WO2002002886A1 - Materiaux structuraux biocomposites, et systemes et procedes associes - Google Patents

Materiaux structuraux biocomposites, et systemes et procedes associes Download PDF

Info

Publication number
WO2002002886A1
WO2002002886A1 PCT/US2001/021052 US0121052W WO0202886A1 WO 2002002886 A1 WO2002002886 A1 WO 2002002886A1 US 0121052 W US0121052 W US 0121052W WO 0202886 A1 WO0202886 A1 WO 0202886A1
Authority
WO
WIPO (PCT)
Prior art keywords
strands
panel
matt
inch
wood cellulosic
Prior art date
Application number
PCT/US2001/021052
Other languages
English (en)
Inventor
Michael J. Riebel
Paul L. Torgusen
Original Assignee
Phenix Biocomposites, Llc
Priority date (The priority date 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 date listed.)
Filing date
Publication date
Application filed by Phenix Biocomposites, Llc filed Critical Phenix Biocomposites, Llc
Priority to AU2001270292A priority Critical patent/AU2001270292A1/en
Publication of WO2002002886A1 publication Critical patent/WO2002002886A1/fr

Links

Classifications

    • E—FIXED CONSTRUCTIONS
    • E04—BUILDING
    • E04C—STRUCTURAL ELEMENTS; BUILDING MATERIALS
    • E04C2/00—Building elements of relatively thin form for the construction of parts of buildings, e.g. sheet materials, slabs, or panels
    • E04C2/02—Building elements of relatively thin form for the construction of parts of buildings, e.g. sheet materials, slabs, or panels characterised by specified materials
    • E04C2/10—Building elements of relatively thin form for the construction of parts of buildings, e.g. sheet materials, slabs, or panels characterised by specified materials of wood, fibres, chips, vegetable stems, or the like; of plastics; of foamed products
    • E04C2/16—Building elements of relatively thin form for the construction of parts of buildings, e.g. sheet materials, slabs, or panels characterised by specified materials of wood, fibres, chips, vegetable stems, or the like; of plastics; of foamed products of fibres, chips, vegetable stems, or the like
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B27—WORKING OR PRESERVING WOOD OR SIMILAR MATERIAL; NAILING OR STAPLING MACHINES IN GENERAL
    • B27N—MANUFACTURE BY DRY PROCESSES OF ARTICLES, WITH OR WITHOUT ORGANIC BINDING AGENTS, MADE FROM PARTICLES OR FIBRES CONSISTING OF WOOD OR OTHER LIGNOCELLULOSIC OR LIKE ORGANIC MATERIAL
    • B27N3/00—Manufacture of substantially flat articles, e.g. boards, from particles or fibres
    • B27N3/04—Manufacture of substantially flat articles, e.g. boards, from particles or fibres from fibres

