Note : Les descriptions sont présentées dans la langue officielle dans laquelle elles ont été soumises.
DESCRIPTION
TITLE
WOODEN BOARD
TECHNICAL FIELD
[0001]
The present invention relates to a wooden board.
BACKGROUND ART
[0002]
In general, tropical plywood, such as lauan plywood, is well known as existing
wooden boards and widely used. In recent years, however, the tropical plywood
itself has
become less easily available due to depletion of raw materials and for
reduction in the
environmental destruction and is thus to be replaced with other types of
wooden boards.
[0003]
Plywood made of domestic conifer as a raw material has no problem of depletion
but insufficient surface properties and is thus used only for a purpose
requiring the strength.
[0004]
OSBs, particle boards (PBs), and MDFs also have no problem in the availability
of
raw materials. With a high strength, OSBs have the problem of insufficient
surface
properties. PBs are inexpensive but have the problem of insufficient strength
and
dimensional stability. MDFs have good surface properties but insufficient
dimensional
stability. In addition, OSBs, PBs, and MDFs have higher densities than
tropical plywood.
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[0005]
In this manner, at present, there is no wooden board satisfying multiple
factors,
such as the strength, the weight, the surface properties, and dimensional
stability in addition
to the stability of the raw material.
[0006]
Patent Documents 1 to 4 suggest typical examples of such types of wooden
boards.
The wooden boards disclosed in Patent Documents 1 and 2 each includes a core
layer, and
a surface layer on at least one surface of the core layer. The core and
surface layers are each
obtained by laminating a large number of thin wood pieces. Patent Document 1
suggests
using, in the wooden board, thin wood pieces with a thickness ranging from
0.50 mm to
1.50 mm in an absolute value for the core layer, and the thin wood pieces with
a thickness
ranging from 0.08 mm to 0.60 mm in an absolute value for the surface layer.
[0007]
On the other hand, in the technique disclosed in Patent Document 3, a fiber
sheet
is pressure-bonded onto the surface of plywood, OSB, or laminated wood, for
example, and
is compressed into a high-density fiber layer to fill and harden the recesses
on the surface
of the base material.
[0008]
Patent Document 4 discloses a floor decorative material obtained by laminating
a
moisture-proof film with a moisture permeability of 7 g/m2 or less for 24
hours on the back
surface of a wooden base material, such as an MDF. Even with a decorative
sheet, with low
moisture permeability, attached to the front surface, the floor decorative
material is less
warped or bent by a large dimensional change.
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CITATION LIST
PATENT DOCUMENTS
[0009]
Patent Document 1: Japanese Unexamined Patent Publication No. f17-47514
Patent Document 2: Japanese Unexamined Patent Publication No. 117-76004
Patent Document 3: Japanese Unexamined Patent Publication No. 2019-31104
Patent Document 4: Japanese Unexamined Patent Publication No. 2019-107894
SUMMARY OF THE DISCLOSURE
TECHNICAL PROBLEMS
[0010]
The wooden boards disclosed in Patent Documents 1 and 2 each includes the core
and surface layers made of the thin wood pieces that are different from each
other not only
in size but also in thickness. There is thus a need to prepare the two types
of thin wood
pieces at the time of production, which inevitably requires time and effort
for the production
and management. In addition, the wooden boards made of the thin wood pieces
described
in the above patent documents have each an uneven surface, that is, cannot
reliably exhibit
surface smoothness sufficient to serve as a floor base material, for example.
[0011]
The wooden board according to Patent Document 3 requires time and effort for
secondary processing of the base material. In addition, since the wooden board
also has the
double structure of the base material and the fiber layer, there is a limit in
reducing the
thickness of the wooden board. The dimensional change caused by moisture
absorption
cannot be reduced.
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[0012]
The decorative material according to Patent Document 4 is a fabricated article
of
the base material, which requires time and effort. In addition, the width of
the moisture-
proof film limits the width of the applicable base material.
[0013]
The present invention was made in view of the problems. It is an objective of
the
present invention to provide a wooden board (or a base material) obtained by
laminating a
large number of thin wood pieces and improved to exhibit a high strength and
excellent
dimensional stability and surface properties and to be easily produced.
SOLUTION TO THE PROBLEM
[0014]
In order to achieve the objective, the present invention provides a wooden
board
obtained as follows. In place of flakes usually used as constituent materials
of OSBs, thin
wood pieces only in small sizes (incl. thicknesses) are used. From these thin
wood pieces,
small thin wood pieces only in smaller sizes are selected as a constituent
material. A large
number of these small thin wood pieces are laminated in an aggregated state
into a wooden
board.
[0015]
In the present invention, wooden layers are laminated and integrated on the
top and
bottom surfaces of the wooden board into a laminated wooden board including a
core layer
and top and bottom layers. The wooden layers are made of, as a constituent
material, tiny
thin wood pieces only in further smaller sizes selected from the small thin
wood pieces.
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[0016]
In the present specification, the "flakes" are pieces cut from raw timber for
an OSB
and typically used as a constituent material of an OSB. The "thin wood pieces"
according
to the present invention are cut from raw timber like "flakes" but are thinner
and smaller
than the "flakes" usually out of the typical thickness range of the "flakes."
The "small thin
wood pieces" according to the present invention fall within the same thickness
range as the
"thin wood pieces" but are smaller than the "thin wood pieces."
[0017]
Specifically, a first aspect of the present invention is directed to a wooden
board
obtained by laminating, adhering, and integrating, in an aggregated state
(aggregated
condition, aggregated manner), a large number of small thin wood pieces with
top and
bottom (front and back) surfaces extending along fibers. The small thin wood
pieces forming
this wooden board have each a thickness ranging from 0.05 mm to 0.35 mm
between the
top and bottom surfaces, and an aspect ratio ranging from 4 to 80 where the
aspect ratio is
defined by (a first length along the fibers as a first direction)/(a second
length in a direction
orthogonal to the fibers as a second direction).
[0018]
In the first aspect of the invention, the wooden board is obtained by
laminating,
adhering, and integrating, in the aggregated state, the large number of small
thin wood pieces
with the thickness ranging from 0.05 mm to 0.35 mm and the aspect ratio
ranging from 4 to
80.
[0019]
The thickness, the first length, and the second length of the small thin wood
pieces
are all expressed in mean. The sizes of a test piece are measured as follows.
The sizes are
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measured at a plurality of points of boards under JIS A 5905:2014 (i.e., a
fiber board) and
JIS A 5908:2015 (i.e., a particle board) using a measuring instrument with an
accuracy
ranging from 1/20 mm to 1 mm and the means of the obtained values are regarded
as the
thickness, width, and length. Under the rule, the thickness, the first length,
and the second
length of the wooden board and the small thin wood pieces forming the wooden
board are
all expressed in mean in the present specification. The accuracy (variation)
of the means of
the respective dimensions of the wooden board and the small thin wood pieces
corresponds,
for example, to the accuracy (accuracy ranging from 1/20 mm to 1 mm) of the
measuring
instrument under the JIS. The accuracy (variation) also corresponds to the
accuracy
(accuracy of settable design values) of the machine used in the step (step P1)
of producing
thin wood pieces or in the step (step P2) of producing small thin wood pieces,
which will
be described later.
[0020]
Like the first aspect, a second aspect of the present invention is directed to
a
wooden board obtained by laminating, adhering, and integrating, in an
aggregated state, a
large number of small thin wood pieces with top and bottom surfaces extending
along fibers.
The small thin wood pieces forming this wooden board each includes the top and
bottom
surfaces with an area of 6 cm2 or less and having a thickness ranging from
0.05 mm to 0.35
mm between the top and bottom surfaces.
[0021]
In the second aspect, the wooden board is obtained by laminating, adhering,
and
integrating, in the aggregated state, the large number of small thin wood
pieces with the area
of 6 cm2 or less and the thicknesses ranging from 0.05 mm to 0.35 mm.
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[0022]
Like the first aspect, a third aspect of the present invention is directed to
a wooden
board obtained by laminating, adhering, and integrating, in an aggregated
state, a large
number of small thin wood pieces with top and bottom surfaces extending along
fibers. The
small thin wood pieces forming this wooden board each includes the top and
bottom surfaces
with an area of 6 cm2 or less and has an aspect ratio ranging from 4 to 80
where the aspect
ratio is defined by (a first length along the fibers)/(a second length in a
direction orthogonal
to the fibers).
[0023]
In the third aspect, the wooden board is obtained by laminating, adhering, and
integrating, in the aggregated state, the large number of small thin wood
pieces with the area
of 6 cm2 or less and the aspect ratio ranging from 4 to 80.
[0024]
That is, the first to third aspects each specifies any two of the thickness
(0.05 mm
to 0.35 mm), the aspect ratio (4 to 80), and the area (6 cm2 or less) of the
small thin wood
pieces forming the wooden board.
[0025]
The wooden board according to the first to third aspects includes only the
small
thin wood pieces in one type of size obtained as follows. In the step P 1 ,
which will be
described later, thin wood pieces with a specific thickness are obtained. In
the step P2, which
will also be described later, these thin wood pieces are crushed in a first
direction (i.e., along
fibers) of the wood pieces and a second direction orthogonal to the first
direction (i.e.,
orthogonal to the fibers). Being significantly thin within the narrow range
from 0.05 mm to
0.35 mm, the large number of small thin wood pieces are uniform in thickness
with little
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variation. In addition, the aspect ratio defined by (the mean first
length)/(the mean second
length) is within the certain range, and thus the small thin wood pieces
uniform in shape
within a certain range are aggregated into a homogeneous wooden board.
Moreover,
including the top and bottom surfaces with the area within the narrow range of
6 cm2 or less,
the large number of small thin wood pieces are uniform in area (size) with
little variation.
Accordingly, the wooden board not only has a higher strength but is less
warped by moisture
absorption and desorption, and thus exhibits dimensional stability as
excellent as tropical
plywood. In addition, since the large number of small thin wood pieces are
uniform in
thickness, shape, and size, the resultant wooden board has no significant
unevenness on the
surfaces unlike typical OSBs and thus exhibits excellent surface properties.
