US3781187A - Method of separating bark components - Google Patents

Method of separating bark components Download PDF

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Publication number
US3781187A
US3781187A US00232737A US3781187DA US3781187A US 3781187 A US3781187 A US 3781187A US 00232737 A US00232737 A US 00232737A US 3781187D A US3781187D A US 3781187DA US 3781187 A US3781187 A US 3781187A
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Prior art keywords
bark
solvent
cork
percent
wax
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US00232737A
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F Trocino
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Bohemia Lumber Co Inc
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Bohemia Lumber Co Inc
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    • D—TEXTILES; PAPER
    • D01—NATURAL OR MAN-MADE THREADS OR FIBRES; SPINNING
    • D01C—CHEMICAL OR BIOLOGICAL TREATMENT OF NATURAL FILAMENTARY OR FIBROUS MATERIAL TO OBTAIN FILAMENTS OR FIBRES FOR SPINNING; CARBONISING RAGS TO RECOVER ANIMAL FIBRES
    • D01C1/00—Treatment of vegetable material
    • D01C1/02—Treatment of vegetable material by chemical methods to obtain bast fibres

Definitions

  • ABSTRACT Cl 162/93 5 Douglas Fir bark is extracted with a hot neutral or- [51] Int Cl Cub 11/00 D016 6 ganic solvent to separate the wax from the bark. [58] Fieid l 62/9398 91 74 Thereafter, the residue is heated to desolventize the 162/72 55 4, f same and expand the cork fraction substantially in 560/4122; size.
  • the bark of trees and particularly, the bark of the Douglas fir consists principally of cork, parenchyma tissue and sclerenchyma or bast fibers.
  • the cork is so called because it is a spongy, resilient, low density material resembling ground cork from the Mediterranean oak in appearance and in many of its properties.
  • the cork contents of Douglas fir bark varies from 32 to 50 percent depending on the location and age of the tree.
  • the parenchyma tissue is a friable phloem consisting principally of sieve tubes. Such tissue readily disintegrates to a fine powder.
  • the sclerenchyma or bast fibers comprise a tough fibrous portion of the phloem occuring in tightly cemented bundles which, upon grinding or subjection to mild attrition, are reduced to the individual or ultimate fibers.
  • Such individual fibers viewed under a microscope, are red-brown in color, short and sharply pointed and appear to have a spindle shape with a length approximately ten times their diameter.
  • Variations in particle sizes of individual fibers have been noted from 0.016 to 0.090 inch in length and from 0.002 to 0.008 inch in thickness at their midsection with the bulk of the-particles having an average length of about 0.054 inch and an average thickness of about 0.005 inch.
  • the bast fiber content of Douglas fir varies between 35 and 48 percent by weight on an air dried basis.
  • the individual fibers are very resistant to comminution and tend to maintain their identity even when subjected to severe pulverizing action by which other portions of the phloem are reduced to powder.
  • Bast or bark fibers are particularly useful in the formulation of thermosetting phenol-aldehyde holding compositions, the fibers being incorporated in substantial proportions to serve as an extender materially to reduce the cost of the compositions.
  • the fibers also impart high flexural and tensile strength to the molded product and give increased impact resistance thereto.
  • Past attempts to separate the bark components have made use of various comminutive devices to reduce the particle size of the bark, followed by various methods for separating or classifying the solid material, such as milling, screening or shearing.
  • raw bark is ground or milled at a controlled moisture content to a suitable particle size. It is then fractionated mechanically by screening, winnowing or other procedures which separate it into fractions comprising predominately bast or bark fiber, parenchyma and cork.
  • a still further object of the present invention is to provide a method of separating bark components wherein the bast or bark fibers are obtained free of any encrustation by parenchyma tissue.
  • the solvent extraction of the bark and the subsequent desolventizing of the residue expands the pieces of cork to facilitate this separation.
  • a quality of cork is achieved comparable to that of Mediterranean oak.
  • Good yields of the bast or bark fibers are also achieved, and such are of high purity and quality.
  • FIG. 1 illustrates a flow diagram of the process in accordance with the teachings of the invention.
  • FIG. 2 illustrates schematically the solvent extracting step.
  • the first step in my process is to grind the bark in a hammermill having a screen with holes about threesixteenths inch in diameter.
  • the mixture thereby achieved is then dried to between about 3 and 8 percent moisture by weight, although this step is not mandatory. Achieving this degree of dehydration is preferable in that it facilitates ultimate recovery of the solvent.
  • the mixture is then extracted with a neutral organic solvents examples of suitable ones being hexane, bezene, the chlorinated hydrocarbons, napthalenes, toluene and the like.
  • a neutral organic solvent examples of suitable ones being hexane, bezene, the chlorinated hydrocarbons, napthalenes, toluene and the like.
  • An example of such a solvent which I have found suitable is that sold by Standard Oil Company of California as SOCAL No. 226. This solvent has the following characteristics:
  • Boiling Point 50% at 208 F. 90% at 213 F.
  • the solvent is heated to a temperature of about 150 F. and is percolated through the mixture of ground bark for about 2 hours, the solvent being introduced to the bark in a hopper having a 200 mesh screen at its bottom and being permitted to flow therethrough by gravity. Solvent passing through the mixture is reheated to 150 F. by a heating coil in a holding tank and thereafter recirculated for the desired time. See FIG. 2.
  • the solvent is circulated through the bark mixture so as to remove between about 3 and 6 percent of the wax based on the dry weight of the bark.
  • Whole Douglas fir bark has between about and percent wax by weight on a dry basis, and I have found that removing approximately 60 percent of the total wax satisfactorily prepares the bark for classification as described hereinafter. A longer period of extraction would dissolve more of the wax, but 1 have found this unnecessary.
  • the surfaces of the bast fibers in the bark mixture are cleaned by the action of the percolating solvent during the extraction, the solvent dissolving the adhering and encrusting material. This facilitates ultimate classification of the components.
  • the bark is drained of solvent, placed in a dryer and heated to about 500 F. for 2 to 4 minutes to dry off the solvent.
  • the solvent can then be condensed, recovered and reused. Heating the bast fibers to 500 F. in the desolventizing step conditions them to that temperature, thereby to make the fibers suitable for end uses requiring an ability to withstand this temperature.
  • the desolventizing of the bark residue after extraction of the wax expands the pieces of cork therein substantially in size.
  • the process of desolventizing expands the individual cork cells, puffing them up visibly in size as the heat evaporates the solvent.
  • the wax can subsequently be recovered from the solvent, thus making possible percent utilization of the bark.
  • the wax extracted residue is then mechanically classified using standard classification equipment, but without the necessity of any further grinding, milling or shearing to achieve ultimate separation of the cork, bast fiber and nonfibrous phloem fractions.
  • the corky fraction of the bark having expanded substantially in size during the desolventizing of the wax extracted residue, is more resilient than its original counterpart, and thismakes classification much easier.
  • the bast fibers achieved in the process are cleaner and of a better quality than those achieved in the aqueous alkali process above mentioned. Furthermore, complete recovery of the solvent and subsequent recovery of the wax therefrom insures that the instant process provides no ultimate disposal problem as in the aqueous alkali process, wherein the caustic solution with the dissolved constituents therein must ultimately be burned.
  • Example 1 Eighty-three pounds of Douglas fir bark were ground in a hammermill having a 3/16 inch round hole screen and subsequently dried to 16.5 percent moisture. The mixture was extracted for two hours with SOCAL No. 226 solvent at F., 2 gallons per minute of the solvent being pumped through a hopper containing the bark mixture as illustrated in FIG. 2. The extracting yielded 5.1 percent wax by weight from the bark on a dry basis. The bark residue was thereafter desolventized by being placed in a 500 F. dryer for four minutes. Classification in a Prater classifier realized the following yields of bark components as a percentage of the weight of the desolventized bark:
  • Example 2 Seventy-eight pounds of Douglas fir bark were ground in a hammermill as in Example 1 and dried to 6.4 percent moisture. The mixture was extracted with SOCAL No. 226 solvent at a temperature of between 150 and 157 F. for 2 hours at a flow rate of 2 gallons per minute. The yield of wax was 3.6 percent by weight on a dry basis. The extracted residue was desolventized in a dryer as in Example 1 for 2 to 3 minutes. Classification in a Prater classifier yielded bark components in the following amounts as a percentage of weight of the desolventized bark:
  • Cork 35% Bast fibers 47% Powder 18% The two examples illustrate that the amount of cork recovered varies with the yield of wax which is to be expected since most of the wax is in the cork in Douglas fir.
  • a method of treating bark containing cork, bark fiber and nonfibrous phloem fractions comprising reducing the bark to the form of small pieces comprising a mixture of pieces of cork, bark fiber and nonfibrous phloem; extracting said mixture of pieces with a neutral organic solvent, thereby separating from said bark wax which is soluble in said solvent and leaving a residue of wax-extracted bark; then heating said residue to desolventize the same and expand said pieces of cork substantially in size,
  • a method as in claim 1 in which said bark is dried to a moisture content between about 3 and 8 percent by weight prior to extracting the same.
  • solvents should be sol baht, m

