CA1284262C - Method of molding using dissociated lignocellulosic material and the product so produced - Google Patents
Method of molding using dissociated lignocellulosic material and the product so producedInfo
- Publication number
- CA1284262C CA1284262C CA 538105 CA538105A CA1284262C CA 1284262 C CA1284262 C CA 1284262C CA 538105 CA538105 CA 538105 CA 538105 A CA538105 A CA 538105A CA 1284262 C CA1284262 C CA 1284262C
- Authority
- CA
- Canada
- Prior art keywords
- lignocellulosic material
- mold
- molding
- dissociated
- molded product
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Expired
Links
- 239000012978 lignocellulosic material Substances 0.000 title claims abstract description 77
- 238000000034 method Methods 0.000 title claims abstract description 50
- 238000000465 moulding Methods 0.000 title claims abstract description 50
- 239000000463 material Substances 0.000 claims abstract description 67
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 claims abstract description 32
- 239000002360 explosive Substances 0.000 claims abstract description 5
- 239000003063 flame retardant Substances 0.000 claims abstract description 5
- 239000003755 preservative agent Substances 0.000 claims abstract description 5
- 230000002940 repellent Effects 0.000 claims abstract description 4
- 239000005871 repellent Substances 0.000 claims abstract description 4
- 230000002335 preservative effect Effects 0.000 claims abstract 3
- 239000000203 mixture Substances 0.000 claims description 29
- HYBBIBNJHNGZAN-UHFFFAOYSA-N furfural Chemical compound O=CC1=CC=CO1 HYBBIBNJHNGZAN-UHFFFAOYSA-N 0.000 claims description 26
- 239000000126 substance Substances 0.000 claims description 22
- 235000000346 sugar Nutrition 0.000 claims description 19
- 229910052799 carbon Inorganic materials 0.000 claims description 18
- 239000002253 acid Substances 0.000 claims description 12
- 239000003054 catalyst Substances 0.000 claims description 11
- 239000003431 cross linking reagent Substances 0.000 claims description 11
- 239000000835 fiber Substances 0.000 claims description 9
- 239000000945 filler Substances 0.000 claims description 9
- 229920005610 lignin Polymers 0.000 claims description 9
- -1 sawdust Substances 0.000 claims description 8
- 239000004033 plastic Substances 0.000 claims description 6
- 239000010902 straw Substances 0.000 claims description 6
- NOEGNKMFWQHSLB-UHFFFAOYSA-N 5-hydroxymethylfurfural Chemical compound OCC1=CC=C(C=O)O1 NOEGNKMFWQHSLB-UHFFFAOYSA-N 0.000 claims description 5
- 230000002378 acidificating effect Effects 0.000 claims description 5
- 229930182470 glycoside Natural products 0.000 claims description 5
- 150000002338 glycosides Chemical class 0.000 claims description 5
- RJGBSYZFOCAGQY-UHFFFAOYSA-N hydroxymethylfurfural Natural products COC1=CC=C(C=O)O1 RJGBSYZFOCAGQY-UHFFFAOYSA-N 0.000 claims description 5
- 238000012856 packing Methods 0.000 claims description 5
- 238000005406 washing Methods 0.000 claims description 5
- 239000002023 wood Substances 0.000 claims description 5
- OKTJSMMVPCPJKN-UHFFFAOYSA-N Carbon Chemical compound [C] OKTJSMMVPCPJKN-UHFFFAOYSA-N 0.000 claims description 4
- 239000002841 Lewis acid Substances 0.000 claims description 4
- 239000003245 coal Substances 0.000 claims description 4
- 239000003337 fertilizer Substances 0.000 claims description 4
- 229910052500 inorganic mineral Inorganic materials 0.000 claims description 4
- 239000011707 mineral Substances 0.000 claims description 4
- 150000007524 organic acids Chemical class 0.000 claims description 4
- 241000609240 Ambelania acida Species 0.000 claims description 3
- 229920002488 Hemicellulose Polymers 0.000 claims description 3
- 239000010905 bagasse Substances 0.000 claims description 3
- 238000001035 drying Methods 0.000 claims description 3
- 239000011152 fibreglass Substances 0.000 claims description 3
- 238000011049 filling Methods 0.000 claims description 3
- 150000007517 lewis acids Chemical class 0.000 claims description 3
- 229920000049 Carbon (fiber) Polymers 0.000 claims description 2
- 239000010425 asbestos Substances 0.000 claims description 2
- 239000004917 carbon fiber Substances 0.000 claims description 2
- 238000002156 mixing Methods 0.000 claims description 2
- 229910052895 riebeckite Inorganic materials 0.000 claims description 2
- 239000004576 sand Substances 0.000 claims description 2
- 235000012431 wafers Nutrition 0.000 claims description 2
- 229920002522 Wood fibre Polymers 0.000 claims 1
- 238000007599 discharging Methods 0.000 claims 1
- 239000002025 wood fiber Substances 0.000 claims 1
- 239000000446 fuel Substances 0.000 abstract 1
- 239000000047 product Substances 0.000 description 42
- 238000004132 cross linking Methods 0.000 description 20
- 239000011230 binding agent Substances 0.000 description 10
- QTBSBXVTEAMEQO-UHFFFAOYSA-N Acetic acid Chemical compound CC(O)=O QTBSBXVTEAMEQO-UHFFFAOYSA-N 0.000 description 9
- SRBFZHDQGSBBOR-IOVATXLUSA-N Xylose Natural products O[C@@H]1COC(O)[C@H](O)[C@H]1O SRBFZHDQGSBBOR-IOVATXLUSA-N 0.000 description 9
- 150000001720 carbohydrates Chemical class 0.000 description 7
- 235000014633 carbohydrates Nutrition 0.000 description 7
- PYMYPHUHKUWMLA-UHFFFAOYSA-N arabinose Natural products OCC(O)C(O)C(O)C=O PYMYPHUHKUWMLA-UHFFFAOYSA-N 0.000 description 6
- SRBFZHDQGSBBOR-UHFFFAOYSA-N beta-D-Pyranose-Lyxose Natural products OC1COC(O)C(O)C1O SRBFZHDQGSBBOR-UHFFFAOYSA-N 0.000 description 6
- 238000004880 explosion Methods 0.000 description 6
- 239000002904 solvent Substances 0.000 description 6
- 229920001221 xylan Polymers 0.000 description 5
- 150000004823 xylans Chemical class 0.000 description 5
- QAOWNCQODCNURD-UHFFFAOYSA-N Sulfuric acid Chemical compound OS(O)(=O)=O QAOWNCQODCNURD-UHFFFAOYSA-N 0.000 description 4
- 239000003795 chemical substances by application Substances 0.000 description 4
- 239000000243 solution Substances 0.000 description 4
- 239000007858 starting material Substances 0.000 description 4
- 238000006243 chemical reaction Methods 0.000 description 3
- 239000012530 fluid Substances 0.000 description 3
- 235000010755 mineral Nutrition 0.000 description 3
- 229920001542 oligosaccharide Polymers 0.000 description 3
- 150000002482 oligosaccharides Chemical class 0.000 description 3
- 150000003839 salts Chemical class 0.000 description 3
- 239000003377 acid catalyst Substances 0.000 description 2
- 150000007513 acids Chemical class 0.000 description 2
- 239000001913 cellulose Substances 0.000 description 2
- 229920002678 cellulose Polymers 0.000 description 2