Definitions

  • the present invention relates to biocomposite materials, systems, and methods, particularly to materials made from agricultural straw. More specifically, the present invention relates to structural biocomposite materials that have applications in residential and commercial construction in addition to countertop, furniture, and other related industrial applications, as well as decorative applications.
  • Structural material is defined as material that meets the mechanical and physical properties defined by the structural performance standards of the PFS Research Foundation entitled the PFS Research Foundation's Performance Standards for Policies for Structural-use Panels (PS-2), or equivalent grade requirements (e.g., CSA standards). These are standards of certification to assure that panel products satisfy the structural requirements of the application for which they are intended. Consequently, these standards are performance- based and not intended to address how panels are to be manufactured.
  • Primary supporting documents of PS-2 are U.S. Department of Commerce Voluntary Product standards based on structural use panels such as structural use plywood, oriented strand board (OSB), and other biocomposite materials. The most widely used structural panels in home construction are plywood and OSB.
  • OSB includes engineered, matt-formed, panel products made of strands, flakes, or wafers sliced from small diameter, round wood logs and bonded with an exterior-type binder under heat and pressure.
  • Strand dimensions are predetermined and have a uniform thickness.
  • the common strand geometries use a combination of strands up to 6 inches (150 mm) in length, 1 inch (25 mm) in width, and 0.025 inch (0.635 mm) to 0.035 inch (0.889 mm) in thickness.
  • OSB panels consist of layered matts with the exterior or surface layers consisting of strands aligned in the long panel direction and inner layers consisting of cross- or randomly-aligned strands. The strength of OSB panels comes mainly from the uninterrupted wood fiber, interweaving of the long strands or wafers, and degree of orientation of strands in the surface layers. Binders are combined with the strands to provide internal strength and rigidity.
  • Plywood is a biocomposite panel derived from multi-layers of wood veneers that are glued together, typically in three or more layers.
  • Plywood is a flat panel built up of sheets of veneer called plies, united under pressure by a bonding agent to create a panel with an adhesive bond between plies; it can be made from either softwoods or hardwoods.
  • Plywood is always constructed with an odd number of layers with the grain direction of adjacent layers perpendicular to one another. Since layers can consist of a single ply or of two or more plies laminated such that their grain is parallel, a panel can contain an odd or even number of plies but always an odd number of layers.
  • the outside plies are called faces or face and back plies; the inner plies are called cores or centers; and the plies with grain perpendicular to that of the face and back are called crossbands.
  • the core may be veneer, lumber, or particleboard, with the total panel thickness typically not less than 1.6 mm (1/16 inch) or more than 76 mm (3 inches).
  • the plies may vary as to number, thickness, species, and grade of wood. To distinguish the number of plies (individual sheets of veneer in a panel) from the number of layers (number of times the grain orientation changes), panels are sometimes described as three-ply, three-layer or four-ply, three-layer.
  • centers generally have their grain direction oriented parallel to the length or long dimension of the panel.
  • the grain of even-numbered layers is perpendicular to the panel's length.
  • agricultural straw e.g., cereal grain straw
  • Cereal grain straw such as wheat, rice, and others have a unique strength to weight ratio and natural fiber geometry which make them desirable for making high strength biocomposite materials or biocomposite panels that meet or exceed structural performance ratings in accordance to US standards for building codes. Due to their unique geometries, chemical makeup, and bulk densities, however, traditional wood theory does not directly apply to the production of a biocomposite structural panel product.
  • U.S. Pat. No. 5,498,469 (Howard et al.) discloses a thin panel of compressed non- woody lignocellulosic material made by mixing short straw pieces with a binder. The panel was used as a core layer or core stock in a plywood laminate; thus, a thin layer of straw panel was sandwiched between two stronger wood sheets of plywood. Although this thin panel appears to perform its intended function, it does not have sufficient strength as a structural board.
  • U.S. Pat. No. 5,656,129 (Good et al.) discloses a method of refining wheat straw into fibers by cutting the straw to a length of two to four inches, wetting the straw, softening the straw by subjecting the straw to pressurized steam, and refining the softened straw in a pressurized mechanical refiner to produce fibers capable of being used in the manufacture of cellulosic board products.
  • the straw fibers can be combined in any proportion to other fibers, such as wood fibers, and used in known dry, wet-dry, and wet board manufacturing processes to produce softboard, medium-density fiberboard, and hardboard products.
  • U.S. Pat. No. 5,932,038 (Bach et al.) discloses a method of fabricating a straw panel, board, or beam using straw split with rollermill technology typically used in grinding grain.
  • the rollermill included two closely spaced shear rollers, each being substantially the same size and having a diameter of 200 mm to 800 mm.
  • the straw was split in two pieces lengthwise with a preferred length comparable to wood OSB (preferably, 50 mm to 100 mm long). This process is not desirable at least because it is difficult and/or expensive to scale up to a commercial level, it creates an irregularly shaped strand that does not allow for good surface contact between strands, and it requires that a panel having a higher density than wood be made to meet structural requirements.
  • the strands produced by this process are not desirable at least because they are not of a regular, flat shape and do not lay well together with high surface area contact between strands. Furthermore, upon pressing into a panel, they tend to form curved strands that do not lay flat. Also, the strands described in U.S. Pat. No. 5,932,038 (Bach et al.) must be oriented such that the longitudinal axes of the straw are aligned.
  • wheat has been used to make particleboard where the wheat is ground into particles, with fine particles on the surface (e.g., 20 mesh (0.037 inch/0.95 mm opening) to 60 mesh (0.01 inch/0.25 mm opening)) and larger particles in the core (e.g., 10 mesh (0.075 inch/1.905 mm opening) to 20 mesh (0.037 inch/0.95 mm opening)).
  • fine particles on the surface e.g., 20 mesh (0.037 inch/0.95 mm opening) to 60 mesh (0.01 inch/0.25 mm opening)
  • larger particles in the core e.g., 10 mesh (0.075 inch/1.905 mm opening) to 20 mesh (0.037 inch/0.95 mm opening).
  • Such particleboards have not been found to meet structural material requirements.
  • the present invention provides a structural biocomposite material, typically in the form of a multi-layer construction, that incorporates small strands of agricultural straw, typically non- ood cellulosic straws, such as cereal grain straw.
  • the strands are preferably straight and flat. Because these strands are flat, there is a high level of surface area contact between adjacent strands. Furthermore, they can form an interwoven or interlocking structure that is believed to contribute to the unexpected mechanical and physical properties.
  • the material typically exhibits mechanical and physical properties that meet or exceed plywood or OSB products produced using wood flakes or wood veneers.
  • the present invention provides biocomposite material in the form of structural panels. These panels can be used in manufacturing a wide variety of products, including a substrate for laminates. Significantly, preferred panels (e.g., boards, beams, or nonflat or shaped objects) of the present invention have a strength that exceeds the strength of the straw panels described in U.S. Pat. No.
  • the biocomposite material of the present invention includes non- wood cellulosic straw, such as cereal grain straw, and a binder.
  • the binder is an isocyanate binder.
  • the strands of the agricultural straw are typically of a sufficient size and geometry that they can be laid in a flat interwoven or interlacing pattern, and oriented if desired.
  • the strands are oriented in a parallel fashion in a face layer of a biocomposite panel, although orientation is not required to obtain structural grade material.
  • Such products, as well as others, can be made due to the unique methods of making the strands of agricultural straw and biocomposite panels described herein.
  • a panel in one embodiment, includes flat non-wood cellulosic strands and a resin, wherein at least about 40 wt-% (preferably, at least about 50 wt-%) of the panel includes flat non- wood cellulosic strands having a length of about 0.25 inch (6.35 mm) to no greater than about 2 inches (50 mm) and a particle size distribution of about 4 mesh (5.46 mm) to about 12 mesh (1.52 mm).
  • the particle size distributions are described in terms of the "mesh" of a screen, which correspond to an average opening size.
  • material that has a particle size distribution of about 4 mesh to about 12 mesh is material that passes through a 4 mesh screen, which corresponds to an average 0.21 inch or 5.46 mm opening, and is retained on a 12 mesh screen, which has a 0.06 inch or a 1.52 mm opening.
  • the structural biocomposite panel can be a homogenous construction, a two-layer construction (i.e., a construction with two general regions of different particle sizes), a three-layer construction (i.e., a construction with three general regions, e.g., two surface regions and a core region of a different particle size material), or more.
  • the flat non-wood cellulosic strands having a length of about 0.25 inch (6.35 mm) to no greater than about 2 inches (50 mm) form surface regions of the panel.
  • the panel includes a core that includes non- wood cellulosic strands having a different particle size than the non-wood cellulosic strands at the surfaces.
  • the non- wood cellulosic strands preferably include strands of cereal grain straw, such as wheat, oat, rice, barley, millet, rye, and combinations thereof.
  • the cereal grain straw is wheat.
  • the resin is preferably an isocyanate resin.
  • the resin can be an acid-catalyzed resin.
  • a structural biocomposite panel of the present invention includes flat non- wood cellulosic strands and a resin, wherein at least about 40 wt-% of the panel includes flat non- wood cellulosic strands having a length of about 0.25 inch (6.35 mm) to no greater than about 2 inches (50 mm) and a particle size distribution of about 4 mesh (5.46 mm) to about 12 mesh (1.52 mm), and further wherein the panel includes surface regions that include the flat non- wood cellulosic strands having a length of about 0.25 inch (6.35 mm) to no greater than about 2 inches (50 mm) and a core including non-wood cellulosic strands having a smaller particle size than the non-wood cellulosic strands at the surfaces.
  • a structural biocomposite panel in another embodiment, includes flat non-wood cellulosic strands and a resin, wherein the panel includes surface regions that include non- wood cellulosic strands and a core including non-wood cellulosic strands having a smaller particle size than the non-wood cellulosic strands at the surfaces.
  • a structural biocomposite panel includes flat non- wood cellulosic strands and a resin, wherein at least about 40 wt-% of the panel includes flat non- wood cellulosic strands having a length of about 0.25 inch (6.35 mm) to no greater than about 2 inches (50 mm), a width of about 0.005 inch (0.127 mm) to about 0.1 inch (2.54 mm), an average ratio of length:width:thickness of about 100:10:1, and aparticle size distribution of about 4 mesh (5.46 mm) to about 12 mesh (1.52 mm).
  • the present invention also provides a sample of flat non- wood cellulosic strands.
  • a sample includes at least about 75 wt-% having a length of about 0.25 inch (6.35 mm) to no greater than about 2 inches (50 mm), a width of about 0.005 inch (0.127 mm) to about 0.1 inch (2.54 mm), an average ratio of length: width:thickness of about 100: 10: 1 , and a particle size distribution of about 4 mesh (5.46 mm) to about 12 mesh (1.52 mm).
  • the present invention provides a method of producing strands of straw that are used in making the biocomposite material.
  • the straw is cut and sized using an impact classification milling (ICM) process that forms a unique geometry and particle size range that allows the strands to be laid in a flat interwoven or interlacing pattern.
  • ICM impact classification milling
  • these strands are produced from cereal grain straw without the use of shear rollers, which give non-straight, non-flat, strands of a wide particle size distribution.
  • the method includes: providing non-wood cellulosic straw; impact milling the non-wood cellulosic straw into strands; and classifying the strands to form a sample of flat non- wood cellulosic strands that include at least about 75 wt-% of the strands having a length of about 0.25 inch (6.35 mm) to no greater than about 2 inches (50 mm).
