CA1064809B - Lumber products formed of wood fibers and method of manufacturing these products - Google Patents
Lumber products formed of wood fibers and method of manufacturing these productsInfo
- Publication number
- CA1064809B CA1064809B CA 325288 CA325288A CA1064809B CA 1064809 B CA1064809 B CA 1064809B CA 325288 CA325288 CA 325288 CA 325288 A CA325288 A CA 325288A CA 1064809 B CA1064809 B CA 1064809B
- Authority
- CA
- Canada
- Prior art keywords
- inch
- lumber
- lumber product
- strands
- modulus
- 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
Classifications
-
- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02W—CLIMATE CHANGE MITIGATION TECHNOLOGIES RELATED TO WASTEWATER TREATMENT OR WASTE MANAGEMENT
- Y02W30/00—Technologies for solid waste management
- Y02W30/50—Reuse, recycling or recovery technologies
- Y02W30/62—Plastics recycling; Rubber recycling
Landscapes
- Dry Formation Of Fiberboard And The Like (AREA)
- Processing And Handling Of Plastics And Other Materials For Molding In General (AREA)
- Separation, Recovery Or Treatment Of Waste Materials Containing Plastics (AREA)
Abstract
A B S T R A C T
A discrete dimensioned structural lumber product is disclosed which has greater strength to density ratio than previous structural lumber product. The product comprises adhesively bonded, substantially straight wood strands having lengths of at least 12 inches, average widths of 0.05 inch to 0.25 inch, and average thickness of 0.05 inch to 0.5 inch, the strands being disposed, side by side length-wise of the lumber product in substantially parallel relation-ship with adhesive bonding adjacent strands but with sub-stantially no straight glue lines extending from one surface to the other of the product, the total amount of adhesive resin solids in the lumber product being from 1% to 5% by weight, the modulus of elasticity for a given dry wood density coming within predetermined boundaries.
A discrete dimensioned structural lumber product is disclosed which has greater strength to density ratio than previous structural lumber product. The product comprises adhesively bonded, substantially straight wood strands having lengths of at least 12 inches, average widths of 0.05 inch to 0.25 inch, and average thickness of 0.05 inch to 0.5 inch, the strands being disposed, side by side length-wise of the lumber product in substantially parallel relation-ship with adhesive bonding adjacent strands but with sub-stantially no straight glue lines extending from one surface to the other of the product, the total amount of adhesive resin solids in the lumber product being from 1% to 5% by weight, the modulus of elasticity for a given dry wood density coming within predetermined boundaries.
Description
648~9 This invention relates to a method of converting lignocellulosic materials into use~ul products wi~hout waste, and products of this method.
In the past th~re has been a great deal o~ waste in the utilization of lignocellulosi~ materials, and particularly wood. During logging operations, the limbs of trees are cut o~f and are burned or left around to decay. In the mills a large percentage of the wood is lost in sawdust, trimmings or cuttings, and the like. Soma effort has been made to reduce the amount of sawdust, and to convert the trimmings and cuttings into chips for use in the manufacture of pulp. However, the waste is still very great. In addition to this, many small trees are left bahind in logging operations since it is uneconomical to cut and handle them, and many species o~ trees and shrubs are not used at all since they are not considered to be suitable for the manufacture of lumber. ~ -Many sources of lignocellulosic ~iber are not commer~
cially utilized for construction purposes because of inherent characteristics that make them economically unattractive, such as small diameter, low density, low resistance to decay, poor grain properties, and poor strength properties. In many areas or countries such weed species can constitute a significant, if not the major, part of the available wood resource. In British Columbia, Canada, Western red cedar constitutes a significant part of the coastal ~orest, something o~ the order of 22%. -However, its strength properties and pulp yield characteristics are such as to make it of little commercial value compared to such contiguous species as Douglas ~ir and hemlock. In some tropical areas, such as Malasia, the desired species may occur at such a low frequency per acre as to allow for only the most ; . . .
primitive segregation and cutting operations. In other areas, the dominaDt vegetation consists of bushes, reeds, and other ~ -$
-~6~8~
woody plants, not suited ~or conventional conversion into con-struction products. In addition to this non utilization o~ non-processed wood ~iber, is the very :Large amount of waste wood generated in the most highly automated, high yield log conver-sion systems. It is estimated that the waste wood amounts to about 45% of the total tree, taking into account all low value uses of residues for fuel and soil conditioning.
The present invention contemplates the production of construction materials, such as lumber, various types of panels, and the production of pulp, from any source of lignaceous cellulosic fiber. The general idea is to break down any ligno-cellulosic material into slivers, fibers or strands by any suit-able means, such as by slicing, crushing, shaving, peeling or the like. The aim in the breakdown is generally to produce as long fibers as possible. During the breakdown there are pro-duced small or fine particles, medium length strands and long length strands. The fine particles are utilized in the manu-facture of pulp and/or fiber boards, the medium lengths are used -~
in the manufacture of strand boards, chip boards and/or particle boards, and the long lengths are manufactured into dimensionedlumber and/or board products. It is this production of $he di-mentioned lumber that makes the process or method practical, since the lumber is engineered to give desired characteristics, regardless of the type of the basic lignocellulosic material.
An important feature of this process is the ~act that it can be operated to produce the various products in accordance with the markat demand. If the demand for pulp is up and fol tha other products is down, more of the material can be converted into short lengths or particles. on the other hand, i~ the demand `~
for strand boards, chip boards or particle boards is up, the percentage of medium lengths can be increased at the expense of the long lengths. Howeuer, if the demand ~or lumber is up, as 3~ - 2 -'i,3 ~648~
many long lengths are produced as possible. As the lumber pro-ducts have the highest com~ercial value, it is usually desirable to aim to produce the highest possible amount of long length fibers.
~he general advantages resulting from this process carry on into the dimensioned lumber field. The lumber can be ~ ~
produced in size and characteristics in accordance with the -market demand. For exampleJ if there is a ralatively great de-mand for two by fours, a large percentage of the long fibers can be converted into these. On the other hand, if other boards or timbers are particularly required, the production can be concen- `
trated on these. - -This is a concept that caD revolutionize the wood ~ ~-product producing industry. Heretofore9 the trees were converted ~ ; ~
: into the best or highest paying products possible. However, with ~ -;
the prior production methods, the control of the type o~ lumber produced-is very limited so-that if a large number of, say, two ~
by fours are in demand, the operation will also result in ths production of large number of boards or lumber of different sizes ~ ;
:- .
which may not be required at the moment. Thus, a producer can end up with a large inventory of boards not needed at the moment when he tries to fulfill the sudden demand for boards or lumber ~ ;~
of other dimensions.
The main product of this process is the dimensioned lumber. It is possible to make any number of boards of the same or dif~erent dimensions, and these can be given desired characteristics regardless of the original source of matsrial.
The term "board" as used herein is intended to include all kinds of boards, timbers and lumber of any desired dimensions.
As stated above, the lignocellulosic materials can be broken down in any desired manner. The fibers are separated by length into those fractions most suitable for the required end 3 _ , ,-: ~, : . , .:.
