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WO2002068165A1 - Piece moulee en copeaux de bois munie de trous aux perimetres densifies et amincis et procede de fabrication - Google Patents

Piece moulee en copeaux de bois munie de trous aux perimetres densifies et amincis et procede de fabrication Download PDF

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Publication number
WO2002068165A1
WO2002068165A1 PCT/US2001/005486 US0105486W WO02068165A1 WO 2002068165 A1 WO2002068165 A1 WO 2002068165A1 US 0105486 W US0105486 W US 0105486W WO 02068165 A1 WO02068165 A1 WO 02068165A1
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WO
WIPO (PCT)
Prior art keywords
inches
wood flakes
mat
hole
mold
Prior art date
Application number
PCT/US2001/005486
Other languages
English (en)
Inventor
Bruce A. Haataja
Original Assignee
Strandwood Molding, Inc.
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 Strandwood Molding, Inc. filed Critical Strandwood Molding, Inc.
Priority to CA002438564A priority Critical patent/CA2438564A1/fr
Priority to PCT/US2001/005486 priority patent/WO2002068165A1/fr
Priority to US10/468,698 priority patent/US6830797B2/en
Publication of WO2002068165A1 publication Critical patent/WO2002068165A1/fr

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Classifications

    • 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
    • B27N5/00—Manufacture of non-flat articles