  • the steps of impact milling and classifying are repeated.
  • providing non- wood cellulosic straw includes providing a bale of non- wood cellulosic straw and reducing the bale, using, for example, rotary slicing optionally in combination with classifying.
  • the step of classifying after impact milling can include, for example, air density classifying, rotary screemng, or a combination thereof.
  • the method preferably includes subsequently drying the strands and optionally classifying the dried strands.
  • a method provides a sample of flat non- wood cellulosic strands wherein at least about 75 wt-% of the strands have a width of about 0.005 inch (0.127 mm) to about 0.1 inch (2.54 mm). In another embodiment, a method provides a sample of flat non- wood cellulosic strands wherein at least about 75 wt-% of the strands have an average ratio of length: width:thickness of about 100:10:1.
  • a method provides a sample of flat non-wood cellulosic strands wherein at least about 75 wt-% of the strands have a particle size distribution of about 4 mesh (5.46 mm) to about 12 mesh (1.52 mm).
  • the present invention also provides methods of preparing a structural biocomposite panel.
  • the method includes: providing non- wood cellulosic strands coated with a resin; forming a matt having larger strands on the surfaces of the matt and smaller strands toward the core; and compressing the matt to form a structural biocomposite panel.
  • the method includes applying soap, wax, or oil to the matt. If desired, the matt is compressed on a screen.
  • the matt is formed using a reversed windformer to place larger strands on the surfaces of the matt and smaller strands toward the core.
  • the windformer includes an orienting device for orienting the strands closer to the surface.
  • the matt is formed using a reversed gradient screen former to place larger strands on the surfaces of the matt and smaller strands toward the core.
  • the reversed gradient screen former includes an orienting device for orienting the strands closer to the surface.
  • a matt (and resultant panel) of the present invention can include at least two layers (i.e., regions), which can differ by the particle size of the strands in the layers.
  • the matt (and resultant panel) can have a substantially uniform distribution of strands.
  • a biocomposite panel of the present invention includes a uniform distribution of particle sizes of strands throughout its thickness.
  • a biocomposite panel includes a gradation of particle sizes of strands throughout its thickness.
  • a biocomposite panel includes face layers (surfaces) of strands of similar particle sizes and geometries and a core (third layer) of strands of a relatively smaller particle size, which may or may not be oriented.
  • the core can also have a different density than that of the face layers (e.g., the face layers can have a higher density than the core layer, thereby providing a density gradient that provides additional mechanical strength).
  • the face layers can have a higher percentage of resin than the core for enhanced moisture resistance and mechanical strength.
  • a method of preparing a structural biocomposite panel includes: providing non-wood cellulosic strands coated with a resin; forming a matt having a substantially uniform distribution of strands; wherein at least about 75 wt-% of the strands have a length of about 0.25 inch (6.35 mm) to no greater than about 2 inches (50 mm), a width of about 0.005 inch (0.127 mm) to about 0.1 inch (2.54 mm), an average ratio of length:width:thickness of about 100:10:1, and a particle size distribution of about 4 mesh (5.46 mm) to about 12 mesh (1.52 mm); and compressing the matt to form a structural biocomposite panel.
  • a method of preparing a structural biocomposite panel includes: providing non-wood cellulosic straw; impact milling the non- wood cellulosic straw into strands; classifying the strands to form a sample of flat non-wood cellulosic strands including at least about 75 wt-% of the strands having a length of about 0.25 inch (6.35 mm) to no greater than about 2 inches (50 mm); coating the strands with a resin; forming a matt that includes the resin-coated strands; and compressing the matt to form a structural biocomposite panel.
  • the matt has larger strands on the surfaces of the matt and smaller strands toward the core, which can be accomplished using, for example, a reversed windformer or a reversed gradient screen former, either of which can optionally include an orienting device for orienting the strands closer to the surface.
  • a reversed windformer or a reversed gradient screen former either of which can optionally include an orienting device for orienting the strands closer to the surface.
  • Figure 1 is a chart of MOE values of various panels including two panels of the present invention ("Structural Wheat 1" and “Structural Wheat 2”) compared to wood OSB and the Canadian standard for wood OSB ("O-2");
  • FIG. 1 is parallel to the panel length;
  • Perp is perpendicular to the panel length.
  • Figure 2 is a chart of MOR values of various panels including two panels of the present invention ("Structural Wheat 1" and “Structural Wheat 2") compared to wood OSB and the Canadian standard for wood OSB ("O-2");
  • FIG. 3 is a representation of the volume of one OSB wood strand compared to about 160 flat strands made according to a method of the present invention.
  • Figure 4 is a representation of the number of OSB wood strands in a surface region of a panel prior to pressing relative to the number of flat strands made according to a method of the present invention.
  • Figure 5 is a schematic of the process for preparing strands and panels according to the present invention.
  • Figure 6 is a schematic of a rotary sheer with optional retention screen for the initial bale reducing.
  • Figure 7 is a schematic of a rotary screen classifier and an air classifier in combination with an impact mill with hammers having sharp knife-like leading edges and a screen.
  • Figure 8 is a cross-section of a straw showing the angles at which the straw tubes are cut using an impact milling process compared to a rollermilling process.
  • Figure 9 is a graph of particle size distributions of strands made according to a process of the present invention compared to material made by a conventional process.
  • Figure 10 is a bar chart of particle size distribution of strands made according to a process of the present invention compared to material made by a conventional process.
  • Figure 11 is a bar chart of MOE values of panels of the present invention made with various resin levels compared to the Canadian standard for randomly formed wood OSB ("R-l OSB").
  • Figure 12 is a bar chart of MOR values of panels of the present invention made with various resin levels compared to the Canadian standard for randomly formed wood OSB ("R- 1 OSB").
  • Figure 13 is a bar chart of water immersion values of panels of the present invention made with various resin levels compared to wood OSB.
  • Figure 14 is a schematic of a reversed gradient screen system for panel formation.
  • Figure 15 is a schematic of a reversed windforming system for panel formation.
  • Figure 16 is a chart of MOE values of various panels including one panel of the present invention (“Structural Wheat 3") compared to conventional oriented split strawboard (OSSB) described in Bach, "Structural Board Manufactured from Split Straw,” Forest Products Research Society, May 19- 20, 1999, and the Canadian standard for wood OSB ("O-2"); "Para” is parallel to the panel length; “Perp” is perpendicular to the panel length.
  • OSSB split strawboard
  • Figure 17 is a chart of MOR values of various panels including one panel of the present invention ("Structural Wheat 3") compared to conventional OSSB described in Bach, "Structural Board Manufactured from Split Straw,” Forest Products Research Society, May 19-20, 1999, and the Canadian standard for wood OSB ("O-2"); "Para” is parallel to the panel length; “Perp” is perpendicular to the panel length.
  • the present invention provides biocomposite materials, systems, and methods.
  • the biocomposite materials are made from agricultural straw in the form of very small, flat, and straight strands.
  • the biocomposite materials of the present invention can be used as structural materials.
  • the structural materials can be used for a variety of applications.
  • the panels of the present invention can be used as prepared (e.g., in an unsanded form) as a replacement for OSB or plywood construction panels in home building or industrial usage.
  • a sanded form of the panels of the present invention has a high degree of surface integrity that allows them to be replacements in sanded plywood applications.
  • they can be laminated, as for example, by a medium density overlay for painting.
  • structural materials meet the mechanical and physical properties defined by the structural performance standards of the PFS Research Foundation entitled the PFS Research Foundation's Performance Standards for Policies for Structural-use Panels (PS-2) or equivalent grade requirements (e.g., CSA standards).
  • PS-2 Structural-use Panels
  • Figures 1 and 2 graphs are shown comparing the modulus of rupture (MOR) and modulus of elasticity (MOE) in both the parallel and perpendicular directions to the panel length (or relative to the longitudinal axis strand) of two different panels of the present invention compared to wood OSB that meets or exceeds the PS-2 standard.
  • MOR modulus of rupture
  • MOE modulus of elasticity
  • the material of the present invention meets or exceeds the MOR and MOE values for both PS-2 and CSA standards (generally, an MOR of at least about 4000 psi (27.6 MPa) and an MOE of at least about 700,000 psi (4827 MPa)).
  • the inventors do not wish to be bound by theory, it is believed that this is because the strands formed from the agricultural straw used to make the panels are formed into flat, generally rectangular pieces with straight sides. Because of this very uniform geometry, the strands can be layered in an interwoven, interlacing manner to form a large number of layers, particularly within the surface regions of a panel.
  • each surface region of a 23/32-inch (18.2-mm) wood OSB panel is approximately five strands thick.
  • These surface regions provide the mechanical strength.
  • the surface regions of a panel of the present invention are each over 15 strands thick, arranged in an interwoven or interlacing fashion. This is shown in Figure 4, which shows the relative number of layers of strands prior to pressing.
  • Figure 4 shows the relative number of layers of strands prior to pressing.
  • This differential results because the strands used to prepare the panels of the present invention are flat, straight, and are long and narrow with a length, width, and thickness ratio of about 100:10:1 as compared to the shape of an OSB wood strand, which varies in thickness, is not uniform in shape, and has a length, width, and thickness ratio averaging 12:3:1.
  • the strands of the present invention are also very different from the strands of U.S. Pat. No. 5,932,038 (Bach et al), which would generally be in the shape of a half circle (a straw split in half) and are of various lengths, and typically not straight nor flat strands.
  • the flat and straight shape of the strands of the present invention allows for high surface contact between strands and an interweaving or interlacing effect.
  • the bulk densities of the strands of the present invention are lower than wood flakes. This allows for a higher compression ratio (e.g., 10:1) of these surface layers that yield higher mechanical performance in the structural biocomposite panel compared to wood strands (e.g., 5:1).
  • the materials of the present invention typically have higher water resistance because of the combination of resin and a naturally more water-resistant agricultural material.
  • there is good bonding between the strands and the resin because there is relatively high contact area between the individual strands, which results in high strength. This is discussed in greater detail below with respect to the resin.
  • Biocomposite panels of the present invention can have a wide range of thicknesses and densities.
  • the thickness of a panel is about 0.25 inch (6.35 mm) to about 1.5 inches (38 mm), although panels in a wide variety of thicknesses can be made if desired.
  • panels can be made according to the invention in a wide variety of densities. For example, densities ranging from about 35 pounds per cubic foot (pcf) (561 kilograms per cubic meter (kg/m 3 )) to about 55 pcf (881 kg/m 3 ) can be achieved, with a preferred range of about 40 pcf (641 kg/m 3 ) to about 50 pcf (801 kg/m 3 ).
  • the surfaces can have higher densities than the cores, which can provide additional strength.
  • the two surface layers equal 60% of the weight of the biocomposite and the balance of the weight (40%) is in the core.
  • Panels of the present invention can be of uniform or non-uniform construction and have uniform or non-uniform properties throughout any one panel for the desired effect.
  • a biocomposite panel can include a uniform distribution of particle sizes of strands, geometries of strands, resin contents, and/or densities throughout its thickness.
  • a biocomposite panel can include a gradation of particle sizes of strands, geometries of strands, resin contents, and/or densities throughout its thickness.