~0~;~809 use, treated with such additives as may be needed to give the required resistance to decay and ~ire, dried either before or after the addition of adhesives, or they can be left undried, and then combined with a binding material, and, possibly, com-bined with non-cellulosic fibers, such as glass, metals and plastics, and formed into a mass and either cast, molded, extruded or pressed into the desired end product.
Any method of breaking up the raw lignacious cellulos material into fibers will develop a wide range of fiber lengths and diameters. The most profitable and useful end use is a lum-ber product suitable for CODstruCtiOn purposes, followed by a strand panel board with strength properties similar to plywood, ;~
chip boards, and lastly the particle board for essentially non~
structural usas. A possible segregation of the particles in the -~
following lengths for the specified purposes is as follows: -Dimensioned lumbar 6" to 4 feet Strand board 2" to 6"
Chip board ~" to 2"
Particle board Less than ~"
Pul~ Less than ~"
An excess of any ~raction can be broken down into lower lengths.
All of the products than can be produced by the present process, excepting the dimensioned lumber, are produced by known processas.
~ owever, this invention contemplates tha production of dimensioned lumber from any lignacious cellulosic ~aterial.
Use of this concept will significantly affect the conventional forestry practices from the present emphasis upon mer~hantable lumber to that of a maximum yield of woody fiber per acre, and will result in a true tree farming approach utilizing fast grow-ing, short cycle, high vield species rather than the present slow growing long cycle species.
_ 4 . . .
~1~6~
As stated above, one of the advantages of the present process is the utilization on non-commercial "weak" specias in the production of good grade lumber. Some species of wood, such as aspen and alder, are considered low value species and little used for commercial purposes because of their very low yield of merchantable lumber per/unit/acre of logs. This low yield is due to the small size of log, the low strength properties and the incidents of compr~ssion and tension wood causing warp-ing and twisting. Utilization of these species in the manufacture of the various products in accordance with this process makes very large volumes of wood available for commercial use. A ~;
large percentage of the wasts from the standard logging sawmill and manufacturing procadures can be converted to dimensioned lumber having more value than the use of these materials for pulping. Smaller trees and shorter harvesting cycles can be used in order to give an increase in wood yield from given acreag~
The present process lsnds itself to the production of a uniform density material with guaranteed strength and durabil-ity properties, free from the inherent defects of normal lumber-knots, splits and density variations.
The strength properties of wood increase with increas-ing density. All species for which data is at present available ;
show this increaseO This relationship of strength properties to density is of major commercial significance in the use of lumber, - ;~
resulting in allowable design stress values significantly below that of the average strength values of the species involved.
Variations in the density of wood are due to variations in its structure and the presence of extraneous constituents. The structure is characterized by the proportional amoLInts of different cell types, such as fibers, tracheids, vessel ducts, and rays, and by their dimensions. Hereditary tendencies, physiological and mechanical factors, position in the tree trunk, ; - 5 -1064~
all affect the density of the wood. The relationships are very complex and not well understood. The result is a wide variation in density within any ona species which can be as large as a factor of 2 to 2~. The dimensionad lumber of the present inven- -tion overcome these inherent variations in normal lumber proper-ties.
By choice of compressed density, resin solids and strand geometry, particular properties can be imparted to an-gineered or dimensioned lumber. A range o~ lumber-like products can thus be engineered to use specifications, and these are com-petitive on an engineering basis with solid lumber, metals, plastic and concrete.
If desired, fire retardants, preservatives, colorants and the like can be added to the particles or strands used in the production of the dimensioned lumber. `
The engineered or dimensioned lumber produced by this process-is-made-up of callulosic-~ibers-or strands ranging from about 6 inches to about 4 feet in length, and having a width of about 0.05 to 0.25 and a thickness of about 0.05 to about 0.5 inch. These fibers are coated with adhesive in standard coating equipment, such as drum applicators or curtain applicators. A
water insoluble structural glue, such as phenol formaldshyde, is used to coat the fibers, although any suitable type of glue can be used. The coated fibers are arranged in bundles and then subjected in presses to pressures sufficient to produce a fin- ; ~
ished product having predetermiDed dimensions and density. The ~ ;
pressures and temperatures used are sufficient to produce the desired density. For e~ample, pressuras of from about 100 to about 400 psi have been found to be suitable, and the ~ibers ara subjected to a high enough temperature for a time sufficient to produce a temperatura of at least 212F within the product. For example, a temperature of 300F for up to 30 minutes has pro-'` , . . .
106480~
duced desirable products, but this time can be reduced. Ifhigh ~requency energy is used for providing the heat, the press-ing can be done in around one minute.
Referring to the accompanying drawings, Figure 1 diagrammatically illustrates apparatus ~or carrying out the method in accordance with this invention, Figure 2 illustrates one way of producing lignocellu- ;
losic material to useful fiber lengths, Figure 3 illustrates a piece o~ dimensioned lumber made in accordance with this invention, Figure 4 is a graph comparing the modulas of elastici$y -~to density in engineered lumber, Figure 5 is a graph illustrating the relationship o~
the resin solids used relative to the modulas of elasticity, Figure 6 is a graph illustrating the ef~ect of strand or fiber length, Figure 7 dia_rammatically illustrates the direction of springback oi some forms of dimensioned lumber, and .
Ei~gures 8, 9 and 10 ara graphs illustrating specified charactsristics of the dimensioned lumber.
Figure 1 diagrammatically illustrates apparatus for carrying out the present invention. The lignocellulosic material such as logs, roots, branches, waste wood, shrubs and the like, are ~ed to a brsakdown device 10 where they are sliced, crushed or otherwise broken d~wn into fibers. It is desirable to produce long strands or fibers for USQ in the manufacture of dimensioned lumber. For example, these can be f~om 6 inches to 4 feet in length, 0.05 to 0.~5 inch in width, and 0.1 to 0.5 inch in thick- ~ -ness. In the general breakdown there will be fibers o~ medium length and very short fibers. The general aim is to produce as many long fibers as possible since these are used in the produc-tion of dimensioned lumber which is ths most valuable product , ~0648~g for the market. It is at this point that the final output of the process can be controlled. The short or fine fibers are used for pulping or fiber boards, while the medium length fibers are used in the manufacture of strand boards, chipboards, particle boards and the like. If the demand for pulp and/or these differ-ent boards goes up relative to the demand for dimensioned lumber, more short fibers and/or medium fibers are produced at the break-down device 10.
The fibers from device 10 go to a separator 12 which separates out the short length fibers to be used in the manu-facture of fiber boards or pulp, or for any other purpose for which short length fibers are suitable.
Some or all of the medium length and long length fibers may be directed to an applicator 14 where they are treated with fire proofing material, insecticides, preservatives, stains or the like before being sent on to a dryer 16. Some or all of these fibers can be by-passed directly to dryer 16. The moisture content of the fibers is reduced to the desired extent for the ~-~
production of the final product. If desired, the medium length fibers may be separated ~rom the long length fibers before they reach dryer 16, in which case the different groups of fibers would be separately dried in accordance with the demand. ~
In this example, the fibers from dryer 16 go to a ?
separator 18 which separates them into the long fibsrs and the medium fibers. The long fibers go to a glue applicator 20 which may be in any desired form, such as a drum applicator or a curtain applicator, and from here they go to a prass or mold 22 which presses them under heat and pressure into lumber of desired dimensions and the desired density. There is another control at this point, that is, the dimensions of the lumber produ~ed is in accordance with the demand. For example, if there is a great demand for two by fours, the percentage of these would be high . ~.
