US2541059A - Process for producing lignin products - Google Patents

Description

Mh, M, H951 c. c. HERITAGE ETAL PROCESS FOR PRODUCNG LIGNIN PRODUCTS Filed June 17, 1948 JNVENTOR CLA/9K C. HER/TAGE BY W/L L/A/l/ G. l/A/V BEC/(UM fm1 M ATTORNEYS Patented Feb. 13, 1951 PROCESS FOR PRODUCING LIGNIN PRODUCTS Clark C. Heritage, Cloquet,.Minn., and William G. Van Beckum,` Longview, Wash., assignors to Weyerhaeuser Timber Company,

Longview,

Wash., a corporation of Washington ApplicationJune 17, 1948, Serial No. 33,626

8 Claims. (Cl. 260--124) This invention relates to a method for producing lignin products from materials containing cellulose and lignin, such as Wood, cornstalks, straw, bagasse, iiax shives, hemp, etc., these and other similar raw materials being hereinafter referred to as lignocellulose materials. The process of ,the invention is particularly applicable to woods of Various species, representative and suitable Woods being aspen, jack pine, western larch, Douglas r, and Western red cedar. This application is a continuation-in-part of our abandoned application Serial No. 602,917, led July 2, 1945.

When wood is used as a source of lignocellulose materials, it is preferably irst reduced to fibrous form by mechanical or other methods which do not subject the wood to the action of added chemicals other thanwater. This reduction is carried to the point Where it results in the conversion of the wood substance to fibers physically cnsisting substantially of ultimate fibers and opened-up bundles of ultimate fibers, and constitutionally consisting primarily of cellulose, lignin, and polysaccharides-other-than-cellulose, these three constituents being present in ratios in the range of contents falling between that characterizing the raw Wood from which the fiber is derived and that characterizing the water-insoluble content of the raw wood from which the ber is derived. Fiber containing cellulose, lignin, and polysaccharides-other-than-cellulose in the range characterizing the water-insoluble content of the raw wood from which the ber is derived is exremplied by raw Wood ber which has been so treated with water as to extract the Watersoluble constituents and leave as a brous -residue the water-insoluble content of the wood. The production of such ber from woods such as the species hereinabove mentioned is of particular interest, since these woods contain high percentages of water extractable substances, e. g. about 25% in the case of western 'larch.l It may, therefore, be commercially desirable in the case of these woods to extract them with water in order to isolate as commercial' products the Water-soluble fraction of the wood substance. A ber residue is thus obtained which may be employed to advantage as a raw material for the process of the instant invention.

The Wood fibers to which the process of the in- .vention may be satisfactorily applied may be produced, for example, by the method described in U. S. Patent No. 1,913,607 to McMillan. This patent describes a mechanical defibering process entirely free from chemical action, which comprises combing out substantially ultimate fibers from Wood by contacting logs of wood with high speed rotary radial elements such as pointed pins projecting from an axle, like bristles. Fiber produced by this process is herein referred to as McMillan liber, or pin fiber.

Wood fiber suitable for use in the process of the present invention may also be prepared by the method described in U'. S. Patent No. 2,008,982 to Asplund. In this method wood substance is deiibered by mechanically reducing the wood while simultaneously applying sufficient steam pressure to soften the lignin in the middle lamella, thus permitting easy deflbration of the softened Wood. The ber resulting from this practice in efcient operation of the commercial Asplund machine is termed herein normal Asplund fiber, or normal defibrator liber. It is prepared, for example, by reducing Wood While exposing it for about one minute to high pressure steam at a temperature sufficient to effect the desired softening.`

Other processes may be employed for reducing wood substance to said ultimate fiber or opened-'- up bundle form. The wood substance may be affected by steam at any time or times before, during or after such defbration. Action by steam should be such as to avoid any substantial gasification of the wood substance which thus leads to loss or decomposition of Wood substance, usually with the formation of furfural, as well as to altered proportions of the three primary constituents, and unduly altered forms of said constituents. The fibers resulting from processes 'involving both defibering and steaming, which includes those resulting from the Asplund process,v differ from the raw Wood in that their water-soluble content has been to a greater or lesser degree increased by the action of the steam. In the case of normal Asplund aspen fibers made in about one minute at about 128 pounds steam pressure, the increase in Water-soluble content is 4% to 5%.