Since the large
number of small thin wood pieces uniform in size are aggregated and laminated,
the wooden
board is produced easily.
[0026]
Like the first to third aspects, a fourth aspect of the present invention is
directed to
a wooden board obtained by laminating, adhering, and integrating, in an
aggregated state, a
large number of small thin wood pieces with top and bottom surfaces extending
along fibers.
The small thin wood pieces forming this wooden board each includes the top and
bottom
surfaces with an area of 6 cm2 or less, has a thickness ranging from 0.05 mm
to 0.35 mm
between the top and bottom surfaces, and has an aspect ratio ranging from 4 to
80 where the
aspect ratio is defined by (a first length along the fibers)/(a second length
in a direction
orthogonal to the fibers).
[0027]
In the fourth aspect, the wooden board is obtained by laminating, adhering,
and
integrating, in the aggregated state, the large number of small thin wood
pieces with the area
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of 6 cm2 or less, the thickness ranging from 0.05 mm to 0.35 mm, and the
aspect ratio
ranging from 4 to 80. That is, the fourth aspect specifies all the three of
the thickness (0.05
mm to 0.35 mm), the aspect ratio (4 to 80), and the area (6 cm2 or less) of
the small thin
wooden pieces forming the wooden board. This configuration further increases
the
dimensional stability and further improves the surface properties of the
wooden board.
[0028]
Like the first to fourth aspects, a fifth aspect of the present invention is
directed to
a wooden board obtained by laminating, adhering, and integrating, in an
aggregated state, a
large number of small thin wood pieces with top and bottom surfaces extending
along fibers.
The small thin wood pieces forming this wooden board each have a bulk density
ranging
from 10 kg/m3 to 150 kg/m3, and includes the top and bottom surfaces with an
area of 6 cm2
or less.
[0029]
In the fifth aspect, the wooden board is obtained by laminating, adhering, and
integrating, in the aggregated state, the large number of small thin wood
pieces having the
bulk density ranging from 10 kg/m3 to 150 kg/m3 and including the top and
bottom surfaces
with the area of 6 cm2 or less.
[0030]
Like in the first to fourth aspects, a wooden board according to a fifth
aspect of the
present invention is made only of small thin wood pieces in one type of size.
With the
specified bulk density and area of the top and bottom surfaces, the large
number of small
thin wood pieces are significantly thin and uniform in thickness with little
variation. In
addition, the large number of small thin wood pieces are uniform in size with
little variation
in the first length in the first direction (i.e., along fibers) and the second
length in the second
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direction (i.e., orthogonal to the fibers). In this manner, the small thin
wood pieces uniform
in thickness and size within certain ranges are aggregated into a homogeneous
wooden
board. Accordingly, the wooden board not only has a higher strength but is
less warped by
moisture absorption and desorption, and thus exhibits dimensional stability as
excellent as
tropical plywood. In addition, since the large number of small thin wood
pieces are uniform
in thickness and size, the resultant wooden board has no significant
unevenness on the
surfaces unlike usual OSBs and thus exhibits excellent surface properties.
Since the large
number of small thin wood pieces uniform in thickness and size are aggregated
and
laminated, the wooden board is produced easily.
[0031]
A sixth aspect of the present invention is directed to a laminated wooden
board
obtained by laminating and integrating a wooden layer on each of the top and
bottom
surfaces of the wooden board of any one of the first to fifth aspects. The
wooden layer
serving as each of the top and bottom layers of this wooden layer is obtained
by laminating,
adhering, and integrating, in an aggregated state, tiny thin wood pieces with
a smaller area
than the small thin wood pieces. Note that the "area" is represented by a
numerical value
obtained by multiplying the first length by the second length, and refers to
the area of the
top and bottom surfaces along the fibers.
[0032]
In the sixth aspect, the laminated wooden board is obtained by laminating and
integrating the wooden board serving as the core layer and the wooden layers
serving as the
top and bottom surfaces. The wooden layer is obtained by laminating, adhering,
and
integrating, in the aggregated state, the large number of tiny thin wood
pieces with the
smaller area than the small thin wood pieces.
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[0033]
In this manner, the laminated wooden board includes only the small thin wood
pieces in two types of sizes obtained as follows. In the step Pl, which will
be described later,
thin wood pieces with a specific thickness are obtained. In the steps P2 and
P6, which will
also be described later, these thin wood pieces are crushed in a first
direction (i.e., along
fibers) of the wood pieces and a second direction orthogonal to the first
direction (i.e.,
orthogonal to the fibers). Including, as the core layer, the wooden board made
of the small
thin wood pieces, the laminated wooden board provides at least the same
advantages as the
wooden board according to the first aspect. In the laminated wooden board, the
wooden
layer made of a large number of tiny thin wood pieces with a smaller area than
the small
thin wood pieces is laminated on each surface of the wooden board so as to
serve as the
front or back layer. The laminated wooden board has no significant unevenness
on the
surfaces unlike usual OSBs and thus exhibits further improved surface
properties that are as
excellent as MDFs. The aggregate of the large number of tiny thin wood pieces
uniform in
size, the aggregate of the large number of small thin wood pieces uniform in
size, and the
aggregate of the large number of tiny thin wood pieces are sequentially
laminated and
integrated. Accordingly, the laminated wooden board is produced easily.
[0034]
A seventh aspect of the present invention is directed to the wooden board
(i.e., the
laminated wooden board) of the sixth aspect. In the seventh aspect, the wooden
layer has a
thickness accounting for 5% to 40% of a total thickness of the wooden board.
With this
configuration, the laminated wooden board can exhibit both a high strength and
excellent
surface properties.
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[0035]
An eighth aspect of the present invention is directed to the wooden board of
any
one of the first to the seventh aspects with a density ranging from 500 kg/m3
to 800 kg/m3.
This configuration further increases the strength of the wooden board.
[0036]
A ninth aspect is directed to the wooden board of any one of the first to the
eighth
aspects. In the ninth aspect, the wooden board has a root mean square height
Sq ranging
from 0.005 gm to 0.015 gm on a surface, or an arithmetic average height Sa
ranging from
0.002 gm to 0.007 gm on the surface. This configuration further improves the
surface
properties of the wooden board. In the present specification, the surface
properties of the
wooden board are the surface characteristics of the wooden board adjusted to a
product
thickness using a sander of #150, for example.
ADVANTAGES OF THE INVENTION
[0037]
As described above, in the present invention, a wooden board obtained by
laminating, adhering, and integrating, in an aggregated state, a large number
of small thin
wood pieces with top and bottom surfaces extending along fibers. For the small
thin wood
pieces, at least two of the following are specified within narrow ranges: the
thicknesses, the
aspect ratio defined by (the first length)/(the second length); or the size of
the top and bottom
surfaces. Alternatively, the bulk density and the area of the top and bottom
surfaces are
specified in narrow ranges. The large number of small thin wood pieces are
uniform in size
with little variation. Accordingly, the wooden board has a higher strength,
dimensional
stability and surface properties as excellent as tropical plywood, and is thus
produced easily.
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BRIEF DESCRIPTION OF THE DRAWINGS
[0038]
FIG. 1 is a cross-sectional view of a wooden board according to a first
embodiment
of the present invention.
FIG. 2 is an enlarged cross-sectional view of the main part of the wooden
board
according to the first embodiment.
FIG. 3 is an enlarged perspective view schematically showing small thin wooden
pieces forming the wooden board according to the first embodiment.
FIG. 4 shows a process of producing the wooden board according to the first
embodiment.
FIG. 5 is an enlarged cross-sectional view showing that the wooden board
according to the first embodiment is obtained by hot-pressing a sheet (mat)
which is an
aggregate of small thin wood pieces.
FIG. 6 shows the characteristics of the wooden board according to the first
embodiment in comparison with boards of other materials.
FIG. 7 is a cross-sectional view of a wooden board according to a second
embodiment of the present invention.
FIG. 8 is an enlarged cross-sectional view of the main part of the wooden
board
according to the first embodiment.
FIG. 9 is an enlarged perspective view schematically showing tiny thin wood
pieces
forming a wooden layer according to the second embodiment.
FIG. 10 shows a process of producing the wooden board according to the second
embodiment.
FIG. 11 is an enlarged cross-sectional view showing that the wooden board
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according to the second embodiment is obtained by hot-pressing sheets which
are each an
aggregate of small thin wood pieces or tiny thin wood pieces.
FIG. 12 shows the characteristics of the wooden board according to the second
embodiment in comparison with boards of other materials.
DESCRIPTION OF EMBODIMENTS
[0039]
Now, embodiments of the present invention will be described in detail with
reference to the drawings. Note that the following description of the
embodiments is merely
an example in nature, and is not intended to limit the scope, applications, or
use of the
present disclosure.
[0040]
[First Embodiment]
<Wooden Board>
FIG. 1 shows a wooden board As according to a first embodiment of the present
invention. The wooden board As has a density ranging from 500 kg/m3 to 800
kg/m3 and a
thickness ranging from 3 mm to 12 mm, for example. A wooden board As with a
small
thicknesses ranging from 3 mm to 6 mm are used as, for example, an inner wall
material for
a cargo bed of a vehicle, such as a truck, a base material for an indoor
cushioned floor, a
decorative surface material, and an interior material, such as an interior
building material
(e.g., a riser). A wooden board As with a medium thickness ranging from 6 mm
to 12 mm is
used as the base material of an indoor soundproof floor or a floor for walking
with shoes on,
or an entrance finishing material, for example. In this manner, the wooden
board As is used
as a substitute for the existing plywood for a base plate. This wooden board
As will be
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described in detail.
[0041]
As shown in an enlarged view of FIG. 2, the wooden board As is obtained by
laminating, adhering, and integrating, in an aggregated state, a large number
of small thin
wood pieces 1, 1, . . . with top and bottom surfaces extending along the
fibers. The large
number of small thin wood pieces 1, 1,. . . have one type of thickness.