ILCl 6~
relative to boards of other dimensions ~or which the demand was not so ~reat. Although this diagram merely shows one press or mold 22, it is obvious that there cDuld be several presses so that boards of different dimensions could be made at the same time.
Separator 18 separates out the medium fibers from the long fibers, and these are directed to a glue applicator 24, whence they travel to a press 26 which produces the type of boards required, such as strand boards, chipboards, particle-boards, and the like. Here again, although one press only is shown, there may be several. In addition to this, the "press"
is intended to mean any system necessary to produce the desired particle-type board.
What actually happens in this method or process is that ths original material is broke~ down into fibers of di~fer-ent lengths, and then these are reconstituted into dimensioned lumber, particle-type boards, pulp and the like. With this ~ -arrangement, there is no waste. In addition, the process is geared to handle all of the particles produced from the original material, regardless of their length, and regardless of whe~her the lengths are accidentally or intentionally produced.
Figure 2 illustrates one way of reducing lignocellu-losic material, such as a log, to useful fiber leDgths. A log 30 is cut by suitable slicing material into slices 31, and then each slice 31 is cut into relatively thin pieces 32 which extend the length of slice 31. Each piece 32 has a desired width, such as 0~05 to 0.25 inch. Then each piece is cut transversely into strands 33 of desired thicknesses, for example, 0.05 to 0.5 inch.
These preferably are the length of the pieces 32. It is obvious that during this slicing or cutting process~ there will be a lot of fibers which are considerably shorter than the strands or iibers 33. As stated above, the medium length fibers can be used .
_ g _ ' i~6~8~
in the production of particle-type boards, and the short fibers can be used in the production of pulp, or ~or other desired purposes. ;
Figure 3 illustrates a piece of dimensioned lumber or board 38 made up of strands or fibers 33. These strands or fibers, after being coated with a suitable adhesive, are laid side by side and then pressed under heat and pressure into a board of desired dimensions, such as, for axample, a two by four.
These strands can extend the full length o~ the board, as shown, 1~ or each strand may extsnd only part way through-out the length of the board. The strands are laid side by side, but as these are of random dimensions and lengths, they interlock to a degree so that there are no straight glue lines extending from one sur-face to the other of the board. The density of the finished pro-duct is determined by the amount of pressure and heat used in the press. This is another advantage of this method, that is the boards produced can be not only of desired dimensions, but -they can be made in desired densities in accordance with the ~-purpose for which they are designsd. In addition, it is po~sible to subject the long strands to a continuous pressing operation so ;~
that boards of any desired length can be produced. As the strands are interlaced to a certain degree, any length of board can be produced.
Although the lengths of the strands for dif~erent purposes can vary, the following is an indication of practical leDgths for the different pUrpQSeS~
Engineered lumber 6 inches to 48 inches `~
Strand board 2 inches to 6 inches Chipboard ~ inch to 2 inches ~ -Particle board Less than a ~ inch Pulp chips and sawdust ~0648~
In the manufactured or dimensioned lumber, the re~
sistance of the glueline to horizontal shearing ~orces is pro-portional to tha length of the fiber to which the stress îs being transmitted to the glueline. It i5 also inversely proportional to the thickness of the glueline wh:ich is rel~ted to ths ~iber thickness to the extand that the degree to which a "closest packing" condition of the fibers is achieved. The optimum resin ;~;
content for any set of variables is that at which maximum strength properties are obtained, all else being equal. Theoretically, too little resin gives insufficient coverage, and too much resin causes thick gluelines, thereby reducing strength. Variables affecting the optimum resin content are the fiber geometry and the pressure applied during the curing of the resin.
The thing that makes this process an economical success is the fact that engineered or dimensioned lumber can be made with equal strength to that of top structural grade Douglas fir lumber. This can be either on an equal density basis using ~- ;
optimum fiber geometry ~nd adhesive content, or it can be on an ;
increased density basis using less favourable fiber geometry and adhesive content. The strength of the engineered lumber is essentially independent of the raw material species, but in-creased "springback" with moisture absGrption occurs with the ~`
use of low dansity species. The durability and stability are mainly controlled by adhesive content.
Strength-Density Relationship for Engineered Lumber Figure 4 shows plots of the strengths (Modulus of Elasticity,MOE) against compressed density for engineered lumber made from 1/8" Douglas fir strands under the following con-ditions:
Strand length 6", 12", 24"
Resin solids 1, 3, 5% (Phenol formaldehyde solids to dry wood percentage) Press pressures 100 to 400 psi ~ -- 11 --~3 .
: . . - -. . . ~ , ; : .
. :,, : . . : : . .
These plots show that for any givan condition of strand length and resin solids the strength of tlle engineered lumber increases with increasing compressed density. The rates of increase, i.e. the slope of the strength with density are equal (the lines are parallel). This linear increase of strength with the density is characteristic of ~ood, i.e. if the clear wood strengths of the commercial western softwoods (USDA "Wood Handbook", p. 75-77) are plotted against ovendry density, a straight line is obtained shown by the heavy straight line in Figure 4. This line has the same slope as the engineered lumber lines and acts as an upper limit of those lines.
It will be seen that the 24", 5% line is coincident with the limiting wood strength line. It is believed that no engineerad lumber can be made with graater strength at a given density than this clear wood strength limiting line.
In Figure 4 the MOE requirements of two grades of Douglas fir lumber, select structural and No. 3 structural are shown by horizontal lines (Standard Grading Rules No. 16, WCLIP, p. 135). This shows how engineered lumber can be made with ~-~
equal strength to these grades for all conditions of strand length and resin solids which cross the horizontal strength -lines. For a given grade increased density is required to com~
pensate for shorter strand lengths and reduced resin solids.
Strength Versus % Resin Solids Figure 5 shows that the optimum resin solids percentage is in the range 3-5%. The plots at equal press pressure (and resulting density) level off in this range, any increment in resin solids giving only a marginal increase in strength. This ~i ;
resin solids range is for 1/8" square cross section strands.
Increasing rasin solids would be required for smaller strand section because of increasing specific surface area in the engineered lumber and vice versa with large strand cross sections.
, _ , .
1~;4~9 Ef~ect of Strand Length on Strength Lines taken from Figure 4 are plotted in Figure 6 to show the effect of strand leng-th on strength at equal resin solids (5%). Tha 24" line is almost coincident with the clear wood strength line, the 12" line is about 20% below the clear wood strength line, and the 6" line is about 50% below. The clear western softwoods MOE density line can be assumad equi-valent to engineered lumber with infinitely long strands. Thus the 24" strand lengths are the best approximation to infinite strand lengths. The 24" length on an 1/8" square cross section corresponds to a length to diameter ratio of 200:1 which has been established as the optimum fiber geometry for glass ~iber composites. (Motavkin, A.V., et al "Choice of Optimu~ Structure of Glass Fiber Based Materials", Mekhanika Polimerov 5 (2):
288-297 (1969).