Other methods for producing fibers from wood substance may also be used, provided said methods do not subject the wood to the action of added ,chemical agents other than liquid water or steam. No known attempts have heretofore been made 3 to isolate lignin products resulting from relatively mild treatments of lignocellulose materials and having such characteristic and reproducible properties as to be useful as raw materials for a variety of industrial applications. In the past, lignocellulose material such as Wood chips has been converted to pulp suitable for use in the manufacture of paper, liber-board, and other products, by relatively severe chemical treatment. Papermaking pulp has been commonly prepared, for example, by treatinggraw'.Woodchips with strong solutions of 'bisulte salts, e. g. calcium bisulte or magnesium bisulte, under conditions of high temperature, high pressure, and for long periods of time.

alkaline chemicals alone or inadmixture, asin the soda, kraft or sulfate, and monosulteprocesses, again employing strong solutions under conditions of high temperature, high pressure, and prolonged operating periods. Although lignin derivatives have been produced-'by all of these processes, it has been the general practice heretofore either to discard them in the Waste liquor, to burn` them to recover the alkali, or to recover part of ,them as a crude aggregate product of indefinite properties Such products as have been obtained from these processes yhave been so modified bythe drastic chemical treatment to which thewood substance has been subjected as to differ materially from lignin as it is originally found in Wood, ,and torepres'ent chemically altered or degraded forms of lignin.

` Lignin is obtained from lignocellulose material in.- accordance with the present invention by treating, such material-with an aqueous alkaline reagent comprising a Weak aqueous solution of an'ralkali-metal hydroxide, e. g. sodium hydroxide, at'. a`vv temperature in the range between about normalroom temperature and about .the boiling temperatureA of theY solution at. normal atmospheric-pressure for a` timesuiiicient substantially to,r exhaust the extracting action of the alkali, therebyv dissolving from the said material lignin and@ polysaccharides-other-than-cellulose and leavinga fibrous residue, separating the said ibrousfresidue from; the alkaline -extract which containsdignin and polysaccharides-other-thancellulose,l conditioning the said.' alkaline extract tocprovide a substantial quantity of salt concentratingwhereby alignin material isy precipitated therefrom, separating the, precipitatedv lignin from thel resulting solution in which polysaccharides-other-than-cellulose` and other lignins remain; dissolved, and extractingv the precipitated lignin withl a.. solvent comprisingv water to--eiTect tirez.. separation thereof into Water-soluble and water-insoluble fractions. ItA isgtherefore an object ,ofy the present invention; tofprovide. a method for the isolation-1 of lign-infromlignocellulosematerials:

Itiis a further object to provide. a methodY for tlfi'esolationv from lignocellulose materials of" lignin'f: in forms.` which have notbeen drastically altered by theaction of strong chemicalreagents.

Stilll another object of the invention is to: provide-a-method for the isolation of lignin from lignocellulose materials whereby-more than one lignin product isobtained, eachof said products havingV characteristic and diierentiatingv properties.

Another object is to provide a method for Vthe from' those" of lignins heretofore'knownrtoy the It has also been common practice tol subject raw wood chips to the action of numerous;

Y isolation ofiignins havingproperties 4differing e art and being applicable, therefore, to unique and varied applications.

1t is still a further object to provide a, method for the separation of lignin from aqueous solutions containing, in addition to lignin, polysaccharides-other-than-cellulose.

It has been found that the above and other objects of the invention may be accomplished by subjecting lignocellulose material, e. g. wood ber, to the action of a dilute aqueous solution of a basic-acting compoundyoi an alkali-metal, separating the resulting solution from the treated material, and separating lignin from the said resulting solution.