[0042]
The small thin wood pieces 1 will be described. As shown in an enlarged view
of
FIG. 3, the small thin wood pieces 1 have a thickness t preferably ranging
from 0.05 mm to
0.35 mm (0.05 mm or more and 0.35 mm or less), more preferably ranging from
0.10 mm
to 0.30 mm, still more preferably ranging from 0.15 mm to 0.25 mm, and further
more
preferably ranging from 0.15 mm to 0.20 mm. These thin pieces 1, 1, . . . with
the small
thickness t determine the characteristics of the wooden board As. The
thickness t of the small
thin wood pieces 1 is expressed in mean. In other words, while strands (also
referred to as
"flakes" in the present invention) usually used as an element (i.e., a
constituent material) of
typical OSBs typically have a thickness ranging from about 0.6 mm to about 1.5
mm, the
small thin wood pieces 1 are thin pieces thinner than the strands.
[0043]
The following is the relationship between the small thin wood pieces 1 and the
advantages of the wooden board As made of the small thin wood pieces 1 as a
constituent
material. The small thin wood pieces 1 have a thickness t within the specific
narrow range
described above between the top and bottom surfaces. For example, a wood board
As is
made of small thin wood pieces 1 with a thickness t of 0.3 mm, where the first
and second
lengths dl and d2 are determined by the aspect ratio, the area, or the bulk
density which will
CA 03216124 2023- 10- 19
be described later. This wooden board As has a significantly higher Young's
modulus of
bending (i.e., rigidity) than a comparative wooden board (specifically the
wooden board As
has 4560, while the comparative wooden board has 3764), where the comparative
wooden
board is made of, as a constituent material, comparative thin wood pieces with
a thickness t
changed to 0.4 mm. As compared to the comparative wooden board, the wooden
board As
is significantly excellent in the root mean square height Sq and the
arithmetic mean height
Sa on the surface measured after water absorption and drying (specifically,
the wooden
board As has Sq of 0.008 gm, while the comparative wooden board has Sq of
0.079 gm. The
wooden board As has Sa of 0.005 gm, while the comparative wooden board has Sa
of 0.059
gm). Note that Sq and Sa of the wooden board As fall within the range of the
surface
properties of the wooden board As which will be described later. That is, the
wooden board
As exhibits particularly improved strength and surface properties by
specifying the
thicknesses of the small thin wood pieces 1 to 0.35 mm or less.
[0044]
The small thin wood pieces 1 have an aspect ratio (dl/d2) ranging from 1 to 80
where the aspect ratio is defined by (a mean first length d1)/(a mean second
length d2) which
is a ratio between the mean of a first length dl in a first direction and the
mean of a second
length d2 in a second direction orthogonal to the first direction in one
preferred embodiment.
That is, the small thin wood pieces 1 may be in a square shape or an elongated
shape (i.e., a
strip shape). In particular, the small thin wood pieces 1 are in an elongated
shape with an
aspect ratio ranging from 4 to 80 in one more preferred embodiment. With
respect to the
small thin wood pieces 1 in an elongated shape, the first length dl is the
longitudinal size
(i.e., length). The small thin wood pieces 1 include fibers la, la, . . . such
as vessels or
tracheids, for example, and the first length dl is the length along the fibers
1 a. The second
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length d2 is the transverse size (i.e., width), for example, the size in the
direction orthogonal
to the fibers. The aspect ratio preferably ranges from 2 to 70, more
preferably ranges from
3 to 55, and still more preferably ranges from 4 to 40. As will be described
later, although
not shown in the drawings, the small thin wood pieces 1 are obtained by
crushing thin wood
pieces (also referred to as "cut thin wood pieces") as cut from raw timber
into smaller sizes.
The small thin wood pieces 1 are called so to be distinguished from these cut
thin wood
pieces.
[0045]
The small thin wood pieces 1 have the top and bottom surfaces with an area (a
numerical value obtained by multiplying the first length dl by the second
length d2, i.e., dl
x d2) of preferably 64 cm2 or less, more preferably 32 cm2 or less, still more
preferably 16
cm2 or less, and further more preferably 6 cm2 or less. The lower limit of the
area is 0.5 cm2
or more, for example.
[0046]
The small thin wood pieces 1 have a bulk density ranging from 10 kg/m3 to 150
kg/m3 in one preferred embodiment. In the present specification, the bulk
density is defined
by the mass of the small thin wood pieces 1, 1, . . . with respect to the
volume of the small
thin wood pieces 1, 1,. . . filling a container (hereinafter also referred to
as a "measurement
container") with a certain volume, and is represented by the following
equation (1).
[Math 1]
Bulk Density = Mass of Small Thin Wood Pieces Filling Measurement
Container/Volume
of Small Thin Wood Pieces. . . (1)
[0047]
In the equation (1), the "Mass of Small Thin Wood Pieces Filling Measurement
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Container" is the total mass of the large number of small thin wood pieces 1,
1, . . . that can
fill the measurement container, excluding the mass of the measurement
container. The mass
of the small thin wood pieces filling the measurement container is measured,
for example,
as follows. The small thin wood pieces 1, 1, . . . are piled up in the
measurement container
without gaps. The tops of the piled small thin wood pieces 1, 1,. . . are
flattened to be flush
with each other using a ruler, spatula, or any other suitable tool without
applying any
pressure. In this state, the mass (i.e., the sum of the masses of the
measurement container
and the large number of small thin wood pieces 1, 1, . . . ) was measured. The
mass of the
measurement container is then subtracted from the obtained mass. The mass can
be
measured using a typically commercially available measuring instrument.
[0048]
In the equation (1), the "Volume of Small Thin Wood Pieces" refers to the
total
volume of the large number of small thin wood pieces 1, 1, . . . that can fill
the measurement
container. Specifically, the volume refers to the total volume of the large
number of small
thin wood pieces 1, 1, . . . contained flush in the measurement container.
Used as an
approximate value to the "Volume of Small Thin Wood Pieces" may be the
internal volume
of the measurement container.
[0049]
The bulk density defined as described above can be the density when the small
thin
wood pieces 1, 1, . . . fully fill the measurement container and the internal
volume thereof
is regarded as the volume. The small thin wood pieces 1, 1, . . . with a bulk
density within
the specific range from 10 kg/m3 to 150 kg/m3 determine the characteristics of
the wooden
board As. Specifically, the strands (i.e., flakes) of an OSB have a bulk
density greatly
exceeding 150 kg/m3. Here, the bulk density correlates with the thickness of
the pieces.
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Specifically, there is believed to be a tendency that the bulk density
decreases with a
decrease in the thickness of the pieces. Since the small thin wood pieces 1
are thinner pieces
than the strands of an OSB and thus believed to have a lower bulk density. The
small thin
wood pieces 1 have a bulk density preferably ranging from 10 kg/m3 to 100
kg/m3, more
preferably ranging from 20 kg/m3 to 90 kg/m3, still more preferably ranging
from 30 kg/m3
to 80 kg/m3, and further more preferably ranging from 40 kg/m3 to 70 kg/m3.
[0050]
The small thin wood pieces 1, 1, . . . with a bulk density within a specific
range are
thinner pieces than the strands (i.e., flakes) of an OSB, and have the first
length dl in the
first direction and the second length d2 in the second direction orthogonal to
the first
direction both within certain narrow ranges. That is, the bulk density
determines the
thicknesses t and the first and second lengths dl and d2 of the small thin
wood pieces 1.
Both the first and second lengths dl and d2 of the small thin wood pieces 1
are expressed
in mean.
[0051]
For some of the small thin wood pieces 1, 1, . . . (hereinafter, referred to
as "first
small thin wood pieces 1, 1, . . . " when individually described) with the
configuration
described above, at least two of the following are specified within narrow
ranges: the
thickness t, the aspect ratio (dl/d2) defined by (the first length d1)/(the
second length d2),
or the area (dl x d2) of the top and bottom surfaces. Others of the small thin
wood pieces 1,
1, . . . (hereinafter referred to as "second small thin wood pieces 1, 1, . .
. " when
individually described), the bulk density and the area of the top and bottom
surfaces are
specified within narrow ranges.
19
CA 03216124 2023- 10- 19
[0052]
The tree species used for the small thin wood pieces 1 is not particularly
limited.
Examples include a tropical tree, a broadleaf tree, or any other suitable tree
species.
Examples include cedar, cypress, firs such as Douglas fir, acacia, aspen,
poplar, pines (e.g.,
hard pine, soft pine, and radiata pine), birch, and rubber (i.e., rubber
tree). The tree species
are however not limited thereto and may further include various tree species.
Examples of
the various tree species include domestic timber, boreal timber, tropical
timber, and other
overseas timber. Examples of the domestic timber include Sakhalin fir,
Japanese larch, Ezo
spruce, Sawara cypress, Hiba cypress, Japanese torreya, Japanese hemlock,
Japanese yew,
various pines, paulownia, maple, birch (white birch), chinquapin, beech, oak,
fir, sawtooth
oak, Japanese oak, camphor, and Japanese zelkova. Examples of the boreal
timber include
cypress, Alaska cedar, red cedar, noble fir, spruce, western hemlock, and
redwood.
Examples of the tropical timber include agathis, terminalia, lauan, meranti,
jongkong,
kamerere, calampayan, amberoi, melina, teak, apitong, and sengonlaut. Examples
of other
overseas timber include balsa, cedro, mahogany, lignum vitae, acacia mangium,
Mediterranean pine, bamboo, sorghum, and kamerere. Any timber is applicable.
[0053]
As the physical properties, the density of the small thin wood pieces 1 is
preferably
250 kg/m3 or more, and more preferably 300 kg/m3 or more. On the other hand,
the density
is preferably 800 kg/m3 or less, more preferably 500 kg/m3 or less, and still
more preferably
400 kg/m3 or less. A density less than 250 kg/m3 requires a thicker sheet to
form the wooden
board As with the same density and strength and a higher pressure for hot-
pressing in the
press forming step.
CA 03216124 2023- 10- 19
[0054]
The small thin wood pieces 1 may have a density exceeding 800 kg/m3, which are
however not easily available. That is, the upper limit of the density is not
necessarily 800
kg/m3 and may be higher, if small thin wood pieces 1 with a density exceeding
800 kg/m3
are easily available.