Thickness Swell of Engineered Lumber After Moisture Absorption The compression of the engineered lumber to any desired density has a disadvantage of "springback", the permanent residual thickness swelling which occurs on release of the com-pressive stress with moisture absorption. This "springback" ~`
phenomenon is also experienced in particleboard type products. `~
In angineered lumber the thickness swelling and "springback" is dependent on the overcompression above the unco~pressed density of the strand bundles (extrapolate the lines back to the density X-axis), the resin solids and the strand geometry. This permanent "springback" of about 5% for optimum strand length and resin solids is not disadvantageous in lumber type applications of floor joists and wall studs where the swelling would be re-stricted to the smaller dimension direction as shown in Figure ~.
Effect o~ Species on Thickness Swell and "Springback"
Figure 10 shows the comparison of residual thickness .
, 11)648~9 swell in tha compressed direction ("springback") of aspen with that of Douglas fir for equal strand length and resin solids conditions. It will be seen from the Figure that aspen has a greater "springback" than Douglas fir (about 7% more swell for all densities). This difference can be accounted for if the two 5% 24" lines are extrapolated back to the density X-axis at 20 and 26 lb/cu. ft. for aspen and Douglas fir, respectively. The 6 lb./cu. ft. difference is approximately equal to the differ-ence clear wood dry densities (30.4 23.2 = 7.2) between ~
Douglas fir and aspen. `;
Thus the influence of species on swelling character-istics can be predicted with reference to the Douglas fir data by comparison of clear wood dry densities and drawing lines para- ~
llel to the established Douglas fir standard swell lines. ~ ;
Engineered or dimensional lumber can be made with any desired strength to above that of the structural ~rade of a ;~
high strength wood species, such as Douglas fir, by using wood fibers obtained from low quality logs and combining fiber length, `~
resin content and final product density. The exact combination of fiber length, resin solids and final pressed density chosen will depend upon the econo~ic and technical situation, such as ;~
the fiber length in stock, the co~t of the raw materials, and the wood species available. Examples of such combinations to -~;
meet various grades are shown in the following Table: -'` ` "
.~ '' -.
`; ~
, . , !-;
~.,, .. .... . ... . . .,...... . . . :
. . . .. .
-- ~064~
TABLE
Group Grade MOE Species Fiber Resin Density 1,000,000 Length In. Solids Lbs/Cu/
% Ft.
A Douglas Fir Structural Selsct and No. 1 1.93 24 5 30 24 3 31.2 2~ 1 35.5 -Douglas Fir 12 5 32.6 :
12 3 35.6 12 1 40.0 6 5 36.0 ~i Aspen 24 5 35 W. Red Cedar 24 5 31 Douglas Fir Structural No. 2 1.74 24 5 27.O ~.:
24 1 34.5 12 5 30.5 :~.
Douglas Fir 12 3 32.7 -.
12 1 3~.5 ~-6 5 34.2 Aspen 24 5 31.5 :~:
Douglas Fir W. Red Cedar 24 5 31.5 Structural 12 5 30.5 .: :
No. 3 and Light Framing 24 5 25.0 Construction 1.54 24 3 27 Standard and 24 1 31.5 --UXility Douglas Fir 12 5 28 12 3 30.5 ;:
6 5 34 : :
6 3 34.5 6 1 40 .
Aspen 24 5 28.5 W.Red Cedar 24 5 28 12 5 23.5 ~`
B Pacific Hemlock 1.30 24 5 23 Structural No.3 24 3 25 : .
and Light Framing 24 1 29 Construction. Douglas Fir 12 5 26 -Standard and 12 3 28 ::
Utility. 12 1 33.5 ~:~
In the past th~re has been a great deal o~ waste in the utilization of lignocellulosi~ materials, and particularly wood. During logging operations, the limbs of trees are cut o~f and are burned or left around to decay. In the mills a large percentage of the wood is lost in sawdust, trimmings or cuttings, and the like. Soma effort has been made to reduce the amount of sawdust, and to convert the trimmings and cuttings into chips for use in the manufacture of pulp. However, the waste is still very great. In addition to this, many small trees are left bahind in logging operations since it is uneconomical to cut and handle them, and many species o~ trees and shrubs are not used at all since they are not considered to be suitable for the manufacture of lumber. ~ -Many sources of lignocellulosic ~iber are not commer~
cially utilized for construction purposes because of inherent characteristics that make them economically unattractive, such as small diameter, low density, low resistance to decay, poor grain properties, and poor strength properties. In many areas or countries such weed species can constitute a significant, if not the major, part of the available wood resource. In British Columbia, Canada, Western red cedar constitutes a significant part of the coastal ~orest, something o~ the order of 22%. -However, its strength properties and pulp yield characteristics are such as to make it of little commercial value compared to such contiguous species as Douglas ~ir and hemlock. In some tropical areas, such as Malasia, the desired species may occur at such a low frequency per acre as to allow for only the most ; . . .
primitive segregation and cutting operations. In other areas, the dominaDt vegetation consists of bushes, reeds, and other ~ -$
-~6~8~
woody plants, not suited ~or conventional conversion into con-struction products. In addition to this non utilization o~ non-processed wood ~iber, is the very :Large amount of waste wood generated in the most highly automated, high yield log conver-sion systems. It is estimated that the waste wood amounts to about 45% of the total tree, taking into account all low value uses of residues for fuel and soil conditioning.
The present invention contemplates the production of construction materials, such as lumber, various types of panels, and the production of pulp, from any source of lignaceous cellulosic fiber. The general idea is to break down any ligno-cellulosic material into slivers, fibers or strands by any suit-able means, such as by slicing, crushing, shaving, peeling or the like. The aim in the breakdown is generally to produce as long fibers as possible. During the breakdown there are pro-duced small or fine particles, medium length strands and long length strands. The fine particles are utilized in the manu-facture of pulp and/or fiber boards, the medium lengths are used -~
in the manufacture of strand boards, chip boards and/or particle boards, and the long lengths are manufactured into dimensionedlumber and/or board products. It is this production of $he di-mentioned lumber that makes the process or method practical, since the lumber is engineered to give desired characteristics, regardless of the type of the basic lignocellulosic material.
An important feature of this process is the ~act that it can be operated to produce the various products in accordance with the markat demand. If the demand for pulp is up and fol tha other products is down, more of the material can be converted into short lengths or particles. on the other hand, i~ the demand `~
for strand boards, chip boards or particle boards is up, the percentage of medium lengths can be increased at the expense of the long lengths. Howeuer, if the demand ~or lumber is up, as 3~ - 2 -'i,3 ~648~
many long lengths are produced as possible. As the lumber pro-ducts have the highest com~ercial value, it is usually desirable to aim to produce the highest possible amount of long length fibers.