  • the panels are in a multi-layer construction.
  • Multi-layered constructions can include layers formed by differing particle sizes of the strands, differing densities, differing resin contents, etc.
  • a panel can include a core of one or more materials having a finer (i.e., smaller particle size) and/or geometry and at least one face layer, and preferably both face layers, of one or more materials having a higher aspect ratio and size than that of the core material.
  • the material can be oriented or not.
  • the strands of the face layers are oriented, although this is not a requirement for structural grade material.
  • a panel can include a core having a different density than that of the face layers (e.g., the face layers can have a higher density than the core layer, thereby providing a density gradient that provides additional mechanical strength). Also, the surface layers can have a higher percentage of resin than the core for enhanced moisture resistance and mechanical strength.
  • non-wood cellulosic straw which includes cereal grain straws as well as other non-wood cellulosics.
  • cereal grain straw and “cereal straw” refer to the stems from a wide variety of grain crops commonly used for food and feed sources.
  • Some examples of such cereal grain straws include, but are not limited to, wheat (summer, winter, durum, semolina, etc.), oat, rice, barley, millet, rye, the triticum genus of cereal grasses, prairie grasses of the plains states, flax, and cannola.
  • non- wood cellulosic straw also includes other cellulosic materials that are cereal strawlike in structure, such as bamboo, as well as soybean, knaf, hemp, and sugarcane straw.
  • the non-wood cellulosic straws can be formed into the desired geometry and particle size range by a number of methods, including, for example, hammer milling, chopping, knife refining, and grinding.
  • the strands are formed by an impact classification process, which is described in greater detail below. This process of the generation of these small, linear (i.e., straight), flat strands are less expensive to produce than wood OSB strands.
  • the resultant biocomposite panels can be of lower cost than traditional structural wood composite panels.
  • Individual strands used to prepare the materials of the present invention are generally two-dimensional, preferably sliced, classified, strands (i.e., not split or chopped). They are extremely flat and thin. The thickness is generally very uniform, with a variation of typically less that 0.001 inch (0.025 mm), as compared to wood OSB strands that can vary well over 0.02 inch (0.508 mm) across a strand. In addition the edge profile of an individual strand is defined and does not round off as do wood OBS strands.
  • Individual strands used to prepare the materials of the present invention are flat and straight (i.e., linear). Preferably, they are of a length of no greater than about 2 inches (50 mm), and more preferably, no greater than about 1.5 inch (38 mm). Preferably, they are of a length of at least about 0.25 inch (6.35 mm), and more preferably, at least about 0.5 inch (12.7 mm). Preferably, they are of a width of no greater than about 0.1 inch (2.54 mm), and more preferably of a width of at least about 0.05 inch (1.27 mm).
  • the strands are of a size sufficient to pass through no larger than a 4 mesh (5.46 mm opening) screen and be held on no smaller than a 12 mesh (1.52 mm opening) screen.
  • the thickness of the strands is dependent on the type of straw.
  • the ratio of length to width contributes to the structural and physical properties of the material.
  • the average ratio of length to width to thickness is about 100:10:1.
  • the geometry of the straw used in making the materials described in U.S. Pat. No. 5,932,038 (Bach et al.) is a strand that is "split" in half, thus being half of a cylinder (i.e., curved), which is typically what results from rollermilling.
  • these strands are preferably 2 inches (50 mm) to 4 inches (100 mm) in length and are "crimped" by the means of their rollermill process.
  • the preferred lengths of the strands of U.S. Pat. No. 5,932,038 are at least 40 mm for structural MOR and MOE values (as shown in Figure 2 of U.S. Pat. No. 5,932,038).
  • the split straws must be oriented, such that the longitudinal axes of the straws are aligned, to obtain structural grade materials.
  • the particle size range contributes to the structural and physical properties of the material.
  • the range of particle size is about 4 mesh to about 12 mesh, which translates to about a 0.21 inch/5.46 mm opening to about a 0.06 inch/1.52 mm opening, and more preferably, about 4 mesh to about 10 mesh, which translates to about a 5.46 mm opening to about a 1.9 mm opening.
  • particle size refers to material that passes the larger mesh screen and is retained on the smaller mesh screen.
  • "optimal" strands have a length of at least about 0.25 inch (6.35 mm) to no greater than about 2 inches (50 mm) with a preference of about 0.75 inch (19 mm) to about 1.5 inch (38 mm), a width of at least about 0.005 inch (0.127 mm) and no greater than about 0.1 inch (2.54 mm) with a preference of about 0.050 inch (1.27 mm), an average ratio of length:width:thickness is about 100:10:1, and a particle size distribution of about 4 mesh (5.46 mm) to about 12 mesh (1.52 mm).
  • the faces of a biocomposite panel are made of at least about 15 layers of these strands.
  • Core material can have a wider range of strand geometry and particle sizes than the face material. This can result from the addition of fine material left over from the impact classification processing, as described in greater detail below.
  • Face material that is smaller in size or not optimal as defined above can be detrimental to overall mechanical and physical performance of the biocomposite.
  • the face layers typically have at least about 50%, and more preferably, at least about 80%» material within the ranges described above.
  • Suitable strands are produced using a rotary slicing process, or alternative bale-reducing method followed by an impact classification milling (ICM) process, wherein cereal grain straw is sliced and fragmented by impact into a range of strands having a desired mesh size, density, and physical geometry.
  • ICM impact classification milling
  • the ICM process produces a narrower aspect ratio strand at a specific length than do conventional process technologies that grind or split the straw.
  • Such conventional processes cannot control the length, uniformity, or geometry of the strands to the degree that the ICM process can.
  • conventional process technology produces a wide range of strand sizes and geometries that are not sorted or classified within the process.
  • the ICM process produces an optimal strand geometry, being of a narrow aspect ratio and a specific flat planar geometry, as described above.
  • this provides for increased fiber weaving and interlacing of the surface layers of the biocomposite.
  • This effect makes it possible to achieve a structural mechanical performance using much shorter fibers than wood or other non-wood materials.
  • the basic process is shown in Figure 5. Processing of large compacted bales of straw (e.g., wheat or rice) can be done using a bale reduction process, such as a slicing or bale-breaking process.
  • the slicing process involves a rotary cutter or rotary impact drum that both cuts and breaks the strands through impact means.
  • This machine shown in Figure 6, uses a rotating drum 10 with sharp cutter knives 12 attached to the rotating drum 10.
  • the sharpness, length, and speed of the knives reduces the strands to specific lengths whereas the speed of the rotary action controls the breakage of the strands.
  • These knives can have either a triangular or square shape with a sharp tip or sharp edge on the leading edge of the cutter. Slicing of a bale in this manner reduces the straw to a strand geometry and size at or larger than the optimal geometry and size to reduce undesired fines.
  • the strands are cut into lengths of about 2 inches (50 mm) to about 6 inches (150 mm).
  • a screen 14 is mounted on the back-side of the drum to increase retention of the strands in the rotary cutter for better control of size and geometry of the strands, and to perform the first level of classification, although a screen is not required.
  • the screen is mounted within about 0.25 inch (6.35 mm) of the knives on the drum and follows the contour of the drum covering up to about one-half (typically, about one-quarter to about one-half) of the circumference of the drum.
  • the screen size is typically between about a 0.75-inch (19-mm) hole size to about a 4-inch (101.6-mm) hole size with optimal being about a 2-inch (50-mm) hole size.
  • Such rotary cutters are commercially available without these screens from companies such as Vermeer (Pella, I A) and Deweze (Harper, KS).
  • the process subsequently involves impact classification milling, which involves screening or classification and impact milling, as shown Figure 5.
  • the first part of the process uses a rotary screen classifier 20 and/or an air density classifier 30, which classifies the fibers primarily by width or arc angle of a tube, as shown in Figure 7.
  • the strands of suitable size are removed and the material that is longer, wider, and inclusions are transferred to an impact mill 40. Unwanted fines can be removed at this point.
  • a rotary screen classifier 20 there can be one or more screens of different mesh size (e.g., a 4 mesh rotary screen 22 and a 10 mesh rotary screen 24).
  • the material that is retained on screen 22 is transferred to the impact mill 40 along line 26, the material that is retained on screen 24 is of desirable particle size and is transferred to a dryer along line 27, as shown in Figure 5, and the fines and dust are removed at 28.
  • straw input is carried by air from air source 32 along lines 34, 36, and 38.
  • the larger, heavier particles will drop in a shorter distance (e.g., along line 38) whereas the smaller finer particles will travel further (e.g., along line 34) and the material of a desirable particle size will travel, for example, along line 36.
  • An impact mill 40 is similar to a standard hammer mill. This milling process is different from standard hammer milling, however, by reconfiguring the hammers 42 to have a sharp knife-like leading edge with a screen 44 concave in the mill, as shown in Figure 7. Other modifications may also be possible for the same results.
  • the screen size is typically between about a 0.75- inch (19-mm) hole size to about a 2-inch (50-mm) hole size with optimal being about a 1-inch (25.4-mm) hole size.
  • Material can be transferred back and forth between the rotary or air density classifier and the impact mill to reduce the strands to the desired particle size. That is, the strands are separated by mesh size and materials larger than desired are resliced and impact reduced in this looping system. Typically, using this process, the strands are cut into arc angles of 90 degrees or less, as shown in Figure 8. This is compared to how a straw tube is sliced in half using a rollermill, for example.
  • U.S. Pat. No. 5,932,038 (Bach et al.) discloses the use of grinding or hammer milling processes to grind a wide distribution of strands to produce a range of strands from over 4 inches (102 mm) to very fine micron size dust.
  • This material with such a wide range of particle sizes is passed through a rollermill to break the tubes of straw in half creating a long half circle strand that does not lend itself for multi-layered surface biocomposites, as produced in the methods of the present invention.
  • the strands of U.S. Pat. No. 5,932,038 (Bach et al.) are generally not screenable, nor uniform, and are generally not straight.
  • the strands of the present invention are flat and straight, and thus, better able to be oriented and layered, which can provide better performance.
  • the homogeneous structural boards of U.S. Pat. No. 5,932,038 (Bach et al.) have poorer performance (e.g., MOR, MOE) at the same strand length.
  • the grinding or rollermilling processes used in U.S. Pat. No. 5,932,038 do not generally allow for the use of straws other than cereal grain straws (i.e., nontubular straws). For example, soy straw would not readily split using these processes as they require a tubular geometry that can be flattened and split.
  • the methods of the present invention allow for a greater input of materials (all non-wood cellulosic materials).
  • Particle reduction processing using a rotary cutter and impact classifier is preferably optimized to create a particle size distribution wherein the majority of the strands are of the desired geometry and particle size. Any strands larger than desired can be reprocessed. Significantly, the use of these two systems reduces the amount of strands that are finer or smaller than the desired geometry and particle size, thereby reducing the amounts of fines and dust created.
  • these strands can be further classified by a variety of screening methods, particularly for removal of the relatively small amount of fines.
  • Two forms of classification processes are preferred for production and sorting of strands.
  • Rotary screening or air density classification processing works well to optimize distribution and efficiency.
  • the optimum strands are separated and the larger material is reprocessed, thereby contributing to the reduction in the amount of fines and dust.
