US1866917A - Manufacture of cellulose material from hemp fibers - Google Patents

Description

Patented July 12, 1932 UNITED STATES PATENT OFFICE EDWAJRD GHAUNCEY WORDEN, 151, OF MILIBURN, NEW JERSEY, ASSIGNOR TO HANSON 03TH N YORK, N. Y. A FIRM GOMPOSED or GEARLESD. ORTH, sn, AND CHARLES 1). 0mm, an, AND MICHAEL J. smrrn: 1

MANUFACTURE OF CELL'ULOSE MATERIAL FROM IEEMP FIBERS 1T0 Drawing.

This invention relates to the industrial treatment and utilization of the fibers for the production of purified cellulose therefrom, of various kinds, species or'grades of hemp said cellulose in the purified state,

having een found highly advantageous forthe manufacture of rayon, as more specifically set forth in my co-pending application, Serial No. 347,457 of March 15, 1929, for manufacture of rayon from hemp fiber. By rayon or artificial filaments is understood to comprise those esters and ethers of cellulose, which, after being placed. in solution, are afterwards forced through minute orifices into a liquid or other medium whereby they are precipitated into a hydrated cellulose with decomposition of the cellulose compound or cellulose ester, or deposited as the cellulose ester by the volatilization of a volatile solvent. Of the first group would be included rayon produced from viscose and cuprammonium cellulose. From the second group, would be included the nitrocellulose filaments which are afterwards denitrated, the organic esters of cellulose such as acetated cellulose, and the alkyland aryl-celluloses,

{.ypified by ethylcellulose and benzyl-celluose.

There appears to be a looseness in the use of the word hemp by some writers. Hemp in this invention is intended to cover hemp fibers, as stated on page 190 of Report No. 9, U. S. Department of Agriculture, A descriptive catalogue of useful fiber plants of the world, by Charles Richards Dodge, published at the Government Printing Oflice, Washington, D. C., 1897. Of these hemp fibers therein listed, I have obtained especially useful cellulosic fibers for the production of rayon and artificial filaments by the use of fibers and other components from the hotanical group Musa, of which Mum temtz'lz's and Musa sapz'en-tum are perhaps most well known. the partially purified state, whether that pu- Hemp fibers in general, when in Application filed March 16, 1929. Serial No. 347,728.

rification be entirelymechanical or not, are distmgulshed by their great tensile strength, and also by their resistance to-chemical treatment with the minimum of degradation, de-

phacellulose or resistant cellulose, and con-- taining but small amounts of hemicelluloses and other inferior celluloses or cellulosic bodies, which renders purified hemp cellulose, peculiarly adapted to the formation of high strengthartificial filaments, provided the series of treatments or steps to which the cellulosic material is subjected in transformation from. cellulose toartificial filaments, is carried on without serious weakening of the hemp cellulosic structure or strength. 1

In the cellulose ester and cellulose ether art in general, and. the nitrocellulose industry in particular, those who have lived the art, and not merely worked in it, have been aware that in an identical method and procedure of esterification, the initial length and strength of the cellulose fiber to be esterified bears a definite relation tothe strength of the esterified cellulose made therefrom, and this relationship of strength and tenacity is especially exemplified when the esterized cellulose is dissolved and placed in filament or film form from an evaporation therefrom of the volatile solvents contained therein. In other words, where thetensile strength and length offiber of the initial purified cellulose is relatively high, other conditions of treatment being the same, the esterified prod not will be correspondingly high in tensile strength and other desirable characteristics.

That is, they are increased with an increase in strength of the original cellulose from which produced by the esterifying or other process towhich the cellulosic fibers are sub jected, and that the stronger the original purified cellulosic fiber, other conditions remaining substantially the same, the stronger will films and filaments be when the cellulose is transformed into ester form, dissolved and deposited either as a filnrby the removal of solvent, or as a filament by the same procedure, by precipitation, setting, coagulation or otherwise.

That is, a relatively long fiber cotton upon nitration, for example, will produce a cellulose ester, which when dissolved and the solvent removed therefrom, forms a film or filament of greater tensile strength and other desirable physical qualities than will a relative ly much shorter cotton fiber (such as linters or-fiy). This difference has been found to be due in a measure to the greater length and strength of the individual cellulose cell in the longer fiber cotton.