~he general advantages resulting from this process carry on into the dimensioned lumber field. The lumber can be ~ ~
produced in size and characteristics in accordance with the -market demand. For exampleJ if there is a ralatively great de-mand for two by fours, a large percentage of the long fibers can be converted into these. On the other hand, if other boards or timbers are particularly required, the production can be concen- `
trated on these. - -This is a concept that caD revolutionize the wood ~ ~-product producing industry. Heretofore9 the trees were converted ~ ; ~
: into the best or highest paying products possible. However, with ~ -;
the prior production methods, the control of the type o~ lumber produced-is very limited so-that if a large number of, say, two ~
by fours are in demand, the operation will also result in ths production of large number of boards or lumber of different sizes ~ ;
:- .
which may not be required at the moment. Thus, a producer can end up with a large inventory of boards not needed at the moment when he tries to fulfill the sudden demand for boards or lumber ~ ;~
of other dimensions.
The main product of this process is the dimensioned lumber. It is possible to make any number of boards of the same or dif~erent dimensions, and these can be given desired characteristics regardless of the original source of matsrial.
The term "board" as used herein is intended to include all kinds of boards, timbers and lumber of any desired dimensions.
As stated above, the lignocellulosic materials can be broken down in any desired manner. The fibers are separated by length into those fractions most suitable for the required end 3 _ , ,-: ~, : . , .:.
~0~;~809 use, treated with such additives as may be needed to give the required resistance to decay and ~ire, dried either before or after the addition of adhesives, or they can be left undried, and then combined with a binding material, and, possibly, com-bined with non-cellulosic fibers, such as glass, metals and plastics, and formed into a mass and either cast, molded, extruded or pressed into the desired end product.
Any method of breaking up the raw lignacious cellulos material into fibers will develop a wide range of fiber lengths and diameters. The most profitable and useful end use is a lum-ber product suitable for CODstruCtiOn purposes, followed by a strand panel board with strength properties similar to plywood, ;~
chip boards, and lastly the particle board for essentially non~
structural usas. A possible segregation of the particles in the -~
following lengths for the specified purposes is as follows: -Dimensioned lumbar 6" to 4 feet Strand board 2" to 6"
Chip board ~" to 2"
Particle board Less than ~"
Pul~ Less than ~"
An excess of any ~raction can be broken down into lower lengths.
All of the products than can be produced by the present process, excepting the dimensioned lumber, are produced by known processas.
~ owever, this invention contemplates tha production of dimensioned lumber from any lignacious cellulosic ~aterial.
Use of this concept will significantly affect the conventional forestry practices from the present emphasis upon mer~hantable lumber to that of a maximum yield of woody fiber per acre, and will result in a true tree farming approach utilizing fast grow-ing, short cycle, high vield species rather than the present slow growing long cycle species.
_ 4 . . .
~1~6~
As stated above, one of the advantages of the present process is the utilization on non-commercial "weak" specias in the production of good grade lumber. Some species of wood, such as aspen and alder, are considered low value species and little used for commercial purposes because of their very low yield of merchantable lumber per/unit/acre of logs. This low yield is due to the small size of log, the low strength properties and the incidents of compr~ssion and tension wood causing warp-ing and twisting. Utilization of these species in the manufacture of the various products in accordance with this process makes very large volumes of wood available for commercial use. A ~;
large percentage of the wasts from the standard logging sawmill and manufacturing procadures can be converted to dimensioned lumber having more value than the use of these materials for pulping. Smaller trees and shorter harvesting cycles can be used in order to give an increase in wood yield from given acreag~
The present process lsnds itself to the production of a uniform density material with guaranteed strength and durabil-ity properties, free from the inherent defects of normal lumber-knots, splits and density variations.
The strength properties of wood increase with increas-ing density. All species for which data is at present available ;
show this increaseO This relationship of strength properties to density is of major commercial significance in the use of lumber, - ;~
resulting in allowable design stress values significantly below that of the average strength values of the species involved.
Variations in the density of wood are due to variations in its structure and the presence of extraneous constituents. The structure is characterized by the proportional amoLInts of different cell types, such as fibers, tracheids, vessel ducts, and rays, and by their dimensions. Hereditary tendencies, physiological and mechanical factors, position in the tree trunk, ; - 5 -1064~
all affect the density of the wood. The relationships are very complex and not well understood. The result is a wide variation in density within any ona species which can be as large as a factor of 2 to 2~. The dimensionad lumber of the present inven- -tion overcome these inherent variations in normal lumber proper-ties.
By choice of compressed density, resin solids and strand geometry, particular properties can be imparted to an-gineered or dimensioned lumber. A range o~ lumber-like products can thus be engineered to use specifications, and these are com-petitive on an engineering basis with solid lumber, metals, plastic and concrete.
If desired, fire retardants, preservatives, colorants and the like can be added to the particles or strands used in the production of the dimensioned lumber. `
The engineered or dimensioned lumber produced by this process-is-made-up of callulosic-~ibers-or strands ranging from about 6 inches to about 4 feet in length, and having a width of about 0.05 to 0.25 and a thickness of about 0.05 to about 0.5 inch. These fibers are coated with adhesive in standard coating equipment, such as drum applicators or curtain applicators. A
water insoluble structural glue, such as phenol formaldshyde, is used to coat the fibers, although any suitable type of glue can be used. The coated fibers are arranged in bundles and then subjected in presses to pressures sufficient to produce a fin- ; ~
ished product having predetermiDed dimensions and density. The ~ ;
pressures and temperatures used are sufficient to produce the desired density. For e~ample, pressuras of from about 100 to about 400 psi have been found to be suitable, and the ~ibers ara subjected to a high enough temperature for a time sufficient to produce a temperatura of at least 212F within the product. For example, a temperature of 300F for up to 30 minutes has pro-'` , . . .
106480~
duced desirable products, but this time can be reduced. Ifhigh ~requency energy is used for providing the heat, the press-ing can be done in around one minute.
Referring to the accompanying drawings, Figure 1 diagrammatically illustrates apparatus ~or carrying out the method in accordance with this invention, Figure 2 illustrates one way of producing lignocellu- ;
losic material to useful fiber lengths, Figure 3 illustrates a piece o~ dimensioned lumber made in accordance with this invention, Figure 4 is a graph comparing the modulas of elastici$y -~to density in engineered lumber, Figure 5 is a graph illustrating the relationship o~
the resin solids used relative to the modulas of elasticity, Figure 6 is a graph illustrating the ef~ect of strand or fiber length, Figure 7 dia_rammatically illustrates the direction of springback oi some forms of dimensioned lumber, and .
Ei~gures 8, 9 and 10 ara graphs illustrating specified charactsristics of the dimensioned lumber.
Figure 1 diagrammatically illustrates apparatus for carrying out the present invention. The lignocellulosic material such as logs, roots, branches, waste wood, shrubs and the like, are ~ed to a brsakdown device 10 where they are sliced, crushed or otherwise broken d~wn into fibers. It is desirable to produce long strands or fibers for USQ in the manufacture of dimensioned lumber. For example, these can be f~om 6 inches to 4 feet in length, 0.05 to 0.~5 inch in width, and 0.1 to 0.5 inch in thick- ~ -ness. In the general breakdown there will be fibers o~ medium length and very short fibers. The general aim is to produce as many long fibers as possible since these are used in the produc-tion of dimensioned lumber which is ths most valuable product , ~0648~g for the market. It is at this point that the final output of the process can be controlled. The short or fine fibers are used for pulping or fiber boards, while the medium length fibers are used in the manufacture of strand boards, chipboards, particle boards and the like. If the demand for pulp and/or these differ-ent boards goes up relative to the demand for dimensioned lumber, more short fibers and/or medium fibers are produced at the break-down device 10.
