CA1285466C - Overlaid corrugated waferboard panel and a process for its manufacture - Google Patents

Overlaid corrugated waferboard panel and a process for its manufacture

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Publication number
CA1285466C
CA1285466C CA000613069A CA613069A CA1285466C CA 1285466 C CA1285466 C CA 1285466C CA 000613069 A CA000613069 A CA 000613069A CA 613069 A CA613069 A CA 613069A CA 1285466 C CA1285466 C CA 1285466C
Authority
CA
Canada
Prior art keywords
overlay
corrugated
panel
mat
planar
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Expired - Fee Related
Application number
CA000613069A
Other languages
French (fr)
Inventor
Lars Bach
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Alberta Research Council
Original Assignee
Alberta Research Council
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 Alberta Research Council filed Critical Alberta Research Council
Priority to CA000613069A priority Critical patent/CA1285466C/en
Application granted granted Critical
Publication of CA1285466C publication Critical patent/CA1285466C/en
Anticipated expiration legal-status Critical
Expired - Fee Related legal-status Critical Current

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Classifications

    • BPERFORMING OPERATIONS; TRANSPORTING
    • B27WORKING OR PRESERVING WOOD OR SIMILAR MATERIAL; NAILING OR STAPLING MACHINES IN GENERAL
    • B27NMANUFACTURE 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
    • B27N5/00Manufacture of non-flat articles
    • BPERFORMING OPERATIONS; TRANSPORTING
    • B27WORKING OR PRESERVING WOOD OR SIMILAR MATERIAL; NAILING OR STAPLING MACHINES IN GENERAL
    • B27NMANUFACTURE 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
    • B27N3/00Manufacture of substantially flat articles, e.g. boards, from particles or fibres
    • B27N3/06Making particle boards or fibreboards, with preformed covering layers, the particles or fibres being compressed with the layers to a board in one single pressing operation

Landscapes

  • 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

"OVERLAID CORRUGATED WAFERBOARD PANEL AND
A PROCESS FOR ITS MANUFACTURE"

Abstract of the Disclosure An overlaid corrugated waferboard panel is provided together with a technique for its manufacture. The overlay may comprise a wood veneer, or the like. The core of the panel comprises wafer board. The single stage process for the panel manufacture involves utilizing a press platen system which is mechanically convertible between a planar and a corrugated configuration. The overlay is first placed on the lower platen which is in the planar configuration. The wafers and a binder resin in admixture are uniformly distributed over the overlay sheet. Optionally, a second overlay sheet is placed over the wafer/binder mat. The platens are biased together to precompress the mat and the overlay in contact therewith. Finally, the platens are converted from the planar to the corrugated configuration, thus forming the overlaid corrugated waferboard panel in a single stage.