- 239000007795 chemical reaction product Substances 0.000 description 2
- 239000003153 chemical reaction reagent Substances 0.000 description 2
- 238000002485 combustion reaction Methods 0.000 description 2
- 239000000428 dust Substances 0.000 description 2
- 238000010438 heat treatment Methods 0.000 description 2
- 238000004519 manufacturing process Methods 0.000 description 2
- 235000005985 organic acids Nutrition 0.000 description 2
- 239000005011 phenolic resin Substances 0.000 description 2
- 229920001568 phenolic resin Polymers 0.000 description 2
- 239000011120 plywood Substances 0.000 description 2
- 239000002689 soil Substances 0.000 description 2
- JIAARYAFYJHUJI-UHFFFAOYSA-L zinc dichloride Chemical compound [Cl-].[Cl-].[Zn+2] JIAARYAFYJHUJI-UHFFFAOYSA-L 0.000 description 2
- GBOVPZFEODYRSR-UHFFFAOYSA-N 2-(hydroxymethyl)-3h-furan-2-carbaldehyde Chemical compound OCC1(C=O)CC=CO1 GBOVPZFEODYRSR-UHFFFAOYSA-N 0.000 description 1
- IAJILQKETJEXLJ-UHFFFAOYSA-N Galacturonsaeure Natural products O=CC(O)C(O)C(O)C(O)C(O)=O IAJILQKETJEXLJ-UHFFFAOYSA-N 0.000 description 1
- 240000005979 Hordeum vulgare Species 0.000 description 1
- 235000007340 Hordeum vulgare Nutrition 0.000 description 1
- 229910002651 NO3 Inorganic materials 0.000 description 1
- 240000007594 Oryza sativa Species 0.000 description 1
- 235000007164 Oryza sativa Nutrition 0.000 description 1
- 229930040373 Paraformaldehyde Natural products 0.000 description 1
- 108010064851 Plant Proteins Proteins 0.000 description 1
- 241000209140 Triticum Species 0.000 description 1
- 235000021307 Triticum Nutrition 0.000 description 1
- 240000008042 Zea mays Species 0.000 description 1
- 235000005824 Zea mays ssp. parviglumis Nutrition 0.000 description 1
- 235000002017 Zea mays subsp mays Nutrition 0.000 description 1
- 238000010521 absorption reaction Methods 0.000 description 1
- IAJILQKETJEXLJ-QTBDOELSSA-N aldehydo-D-glucuronic acid Chemical compound O=C[C@H](O)[C@@H](O)[C@H](O)[C@H](O)C(O)=O IAJILQKETJEXLJ-QTBDOELSSA-N 0.000 description 1
- 239000007864 aqueous solution Substances 0.000 description 1
- 239000010426 asphalt Substances 0.000 description 1
- 239000003086 colorant Substances 0.000 description 1
- 238000012505 colouration Methods 0.000 description 1
- 150000001875 compounds Chemical class 0.000 description 1
- 238000011109 contamination Methods 0.000 description 1
- 239000007799 cork Substances 0.000 description 1
- 235000005822 corn Nutrition 0.000 description 1
- 235000014113 dietary fatty acids Nutrition 0.000 description 1
- 238000010790 dilution Methods 0.000 description 1
- 239000012895 dilution Substances 0.000 description 1
- 229930195729 fatty acid Natural products 0.000 description 1
- 239000000194 fatty acid Substances 0.000 description 1
- 150000004665 fatty acids Chemical class 0.000 description 1
- 239000007789 gas Substances 0.000 description 1
- 229940097043 glucuronic acid Drugs 0.000 description 1
- 230000005484 gravity Effects 0.000 description 1
- 230000007062 hydrolysis Effects 0.000 description 1
- 238000006460 hydrolysis reaction Methods 0.000 description 1
- 239000012212 insulator Substances 0.000 description 1
- 238000002386 leaching Methods 0.000 description 1
- 239000011159 matrix material Substances 0.000 description 1
- 150000007522 mineralic acids Chemical class 0.000 description 1
- 235000015097 nutrients Nutrition 0.000 description 1
- 229920002866 paraformaldehyde Polymers 0.000 description 1
- 238000005325 percolation Methods 0.000 description 1
- 230000008635 plant growth Effects 0.000 description 1
- 235000021118 plant-derived protein Nutrition 0.000 description 1
- 239000011148 porous material Substances 0.000 description 1
- 238000004382 potting Methods 0.000 description 1
- 239000000843 powder Substances 0.000 description 1
- 238000004537 pulping Methods 0.000 description 1
- 238000011084 recovery Methods 0.000 description 1
- 235000009566 rice Nutrition 0.000 description 1
- 239000010454 slate Substances 0.000 description 1
- 241000894007 species Species 0.000 description 1
- 150000008163 sugars Chemical class 0.000 description 1
- 239000013589 supplement Substances 0.000 description 1
- KCDXJAYRVLXPFO-UHFFFAOYSA-N syringaldehyde Chemical compound COC1=CC(C=O)=CC(OC)=C1O KCDXJAYRVLXPFO-UHFFFAOYSA-N 0.000 description 1
- COBXDAOIDYGHGK-UHFFFAOYSA-N syringaldehyde Natural products COC1=CC=C(C=O)C(OC)=C1O COBXDAOIDYGHGK-UHFFFAOYSA-N 0.000 description 1
- 235000012141 vanillin Nutrition 0.000 description 1
- MWOOGOJBHIARFG-UHFFFAOYSA-N vanillin Chemical compound COC1=CC(C=O)=CC=C1O MWOOGOJBHIARFG-UHFFFAOYSA-N 0.000 description 1
- FGQOOHJZONJGDT-UHFFFAOYSA-N vanillin Natural products COC1=CC(O)=CC(C=O)=C1 FGQOOHJZONJGDT-UHFFFAOYSA-N 0.000 description 1
- 239000013053 water resistant agent Substances 0.000 description 1
- 239000011592 zinc chloride Substances 0.000 description 1
- 235000005074 zinc chloride Nutrition 0.000 description 1
Landscapes
- Compositions Of Macromolecular Compounds (AREA)
- Dry Formation Of Fiberboard And The Like (AREA)
Abstract
ABSTRACT OF THE DISCLOSURE
Dissociated lignocellulosic material produced by a process of explosive depressurization is molded into products of widely varying densities. Various fibrous and woody materials can be incorporated into the molded product to give a wide range of nailing and strength characteristics. Colour, water repellent, preservative and fire retardant materials can be mixed with the material before molding. Other aggregates can be bound into the molded product which can contain fire enhancement materials for fuel.
Dissociated lignocellulosic material produced by a process of explosive depressurization is molded into products of widely varying densities. Various fibrous and woody materials can be incorporated into the molded product to give a wide range of nailing and strength characteristics. Colour, water repellent, preservative and fire retardant materials can be mixed with the material before molding. Other aggregates can be bound into the molded product which can contain fire enhancement materials for fuel.
Description
METHOD OF MOLDING USING DISSOCIATED LIGNOCELLULOSIC
MATERIAL AND THE PRODUCT SO PRODUCED
Field of the Invention This invention relates to a method for producing a molded product from dissociated lignocellulosic material and to the product of this process. It also relates to the use of dissociated lignocellulosic material as a binder to replace in whole or in part the phenolic resins which are normally used in the production of plywood, waferboard, oriented strand board, particleboard and other molded products.