The fibers from device 10 go to a separator 12 which separates out the short length fibers to be used in the manu-facture of fiber boards or pulp, or for any other purpose for which short length fibers are suitable.
Some or all of the medium length and long length fibers may be directed to an applicator 14 where they are treated with fire proofing material, insecticides, preservatives, stains or the like before being sent on to a dryer 16. Some or all of these fibers can be by-passed directly to dryer 16. The moisture content of the fibers is reduced to the desired extent for the ~-~
production of the final product. If desired, the medium length fibers may be separated ~rom the long length fibers before they reach dryer 16, in which case the different groups of fibers would be separately dried in accordance with the demand. ~
In this example, the fibers from dryer 16 go to a ?
separator 18 which separates them into the long fibsrs and the medium fibers. The long fibers go to a glue applicator 20 which may be in any desired form, such as a drum applicator or a curtain applicator, and from here they go to a prass or mold 22 which presses them under heat and pressure into lumber of desired dimensions and the desired density. There is another control at this point, that is, the dimensions of the lumber produ~ed is in accordance with the demand. For example, if there is a great demand for two by fours, the percentage of these would be high . ~.
ILCl 6~
relative to boards of other dimensions ~or which the demand was not so ~reat. Although this diagram merely shows one press or mold 22, it is obvious that there cDuld be several presses so that boards of different dimensions could be made at the same time.
Separator 18 separates out the medium fibers from the long fibers, and these are directed to a glue applicator 24, whence they travel to a press 26 which produces the type of boards required, such as strand boards, chipboards, particle-boards, and the like. Here again, although one press only is shown, there may be several. In addition to this, the "press"
is intended to mean any system necessary to produce the desired particle-type board.
What actually happens in this method or process is that ths original material is broke~ down into fibers of di~fer-ent lengths, and then these are reconstituted into dimensioned lumber, particle-type boards, pulp and the like. With this ~ -arrangement, there is no waste. In addition, the process is geared to handle all of the particles produced from the original material, regardless of their length, and regardless of whe~her the lengths are accidentally or intentionally produced.
Figure 2 illustrates one way of reducing lignocellu-losic material, such as a log, to useful fiber leDgths. A log 30 is cut by suitable slicing material into slices 31, and then each slice 31 is cut into relatively thin pieces 32 which extend the length of slice 31. Each piece 32 has a desired width, such as 0~05 to 0.25 inch. Then each piece is cut transversely into strands 33 of desired thicknesses, for example, 0.05 to 0.5 inch.
These preferably are the length of the pieces 32. It is obvious that during this slicing or cutting process~ there will be a lot of fibers which are considerably shorter than the strands or iibers 33. As stated above, the medium length fibers can be used .
_ g _ ' i~6~8~
in the production of particle-type boards, and the short fibers can be used in the production of pulp, or ~or other desired purposes. ;
Figure 3 illustrates a piece of dimensioned lumber or board 38 made up of strands or fibers 33. These strands or fibers, after being coated with a suitable adhesive, are laid side by side and then pressed under heat and pressure into a board of desired dimensions, such as, for axample, a two by four.
These strands can extend the full length o~ the board, as shown, 1~ or each strand may extsnd only part way through-out the length of the board. The strands are laid side by side, but as these are of random dimensions and lengths, they interlock to a degree so that there are no straight glue lines extending from one sur-face to the other of the board. The density of the finished pro-duct is determined by the amount of pressure and heat used in the press. This is another advantage of this method, that is the boards produced can be not only of desired dimensions, but -they can be made in desired densities in accordance with the ~-purpose for which they are designsd. In addition, it is po~sible to subject the long strands to a continuous pressing operation so ;~
that boards of any desired length can be produced. As the strands are interlaced to a certain degree, any length of board can be produced.
Although the lengths of the strands for dif~erent purposes can vary, the following is an indication of practical leDgths for the different pUrpQSeS~
Engineered lumber 6 inches to 48 inches `~
Strand board 2 inches to 6 inches Chipboard ~ inch to 2 inches ~ -Particle board Less than a ~ inch Pulp chips and sawdust ~0648~
In the manufactured or dimensioned lumber, the re~
sistance of the glueline to horizontal shearing ~orces is pro-portional to tha length of the fiber to which the stress îs being transmitted to the glueline. It i5 also inversely proportional to the thickness of the glueline wh:ich is rel~ted to ths ~iber thickness to the extand that the degree to which a "closest packing" condition of the fibers is achieved. The optimum resin ;~;
content for any set of variables is that at which maximum strength properties are obtained, all else being equal. Theoretically, too little resin gives insufficient coverage, and too much resin causes thick gluelines, thereby reducing strength. Variables affecting the optimum resin content are the fiber geometry and the pressure applied during the curing of the resin.
The thing that makes this process an economical success is the fact that engineered or dimensioned lumber can be made with equal strength to that of top structural grade Douglas fir lumber. This can be either on an equal density basis using ~- ;
optimum fiber geometry ~nd adhesive content, or it can be on an ;
increased density basis using less favourable fiber geometry and adhesive content. The strength of the engineered lumber is essentially independent of the raw material species, but in-creased "springback" with moisture absGrption occurs with the ~`
use of low dansity species. The durability and stability are mainly controlled by adhesive content.
Strength-Density Relationship for Engineered Lumber Figure 4 shows plots of the strengths (Modulus of Elasticity,MOE) against compressed density for engineered lumber made from 1/8" Douglas fir strands under the following con-ditions:
Strand length 6", 12", 24"
Resin solids 1, 3, 5% (Phenol formaldehyde solids to dry wood percentage) Press pressures 100 to 400 psi ~ -- 11 --~3 .
: . . - -. . . ~ , ; : .
. :,, : . . : : . .
These plots show that for any givan condition of strand length and resin solids the strength of tlle engineered lumber increases with increasing compressed density. The rates of increase, i.e. the slope of the strength with density are equal (the lines are parallel). This linear increase of strength with the density is characteristic of ~ood, i.e. if the clear wood strengths of the commercial western softwoods (USDA "Wood Handbook", p. 75-77) are plotted against ovendry density, a straight line is obtained shown by the heavy straight line in Figure 4. This line has the same slope as the engineered lumber lines and acts as an upper limit of those lines.
It will be seen that the 24", 5% line is coincident with the limiting wood strength line. It is believed that no engineerad lumber can be made with graater strength at a given density than this clear wood strength limiting line.
In Figure 4 the MOE requirements of two grades of Douglas fir lumber, select structural and No. 3 structural are shown by horizontal lines (Standard Grading Rules No. 16, WCLIP, p. 135). This shows how engineered lumber can be made with ~-~
equal strength to these grades for all conditions of strand length and resin solids which cross the horizontal strength -lines. For a given grade increased density is required to com~
pensate for shorter strand lengths and reduced resin solids.
Strength Versus % Resin Solids Figure 5 shows that the optimum resin solids percentage is in the range 3-5%. The plots at equal press pressure (and resulting density) level off in this range, any increment in resin solids giving only a marginal increase in strength. This ~i ;
resin solids range is for 1/8" square cross section strands.