Furthermore, in the production of those cellulose esters represented by the Xanthated celluloses (viscose) it has been noted that the relatively shorter wood cellulose fibers do not admit of the production of a rayon filament of as high tensile strength and other desirable physical characteristics as when the relatively longer purified cotton cellulose fibers have been submitted to the same esterification steps under comparable conditions, and cotton cellulose fiber is being admixed with wood cellulose fiber at the present time for viscose rayon manufacture, in order to increase the tensile strength both in the wet and dry state and other qualities, over that which would normally result if wood cellulose alone be used.

There appears to be a well defined relationship between the length and strength of the original cellulose fiber used for esterification purposes and the tensile strength and other qualities of filaments and films producible therefrom, irrespective of whether the final product is the cellulose ester in the solid form or whether the final product is .a de-esterified filament or film as in viscose and nitrocellulose rayon.

It is conceded that hemp fiber possesses unusual strength when compared with wood fiber or cott-oncellulose fiber, all in the purified state.

Coincidental with an increase in tensile strength of initial purified cellulosic-fiber as used for esterification purposes, usually comes a diminished reactivity, especially to chen'ncal treatments, and adjustments of concentration, avidity ofreactiveness, time factor, temperature, etc. are usually necessary d e to this property, when operating upon celluloses from various origins. This is readily seen at the present time, in endeavors to supplant a portion of the wood cellulose here- I tofore used in viscose rayon production, with an equivalent amount of purified cotton fiber,

usually linters on account of its inexpensiveness.

In general, from a chemical reactive point of view, cotton cellulose is more obdurate to treatment than is wood cellulose, and purified hemp fiber cellulose than is cotton cellulose, especially when subjected to the various steps involved in esterification primarily for rayon production, and corresponding variations ,and adJustment in chemicals, concentration,

product, whether that product be an ester or an ester which has been de-esterified, usually with the production of hydrated cellulose.

This invention. therefore, is primarily concerned with the respective steps in treatment of the fibers commercially classified under the general heading of hemp as heretofore indicated, for the preparation therefrom of a cellulosic material high in alphacellulose, and relatively low in hemicellulose and other inferior cellulosic bodies, and admirably adapted for the transformation into ravens and other artificial filaments, films, etc. by virtue of its high alphacellulose or resistant cellulose content, and virtue of practical absence of inferior of cellulose and cellulosic bodies.

In the illustrative example to follow, it is to be understood that the method of procedure will necessarily vary, as well as the amounts and nature of chemicals used, time, temperature, pressure and concentration factors, depending upon the source from which the hemp was obtained whether from the male or female plant, and the physical condition as to disintegration of the fibers or bundles of fibers, at the time the treatment of purification is commenced.

It is immaterial whether the hemp has been submitted to a retting operation, is scutched or heckled, or a combination of two or more of the operations has been applied to it. I prefer as the first chemical operation (the fiber previously having been placed in physical condition to make it of maximum receptivity to chemical treatment) to boil the fibers or fiber bundles or aggregates with an excess of water containing 3%7% free sodium hydroxide, Q.5%3% alkali silicate and 0.5%- 4% cottonseed oil or other readily saponifiable vegetable or animal oil, or an equivalent amount of the oil already saponified. Satisfactory results have also been obtained by substituting for the saponified oil, the alkali metal salts of the sulfonated oils (i. e. Turkey red oil, alizarin assistant, saponified-sulfonated corn oil, etc.). The fiber is placed in s to a running cold water washing treatment.

a pressure kier, and submitted to heat, preferably at a temperature of around 110 C. circulation being aided, if desired, by means of a circulatory arrangement for pumping continuously the boil-off liquor over the mass of fibers. It has been found that the addition to the boil-off liquor of an amount of soluble water glass is especially beneficial in scouring and removal of intercellular and cementitious material, fats, oil,= wax and similar encrusting and adhering impurities, and tends to leave the fiber in an especially porous and absorptive condition for quick and complete penetration of reagents used in normal esterifying and etherifying processes. The boiloif operation is continued from 3 to 8 hours depending upon the comparative amounts of impurities in the fibers or fibrous aggregates, after which the boil-off liquor is allowed to drain oil, and clear Water added, and heat applied, and this alternate addition of water, heating, and discarding of the wash water is continued until the wash waters are practically colorless, and a sample of material when extracted in a Soxhlet'or other suitable apparatus with a chemical-such as ether, gives practically no extractive.

, The fibers are, stillxin the Wet condition, passed through friction rollers which tend to break down and disintegrate the fibrous bundles 'orimasses, the fibers being subjected in an ,elutriating manner, whereby intercellular and encrusting'material is disintegrated, and floats off in the water. fibers are then hydro-extracted, and submitted to an electrolytic (preferably) chlorine bleach, care being taken that the fibers are not exposedto the atmospheretduring the bleaching and subsequent acidifying operation, to minimize formation of oxycellulose and other oxidation cellulosic compounds.