Dissociated lignocellulosic material, the starting material for the molding process described herein, is produced by a process of explosive depressurization. The explosion process utilizes lignocellulosic material, which includes such plant growth materials as oat hulls, corn stalks, bagasse, wheat straw, oat straw, barley straw, rice straw and woods of various species. The explosion process comprises the following steps: (l) packing the lignocellulosic materials in a divided, exposed, moist form in a pressure vessel having a valved outlet; (2) with the valve closed, rapidly filling the pressure vessel with steam at a pressure of at least 400 psi to bring substantially all of the lignocellulosic material to a temperature in the range 185C to 240C in less than 60 seconds to thermally soften the lignocellulosic material into a plastic condition; and (3) as soon as the plastic condition has been attained, opening the valved outlet and instantly and 1~84Z6Z
explosively expelling the lignocellulosic material from the pressure vessel to atmosphere. This explosion process breaks the chemical crosslinks between the lignin and hemicellulose and produces a mixture of chemical substances. This mixture, referred to in this specification as "dissociated lignocellulosic material", is a particulate substance having the appearance of potting soil. It consists primarily of cellulose, lignin, aceti~ acid, glucuronic acid, furfural, xylose sugars and xylan, which substances are substantially chemically dissociated from each other. The steam explosion process is further described in Canadian Patent Nos. 1,096,374, 1,141,376 and 1,217,765 to DeLong, and the apparatus used in the process i~ illustrated and described therein.
Summary of the Invention It has previously been conceived that dissociated lignocellulosic material would be used as an animal feedstuff, or as a starting material from which the various chemical component~ of the mixture could be obtained. However, it has now been found that it is possible to recombine the dissociated components of the mixture produced by the process of explosive depressurization of lignocellulosic materials into a heavily crosslinked matrix by subjecting the mixture to heat and pressure in a mold. Various combinations of molding pressure and temperature and mold dwell time may be used to vary the degree of crosslinking of the material and thereby control the strength and density of the end product.
` 1284:;~62 In some embodiments, the water-soluble components of the dissociated mixture are removed and then replaced by an alternative crosslinking composition.
In addition, it has been found that it is possible to make a molded product from a mixture of dissociated lignocellulosic material and various fibrous or woody materials. In this case, the dissociated lignocellulosic material acts as both a filler and a binder. Further, the dissociated lignocellulosic material in acting as a binder can encapsulate a variety of other aggregates such as coal, asphalt, fiber glass, and other non-woody materials.
The invention is therefore directed to a method of molding dissociated lignocellulosic material, with or without the addition of aggregate materials, to form a rigid product. The moisture level of the starting material may be reduced, if necessary, to a level suitable for molding. The material is then packed into a mold which has been preheated to a suitable temperature.
Sufficient presBure iB then applied for a sufficient time to form a rigid product. The molded product may be cured to relieve internal stresses by placing it under pressure in an unheated mold.
The invention is preferably directed to a method of molding dissociated lignocellulosic material comprising preparing the dissociated lignocellulo6ic material by packing lignocellulosic material in a divided, moist form in a pressure vessel having a valved outlet; with the valve closed, rapidly filling the pressure vessel with steam at a pres~ure of at least 400 pBi to bring substantially all of the lignocellulosic material to a temperature in the range of 185 C to 240 C in less than 60 seconds to thermally soften the lignocellulosic material into a plastic condition: as soon as the plastic condition has been attained, opening the valved ,. -- 3 --.Z8426Z
outlet and instantly and explosively expelling the lignocellulosic material from the pressure vessel to atmosphere, wherein the explosive expulsion breaks the chemical cross-link between the lignin and hemicellulose of the lignocellulosic material and produces a mixture of water-soluble chemical substances, whereby di~sociated lignocellulosic material is produced. Next, the said dissociated lignocellulosic material is washed with water to substantially remove the said water-soluble chemical substances.
A cro~s-linking agent and catalyst therefor is added to the washed dis~ociated lignocellulosic material to provide a moldable dissociated lignocellulosic material, said cross-linking agent being ~elected from the group consisting of a five carbon sugar, a ~ix carbon sugar, their glycosides and con~ugates, furfural, and hydroxymethylfurfural, and mixtures thereof, and said catalyst being an acidic cataly~t. The moldable dissociated lignocellulosic mat-rial i~ dried to a water content of about 5% or less. The moldable material iB then packed into a heated, vented mold, wherein sufficient pressure is applied in the range of 20-700 psi for a ~ufficient time in the range of 5 seconds to 30 minutes and at a sufficient temperature in the range of 70 C to 260 C to the ~oldable material in the mold to cause it to form a r~gid product.
The molded product iB then discharged from the mold.
The economics of producing molded board and other products can be improved significantly by the removal of the water soluble fraction of the dissociated lignocellulosic material, and ~eparating the isolated chemicals. This is especially true because the cost of replacement crosslinking chemicals is markedly less than the value of the ---------------------------------------3 a -water-solubles. A preferred method of extracting the water-soluble chemical compounds from dissociated lignocellulosic material comprises placing the material in a column having an upper and a lower opening, adding the water through the top opening, and, without agitating the contents of the column, allowing the solvent to percolate down through the dissociated lignocellulosic material, under the force of gravity, and then removing the solvent and dissociated substances through the lower opening of the column. Aqueous solutions of lignin crosslinking compositions can then be added to the column for wet mixing, by percolation as for water wa8hing. The column contents are then removed, dewatered, then further dried ae nece#sary to lower moisture levels. The resulting product can be molded in the samè manner as that de~cribed herein for dissociated lignocellulosic material that has not been treated in this manner. `~
Detailed Descri tion of the Preferred Embodiment p Dissociated lignocellulosic material freshly produced by the processes described above and in Canadian Patent NOB . 1,096,374, 1,141,376 and 1,217,765 will normally contain excessive moisture, that is, a level of moisture that will hamper the molding process. It has been found that drying the material prior to molding it until the water content is about 5% produces good results. This drying may be carried out by simply exposing the material to air at ambient temperature for a sufficient length of time. The precise water content is not critical to the molding process as it will still work, though less well, if somewhat more or less moisture is present.
Once the water content has been thus reduced, the material may be packed or injected into a mold of the desired size and shape. The molded product has been found to be a suitable substitute for particleboard, waferboard, fibreboard, hardboard, plywood and the like, so the mold may be shaped accordingly.
The molding pressure, temperature and dwell time selected will depend on the type of product desired.
The molding may take place over a wide range of temperatures. The cros~linking reactions that occur during molding take place more quickly at higher temperatures. It has been found that as the molding temperature is increased, the density of the product increases at constant pressure.
Temperatures in the range of about 70C to 260C have been found useful in producing a general-purpose product. The desired molding temperature may be achieved by preheating the mold, and in this specification "molding temperature" means the temperature of the mold. Whether all of the material in the mold is heated to this temperature depends on the thickness of the mold and the dwell time. Alternatively, it is pos6ible, when molding large volume products, for instance, railroad ties or structural components, to preheat the starting materials rather than, or in addition to, heating them in the mold. Preheating the material should ...
., . , . . . ~ .
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be carried out in a closed vessel to prevent the escape of furfural and the like.
