Note: Descriptions are shown in the official language in which they were submitted.
CA 02638079 2008-07-17
CONTAINER FLOORING MATERIAL AND METHOD OF MANUFACTURE
Field of the Invention
[0001] The present invention relates to a composite container floorboard
having a
structural strand-based board as the core material and the fabrication method
thereof.
Background of the Invention
[0002] The floorboard of the container is the main structural component and
primarily
dictates the load-bearing area of the container. Container floorboards must
meet high
requirements for mechanical performance, impact resistance, and durability.
Tropical
hardwood species such as Keruing and Apitong have been used to produce multi-
layered
thick plywood as container flooring by virtually the entire container
industry.
Considering that such tree species have a growing cycle as long as fifty years
and even
longer, the market supply for large-diameter Keruing and Apitong timber has
dwindled as
a 1-esult of the over-logging of primeval tropical rainforests.
[0003] The present invention has practical value to the protection of the
worlds' ecology,
the reduction in the consumption of tropical hardwood resources, the
development of new
types of floorboards for containers, and the widening of the sources of
materials for
container floorboard.
[0004] A primary object of the present invention is to provide a composite
container
floorboard having a structural strand-based board as the core material and the
fabrication
=
method thereof In general, a suitable container floorboard must achieve a
minimum of
12 to15 years of service life and must be capable of withstanding repeated
high horizontal
shear loads applied through forklift truck wheels or other loading equipment,
as expected
CA 02638079 2008-07-17
and experienced in its normal operational environment. The wood species must
match or
exceed the performance of traditional apitong/keruing panels. Generally,
suppliers are
required to provide evidence of satisfactory performance for all plywood
panels.
[0005] In part, the ability to withstand repeated high horizontal shear loads
mandates a
minimum thickness of about 28 mm, with a density of about 700 kgs - 880
kgs/cubic
meter.
[0006] Suitable container floorboards should demonstrate performance
characteristics
such as a short span test with loads greater than 1525 lbs. This is a three
point bending
test for estimating shear strength of the panels. The floorboards should also
pass a
floorboard strength test using a forklift vehicle. This test requires a test
vehicle loaded
with an axle load of 3630 kg per wheel (2 wheel load 7260 kg) to manoeuvre
slowly over
the board. Failure includes delaminating ply separation or cracks in the
veneers.
Summary of the Invention
[0007] The present invention relates to a novel wood composite material
suitable for use
as container flooring. Rather than using completely high-density tropical
hardwood
species, the present invention utilizes fast growing bamboo species as well as
fast-
growing low-density wood species and tropical hardwood species veneers.
[0008] The present invention provides a method of using structural strand-
based boards,
which can be made of small-diameter logs, brushwood, timber harvesting and
processing
residuals, with high strength and modulus of elasticity (MOE), proper
proportion between
their longitudinal and traverse strength and MOE complied with certain
requirements,
and high shear resistance. Such structural strand-based boards are then
applied as core
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materials in the floorboards of containers whilst materials such as wooden
veneers,
bamboo curtains, bamboo-woven mats and resin-impregnated paper are applied
alone or
compositely as surface overlay materials of the floorboard.
[0009] Therefore, in one aspect, the invention comprises a composite container
floorboard having a structural strand-based board as core material, wherein a
structural
strand-based board being used as a core board comprises two to four layers of
wooden
veneers coated or impregnated with phenol-formaldehyde resin (or coated or
impregnated
with other weather-resistant resin) on a top and a bottom, respectively, of
surface overlay
materials; or comprises one piece of impregnated paper, one phenol-
formaldehyde resin-
impregnated (or other weather-resistant resin-impregnated) bamboo-woven mat,
and one
to three pieces of wooden veneers coated or impregnated with phenol-
formaldehyde resin
(or other weather-resistant resin) on double sides (or partially or entirely
replacing
wooden veneers with bamboo curtains impregnated with phenol-formaldehyde resin
or
other weather-resistant resin) from an exterior to an interior, respectively,
of surface
overlay materials; or comprises one piece of Keruing or Apitong wooden veneer
or other
species of wooden veneer with similar properties, and one to three pieces of
wooden
veneers coated or impregnated with phenol-formaldehyde resin (or other weather-
resistant resin) on double sides (or partially or entirely replacing wooden
veneers with
bamboo curtains or bamboo-woven mats impregnated with phenol-formaldehyde
resin
(or other weather-resistant resin) from an exterior to an interior,
respectively, of surface
overlay materials.
