US 2538457 A
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M. S. HUDSON Jan. 16, 1951 TREATING WOOD Filed Nov. 2, 1946 Patented Jan. 16, 1 951- UNITED STATE S PATENT OFFICE product has numerous advantages, among which may be mentioned the ease with'which a potentially reactive'resin may be incorporated'in the same and' the stability of the wood product when exposed to moisture.
The primary object of the invention'is the provision of an improved rapid, economical and reliable process for producing such a completely dried hydrolyzed wood in massive or comminuted form, or in the form of powderor flour suitable for molding purposes. This process employs (1) hydrolyzing during which condensates from the steam and'products of the hydrolysis reac-, tion soluble therein are constantly removed from contact with the wood and from the treating chamber, and (2) the drying of such hydrolyzed wood in an atmosphere of an'organic drying medium which is a solvent for organic solvent soluble extractives produced by the hydrolysis or already present in the wood whereby the same are removed from the wood. In other words, the
process assures that the condensates from steam and hydrolysis products soluble therein are continually removed during hydrolysis whereby such valuable by-products may be recovered in a form free from de radation and that objectionable organic solvent soluble extractives produced by hydrolysis or already present are simultaneously removed in the drying operation incident to forming woocl'having a zero moisture content.
In the manufacture of hydrolyzed products in accordance with the invention from Wood in the form of structural lumber, plywood and comminuted wood and similar materials, the same is subjected to a'vapor treatment with either steam containing small amounts of hydrochloric acid, as a'c'atalyst, or steam with small amounts of aniline to produce mild hydrolysis 'for the purpose of removing hemicelluloses. After this vapor treatment, pressure with air or inert gas may be built up in the wood in the treating chamher; The treating chamber is then filled with water still maintaining the pressure of inert gas resentative examples of 2 or air, as in the Rueping process (see United States Patent No. 709,799, Reissue No. 12,707, and Patent No. 1,008,864). Water is driven into the wood by employing a higher pressure, and this water serves to wash out the hydrolysis products on the release of the pressure and institution of vacuum or suitable reduced pressure conditions. One or more of these cycles may be employed for completely washing out the hydrolysis products from the wood. The wood may then be dried byemploying vapor phase drying, as described in my Patent No. 2,273,039 and my application Serial No. 579,851, now Patent No. 2435218, using a suitable drying medium such as Stoddard solvent. As disclosed in my above identified patents, in efiecting dehydration of wood any suitable organic material which can be vaporized and which vapor-will permeate wet wood and flash-off the moisture content thereof without deleteriously affecting the wood may be.
used. There are numerous and practically unlimited examples of suitable materials, but repsatisfactory materials are as follows:
Organic compounds, whether saturated or unsaturated, chain or cyclic, and any of their homologues that might be suitable for this procedure, such as alcohols, ethers, amines, acids, aldehydes, ketones, esters, halides, cyanides, sulphides, polyhydric alcohols, anhydrides such as phthalic and nitro compounds; of which the following are examples:
n-Decane n-Decyl alcohols n Decyl amines n-Decyl esters n-Decyl' halides n-Decanoic acids n-Decyl ketones n-Decyl 'aldehydes n-Decyl cyanidesn-Decyl sulphides Preferred examples of suitable, organic drying mediums are creosote, petroleum distillates, coal tar, wood tar or wood distillates, and the following:
High boiling alcohols:
Amyl Isopropyl Isobutyl Diethylene glycol Glycerol Aldehydes:
Butyric aldehyde Benzaldehyde Crotonaldehyde Furfural High boiling amines:
. Aniline Dimethyl-aniline Mono-, diand tri-ethanolamines Pyridines Quinollnes High boiling esters:
Butyl acetate Amyl acetate Butyl lactate Dlbutylphthalate Diamylphthalate Glycol monoetnyl ether acetate Isopropyl lactate Octyl acetate Diglycololeate Glycol stearate High boillng ethers:
Diamyl ether Diethylene glycol monoethyl ether Halides:
Chlorobenzenes Chlorinated phenols Nitrochlorobenzenes Ortho-dichlorobenzenes Ortho-nitrochlorobenzenes Para-dichlorobenzenes Nitro compounds:
Nitrobenzene Ortho-nitrotoluenes Hydrocarbons:
Benzenes Toluenes Mesitylenes Cumenes Naphthalenes Diphenyl KetonesBenzophenone Furfural or other resin forming material may be used as the drying medium if it is desired to leave in the wood resinous condensation products, i. e., to incorporate a synthetic resin in the wood.