Definitions

  • the present invention relates to wood flake molding.
  • Wood flake molding also referred to as wood strand molding, is a technique invented by wood scientists at Michigan Technological University during the latter part of the 1970s for molding three-dimensionally configured objects out of binder coated wood flakes having an average length of about 1 A to about 6 inches, preferably about 2 to about 3 inches; an average thickness of about 0.005 to about 0.075 inches, preferably about 0.015 to about 0.030 inches; and an average width of 3 inches or less, most typically 0.25 to 1.0 inches, and never greater than the average length of the flakes. These flakes are sometimes referred to in the art as "wood strands.” This technology is not to be confused with oriented strand board technology (see e.g., U.S. Patent No.
  • the top metal tray is removed, and the bottom metal tray is then slid out from underneath the mat, to leave the loosely felted mat in position on the bottom half of the mold.
  • the top half of the mold is then used to press the mat into the bottom half of the mold at a pressure of approximately 600 psi, and at an elevated temperature, to "set” (polymerize) the MDI binder, and to compress and adhere the compressed wood flakes into a final three- dimensional molded part.
  • the excess perimeter of the loosely felted mat that is, the portion extending beyond the mold cavity perimeter, is pinched off where the part defining the perimeter of the upper mold engages the part defining perimeter of the lower mold cavity. This is sometimes referred to as the pinch trim edge.
  • U.S. Patents 4,440,708 and 4,469,216 disclose this technology.
  • the drawings in U.S. Patent 4,469,216 best illustrate the manner in which the wood flakes are deposited to form a loosely felted mat, though the metal trays are not shown.
  • loosely felted it is meant that the wood flakes are simply lying one on top of the other in overlapping and weaving fashion, without being bound together in any way.
  • the binder coating is quite dry to the touch, such that there is no stickiness or adherence which holds them together in the loosely felted mat.
  • the drawings of U.S. Patent 4,440,708 best illustrate the manner in which a loosely felted mat is compressed by the mold halves into a three- dimensionally configured article (see Figs. 2-7, for example).
  • FIG. 1 is a side elevational cross sectional view of the spaced upper and lower mold halves with a loosely felted mat of wood flakes positioned therebetween.
  • Fig. 2 is the same view of Fig. 1 with the mold closed, whereby the wood flakes are consolidated, compressed, and cured under heat and pressure to form a molded wood flake part, having a hole in a boss.
  • Fig. 3 is a side elevational view of the mold apparatus of Fig. 1 with the mold reopened and the part removed.
  • Fig. 4 is a side elevational view of the part once removed from the mold.
  • Fig. 5 is a side elevational cross sectional view of the spaced upper and lower mold halves, having the hole forming punch adjusted, with a loosely felted mat of wood flakes positioned therebetween.
  • Fig. 6 is the same view of Fig. 5 with the mold closed, whereby the wood flakes are consolidated, compressed, and cured under heat and pressure to form a molded wood flake part having an adjusted hole in a boss.
  • Fig. 7 is a side elevational view of the molded apparatus of Fig. 5 with the mold reopened and the part removed.
  • Fig. 8 is a side elevational cross sectional view of the part once removed from the mold, showing the hole adjustment.
  • the mold 10 is used to form loosely felted mat 11 of wood flakes 12 into a molded wood flake part 14 (Fig. 2).
  • the mold 10 includes a top mold die 16 and a bottom mold die 18.
  • the top mold die 16 includes a surface 20 and a male hole forming punch 17 defining a hole forming projection 39, which projects beyond a shoulder 37. Shoulder 37 is flush with the surface 20 of the top mold die 16.
  • the bottom mold die 18 includes a surface 26 and a punch receiver 19 having a cavity 19a therein for receiving projection 39, cavity 19a is slightly larger than projection 39, to accommodate excess wood flake scrap forced therein.
  • top mold die 16 includes a boss forming projection 34 surrounding the male hole punch 17, and the lower mold die includes a boss forming recess, or well 36, surrounding the punch receiver 19.
  • the molded wood flake part 14 is made by positioning a loosely felted mat 11 of wood flakes 12 on the bottom mold die 18 (Fig. 1).
  • the surface 20 of the top mold die 16 is designed to fit closer to the surface 26 of the bottom mold die 18 around the boss 32 and hole 15 (Fig. 2) when the top mold die 16 and bottom mold die 18 are brought together.
  • the male hole forming punch 17 is designed to fit with the punch receiver 19.
  • such mats are typically layered to eight or nine times the desired thickness of the final part.
  • Mat 11 is of relatively uniform thickness, though it can be made thicker or thinner in portions by adding or removing wood flakes 12.
  • top mold die 16 and the bottom mold die 18 are then compressed (Fig. 2) and heat and pressure are applied to the felted mat 11.
  • the felted mat 11 is thereby compressed and cured into the molded wood flake part 14 having a hole 15 (Fig. 3).
  • the narrower width 13 between the surface 20 of the top mold die 16 and the surface 26 of the bottom mold die 18 further compacts the loosely felted mat 11 of wood flakes 12 in the area around the boss 32 and hole 15 when the top mold die 16 and the bottom mold die 18 are compressed.
  • the strength of molded wood flake parts 14 is highly dependent on material density.
  • the target density for the molded wood flake parts 14 is approximately 42 pounds per cubic foot (pcf). Additional densification will improve strength, but as density increases, there is risk of excessive spring back and blistering, requiring lower moisture levels and longer press times.
  • part 14 has a target density of 42 pcf. If the molded wood flake part 14 were made with a raised boss 32 having a hole 15 with the same thickness as the rest of the part 14, then the density in the raised boss 32 would be approximately 36.8 pcf. By reducing the thickness of the part 14 in the area of the boss 32 and the hole 15 by l/16th of an inch, the density of the affected area 21 would be approximately 40.3 pcf.
  • the wood flake part 14 has a thicker portion 25 away from the hole 15, and a thinner portion 21 near the hole 15 and boss 32 (Fig. 4).
  • the density of the thinner portion 21 may be near to or more than the target density of the entire part 14.
  • the wood flake part 14 may have a cap 23 that is formed as a result of the compression of the mat 11 of wood flakes 12 at or near the hole 15 (Fig. 3). This cap 23 can be removed from the wood flake part 14 (Fig. 4).
