U.S. patent application number 12/351035 was filed with the patent office on 2009-10-01 for wood cement board.
This patent application is currently assigned to NICHIHA CORPORATION. Invention is credited to Yoshinori Hibino, Masaya Higuchi, Yuji YAMAZAKI.
Application Number | 20090242728 12/351035 |
Document ID | / |
Family ID | 41060728 |
Filed Date | 2009-10-01 |
United States Patent
Application |
20090242728 |
Kind Code |
A1 |
YAMAZAKI; Yuji ; et
al. |
October 1, 2009 |
WOOD CEMENT BOARD
Abstract
Provided is a wood cement board that has a pattern of
acute-angled and deep recesses and projections on its surface, and
that tends not to cause cracking during a hardening and curing
process, a drying process, a transportation process and so on. The
wood cement board has a pattern of recesses and projections on its
surface, in which the distance from the apex of the projections to
the rear face is 9 mm or more, and the distance from the apex of
the projections to the base point of the recesses is 2 mm or more,
and is equal to or less than half the distance from the apex of the
projections to the rear face. The average specific gravity of the
wood cement board as a whole, and the specific gravities of the
projections and the recesses are each 1.1 or more, and the
difference between the specific gravity of the projections and the
specific gravity of the recesses is less than 0.1.
Inventors: |
YAMAZAKI; Yuji; (Chita-shi,
JP) ; Higuchi; Masaya; (Nagoya-shi, JP) ;
Hibino; Yoshinori; (Ama-gun, JP) |
Correspondence
Address: |
BIRCH STEWART KOLASCH & BIRCH
PO BOX 747
FALLS CHURCH
VA
22040-0747
US
|
Assignee: |
NICHIHA CORPORATION
Nagoya-shi
JP
|
Family ID: |
41060728 |
Appl. No.: |
12/351035 |
Filed: |
January 9, 2009 |
Current U.S.
Class: |
249/16 |
Current CPC
Class: |
E04C 2/324 20130101;
E04C 2/044 20130101 |
Class at
Publication: |
249/16 |
International
Class: |
E04G 9/08 20060101
E04G009/08 |
Foreign Application Data
Date |
Code |
Application Number |
Mar 31, 2008 |
JP |
JP2008-092317 |
Claims
1. A wood cement board having a pattern of recesses and projections
on its surface, and comprising a hydraulic material, a
silica-containing material, and a wood reinforcement, wherein the
distance from the apex of the projections of the wood cement board
to a rear face of the wood cement board is 9 mm or more, the
distance from the apex of the projections to the base point of the
recesses is 2 mm or more, and is equal to or less than half the
distance from the apex of the projections to the rear face, the
average specific gravity of the wood cement board as a whole, and
the specific gravities of the projections and the recesses are each
1.1 or more, and the difference between the specific gravity of the
projections and the specific gravity of the recesses is less than
0.1.
2. The wood cement board according to claim 1, wherein the wood
cement board comprises a surface layer and a core layer, and raw
material mixtures of the surface layer and the core layer have
different compositions, and the surface layer has a denser
structure than that of the core layer.
Description
BACKGROUND OF THE INVENTION
[0001] 1. Field of the Invention
[0002] The present invention relates to a wood cement board that
has a pattern of recesses and projections on its surface, and more
particularly to a wood cement board that has a pattern of
acute-angled and deep recesses and projections on its surface, and
that tends not to cause cracking during a hardening and curing
process, a drying process, a transportation process and soon.
[0003] 2. Description of Related Art
[0004] Wood cement boards are produced by forming a mat using a raw
material mixture in which a hydraulic material, a silica-containing
material, a wood reinforcement, and as needed, other materials are
blended, and then pressing the mat, followed by hardening and
curing. Such wood cement boards are widely used as housing members
such as exterior building materials and backing materials of tiles.
Various patterns formed by recesses and projections, such as a
brick pattern and joint grooves, are created on the surface of wood
cement boards for use as exterior building materials in order to
achieve an improved appearance.
[0005] Recently, for a further improved surface design, there is a
demand for acute-angled and deep recesses and projections.
