WO2001083176A1 - Dispositif et procede permettant un angle de depouille plus grand au niveau des bords detoures par pincement dans des produits moules a base de copeaux de bois longs - Google Patents

Dispositif et procede permettant un angle de depouille plus grand au niveau des bords detoures par pincement dans des produits moules a base de copeaux de bois longs Download PDF

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Publication number
WO2001083176A1
WO2001083176A1 PCT/US2000/012056 US0012056W WO0183176A1 WO 2001083176 A1 WO2001083176 A1 WO 2001083176A1 US 0012056 W US0012056 W US 0012056W WO 0183176 A1 WO0183176 A1 WO 0183176A1
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WO
WIPO (PCT)
Prior art keywords
mat
inches
flakes
draft angle
article
Prior art date
Application number
PCT/US2000/012056
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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 US10/019,755 priority Critical patent/US6756105B1/en
Priority to PCT/US2000/012056 priority patent/WO2001083176A1/fr
Priority to CA002378023A priority patent/CA2378023A1/fr
Publication of WO2001083176A1 publication Critical patent/WO2001083176A1/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
    • 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
    • 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
    • B27N3/08—Moulding or pressing

Definitions

  • the present invention relates to the revolutionary wood flake molding technology invented by wood scientists at Michigan Technological University during the latter part of the 1970s.
  • Wood flake molding also referred to as wood strand molding, is a technique for molding three-dimensionally configured objects out of binder coated wood flakes having an average length of about 1 l 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 0.025 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.
  • flakes of wood having the dimensions outlined above are coated with MDI or similar binder and deposited onto a metal tray having one open side, in a loosely felted mat, to a thickness eight or nine times the desired thickness of the final part.
  • the loosely felted mat is then covered with another metal tray, and the covered metal tray is used to carry the mat to a mold.
  • mold and die as well as mold die, are sometimes used interchangeably herein, reflecting the fact that "dies” are usually associated with stamping, and molds are associated with plastic molding, and molding of wood strands does not fit into either category.
  • 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.
  • Patent 4,440,708 and Patent 4,469,216 disclose this technology.
  • the drawings in 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 interleaving 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 hold them together in the loosely felted mat.
  • the drawings of Patent 4,440,708 best illustrate the manner in which a loosely felted mat is compressed by the mold halves into a three 1 dimensionally configured article (see Figs. 2-7, for example).
  • molded wood strand products can be produced having minimal blistering, minimal springback, and minimal over densification to the pinch trimmed edges of the finished product utilizing a mold having a draft angle of ten degrees (10°) or greater for at least a portion of its edge which approaches the pinch trim edge.
  • Fig. 1 is a plane view of a part to be molded of wood strands
  • Fig. 1A is a cross section taken along 1A-1A of Fig. 1;
  • Fig. IB is a cross section taken along IB-IB of Fig. 1;
  • Fig. 2 is an illustration of step 1 in the method of producing molded wood strand products utilizing draft angles of ten degrees (10°) or larger, in which a felted mat of wood strands coated with MDI is placed between the top and bottom dies of the mold;
  • Fig. 3 is an illustration of step 2 of the method, in which the wood strands are consolidated, compressed, and cured under heat and pressure to form the molded wood product;
  • Fig. 4 shows a prior art cross section similar to Fig. 1A, showing the three degree (3°) draft angle previously thought necessary at the pinch trim edge;
  • Fig. 5 is a bottom plane view of the part of Fig. 1, in which edge portions and interior portions of part 1 have been numbered to correspond with Table 1, in which the densities of the numbered portions, and the average draft angle of the numbered edge portions, are recorded.
  • Part 1 made in accordance with a preferred embodiment of the invention has a draft angle 2 of 20° (Fig. 1A), a draft angle 3 at another point of 63°, and a draft angle 4 at another point of 48° (Fig. IB). This is in contrast to a typical prior art part (Fig. 4), where all of the draft angles to the pinch trim edge were about 3°.
  • Fig. 2 illustrates a mold 10 in accordance with a preferred embodiment of the present invention, having a top mold or die 12, and bottom mold or die 13, which is capable of engaging top mold 12 to mold three- dimensionally curved wood strand products from a loosely felted mat 20 of wood flakes. Mold halves 12 and 13 are mounted on heated platens which press the mold halves together and heat them, to thereby heat and press the loosely felted mat 20.
  • Top mold 12 and bottom mold 13 slidably engage one another at pinch trim edges 12a and 13a, respectively, (actually there is a slight space of about 0.030 inches between pinch trim edges 12a and 13a), while compressing and curing a felted mat 20 of resinous binder coated wood strand flakes placed between top mold 12 and bottom mold 13 (Fig. 3).
  • Draft angles 14 and 15 are the angles with respect to the vertical, at which the edges 16 and 17 of the cavity of bottom mold 13 approach pinch trim edges 12a and 13a.
  • Pinch trim edges 12a and 13a are the points at which top mold 12 and bottom mold 13 slidably engage, pinch, and sometimes remove excess flashing/pinch trim 21 from formed part 20' (Fig. 3).
  • the flashing/pinch trim 21 or a portion thereof has to be cleaned off of the finished part. It has been surprisingly found that draft angles 14 and 15 can be ten degrees or larger with minimal or no blistering, minimal or no springback of the wood flakes from over densification causing an unsuitable, inferior, and unusable product.
  • a normal molded pinch trimmed edge for a finished product was expected to have an edge density similar to the interior density.
  • the molded product was expected to have an average edge density of 1.6 times the interior density.
  • the integrity of the pinched trimmed edge is not compromised during the molding process by blistering or excessive springback from over densification.
  • Fig. 1 where draft angles of 20°, 48°, and 63° were used in a molded wood strand product, which did not exhibit blistering or springback from over densification at the pinch trim edges.
  • three dimensionally curved wood strand parts can be molded with draft angles of ten degrees (10°) or greater, without having to worry about blistering or springback from over densification.