The molding pressure may also be selected from a wide range of pressures, depending on the desired density of the molded product. It has been found that molding pressures from about 20-1500 psi may be used. Pressures in the range of 600-700 psi can be used to produce a good general-purpose product.
To make a molded product similar to cork, a molding temperature of about 70-110C and a molding pressure of about 20-90 psi may be used. Such a product might be used to encapsulate slow release nutrients in a biodegradeable planting pot.
It is possible to produce a low density molded product having increased toughness and water resistance by molding at relatively low temperature (e.g. 70-120C) and then applying a mold platen heated to about 300C for a short time.
This plasticizes the cellulose at the surface of the molded product.
To make a molded product having a density similar to that of furniture board (medium density), a molding temperature of about 120-145C and a molding pressure of about 100-700 psi may be used.
To produce a high density molded product, a molding temperature of about 120-165C and a molding pressure of about 700-1500 psi may be used. Using suitably high pressures and temperatures it is possible to produce a very high density , lZE~
material which could be used, for example, to replace slate in pool table tops. Such a product is so dense that a .22 caliber rifle bullet, fired from close range, will not penetrate beyond 4 or 5 mm.
The dwell time in the mold may vary over a wide range depending on the thickness of the board and the desired density of the product. The material acts as an insulator; a thicker molded product requires more time for the heat from the mold to fully penetrate it and for it to cure after crosslinXing occurs. To achieve uniform crosslinking across the thickness of the product, longer dwell times can be used, and the temperature may be reduced accordingly. It has been found that for a given temperature, pressure and thickness, increased dwell time results in increased product density. Dwell times in the range of about 5 seconds to 30 minutes have been used with success.
The mold ~hould be vented to permit the continuous escape of steam and other gases produced during molding.
In some cases, the molded material should be permitted to cure after molding to relieve internal stresses.
For high density material, a longer cure time is required and it may be desirable immediately after molding to transfer the molded product to an unheated mold at pressures similar to the molding pressure to allow the product to cure.
When dissociated lignocellulosic material is molded in the manner described, the lignin crosslinks with furfural, fatty acids and xylan. As the molding temperature is increased, up to about 240C, the acids in the dissociated lignocellulosic material react at an increasing rate with the xylan and xylose sugars to produce higher concentrations of furfural, which will in turn increase the degree of crosslinking with the lignin, thereby producing a denser and stronger product. By controlling these reactions, one can vary the strength, water resistance and density of the molded product.
If it is desired to increase the speed of the reaction or lower the molding temperature, or both, an acid catalyst (such as a mineral acid, an organic acid, or a Lewis acid or a mixture thereof) can be added to increase the rate and degree of hydrolysis of the xylan and xylose sugars to furfural, which in turn increases the degree of crosslinking with the lignin. It i8 also possible to add paraformaldehyde, six carbon sugars either free or combined as glycosides or as short chain oligosaccharides, or some other croæslinking agent to the dissociated lignocellulosic material to produce a higher degree of crosslinking than happens with only the furfural which is produced from the xylose and the xylan in the material both during the explosion process and during the heating cycle in the mold.
In the process described above, the dissociated lignocellulosic material forms both the filler and the binder of the molded product. However, the invention is also directed to the use of dissociated lignocellulosic material in association with such materials as sawdust, wood wafers, wood .
~ - 8 -, ~2842~Z
fibers, straw fibers, bagasse fibers, fiber glass fibers, asbestos fibers, carbon fibers, coal, sand and the like. Here the dissociated lignocellulosic material contributes to the molded product as a filler, but is intended to act primarily as 5 a binder, replacing in whole or in part the phenolic resins and similar substances that are commonly used as binders when such materials are molded. If used, these materials should be mixed thoroughly with the dissociated lignocellulosic material prior to molding.
Generally, the higher the proportion of these materials, the softer the molded product. For example, to produce a relatively soft end product, sawdust may be mixed with the dissociated lignocellulosic material to be molded in a ratio of about 4 parts sawdust:l part dissociated lignocellulo~ic material. To make a firmer board, ratios of 1 part or less sawdust:l part dissociated lignocellulosic material may be employed.
It will be apparent to one skilled in the art that various mixtures of these filler materials may be used and various combinations of molding pressure, temperature and dwell time employed to produce a molded product having the characteri~tics desired for a particular application. Also, preservatives, water repellents, fire retardants and the like can be added to the material before molding to produce those ; 25 additional characteristics when required.
It is also possible to mix fertilizer material with the material to be molded, prior to molding. The resulting , - g _ product will per~it the slow release of the fertilizer into the soil, avoiding the rapid run-off and contamination of waterways that often occurs when fertilizer is used by far~ers In the embodiment of the invention that will now be described, the water-soluble substances in the dissociated lignocellulosic material are removed by washing with water.
This removes most of the crosslinking capability of the mixture. The water-soluble substances include acetic acid, glucoronic acid, vanillin, syringaldehyde, plant protein, furfural, inorganic salts, xylose and xylose oligomers~
In order to restore the binding properties of the water-wa~hed, dissociated lignocellulosic material it is necessary to add crosslinking compositions. Typically such compositions would include an acidic catalyst (one or more of the set of mineral acids like sulfuric acid, organic acids like acetic acid, or Lewis acids like zinc chloride) in conjunction with a carbohydrate component consisting of five-carbon sugars, such as those in the water-solubles extracted from the dissociated lignocellulosic material, or six-carbon sugars, their glycosides or short chain oligosaccharides, or a mixture of five-carbon and six-carbon sugars. The active crosslinking agent during the molding process is furfural if the source is a five-carbon sugar, and hydroxymethylfurfural if a six-carbon sugar. Therefore, furfural or hydroxymethylfurfural and the like may replace or supplement the amorphous carbohydrate component in the composition. It is our experience that the -~2 hydroxymethylfurfural is a markedly superior crosslinking material, thus a six-carbon sugar is preferred.
To remove the water-soluble substances, the dissociated lignocellulosic material is washed in a column.
This can be done using a column having an upper opening through which solvent can be added and the dissociated lignocellulosic material put into the column, and a lower opening for the removal of the eluant. (In this specification, "eluant" means a solvent with it~ dissolved or suspended materials which is removed from the column.) The column can conveniently be a cylinder or rectangular tube open at the top and having a drainage ~ystem at the bottom leading to a line and vessel for recovering the eluant. The column can be filled to various heights with dissociated lignocellulosic material, depending on the degree of leaching desired. The inventor has obtained good results with a five foot high column of material, but heights from one foot to over twenty feet have been used successfully.
Water occurs naturally in the lignocellulosic material and more is added by absorption during the first stage of the explosion process. Hence, the water soluble fraction of the dissociated lignocellulosic material i6 already dissolved in the water in the material.
Packing or compressing of the material in the column hampers solvent flow and is therefore to be avoided. Water is then added to the column. The fluid percolates down through the bed, pushing the slug of connate water containing the water solubles ahead of it. The solution which exits at the bottom i28~262 of the column is initially very concentrated, but, because not all channels for fluid flow are swept by the incoming fluid at the same rate due to their different pore or channel sizes, perfect plug flow is not realized and the concentration of dissolved matter falls off exponentially. Water extractable substances comprise approximately 25% by weight of the dissociated lignocellulosic material (on a dry basis). For a five foot high column of loosely filled dissociated lignocellulosic material, more than 99 percent of the water solubles can be removed with only two column volumes of water.