In a specilicv embodiment of the invention, wood ber containing substantially all of the waterinsoluble content of the Wood from which the fiber Yis derived and prepared by the hereinabove referredto McMillan, Asplund or other processes, and physicallyconsisting substantially of ultimate bers and opened-up bundles of ultimate bers and` constitutionally consisting primarily of cellulose, lignin, and polysaccharides-otherthan-cellulose, said three constituents being present in mutual ratios `in the range of. contents from those characterizing the Wood from which theberis derived.v to those characterizingthe water-insoluble content ofthe said woodfrom which the fibers4 arederived, istreated--witha dilute aqueous .extracting solution of alkali-metal. The-.alkaline reagent employed is ,typically exemplified by sodium hydroxide, e. g. a 1/4norma1, solution of sodium hydroxide, in a, total amount, with respect to fiber, sumcientto maintain anexraGtng alkalinity` during the operation.V This treatment. is preferablyA carried out atatmospheric. pressure, and at about the boiling point-A of the said solution.- The. time of treatment. is variable depending upon the typeA of .Wood being treated and the other conditions of thetreatf ment, but in general may be up toabout two hours, or such time as shows the extraction to be substantially complete; This treatment extracts from the wood substance a substantial proportion of its lignin and p olysaccharides-other-thancellulose content and leaves a. brous Alignocellulosic residue. After, separation of the residue fromV `the:` causticsolutiom the .caustic solution is treated. for isolation of'lignin therefrom.A Asis morery fully explainedphereinbelow,,this mayfbe accomplished by an integrated series of process steps f comprising, in Variable combinations,v neu,- tralization, concentration;,iiltration, extraction and-the'addition of-.chemical reagents).

The drawing illustratesa suitablemethodlfor the separation of. lignin products-,from an alkaeline. solution resultingatogether with afibrous product, from the extractionA of lignocellulose materials, e. g; wood fiber, Withadilute aqueous solution of alkali. The proceduraoutlinediprogvides. for the isolation from lignocellulosic mate rial oflignin products, .herein arbitrarily desig-n nated'aslignins l-a, l-a'-I, and l-af.-2, as theiree lignin acids and as thezlignin salts. These lignin products. differ from each other in severalrespects,.principally in their. solubility characteristics, analyses, softening andk melting points, and chemical reactivity. Because of these differences inv constitutionand properties,v these diverse ligninproducts may obviouslybe; applied to diverse uses.

In accordance with the procedure outlined-:in thedrawing, it willfbeseen that the process of the invention -is practiced fby" treating 'lignocellus lose material 1, e. g., `wood nber, as the starting raw stock, with an alkaline reacting compound of alkali metal as indicated at step 8. The alkaline reagent employed is typically exemplied by sodium hydroxide. The treatment is conducted at an latmospheric pressure and at a temperature in the range from room temperature to about 140 C. The time of treatment is variable, depending upon the type of wood being treated, but in general may be up to -about two hours, or such time as shows the extraction to be approaching completion. The reacted mass is extracted at step IIJ to separate the soluble matter from the thus treated fiber.

-Step 8, or steps 8 and I0, herein referred to as the alkali treatment, extract from the wood substance a substantial proportion o f the content of lignin and of other organic materials such as polysaccharides-other-than-cellulose, and leave a fibrous residue. Step 8 may be practiced by a batchwise procedure or by a counter-current or recycling procedure as hereinafter more fully discussed. Water is usually employed as the solvent in step I0, but the water may also be admixed with other materials in order to contribute specific properties to the solvent or for specific aqueous suspension, is next iltered at step I2,

or otherwise processed to separate the treated lignocellulose residue I3, herein arbitrarily designated as Fiber I from the soluble matter in the filtrate or solution I5 arbitrarily herein designated Extract I, which contains lignin and the other organic materials including the polysaccharides-cther-than-cellulose.