[0010] The method of fabricating a composite container floorboard having a
structural
strand-based board as the core material comprises:
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a, a step of selecting and treating wooden veneers, such that wooden
veneers with
moisture content of 12% or less and are coated or impregnated with phenol-
formaldehyde
resin on double sides of the wooden veneers with a spread of 250-350 g/tn2;
the wooden
veneers are treated through conditioning or low-temperature drying, and bamboo
curtains
and bamboo-woven mats are dried to a moisture content of less than 15% and
impregnated with phenol-formaldehyde resin (or other weather-resistant resin)
and
treated through low-temperature drying, wherein a certain proportion of
insecticide is
added to the phenol-formatdehyde resin;
b. a step of forming a core board, wherein a substrate of the structural
strand-based board is made into a core board of the structural strand-based
board after being configured into a board of constant thickness and being
sanded to the thickness of about 20 mm to about 24 mm; and
c. a step of laying up, wherein materials such as wooden veneers,
bamboo curtains, bamboo-woven mats and resin-impregnated paper are alone
or compositely laid up onto the core board of the structural strand-based
board, before being hot pressed at a temperature ranging from 125 to 150 C
and at maximum pressure of 1.0 -4.0 MPa for five to ten minutes, sequentially
stepping down the press pressure, degassing, and then relieving press
pressure.
100111 The present invention has the advantages of effectively utilizing
various species at
diverse diameters from China and the world. Examples include a great variety
of
softwood, hardwood, and bamboos from natural forests and plantation forests,
These
materials, upon applying alone or compositely and through scientific designs
and logical
combination, may overcome the shortage of worldwide hardwood resources,
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Additionally, the present invention has overcome the technical problem in
connection
with the mass production of new types of container floorboards that comply
with the
requirements of the international container industry. A structural strand-
based board is
made into a middle core layer of the container floorboard after being
configured into a
board of constant thickness and being sanded, whilst four to eight layers of
wooden
veneers, bamboo curtains, bamboo-woven mats and resin-impregnated paper are
alone or
compositely used as surface overlay materials of the core board. Some wooden
veneers
need to be coated (or impregnated) with phenol-formaldehyde resin (or other
weather-
resistant resin) on double sides whilst bamboo curtains and bamboo-woven mats
need to
be impregnated with phenol-formaldehyde resin (or other weather-resistant
resin). Resin-
impregnated paper is made by impregnating wood pulp with phenol-formaldehyde
or
melamine-formaldehyde or a hybrid resin of the above two and treating through
low-
temperature drying. A certain proportion of insecticides should preferably be
added to the
veneer resin, such that the veneer resin may evenly penetrate into the surface
overlay
materials on the floorboard of containers during hot pressing, thus making the
floorboard
long-term insecticidal. The core materials and the surface overlay Materials
are laid up
and configured into the floorboard of containers through resination and hot
pressing, such
that various performance indicators such as their strength, modulus of
elasticity, and
other properties can completely comply with the technicarrequirements of the
international container industry.
Brief Description of the Drawings
[0012] Fig. 1 shows one embodiment of the invention in cross-section. The
floorboard
has a core layer composed of strand-based wood composite. Item (1) is the
surface layer
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of parallel-grained wood veneer layers; Item (2) is the cross-grained wooden
veneer; and
Item (3) is the strand-based wood composite.
[0013] Fig. 2 shows another embodiment of the invention in cross-section. The
floorboard has a core layer composed of strand-based wood composite. Item (4)
is the
surface layer of paper impregnated with resin; Item (5) is the bamboo-woven
mat layer;
Item (6) is the wood veneer in the parallel-grained direction; and Item (3) is
the strand-
based wood composite.
[0014] Fig. 3 shows another embodiment of the invention in cross-section. The
floorboard has a core layer composed of strand-based wood composite. Item (4)
is the
surface layer of paper impregnated with resin; Item (5) is the bamboo-woven
mat layer;
Item (7) is the bamboo curtains layer; and Item (3) is the strand-based wood
composite.
[0015] Fig. 4 shows another embodiment of the invention in cross-section. The
floorboard has a core layer composed of strand-based wood composite. Item (8)
is the
wood veneer layer made from Keruing or Apitong; Item (9) is the wood veneer
layer; and
Item (3) is the strand-based wood composite.