Description

~!2~S4~
2 The present invention relates to an overlaid corrugated 3 wafer board panel and to the process for making it.
Typicallyl a wafer board panel comprises layers of wood 6 flakes or wafers formed into a composite structure using a 7 resinous binder. The preparation of wafer board panels is 8 complex, but broadly consists of two principal stages. The first g stage comprises the preparation of the wafers and the admixing thereof to form a loose layer or mat. The second stage involves 11 subsequent compression and heating of the mat to cure the resin 12 and form the consolidated panel.
13 Until recently, wafer board was manufactured in the 14 form of planar or flat sheets. However, as disclosed in U.S.
Patent 4,616,991, the present applicant has developed an 16 apparatus and process for the manufacture of panels having a 17 wave-like or corrugated configuration. Such wave-board panels 18 have improved structural strength properties, relative to planar 19 panels.
This prior patented apparatus involved a pair of 21 opposed, spaced-apart, upper and lower platens. Each platen was 22 formed of adjacent lengths of chain-like links. When the lengths 23 were moved laterally inwardly, they would shift from a planar to 24 an undulating corrugated form.
The process steps involved:
26 distributing a mat of loose wood wafers together 27 with a binder between the upper and lower platen 28 surfaces while they were maintained in the planar ~285466 1 configuration;
2 - biasing the platens together to pre-compress the 3 mat, and thereby substantially fixing the wafers 4 together to limit their further relative movement;
- converting the two platen surfaces, still in 6 pressing association with the mat, from the planar 7 to the corrugated configuration; and 8 - applying additional pressure and heat for a g sufficient time to cure the binder and produce a corrugated wave-board panel.
11 The main advantage inherent in the patented process was 12 that the panel product so formed was characterized by having a 13 substantially uniform density. This was achieved because the 14 wafers were fixed by the pre-compression step and because the mat was not significantly stretched or elongated during the 16 conversion from the planar to the corrugated configuration.
17 It would be an advantage if one could provide an 18 overlaid corrugated panel. By overlaid is meant with veneer, or 19 the like on at least one face thereof. Such veneer-clad product would be useful for high structural strength purposes. By veneer 21 is meant 1-6 mm thick rotary cut wood sheets of substantial size.
22 The manufacture of a corrugated, veneered plywood has 23 been attempted in the prior art has been unsuccessful. This is 24 due to the structural failure of the veneer layer probably because of the particular orientation of the grains lying in a 26 direction perpendicular to the direction of the wavetop of the 27 plywood panel.

~2~35466 SUMMARY OF THE INVENTION
In accordance with the present invention, it has been 3 found that an overlaid corrugated wave-board panel may be 4 manufactured in a single stage. The process involves the concept of:
6 _ utilizing corrugated platens like those described 7 in the '991 patent i.e. platens which are 8 mechanically convertible between a planar and a g corrugated configuration;
~ placing the overlay to be used namely the sheet of 11 veneer or the like, on the lower press platen;
12 _ distributing the mat of loose wood wafers in 13 admixture with a binder onto the overlay sheet;
14 optionally placing a second sheet of overlay over the mat;
16 biasing the platens together to pre-compress the 17 mat substantially fixing the wafers so as to limit 18 their relative movement and bringing the overlay 19 into contact therewith;
- converting the two platen surfaces, still in 21 pressing association with the mat and the overlay, 22 from the planar to the corrugated configuration so 23 as to translate both the overlay and mat in 24 combination in a single stage from the planar to the corrugated overlaid form; and 26 - applying additional pressure (and optionally heat~
27 so as to cure the binder and adhere the overlay to 28 the mat core to thereby provide a cohesive 29 overlaid corrugated wave-board panel.

1 The process relies on the concepts of converting the 2 overlay and mat in combination, in a single stage from the planar 3 to the corrugated form.
4 Nore ~pecifically, it has been determined that in order to manufacture a veneer overlaid corrugated waferboard (wherein 6 the veneer layer is more than l mm thick) the wood veneer grains 7 must be orientated in a direction substantially parallel to the 8 direction of the wave tops. Furthermore, it is preferred that g the moisture content of the core be in the range of between about 5% to about 15~.
11 An advantage of the panels of the present invention and 12 the process thereof resides in the improved strength properties 13 of the panels as will be demonstrated hereinafter.
14 In a first broad aspect, the invention is a corrugated veneer overlaid panel which comprises: a binder-coated wafer 16 core which has been subjected to binder curing and compression 17 and a veneer overlay bonded to one face of said core which 18 overlay has been subjected to compression and densification.
19 In a second broad aspect, the invention is a process for making a corrugated panel having an overlay thereon which 21 comprises: placing the overlay sheet onto the press platen;
22 distributing a mat of loose binder-coated wood wafers between the 23 overlay and the upper press platen or optionally between two 24 overlay sheets, said platens being adapted to be mechanically actuated to move the surfaces together and when further required 26 to be converted from the planar configuration to a wave-like 27 configuration; biasing the platens together vertically to 28 precompress the mat between the planar surfaces to substantially 29 fix the wafers together to limit their further relative movement;