Increasing rasin solids would be required for smaller strand section because of increasing specific surface area in the engineered lumber and vice versa with large strand cross sections.
, _ , .
1~;4~9 Ef~ect of Strand Length on Strength Lines taken from Figure 4 are plotted in Figure 6 to show the effect of strand leng-th on strength at equal resin solids (5%). Tha 24" line is almost coincident with the clear wood strength line, the 12" line is about 20% below the clear wood strength line, and the 6" line is about 50% below. The clear western softwoods MOE density line can be assumad equi-valent to engineered lumber with infinitely long strands. Thus the 24" strand lengths are the best approximation to infinite strand lengths. The 24" length on an 1/8" square cross section corresponds to a length to diameter ratio of 200:1 which has been established as the optimum fiber geometry for glass ~iber composites. (Motavkin, A.V., et al "Choice of Optimu~ Structure of Glass Fiber Based Materials", Mekhanika Polimerov 5 (2):
288-297 (1969).
Thickness Swell of Engineered Lumber After Moisture Absorption The compression of the engineered lumber to any desired density has a disadvantage of "springback", the permanent residual thickness swelling which occurs on release of the com-pressive stress with moisture absorption. This "springback" ~`
phenomenon is also experienced in particleboard type products. `~
In angineered lumber the thickness swelling and "springback" is dependent on the overcompression above the unco~pressed density of the strand bundles (extrapolate the lines back to the density X-axis), the resin solids and the strand geometry. This permanent "springback" of about 5% for optimum strand length and resin solids is not disadvantageous in lumber type applications of floor joists and wall studs where the swelling would be re-stricted to the smaller dimension direction as shown in Figure ~.
Effect o~ Species on Thickness Swell and "Springback"
Figure 10 shows the comparison of residual thickness .
, 11)648~9 swell in tha compressed direction ("springback") of aspen with that of Douglas fir for equal strand length and resin solids conditions. It will be seen from the Figure that aspen has a greater "springback" than Douglas fir (about 7% more swell for all densities). This difference can be accounted for if the two 5% 24" lines are extrapolated back to the density X-axis at 20 and 26 lb/cu. ft. for aspen and Douglas fir, respectively. The 6 lb./cu. ft. difference is approximately equal to the differ-ence clear wood dry densities (30.4 23.2 = 7.2) between ~
Douglas fir and aspen. `;
Thus the influence of species on swelling character-istics can be predicted with reference to the Douglas fir data by comparison of clear wood dry densities and drawing lines para- ~
llel to the established Douglas fir standard swell lines. ~ ;
Engineered or dimensional lumber can be made with any desired strength to above that of the structural ~rade of a ;~
high strength wood species, such as Douglas fir, by using wood fibers obtained from low quality logs and combining fiber length, `~
resin content and final product density. The exact combination of fiber length, resin solids and final pressed density chosen will depend upon the econo~ic and technical situation, such as ;~
the fiber length in stock, the co~t of the raw materials, and the wood species available. Examples of such combinations to -~;
meet various grades are shown in the following Table: -'` ` "
.~ '' -.
`; ~
, . , !-;
~.,, .. .... . ... . . .,...... . . . :
. . . .. .
-- ~064~
TABLE
Group Grade MOE Species Fiber Resin Density 1,000,000 Length In. Solids Lbs/Cu/
% Ft.
A Douglas Fir Structural Selsct and No. 1 1.93 24 5 30 24 3 31.2 2~ 1 35.5 -Douglas Fir 12 5 32.6 :
12 3 35.6 12 1 40.0 6 5 36.0 ~i Aspen 24 5 35 W. Red Cedar 24 5 31 Douglas Fir Structural No. 2 1.74 24 5 27.O ~.:
24 1 34.5 12 5 30.5 :~.
Douglas Fir 12 3 32.7 -.
12 1 3~.5 ~-6 5 34.2 Aspen 24 5 31.5 :~:
Douglas Fir W. Red Cedar 24 5 31.5 Structural 12 5 30.5 .: :
No. 3 and Light Framing 24 5 25.0 Construction 1.54 24 3 27 Standard and 24 1 31.5 --UXility Douglas Fir 12 5 28 12 3 30.5 ;:
6 5 34 : :
6 3 34.5 6 1 40 .
Aspen 24 5 28.5 W.Red Cedar 24 5 28 12 5 23.5 ~`
B Pacific Hemlock 1.30 24 5 23 Structural No.3 24 3 25 : .
and Light Framing 24 1 29 Construction. Douglas Fir 12 5 26 -Standard and 12 3 28 ::
Utility. 12 1 33.5 ~:~
3 32.5 Aspen 24 5 25 W.Red Cedar 24 5 23.5 12 5 25~5 -~
, .. . ... . .
:; - ~ . . , ~ . .- . . , ~L~6~8~9 As can be seen, the strength of the engineered lumber can be independent of the raw material species so that weak species, such as Aspen and Western Red Cedar, can be used in the manu-facture of the highest strength lumber grades, even though their natural occurring densities of 23.7 and 20.6 lbs/cu. ft., re-spectively, would normally relegate them to the lowast strength grade of 1.00 MM psi MOE. The actual volume of dry fiber re-quired per MFBM of engineered lumber will depend upon the re~
quired grade, tha density of the wood specias, the required density of the engineered lumber for that species, and the length of the fibers. In practice, it is possible to mix species and fiber lengths in various proportions to make the most effect-lve use of the available raw material.
-~'.~,'..
. . ~
. . . ~ . , .
~' ' ''' ' ' ,: . . . . . .
, .. . ... . .
:; - ~ . . , ~ . .- . . , ~L~6~8~9 As can be seen, the strength of the engineered lumber can be independent of the raw material species so that weak species, such as Aspen and Western Red Cedar, can be used in the manu-facture of the highest strength lumber grades, even though their natural occurring densities of 23.7 and 20.6 lbs/cu. ft., re-spectively, would normally relegate them to the lowast strength grade of 1.00 MM psi MOE. The actual volume of dry fiber re-quired per MFBM of engineered lumber will depend upon the re~
quired grade, tha density of the wood specias, the required density of the engineered lumber for that species, and the length of the fibers. In practice, it is possible to mix species and fiber lengths in various proportions to make the most effect-lve use of the available raw material.
-~'.~,'..
. . ~
. . . ~ . , .
~' ' ''' ' ' ,: . . . . . .
Claims (13)
1. A discrete dimensioned structural lumber product comprising adhesively bonded, substantially straight wood strands having lengths of at least 12 inches, average widths of 0.05 inch to 0.25 inch, and average thickness of 0.05 inch to 0.5 inch, said strands being disposed, side by side lengthwise of the lum-ber product in substantially parallel relationship with adhesive bonding adjacent strands but with substantially no straight glue lines extending from one surface to the other of the product, the total amount of adhesive resin solids in said lumber product being from 1% to 5% by weight, said lumber product having a mod-ulus of elasticity for a given dry wood density within the boundaries in FIG. 4 of the curve for western softwood clear lum-ber as an upper limit of modulus of elasticity for a given dry wood density and as a lower limit of modulus of elasticity for a given dry wood density the curve for 24 inch strand length 1%
adhesive resin solids.
adhesive resin solids.