  • the male hole forming punch 17a of the top mold die 16 can be positioned in mold die 16 so that instead of shoulder 37 being flush with surface 20, it projects beyond the surface 20 of the top mold die 16 (Fig. 5). This can be accomplished, for example, by placing a spacer 28 in the bottom of the punch receiving well 36 of die 16 (Fig. 7). The extended projection 38 shortens the distance between the male hole forming punch 17 and the punch receiver 19 (Fig. 6). The projecting shoulder 37 further compresses the mat 11 at or near the hole 15 resulting in an increasingly narrow portion 28 in part 14 (Fig. 7). This results in increased densification of the part
  • the density immediately around the hole 15 may be increased to approximately 50.3 pcf or any suitable level.
  • An adjustment may also be made to the position of punch receiver 19 to assist in increasing the density near the hole 15.
  • the wood flakes 12 used in creating the molded wood flake part 14 can be prepared from various species of suitable hardwoods and softwoods used in the manufacture of particleboard.
  • suitable woods include aspen, maple, oak, elm, balsam fir, pine, cedar, spruce, locust, beech, birch and mixtures thereof. Aspen is preferred.
  • Suitable wood flakes 12 can be prepared by various conventional techniques. Pulpwood grade logs, or so-called round wood, are converted into wood flakes 12 in one operation with a conventional roundwood flaker. Logging residue or the total tree is first cut into fingerlings in the order of 2-6 inches long with a conventional device, such as the helical comminuting shear disclosed in U.S. Patent No. 4,053,004, and the fingerlings are flaked in a conventional ring-type flaker. Roundwood wood flakes 12 generally are higher quality and produce stronger parts because the lengths and thickness can be more accurately controlled.
  • roundwood wood flakes 12 tend to be somewhat flatter, which facilitates more efficient blending and the logs can be debarked prior to flaking which reduces the amount of less desirable fines produced during flaking and handling.
  • Acceptable wood flakes 12 can be prepared by ring flaking fingerlings and this technique is more readily adaptable to accept wood in poorer form, thereby permitting more complete utilization of certain types of residue and surplus woods.
  • the wood flakes 12 should have an average length of about 1 l A inch to about 6 inches and an average thickness of about 0.005 to about 0.075 inches.
  • the average length of the wood flakes is preferably about 2 to about 3 inches. In any given batch, some of the wood flakes 12 can be shorter than 1 4 inch, and some can be longer than 6 inches, so long as the overall average length is within the above range. The same is true for the thickness.
  • wood flakes 12 having a thickness greater than about 0.075 inch are relatively stiff and tend to overlie each other at some incline when formed into the felted mat 11. Consequently, excessively high mold pressures are required to compress the wood flakes 12 into the desired intimate contact with each other. For wood flakes 12 having a thickness falling within the above range, thinner ones produce a smoother surface while thick ones require less binder. These two factors are balanced against each other for selecting the best average thickness for any particular application.
  • the average thickness of the wood flakes 12 preferably is about 0.015 to about 0.25 inches, and more preferably about 0.0020 inch.
  • the width of the wood flakes 12 is less important.
  • the wood flakes 12 should be wide enough to ensure that they lie substantially flat when felted during mat formation.
  • the average width generally should be about 3 inches or less and no greater than the average length.
  • the majority of the wood flakes 12 should have a width of about 1/16 inch to about 3 inches, and preferably 0.25 to 1.0 inches.
  • the blade setting on a flaker can primarily control the thickness of the wood flakes 12.
  • the length and width of the wood flakes 12 are also controlled to a large degree by the flaking operation. For example, when the wood flakes 12 are being prepared by ring flaking fingerlings, the length of the fingerlings generally sets the maximum lengths.
  • Other factors, such as the moisture content of the wood and the amount of bark on the wood affect the amount of fines produced during flaking. Dry wood is more brittle and tends to produce more fines. Bark has a tendency to more readily break down into fines during flaking and subsequent handling than wood.
  • the flake size can be controlled to a large degree during the flaking operation as described above, it usually is necessary to use some sort of classification in order to remove undesired particles, both undersized and oversized, and thereby ensure the average length, thickness and width of the wood flakes 12 are within the desired ranges.
  • both screen and air classification usually are required to adequately remove both the undersize and oversize particles, whereas fingerling wood flakes 12 usually can be properly sized with only screen classification.
  • Wood flakes 12 from some green wood can contain up to 90% moisture.
  • the moisture content of the mat must be substantially less for molding as discussed below.
  • wet wood flakes 12 tend to stick together and complicate classification and handling prior to blending.
  • the wood flakes 12 are preferably dried prior to classification in a conventional type drier, such as a tunnel drier, to the moisture content desired for the blending step.
  • the moisture content to which the wood flakes 12 are dried usually is in the order of about 6 weight % or less, preferably about 2 to about 5 weight %, based on the dry weight of the wood flakes 12.
  • the wood flakes 12 can be dried to a moisture content in the order of 10 to 25 weight % prior to classification and then dried to the desired moisture content for blending after classification. This two-step drying may reduce the overall energy requirements for drying wood flakes 12 prepared from green woods in a manner producing substantial quantities of particles which must be removed during classification and, thus, need not be as thoroughly dried.
  • a known amount of the dried, classified wood flakes 12 is introduced into a conventional blender, such as a paddle-type batch blender, wherein predetermined amounts of a resinous particle binder, and optionally a wax and other additives, is applied to the wood flakes 12 as they are tumbled or agitated in the blender.
  • a conventional blender such as a paddle-type batch blender
  • predetermined amounts of a resinous particle binder, and optionally a wax and other additives is applied to the wood flakes 12 as they are tumbled or agitated in the blender.
  • Suitable binders include those used in the manufacture of particle board and similar pressed fibrous products and, thus, are referred to herein as "resinous particle board binders.