In the manufacture of hydrolyzed products, by means of acid hydrolysis, in accordance with this invention, from coinminuted Wood the material is wetted with a solution of a mineral acid, e. g., sulfuric acid of about 1% strength and subjected in a rotating basket in 'a closed cyiim der to the action of steam at a temperature of 340 to 360 F. (105 to 135 lbs/sq. in. gauge pressure) for a period of 20 to 40 minutes, depending on the particle size of the commlhuted wood and the lignin content desired in the final product. The steam pressure is then released through a line in the bottom of the treating cylinder so that condensates and drainings from the WOOd, which contain sugars, furfural, and other by-products are forced into a condensate flash tank in which there is a line in the vapor space leading to the atmosphere. By releasing the pressure in the flash tank to the atmosphere the hydrolysis liquor containing sugars and non-volatile substances is concentrated. The steam being released is lead through suitable heat exchangers both for the purpose of recovering heat and steam volatile hy-products such as furfural and acetic acid by condensation.
When the pressure in the cylinder has reached atmospheric, wash Water may be introduced and the hydrolyzed wood product washed by rotating the basket. After each washing period the Wash water is drained 01f and a spray of Wash Water directed on the rotating basket from a spray line provided in the cylinder. washings in the manner described are continued until the hydrolyzed product is free of hydrolyzing acid and products or hydrolysis. A. satisfactory indication of this point is when a distilled water sample in which a sample of thehydrolyzed wood has been boiled snows a pH of 5.0 to 6.0.
The washed hydrolyzed product may then be vapor dried in the same cylinder by subjecting it to the action of the vapor from a boiling hydrocarbon, such as Stoddard solvent,'or other suitable organic drying or drying and impregnating medium, introduced to the cylinder while rotating the basket. The solvent may be removed if desired after drying has been completed by employing a suitable vacuum step.
In the accompanying drawings, I have illustrated a preferred apparatus, but it is to be understood that this apparatus may be suitably modified in order to carry out the invention within the scope of the appended claims.
In the attached drawing there is shown diagrammatically the apparatus which I employ for processing of Wood or Wood products with the vapor-liquid method for the production of hydrolyz'ed wood.
In the drawing A is a horizontal metal retort or cylinder such as, for example, a creosoting cylinder. B is a cylindrical basket-like container for Wood shavings, sawdust, chips or similar mechanically disintegrated Wood substance. This basket is constructed of Wire mesh of suitable size covering a rigid frame work l9. Spiral baffies H are arranged within this frame work to aid in mixing the material when the basket is rotated. The numeral l2 indicates an engaging device such as a female gear to accommodate a gear I3 on the shaft M which passes through packing gland [5 to the sprocket i6 driven by a chain I! from motor [8 and serves as a means for slow speed rotation of the basket B. The numeral l9 indicates a bearing on the cylinder B which receives the stationary shaft 20 on the door of the retort. When the door of the retort is-closed the shaft 28 and bearing I9 support the cylinder B in cooperation with the rotating supporting means [Sand l4.
Rollers 21 supported on cylinder A, Whichcontact circular tracks or hands 22 forming part of frame work 18 on cylinderB, serve to align and support the basket during rotation. Suitable lever "operated rollers (not shown) may also be arranged for shifting to contact longitudinal bands '23 of frame work l8 and thus support basket B for loading or unloading from chamber A.
The cylinder A is connected through ports a, b and c to vapor line LVI which connects through valve 24 to evaporator or boiler C. The nipples from the line LVI through ports a, b and c are extended into the cylinder about 4" to prevent drain back: of condensate in the cylinder to line LV!. Through ported, e and f the cylinder is connected to vapor line LV-2 having valves 25 and 26 to line LV-3 leading to dephlegma'tor D or the 7 cylinder is connected pump 29. 1 1
evaporator into line HL2 and returns to the The following example is illustrative ofthe manner of using this apparatus to produce hydrolyzed wood of high lignin content.