[0055]
The small thin wood pieces 1 have a water content preferably ranging from
about
2% to about 20%, and more preferably ranging from 2% to 8%. It takes a longer
time to
soften the small thin wood pieces 1 with a water content less than 2% in the
hot-pressing in
the press forming step, that is, a longer pressing period, which may lower the
strength.
[0056]
On the other hand, it takes a longer time to heat and compress the small thin
wood
pieces 1 with a water content exceeding 20% in the hot-pressing. In addition,
the curing of
the adhesive may be inhibited, which may lower the strength.
[0057]
In the wooden board As, the fibers 1a, 1a, . . . of the large number of small
thin
wood pieces 1, 1 , . . . may be oriented in a reference direction (i.e., the
longitudinal direction
of the fibers corresponds to the reference direction), but not necessarily
have such an
orientation and may lie randomly. With the expression "the fibers 1a, 1a, . .
. of the large
number of small thin wood pieces 1, 1, . . . may be oriented in a reference
direction", the
fibers la, 1a, . . . of all the small thin wood pieces 1, 1, . . . are not
necessarily oriented in
exactly the same direction in the wooden board As, in other words, the
oriented fibers of the
small thin wood pieces 1, 1 , . . . are not necessarily parallel to each
other. Some of the small
thin wood pieces 1, 1, . . . may include fibers inclined at a certain angle
(e.g., about 20 )
21
CA 03216124 2023- 10- 19
from the reference direction.
[0058]
<Method of Producing Wooden Board>
Next, methods of producing the small thin wood pieces 1 and producing the
wooden board As from the small thin wood pieces 1 will be described with
reference to FIG.
4. The method of producing the small thin wood pieces 1 includes a step P1 of
producing
thin wood pieces and a step P2 of producing small thin wood pieces. The method
of the
wooden board As further includes subsequent steps, namely, a step P3 of
applying an
adhesive, a step P4 of forming a sheet (mat), and a step P5 of hot-pressing.
[0059]
(Step P1 of Producing Thin Wood Pieces)
Raw timber, such as a log or a thinned wood, as a material is cut into short
lengths
and its bark is removed if necessary, and the water content is then adjusted
in some cases.
The raw timber is cut with an outer or inner blade cutter (or strander) into a
large number of
thin wood pieces (cut thin wood pieces) thinner and smaller than flakes
usually used as
constituent materials of OSBs. The thin wood pieces can also be made of a
scrap material,
a waste material, or a waste pallet material available at a construction or
any other site. Used
here is a typical cutter. The thickness of the thin wood pieces is adjusted by
the speed of
feeding the raw timber into the cutter. The thin wood pieces (i.e., the cut
thin wood pieces)
formed by this cutting are different from the small thin wood pieces 1 forming
the wooden
board As according to this embodiment, and have a larger area (specifically,
length in the
direction orthogonal to the fibers) than the small thin wood pieces 1.
[0060]
At this time, cutting is performed so that fibers appear linearly on the top
and
22
CA 03216124 2023- 10- 19
bottom surfaces of the thin wood pieces and the resultant thickness is equal
to the thickness
t of the small thin wood pieces 1. This is because, in the subsequent steps,
the thickness t of
the small thin wood pieces 1 does not change basically from the thickness of
the cut thin
wood pieces. The thickness of the cut thin wood pieces remains as the
thickness t of the
small thin wood pieces 1.
[0061]
The cut thin wood pieces obtained in this step P1 may pass through a sieve
(e.g., a
mesh with 05 mm or more) or any other suitable tool so as to be sorted (i.e.,
classified)
according to sizes. Through the procedure (i.e., the classification step),
thin wood pieces
may be obtained in a size (within a size range of the first small thin wood
pieces 1, 1,. . . )
corresponding to that of the small thin wood pieces 1, 1, . . . obtained after
the subsequent
step P2 of producing small thin wood pieces. In this case, these thin wood
pieces can be
used as the small thin wood pieces 1, 1,. . . in the step P3 of applying an
adhesive, without
being subjected to the step P2 of producing small thin wood pieces.
[0062]
(Step P2 of Producing Small Thin Wood Pieces)
Next, after the cutting, the thin wood pieces (cut thin wood pieces)
classified as
necessary are crushed using a crusher into sizes in the direction orthogonal
to the fibers
smaller than the thin wood pieces immediately after the cutting to obtain
small thin wood
pieces 1, 1, . . . for forming the wooden board As. The crusher may be a
hammer mill, a pin
mill, or a jet mill without any cutter, or may be a knife piecer or a cutter
mill with a cutter.
At this time, made of the cut thin wood pieces crushed in the transverse
direction so as to
be split along the fibers (i.e., the longitudinal direction), elongated small
thin wood pieces
1, 1,. . . can be produced. In other words, with a force (impact) applied
orthogonally to the
23
CA 03216124 2023- 10- 19
fibers, the cut thin wood pieces are not easily broken. On the other hand,
with a force applied
along the fibers, the thin wood pieces are easily broken. Even if curved, the
cut thin wood
pieces are divided into planes by the crushing. The force is not necessarily
applied to the cut
thin wood pieces along the fibers. With a force applied in a random direction,
the cut thin
wood pieces are usually broken from weak points (easily broken in weak
directions). The
force (force in the direction orthogonal to the fibers) of connecting the
fibers of the cut thin
wood pieces is much weaker than the force along the fibers. When crushed (a
force is
applied) in a random direction using the typical crusher described above, the
cut thin wood
pieces are broken along the fibers to be shorter in the direction orthogonal
to the fibers into
elongated small thin wood pieces 1, 1, . . . .
[0063]
Even if the cut thin wood pieces have knots, such knots are more fragile than
other
portions, and thus pulverized by crushing and removed in the subsequent
classification step.
[0064]
A crusher with a cutter may unintentionally crush the cut thin wood pieces in
the
direction orthogonal to the fibers. By contrast, a crusher without any cutter
is less likely to
have such the problem and is thus used in one preferred embodiment to crush
the cut thin
wood pieces.
[0065]
In this manner, raw timber is subjected not to one stage of the cutting step
only but
to two stages including the subsequent crushing step. Accordingly, from the
cut thin wood
pieces, which are thinner and smaller than the flakes, high-strength small
thin wood pieces
1, 1,. . . can be produced easily in a required size without knots.
24
CA 03216124 2023- 10- 19
[0066]
The process may include a classification step of causing the small thin wood
pieces
1, 1,. . . obtained in the crushing step to pass through a sieve or any other
suitable tool, and
sorting (classifying) the small thin wood pieces 1, 1, . . . . according to
sizes. Accordingly,
the large number of small thin wood pieces 1, 1,. . . become finer and more
uniform in size
and shape. From the foregoing, the small thin wood pieces 1 are produced.
[0067]
(Step P3 of Applying Adhesive)
The large number of small thin wood pieces 1, 1, . . . , fine and uniform in
size and
shape are obtained by sorting in the step P2 of producing small thin wood
pieces. The step
P3 of applying an adhesive is then performed. These small thin wood pieces 1,
1, . . . are
transferred into adhesive application equipment and applied with an adhesive.
The adhesive
may be an isocyanate-based adhesive, for example. Besides, for example, a
phenolic resin,
an amine-based adhesive, such as a urea resin or a melamine resin, or a
natural product for
wood (tannin)-based adhesive may be used. In combination with the adhesive, a
generally
used water repellent may be used.
[0068]
(Step P4 of Forming Sheet)
Next, as shown on the left of FIG. 5, the large number of small thin wood
pieces 1,
1,. . . applied with the adhesive are laminated (stacked) to a predetermined
thickness (i.e.,
height) in an aggregated state along the thickness with or without being
oriented along the
fibers to form a sheet Al of the small thin wood pieces 1, 1, . . . . In order
to form a wooden
board As with a thickness of 4 mm, for example, small thin wood pieces 1, 1, .
. . with a
thickness t of 0.2 mm are stacked so that the resultant sheet Al has a
thickness (i.e., height)
CA 03216124 2023- 10- 19
of about 40 mm.
[0069]
(Step P5 of Hot-Pressing)
The sheet Al is transferred into a hot press machine, set between hot plates,
and
subjected to hot-pressing at predetermined pressure and temperature in the hot
press
machine so as to be compressed and integrally formed by curing the adhesive.
Accordingly,
the wooden board As shown in FIG. 1 is formed.
[0070]
At this time, as shown in FIG. 5, the illustrated sheet Al with a thickness of
about
40 mm is compressed into the wooden board As with a thickness of 4 mm, for
example, that
is, a one-tenth thickness. The pressing temperature for the hot-pressing is
not particularly
limited but may range from 100 C to 180 C, for example. The pressing pressure
in the hot-
pressing ranges from 2 Nimm2 to 4 Nimm2, for example. The pressing period is
one to two
minutes, for example. The pressing period depends on the thickness of the
wooden board
As and may be shorter than one minute or longer than two minutes. A preheating
using a
heating machine may be performed before the hot-pressing using the hot press
machine.
[0071]
The small thin wood pieces 1, 1, . . . have their knots removed and are kept
in a
fine size without variation and the whole sheet Al is thus homogeneous, which
causes less
variation in the strength of the wooden board As. On the other hand, a strand
board made of
large strands (i.e., flakes) has, due to a non-uniform sheet including knots,
for example, low-
density or small-thickness and low-strength portions (or spots), causing
variation in the
strength. In addition, the sheet Al made of thinner small thin wood pieces 1,
1, . . . has a
higher homogeneity, and the resultant wooden board As thus tends to exhibit a
higher
26
CA 03216124 2023- 10- 19
strength. In general, a strand board made of large strands (i.e., flakes) can
exhibit a higher
strength. In the present invention, the wooden board As has homogeneity and
strength with
the small thin wood pieces 1 obtained by further miniaturizing the thin wood
pieces (i.e.,
cut thin wood pieces), which are thinner and smaller than the flakes, by
crushing.