  • the density of the edge portion is just significantly greater than that of the interior of the part to increase the structural integrity of the edge of the part.
  • the wood flakes used 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 can be prepared by various conventional techniques. Pulpwood grade logs, or so-called round wood, are converted into flakes 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.
  • a conventional device such as the helical comminuting shear disclosed in U.S. Patent No. 4,053,004
  • Roundwood flakes generally are higher quality and produce stronger parts because the lengths and thickness can be more accurately controlled. Also, roundwood flakes 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 flakes 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 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 flakes can be shorter than 1 A inch, and some can be longer than 6 inches, so long as the overall average length is witliin the above range. The same is true for the thickness.
  • the presence of major quantities of flakes having a length shorter than about 1 l A inch tends to cause the mat to pull apart during the molding step.
  • the presence of some fines in the mat produces a smoother surface and, thus, may be desirable for some applications so long as the majority of the wood flakes, preferably at least 75% , is longer than 1 1/8 inch and the overall average length is at least 1 V ⁇ inch.
  • Substantial quantities of flakes having a thickness of less than about 0.005 inches should be avoided, because excessive amounts of binder are required to obtain adequate bonding.
  • flakes 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 mat. Consequently, excessively high mold pressures are required to compress the flakes into the desired intimate contact with each other.
  • thinner ones produce a smoother surface while thick ones require less binder.
  • the width of the flakes is less important.
  • the flakes 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 flakes 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 the flaker can primarily control the thickness of the flakes.
  • the length and width of the flakes are also controlled to a large degree by the flaking operation. For example, when the flakes 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 flakes are within the desired ranges.
  • both screen and air classification usually are required to adequately remove both the undersize and oversize particles, whereas fingerling flakes usually can be properly sized with only screen classification.
  • Flakes 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 flakes tend to stick together and complicate classification and handling prior to blending.
  • the flakes 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 flakes 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 flakes.
  • the flakes 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 flakes 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 flakes 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 flakes 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 flakes 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 badly 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 polyisocyantes, either alone or combined with urea- or melamine-formaldehyde resins.
  • Particularly suitable polyisocyanates are those containing at least two active isocyanate 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 flakes during the blending step depends primarily upon the specific binder used, size, moisture content and type of the flakes, and the desired characteristics of the part being formed. Generally, the amount of binder added to the flakes is about 2 to about 15 weight % , preferably about 4 to about 10 weight % , as solids based on the dry weight of the flakes. When a polyisocyanate 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 flakes in either dry or liquid form.
  • the binder preferably is applied by spraying droplets of the binder in liquid form onto the flakes 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 flakes during the blending step.
  • the amount of wax added generally is about 0.5 to about 2 weight %, as solids based on the dry weight of the flakes.
  • 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 flakes 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 flakes or "furnish" from the blending step is formed into a loosely-felted, layered mat 20, which is placed within the cavity of bottom mold 13 prior to the molding and curing of the mat into a molded wood particle product.
  • the moisture content of the flakes 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 flakes during molding.
  • the presence of moisture in the flakes facilitates their bending to make intimate contact with each other and enhances uniform heat transfer throughout the mat 20 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 flakes 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 a generally flat, loosely-felted, mat, 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 mat.
  • a dispensing system includes trays, each having one open side, carried on an endless belt or conveyor and one or more (e.g., 3) 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 20 within the cavity of bottom mold 13, by sliding the tray out from under mat 20.
  • the felted mat 20 should preferably have a substantially uniform thickness and the flakes 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 flakes Spacing the forming heads above the carriage so the flakes must drop about 1 to about 3 feet from the heads en route to the carriage can enhance the desired random orientation of the flakes. As the flat flakes fall from that height, they tend to spiral downwardly and land generally flat in a random pattern. Wider flakes within the range discussed above enhance this action.
  • a scalper or similar device spaced above the carriage can be used to ensure uniform thickness or depth of the mat, however, such means usually tend to align the top layer of ftakes, i.e., eliminate the desired random orientation. Accordingly, the thickness of the mat preferably is controlled by closely metering the flow of furnish from the forming heads.
  • the mat thickness used will vary depending upon such factors as the size and shape of the wood flakes, the particular technique used for forming the mat, the desired thickness and density of the mold wood product produced, the configuration of the molded wood product, and the molding pressure to be used.
  • top mold 12 comes almost into contact with bottom mold 13 at pinch trim edges 12a and 13a (leaving a space of about 0.030 inches), such that the excess of mat 20 is pinched off to form flashing/pinch trim portions 21.
  • the wood flakes are compressed and cured under heat and pressure between top mold 12 and bottom mold 13, the flakes bond together to form molded wood part 1 (Fig. 1).