  • Suitable binders include thermosetting resins such as phenolformaldehyde, resorcinol-formaldehyde, melamine-formaldehyde, urea- formaldehyde, urea-furfuryl and condensed furfuryl alcohol resins, and organic poly isocy antes, either alone or combined with urea- or melamine-formaldehyde resins.
  • Particularly suitable polyisocyanates are those containing at least two active isocy anate groups per molecule, including diphenylmethane diisocyanates, m- and p- phenylene diisocyanates, chlorophenylene diisocyanates, toluene di- and triisocyanates, triphenylmethene triisocyanates, diphenylether-2,4,4'-triisoccyanate and polyphenylpolyisocyanates, particularly diphenylmethane-4,4'-diisocyanate. So-called MDI is particularly preferred.
  • the amount of binder added to the wood flakes 12 during the blending step depends primarily upon the specific binder used, size, moisture content and type of the wood flakes 12, and the desired characteristics of the part being formed. Generally, the amount of binder added to the wood flakes 12 is about 2 to about 15 weight %, preferably about 4 to about 10 weight % , as solids based on the dry weight of the wood flakes 12. When a poly isocy anate is used alone or in combination with a urea- formaldehyde resin, the amounts can be more toward the lower ends of these ranges.
  • the binder can be admixed with the wood flakes 12 in either dry or liquid form.
  • the binder preferably is applied by spraying droplets of the binder in liquid form onto the wood flakes 12 as they are being tumbled or agitated in the blender.
  • a conventional mold release agent preferably is applied to the die or to the surface of the felted mat prior to pressing.
  • a conventional liquid wax emulsion preferably is also sprayed on the wood flakes 12 during the blinding step.
  • the amount of wax added generally is about 0.5 to about 2 weight %, as solids based on the dry weight of the wood flakes 12.
  • additives such as at least one of the following: a coloring agent, fire retardant, insecticide, fungicide, mixtures thereof and the like may also be added to the wood flakes 12 during the blending step.
  • a coloring agent such as fire retardant, insecticide, fungicide, mixtures thereof and the like
  • the binder, wax and other additives can be added separately in any sequence or in combined form.
  • the moistened mixture of binder, wax and wood flakes 12 or "furnish" from the blending step is formed into a loosely-felted, layered mat 11 , which is placed within the cavity 30 prior to the molding and curing of the felted mat 11 into molded wood flake part 14.
  • the moisture content of the wood flakes 12 should be controlled within certain limits so as to obtain adequate coating by the binder during the blending step and to enhance binder curing and deformation of the wood flakes 12 during molding.
  • the presence of moisture in the wood flakes 12 facilitates their bending to make intimate contact with each other and enhances uniform heat transfer throughout the mat during the molding step, thereby ensuring uniform curing.
  • excessive amounts of water tend to degrade some binders, particularly urea-formaldehyde resins, and generate steam which can cause blisters.
  • the wood flakes 12 are too dry, they tend to absorb excessive amounts of the binder, leaving an insufficient amount on the surface to obtain good bonding and the surfaces tend to cause hardening which inhibits the desired chemical reaction between the binder and cellulose in the wood. This latter condition is particularly true for polyisocyanate binders.
  • the moisture content of the furnish after completion of blending should be about 5 to about 25 weight % , preferably about 8 to about 12 weight %.
  • higher moisture contents within these ranges can be used for polyisocyanate binders because they do not produce condensation products upon reacting with cellulose in the wood.
  • the furnish is formed into the generally flat, loosely-felted, mat 11, preferably as multiple layers.
  • a conventional dispensing system similar to those disclosed in U.S. Pat. Nos. 3,391,223 and 3,824,058, and 4,469,216 can be used to form the felted mat
  • such a dispensing system includes trays, each having one open side, carried on an endless belt or conveyor and one or more (e.g., three) hoppers spaced above and along the belt in the direction of travel for receiving the furnish.
  • a plurality of hoppers usually are used with each having a dispensing or forming head extending across the width of the carriage for successively depositing a separate layer of the furnish as the tray is moved beneath the forming heads. Following this, the tray is taken to the mold to place the felted mat within the cavity of bottom mold, by sliding the tray out from under mat.
  • the felted mat should preferably have a substantially uniform thickness and the wood flakes 12 should lie substantially flat in a horizontal plane parallel to the surface of the carriage and be randomly oriented relative to each other in that plane.
  • the uniformity of the mat thickness can be controlled by depositing two or more layers of the furnish on the carriage and metering the flow of furnish from the forming heads.
  • the thickness of the mat that would optimally have the nominal part thickness preferably controlled by closely metering the flow of furnish from the forming heads.
  • the mat thickness that would optimally have the nominal part thickness used will vary depending upon such factors as the size and shape of the wood flakes 12, the particular technique used for forming the mat 11, the desired thickness and density of the molded wood flake part 14 produced, the configuration of the molded wood flake part 14, and the molding pressure to be used.
  • the felted mat 11 mat is compressed and cured under heat and pressure when the top mold die 16 engages the bottom mold die 18.
  • any flashing or caps 23 are removed by conventional means.
  • the surface 20 of the top mold die 16 and the surface 26 of the bottom mold die 18 fit closer together near the boss 32 and hole 15, formed by the male hole forming punch 17 and punch receiver 19, thus compressing the felted mat 11 more at the peripheries of the hole 15 in boss 32.
  • the resulting wood flake part 14 has a thinner portion 21 in the boss 32 near the hole 15, which serves to strengthen the peripheries of the hole 15.
  • the thinner portion 21 may have near to or more than the target density of the entire part 14.
  • the illustrated example shows the hole 15 being formed in a raised boss 32 (Fig.
  • the raised boss 32 is created by a boss forming projection 34 in the top surface 20 and the corresponding boss forming recess 36 in bottom surface 26. It is envisioned that the hole 15 and/or boss 32 can be created by having the male hole forming punch 17 in either top mold die 16 or bottom mold die 18. Furthermore, in accordance with the present invention, the hole 15 may be made in the part 14, without a raised boss 32.