Comminuted wood, e. g., wood chips having a havingvalve Sl by a pump, not shown, through valve 32, pump 33, and valve 34 to spray line SLl and spray header 35; the acid solution being sprayed on the basket and its contents during slow rotation of the basket. When the comminuted wood in the basket has-been saturated to'the desired extent withacid, as may be determined by gauging the tank from which the acid is beingdrawn, the pump is stopped and valves 3], 32 and 34 areclosed. During the spraying operation any of the acid solution not takenup by the wood may be allowed to drain from the cylinder to tank, F by opening valve 36 on line LL- -l. It may then be returned to storage by opening valve 3! on line LLII, by a suitable pumping means, not shown. Thecylinder A is then connected to the atmosphere through line LV2 by opening valves and 21 to condenser E and valve 33 on line LV5. Steam is then introduced to, the cylinder from the evaporator C :(which in this case may be a simple steam boiler) by opening valve on line LV I. Assoon as I the air in the cylinder has been displaced by the steam, as will be shown by live steam being discharged from line LV5, valves 25, 21, and 38 arethen closed. Valves 39 and M are then opened, the steam passing from the evaporator through lines LVI, LV--2 to the cylinder A. Steam pressure in'the cylinder A thereby rapidly ,in'creased to 195-135 lbs/sq} in;, which usually requires fromB to 5 minutes During this time" the basket B is kept rotating at a rate of Std 15R. P. M. Valve 36 is partially opened to allow condensate containing reaction products from the'wood to drain into condensate tank F,
'valve t! on line LV -S being openedto condenser In. this manner condensates from thecylin der A is being continually removed from the hydrolyzing theater and is being concentrated in tank F by the flashing oif of steam and steam volatile products to the condenser E which may be operating also as a heat exchanger to recover heat from the steam. 'In lieu'of the manually operated drain valve 33am automatic condensate discharge trap may be employed to transfer the condensate fronr'the cylinder A to'th'e conden'sate tankF.
The conditions of temperature (340 F. to 360 F.) and pressure (195 to 135 lbs/sq. in.) are maintained in the cylinder for the necessary time dried usingthe apparatus shown in the attached required to give the desired lignin content in the final product. About 20 to 30 minutesunder'the operating conditions described above will yield a product having a lignin content of 40 to 45%.
At the endof .this' time valves 39 and 49 are suitable. storage, not shown, by means of a pumping means, not shown, entering the heat exchanger D through line LL-Z and passing through the. tube section of D to a suitable discharge line, not shown, returning to the wash water storage. 1
4 Condensate forming in.D may be allowed to fill that heat exchanger and spill over to condenser E by opening valve 43 on line LV-l2.
Condensation of steam and steam distilled byproducts from the wood occurs in condenser E when water is introduced to the tube section of that condenser by suitable means, not shown. The condensate is collected in condensate receiving tank H and may be transferred therefrom to a volatile by-product storage or tosuitable fractionating equipment, not shown, through line LL5 having valve 44.
Release of pressure from the cylinder A is usually completed in a matter of from 5 to l 10 minutes. 7
When the pressure in the cylinder A has 1 reached atmospheric, heated wash water at a temperature of to F. is pumped into the cylinder from a suitable source through line LL9, having valve 3i, valves 32' and 35 being opened. The wash water enters thecylinder quire about30 minutes to l'hour, the wash water,
is drained from the cylinder by opening a suitable discharge, not shown, onthe bottom of the cylinder. At the-end-of such periods of draining wash water may be sprayed on the basket and contents and the latter allowed. to drain for a short period thereafter before introducing water for the next. main washing cycle.
a About 3 or- 4 such washinQg-cycleswill be found sufficient to remove the acid and hydrolysis prod ucts, a total of 10 to 15 thousand gallons of wash water per ton of dry hydrolyzed wood, delivered in 3 or 4 wash-ing'cycles, are required for the, washing. a a
The damp hydrolyzed product is then vapor ap the dedrawing in accordance with. the methods scribed in my Patent No. 2,273,039 and my plication Serial No. 579,851. 7 Operation of apparatus for drying is the same as that scribed in the application SerialNo. 579,851 cept that the wood is contained in a rotating basket instead of on trams which applies in the case of massive wood.