  • fines are acceptable as a relatively small percentage of the core of the structural biocomposite panels, their inclusion is not recommended as they can diminish optimal biocomposite performance. Dust, however, is undesirable.
  • the process of the present invention is optimized for minimal dust creation.
  • Rotary screening is preferably carried out using a rotary drum screener due to the linear nature of the fiber. Even through flat bed screeners may work, the rotary drum system optimizes the geometry and efficiency of the screen process.
  • Traditional flat bed screeners classify particles that are typically uniform geometries.
  • the strands of the present invention are long and narrow, and thus have a tendency to slide across a screen if not fluidized.
  • a rotary system places the strands in the air to allow the strands to hit the screen in a random flow whereas a bed screener allows strands to flow across parallel to the screen. The tighter the distribution of optimal size, the better the properties of the structural biocomposite panel.
  • the unique geometry of the strands of the present invention lends itself to classification by airflow and density.
  • air classification to separate particles are used in other industries but only with very fine particles, typically less than 5 microns.
  • a wind-forming machine used in the classification process described herein is manufactured by Schenck Company, Frankfurt, Germany, and modified by retrofitting to reverse the direction of the air flow and installing separate slots for each desired particle size. This process is preferred over rotary screeners.
  • this form of classification can also be used for removal of foreign objects such as rocks, dirt, metal, wheat or rice seeds, and other inclusion that would be detrimental to the end biocomposite.
  • an ICM process uses larger internal classification screens in conjunction with secondary classification by rotary or wind (air) density classification to optimize strand geometry and maximize the number of strands produced in the desired size region.
  • Length of the strands is controlled by the primary slicer/ breaker and the hole size of the ICM milling process. Width is controlled by the speed of the ICM process and rotary or air density classification. Geometry is controlled by the balance of the process speeds, and relationship between screens in the rotary slicer and ICM process.
  • the graph shown in Figure 10 shows strand distribution of the present ICM/Classification process compared to conventional methods.
  • the strands are then dried while material outside of the desired particle size range is reprocessed or discarded.
  • the straw typically has an initial moisture content of about 10 wt-% to about 30 wt-%. This is preferably reduced to less than about 10 wt-% and more preferably, to about 6 wt-% or less.
  • the moisture content of the strands upon combination with the resin system is preferably about 2 wt-% to about 10 wt-%, and more preferably about 3 wt-% to about 6 wt-%.
  • additional classification can be optionally carried out using conventional methods, such as screening, as shown in Figure 5.
  • various material fractions can be formed. For example, fines (e.g., material of about 30 mesh (0.024 inch 0.6 mm opening) to about 60 mesh (0.01 inch/0.25 mm opening) and dust (e.g., material of less than 60 mesh (0.01 inch/0.25 mm opening) and finer) can be removed at this stage, prior to blending with a resin system, as shown in Figure 5.
  • the strands within the structural biocomposite panels particularly the strands within the surface layers, as opposed to the resin, provide the greatest contribution to the strength of the panels.
  • the resin bonds the strands together but does not provide a significant contribution to the strength.
  • Resins useful in the resin system include, for example, thermosetting resins.
  • a wide variety of resins can be used, such as an isocyanate, epoxy, phenolic, melamine, or urea-containing binder.
  • the thermosetting resin is an organic isocyanate, and more preferably an aromatic isocyanate.
  • the resin system includes one or more isocyanate resins.
  • isocyanate resins can be used.
  • Suitable isocyanates include, but are not limited to, the aromatic isocyanates 4,4-diphenylmethane diisocyanate (MDI), toluene isocyanate (TDI), xylene diisocyanate (XDI), and methaxylene diisocyanate (MXDI).
  • MDI 4,4-diphenylmethane diisocyanate
  • TDI toluene isocyanate
  • XDI xylene diisocyanate
  • MXDI methaxylene diisocyanate
  • the isocyanate is 4,4-diphenyl methane diisocyanate (polymeric MDI, which is available from ICI polyurethanes under the RUBINATE trademark and from Bayer under the MONDUR trademark).
  • Many other isocyanates are commercially available from BASF and Dow, for example.
  • an "acid-catalyzed resin system” as disclosed in WO 00/25998 can be used in one or more layers of the biocomposite panel.
  • a resin i.e., one or more resins
  • an acid catalyst i.e., one or more acid catalysts
  • suitable resins for this embodiment include, but are not limited to, "phenolic resins,” such as phenol formaldehyde and phenol-melamine formaldehyde, melamine, melamine formaldehyde, melamine-urea formaldehyde, melamine-urea-phenol formaldehyde, urea formaldehyde, or a combination of these resins.
  • phenolic resins include those available as PMF 9707 (ARC Resins Corp., Longueuil, QC, Canada) and CRC 153 (Capital Resin Corp., Columbus, OH).
  • Acids useful in the acid-catalyzed resin system include organic acids and mineral acids. Examples include, but are not limited to, formic acid, fumeric acid, sulfuric acid, as well as aromatic sulfonic acids such as benzenesulfonic acid, phenolsulfonic acid, and toluenesulfonic acid.
  • the acid is formic acid, which can be obtained under the tradename ARC CATALYST 9700 (ARC Resins Corp.).
  • the types and amounts of resin (and acid) employed in the resin system typically depend upon the type of non- wood cellulosic material selected and the final biocomposite panel attributes desired.
  • the types and amounts ofresin (and acid) will effect the cure rate of the resin and bond quality of the panel produced.
  • a desired rate of cure is within a range of about 10 seconds to about 25 seconds per millimeter of final panel thickness.
  • Resins employed in biocomposite panels of the invention are typically present in an amount of about 2 weight percent (wt-%) solids to about 10 wt-% solids, and preferably, about 2 wt-% to about 6 wt-%, based on the total amount of solids in a biocomposite panel.
  • the resin amounts may be adjusted throughout the biocomposite independently for the surface layers and core layers. Higher amount ofresin can be used in the surface as compared to the core to add both mechanical and physical water resistance performance. Varying the resin percentage does not significantly affect the strength of the panels, as evidenced by the MOE and MOR values shown in Figures 11 and 12. Increasing the resin percentage increases the water resistance as evidenced by the data shown in Figure 13. At most resin levels, the water resistance is better for the panels of the present invention compared to wood OSB.
  • MDI is used as the resin, although extenders such as soybean protein resins, vegetable oils or petroleum oils, modified waxes, etc., can be used. Additional additives may be added to the resin or to the strands to impart fire resistance (e.g., fire retardants such as borates), additional mold resistance (e.g., fungicides, biocides), termite resistance (e.g., insecticides), color (e.g., dyes or pigments), etc. Also, mold release agents, such as waxes and oils, can be added that also provide additional water resistance.
  • fire retardants such as borates
  • additional mold resistance e.g., fungicides, biocides
  • termite resistance e.g., insecticides
  • color e.g., dyes or pigments
  • mold release agents such as waxes and oils, can be added that also provide additional water resistance.
  • a biocomposite panel according to the invention can be homogeneous with respect to types of resins, types of agricultural straws, and particle size distribution of the strands.
  • the outer (i.e., face or surface) layer(s) (i.e., region(s)) of the structural biocomposite panels preferably include material of a larger particle size than is used in the inner (i.e., core) layer(s) (i.e., region(s)).
  • Forming of the structural biocomposite panels is preferably accomplished in a matt-forming machine that creates a loose matt of layered materials prior to thermal pressing.
  • Uniform or nonuniform matts can be formed depending on the desired end use. Matts are preferably formed in two layers in which these layers are formed in gradients classified by strand geometry and density. The goal is to place the optimally sized strand closest to the surface and strands shorter than optimal near the core of the matt.
  • Three layer matts may also be formed in which a third mechanical former can be used to lay a separate core layer to speed production rates of forming.
  • a bottom or first layer of strands is formed using a first matt former
  • an optional core or second layer of strands is formed using a second matt former
  • a top or third layer of strands is formed using a third matt former.
  • matt formers can be any of a variety of matt formers, such as a reversed gradient screen forming system, shown in Figure 14, and a reversed wind forming system, shown in Figure 15.
  • Gradient screen forming and orienting uses a unique system to classify and form the strands into a matt with the largest strands on the surface of the composite.
  • Figure 14 shows a reversed gradient screen former 50 that includes a large box 52 which contains three screens, although any number of screens can be used.
  • screen 53 is a 4 mesh (5.46 mm) screen
  • screen 54 is a 6 mesh (3.35 mm) screen
  • screen 55 is a 10 mesh (1.905 mm) screen, of which the largest mesh screen is on the leading edge of the matt formation process.
  • These screens may independently vibrate or move to assist in flowing the strands through the screens.
  • a series of moving paddles 58 also assists in moving the strands forward to the screens and assists in allowing the strands to flow through the screens.
  • a series of orienting disks 59 can be placed under the largest screen section which deposits the longest fibers on the surface.
  • a second reversed gradient screen former which is a mirror image of the reversed gradient screen former 50 shown in Figure 14, can be used to apply a second "layer” on the first "layer” applied by the first gradient screen former, thereby forming a gradient of strand length throughout the biocomposite.
  • the largest strands are on the surface and lighter or small strands are wind classified to the core.
  • two gradient screen formers can be used to create the two "layers," the biocomposite panel exhibits a continuous gradient of strand lengths and does not have a visible or mechanical layering effect.
  • a reversed windformer can be used to make a matt.
  • Windformers are used in the forming of conventional wood particleboard matts for surface layers of three-layer particleboard biocomposites.
  • the windformer system uses finer wood materials and classifies them in the surface layer placing the finest materials on the surface to create a smooth surface for optimal laminating conditions.
  • the panel making process of the present invention uses a conventional windformer modified in at least two areas, as shown in Figure 15, to form a reversed windformer 60.
  • the system is modified by reversing the wind (air) flow 62 to allow the larger strands to settle first along line 64, intermediate strands along line 66, and the finest strands settle along line 68.
  • the strands By decreasing air flow in the reverse direction, the strands can be laid flat to optimize performance of the biocomposite surface layer.
  • the area where the strands are laid allows for placement of a series of disks 69 at a 3/8 inch (9.53 mm) interval to align most of the strands in the parallel direction of the board for increased mechanical strength.
  • a second reversed windformer which is a mirror image of the windformer 60 shown in Figure 15, can be used to apply a second "layer" on the first "layer” applied by the first reversed windformer, thereby forming a gradient of strand length throughout the biocomposite. In this resultant gradient, the largest strands are on the surface and lighter or small strands are wind classified to the core. Even though two wind formers can be used to create the two "layers," the biocomposite panel exhibits a continuous gradient of strand lengths and does not have a visible or mechanical layering effect.
  • a fine mist of wax, oil, soap or other water resistant liquid can be applied to the surfaces of the matt to impart additional surface water resistance and/or mold release. These surface liquids saturate into the surface of the matt and are cured within the thermal pressing process.
  • Typical pressing temperatures range from about 250°F (121 °C) to about 450°F (232°C) with a more preferred range from about 320°F (160°C) to about 400°F (204°C).
  • Typical pressing pressures range from 250 psi (1.7 MPa) to 750 psi (5.2 MPa) depending on the final desired panel density. The preferred pressure is about 500 psi (3.4 MPa).
  • Closing speeds of the thermal press range from about 15 seconds to about 120 seconds depending on the surface density specification.