[0072]
The small thin wood pieces 1, 1, . . . are small and uniform in size with gaps
left
evenly in the sheet Al. Even if the small thin wood pieces 1, 1, . . . in the
sheet Al are hot-
pressed, while containing a relatively large amount of moisture, vapor
generated by
evaporation of the moisture is smoothly released from the sheet Al. That is,
as shown on
the left of FIG. 5, the sheet Al includes a large number of small voids
between the adjacent
small thin wood pieces 1, 1, . . . . These voids communicate with each other
not only along
and orthogonally to the fibers of the small thin wood pieces 1, 1, . . . but
also along the
thickness, and are continuous three-dimensionally. This configuration causes
less puncture
at the stop of applying pressure onto the wooden board As.
[0073]
Through these steps, the wooden board As is formed which has a density ranging
from 500 kg/m3 to 800 kg/m3 and a Young's modulus of bending ranging from 3.5
GPa to
7.0 GPa. As shown on the right of FIG. 5, this wooden board As includes
(retains) a large
number of three-dimensionally continuous small voids. Accordingly, the wooden
board As
also has an excellent air permeability.
[0074]
(Other Steps)
The method of producing the wooden board As may further include, as another
step,
a finish step after the step P5 of hot-pressing. In the finish step, the
wooden board As is
27
CA 03216124 2023- 10- 19
cured to an equilibrium water content and then the top and bottom surfaces of
the wooden
board As are ground by a sander to adjust the final thicknesses of the wooden
board As. The
sander may be a generally used one and is #150, for example. Through this
finish step, the
wooden board As with more excellent surface properties can be obtained.
[0075]
<Surface Properties of Wooden Board>
The wooden board As preferably has a root mean square height Sq ranging from
0.005 pm to 0.015 gm or an arithmetic mean height Sa ranging from 0.002 gm to
0.007 gm
on the surface. The surface of the wooden board As refers to the surface of
the wooden board
As after the finish step, and, for example, refers to the surface of the
wooden board As
adjusted to a product thickness using a sander #150. The root mean square
height Sq and
the arithmetic mean height Sa are surface roughness parameters representing
the surface
properties under ISO 25178. That is, the wooden board As has excellent surface
properties
with the parameters Sq and Sa specifying the surface properties of the wooden
board As
controlled within specific ranges.
[0076]
The root mean square height Sq is a parameter corresponding to the standard
deviation of the distance from the mean plane, and corresponds to the standard
deviation of
the height. With a decreasing root mean square height Sq, the surface of the
wooden board
As has less significant unevenness and thus exhibits excellent surface
properties.
Specifically, made of small thin wood pieces 1, 1,. . . with a thickness t of
0.35 mm or less,
the wooden board As has a root mean square height Sq ranging from about 0.005
gm to
about 0.015 gm on the surface. Made of small thin wood pieces 1, 1,. . . with
a thickness t
of 0.25 mm or less (preferably 0.20 mm or less), the wooden board As has a
root mean
28
CA 03216124 2023- 10- 19
square height Sq ranging from about 0.005 gm to about 0.008 gm on the surface.
With a
surface roughness as low as an MDF with excellent surface properties, the
wooden board
As has more excellent surface properties and is preferable.
[0077]
The arithmetic mean height Sa represents the mean of the absolute values of
the
differences in height between various points and the mean plane of the
surface. With a
decreasing arithmetic mean height Sa, the surface of the wooden board As has
less
significant unevenness and thus exhibits excellent surface properties.
Specifically, made of
small thin wood pieces 1, 1, . . . with a thickness t of 0.35 mm or less, the
wooden board As
has an arithmetic mean height Sa ranging from about 0.002 gm to about 0.007 gm
on the
surface. Made of small thin wood pieces 1, 1, . . . with a thickness t of 0.25
mm or less
(preferably 0.20 mm or less), the wooden board As has an arithmetic mean
height Sa ranging
from about 0.002 gm to about 0.005 gm on the surface. With a surface roughness
as low as
an MDF with excellent surface properties, the wooden board As exhibits more
excellent
surface properties and is thus preferable.
[0078]
The surface properties of the wooden board As are not necessarily specified by
the
root mean square height Sq and the arithmetic mean height Sa, but may be
specified by the
skewness Ssk, the maximum valley depth Sv, the maximum height Sz which is the
sum of
the maximum peak height Sp and the maximum valley depth Sv, or the kurtosis
Sku, for
example.
[0079]
The wooden board As according to the embodiment described above can provide
the following advantages.
29
CA 03216124 2023- 10- 19
[0080]
The wooden board As is a single layer obtained by laminating, adhering, and
integrating a large number of small thin wood pieces 1, 1,. . . in an
aggregated state.
[0081]
The single-layer wooden board As may include only one type, namely, the first
small thin wood pieces 1, 1, . . . . For the first small thin wood pieces 1,
1, . . . , at least two
of the following are specified within narrow ranges: the thickness t; the
aspect ratio (dl/d2)
defined by (a mean first length d1)/(a mean second length d2) which is a ratio
between the
mean of the first length dl in the first direction (i.e., along the fibers)
and the mean of the
second length d2 in the second direction (i.e., orthogonal to the fibers); or
the area of the top
and bottom surfaces. Specifically, with a significantly thin thickness t
within the narrow
range from 0.05 mm to 0.35 mm, the large number of the first small thin wood
pieces 1,
1, . . . are uniform in thickness t with little variation. In addition, since
the aspect ratio
(dl/d2) of the first small thin wood pieces falls within a certain range, the
first small thin
wood pieces 1, 1, . . . uniform in size within a certain range are aggregated
into a
homogeneous wooden board As. Moreover, including the top and bottom surfaces
with an
area within the narrow range of 6 cm2 or less, the large number of first small
thin wood
pieces 1, 1, . . . are uniform in area (size) with little variation.
Accordingly, the wooden
board As not only has a higher strength but is less warped by moisture
absorption and
desorption, and thus exhibits dimensional stability as excellent as tropical
plywood. In
addition, since the large number of first small thin wood pieces 1, 1,. . .
are uniform in size,
the wooden board As has no significant unevenness on the surfaces unlike
typical OSBs and
thus exhibits excellent surface properties. Since the large number of first
small thin wood
pieces 1, 1, . . . uniform in shape are aggregated and laminated, the wooden
board As is
CA 03216124 2023- 10- 19
produced easily.
[0082]
In particular, made of the first small thin wood pieces 1, 1,. . . with a mean
thickness
t ranging from 0.15 mm to 0.25 mm and in an elongated shape with an aspect
ratio (dl/d2)
ranging from 4 to 40, the wooden board As has further improved dimensional
stability and
surface properties.
[0083]
On the other hand, the single-layer wooden board As may include only one type,
namely, the second small thin wood pieces 1, 1, . . . . For the second small
thin wood pieces
1, 1,. . . , the bulk density and the area of the top and bottom surfaces are
specified within
narrow ranges. Specifically, with a bulk density within the narrow range from
10 kg/m3 to
150 kg/m3, the large number of the second small thin wood pieces 1, 1,. . .
are uniform in
thickness t with little variation and in first and second lengths dl and d2
within certain
ranges. Accordingly, the second small thin wood pieces 1, 1,. . . uniform in
thickness and
size (area of the top and bottom surfaces) within the certain range of 6 cm2
or less are
aggregated into a homogeneous wooden board As. Accordingly, the wooden board
As not
only has a higher strength but is less warped by moisture absorption and
desorption, and
thus exhibits dimensional stability as excellent as tropical plywood. In
addition, since the
large number of second small thin wood pieces 1, 1,. . . are uniform in
thickness and area,
the wooden board As has no significant unevenness on the surfaces unlike
typical OSBs and
thus exhibits excellent surface properties. Since the large number of second
small thin wood
pieces 1, 1,. . . uniform in thickness and size are aggregated and laminated,
and the wooden
board As is produced easily.
31
CA 03216124 2023- 10- 19
[0084]
In particular, assume that the large number of second small thin wood pieces
1,
1,. . . are significantly thin with a mean thickness t ranging from 0.05 mm to
0.35 mm and
have a bulk density ranging from 20 kg/m3 to 90 kg/m3. In this case, the large
number of
second small thin wood pieces 1, 1, . . . are uniform in thickness t and area,
which further
improves the dimensional stability and surface properties of the wooden board
As.
[0085]
FIG. 6 illustrates the characteristics of the wooden board As according to the
present invention in comparison with boards made of other materials. The
wooden board As
is as large as lauan plywood in the Young's modulus of bending, the rate of
change in the
length at the time of moisture absorption and desorption, and the smoothness.
The wooden
board As is superior to lauan plywood in the anisotropy as the dimensional
stability; and the
color tone and the color uniformity as the surface properties. As compared to
an OSB, the
wooden board As has a uniform Young's modulus of bending in the longitudinal
and
transverse directions, and is excellent in the anisotropy as the dimensional
stability; and the
smoothness, the color tone, and the color uniformity as the surface
properties. That is, the
wooden board As has a high strength and excellent dimensional stability and
surface
properties.
[0086]
[Second Embodiment]
<Wooden Board (Laminated Wooden Board)>
FIG. 7 shows a wooden board Am according to a second embodiment of the present
invention. The wooden board Am according to this embodiment is obtained by
laminating
and integrating wooden layers on the top and bottom surfaces of the wooden
board As
32
CA 03216124 2023- 10- 19
according to the first embodiment, and can also be referred to as a "laminated
wooden board."
The wooden board Am will also referred to as a "laminated wooden board Am."
Note that
the configuration of the wooden board As other than the wooden layers forming
the
laminated wooden board Am is the same as in the first embodiment, and the
detailed
description thereof is omitted here. The same reference characters are used to
represent the
same components as in the first embodiment, and the description thereof will
be omitted.