The apparatus shown in the drawing may be used for hydrolysis of wood by vapor treatment with water acidified with small amounts of H61 to prepare it for subsequent treatment with aniline andfurfural to produce ligno-cellulose plastic molding powders as described in U. S. Patents luv- VA Nos. 1,923,756 and1-.,932,255.. After hydrolysis. the material may be washed in. the. cylinder B and subsequently dried by introducing. vaporized; aniline or furfural. Drying by means; or. aniline.- or an aldehyde in vapor phase. gives. a much. more thorough. and. uniform. distribution of: the plasticizer throughout. the. mass and the heating of the wood. at the; boiling pointof. the chemicals produces a much more stable ligninecelluiose aniline complex, or lignin-cellulose-iuriural plastic when the material is molded. I
In preparing hydrolyzed: products from. either massive timber or comminuted. wood. according. to the present. inventiom. where:- drying. is resorted. to, this is carried outv in accordance with my aforesaid patent and. applications to substantially zero moisture content.
The hydrolyzed products obtained, whether from massive timber or comminutedwood, are completely dried and are identifiable because they are substantially devoid ofwater soluble extracts such as hexose sugars and furi'uralproduced by the hydrolysis action. Moreover the hydrolyzed products are further identifiable by being substantially devoid of organic solvent soluble extractives such as Wood gums and resins, either normally present or produced by said hydrolysls because these are removed when the treated wood is completely dried with an organic vapor which is a solvent for such extractives.
To the dried comm-muted wood treated as above there may be incorporated a potentially reactive synthetic resin. Among such resins are those obtainable from phenol-aldehyde, aminealdehyde, urea-aldehyde, Glyptal and cumarone resin com onents. Prererably about 2: by weight or the potentially reactive synthetic resin is introduced to the comminuted wood which may in some cases be further reduced in size so as to pass through a 20 mesh screen or smaller. In this manner a heat moldable or heat compressible composition is formed.
It will be observed that condensates from. the steam and products of the hydrolysis reaction soluble therein are continually removed as formed from contact with the. wood and by removing these condensates from the treating chamber and lowering the pressure. and temperature conditions surrounding them, for example as in the flash tank F, the usual degradation which occurs when these products are left in the. environment of the treating conditions in. the chamber A is largely prevented and the by-products. are in a much more usable and valuable form.
After the hydrolysis treatment the; wood is usually washed with water and in the case of comminuted wood as much water expressed there.- from as possible before the same is: introduced to the vapor phase drier. This vapor phase drying with an organic vapor. as set forth. in my above mentioned patents, not only produces a completely dry wood but, as mentioned above, removes the organic solvent soluble extractives produced by the hydrolysis, or already present in the wood. These wood gums, although. being resinous in nature, are, as a. rule, not generally miscible with synthetic resins and hence will deter the latter from readily wetting and penetrating the wood in the most satisfactory manner and furthermore such wood resins are generally hygroscopic in nature. although not water soluble and hence are poor binding agents. Therefore it is desirable that these wood gums or resins be removed.
Jlclaimti Y i j 1. The process of hydrolyzing wood which comeprisesz: treatingthe: wood in a. closed chamber; with steam in the. presence. of an acid catalyst and simultaneously with. hydrolysis: of the Wood: removingirom said chamber the condensate. from the steamandproductsof the hydrolysis reaction soluble therein.
2-. The process of. hydrolyzing, wood which. com.- prises treating the wood in a closed chamber with steam in. the presence of. an acid. catalyst-and simultaneouslywith hydrolysis of the woodremoving from said chamber the condensatesfrom.
the steam and. products of the. hydrolysis reaction soluble therein, and thereafter removing organic solvent soluble extractives. produced by the. hydrolysis together with such extractives already present in. the wood while; drying to. zero moisture content with an organic solventv vapor.