Removal of the water solubles can be accomplished by other methods, such as conventional pulping techniques that involve solvent exchange by massive dilution of the solution already present u~ing very large volumes of water. From the point of view of using the water-washed material for molding, it iB unimportant how the water solubles are removed; however, the column method described herein permits the economical recovery of the water-soluble substances, and is therefore to be preferred.
After water-washing, the dissociated lignocellulosic material is essentially free of chemical reagents which are capable of crosslinking with the lignin. If de~ired, the dissociated lignocellulosic materials may be washed less thoroughly 80 that only some of the crosslinking chemical reagents are removed.
In order to recover the binder qualities of the material, it is necessary to add an appropriate crosslinking .. ... .. , ~
composition. Typically such a composition would include a water-soluble acid (such as sulfuric acid, or acetic acid) together with a 5-carbon or 6-carbon sugar (or a mixture of a 5-carbon and a 6-carbon sugar) in free form or glycosides or in conjugates such as low molecular weight oligosaccharides.
These carbohydrates may be obtained from the water-solubles that were washed from the dissociated lignocellulosic material.
The crosslinking composition, which may contain acid in strengths of 0.2 to 1.0% and sugars in the concentration range of 2-12~, i8 added to the top of the column and allowed to drain through the material. Initially, water from the previous wash exits the column in plug flow. Sufficient composition is added ~uch that the pH of the aqueous eluant exiting the column is as low as the column's entry solution indicating that the acid is leaving the column having wet the entire column's contents equally. At this point, the material is removed from the column, dewatered as much as practical, and then further dried in air or a heated drier. The material can then be milled or ground to produce a fine powder suitable for use as a binder. Prior to molding, the dried material may be mixed with the fibrous aggregate materials, preservatives, water-resistant agents, and flame retardants as required by the specification.
To improve the water resistance of the molded product when water absorbing fillers such as saw dust or wood chips are used, the saw dust or wood chip material can be impregnated with the acid/carbohydrate crosslinking material. This will produce furfural or hydroxymethylfurfural at the binder/filler i . :
~2842~2 interface to create a seal around the filler. In general, the material can be used for molding in the same manner as dissociated lignocellulosic material that has not been subjected to the water-washing process.
In some cases it is desired to use the molded finished product for combustion and an aggregate material such as coal will be incorporated into the product. Here, there may be mixed with the crosslinking composition, before adding it to the column, agents which promote combustion (such as nitrate salts), and flame colouration materials (various inorganic salts depending upon colours desired). Such molded combustibles may ultimately take the form of firelogs or briquet-like chunks.
In the case where neither mineral or organic acids are used in the crosslinking composition, but a Lewis acid salt i8 employed instead, then this salt must be mixed in the dry form and ideally with material having a moisture content lower than l~.
Insofar as the acid behaves as a catalyst, small quantities are used, but the absolute amount required may depend on the nature of the fibrous or aggregate material, and its ability to withdraw the acid from the crosslinking carbohydrate material by capillary action. Typically, a solution of less than 1~ by weight of acid catalyst is required. In whole dissociated lignocellulosic material, the amorphous carbohydrate content is in the range of lS~ to 25%
depending on the input lignocellulosic material. By 128~262 water-washing the dissociated lignocellulosic material and combining with other crosslinking carbohydrate agents, this amount of sugar can be reduced to less than half and the final composition will still serve as an effective binder.
: . ~
MATERIAL AND THE PRODUCT SO PRODUCED
Field of the Invention This invention relates to a method for producing a molded product from dissociated lignocellulosic material and to the product of this process. It also relates to the use of dissociated lignocellulosic material as a binder to replace in whole or in part the phenolic resins which are normally used in the production of plywood, waferboard, oriented strand board, particleboard and other molded products.
Dissociated lignocellulosic material, the starting material for the molding process described herein, is produced by a process of explosive depressurization. The explosion process utilizes lignocellulosic material, which includes such plant growth materials as oat hulls, corn stalks, bagasse, wheat straw, oat straw, barley straw, rice straw and woods of various species. The explosion process comprises the following steps: (l) packing the lignocellulosic materials in a divided, exposed, moist form in a pressure vessel having a valved outlet; (2) with the valve closed, rapidly filling the pressure vessel with steam at a pressure of at least 400 psi to bring substantially all of the lignocellulosic material to a temperature in the range 185C to 240C in less than 60 seconds to thermally soften the lignocellulosic material into a plastic condition; and (3) as soon as the plastic condition has been attained, opening the valved outlet and instantly and 1~84Z6Z
explosively expelling the lignocellulosic material from the pressure vessel to atmosphere. This explosion process breaks the chemical crosslinks between the lignin and hemicellulose and produces a mixture of chemical substances. This mixture, referred to in this specification as "dissociated lignocellulosic material", is a particulate substance having the appearance of potting soil. It consists primarily of cellulose, lignin, aceti~ acid, glucuronic acid, furfural, xylose sugars and xylan, which substances are substantially chemically dissociated from each other. The steam explosion process is further described in Canadian Patent Nos. 1,096,374, 1,141,376 and 1,217,765 to DeLong, and the apparatus used in the process i~ illustrated and described therein.
Summary of the Invention It has previously been conceived that dissociated lignocellulosic material would be used as an animal feedstuff, or as a starting material from which the various chemical component~ of the mixture could be obtained. However, it has now been found that it is possible to recombine the dissociated components of the mixture produced by the process of explosive depressurization of lignocellulosic materials into a heavily crosslinked matrix by subjecting the mixture to heat and pressure in a mold. Various combinations of molding pressure and temperature and mold dwell time may be used to vary the degree of crosslinking of the material and thereby control the strength and density of the end product.
` 1284:;~62 In some embodiments, the water-soluble components of the dissociated mixture are removed and then replaced by an alternative crosslinking composition.
In addition, it has been found that it is possible to make a molded product from a mixture of dissociated lignocellulosic material and various fibrous or woody materials. In this case, the dissociated lignocellulosic material acts as both a filler and a binder. Further, the dissociated lignocellulosic material in acting as a binder can encapsulate a variety of other aggregates such as coal, asphalt, fiber glass, and other non-woody materials.
The invention is therefore directed to a method of molding dissociated lignocellulosic material, with or without the addition of aggregate materials, to form a rigid product. The moisture level of the starting material may be reduced, if necessary, to a level suitable for molding. The material is then packed into a mold which has been preheated to a suitable temperature.
Sufficient presBure iB then applied for a sufficient time to form a rigid product. The molded product may be cured to relieve internal stresses by placing it under pressure in an unheated mold.
The invention is preferably directed to a method of molding dissociated lignocellulosic material comprising preparing the dissociated lignocellulo6ic material by packing lignocellulosic material in a divided, moist form in a pressure vessel having a valved outlet; with the valve closed, rapidly filling the pressure vessel with steam at a pres~ure of at least 400 pBi to bring substantially all of the lignocellulosic material to a temperature in the range of 185 C to 240 C in less than 60 seconds to thermally soften the lignocellulosic material into a plastic condition: as soon as the plastic condition has been attained, opening the valved ,. -- 3 --.Z8426Z
outlet and instantly and explosively expelling the lignocellulosic material from the pressure vessel to atmosphere, wherein the explosive expulsion breaks the chemical cross-link between the lignin and hemicellulose of the lignocellulosic material and produces a mixture of water-soluble chemical substances, whereby di~sociated lignocellulosic material is produced. Next, the said dissociated lignocellulosic material is washed with water to substantially remove the said water-soluble chemical substances.