~2~5466 converting the two platens and their platen surfaces still in 2 pressing association with the mat and overlay, from the planar to 3 the corrugated configuration; and applying heat and additional 4 pressure using the platen surfaces to the mat and overlay for a sufficient time to cure the binder and adhere the overlay to the 6 mat and produce a corrugated wafer board panel having an overlay 7 thereover.
9 The overlaid corrugated wafer board panels having a 10 wave-like configuration were prepared using the process and 11 platen system described in U.S. Patent 4,616,991. As stated 12 earlier, the platen system involved a pair of opposed, spaced-13 apart upper and lower platens. Each platen was formed of 14 adjacent lengths of chain-like links. Upon application of a lateral force thereto, the link assembly would move from a planar 16 to a corrugated form. The final outside dimensions of the 17 prepared panels were 24" x 36", the core plus overlay thickness 18 was approximately 11.3 mm (7/16"), and the panel depth wave peak 19 to bottom was 63.5 mm (2-1/2"). Additionally, it can be appreciated that the final panel size can be scaled up to 1220 x 21 4880 mm (4' x 16'). Overlaid boards having panel core plus faces 22 densities approximately 750 kg/m3 were prepared.
23 ~he process for preparing the overlaid corrugated wafer 24 board comprised the following steps.
The furnish could be prepared using various wood 26 species or other fibrous lignocellotic materials e.g. flax or 27 sugarcane. Aspen logs approximately 8' in length and 6" - 14" in 28 diameter were used. The logs were cleaned, debarked, waferized ~Z85~66 1 and screened. The strand or wafer length averaged 76 mm (3 ) and 2 the thickness was about 0.76 mm (O.03"), however other strand or 3 wafer geometrics can be used.
4 The moisture content of the furnish was reduced from the green state to about 5% to 10% using commercial dryers. The 6 wafer was screened following drying.
7 At 5~ moisture content, the furnish was blended with 2%
8 by weight of isocyanate resin and 1~ by weight wax in a g laboratory drum blender.
Resin was utilized as a binder for the wafers and to 11 adhere the veneer or metal overlay to the wafer board core.
12 The wax and wax/resin in admixture were arranged 13 loosely by hand onto the overlay sheet which had been positioned 14 on the lower platen. The quantity of wafers and resin used were sufficient to produce a board having the requisite density.
16 The overlay sheet could comprise veneers such as 17 Douglas fir, Spruce or Pine. The thickness of the sheet would 18 preferably range from between about 1 mm to about 6 mm. The wood 19 grains making up the veneer would be orientated substantially in one direction.
21 In the press, the mat and overlay sheet were subjected 22 simultaneously to high temperature, which set the binder, and to 23 high pressure which compressed the mat to specified thickness, 24 and into adhesive engagement with the overlay sheet. The overlay sheet would be positioned in the press so that the wood grains 26 thereof would be orientated in a direction generally parallel to 27 that of the wave tops. More particularly, the corrugated platen 28 temperature was maintained at 205C. The platen was heated by 29 electrically heated rods extending within the press platens.

~ Z~35466 1 The open or fully extended surface area of the platens 2 was 920 x 920 mm.
3 To obtain pre-compression and corrugation the press was 4 operated in a manual control mode. Once the mat and overlay sheet were in place on the platens, a vertical pre-compression 6 force of less than 3.4 x 106 Newtons were applied. Application 7 of this force brought the top and bottom platens towards one 8 another. At this displacement, the platens were, following pre-g compression, actuated into the corrugated configuration by application of a horizontal side force of less than 0.52 x 106 11 Newtons thereto.
12 It is to be noted that the application of this pressure 13 (of the order of about 450 p.s.i.) imparts a desirable degree of 14 densification to the veneer, thus improving the strength properties thereof in unit volume of same.
16 A final compression was applied by bringing the press 17 platens closer together, until the latter reached their stops.
18 The panel was retained between the press platens for several 19 minutes to allow the resin to set.
Prior to removal of the finished wafer board panel from 21 the press, the pressure was released slowly to avoid steam 22 release damage.
23 The panels were then cooled.