  • Total cycle times or time under heat and pressure range from about 2 minutes to about 6 minutes depending on thickness and density.
  • a % inch (19 mm) panel typically has a curing rate under these typical pressures and temperatures of about 10 to about 18 seconds per millimeter thickness of the final panel.
  • a fine woven steel screen is used beneath the matt and optionally on top of the matt. This reduces water vapor pressures in the matt allowing for faster degasing times during press release and offers advantages in compression of the matt.
  • Cereal straw typically has different thermal dynamic issues as compared to higher density wood strands, thus these parameters with screens offer advantages in thermal transfer issues related to processing straw.
  • the structural biocomposite panels of the present invention can be used sanded or unsanded.
  • a sanded biocomposite panel of the present invention can have applied thereto a laminated medium or high density overlay by means of a secondary thermal fused pressing process. These overlays can be used to produce a structural paintable grade of panels for usage in the transportation industry.
  • Other laminates include metal, melamine foil or a high pressure laminate (e.g., FORMICA).
  • straw bales typically large square bales, weighing approximately 1300 pounds (590 kg) are run through a primary slicer or bale breaking system, which opens the bales, slices the individual straws into strands, although tubular pieces can be formed, and reduces the size of the strands/tubular pieces. Typically, they are reduced to a length of about 1 inch (25.4 mm) to about 5 inches (127 mm), although there may be a percentage of finer materials.
  • the preferred method of slicing uses a drum of 20-inch (500 mm) diameter with multiple cutting knives placed in a helical pattern around the drum and a retention screen covering at least the back l A of the drum.
  • This drum spins at a speed ranging between about 200 revolutions per minute (rpm) and about 1500 rpm and uses between about 20 horsepower to about 100 horsepower to process about 5 tons (4500 kg) to about 10 tons per hour. This is significantly lower than the high horsepower requirement needed to generate wood OSB strand, which is done with a wood strand flaker equipment with horsepowers typically over 500 horsepower to create equal product flow.
  • the material is classified using a rotary or air density classification system.
  • This process classifies the strands primarily by width or arc angle of a tube. Strands of the desired size and geometry are separated and removed to bins whereas material that is longer, wider, and inclusions will go to the next step of the process. Unwanted fines can be removed at this point.
  • the material is further reduced in particle size using an impact mill.
  • This mill includes a combination of knives or sharp hammers in conjunction with a classification screen. This process controls two variables. The speed of rotation of the knives or hammers controls the impact and the breakage of the tubes into specific widths or arc angles.
  • the classification screen controls both retention and length of the strands. This is connected with the classification system used in the second system. That is, the output of the impact mill flows directly back to the classification system for further classification, preferably to reduce the amount of fines generated and tighten the particle size distribution range.
  • the strands are then dried using high volumes of air and low degree of heat due to the thermal dynamic diffusion properties of these strands. This is clearly a significant cost advantage over wood OSB that requires extreme temperatures and high energy costs. Wood drying under these conditions emits large quantities of VOCs, and particulate emissions whereas non- wood cellulosic materials do not emit VOCs and relatively small amounts of particulate material. Drying is done in simple rotary dryer manufactured by companies such as MEC Corp., Minneapolis, KS. The dried material is then further classified if desired. This process separates the optimal strands for placement in a surface storage bin and the finer or less optimal strands are removed and placed in a core storage bin to be used for the core of the biocomposite if desired. This classification step, however, is not required with reversed windforming or gradient screen forming.
  • an MDI-containing resin is used in an amount of about 2 wt- % to about 10 wt-% solids, based on the total weight of the structural biocomposite panel.
  • about 2 wt-% to about 3 wt-% resin content has proven to meet PS-2 Structural Performance Requirements.
  • a matt is then formed of the resin-strand mixture as a single layer, two layers, or three layers, for example. Typically, all of these matts have the optimal strands on the surface.
  • a single layer matt can be formed using a simple mechanical forming head with optional orienting discs.
  • a two-layer matt can be formed using a reversed windforming system or a reversed gradient screen forming head that places the optimal strands on both surfaces of the biocomposites.
  • These matts are sprayed with a mold release, which is a water based wax, soap or oil applied directly to the surface of the matt or to a screen caul system by means of individual spray head similar to an automotive paint spraying system. Amounts of mold release or water resistant additives are applied sufficient to create unique water resistant or water proof surfaces on the structural biocomposite panel.
  • the matts are then compressed to form biocomposite panels.
  • This process uses a high-pressure press with thermally heated platens. By controlling the closure speed and time, heat transfer and temperature, and degas cycle the mechanical and physical properties can be controlled within a specified range.
  • the purpose of this example is to compare the mechanical properties (specifically bending - MOE and MOR) of a 'Structural Wheat Straw Board' (SWSB) of the present invention, wherein coarse longer wheat strands are used on the surface of the panel to improve strength and stiffness, with that of a wood strand Oriented Strand Board (OSB). A further comparison was made with a performance standard used for typical wood strand Oriented Strand Board (OSB).
  • SWSB 'Structural Wheat Straw Board'
  • Structural Wheat 1 utilized core strands that had been further screened on the Sweco circular screener (Sweco Corp., Florence, KY) to further remove strands below a 30 mesh screen with a 0.0269-inch (0.683-mm) opening.
  • the resin used was an isocyanate resin available under the trade designation M20S PMDI from BASF. All wheat strands had water and resin applied to them in a ribbon paddle mixer. Water and resin was sprayed into the closed mixer with conventional air atomizing spray heads. Water was added to achieve approximately 9.0 wt-% moisture content on the surface layers and 7.0 wt-% in the core layer. Resin levels were targeted at 7.0 wt-% for the surface layers and 4.0 wt-% for the core layers. No other additives were used. Matt Forming. Matts were formed by hand leveling predetermined amounts of blended strands in a 24-inch x 24-inch (610-mm x 610-mm) square frame.
  • Alignment of the surface strands was achieved by inserting a removable jig into the square frame onto which strips of metal had been welded parallel to each other with an approximate 0.25-inch to 0.375-inch (6.35-mm to 9.53-mm) gap between strips. Core layer strands were spread randomly without the use of the alignment jig. A 30/40/30 (weight percent) surface/core/surface ratio was used. Predetermined amounts were based on a dry solids weight basis from moisture content tests run after blending.
  • Compression time 300 seconds (includes closing time)
  • Degas time 45 seconds
  • MOE/MOR Testing was performed as per ASTM D 1037 - 96. Any deviations are noted. It is noted that these test methods may or may not be included, or may differ, from the set of tests typically performed on OSB or similar structural products as specified from country to country, however, they do provide for practical comparative results during product development.
  • Wheat straw bales were reduced using a rotary drum grinding system.
  • an Arasmith rotary grinding system described in Example 1 was used. This material was then dried to an average moisture content of about 5 percent on a dry weight basis.
  • the material was processed in the first section of the ICM process in classification screens with three screen decks of 4 mesh, 10 mesh, and 60 mesh.
  • This system was available from Rotex Screening Company (Cincinnati, OH). This system had a bed size of 5 feet by 12 feet (1.5 meters x 3.7 meters) and was set at the maximum angle determined by Rotex.
  • the material of 4-10 mesh (5.46 mm-1.905 mm) was filtered off of the system whereas the material greater in size than 4 mesh (5.46 mm) was sent through a secondary impact milling process. Material finer than 10 mesh (1.905 mm) was separated out for usage in the core of the biocomposite.
  • the material processed through the impact mill was sent back through the classification system and blended with the primary flow. Samples from the 4-10 mesh (5.46-mm- 1.905 mm) flow of strands were taken over a 1-hour period.
  • the impact milling process used a Sprout Bauer impact mill (Sprout
  • Example 3 Preparation of Wheat Panels Varying Resin Level ( Figures 11-13)
  • the purpose of this example is to compare the mechanical (specifically bending - MOE and MOR) and moisture resistance (specifically 24-hour Immersion) properties of a 'Structural Wheat Straw Board' (SWSB) of the present invention, wherein coarse longer wheat strands are used on the surface of the panel to improve strength and stiffness, when resin levels have been varied.
  • a further comparison was made with a performance standard used for typical wood Oriented Strand Board (OSB).
  • a further comparison of moisture resistance (24-hour Immersion) was made with a typical wood strand Oriented Strand Board (OSB).
  • Four (4) sets of laboratory test panels were produced with 'Random' (non-aligned to an axis) face and core layers with varying levels of resin.
  • Wheat strands were prepared and screened as described in Example 1 except no strands between 30 mesh (0.6 mm opening) and 60 mesh (0.25 mm) were removed.
  • the resin used was an isocyanate resin available under the trade designation M20S PMDI from BASF. All wheat strands had water and resin applied to them in a ribbon paddle mixer. Water and resin was sprayed into the closed mixer with conventional air atomizing spray heads. Water was added to achieve approximately 9.0 wt-% moisture content on the surface layers and 7.0 wt-% in the core layer. Resin levels were varied between the sets of panels. No other additives were used. Resin Levels
  • Matts were formed by hand leveling predetermined amounts of blended strands in a 24-inch x 24-inch (610-mm x 610-mm) square frame. Each layer of strands was spread randomly. A 30/40/30 (weight percent) surface/core/surface ratio was used. Predetermined amounts were based on a dry solids weight basis from moisture content tests run after blending.
  • Closing Time 30 seconds
  • Compression time 180 seconds (includes closing time)
  • MOE/MOR and 24-hour Immersion Testing was performed as per ASTM D 1037 - 96. Any deviations are noted. It is noted that these test methods may or may not be included, or may differ, from the set of tests typically performed on OSB or similar structural products as specified from country to country, however, they do provide for practical comparative results during product development.
  • Wood PS2-92 Typical Wood OSB Test Results Results in graphical format are shown in Figures 11-13. These figures demonstrate that varying the resin percentage does not significantly affect the strength of the panels, as evidenced by the MOE and MOR. Also, increasing the resin percentage increases the water resistance. Furthermore, at most resin levels, the water resistance is better for the panels of the present invention compared to wood OSB.
  • the purpose of this example is to compare the mechanical properties (specifically bending - MOE and MOR) of a 'Structural Wheat Straw Board' (SWSB) of the present invention, wherein coarse longer wheat strands are used on the surface of the panel to improve strength and stiffness, with that of a wheat Oriented Split Strawboard (OSSB).
  • SWSB 'Structural Wheat Straw Board'
  • OSSB wheat Oriented Split Strawboard
  • OSB wood Oriented Strand Board
  • the resin used was an isocyanate resin available under the trade designation M20S PMDI from BASF. All wheat strands had water and resin applied in a ribbon paddle mixer. Water and resin was sprayed into the closed mixer with conventional air atomizing spray heads. Water was added to achieve approximately 10.0 wt-% moisture content on the surface layers and 6.0 wt-% in the core layer. Resin levels were targeted at 7.0 wt-% for the surface layers and 4.0 wt-% for the core layers. No other additives were used.
  • Compression time 180 seconds (includes closing time)
  • MOE/MOR Testing was performed as per ASTM D 1037 - 96. Any deviations are noted. It is noted that these test methods may or may not be included, or may differ, from the set of tests typically performed on OSB or similar structural products as specified from country to country, however, they do provide for practical comparative results during product development.