A cro~s-linking agent and catalyst therefor is added to the washed dis~ociated lignocellulosic material to provide a moldable dissociated lignocellulosic material, said cross-linking agent being ~elected from the group consisting of a five carbon sugar, a ~ix carbon sugar, their glycosides and con~ugates, furfural, and hydroxymethylfurfural, and mixtures thereof, and said catalyst being an acidic cataly~t. The moldable dissociated lignocellulosic mat-rial i~ dried to a water content of about 5% or less. The moldable material iB then packed into a heated, vented mold, wherein sufficient pressure is applied in the range of 20-700 psi for a ~ufficient time in the range of 5 seconds to 30 minutes and at a sufficient temperature in the range of 70 C to 260 C to the ~oldable material in the mold to cause it to form a r~gid product.
The molded product iB then discharged from the mold.
The economics of producing molded board and other products can be improved significantly by the removal of the water soluble fraction of the dissociated lignocellulosic material, and ~eparating the isolated chemicals. This is especially true because the cost of replacement crosslinking chemicals is markedly less than the value of the ---------------------------------------3 a -water-solubles. A preferred method of extracting the water-soluble chemical compounds from dissociated lignocellulosic material comprises placing the material in a column having an upper and a lower opening, adding the water through the top opening, and, without agitating the contents of the column, allowing the solvent to percolate down through the dissociated lignocellulosic material, under the force of gravity, and then removing the solvent and dissociated substances through the lower opening of the column. Aqueous solutions of lignin crosslinking compositions can then be added to the column for wet mixing, by percolation as for water wa8hing. The column contents are then removed, dewatered, then further dried ae nece#sary to lower moisture levels. The resulting product can be molded in the samè manner as that de~cribed herein for dissociated lignocellulosic material that has not been treated in this manner. `~
Detailed Descri tion of the Preferred Embodiment p Dissociated lignocellulosic material freshly produced by the processes described above and in Canadian Patent NOB . 1,096,374, 1,141,376 and 1,217,765 will normally contain excessive moisture, that is, a level of moisture that will hamper the molding process. It has been found that drying the material prior to molding it until the water content is about 5% produces good results. This drying may be carried out by simply exposing the material to air at ambient temperature for a sufficient length of time. The precise water content is not critical to the molding process as it will still work, though less well, if somewhat more or less moisture is present.
Once the water content has been thus reduced, the material may be packed or injected into a mold of the desired size and shape. The molded product has been found to be a suitable substitute for particleboard, waferboard, fibreboard, hardboard, plywood and the like, so the mold may be shaped accordingly.
The molding pressure, temperature and dwell time selected will depend on the type of product desired.
The molding may take place over a wide range of temperatures. The cros~linking reactions that occur during molding take place more quickly at higher temperatures. It has been found that as the molding temperature is increased, the density of the product increases at constant pressure.
Temperatures in the range of about 70C to 260C have been found useful in producing a general-purpose product. The desired molding temperature may be achieved by preheating the mold, and in this specification "molding temperature" means the temperature of the mold. Whether all of the material in the mold is heated to this temperature depends on the thickness of the mold and the dwell time. Alternatively, it is pos6ible, when molding large volume products, for instance, railroad ties or structural components, to preheat the starting materials rather than, or in addition to, heating them in the mold. Preheating the material should ...
., . , . . . ~ .
128~Z
be carried out in a closed vessel to prevent the escape of furfural and the like.
The molding pressure may also be selected from a wide range of pressures, depending on the desired density of the molded product. It has been found that molding pressures from about 20-1500 psi may be used. Pressures in the range of 600-700 psi can be used to produce a good general-purpose product.
To make a molded product similar to cork, a molding temperature of about 70-110C and a molding pressure of about 20-90 psi may be used. Such a product might be used to encapsulate slow release nutrients in a biodegradeable planting pot.
It is possible to produce a low density molded product having increased toughness and water resistance by molding at relatively low temperature (e.g. 70-120C) and then applying a mold platen heated to about 300C for a short time.
This plasticizes the cellulose at the surface of the molded product.
To make a molded product having a density similar to that of furniture board (medium density), a molding temperature of about 120-145C and a molding pressure of about 100-700 psi may be used.
To produce a high density molded product, a molding temperature of about 120-165C and a molding pressure of about 700-1500 psi may be used. Using suitably high pressures and temperatures it is possible to produce a very high density , lZE~
material which could be used, for example, to replace slate in pool table tops. Such a product is so dense that a .22 caliber rifle bullet, fired from close range, will not penetrate beyond 4 or 5 mm.
The dwell time in the mold may vary over a wide range depending on the thickness of the board and the desired density of the product. The material acts as an insulator; a thicker molded product requires more time for the heat from the mold to fully penetrate it and for it to cure after crosslinXing occurs. To achieve uniform crosslinking across the thickness of the product, longer dwell times can be used, and the temperature may be reduced accordingly. It has been found that for a given temperature, pressure and thickness, increased dwell time results in increased product density. Dwell times in the range of about 5 seconds to 30 minutes have been used with success.
The mold ~hould be vented to permit the continuous escape of steam and other gases produced during molding.
In some cases, the molded material should be permitted to cure after molding to relieve internal stresses.
For high density material, a longer cure time is required and it may be desirable immediately after molding to transfer the molded product to an unheated mold at pressures similar to the molding pressure to allow the product to cure.
When dissociated lignocellulosic material is molded in the manner described, the lignin crosslinks with furfural, fatty acids and xylan. As the molding temperature is increased, up to about 240C, the acids in the dissociated lignocellulosic material react at an increasing rate with the xylan and xylose sugars to produce higher concentrations of furfural, which will in turn increase the degree of crosslinking with the lignin, thereby producing a denser and stronger product. By controlling these reactions, one can vary the strength, water resistance and density of the molded product.
If it is desired to increase the speed of the reaction or lower the molding temperature, or both, an acid catalyst (such as a mineral acid, an organic acid, or a Lewis acid or a mixture thereof) can be added to increase the rate and degree of hydrolysis of the xylan and xylose sugars to furfural, which in turn increases the degree of crosslinking with the lignin. It i8 also possible to add paraformaldehyde, six carbon sugars either free or combined as glycosides or as short chain oligosaccharides, or some other croæslinking agent to the dissociated lignocellulosic material to produce a higher degree of crosslinking than happens with only the furfural which is produced from the xylose and the xylan in the material both during the explosion process and during the heating cycle in the mold.
In the process described above, the dissociated lignocellulosic material forms both the filler and the binder of the molded product. However, the invention is also directed to the use of dissociated lignocellulosic material in association with such materials as sawdust, wood wafers, wood .
~ - 8 -, ~2842~Z
fibers, straw fibers, bagasse fibers, fiber glass fibers, asbestos fibers, carbon fibers, coal, sand and the like. Here the dissociated lignocellulosic material contributes to the molded product as a filler, but is intended to act primarily as 5 a binder, replacing in whole or in part the phenolic resins and similar substances that are commonly used as binders when such materials are molded. If used, these materials should be mixed thoroughly with the dissociated lignocellulosic material prior to molding.