[0087]
The laminated wooden board Am has a density ranging from 500 kg/m3 to 800
kg/m3 and a thickness ranging from 3 mm to 12 mm, for example. A laminated
wooden
board Am with a small thicknesses ranging from 3 mm to 6 mm are used as, for
example,
an inner wall material for a cargo bed of a vehicle, such as a truck, a base
material for an
indoor cushioned floor, a decorative surface material, and an interior
material, such as an
interior building material (e.g., a riser). A laminated wooden board Am with a
medium
thickness ranging from 6 mm to 12 mm is used as the base material of an indoor
soundproof
floor or a floor for walking with shoes on, or an entrance finishing material,
for example. In
this manner, the laminated wooden board Am is used as a substitute for the
existing plywood
for a base plate. With the same level of surface properties as an MDF, the
laminated wooden
board Am is used advantageously as a decorative thin plywood.
[0088]
The laminated wooden board Am includes a first wooden layer B and two wooden
layers (hereinafter also referred to as the "second wooden layers") C and C.
The laminated
wooden board Am is obtained by laminating and integrating the second wooden
layers C
and C on both the surfaces of the first wooden layer B. In other words, the
first wooden
layer B is interposed between the two second wooden layers C and C. That is,
the first
33
CA 03216124 2023- 10- 19
wooden layer B serves as the core layer of the laminated wooden board Am,
while the two
second wooden layers C and C serve as the top and bottom layers of the
laminated wooden
board Am.
[0089]
The second wooden layers C have each a thickness preferably accounting for 5%
to 40%, more preferably accounting for 8% to 30%, and still more preferably
accounting
for 10% to 25% of the total thickness of the laminated wooden board Am. That
is, the
thickness ratio of the second, first, and second wooden layers C, B, and C to
the laminated
wooden board Am preferably ranges from 5:90:5 to 40:20:40, more preferably
ranges from
8:84:8 to 30:40:30, and still more preferably ranges from 10:80:10 to
25:50:25. With the
ratio of the thicknesses of the first and second wooden layers B and C varied
as appropriate,
the wooden laminated board Am is obtained which exhibits both the strength
required
depending on the purpose and the excellent surface properties.
[0090]
(First Wooden Layer)
As described above, the first wooden layer B is the wooden board As according
to
the first embodiment. That is, the configuration of the wooden board As
described above is
all applied to the first wooden layer B.
[0091]
(Second Wooden Layer)
As shown in an enlarged view of FIG. 8, each second wooden layer C is obtained
by laminating, adhering, and integrating, in an aggregated state, a large
number of tiny thin
wood pieces 2, 2, . . . with top and bottom surfaces extending along the
fibers. The large
number of tiny thin wood pieces 2, 2,. . . have one type of thickness.
34
CA 03216124 2023- 10- 19
[0092]
The tiny thin wood pieces 2 are thin pieces smaller in size (i.e., area of the
top and
bottom surfaces) than the small thin wood pieces 1. The tiny thin wood pieces
2 will be
described in detail. As shown in an enlarged view of FIG. 9, the tiny thin
wood pieces 2
have a thickness t preferably ranging from 0.05 mm to 0.35 mm, more preferably
ranging
from 0.10 mm to 0.30 mm, still more preferably from 0.15 mm to 0.25 mm, and
further
more preferably ranging from 0.15 mm to 0.20 mm. That is, the thickness t of
the tiny thin
wood pieces 2 is equivalent to (within the same thickness range as) the
thickness t of the
small thin wood pieces 1. Accordingly, these tiny thin wood pieces 2, 2, . . .
with the small
thickness t determine the characteristics of the second wooden layers C, that
is, the
characteristics of the laminated wooden board Am. The thickness t of the tiny
thin wood
pieces 2 is expressed in mean.
[0093]
The tiny thin wood pieces 2 have an aspect ratio (dl/d2), which is defined
like for
the small thin wood pieces 1, ranging from 1 to 500 in one preferred
embodiment. That is,
the tiny thin wood pieces 2 may be in a square shape or an elongated shape
(i.e., a strip
shape). The tiny thin wood pieces 2 in an elongated shape has a first length
dl which is the
longitudinal size (i.e., length) like in the small thin wood pieces 1. The
tiny thin wood pieces
2 include fibers 2a, 2a, . . . such as vessels or tracheids, for example, and
the first length dl
is the length along the fibers 2a. The second length d2 is the transverse size
(i.e., width), for
example, the size in the direction orthogonal to the fibers. The aspect ratio
preferably ranges
from 2 to 100, more preferably ranges from 3 to 12.5, and still more
preferably ranges from
to 10.
CA 03216124 2023- 10- 19
[0094]
The area of the top and bottom surfaces of the tiny thin wood pieces 2 is not
particularly limited as long as being smaller than that of the small thin wood
pieces 1. The
area is preferably 5 cm2 or less, more preferably 2 cm2 or less, still more
preferably 1 cm2
or less, and further more preferably 0.5 cm2 or less.
[0095]
The tiny thin wood pieces 2 have a bulk density preferably ranging from 10
kg/m3
to 150 kg/m3, more preferably ranging from 10 kg/m3 to 100 kg/m3, still more
preferably
ranging from 20 kg/m3 to 95 kg/m3, and further more preferably ranging from 30
kg/m3 to
90 kg/m3.
[0096]
The tree species used for the tiny thin wood pieces 2, 2, . . . is not
particularly
limited. The tree species which is the same or different from that of the
small thin wood
pieces 1, 1, . . . may be employed. That is, the tree species of the tiny thin
wood pieces 2,
2,. . . may be the same as or different from that of the small thin wood
pieces 1, 1, . . . . In
order to easily produce the tiny thin wood pieces 2, 2,. . . using the small
thin wood pieces
1, 1, . . . , the tree species of the tiny thin wood pieces 2, 2, . . . is the
same as that of the
small thin wood pieces 1, 1, . . . . in one preferred embodiment.
[0097]
As the physical properties, the density of the tiny thin wood pieces 2 is
preferably
250 kg/m3 or more, and more preferably 300 kg/m3 or more. Further, the density
is
preferably 800 kg/m3 or less, more preferably 500 kg/m3 or less, and still
more preferably
400 kg/m3 or less. A density less than 250 kg/m3 requires a thicker sheet to
form the
laminated wooden board Am with the same levels of density and strength and a
higher
36
CA 03216124 2023- 10- 19
pressure for hot-pressing in the press forming step.
[0098]
The tiny thin wood pieces 2 may have a density exceeding 800 kg/m3, which are
however not easily available. That is, the upper limit of the density is not
necessarily 800
kg/m3 and may be higher, if tiny thin wood pieces 2 with a density exceeding
800 kg/m3 are
easily available.
[0099]
The tiny thin wood pieces 2 have a water content preferably ranging from about
2% to about 20%, and more preferably ranging from 2% to 8%.
[0100]
In each wooden layer C, (the length of) the fibers 2a, 2a,. . . of the large
number of
tiny thin wood pieces 2, 2, . . . may be oriented in a reference direction but
not necessarily
have such an orientation but may lie randomly. Some of the tiny thin wood
pieces 2, 2,. . .
may include fibers inclined at a certain angle (e.g., about 20 ) from the
reference direction.
[0101]
<Method of Producing Wooden Board (Laminated Wooden Board)>
Next, methods of producing the small thin wood pieces 1, 1,. . . and tiny thin
wood
pieces 2, 2,. . . and producing the laminated wooden board Am from these thin
wood pieces
1 and 2 will be described with reference to FIG. 10. The method of producing
small thin
wood pieces 1, 1, . . . includes a step 131 of producing thin wood pieces and
a step P2 of
producing small thin wood pieces. The method of producing the tiny thin wood
pieces 2,
2, . . . further includes a subsequent step P6 of producing tiny thin wood
pieces. The method
of producing the laminated wooden board Am further includes subsequent steps,
namely, a
step P3 of applying an adhesive, a step P4 of forming a sheet, and a step P5
of hot-pressing.
37
CA 03216124 2023- 10- 19
[0102]
(Step P1 of Producing Thin Wood Pieces)
The step P1 of producing thin wood pieces is the same as in the first
embodiment,
and detailed description thereof will thus be omitted here. In the subsequent
steps, the
thickness t of the small thin wood pieces 1 and the tiny thin wood pieces 2
does not change
basically from the thickness of the cut thin wood pieces. The thickness of the
cut thin wood
pieces remains as the thickness t of the small thin wood pieces 1 and the tiny
thin wood
pieces 2.
[0103]
(Step P2 of Producing Small Thin Wood Pieces)
The step P2 of producing small thin wood pieces is the same as in the first
embodiment, and detailed description thereof will thus be omitted here.
[0104]
(Step P6 of Producing Tiny Thin Wood Pieces)
In the step P2 of producing small thin wood pieces, the small thin wood pieces
1,
1, . . . are formed and small thin wood pieces 3, 3, . . . (not shown) are
removed in the
classification step of the small thin wood pieces 1, 1, . . . . From these
small thin wood pieces,
tiny thin wood pieces 2, 2, . . . smaller than the small thin wood pieces 1,
1, . . . can be
obtained. Note that the "small thin wood pieces 3, 3, . . . removed in the
classification step"
are the small thin wood pieces other than the small thin wood pieces 1 formed
in the step
P2 of producing small thin wood pieces. The small thin wood pieces 3, 3,. . .
are in a size
(at least one of the thickness t or the aspect ratio, or at least one of the
thickness t, the first
length dl, or the second length (i.e., width) d2) out of the range.
38
CA 03216124 2023- 10- 19
[0105]
Specifically, the small thin wood pieces 1, 1,. . . and/or the small thin wood
pieces
3, 3,. . . are further crushed by the same method as in the step P2 of
producing small thin
wood pieces. Accordingly, the small thin wood pieces 1, 1, . . . and/or 3, 3,
. . . are crushed
along the width so as to be split along the fibers (i.e., along the first
length) into the tiny thin
wood pieces 2, 2,. . . which are more elongated than the elongated small thin
wood pieces
1, 1, . . . . That is, the tiny thin wood pieces 2 are thin pieces smaller in
the second length
(i.e., the width) d2 than the small thin wood pieces 1. In the additional
crushing step in the
production step P6, the small thin wood pieces 1, 1, . . . and/or 3, 3, . . .
are also crushed
along the first length. That is, the tiny thin wood pieces 2 are thin pieces
smaller not only in
the second length (i.e., the width) d2 but also in the first length dl than
the small thin wood
pieces 1.