The'now nearly white fibers are washed until all traces of reactants are removed, and dried at a comparatively low temperature. For ease in manipulation during esterification, and the steps preceding and succeeding it, it is advisable to make the fibers into sheet paper, either along or with admixture thereto.

One or more of the foregoing steps may be prolonged, shortened or repeated, depending upon the comparative refractoriness of i the hemp fiber to be purified, or the concen- The trations of the baths may be increased or diminished, as conditions may arise.

The purified hemp cellulose, as the mean of determinations of several runs, gave figures as follows Per cent Molsture (drying at 105 C.) 6.1 Ether extractive 0.12

Hemicellulose and similar bodies (less than) 1. Ash (inorganic impurities) 0.14

The absorption of the cellulose is shown by the factthat a pledget of the same placed upon the surface of water at room temperature will be immersed by its own weight, usually in less than 30 seconds. Alphacellulose determinations made on various samples indicated that it was practically pure alphaor resistant cellulose, and with but negligible amounts of other cellulosic materials present, while the original tensile strength of the fiber was substantially conserved.v The color of the-individual fibers varies from a light straw color to pure White, depending upon the thoroughness and care exercised in the purification treatments. Inasmuch, however, as rayon filaments are usually bleached, I prefer to submit the cellulose to what is known in the trade as between a threequarters and full bleach, in order to conserve to the maximum, the tensile strength of the individual cellulosic fibers.

I am aware that it is proposed to produce paper from hemp fibers by the addition thereto in a partially purified state of varying amounts of filling and loading materials, sizes, albuminous and other organic and inorganic products to induce specific surface and interior effects in the paper so produced. I lay no claim to this.

But what I do claim and desire to secure by Letters Patent is:

1. A process for treating hemp fibers for the isolation therefrom of alphacellulose in a highly purified condition, comprising mechanically disintegrating said fibers, removing impurities therefrom by treatment with a hot solution of alkalinehydi'oxide, alkaline silicate and a softening body, removing reac'tants and products of decomposition by Washing, bleaching the same in the absence o'fthe air, and Washing free from chemicals, substantially as herein set forth.

2. A process for treating hemp fibers comprising mechanically disintegrating the same, removing therefrom alkali-soluble matter by boiling in Water, removing water-soluble components by Washing and bleaching, finally removing reacting chemicals by washing until a neutral mass is obtained, as herein described.

3. A process for the production of cellulosic material relatively high in alpha-cellulose and relatively low in hemicellulosicand other inferior cellulosic bodies from hemp .fiber, comprising boiling the original fibers in an aqueous solution containing the hydroxide and silicate of an alkali metal until all alkali-soluble material has become water soluble, washing until neutral, and removing coloring matter therefrom by Ways now known, as herein set forth.

4. A process for the treatment of hemp fibers to obtain therefrom cellulose of maximum suitability for esterification purposes, comprising treating the hemp fiber suitably subdivided with a saponified vegetable oil containing an excess of alkali until non-cellulosic bodies have been saponified, emulsified or otherwise rendered water-soluble or removable by washing, eliminating said impurities by a washing treatment, decolorizing the purified cellulose, and washing to a neutral reaction, substantially as herein set forth.

5. A process for the treatment 'of hemp fibers to obtain therefrom purified resistant cellulose, comprising treating the finely subdivided fibers with a non-solvent of cellulose containing alkali hydroxide and silicate which is at the same time a solvent or emulsifier of the non-cellulosic impurities therein, removing said non-cellulosic bodies by a Washing process in water with the minimum of'degradation of the cellulosic portion, then bleaching and washing to a neutral reaction the purified cellulose so obtained, asrset forth herein.

6. A process for the purificationof hemp fibers from the non-cellulosic 'bodies normally contained therein, comprising treating said fibers preferably in a fine state ofsubdivision with an emulsifying and saponifying agent containing alkaline metal 40 hydroxide and silicate, and which; is at the same time a solvent of hemicelluloses and a non-solvent of alphacellulose, continuing said treatment in a hot aqueous solution until the alphacellulose has been separated from its impurities, washing to remove said impurities, bleaching the alphacellulose thus formed to increase its porosity and receptiveness for esterifying chemicals, then washing until neutral, substantially as herein set forth.

In witness whereof I attach my signature hereto.

EDWARD CHAUNCEY woman, 1a.