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

Abstract

La présente invention concerne une pièce moulée en copeaux de bois (14) dans laquelle un périmètre densifié et/ou aminci entoure un trou (15) formé dans la pièce. Le procédé de fabrication de la pièce précitée consiste à rétrécir la cavité de moule entourant le trou et/ou à former sur un perforateur de trous (17) un épaulement qui est projeté au-delà de la surface du moule afin de comprimer davantage les copeaux de bois à proximité du trou.
PCT/US2001/005486 2001-02-21 2001-02-21 Piece moulee en copeaux de bois munie de trous aux perimetres densifies et amincis et procede de fabrication WO2002068165A1 (fr)

Priority Applications (3)

Application Number Priority Date Filing Date Title
CA002438564A CA2438564A1 (fr) 2001-02-21 2001-02-21 Piece moulee en copeaux de bois munie de trous aux perimetres densifies et amincis et procede de fabrication
PCT/US2001/005486 WO2002068165A1 (fr) 2001-02-21 2001-02-21 Piece moulee en copeaux de bois munie de trous aux perimetres densifies et amincis et procede de fabrication
US10/468,698 US6830797B2 (en) 2001-02-21 2001-02-21 Wood strand molded part having holes with densified and thinner perimeters and method of making same

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
PCT/US2001/005486 WO2002068165A1 (fr) 2001-02-21 2001-02-21 Piece moulee en copeaux de bois munie de trous aux perimetres densifies et amincis et procede de fabrication

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WO2002068165A1 true WO2002068165A1 (fr) 2002-09-06

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PCT/US2001/005486 WO2002068165A1 (fr) 2001-02-21 2001-02-21 Piece moulee en copeaux de bois munie de trous aux perimetres densifies et amincis et procede de fabrication

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WO (1) WO2002068165A1 (fr)

Citations (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4248820A (en) * 1978-12-21 1981-02-03 Board Of Control Of Michigan Technological University Method for molding apertures in molded wood products
US4440708A (en) * 1978-12-21 1984-04-03 Board Of Control Of Michigan Technological University Method for molding articles having non-planar portions from matted wood flakes

Patent Citations (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4248820A (en) * 1978-12-21 1981-02-03 Board Of Control Of Michigan Technological University Method for molding apertures in molded wood products
US4440708A (en) * 1978-12-21 1984-04-03 Board Of Control Of Michigan Technological University Method for molding articles having non-planar portions from matted wood flakes

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Publication number Publication date
CA2438564A1 (fr) 2002-09-06

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