As solution IE is initially :obtained it may be relatively dilute where a single batch of liber is treated with an extracting solution, or it may be more concentrated where a recycling or counter-current procedure has been used to minimize the water in the systemnlignocellulose, alkali, and water. ln' all cases the pH value of solution I5 will range from neutral to about 10, depending on the extent to which the alkali content has been spent during the reaction with the ligno- Cellulose material. The solution is neutralized at step I6 by addition of inorganic acid, such as hydrochloric acid, sulfuric acid or sodium acid sulfate, bringing it to a pH of approximately '7. The solution as thus acidied is then conditioned for precipitation at step I8. This conditioning may take one of two forms, or a combination of both-by either the removal of water of solution, step 2B, 0r by the addition of inorganic salts, step 22. Both'treatments have in common the fact that they result in the concentration of the solu-V tion to a point at which completion of the lignin precipitation is effected. The precipitated lignin is then Iiltered at step 24 and recovered at 25 as product lignin I-a.

It is desired at this point to elaborate on step I8 of conditioning the solution for precipitation of the lignin, especially since this same step is generally applicable at other steps in the process, or in other sequences, to the separation of the other' ligninproducts at other pH ranges. While some precipitation of lignin may occur by virtue of establishment of the pH range for separation. of the lignin product concerned, the separation of the lignin in this manner is not sharp, and it is advisable to condition the solution in. order to effect the complete precipitation of all the lignin which will separate at the particular pI-I range. After neutralization, the solution may be concentrated by evaporation, which step, if practiced, is included in step I8. The concentration is continued to a point where the lignin content is precipitated in substantial amount. The solution is preferably maintained neutral during this concentration step by the addition of acid as necessary. It will be obvious that the need for concentration by removal of water will depend upon the usage of alkali and the concentration` of the 'alkali in the solution I5. The more theV salt content formed by the interaction between the alkali and the acid, the less will be the extent to which the removal of waterneeds to be continued. It will be further appreciated in this connection that steps I6 and I8 are more or less interdependent and that either step may be performed iirst; that is, either the removal of water or the addition of the salt may precede acidification. It is generally more advantageous, however, for step I8 to follow step I8, because, in this manner, full advantage can be taken of the salts formed by the. neutralization of the alkali present.

When the conditioning ofthe solution for precipitation is to be accomplished by the addition of inorganic salts as at 22, sodium acid sulfate is preferably used, and is added until the solution is near saturation with respect to this compound. At this point, precipitation of lignin I--a can be expected to be substantiallyscomplete. The neutral, concentrated solution containing undissolved lignin,y preferably at room temperature, is ltered at 24, thereby separating lignin I-a, designated 2 5, in the solid form. Division of this lignin product may be elected by extracting it at 2E with hot water.

The hot-water-soluble fraction 28 which contains lignin I-a-Z may be evaporated to dryness at 29 to yield the lignin content of the solution in the salt form 3I. Alternatively, the aqueous solution maybe acidied to a pH of about 1.5 at 32, and the free lignin acids 35i` thereby precipitated. These may be separated by ltration of the solution, preferablyl after heating to about 60 C. to facilitate filtration.

It will be apparent that the process of the invention is iiexible and may be varied as desirable or necessary when processing different species of woods or when employing a range of operating conditions and reagent concentrations. For example, various alkaline materials mayl be employed in the treating step 8. Suitable: alkaline materials include in 'general the hydroxides of the alkali metals as well as those alkali metal compounds which, being salts of strong bases and Weak acids, undergo hydrolysis in aqueous medium to form the alkali-metal hydroxides, or their equivalent in. alkali-metal f ions and Ahydroxyl This resultsin the formation of a hot-water-insoluble lignin` lithium,.sodium, potassium, rubidium and caesi-v um.:v Thehydroxides of this group ofmetals, es-

peciallyisodium hydroxide; arev preferred reagents for feffecting theherein'. described extraction, al-

though: the carbonates,. e. g. sodium carbonate, Vmayfalsobe used..