Generally, the higher the proportion of these materials, the softer the molded product. For example, to produce a relatively soft end product, sawdust may be mixed with the dissociated lignocellulosic material to be molded in a ratio of about 4 parts sawdust:l part dissociated lignocellulo~ic material. To make a firmer board, ratios of 1 part or less sawdust:l part dissociated lignocellulosic material may be employed.
It will be apparent to one skilled in the art that various mixtures of these filler materials may be used and various combinations of molding pressure, temperature and dwell time employed to produce a molded product having the characteri~tics desired for a particular application. Also, preservatives, water repellents, fire retardants and the like can be added to the material before molding to produce those ; 25 additional characteristics when required.
It is also possible to mix fertilizer material with the material to be molded, prior to molding. The resulting , - g _ product will per~it the slow release of the fertilizer into the soil, avoiding the rapid run-off and contamination of waterways that often occurs when fertilizer is used by far~ers In the embodiment of the invention that will now be described, the water-soluble substances in the dissociated lignocellulosic material are removed by washing with water.
This removes most of the crosslinking capability of the mixture. The water-soluble substances include acetic acid, glucoronic acid, vanillin, syringaldehyde, plant protein, furfural, inorganic salts, xylose and xylose oligomers~
In order to restore the binding properties of the water-wa~hed, dissociated lignocellulosic material it is necessary to add crosslinking compositions. Typically such compositions would include an acidic catalyst (one or more of the set of mineral acids like sulfuric acid, organic acids like acetic acid, or Lewis acids like zinc chloride) in conjunction with a carbohydrate component consisting of five-carbon sugars, such as those in the water-solubles extracted from the dissociated lignocellulosic material, or six-carbon sugars, their glycosides or short chain oligosaccharides, or a mixture of five-carbon and six-carbon sugars. The active crosslinking agent during the molding process is furfural if the source is a five-carbon sugar, and hydroxymethylfurfural if a six-carbon sugar. Therefore, furfural or hydroxymethylfurfural and the like may replace or supplement the amorphous carbohydrate component in the composition. It is our experience that the -~2 hydroxymethylfurfural is a markedly superior crosslinking material, thus a six-carbon sugar is preferred.
To remove the water-soluble substances, the dissociated lignocellulosic material is washed in a column.
This can be done using a column having an upper opening through which solvent can be added and the dissociated lignocellulosic material put into the column, and a lower opening for the removal of the eluant. (In this specification, "eluant" means a solvent with it~ dissolved or suspended materials which is removed from the column.) The column can conveniently be a cylinder or rectangular tube open at the top and having a drainage ~ystem at the bottom leading to a line and vessel for recovering the eluant. The column can be filled to various heights with dissociated lignocellulosic material, depending on the degree of leaching desired. The inventor has obtained good results with a five foot high column of material, but heights from one foot to over twenty feet have been used successfully.
Water occurs naturally in the lignocellulosic material and more is added by absorption during the first stage of the explosion process. Hence, the water soluble fraction of the dissociated lignocellulosic material i6 already dissolved in the water in the material.
Packing or compressing of the material in the column hampers solvent flow and is therefore to be avoided. Water is then added to the column. The fluid percolates down through the bed, pushing the slug of connate water containing the water solubles ahead of it. The solution which exits at the bottom i28~262 of the column is initially very concentrated, but, because not all channels for fluid flow are swept by the incoming fluid at the same rate due to their different pore or channel sizes, perfect plug flow is not realized and the concentration of dissolved matter falls off exponentially. Water extractable substances comprise approximately 25% by weight of the dissociated lignocellulosic material (on a dry basis). For a five foot high column of loosely filled dissociated lignocellulosic material, more than 99 percent of the water solubles can be removed with only two column volumes of water.
Removal of the water solubles can be accomplished by other methods, such as conventional pulping techniques that involve solvent exchange by massive dilution of the solution already present u~ing very large volumes of water. From the point of view of using the water-washed material for molding, it iB unimportant how the water solubles are removed; however, the column method described herein permits the economical recovery of the water-soluble substances, and is therefore to be preferred.
After water-washing, the dissociated lignocellulosic material is essentially free of chemical reagents which are capable of crosslinking with the lignin. If de~ired, the dissociated lignocellulosic materials may be washed less thoroughly 80 that only some of the crosslinking chemical reagents are removed.
In order to recover the binder qualities of the material, it is necessary to add an appropriate crosslinking .. ... .. , ~
composition. Typically such a composition would include a water-soluble acid (such as sulfuric acid, or acetic acid) together with a 5-carbon or 6-carbon sugar (or a mixture of a 5-carbon and a 6-carbon sugar) in free form or glycosides or in conjugates such as low molecular weight oligosaccharides.
These carbohydrates may be obtained from the water-solubles that were washed from the dissociated lignocellulosic material.
The crosslinking composition, which may contain acid in strengths of 0.2 to 1.0% and sugars in the concentration range of 2-12~, i8 added to the top of the column and allowed to drain through the material. Initially, water from the previous wash exits the column in plug flow. Sufficient composition is added ~uch that the pH of the aqueous eluant exiting the column is as low as the column's entry solution indicating that the acid is leaving the column having wet the entire column's contents equally. At this point, the material is removed from the column, dewatered as much as practical, and then further dried in air or a heated drier. The material can then be milled or ground to produce a fine powder suitable for use as a binder. Prior to molding, the dried material may be mixed with the fibrous aggregate materials, preservatives, water-resistant agents, and flame retardants as required by the specification.
To improve the water resistance of the molded product when water absorbing fillers such as saw dust or wood chips are used, the saw dust or wood chip material can be impregnated with the acid/carbohydrate crosslinking material. This will produce furfural or hydroxymethylfurfural at the binder/filler i . :
~2842~2 interface to create a seal around the filler. In general, the material can be used for molding in the same manner as dissociated lignocellulosic material that has not been subjected to the water-washing process.
In some cases it is desired to use the molded finished product for combustion and an aggregate material such as coal will be incorporated into the product. Here, there may be mixed with the crosslinking composition, before adding it to the column, agents which promote combustion (such as nitrate salts), and flame colouration materials (various inorganic salts depending upon colours desired). Such molded combustibles may ultimately take the form of firelogs or briquet-like chunks.
In the case where neither mineral or organic acids are used in the crosslinking composition, but a Lewis acid salt i8 employed instead, then this salt must be mixed in the dry form and ideally with material having a moisture content lower than l~.
Insofar as the acid behaves as a catalyst, small quantities are used, but the absolute amount required may depend on the nature of the fibrous or aggregate material, and its ability to withdraw the acid from the crosslinking carbohydrate material by capillary action. Typically, a solution of less than 1~ by weight of acid catalyst is required. In whole dissociated lignocellulosic material, the amorphous carbohydrate content is in the range of lS~ to 25%
depending on the input lignocellulosic material. By 128~262 water-washing the dissociated lignocellulosic material and combining with other crosslinking carbohydrate agents, this amount of sugar can be reduced to less than half and the final composition will still serve as an effective binder.