Landscapes

  • Engineering & Computer Science (AREA)
  • Life Sciences & Earth Sciences (AREA)
  • Wood Science & Technology (AREA)
  • Architecture (AREA)
  • Civil Engineering (AREA)
  • Structural Engineering (AREA)
  • Manufacturing & Machinery (AREA)
  • Forests & Forestry (AREA)
  • Dry Formation Of Fiberboard And The Like (AREA)

Abstract

L'invention concerne un matériau structural biocomposite constitué de petits brins de paille du type agricole, notamment de paille cellulosique non ligneuse telle que la paille de céréales.
PCT/US2001/021052 2000-07-05 2001-06-30 Materiaux structuraux biocomposites, et systemes et procedes associes WO2002002886A1 (fr)

Priority Applications (1)

Application Number Priority Date Filing Date Title
AU2001270292A AU2001270292A1 (en) 2000-07-05 2001-06-30 Structural biocomposite materials, systems, and methods

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
US21594600P 2000-07-05 2000-07-05
US60/215,946 2000-07-05

Publications (1)

Publication Number Publication Date
WO2002002886A1 true WO2002002886A1 (fr) 2002-01-10

Family

ID=22805043

Family Applications (1)

Application Number Title Priority Date Filing Date
PCT/US2001/021052 WO2002002886A1 (fr) 2000-07-05 2001-06-30 Materiaux structuraux biocomposites, et systemes et procedes associes

Country Status (3)

Country Link
US (1) US20020100565A1 (fr)
AU (1) AU2001270292A1 (fr)
WO (1) WO2002002886A1 (fr)

Cited By (7)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
GB2446935A (en) * 2007-02-17 2008-08-27 Ecoboard Ltd Method of manufacturing a structural panel, and structural panel made thereby
DE102013226510A1 (de) 2013-12-18 2015-06-18 Panel Board Holding Bv Vorrichtung und Verfahren zur Herstellung einer Platte
WO2016055215A1 (fr) * 2014-10-09 2016-04-14 Mayfair Vermögensverwaltungs Se Plaque, planche ou panneau
WO2016162244A2 (fr) 2015-04-10 2016-10-13 Mayfair Vermögensverwaltungs Se Tête d'épandage, procédé et panneau
DE102015206469B3 (de) * 2015-04-10 2016-10-13 Mayfair Vermögensverwaltungs Se Streukopf, Verfahren und Paneel
DE102015209759A1 (de) 2015-05-28 2016-12-01 Mayfair Vermögensverwaltungs Se Streukopf, Verfahren und Paneel
WO2017081672A1 (fr) * 2015-11-13 2017-05-18 Basf Se Mat composite ignifuge