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  • Engineering & Computer Science (AREA)
  • General Chemical & Material Sciences (AREA)
  • Chemical & Material Sciences (AREA)
  • Molecular Biology (AREA)
  • Life Sciences & Earth Sciences (AREA)
  • Chemical Kinetics & Catalysis (AREA)
  • Health & Medical Sciences (AREA)
  • Wood Science & Technology (AREA)
  • Zoology (AREA)
  • Textile Engineering (AREA)
  • Chemical And Physical Treatments For Wood And The Like (AREA)
  • Extraction Or Liquid Replacement (AREA)
  • Compounds Of Unknown Constitution (AREA)
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US00232737A 1972-03-08 1972-03-08 Method of separating bark components Expired - Lifetime US3781187A (en)

Applications Claiming Priority (1)

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US23273772A 1972-03-08 1972-03-08

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US (1) US3781187A (es)
JP (1) JPS5632001B2 (es)
AU (1) AU460199B2 (es)
CA (1) CA975907A (es)
GB (1) GB1402617A (es)

Cited By (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3929446A (en) * 1974-04-19 1975-12-30 Bohemia Inc Slow nitrogen releasing fertilizers and methods of making the same
FR2401241A1 (fr) * 1977-08-22 1979-03-23 Etienne De Berwinne Ef Preparation aux usages industriels des vegetaux a fibres

Cited By (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3929446A (en) * 1974-04-19 1975-12-30 Bohemia Inc Slow nitrogen releasing fertilizers and methods of making the same
FR2401241A1 (fr) * 1977-08-22 1979-03-23 Etienne De Berwinne Ef Preparation aux usages industriels des vegetaux a fibres

Also Published As

Publication number Publication date
JPS5632001B2 (es) 1981-07-24
CA975907A (en) 1975-10-14
GB1402617A (en) 1975-08-13
JPS48103714A (es) 1973-12-26
AU4542672A (en) 1974-02-14
AU460199B2 (en) 1975-04-17

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