Detailed Description of Preferred Embodiments
[0016] The present invention relates to a composite container floorboard
having a
structural strand-based board as the core material and its fabrication method
thereof.
Given that the structural strand-based board is used as a middle core layer
after
configuring it into a board of constant thickness and having it sanded,
together with 4 to 8
layers of wooden veneers, bamboo curtains, bamboo-woven mats and resin-
impregnated
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paper being applied alone or compositely as surface overlay materials thereof,
the present
invention has the advantages of: (1) increasing the sources of raw materials
for container
floorboard; and (2) producing composite container floorboard with consistent
quality,
strength and stiffness, and other properties and performances to meet the
technical
requirements of the international container industry.
[0017] When describing the present invention, all terms not defined herein
have their
common art-recognized meanings. As used herein, the term "about" refers to a
margin of
plus or minus 10%, or within the tolerance of a suitable measuring device or
instrument.
As used herein, "specific density" refers to density relative to water. All
wood density
refers to the density of oven-dried wood.
[0018] The term "weather proof resin" means a natural or synthetic resin which
has
adhesive and water-repellant properties. Weather proof resins include, without
limitation, formaldehyde resins such as phenol-formaldehyde or melamine-
formaldehyde
resins.
[0019] The present invention relates to a hardwood veneer-wood composite board
suitable for use as a container flooring material. In general terms, the
invention comprises
a multilayer board having a surface composite wooden veneer layer and a wood
core
layer.
[0020] The wood veneer layers comprises of wood veneers in either gain
parallel or
grain perpendicular orientation or in alternating parallel and perpendicular
layers. As
used herein, "grain parallel" refers to wood grain which is parallel to the
longitudinal axis
of the board. "Grain perpendicular" refers to wood grain which is
perpendicular the
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longitudinal axis of the board. The wood veneer layers may be comprised of
Keruing or
Apitong or wood of similar properties such as pine, fir or eucalyptus.
[0021] The bamboo layer comprises bamboo strips sheets made of strips of
bamboo and
a suitable resin. The bamboo strips may be arranged so that the bamboo strips
are all
parallel, or parallel and perpendicular combination, or they may be layered or
woven in a
crisscrossing pattern. The bamboo layer may comprise of bamboo curtains made
from
strips of bamboo held together with string. The bamboo layer may also comprise
a stripe
sheet bamboo-woven mat made of strips of bamboo in a crisscrossing pattern and
a
suitable resin
[0022] The wood core layer comprises of a thick layer of wood strand, which
comprises
wood strand chips similar to those suitable for use in oriented strand boards.
The wood
strand layer may be oriented or non-oriented.
[0023] The wood core layer may preferably be comprised of any suitable low-
density
wood. Low density wood has a specific density of about 0.6 or less. Suitable
wood
species may include poplar, aspen, spruce, fir and pine. Preferably, the wood
species is a
fast growing species which may provide a plentiful and low-cost supply. The
wood core
layer may be comprised of a single tree species or a mixture of various tree
species with
similar properties.
[0024] In the Figures which illustrate exemplary embodiments of the invention,
(1)
refers to two to three layers of parallel-grained wooden veneers, respectively
on a top and
a bottom of surface overlay materials, coated (or impregnated) with phenol-
formaldehyde
resin on double sides and treated through low-temperature drying; (2) refers
to one layer
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of cross-grained wooden veneer, respectively on a top and a bottom of surface
overlay
materials, coated (or impregnated) with phenol-formaldehyde resin on double
sides and
treated through low-temperature drying; (3) refers to a core board of the
structural strand-
based board; (4) refers to one layer of paper, respectively on a top and a
bottom of
surface overlay materials, impregnated with phenol-formaldehyde or melamine-
formaldehyde (or impregnated with a hybrid resin of the phenol-formaldehyde
and the
melamine-formaldehyde); (5) refers to a layer of bamboo-woven mat,
respectively on a
top and a bottom of surface overlay materials, impregnated with phenol-
formaldehyde
resin and treated through low-temperature drying; (6) refers to two to three
layers of
parallel-grained wooden veneers, respectively on a top and a bottom of surface
overlay
materials, coated (or impregnated) with phenol-formaldehyde resin on double
sides and
treated through low-temperature drying; (7) refers to two layers of bamboo
curtains
impregnated with phenol-formaldehyde resin and treated through low-temperature
drying
(or replacing one layer of bamboo curtain with one layer of wooden veneer
coated or
impregnated with phenol-formaldehyde resin on double sides); (8) refers to a
Kerning or
an Apitong wooden veneer of Southeast Asia or other wooden veneer with similar
properties; and (9) refers to one to two layers of wooden veneers coated or
impregnated
with phenol-formaldehyde resin on double sides and treated through low-
temperature
drying (or replacing one layer of wooden veneer with one layer of bamboo-woven
mat or
bamboo curtain impregnated with phenol-formaldehyde resin and treated through
low-
temperature drying).