Families Citing this family (15)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US6886306B2 (en) * 2001-05-04 2005-05-03 Greencor Composites, Llc Fire-resistant material and method of manufacture
US20050223671A1 (en) * 2004-03-24 2005-10-13 Oryzatech, Inc. Culm block and method for forming the same
CA2491638A1 (fr) * 2005-01-06 2006-07-06 Gerard Lavoie Panneau a copeaux orientes
JP4129270B2 (ja) * 2005-05-10 2008-08-06 オリンパス株式会社 シミュレーション方法、シミュレーション装置、およびシミュレーションプログラム
US20070049661A1 (en) * 2005-08-26 2007-03-01 Premomcne, Llc Agricultural stalk strandboard
US20080032147A1 (en) * 2005-08-26 2008-02-07 Thomas Neel Medium density fibreboard
US7625631B2 (en) * 2005-08-31 2009-12-01 Huber Engineered Woods Llc Wood panel containing inner culm flakes
US20070116940A1 (en) * 2005-11-22 2007-05-24 Ou Nian-Hua Panel containing bamboo
US8449986B2 (en) * 2008-03-05 2013-05-28 Scout Materials Llc Multifunctional biocomposite additive compositions and methods
US8389107B2 (en) 2008-03-24 2013-03-05 Biovation, Llc Cellulosic biolaminate composite assembly and related methods
US20110123809A1 (en) * 2008-03-24 2011-05-26 Biovation, Llc Biolaminate composite assembly and related methods
AU2009229406A1 (en) * 2008-03-24 2009-10-01 Biovation, Llc Biolaminate composite assembly and related methods
US20150107749A1 (en) * 2013-10-18 2015-04-23 Unilin, Bvba Process and Device for Gluing Dried Fibers Designated for the Production of Fiberboards
UY38825A (es) * 2019-08-08 2021-02-26 Feltwood Ecomateriales S L Método para la producción de artículos sólidos moldeados fabricados de materiales vegetales no de madera
US20220371219A1 (en) * 2021-05-20 2022-11-24 Washington State University Thermally modified composite wood-strand products for construction and other applications

Citations (6)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4480061A (en) * 1982-12-28 1984-10-30 E. I. Du Pont De Nemours And Company Wood-like articles made from cellulosic filler loaded ethylene interpolymers
DE4412248A1 (de) * 1993-08-31 1995-03-02 Prohadi Produktions Handels Un Strohmehl
WO1995015252A1 (fr) * 1993-12-02 1995-06-08 Bio-Sunn Corporation Traitement de residus agricoles lignocellulosiques
US5498469A (en) 1994-12-02 1996-03-12 Howard; Robert E. Thin panels of non-woody lignocellulosic material
US5729936A (en) 1995-10-03 1998-03-24 Maxwell; James F. Prefab fiber building construction
US5730830A (en) 1995-12-26 1998-03-24 Haddonfield Management Co. Ltd. Fiber panel manufacturing method and apparatus

Patent Citations (6)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4480061A (en) * 1982-12-28 1984-10-30 E. I. Du Pont De Nemours And Company Wood-like articles made from cellulosic filler loaded ethylene interpolymers
DE4412248A1 (de) * 1993-08-31 1995-03-02 Prohadi Produktions Handels Un Strohmehl
WO1995015252A1 (fr) * 1993-12-02 1995-06-08 Bio-Sunn Corporation Traitement de residus agricoles lignocellulosiques
US5498469A (en) 1994-12-02 1996-03-12 Howard; Robert E. Thin panels of non-woody lignocellulosic material
US5729936A (en) 1995-10-03 1998-03-24 Maxwell; James F. Prefab fiber building construction
US5730830A (en) 1995-12-26 1998-03-24 Haddonfield Management Co. Ltd. Fiber panel manufacturing method and apparatus

Cited By (12)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
GB2446935A (en) * 2007-02-17 2008-08-27 Ecoboard Ltd Method of manufacturing a structural panel, and structural panel made thereby
DE102013226510A1 (de) 2013-12-18 2015-06-18 Panel Board Holding Bv Vorrichtung und Verfahren zur Herstellung einer Platte
CN104723437A (zh) * 2013-12-18 2015-06-24 麦秸板控股公司 生产板的设备和方法
WO2015091596A2 (fr) 2013-12-18 2015-06-25 Mayfair Vermögensverwaltungs Se Appareil et procédé de fabrication d'un panneau
DE102013226510B4 (de) * 2013-12-18 2016-10-27 Mayfair Vermögensverwaltungs Se Vorrichtung und Verfahren zur Herstellung einer Platte
WO2016055215A1 (fr) * 2014-10-09 2016-04-14 Mayfair Vermögensverwaltungs Se Plaque, planche ou panneau
DE102014220459A1 (de) 2014-10-09 2016-04-14 Mayfair Vermögensverwaltungs Se Platte, Brett oder Paneel
US10227778B2 (en) 2014-10-09 2019-03-12 Mayfair Vermögensverwaltungs Se Sheet, board or panel
WO2016162244A2 (fr) 2015-04-10 2016-10-13 Mayfair Vermögensverwaltungs Se Tête d'épandage, procédé et panneau
DE102015206469B3 (de) * 2015-04-10 2016-10-13 Mayfair Vermögensverwaltungs Se Streukopf, Verfahren und Paneel
DE102015209759A1 (de) 2015-05-28 2016-12-01 Mayfair Vermögensverwaltungs Se Streukopf, Verfahren und Paneel
WO2017081672A1 (fr) * 2015-11-13 2017-05-18 Basf Se Mat composite ignifuge

Also Published As

Publication number Publication date
US20020100565A1 (en) 2002-08-01
AU2001270292A1 (en) 2002-01-14

Similar Documents

Publication Publication Date Title
US20020100565A1 (en) Structural biocomposite materials, systems, and methods
EP1115942B1 (fr) Panneau composite à base d'arundo donax et procédé de production du même
EP3648937B1 (fr) Panneau à copeaux orientés, procédé de production d'un panneau à copeaux orientés, et appareil de production d'un panneau à copeaux orientés
EP2574455B2 (fr) Panneau en bois multicouche léger
Irle et al. 10 Wood Composites
US20080152861A1 (en) Engineered Wood Composites Having Superior Strength and Stiffness
EP3784456B1 (fr) Panneau de fibres et procédé de formation d'un panneau de fibres
CN101148056A (zh) 无甲醛复合秸秆板生产工艺方法和用途
US20240208109A1 (en) Roof cover board with improved fragment size and plastic-to-paper ratio
EP2794211B1 (fr) Matériaux lignocellulosiques renfermant des fibres lignocellulosiques dans les couches externes et des particules de matière plastique expansée présentes dans l'âme, et méthode et utilisation
Walker et al. Wood-based panels: particleboard, fibreboards and oriented strand board
EP2349663B1 (fr) Panneaux de particules monocouches gaufres et procedes de preparation associes
Cai Selected properties of MDF and flakeboard overlaid with fiberglass mats
EP2507020B1 (fr) Panneau dérivé du bois, léger
RU2781987C2 (ru) Древесноволокнистая плита и способ формирования древесноволокнистой плиты
JP7536976B1 (ja) パーティクルボード及びパーティクルボードの製造方法
RU2776715C1 (ru) Древесная плита с ориентированной стружкой, способ производства и устройство для производства такой плиты
WO2008036106A2 (fr) Procédé integré pour la fabrication simultanée de produits de bois d'oeuvre et de planches à copeaux orientés
Irle The main process stations in a Particleboard production line (Metso Panelboard).
Berglund et al. Wood Composites 10
RU2020138297A (ru) Древесноволокнистая плита и способ формирования древесноволокнистой плиты
JP2004122686A (ja) 木質系複合材料の製造方法
Strandboard Wood-based Composites and Panel Products
Ntalos et al. 3.1 Wood-Based Panels

Legal Events

Date Code Title Description
AK Designated states

Kind code of ref document: A1

Designated state(s): AE AG AL AM AT AU AZ BA BB BG BR BY BZ CA CH CN CO CR CU CZ DE DK DM DZ EC EE ES FI GB GD GE GH GM HR HU ID IL IN IS JP KE KG KP KR KZ LC LK LR LS LT LU LV MA MD MG MK MN MW MX MZ NO NZ PL PT RO RU SD SE SG SI SK SL TJ TM TR TT TZ UA UG US UZ VN YU ZA ZW

AL Designated countries for regional patents

Kind code of ref document: A1

Designated state(s): GH GM KE LS MW MZ SD SL SZ TZ UG ZW AM AZ BY KG KZ MD RU TJ TM AT BE CH CY DE DK ES FI FR GB GR IE IT LU MC NL PT SE TR BF BJ CF CG CI CM GA GN GW ML MR NE SN TD TG

121 Ep: the epo has been informed by wipo that ep was designated in this application
DFPE Request for preliminary examination filed prior to expiration of 19th month from priority date (pct application filed before 20040101)
REG Reference to national code

Ref country code: DE

Ref legal event code: 8642

122 Ep: pct application non-entry in european phase
NENP Non-entry into the national phase

Ref country code: JP