1 The;2 operating conditions ofthe extraction step, wherein .lignocelluloslc fiber is .extracted with a dilute -faqueoussolution of a` basic-acting alkalimetallv compound, may' beA varied within limits as.

desirablelorlnecessary to suit the particular'lignocellulosel material` being treated. It isthe'teach.- ingofth'e invention', however, and critical'to` its successf'inl practical operation, to use and'main'- tainfoperatin'gi-4 conditions and reagents of such a mild character asf to effect the cleavagev of the lignin-*polysaccharide complexes existing Jin. thevr lig'n'ocell'ulosamaterials,` andthe separation of lignin:l without causing substantial or drastic changesY in composition of the constituents, thereby preserving therinherently great reactivity7 of' naturally occurring lignin. Thus it is preferred touseVJ al solution having a relatively low concentration of alkali-metal hydroxide, i. e, a-solution which contains suicient alkali-metal 'hydroxide tof be'- about 1A; normal with respect'to that vreagent. A preferred solution for eiiecting the extractionV is a 0.6% solution of sodium hydroxide.

Usages of alkali largely in excess of those necessary-to obtain the desired fractionation are also avoided. The ztotal amount of alkali-metal hydroxide used isusually based upon the weight of ber'treated. Thus, forexample, a usage of 15%" sodium hydroxide/signifies that parts by weight ofsodium hydroxide Vis used to extract 100parts offdry ber.

Where a mixing procedureisemployed in the extraction With'alkali-metal hydroxide, the consistency of the reaction mixture (i. e. the weight offber perf'lOO parts by weight 0f solution) is maintained" at a level such as to'afford ease of manipulation and thoroughnessV of treatment. The optimum consistency is obviously dependent upon'manyfactors, principally upon the method o'fhandling the ber mixture. Varying consistencies` may' be used depending'upon Whether the liber is treated 'batchwise or continuously,'as in counter'-'currentl operation.

:Itwill'lbe apparent that concentration, usage` tofavor easeof handling, drying, processingand" relatively complete separation of` extract from treated material.. Arepresentative' combination of these .variables suitableforuse'in extracting Woodsin fibrous form ini accordance with thev process of theinvention comprises the'use offan aqueous sodium hydroxide solution having. a concentration of 0.6% by` Weight sodium. hydroxide inwan amount equal to 15%v by weight of.` theifiher treated, whereupon theV consistencyof the mix.-

ture will-beabcut 4%..V u

' As stated hereinabove, the alkaline: extraction` isf-,carried out at aitemperature which is prefer.- ably about theboiling temperature'of the mixture-'iat about normal atmospheric pressure. In

arrhes-a;

dldinary.; operation Whereftheuproces's is-1.carried; 75

out at;normalatmospheric pressure infonet-mese? sels fand where: the. described .fdilute solutjonsv are? employe-3d, the temperature. of operation will bef about C.l

beemployed. In the caseoi aspen, jackl pine,.- ancl similar Woods, maximum `.treating times c tithe, .order of one i hour Vare-fused, relatively little"y advantage Vobtaining from' longer treating duras tiOIlS.

Largely; forv reasons of economyand eilicient. operation; itisr usually preferred toVVV recyclethe` alkaline solution used in the extraction when batchwise extraction is being practiced.V In. t hiS;l mannen as the caustic-soluble content of the wood substance is built upin the solution,.thef: solution becomes increasingly valuableV as ai; source of extracted materials. Since some ofthe alkali is'consumed by reaction with thewoodsub stance during the extractionV process, it is desir-. able to add a` further quantity of alkali before-4 treating fresh wood liber. In the case of-woodsr such as aspen and jack pine, extracted at'4% consistency with a 0.6% solution of caustic'soda-. about 60% replacement of the original caustic.l

alkali usage after each extraction is suiiicient t0-'f'\` fortify the solution to the desired degree., e. gato a concentration of about 0.6%.in the case of cause" tic soda. Although the number of times anal-1 kaline solution which has been thus fortiedmayf. be used for the extraction of raw Wood is variable*- dependingV largely upon the nature of .thewoodiV it hasbeen observed that extractingzeightitimesf in a manner stated above and fortifying. the -re, sulting extract with additional alkali before eachf extraction results in the production of `an alkaline extract rich in lignins and polysaccharides-vv other-than-cellulose and, at the same-time, leaves.' a fiber residue of useful composition and prop-V erties.