[0025] In one embodiment, the invention comprises a wood composite material
comprising low density wood species as raw materials. As shown in FIG.1, the
material
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includes at least two surface layers (1) of parallel-grained wooden veneers, a
wood
veneer layer (2) of perpendicular-grained wood veneer and a core layer of a
wood strand
layer (3). Preferably, the perpendicular-grained veneer layer (2) is adjacent
the core layer
(3). In one embodiment, the composite container floorboard is fabricated from
veneers of
pine (Larix gmelini or called Dahurian larch, Pinus massoniana Lamb. or called
Chinese
red pine and so on) a core board of a structural strand-based board (furnish
from single
tree species or a mixture of various tree species with similar properties),
wherein one
layer of cross-grained wooden veneer (2) coated (or impregnated) with phenol-
formaldehyde resin on double sides and treated through low-temperature drying
and two
to three layers of parallel-grained wooden veneers (1) coated (or impregnated)
with
phenol-formaldehyde resin on double sides and treated through low-temperature
drying
are symmetrically formed, respectively, on a top and a bottom, of the core
board of the
structural strand-based board (3) sequentially.
[0026] In one example, the method of fabricating a composite container
floorboard
comprises:
a. a step of selecting and treating wooden veneers, such that wooden
veneers
contain moisture content of 12% or less and are coated or impregnated with
phenol-
formaldehyde resin on double sides of the wooden veneers with a spread of 250-
350
g/m2; the wooden veneers are conditioned until they are not viscous or they
are treated
through low-temperature drying until their moisture content becomes less than
12%; and
2.4 g insecticide is added to each kilogram of phenol-formaldehyde resin
(solid content:
45%);
CA 02638079 2008-07-17
b. a step of forming a core board, wherein the structural strand-based
board is
made into a core board (3) of the structural strand-based board after being
configured into
a board of constant thickness and being sanded to thickness of about 20 mm to
about 24
mm; and
c. a step of laying up, wherein two to three layers of parallel-
grained wooden
veneers (1) coated (or impregnated) with phenol-formaldehyde resin on double
sides and
treated through low-temperature drying and one layer of cross-grained wooden
veneer (2)
coated (or impregnated) with phenol-formaldehyde resin on double sides and
treated
through low-temperature drying are laid up onto a top and a bottom,
respectively, of the
core board (3) of the structural strand-based board before being hot pressed
at a
temperature ranging from 125 to 150 C and at maximum pressure of 1.0 ¨ 4.0 MPa
for
five to ten minutes, sequentially stepping down the press pressure, degassing,
and then
relieving press pressure.
[0027] Upon standardized processing in the later phase, a finished composite
container
floorboard with physical and mechanical properties set out below is made:
MOR in parallel direction: 95 MPa
MOR in perpendicular direction: 30 MPa
MOE in parallel direction: 10500 MPa
MOE in perpendicular direction: 3000 MPa
Panel Density: 0.75-0.90 g/cm3
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[0028] In another embodiment as shown schematically in FIG. 2, the floorboard
comprises a surface paper layer impregnated with resin (4), a woven bamboo mat
layer
(5), a parallel-gained wood veneer layer (6) and a core layer of a wood strand
layer (3).
[0029] The composite container floorboard is fabricated from phenol-
formaldehyde
resin-impregnated paper, bamboo-woven mats, wooden veneers and a structural
strand-
based board, wherein two layers of parallel-grained wooden veneers (6) coated
(or
impregnated) with phenol-formaldehyde resin on double sides and treated
through low-
temperature drying, one layer of bamboo-woven mat (5) impregnated with phenol-
formaldehyde resin and treated through low-temperature drying and one layer of
paper
(4) impregnated with phenol-formaldehyde or melamine-formaldehyde (or
impregnated
with a hybrid resin of the phenol-formaldehyde and the melamine-formaldehyde)
are
symmetrically formed, respectively, on a top and a bottom, of the core board
of the
structural strand-based board sequentially.