[0006] Wood cement boards for use as backing materials for tiles
need to be provided with fixing portions formed by acute-angled and
deep recesses and projections on their surface for securing the
tiles.
[0007] Examples of the method for forming recesses and projections
on the surface of a wood cement board include a method in which an
embossing roll having an engraved pattern of recesses and
projections is rolled on the surface of a half-hardened mat that
has not been pressed, while applying pressure, thereby forming the
desired pattern of recesses and projections on the surface, a
method in which the surface of a wood cement board that has
undergone a hardening and curing process is subjected to cutting
such that a pattern of recesses and projections is formed on its
surface, and a method in which a template having a pattern of
recesses and projections is placed on the surface of a mat that has
not been pressed, followed by pressing the mat together with the
template.
[0008] However, with the method using an embossing roll, it is
difficult to form acute-angled and deep recess and projection
shapes.
[0009] The method in which the surface of a wood cement board is
subjected to cutting requires a cutting process, and therefore
involves additional equipment cost and time, leading to poor
production efficiency. Moreover, defective products tend to be
produced as a result of cutting failure in the cutting process.
[0010] The method using a template can form acute-angled and deep
recess and projection shapes. However, the mat on which the
template is placed has an approximately uniform thickness and an
approximately flat surface, and therefore, the recesses have a high
specific gravity, and the projections have a low specific gravity.
Due to this specific gravity difference between the recesses and
the projections, cracking tends to occur in the wood cement board
during a hardening and curing process, a drying process, a
transportation process and so on, and a coating material is
absorbed into the substrate of the wood cement board during a
coating process. This results in the problems of a significant
reduction in the strength, the water resistance, the freeze
resistance, the weatherability and the like of the wood cement
board, an increase in the amount of the coating material required,
and nonuniform coating.
[0011] As one remedy for the above-described problems, there has
been proposed a method in which a mat layer is formed by dispersing
a raw material mixture with a plurality of partition plates placed
on predetermined areas, and then removing the raw material mixture
present on the partition plates, thereby forming a mat having
recesses on the predetermined areas, and an upper template provided
with projections corresponding to the portions on which the
recesses are formed is pressed down from above the thus formed mat,
followed by hardening and curing (JP 2001-150421 A).
[0012] However, the method disclosed in JP 2001-150421A requires
the operation of arranging partition plates, and also the operation
of removing the partition plates, and therefore has reduced
production efficiency.
[0013] Moreover, there will be an extra initial cost since various
partition plates need to be prepared depending on the depth, the
width, and the length of the recesses. In the case of forming a
pattern having a large number of recesses, or a pattern having
recesses of various shapes, the operation is more complicated,
which results in a further reduction in the production
efficiency.
[0014] Also in the case of forming recesses that have a long shape,
such as those longitudinally traversing the surface of a wood
cement board, or that have a wide shape, the workability is reduced
and the production efficiency is poor.
[0015] Furthermore, the mat layer from which the partition plates
have been removed tends to crumble, and it is therefore difficult
to achieve a specific gravity difference of less than 0.1 between
the projections and the recesses. Accordingly, the problems of the
tendency of cracking in the wood cement board during a hardening
and curing process, a drying process, a transportation process and
so on, the absorption of a coating material into the substrate of
the wood cement board during a coating process, a significant
reduction in the strength, the water resistance, the freeze
resistance, the weatherability and the like of the wood cement
board, an increase in the amount of the coating material required,
and nonuniform coating cannot be solved.
[0016] The present invention has been made in order to solve the
above-described problems, and it is an object of the invention to
provide a wood cement board that has a pattern of acute-angled and
deep recesses and projections on its surface, and that tends not to
cause cracking during a hardening and curing process, a drying
process, a transportation process and so on.