Table I herebelow is included to illustrate 26 the improved structural properties imparted by providing a veneer 27 face to a corrugated wafer board in comparison to a corrugated 28 wafer board and a flat waferboard.

~285466 1 Table I
2 Wafer-core + Wafer Flat 3 Veneer faces of only Waferboard 4 Sample corrugated panel corrugated panel Hoop PineSlash Pine All Wafer All Wafer 6 2.4 mm 2.4 mm No Veneer No Veneer 7 Panel Density 742 752 647 661 8 (kg/mm3) 9 Panel Mass 9.3 9.4 8.6 7.3 ( kg/mm2 ) 11 Wave Length 188 188 188 ---12 (mm) 13 Panel Depth 65 65 65 ___ 14 (mm) Skin* Thickness 10.4 10.4 11.2 11.1 16 (mm) 17 "Strength" 5430 5350 4000 630 18 Unit Max.
19 Bending Noment (N.mm/mm) 21 "Stiffness~ 29.9-106 29.2-106 20.4-106 0.7_106 2232 Unit EI
24 (N-mm/mm) 2 Moisture 5.1% 4.9% 4.1% 2.9%
265 Content 27 * Core + Faces.
28 The corrugated wafer board having no veneer, and having 29 random wafer orientation was used as the control.

Claims (3)

1. A corrugated veneer overlaid panel which comprises: a binder-coated wafer core which has been subjected to binder curing and compression and a veneer overlay bonded to one face of said core which overlay has been subjected to compression and densification.
2. The panel as set forth in claim 1 wherein said overlay comprises a wood veneer having a thickness between about 1 mm to 6 mm and wherein the veneer gains are orientated in a direction substantially perpendicular to that of said wave tops.
3. A process for making a corrugated panel having an overlay thereon which comprises:
placing the overlay sheet onto the press platen;
distributing a mat of loose binder-coated wood wafers between the overlay and the upper press platen or optionally between two overlay sheets, said platens being adapted to be mechanically actuated to move the surfaces together and when further required to be converted from the planar configuration to a wave-like configuration;
biasing the platens together vertically to precompress the mat between the planar surfaces to substantially fix the wafers together to limit their further relative movement and bring the overlay into engagement therewith; and converting the two platens and their platen surfaces still in pressing association with the mat and overlay, from the planar to the corrugated configuration; and applying heat and additional pressure with the platen surfaces to the mat and overlay for a sufficient time to cure the binder and produce a corrugated wafer board panel having an overlay thereover.
CA000613069A 1989-09-25 1989-09-25 Overlaid corrugated waferboard panel and a process for its manufacture Expired - Fee Related CA1285466C (en)

Priority Applications (1)

Application Number Priority Date Filing Date Title
CA000613069A CA1285466C (en) 1989-09-25 1989-09-25 Overlaid corrugated waferboard panel and a process for its manufacture

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
CA000613069A CA1285466C (en) 1989-09-25 1989-09-25 Overlaid corrugated waferboard panel and a process for its manufacture

Publications (1)

Publication Number Publication Date
CA1285466C true CA1285466C (en) 1991-07-02

Family

ID=4140679

Family Applications (1)

Application Number Title Priority Date Filing Date
CA000613069A Expired - Fee Related CA1285466C (en) 1989-09-25 1989-09-25 Overlaid corrugated waferboard panel and a process for its manufacture

Country Status (1)

Country Link
CA (1) CA1285466C (en)

Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN100387413C (en) * 2005-10-25 2008-05-14 南京林业大学 Manufacturing method of large piece wood shaving laminated material

Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN100387413C (en) * 2005-10-25 2008-05-14 南京林业大学 Manufacturing method of large piece wood shaving laminated material

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