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Claims (25)
1. A method of molding dissociated lignocellulosic material comprising the steps of:
(A) preparing the dissociated lignocellulosic material by:
(1) packing lignocellulosic material in a divided, moist form in a pressure vessel having a valved outlet, (2) with the valve closed, rapidly filling the pressure vessel with steam at a pressure of at least 400 psi to bring substantially all of the lignocellulosic material to a temperature in the range of 185°C to 240°C in less than 60 seconds to thermally soften the lignocellulosic material into a plastic condition, (3) as soon as the plastic condition has been attained, opening the valved outlet and instantly and explosively expelling the lignocellulosic material from the pressure vessel to atmosphere, and wherein the explosive expulsion breaks the chemical cross-link between the lignin and hemicellulose of the lignocellulosic material and produces a mixture of water-soluble chemical substances, whereby dissociated lignocellulosic material is produced;
(B) washing the said dissociated lignocellulosic material with water to substantially remove the said water-soluble chemical substances;
(C) adding a cross-linking agent and catalyst therefor to the washed dissociated lignocellulosic material to provide a moldable dissociated lignocellulosic material, said cross-linking agent being selected from the group consisting of a five carbon sugar, a six carbon sugar, their glycosides and conjugates, furfural, and - Page 1 of Claims -hydroxymethylfurfural, and mixtures thereof, and said catalyst being an acidic catalyst;
(D) drying the moldable dissociated lignocellulosic material to a water content of about 5% or less;
(E) packing the moldable material into a heated, vented mold;
(F) applying sufficient pressure in the range of 20-700 psi for a sufficient time in the range of 5 seconds to 30 minutes and at a sufficient temperature in the range of 70 C to 260 C to the moldable material in the mold to cause it to form a rigid product; and (G) discharging the molded product from the mold.
(A) preparing the dissociated lignocellulosic material by:
(1) packing lignocellulosic material in a divided, moist form in a pressure vessel having a valved outlet, (2) with the valve closed, rapidly filling the pressure vessel with steam at a pressure of at least 400 psi to bring substantially all of the lignocellulosic material to a temperature in the range of 185°C to 240°C in less than 60 seconds to thermally soften the lignocellulosic material into a plastic condition, (3) as soon as the plastic condition has been attained, opening the valved outlet and instantly and explosively expelling the lignocellulosic material from the pressure vessel to atmosphere, and wherein the explosive expulsion breaks the chemical cross-link between the lignin and hemicellulose of the lignocellulosic material and produces a mixture of water-soluble chemical substances, whereby dissociated lignocellulosic material is produced;
(B) washing the said dissociated lignocellulosic material with water to substantially remove the said water-soluble chemical substances;
(C) adding a cross-linking agent and catalyst therefor to the washed dissociated lignocellulosic material to provide a moldable dissociated lignocellulosic material, said cross-linking agent being selected from the group consisting of a five carbon sugar, a six carbon sugar, their glycosides and conjugates, furfural, and - Page 1 of Claims -hydroxymethylfurfural, and mixtures thereof, and said catalyst being an acidic catalyst;
(D) drying the moldable dissociated lignocellulosic material to a water content of about 5% or less;
(E) packing the moldable material into a heated, vented mold;
(F) applying sufficient pressure in the range of 20-700 psi for a sufficient time in the range of 5 seconds to 30 minutes and at a sufficient temperature in the range of 70 C to 260 C to the moldable material in the mold to cause it to form a rigid product; and (G) discharging the molded product from the mold.
2. A method according to claim 1, wherein the mold is preheated to a temperature between approximately 70°-260°C and wherein a mold platen preheated to approximately 300°C is applied to the molded product after it is formed.
3. A method according to claim 1, wherein a molded product having a density like that of corkboard is desired, and the mold is preheated to a temperature between approximately 70°-110°C, and a pressure between approximately 20-90 psi is applied to the material in the mold.
4. A method according to claim 1, wherein a molded product having a density like that of furniture board is desired, and the mold is preheated to a temperature between approximately 120°-145°C, and a pressure between approximately 100-700 psi is applied to the material in the mold.
- Page 2 of Claims -
- Page 2 of Claims -
5. A method according to claim 1, wherein a preservative substance is added to the dissociated lignocellulosic material prior to molding.
6. A method according to claim 1, wherein a water repellent material is added to the dissociated lignocellulosic material prior to molding.
7. A method according to claim 1, wherein a fire retardant material is added to the dissociated lignocellulosic material prior to molding.
8. A method according to claim 1, wherein the said acidic catalyst selected from the group comprising a mineral acid, an organic acid and a Lewis acid.
9. A method according to claim 1, wherein the molded product is transferred from the hot mold to an unheated mold under similar pressure to allow the molded product to cure.
10. A method of producing a molded product according to claim 1, including the steps of:
(a) mixing together the dissociated lignocellulosic material and filler materials selected from the group comprising wood wafers, wood fibers, straw fibers, bagasse fibers, sawdust, fiber glass fibers, asbestos fibers, carbon fibers, fertilizer, coal and sand.
- Page 3 of Claims -
(a) mixing together the dissociated lignocellulosic material and filler materials selected from the group comprising wood wafers, wood fibers, straw fibers, bagasse fibers, sawdust, fiber glass fibers, asbestos fibers, carbon fibers, fertilizer, coal and sand.
- Page 3 of Claims -
11. A method according to claim 10, wherein the dissociated lignocellulosic material contains excessive moisture and the moisture content is reduced to a suitable level of about 5% or less before molding.
12. A method according to claim 10, wherein the selected material is sawdust, which is used in a proportion of 4 parts or less of sawdust; 1 part dissociated lignocellulosic material.
13. A method according to claim 10, wherein the mold is preheated to a temperature between approximately 70°-260°C.
14. A method according to claim 13, wherein a mold platen preheated to approximately 300°C, is applied to the molded product after it is formed.
15. A method according to claim 10, wherein a preservative substance is added to the material to be molded prior to molding.
16. A method according to claim 10, wherein a water repellent material is added to the material to be molded prior to molding.
17. A method according to claim 10, wherein a fire retardant material is added to the material to be molded prior to molding.
18. A method according to claim 10, wherein the molded product is transferred from the hot mold to an unheated mold under similar pressures to allow the molded product to cure.
- Page 4 of Claims -
- Page 4 of Claims -
19 19. A method according to claim 10, wherein the crosslinking agent and catalysts are impregnated into the filler material prior to molding.
20. The product produced by the method of claim 10.
21. A method according to claim 1, wherein the said crosslinking agent is selected from the group comprising 5-carbon and 6-carbon sugars in free or combined form.
22. A method according to claim 1, wherein the said crosslinking agent comprises hydroxymethylfurfural.
23. A method according to claim 1, wherein the said crosslinking agent comprises furfural.
24. A method according to claim 1, wherein the concentration of the acidic catalyst in the crosslinking agent is in the range of about 0.2% to 1.0%, and the concentration of the crosslinking agent in the crosslinking agent/catalysts composition is in the range of approximately 2% to 12%.
25. The product produced by the method of claim 1.
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CA 538105 CA1284262C (en) | 1987-05-27 | 1987-05-27 | Method of molding using dissociated lignocellulosic material and the product so produced |
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Cited By (1)
Publication number | Priority date | Publication date | Assignee | Title |
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CN107366196A (en) * | 2017-06-30 | 2017-11-21 | 常州市协旺纺织品有限公司 | A kind of preparation method of non-glue fibre board |
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Cited By (2)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
CN107366196A (en) * | 2017-06-30 | 2017-11-21 | 常州市协旺纺织品有限公司 | A kind of preparation method of non-glue fibre board |
CN107366196B (en) * | 2017-06-30 | 2019-05-07 | 杭州海豪实业有限公司 | A kind of preparation method of non-glue fibre board |
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