT OF THE DISCLOSURE spent sulfite liquor generally contains about 40 to 60 The preparation of a halogenated lignosulfonate by weight percent of lignosulfonate with the remainder be the reaction of lignosulfonate with thionyl chloride or ing carbohydrates and other organic and inorganic ma thionyl bromide under substantially anhydrous conditions. terials dissolved in the liquor. Lignin products obtained by other processes will likewise contain other materials such as carbohydrates, degradation products of carbohy This invention relates to a derivative of lignosulfonate drates, and resinous materials which may remain after and particularly to a halogen containing derivative of sulfonation of the lignin products obtained by Such proc lignoSulfonate and a process for its preparation. esses. Most of the non-lignin constituents such as Sugars Lignin is a polymeric Substance found in plant and may not be detrimental but will result in the utilization vegetable tissue associated with cellulose and other plant of the thionyl halide by reacting with the reagent. Thus, constituents. In the pulp and paper industry, lignin-con generally the lignosulfonate constituents are separated taining materials such as wood, straw, corn Stalks, ba from the non-lignin products prior to reaction with the gasse, and other vegetable and plant tissues are processed acid halide. Lignin products such as a Sulfonated residual to recover the cellulose or pulp with lignin being obtained pulping liquor may be subjected to different treatments, as a by-product. Since vegetable and plant tissues can such as, for example, acid, alkaline or heat treatments contain up to about 30% lignin, large amounts of lignin as well as reaction with other chemicals or oxidation to are available. Considerable effort has been expended in remove or modify some of the non-lignin constituents or lignin research without too much success in the develop for other purposes. The lignin constituents may be af ment of methods or processes to utilize more fully the fected to a certain extent by such treatments but this is chemical values of lignin. Lignin and lignosulfonates not detrimental as long as the treatment is not so Severe have found only limited markets resulting in an appreci as to destroy the basic phenylpropane polymeric struc able amount of the pulping liquors having to be processed ture of the lignin and properties characteristic of these mainly for disposal purposes rather than for recovery of products. For example, a spent sulfite liquor may be oxi any chemical values. dized as in the preparation of vanillin. The vanillin raf It is therefore an object of this invention to provide finate obtained will generally contain lignosulfonates a process for the treatment of residual pulping liquors which may be altered somewhat but which still retain the or lignin so that the chemical value of the product can basic properties and characteristics associated with ligno be utilized. A further object is to provide a lignin deriva 40 sulfonates. It is generally preferred to recover the ligno tive product which is reactive and can be used as an in sulfonates from the lignin products by solvent extraction termediate in the formation of other chemical products. or by precipitation with an alkaline earth hydroxide, an The above and other objects are attained by interacting acid, or an amine. Other known methods, however, may sulfonated lignin with a thionyl halide selected from the also be used, some of which are ion exchange, dialysis group consisting of thionyl chloride and thionyl bromide. and electrodialysis. The interaction of the sulfonated lignin with the thionyl In addition to recovery of the lignosulfonates, the re halide will result in the formation of a halogen contain covered lignosulfonates may be further treated to reduce ing derivative which is reactive and may be reacted with the average molecular weight of the product. The igno other chemicals to form different products. For example, sulfonate having average molecular weights in the range the intermediate product may be interacted with an alco such that the diffusion coefficient is in the range of 14 to holate or a phenolate to form esters or with an amine 20 mm.2/day (as determined by the agar gel method de to form lignosulfonamides. scribed in J. Am. Chem. Soc. vol. 81, 2054 by J. Moacanin It is essential that the lignin be sulfonated prior to re et al.) result in the preparation of a more reactive inter action with the thionyl halide. In some of the pulping mediate product. If desired, the lignosulfonate product processes, for example, the sulfite pulping process, the may be fractionated to recover the low molecular weight residual pulping liquor is a sulfonated product containing fraction. However, it is generally preferred to treat the the lignin in a sulfonated form. In other processes, the lignosulfonate obtained to reduce the average molecular residual pulping liquor or the lignin-containing product weight. This may be done by using the various known as obtained from the process may not be a Sulfonated methods, for example, prehalogenation of the lignosulfo product. However, the residual liquors or products con 60 nate or resulfonation under conditions to obtain reduced taining the lignin portion may be sulfonated by various molecular weight. In the prehalogenation, halogen gases known methods to the degree desired by reaction, for Such as chlorine or bromine may be used or other halo example, with a bisulfite or sulfite, including further Sul genating agents employed which result in the formation of fonation of a sulfite pulping liquor. Residual pulping elemental bromine or chlorine under the treatment condi liquors obtained in the Kraft and other alkaline processes tions. In addition to just reducing the molecular weight, of digestion of lignocellulosic materials, “hydrolysis the prehalogenation results in halogenating the sulfonated lignin’ obtained by the hydrolysis of lignocellulosic ma ignin which has an advantageous effect in making the terials in the manufacture of wood Sugars, “hydrotropic product react more rapidly and efficiently with the thiony lignins' derived from hydrotropic pulping processes, or halide. Halogen Substitution on the aromatic groups of lignin obtained from any source may thus be sulfonated 70 the lignin is most likely obtained by the prehalogenation and used in the formation of the reactive halogenated resulting in the improved properties. ignosulfonate derivative. Also, lignoSulfonates or residu The reaction of the lignosulfonate with the thionyl 3,438,959 3. 4. halide is carried out in a non-aqueous medium preferably react with at least 50% of the sulfonate radicals present in under substantially anhydrous conditions and in a ne the lignosulfonate, preferably from at least about 80% dium in which the particular lignoSulfonate is soluble. to the stoichiometric amount to react with the Sulfonate Thionyl chloride is generally used in the reaction due to radicals. Since the ignosulfonates as recovered may con its availability. Thionyl chloride is a good solvent for tain moisture and other constituents, even though purified, many lignosulfonates and thus may be used also as a re 5 which may utilize some of the thionyl halide, a 10% to action medium. 20% stoichiometric excess or more is often used. With a It is not necessary that the conditions be absolutely large excess of the thionyl halide, such as when the thionyl anhydrous, since any water present will react with the halide is used as the reaction medium, additional halogen thionyl halide to form a hydrogen halide and Sulfur di substitution in the lignin molecules may be obtained, espe oxide until the system becomes Substantially anhydrous. cially at the higher reaction temperature. At reaction Preferably, the reaction is carried out under reflux so temperatures above 50° C. and with excess thionyl halide that the acids or any other gaseous reaction products will present, an increase in the halogen content and a decrease be expelled from the system. A low boiling solvent or me in the hydroxy content in the product are generally ob dium is generally preferred to permit the reaction mix 5 tained indicating that some halogen substitution of the ture to be refluxed at temperatures below the decomposi hydroxy groups may have taken place. tion point of the thionyl halide without having to employ The following examples further illustrate the invention reduced pressures. and the properties of the intermediate product obtained. The lignosulfonate must be at least partially soluble in the solvent to effect the reaction with the thionyl halide. : EXAMPLE I Since there are relatively few non-aqueous solvents, Such A lignosulfonate intermediate or derivative was as, for example, dimethyl sulfoxide, which will dissolve prepared from a fermented calcium base spent sulfite metal salts of lignosulfonate, the lignosulfonate is general liquor. The liquor was fermented to convert the ferment ly converted to the acid form of an annine salt for which able sugars to alcohol and stripped to recover the alco more readily available solvents such as dioxane, tetrahy 2 5 hol.

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