[0106]
As an alternative, the small thin wood pieces 3, 3,. . . may be sorted using a
mesh
of 02, for example, and those passing through the mesh may serve as the tiny
thin wood
pieces 2, 2. . . .
[0107]
In this manner, the small thin wood pieces 1, 1,. . . formed and the small
thin wood
pieces 3, 3, . . . removed in the step P2 of producing small thin wood pieces
are used and
further subjected to the step of crushing or classification. Accordingly, the
tiny thin wood
pieces 2, 2, . . . can be easily produced which are smaller in the first
length dl and/or the
second length d2 than the small thin wood pieces 1, 1, . . . .
[0108]
The process may include causing the tiny thin wood pieces 2, 2,. . . obtained
in the
39
CA 03216124 2023- 10- 19
additional crushing step to pass through a sieve (e.g., with a mesh of 02) or
any other
suitable tool and sorting (classifying) the size of the tiny thin wood pieces
2, 2, . . . .
Accordingly, the large number of tiny thin wood pieces 2, 2,. . . become fine
and uniform
in size and shape. From the foregoing, the tiny thin wood pieces 2, 2,. . .
are produced.
[0109]
(Step P3 of Applying Adhesive)
The large number of small thin wood pieces 1, 1,. . . and tiny thin wood
pieces 2,
2,. . . , which are fine and uniform in size and shape, are obtained by the
sorting in the step
P2 of producing small thin wood pieces and the step P6 of producing tiny thin
wood pieces.
The step P3 of applying an adhesive is then performed. These small thin wood
pieces 1,
1, . . . and tiny thin wood pieces 2, 2, . . . are transferred into adhesive
application equipment
and applied with an adhesive. The adhesive may be an isocyanate-based
adhesive, for
example. Besides, for example, a phenolic resin, an amine-based adhesive, such
as a urea
resin or a melamine resin, or a natural product-based adhesive may be used. In
combination
with the adhesive, a generally used water repellent may be used.
[0110]
(Step P4 of Forming Sheet)
Next, as shown on the left of FIG. 11, first, the large number of tiny thin
wood
pieces 2, 2, . . . applied with the adhesive are laminated (stacked) to a
predetermined
thickness (i.e., height) in an aggregated state along the thickness with or
without being
oriented along the fibers to form a sheet Cl (i.e., a second aggregate) made
only of the tiny
thin wood pieces 2, 2, . . . . Next, the large number of small thin wood
pieces 1, 1,. . . applied
with the adhesive are laminated to a predetermined height in an aggregated
state along the
thickness with or without being oriented along the fibers to form a sheet B1
(i.e., a first
CA 03216124 2023- 10- 19
aggregate) made only of the small thin wood pieces 1, 1, . . . . Finally, the
sheet Cl made
only of the tiny thin wood pieces 2, 2, . . . is formed on the resultant sheet
B as described
above. In this manner, the sheets Cl, Bl, and Cl are sequentially laminated
into a laminated
sheet Al with the triple-layer structure.
[0111]
At this time, the thicknesses of the sheets B1 and Cl are adjusted to obtain
desired
thickness ratios of the first and second wooden layers B and C to the total
thickness of the
laminated wooden board Am. For example, assume that a laminated board Am is
formed
which has a thickness of 4 mm and includes second wooden layers C each having
a thickness
accounting for 15% of the total thickness of the laminated wooden board Am
(i.e., the
thickness ratio of the second, first, and second wooden layers C, B, and C,
are 15:70:15). In
this case, first, tiny thin wood pieces 2, 2, . . . with a thickness t of 0.2
mm are stacked so
that the resultant sheet Cl has a thickness (i.e., height) of about 5 mm.
Then, small thin
wood pieces 1, 1, . . . with a thickness t of 0.2 mm are stacked on the sheet
Cl so that the
resultant sheet B1 has a thickness of about 24 mm. Finally, tiny thin wood
pieces 2, 2, . . .
are stacked on the sheet B1 so that the resultant sheet Cl has a thickness of
about 5 mm.
Accordingly, the laminated sheet Al with the triple-layer structure of the
sheets Bl, Cl and
Al has a thickness (i.e., height) of about 34 mm.
[0112]
(Step P5 of Hot-Pressing)
This laminated sheet Al is first pressed and slightly compacted as in the case
of a
typical wooden board and then transferred into a hot press machine and set
between hot
plates. The hot press machine performs hot-pressing on the laminated sheet Al
at
predetermined pressure and temperature to compress and integrally form the
laminated sheet
41
CA 03216124 2023- 10- 19
Al by curing the adhesive. Accordingly, the laminated wooden board Am shown in
FIG. 7
is formed.
[0113]
At this time, as shown in FIG. 11, the illustrated sheet Al with a thickness
of about
40 mm is compressed into the laminated wooden board Am with a thickness of 4
mm, for
example, that is, a one-tenth thickness. The pressing temperature for the hot-
pressing is not
particularly limited but may range from 100 C to 180 C, for example. The
pressing pressure
in the hot-pressing ranges from 2 Nimm2 to 4 Nimm2, for example. The pressing
period is
one to two minutes, for example. The pressing period depends on the thickness
of the
laminated wooden board Am and may be shorter than one minute or longer than
two minutes.
A preheating using a heating machine may be performed before the hot-pressing
using the
hot press machine.
[0114]
The small thin wood pieces 1, 1, . . . and the tiny thin wood pieces 2, 2, . .
. in a
smaller size have their knots removed and are kept in a fine size without
variation and the
resultant sheets B1 and Cl are thus homogeneous. That is, the whole laminated
sheet Al is
thus homogeneous, which causes less variation in the strength of the laminated
wooden
board Am. That is, a strand board made of large strands (i.e., flakes) has,
due to a non-
uniform sheet including knots, for example, thin, low-strength portions (or
spots), causing
variation in the strength. The laminated wooden board Am is however free from
the problem.
In addition, the sheet B1 made of thinner small thin wood pieces 1, 1, . . .
has a higher
homogeneity, and the resultant laminated wooden board Am thus tends to exhibit
a higher
strength. In general, a strand board made of large strands (i.e., flakes) can
exhibit a higher
strength. In the present invention, the laminated wooden board Am has both
homogeneity
42
CA 03216124 2023- 10- 19
and strength with the small thin wood pieces 1 obtained by further
miniaturizing the thin
wood pieces (i.e., cut thin wood pieces), which are thinner and smaller than
the flakes, by
crushing.
[0115]
The small thin wood pieces 1, 1, . . . are small and uniform in size with gaps
left
evenly in the sheet Bl. Similarly, the tiny thin wood pieces 2, 2, . . . are
smaller and more
uniform in size than the small thin wood pieces 1, 1,. . . with gaps left
evenly in the sheet
Cl. Even if the small thin wood pieces 1, 1,. . . in the sheet B1 and the tiny
thin wood pieces
2, 2, . . . in the sheet Cl are hot-pressed, while containing a relatively
large amount of
moisture, vapor generated by evaporation of the moisture is smoothly released
from the
sheets B1 and Cl. That is, as shown on the left of FIG. 11, the sheet B1
includes a large
number of small voids between the adjacent small thin wood pieces 1, 1, . . .
. Similarly, the
sheet Cl also includes a large number of small voids between the adjacent tiny
thin wood
pieces 2, 2, . . . . These voids communicate with each other not only along
the fibers and
orthogonally to the fibers of the small thin wood pieces 1, 1, . . . and tiny
thin wood pieces
2, 2,. . . but also along the thickness. In addition, these voids are
continuous not only in the
sheets B1 and in the sheets Cl but also between the sheets B1 and Cl, and are
continuous
three-dimensionally throughout the laminated sheet Al. This configuration
causes less
puncture at the stop of applying pressure onto the laminated wooden board Am.
[0116]
Through these steps, the laminated wooden board Am is formed which includes
the
first and second wooden layers B and C with (i.e., which has, as a whole,) a
density ranging
from 500 kg/m3 to 800 kg/m3 and a Young's modulus of bending ranging from 3.5
GPa to
5.0 GPa.
43
CA 03216124 2023- 10- 19
[0117]
The densities of the first wooden layers B and C may be substantially the same
or
different. The densities of the wooden layers B and C are different from each
other in one
preferred embodiment to reduce the puncture during the formation. If the
densities of the
first and second wooden layers B and C are different, the difference is 400
kg/m3 or more,
for example. The magnitude relationship between the densities of the first and
second
wooden layers B and C is not particularly limited. The density of the first
wooden layer B
may be higher or lower than that of the second wooden layers C. In order to
improve the
smoothness, color tone, and color uniformity as the surface properties of the
laminated
wooden board Am, the second wooden layers C is a high-density wooden layer
with a higher
density than the first wooden layer B in one preferred embodiment.
[0118]
As shown on the right of FIG. 11, this wooden board As includes (retains) a
large
number of three-dimensionally continuous small voids inside the first and
second wooden
layers B and C. Accordingly, the laminated wooden board Am also has an
excellent air
permeability.
[0119]
(Other Steps)
The method of producing the laminated wooden board Am may further include, as
another step, a finish step after the step P5 of hot-pressing. In the finish
step, the laminated
wooden board Am is cured to an equilibrium water content and then the second
wooden
layers C as the top and bottom surfaces are ground by a sander to adjust the
final thicknesses
of the laminated wooden board Am. The sander may be a generally used one and
is #150,
for example. Through this finish step, the laminated wooden board Am with more
excellent
44
CA 03216124 2023- 10- 19
surface properties can be obtained.
[0120]
The laminated wooden board Am according to this embodiment can provide the
following advantages.
[0121]
The laminated wooden board Am includes two types of the small thin wood pieces
1 and tiny thin wood pieces 2 with thicknesses within the same range and in
different sizes.