Recycling, or its equivalent operation, mayprof-'f itably be practiced until such time as the contri-1- bution of alkali solublesl ofv each new batch of:` fiber equals the amount of extractedr alkali sol-` uble material retained by the bers'upon .separating the bers and the extract. Obviously; thisvr involves many factors including the amountxof alkali solubles' contributed by each successive@- batch of liber, as Well as the eiciency of the nie-"f chanical stepof ellecting said' separation.`

Similarly,.the conditions Vof operationfcr' iso"-` lating the desired lignin products from the lignin-.containing extract are subject to some` variation. Thus,v various acids may .be usedI for. acidifying the lignin-containing extract. Anyfof the common mineralacids such as sulfuric acidi phosphoric acid or hydrochloric acid, as well-:fas some of the organic acids, e. g. acetic acidgare?l suitable for this purpose. Sulfuric acid is a'pre ferred member of this group.

Theamount of acid used is likewise variable', and depends largely uponthe alkalinity ofthe extract. In general, enough acid is employedito result in the formation Vof a substantially neutralY solution, i. e. one having-a pH of about' '7.

. The neutralized extract is concentrated to2-a1 point at which lignin I-wis insoluble, but at' which its content of'inorganic salts` (principallyl sodium sulfate, when caustic Vsoda andi sulfuric acid are used in the extraction and acidication steps), polysaccharides-other-thanecellulose, and some types'of lignin, are substantially. soluble:- There Vis thus obtained a lignin precipitatev which;r is substantially freefrom contaminationbyim organic salts and polysacclfiaridesfother-thane` cellulose: Although the point at whichV this desideratum is attained varies with the relative i proportions of solvent and solute and with other factors, when the proportions and operating conditions are substantially as given in the examples herein it is preferred to concentrate the neutralized solution to about 12% of its original volume.

Although a substantially aqueous solvent is employed in the extraction of lignin I-a to providevinsoluble lignin I-a-I and soluble lignin l-a--2, relatively minor proportions of other suitable reactive or non-reactive, organic or inorganic, materials may be mixed with the water where desirable or necessary, as Where a sharper separation of these two lignin fractions is desired and thereby effected.

The temperature of the aqueous solvent is likewise variable. In general, an extracting temperature is employed, this being in the range at or near the boiling temperature of the solvent. Where'water alone is used as a solvent, the preferred extracting temperature is at the boiling temperature of water at ordinary atmospheric pressure, i. e. at about 100 C.

In general, `a suflicient amount of water is used to separate completely lignin l--af-I, theinsoluble fraction, from lignin |-a-2, the soluble fraction. Inasmuch as these two lignin fractions diil'er materially in their solubility characteristics, it is preferred to use a substantial excess of aqueous solvent in eiecting their separation. Insoluble lignin I-a-I is obtained in a weakly acidic or neutral form and may be dried and used as such. Soluble lignin |-a--2, however, is obtained as a salt, e. g. as a sodium salt when caustic soda is used as the extracting alkali. It may be obtained as such by evaporation of the aqueous extract and drying of the residue. Although this form may beuseful for some purposes, it may be desired for other uses to obtain the product in the form of a cencentrated aqueous solution or as the free lignin acid. The latter may be accomplished by acidifying the neutral aqueous extract to a pH of about 1.5, using any suitableacid, e. g. a mineral acid such as sulfuric acid, and removing the precipitated lignin acid, as by ltration, followedif desired, by washing and drying. This lignin acid is not identical with lignin l-a-L described above, since it differs therefrom in solubility, degree of acidity, reactivity and other properties. It probably comprises, as do others of the lignin acids described herein, a mixture of organic acids having approximately similar acidities and somewhat similar properties so as to be precipitated together in the operating procedure.

The process of the invention may be illustrated by the following examples, wherein parts are expressed as parts by weight.