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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

L'invention concerne un procédé permettant la production d'articles (20') moulés à base des particules ou de copeaux longs présentant des arrondis tridimensionnels, avec des angles de dépouille de dix degrés (10°) ou plus grands, sans entraîner de cloquage ou de décollement des particules de bois associé à la surdensification. On dispose un mat de particules de bois, feutré de manière lâche, entre la moitié (12) supérieure et la moitié (13) inférieure d'un moule qui entrent en contact l'un avec l'autre par coulissement au niveau des points (12a, 13a) de pincement, de manière à pincer les bords et éliminer éventuellement les bavures/bord pincés débordants.
PCT/US2000/012056 2000-05-02 2000-05-02 Dispositif et procede permettant un angle de depouille plus grand au niveau des bords detoures par pincement dans des produits moules a base de copeaux de bois longs WO2001083176A1 (fr)

Priority Applications (3)

Application Number Priority Date Filing Date Title
US10/019,755 US6756105B1 (en) 2000-05-02 2000-05-02 Article and method using larger draft angle to pinch trim edge of molded wood strand products
PCT/US2000/012056 WO2001083176A1 (fr) 2000-05-02 2000-05-02 Dispositif et procede permettant un angle de depouille plus grand au niveau des bords detoures par pincement dans des produits moules a base de copeaux de bois longs
CA002378023A CA2378023A1 (fr) 2000-05-02 2000-05-02 Dispositif et procede permettant un angle de depouille plus grand au niveau des bords detoures par pincement dans des produits moules a base de copeaux de bois longs

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
PCT/US2000/012056 WO2001083176A1 (fr) 2000-05-02 2000-05-02 Dispositif et procede permettant un angle de depouille plus grand au niveau des bords detoures par pincement dans des produits moules a base de copeaux de bois longs

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WO2001083176A1 true WO2001083176A1 (fr) 2001-11-08

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Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3354248A (en) * 1965-06-08 1967-11-21 Furnierund Sperrholzwerk J F W Process and machine for producing multidimensionally molded articles
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
US4960553A (en) * 1990-02-12 1990-10-02 Board Of Control Michigan Technological University Method for forming articles having deep drawn portions from matted wood flakes

Patent Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3354248A (en) * 1965-06-08 1967-11-21 Furnierund Sperrholzwerk J F W Process and machine for producing multidimensionally molded articles
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
US4960553A (en) * 1990-02-12 1990-10-02 Board Of Control Michigan Technological University Method for forming articles having deep drawn portions from matted wood flakes

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