2. A discrete dimensional structural lumber product according to claim 1 wherein said lumber product has a modulus of elasticity of at least 1.30 x 106 p.s.i. and a dry wood density of not more than 40 lbs. per cubic foot.
3. A discrete dimensioned structural lumber product according to claim 1 wherein said lumber product has a modulus of elasticity within the range of 1.17 to 2.2 x 106 p.s.i.
4. A discrete dimensional structural lumber product consisting of adhesively bonded, substantially straight wood strands having lengths of at least 12 inches, average widths of 0.05 inch to 0.25 inch, and average thickness of 0.05 inch to 0.5 inch, said strands being disposed, side by side lengthwise of the lumber product in substantially parallel relationship with adhesive bonding adjacent strands but with substantially no straight glue lines extending from one surface to the other of the product, the total amount of adhesive resin solids in said lumber product being from 1% to 5% by weight, said lumber product having a modulus of elasticity for a given dry wood density with-in the boundaries in FIG.4 of the curve for western softwood clear lumber as an upper limit of modulus of elasticity for a given dry wood density and as a lower limit of modulus of elas-ticity for a given dry wood density the curve for 24 inch strand length 1% adhesive resin solids.
5. A discrete dimensioned lumber product according to claim 4 wherein the strands are at least 1/8 inch thick and at least 1/8 inch wide.
6. A discrete dimensioned lumber product according to claim 4 wherein the dry wood density of the lumber product is from 23 to 40 pounds per cubic foot.
7. A discrete dimensioned lumber product according to claim 4 wherein the length of the strands is at least 24 inches.
8. A discrete dimensional structural lumber product consisting essentially of adhesively bonded, substantially straight wood strands having lengths of at least 12 inches, average widths of 0.05 inch to 0.25 inch, and average thickness of 0.05 inch to 0.5 inch, said strands being disposed, side by side lengthwise of the lumber product in substantially parallel relationship with adhesive bonding adjacent strands but with substantially no straight glue lines extending from one surface to the other of the product, the total amount of adhesive resin solids in said lumber product being from 1% to 5% by weight, said lumber product having a modulus of elasticity for a given dry wood density with-in the boundaries in FIG. 4 of the curve for western softwood clear lumber as an upper limit of modulus of elasticity for a given dry wood density and as a lower limit of modulus of elasti-city for a given dry wood density the curve for 24 inch strand length 1% adhesive resin solids.
9. A discrete dimensional structural lumber product according to either of claims 4 or 8 wherein said lumber product has a modulus of elasticity of at least 1.30 x 10 p.s.i. and a dry wood density of not more than 40 lbs. per cubic foot.
10. A discrete dimensional structural lumber product according to either of claims 4 or 8 wherein said lumber product has a modulus of elasticity within the range of 1.17 to 2.2 x 10 p . s . i .
11. A discrete dimensional structural lumber product according to either of claims 1 or 8 wherein the strands are at least 1/8 inch thick and at least 1/8 inch wide.
12. A discrete dimensional structural lumber product according to either of claims 1 or 8 wherein the dry wood density of the lumber product is from 23 to 40 pounds per cubic foot.
13. A discrete dimensional structural lumber product according to either of claims 1 or 8 wherein the length of the strands is at least 24 inches.
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| US23770572A | 1972-03-24 | 1972-03-24 |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1064809B true CA1064809B (en) | 1979-10-23 |
Family
ID=22894812
Family Applications (2)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA139,003A Expired CA966409A (en) | 1972-03-24 | 1972-04-06 | Lumber products formed of wood fibers and method of manufacturing these products |
| CA 325288 Expired CA1064809B (en) | 1972-03-24 | 1979-04-09 | Lumber products formed of wood fibers and method of manufacturing these products |
Family Applications Before (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA139,003A Expired CA966409A (en) | 1972-03-24 | 1972-04-06 | Lumber products formed of wood fibers and method of manufacturing these products |
Country Status (2)
| Country | Link |
|---|---|
| JP (1) | JPS5017512B2 (en) |
| CA (2) | CA966409A (en) |
Families Citing this family (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| ZA772210B (en) * | 1976-04-15 | 1978-03-29 | Commw Scient Ind Res Org | Reconsolidated wood product |
| JPS5629337Y2 (en) * | 1976-06-22 | 1981-07-13 | ||
| US4255477A (en) * | 1978-10-24 | 1981-03-10 | Holman John A | Artificial board of lumber |
| CN101676078A (en) | 2008-09-19 | 2010-03-24 | 斯戴尔有限责任上市公司 | Artificial timber product and production method thereof |
-
1972
- 1972-04-06 CA CA139,003A patent/CA966409A/en not_active Expired
-
1973
- 1973-03-24 JP JP3312673A patent/JPS5017512B2/ja not_active Expired
-
1979
- 1979-04-09 CA CA 325288 patent/CA1064809B/en not_active Expired
Also Published As
| Publication number | Publication date |
|---|---|
| JPS5017512B2 (en) | 1975-06-21 |
| JPS4915752A (en) | 1974-02-12 |
| CA966409A (en) | 1975-04-22 |
Similar Documents
| Publication | Publication Date | Title |
|---|---|---|
| US4061819A (en) | Products of converted lignocellulosic materials | |
| USRE30636E (en) | Products of converted lignocellulosic materials | |
| KR100715153B1 (en) | Arundo donax composite panal and method thereof | |
| EP2344309B1 (en) | Manufactured wood product and methods for producing the same | |
| US5334445A (en) | Cellulosic fibrous aggregate and a process for its preparation | |
| EP1181138B1 (en) | Hemp hurd composite panels | |
| US20100119857A1 (en) | Manufactured wood product and methods for producing the same | |
| US5067536A (en) | Method for making structural products from long, thin, narrow, green wood strands | |
| CN1334181A (en) | Middle-density fibre board and its production method | |
| EP0092298B1 (en) | Method for the production of a composite material | |
| CA1064809B (en) | Lumber products formed of wood fibers and method of manufacturing these products | |
| US6895723B2 (en) | Compressed wood waste structural I-beam | |
| US7004215B2 (en) | Compressed wood waste structural beams | |
| US4548851A (en) | Composite material | |
| US20230256648A1 (en) | Method of manufacturing a fire-retardant treated wood composite panel | |
| Youngquist et al. | Aspen wood products utilization: impact of the Lake States composites industry | |
| Ahmad et al. | Properties of single-layer urea formaldehyde particleboard manufactured from commonly utilized malaysian bamboo (Gigantochloa scortechinii) | |
| JP4012419B2 (en) | Wood chip oriented laminate | |
| CA2373339C (en) | Hemp hurd composite panels | |
| Wright | Particleboard, Insulation Board, and Hardboard: Industry Trends, 1956-66 | |
| JP2022512000A (en) | Materials | |
| PL238744B1 (en) | Method for producing large-sized wooden structural elements | |
| MATSUDA et al. | Manufacture of Medium Density Fiberboard from Malaysian Fast Growing Tree Species and Bamboo (Research note) |