EXAMPLE 1 Western red cedar normal Asplund fiber, i. e. ber prepared from the wood of the western red cedar by means of an vAsplund debrator, was extracted with a 0.6% aqueous solution of sodium hydroxide.- A sufficient amount of this solution was used to provide a total sodium hydroxide content equivalent to 15% based on the dry 1 weight of the raw wood ber. sulted in a reaction mixture having a consistency of about`4%, i. e. a mixture containing about 4 parts by weight of fiber per 100 parts of solution. The extraction was eifected at the boiling temperature of the solution `at normal atmospheric This repressure for a durationrof one hour. The fiber was then separated from the alkaline extract and washed with water for subsequent uses. The alkaline extract was fortified by the addition of caustic soda in an amount sufficient to build up the sodium hydroxide concentration to a level substantially that of the original solution. This required replacement of about of the original sodium hydroxide. The fortified solution was then employed in the extraction of a i111'- ther quantity of raw wood ber. A total of eight extractions of raw wood fiber was carried out in this manner, reestablishing the concentration of sodium hydroxide in the extracting solution after each extraction. This resulted in the productionof an alkaline extract rich in materials removed from the wood substances, i. e. rich inlignins and in polysaccharides-otherthancellulose.

This alkaline extract,which has a pH. of about 10, was processed forv the recovery of .a portion of its lignin content. This was accomplished by neutralizing with sulfuric acid and concentrating the neutralized extractby evaporation while adding further sulfuric acid as necessary to maintain the solution neutral. The solution was thus concentrated to about 12% of its original volume. It was then cooled and filtered. This resultedin the separation of lignin fraction I-a. This fraction after separation was boiled with water to further separate it into water-insoluble lignin I-a--I and water-soluble lignin I-a 2.

Lignin l-fa-I resulting from the above treatment was removed by ltration,.dried, :and thus made available for utilization in various applications. The neutral, aqueous solution containing lignin `I--a-Z was subjected to varying procedures in order to obtain the lignin product in any one of various lignin forms.

In one instance, the aqueous solution was evaporated to dryness, thereby forming as a product a dark brownpowder comprising the sodium salt of lignin l-a-2. i

In another case, the neutral, aqueous solution was acidied to a pH of about 1.5. This resulted EXAMPLE 2 McMillan ber, prepared from aspen Wood by means of the McMillan debrator, was extracted EXAMPLE 3 Y yMcMillan jack pine fiber was treated with dilute sodium hydroxide solution and the extract treated using substantially the same procedure as described in Example 1.

EXANIPLE 4 Example 1.

Certain properties of the various lignin products obtained in the foregoing examples are shown in the table, 1

separating the resulting aqueous alkaline treating solution from the said lignocellulcsic residue, neutralizing the `said aqueous alkaline treating solution and conditioning the said aqueous solution by establishing a salt concentration therein in an amount suicient to cause precipitation of a substantial amount of its lignin content, separating the thus precipitated lignin from the residual solution, and treating the said lignin with an aqueous solvent, separating the resulting lignin residue from the resulting lignin-containing aqueous solution, and acidifying the resulting lignin-containing solution for precipitating as free lignin acids the dissolved components of the total lignin fraction.

6. A process for the production of lignin from lignocellulose material which comprises treating said material with an aqueous treating solution of a basic-acting compound of an alkali metal at a temperature of near the boiling temperature of the Said solution at normal atmospheric pressure and in concentration sufficient to provide not substantially more than about 15 parts of said alkali per 100 parts of dry lignocellulose material for a time period of about one hour, thereby forming a solution which contains a composite lignin fraction and polysaccarides-other-than-cellulose and leaving a lignocellulosic residue, separating the said solution from the said residue, neutralizing the said solution and conditioning said aqueous solution by producing therein a salt concentration suiiicient to eiiect the precipitation of a substantial amount of its lignin content, separating the said undissolved lignin from the residual solution, and treating the said undissolved lignin with hot water, thereby extracting therefrom its hot-water-soluble constituents and eiecting its separation into hot-Water-soluble and hot-Waterinsoluble fractions. n