Specifically, the laminated wooden board Am includes: the first wooden layer B
and the two
second wooden layers C. The first wooden layer B is a single layer obtained by
laminating,
adhering, and integrating a large number of small thin wood pieces 1, 1,. . .
in an aggregated
state. The second wooden layers C are each a single layer obtained by
laminating, adhering,
and integrating a large number of tiny thin wood pieces 2, 2, . . . with a
smaller area than
the small thin wood pieces 1, 1, . . . in an aggregated state. The laminated
wooden board Am
is a triple layer obtained by laminating and integrating the second wooden
layers C and C
on both the surfaces of the first wooden layer B.
[0122]
That is, the first wooden layer B serving as the core layer of the laminated
wooden
board Am has the same configuration as the wooden board As. Accordingly, the
first wooden
layer B (i.e., the laminated wooden board Am) not only has a higher strength
but is less
warped by moisture absorption and desorption, and thus exhibit dimensional
stability as
excellent as tropical plywood. In addition, the large number of tiny thin wood
pieces 2, 2, . . .
which are smaller in the area (specifically, at least one of the first length
dl or the second
length (i.e., the width) d2) than the first small thin wood pieces 1, 1, . . .
are more uniform
in size. Thus, the second wooden layers C and C serving as the top and bottom
surfaces of
CA 03216124 2023- 10- 19
the laminated wooden board Am have no significant unevenness on the surfaces
unlike
typical OSBs and thus exhibit more excellent surface properties that are as
excellent as
MDFs. The sheets B1 and Cl, which are the aggregates of the large number of
small thin
wood pieces 1, 1,. . . and the tiny thin wood pieces 2, 2,. . . ,
respectively, and uniform in
size are sequentially laminated and integrated in the order of the sheets Cl,
Bl, and Cl.
Accordingly, the laminated wooden board Am is thus produced easily.
[0123]
In particular, made of the first small thin wood pieces 1, 1,. . . with a mean
thickness
t ranging from 0.15 mm to 0.25 mm and in an elongated shape with an aspect
ratio (dl/d2)
ranging from 4 to 40, the first wooden layer B serving as the core layer of
the laminated
wooden board Am has improved dimensional stability. As a result, the
dimensional stability
of the laminated wooden board Am improves. Since the smoothness of the
surfaces of the
first wooden layer B improves, the smoothness, color tone, and color
uniformity of the
surfaces of the second wooden layers C and C laminated on the first wooden
layer B also
improve. As a result, the laminated wooden board Am with more excellent
surface properties
can be obtained.
[0124]
Assume that the second wooden layers C serving as the top and bottom layers of
the laminated wooden board Am are made of the tiny thin wood pieces 2, 2,. . .
with a mean
thickness ranging from 0.15 mm to 0.25 mm and in an elongated shape with an
aspect ratio
(dl/d2) ranging from 5 to 10. The second wooden layers C then exhibit, that
is, the resultant
laminated wooden board Am exhibits further improved surface properties.
[0125]
In particular, assume that the first wooden layer B serving as the core layer
of the
46
CA 03216124 2023- 10- 19
laminated wooden board Am is made of second small thin wood pieces 1, 1,. . .
with a mean
thickness t ranging from 0.05 mm to 0.35 mm and a bulk density ranging from 20
kg/m3 to
90 kg/m3. The first wooden layer B then exhibits improved dimensional
stability. As a result,
the dimensional stability of the laminated wooden board Am improves. Since the
smoothness of the surfaces of the first wooden layer B improves, the
smoothness, color tone,
and color uniformity of the surfaces of the second wooden layers C and C
laminated on the
first wooden layer B also improve. As a result, the laminated wooden board Am
with more
excellent surface properties can be obtained.
[0126]
Assume that the second wooden layers C serving as the top and bottom layers of
the laminated wooden board Am are made of tiny thin wood pieces 2, 2, . . .
with a mean
thickness t ranging from 0.05 mm to 0.35 mm and a bulk density ranging from 10
kg/m3 to
150 kg/m3. The second wooden layers C then exhibit, that is, the resultant
laminated wooden
board Am exhibits further improved surface properties.
[0127]
Made of the second wooden layers C with a thickness preferably accounting for
5% to 40% of the total thickness of the laminated wooden board Am, the
laminated wooden
board Am can exhibit both a high strength and excellent surface properties.
[0128]
FIG. 12 illustrates the characteristics of the laminated wooden board Am
according
to the present invention in comparison with boards made of other materials.
The laminated
wooden board Am is as large as lauan plywood in the Young's modulus of
bending, the rate
of change in the length at the time of moisture absorption and desorption. The
laminated
wooden board Am is superior to lauan plywood in the anisotropy as the
dimensional
47
CA 03216124 2023- 10- 19
stability; and the smoothness, the color tone and the color uniformity as the
surface
properties. As compared to an OSB, the laminated wooden board Am has a uniform
Young's
modulus of bending in the longitudinal and transverse directions, and is
excellent in the
anisotropy as the dimensional stability; and the smoothness, the color tone,
and the color
uniformity as the surface properties. That is, the laminated wooden board Am
has a high
strength and excellent dimensional stability and surface properties. It can be
said that the
laminated wooden board Am is a wooden board not only has the characteristics
described
above but also is specialized in the surface properties, as compared to a
single-layer wooden
board (in other words, the first wooden layer B) made only of the small thin
wood pieces 1,
1, . . . .
[0129]
<Other Embodiments>
In the embodiments described above, the wooden board As (i.e., the first
wooden
layer (core layer) B in the second embodiment) is made of the small thin wood
pieces 1
obtained by crushing thin wood pieces (i.e., cut thin wood pieces) as cut from
raw timber
into smaller sizes. Alternatively, the wooden board As may be made of thin
wood pieces
(i.e., cut thin wood pieces) as cut from raw timber.
[0130]
In the embodiment described above, the step P1 of producing thin wood pieces
and
the step P2 of producing small thin wood pieces each includes the
classification step.
Alternatively, in the present invention, only one of the steps P1 and P2 may
include the
classification step, or none of the steps P1 and P2 may include the
classification step. In
order not only to increase the strength and but also to further improve the
dimensional
stability and the surface properties of the wooden board As, the step P1 or P2
includes the
48
CA 03216124 2023- 10- 19
classification step in one preferred embodiment, the step P2 includes the
classification step
in one more preferred embodiment, and both the steps P1 and P2 include the
classification
step in one further more preferred embodiment.
[Examples]
[0131]
Now, the present disclosure will be described based on examples. Note that the
present disclosure is not limited to the following examples. Modifications and
change may
be made to the following examples based on the spirit of the present
disclosure and should
not be excluded from the scope of the present disclosure.
[0132]
(Example 1)
The bulk densities of the small thin wood pieces (i.e., the second small thin
wood
pieces) produced in the step of producing small thin wood pieces described
above were
measured. Specifically, the small thin wood pieces were piled up without gaps
in a
measurement container with a volume of 10 L. The tops of the piled small thin
wood pieces
were cut by rubbing and flattened to be flush with each other using a spatula
or any other
suitable tool without applying any pressure. In this state, the mass was
measured. The bulk
densities were obtained from the equation (1), where the "mass of small thin
wood pieces"
was the value obtained by subtracting the mass of the measurement container
from the mass
and the "volume of small thin wood pieces" was the volume (0.01 m3) of the
measurement
container. Several types of small thin wood pieces were prepared in different
sizes, each had
a mean thickness ranging from 0.05 mm to 0.5 mm and included top and bottom
surfaces
with an area of 64 cm2 or less (0.5 cm2 or more). The bulk density of the
small thin wood
pieces in each size was then measured. As a result, it was found that the
small thin wood
49
CA 03216124 2023- 10- 19
pieces each had a bulk density ranging from 10 kg/m3 to 100 kg/m3 (i.e., 10
kg/m3 to 150
kg/m3). It was found that the small thin wood pieces with a mean thickness
ranging from
0.05 mm to 0.35 mm have a bulk density ranging from 20 kg/m3 to 90 kg/m3.
[0133]
(Comparative Example 1)
Like in Example 1, the bulk densities of flakes (corresponding to strands
usually
used as a constituent material of an OSB) were measured, which were used as a
raw material
in the step of producing thin wood pieces. Several types of flakes were
prepared in different
sizes, each had a mean thickness ranging from 0.06 mm to 1.5 mm and included
top and
bottom surfaces with an area of 36 cm2 or less. The bulk density of the flakes
in each size
was then measured. As a result, it was found that the flakes had each a bulk
density of 200
kg/m3 or more.
[0134]
(Example 2)
Like in Example 1, the bulk densities of the tiny thin wood pieces produced in
the
step of producing tiny thin wood pieces described above were measured. Several
types of
tiny thin wood pieces were prepared in different sizes, each had a mean
thickness ranging
from 0.05 mm to 0.5 mm and included top and bottom surfaces with an area
smaller (e.g., 5
cm2 or less) than the small thin wood pieces used in Example 1. The bulk
density of the tiny
thin wood pieces in each size was then measured. As a result, it was found
that the tiny thin
wood pieces had each a bulk density ranging from 10 kg/m3 to 100 kg/m3 (i.e.,
10 kg/m3 to
150 kg/m3).
CA 03216124 2023- 10- 19
INDUSTRIAL APPLICABILITY
[0135]
The present invention allows easy production of a wooden board, which is made
of
small thin wood pieces uniform in size and has a higher strength and
dimensional stability
and surface properties as excellent as tropical plywood, and is thus
significantly useful and
highly industrially applicable.
DESCRIPTION OF REFERENCE CHARACTERS
[0136]
As Wooden Board
Am Laminated Wooden Board (Wooden Board)
Al Sheet
B First Wooden Layer
B1 Sheet
C Second Wooden Layer
Cl Sheet
P1 Step of Producing Thin Wood Pieces
P2 Step of Producing Small Thin Wood Pieces
P3 Step of Applying Adhesive
P4 Step of Forming Sheet
P5 Step of Hot-Pressing
P6 Step of Producing Tiny Thin Wood Pieces
1 Small Thin Wood Piece
la Fiber
51
CA 03216124 2023- 10- 19
2 Tiny Thin Wood Piece
2a Fiber
t Thickness
dl First Length
d2 Second Length
dl/d2 Aspect Ratio
52
CA 03216124 2023- 10- 19