is The process. of hydrolyzing wood. which comprises. treating the same. in comminuted COIldie tionin. a closed. chamber with steamin thev pres.- ence of an acid. catalyst and simultaneously with hydrolysis. of the-wood removing from said chamber the condensates. from the steam and products of the hydrolysis reaction soluble therein, washing said? hydrolyzed wood. with water, and there after removing organic solvent: soluble. extractives produced by the hydrolysis together with such 1 extractives already present in the wood while drying to zero. moisture content with an organic solvent vapor. a
4. The process of hydrolyzing wood which oomprises treating the same in comminutedcondition in a closed chamber with steam in the presence of an acid catalyst and simultaneously with hydrolysis of the wood removing from said cham ber the condensates from the steam and products of the hydrolysis reaction soluble therein and recovering the said by-products' of the hydrolysis continuously as formed during hydrolysis of the wood, washing said hydrolyzed wood with water, and thereafter removing organic solvent soluble extractivesproduced by the hydrolysis together with such extractives already present in the Wood while drying to zero moisture content with an organic solvent vapor.
5. The process oftreating wood which comprises wetting the wood with a dilute mineral acid, subjecting th wood in. a. closed chamber to the action of live steam and simultaneously with said treatment of the wood removing from contact therewith the. wood condensates and reaction products of the treatment soluble in said condensates, subjecting the treated Wood to washing with. water, expressing the. Water from the washed and. treated wood, and drying-the washed and treated wood in the presence of an organic drying medium in vapor phase which is a solvent for. the organic solvent soluble. products produced by the. treatment as. well as such products already present in the wood.
6-. A. wood treatmentv process. comprising wet.- ting disintegrated wood particles with a dilute mineral acid, subjecting said wood particles, in. a closed chamber to the action of live steam, maintaining said steam treatment at atemperature of about 340 F. to 36.0 F. for a time sufficient to give the desired lignin content in the treated wood, washing the time treated wood particles with water to remove the water soluble reaction products therefrom, and drying; the washed wood particles. with heated, inert. organic vapor which removes the remaining water and the organic solvent solubles from the wood and efiects thorough drying of the wood.
7 7. A process of treating wood to render it suitable for resin impregnation, comprising wetting the wood with a dilute solution of a mineral acid, subjecting the wood in a closed chamber to the action of live steam, continually removing the wood condensates and reaction products soluble therein from said chamber so as to avoid degradation thereof, continuing the steam treatment until the desired lignin content in the wood is obtained, washing the thus treated wood with water to remove water solubles, and then drying the washed wood by passing through said chamber a flow of highly heated, inert, organic drying vapor that removes the moisture and the organic solvent solubles from the wood.
8. A process of treating wood to render it suitable for resin impregnation, comprising wetting the wood with a dilute solution of a mineral acid, subjecting the woo-d in a closed chamber to the action of live steam at a pressure of about 105- 135 pounds per square inch, continually removing the wood condensates and reaction products soluble therein from said chamber so as to avoid degradation thereof, maintaining the steam treat ment at a temperature of about 340 F. to 360 F. until a lignin content of about 40% to 45% in the wood is obtained, washing the thus treated wood with hot water to remove water solubles, repeating this washing treatment a plurality of times and removing the wash water from the chamber, and then drying the washed wood by passing through the chamber a flow of highly heated,
inert, organic drying vapor that removes the moisture and the organic solvent solubles from the wood.
MONIE S. HUDSON.
REFERENCES CITED The following references are of record in the file. of this patent:
UNITED STATES PATENTS Number Name Date 150,111 Voelter Apr. 21, 1874 1,037,185 Gallagher et al. Aug. 27, 1912 1,059,820 Besenfelden Apr. 22, 1913 1,087,743 Ekstrom Feb. 17, 1914 1,890,304 Scholler Dec. 6, 1932 2,080,077 Howard May 11, 1937 2,108,567 Scholler Feb. 15, 1938 2,123,211 Scholler July 12, 1938 2,123,212 Scholler July 12, 1938 2,153,316 Sherrard Apr. 4, 1939 2,156,160 Olson Apr. 25, 1939 2,196,277 Schorger Apr. 9, 1940 2,315,372 Kressman Mar. 30, 1943 2,323,194 Beveridge June 29, 1943 2,325,570 Katzen July 27, 1943 FOREIGN PATENTS Number Country Date 435,896 Canada July 23, 1946 OTHER REFERENCES Katzen et a1: Ind. Eng. Chem., pp. 314-322, vol. 34, No. 3 (Mar. 1942).