7. The process for obtaining lignin from lignocellulose material which comprises providing the said material in the form of ultimate bers and opened-up bundles of ultimate fibers and constitutionally consisting primarily of cellulose, lignin and polysaccharides-other-than-cellulose, providing and maintaining an aqueous treating solution of an alkali metal hydroxide, treating said bers with said alkaline solution at an elevated temperature and in concentration sufficient to provide not substantially more than about 15 parts of said alkali metal hydroxide per 100 parts of dry lignocellulose material for a time period suflcient substantially to exhaust the extracting action of said solution for dissolving from the bers lignin and polysaccharides-other-than-cellulose and leaving a fibrous residue, separating said fibrous residue from said alkaline solution, neutralizing said alkaline solution and conditioning said solution by producing therein a salt concentration in an amount suiiicient to cause precipitation of a substantial amount of its lignin content, separating the thus precipitated lignin from the resulting solution, and treating the said lignin with an aqueous solvent for extracting components dissolved by said solvent and effecting the separation of said lignin into fractions characterized by solubility and insolubility in said solvent. t

8. The process for obtaining lignin from Wood which comprises providing the wood in the form of ultimate bers and opened-up bundles of ultimate bers and constitutionally consisting primarily of cellulose, lignin and polysaccharidesother-than-cellulose, providing and maintaining an aqueous treating solution of an alkali metal hydroxide, treating said bers with said alkaline solution at an elevated temperature and in concentration suiicient to provide not substantially more than about 15 parts of said alkali metal hydroXide per parts of dry wood bers for a time period suicient substantially to exhaust the extracting action of said solution for dissolving from the fibers lignin and polysaccharides-otherthan-cellulose and leaving a fibrous residue, separating said fibrous residue from said alkaline solution, neutralizing said alkaline solutionand conditioning said Solution by producing therein a salt concentration in an amount sucient to cause precipitation of a substantial amount of its lignin content, separating the thus precipitated lignin from the resulting solution, treating the said lignin with a hot aqueous solvent, separating the resulting lignin residue from the resulting lignin-containing aqueous solution, acidifying the said resulting lignin-containing aqueous solution for precipitating the free lignin acids, and separating the precipitated lignin acids from the resulting solution.

CLARK C. HERITAGE.

WILLIAM G. VAN BECKUM.

REFERENCES CITED The following references are of record in the le of this patent:

Wise: Wood Chemistry, 1944," pages 286-288.

Claims (1)

1. 3. A PROCESS FOR OBTAINING LIGNIN FROM LIGNOCELLULOSE MATERIAL WHICH COMPRISES TREATING SAID MATERIAL WITH AN AQUEOUS SOLUTION OF AN ALKALI METAL CARBONATE AT A TEMPERATURE OF FROM ABOUT NORMAL ROOM TEMPERATURE TO ABOUT THE BOILING POINT OF SAID SOLUTION AT ATMOSPHERIC PRESSURE AND IN CONCENTRATION SUFFICIENT TO PROVIDE NOT SUBSTANTIALLY MORE THAN ABOUT 15 PARTS OF SAID ALKALI PER 100 PARTS OF DRY LIGNOCELLULOSE MATERIAL FOR DISSOLVING FROM THE MATERIAL LIGNIN AND POLYSACCHARIDES-OTHER-THAN-CELLULOSE AND LEAVING A LIGNOCELLULOSIC RESIDUE, SEPARATING THE RESULTING AQUEOUS ALKALINE TREATING SOLUTION FROM THE SAID LIGNOCELLULOSIC RESIDUE, SUBSTANTIALLY NEUTRALIZING SAID ALKALINE SOLUTION AND CONDITIONING THE SAID AQUEOUS SOLUTION BY ESTABLISHING A SALT CONCENTRATION THEREIN IN AN AMOUNT SUFFICIENT TO CAUSE PRECIPITATION OF A SUBSTANTIAL AMOUNT OF ITS LIGNIN CONTENT, SEPARATING THE THUS PRECIPITATED LIGNIN FROM THE RESIDUAL SOLUTION, AND TREATING THE SAID LIGNIN WITH AN AQUEOUS SOLVENT FOR EXTRACTING COMPONENTS DISSOLVED BY SAID SOLVENT.

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