[00301 In one example, the method of fabricating a composite container
floorboard
comprises:
a. a step of selecting and treating wooden veneers, such that wooden
veneers
contain moisture content of 12% or less and are coated or impregnated with
phenol-
formaldehyde resin on double sides of the wooden veneers with a spread of 250-
350
g/m2; the wooden veneers are conditioned until they are not viscous or they
are treated
through low-temperature drying until their moisture content becomes less than
12%;
bamboo materials are processed into thin bamboo strips, which are further
woven into a
bamboo-woven mat, which is dried to contain less than moisture content of 15%;
upon
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conditioning or low-temperature drying; 2.4 g insecticide is added to each
kilogram of
phenol-formaldehyde resin;
b. a step of forming a core board, wherein the structural strand-based
board is
made into a core board of the structural strand-based board after being
configured into a
board of constant thickness and being sanded to the thickness of about 20 mm
to about 24
mm ; and
c. a step of laying up, wherein one layer of paper (4) impregnated with
phenol-
formaldehyde or melamine-formaldehyde (or impregnated with a hybrid resin of
the
phenol-formaldehyde and the melamine-formaldehyde), a layer of bamboo-woven
mat
(5) impregnated with phenol-formaldehyde resin and treated through low-
temperature
drying, and two layers of parallel-grained wooden veneers (6), respectively
coated (or
impregnated) with phenol-formaldehyde resin on double sides and treated
through low-
temperature drying are laid up onto a top and a bottom, respectively, of a
core board of
the structural strand-based board (3), before being hot pressed at a
temperature ranging
from 125 to 150 C and at maximum pressure of 1.0 ¨ 4.0 MPa for five to ten
minutes,
sequentially stepping down the press pressure, degassing, and then relieving
the press
pressure; or leading cool water to hot press platens until the press platens
have cooled to a
certain temperature, followed by press pressure relief.
[0031] Upon standardized processing in the later phase, a finished composite
container
floorboard with physical and mechanical properties set out below is made:
MOR in the parallel direction: 95 MPa
MOR in the perpendicular direction: 30 MPa
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MOE in the parallel direction: 10000 MPa
MOE in the perpendicular direction: ?. 3000 IVII)a
Panel Density: 0.75-0.90 g/cm3
[0032] In another embodiment shown schematically in FIG. 3, the floorboard
comprises
=10 a surface paper layer impregnated with resin (4), a woven bamboo mat
layer (5), a
bamboo curtain layer (7) and a core layer of a wood strand layer (3).
[0033] The composite container floorboard is fabricated from phenol-
formaldehyde
resin-impregnated paper, bamboo-woven mats, bamboo curtains, wooden veneers
and a
structural strand-based board, wherein two layers of bamboo curtains (7)
impregnated
with phenol-formaldehyde resin and treated through low-temperature drying, a
layer of
bamboo-woven mat (5) impregnated with phenol-formaldehyde resin and treated
through
low-temperature drying, and one layer of paper (4) impregnated with phenol-
formaldehyde are symmetrically formed, respectively, on a top and a bottom, of
the core
board of the structural strand-based boards sequentially.
[0034] The method of fabricating a composite container floorboard comprises:
a. a step of selecting and treating wooden veneers, such that wooden
veneers
contain moisture content of 12% or less and are coated or impregnated with
phenol-
formaldehyde resin on double sides of the wooden veneers with a spread of 250-
350
g/m2; the wooden veneers are conditioned until they are not viscous or they
are treated
through low-temperature drying until their moisture content becomes less than
12%;
bamboo materials are processed into thin bamboo strips, which are further
woven into a
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bamboo-woven mat and a bamboo curtain, which are dried to contain less than
moisture
content of 15%; upon conditioned or low-temperature drying, 2.4 g insecticide
is added
to each kilogram of phenol-formaldehyde resin;
b. a step of forming a core board, wherein the structural strand-based
board is
made into a core board of the structural strand-based board after being
configured into a
board of constant thickness and being sanded to the thickness of about 20 mm
to about 24
mm; and
c. a step of laying up, wherein one layer of paper (4) impregnated with
phenol-
formaldehyde or melamine-formaldehyde (or impregnated with a hybrid resin of
the
phenol-formaldehyde and the melamine-formaldehyde), one layer of bamboo-woven
mat
(5) impregnated with phenol-formaldehyde resin and treated through low-
temperature
drying and two layers of bamboo curtains (7) impregnated with phenol-
formaldehyde
resin and treated through low-temperature drying (or replacing one layer of
bamboo
curtain with one layer of wooden veneer coated or impregnated with phenol-
formaldehyde resin on double sides) are laid up onto a top and a bottom,
respectively of a
core board of the structural strand-based board (3), before being hot pressed
at a
temperature ranging from 125 to 150 C and at maximum pressure of 1.0 ¨ 4.0 MPa
for
five to ten minutes, sequentially stepping down the press pressure, degassing,
and then
relieving press pressure; or leading cool water to hot press platens until the
press platens
have cooled to a certain temperature, followed by press pressure relief.
100351 Upon standardized processing in the later phase, a finished composite
container
floorboard with physical and mechanical properties set out below is made:
CA 02638079 2008-07-17
MOR in the parallel direction: 100 MPa
MOR in the perpendicular direction: 30 MPa
MOE in the parallel direction: ?. 10500 MPa
MOE in the perpendicular direction: 3000 MPa
Panel Density: 0.75-0.90 g/cm3
10036] In another embodiment shown schematically in FIG. 4, the floorboard
comprises
a surface wood veneer layer (8), a wood veneer layer (9) and a core layer of a
wood
strand layer (3).
10037] The composite container floorboard is fabricated from a Keruing wooden
veneer,
other wooden veneers, bamboo curtains, bamboo-woven mats, and a structural
strand-
based board, wherein one to two layers of wooden veneers (9) coated or
impregnated
with phenol-formaldehyde resin on double sides and treated through low-
temperature
drying and a Keruing or Apitong wooden veneer (8) of Southeast Asia are
symmetrically
formed, respectively, on a top and a bottom, of the core board of the
structural strand-
based boards sequentially.
[0038] The method of fabricating a composite container floorboard comprises:
a. a step of selecting and treating wooden veneers, such that a
Keruing or an
Apitong wooden veneer (8) (or other wooden veneers with similar properties)
with
moisture content equal to or less than 12% and one to two layers of wooden
veneers
coated or impregnated with phenol-formaldehyde resin on double sides and
treated
through low-temperature drying (or replacing one layer of wooden veneer (9)
with one
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layer of bamboo-woven mat or bamboo curtain impregnated with phenol-
formaldehyde
resin and treated through low-temperature drying);
b. a step of forming a core board, wherein the structural strand-based
board is
made into a core board of the structural strand-based board after being
configured into a
board of constant thickness and being sanded to the thickness of about 20 mm
to about 24
mm; and
c. a step of laying up, wherein a Keruing or an Apitong wooden veneer (8)
of
Southeast Asia (or other wooden veneer with similar properties) and one to two
layers of
wooden veneers (9) coated or impregnated with phenol-formaldehyde resin on
double
sides and treated through low-temperature drying (or replacing one layer of
wooden
veneer with one layer of bamboo-woven mat or bamboo curtain impregnated with
phenol-formaldehyde resin and treated through low-temperature drying) are laid
up onto
a top and a bottom, respectively, of a core board of the structural strand-
based board (3),
before being hot pressed at a temperature ranging from 125 to 150 C and at
maxinnun
pressure of 1.0 ¨ 4.0 MPa for five to ten minutes, sequentially stepping down
the press
pressure, degassing, and then relieving the press pressure.
[0039] Upon standardized processing in the later phase, a finished composite
container
floorboard with physical and mechanical properties set out below is made:
MOR in the parallel direction: 95 Isfla
MOR in the perpendicular direction: 30 MPa
MOE in the parallel direction: 10500 MPa
MOE in the perpendicular direction: ?. 3000 MPa
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Panel Density: 0.75-0.90 g/cm3
[0040] In one embodiment, where bamboo layers are not used, the floorboard may
be
formed in a conventional press suitable for producing plywood, up to pressures
of about
1.0 to about 2.0 MPa. If a bamboo layer is incorporated into the floorboard,
higher
pressing pressures may be required, preferably up to about 4.0 MPa.
[0041] As will be apparent to those skilled in the art, various modifications,
adaptations
and variations of the forgoing specific disclosure can be made without
departing from the
scope of the invention claimed herein. The various features and elements of
the described
invention may be combined in a manner different from the combinations
described or
claims herein, without departing from the scope of the invention.
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