SUMMARY OF THE INVENTION
[0017] In order to attain the above-described object, a wood cement
board according to a first aspect of the present invention has a
pattern of recesses and projections on its surface, and includes a
hydraulic material, a silica-containing material, and a wood
reinforcement, wherein the distance from the apex of the
projections of the wood cement board to a rear face of the wood
cement board is 9 mm or more, the distance from the apex of the
projections to the base point of the recesses is 2 mm or more, and
is equal to or less than half the distance from the apex of the
projections to the rear face, the average specific gravity of the
wood cement board as a whole, and the specific gravities of the
projections and the recesses are each 1.1 or more, and the
difference between the specific gravity of the projections and the
specific gravity of the recesses is less than 0.1. Note that "apex
of projections" refers to the highest point in the projections, and
"base point of recesses" refers to the lowest point in the
recesses.
[0018] According to this aspect of the present invention, the wood
cement board can be produced, for example, by a method for
producing a wood cement board, including the steps of: dispersing a
raw material mixture onto a template provided with recesses
corresponding to the portions of the wood cement board on which
projections are formed, while conveying the template, thereby
forming a mat; pressurizing only a section of the mat raw material
mixture that is layered on the recesses of the template from above;
leveling the surface of the partly pressurized mat; and pressing
the resulting mat and the template together, followed by hardening
and curing. Examples of the method for performing hardening and
curing include a method in which hardening and curing is performed
at 50 to 80.degree. C. for 6 to 12 hours, followed by natural
curing or autoclave curing. Note that the natural curing is a
method in which curing is performed with outside air for 3 to 14
days, and the autoclave curing is a method in which curing is
performed at 160 to 200.degree. C. under 5 to 8 kgf/cm.sup.2 for 5
to 10 hours. In the above-described production method, the mass of
the raw material mixture layered on the recesses of the template is
larger than the mass of the raw material mixture layered on the
projections of the template. That is, the mass of the raw material
mixture on the portions of the wood cement board on which the
projections are formed is larger than the mass of the mixture on
the portions on which the recesses are formed. Accordingly, the mat
can be pressed in a uniform manner, so that the specific gravities
of the projections and the recesses in the pressed mat are
increased to 1.1 or more, and the specific gravity difference
between the projections and the recesses is decreased.
[0019] According to this aspect of the present invention, the
hydraulic material may be cement such as portland cement, blast
furnace cement, silica cement, fly ash cement, or alumina cement,
the silica-containing material of the invention may be silica sand,
silica stone powder, silica fume, blast furnace slag, fly ash,
shirasu balloon, pearlite, or the like, and the wood reinforcement
of the invention may be wood meal, wood fiber, pulp, wood fiber
bundle, wood wool, wood chip, bamboo fiber, hemp fiber, or the
like.
[0020] In addition to the above-described raw materials, it is
possible to include, as raw materials, an active lime-containing
material such as gypsum dihydrate, gypsum hemihydrate, anhydrous
gypsum, hydrated lime, or quick lime, a hardening accelerator such
as magnesium chloride, calcium formate, magnesium sulfate, calcium
chloride, calcium sulfate, sodium aluminate, potassium aluminate,
aluminum sulfate, or water glass, mineral powder such as
vermiculite, bentonite, wollastonite, or attapulgite, a water
repellent agent such as wax, paraffin, or silicone, a reinforcement
such as synthetic resin emulsion, as well as foamable thermoplastic
bead, and foamed plastic.
[0021] The mixing ratio of the above-described raw materials is as
follows: 35 to 70 mass % of the hydraulic material, 0 to 60 mass %
of the silica-containing material, and 5 to 30 mass % of the wood
reinforcement.
[0022] According to this aspect of the present invention, the
distance from the apex of the projections of the wood cement board
to the rear face is 9 mm or more, and therefore an excellent
strength is achieved, and cracking tends not to occur during a
hardening and curing process, a drying process, a transportation
process and so on. When the distance from the apex of the
projections of the wood cement board to the rear face is less than
9 mm, the strength is insufficient, and cracking tends to occur
during a hardening and curing process, a drying process, a
transportation process and so on, so that the wood cement board may
be broken during transportation.
[0023] Furthermore, according to this aspect of the present
invention, the distance from the apex of the projections of the
wood cement board to the base point of the recesses is 2 mm or
more, and is equal to or less than half the distance from the apex
of the projections to the rear face, so that the recess and
projection shapes are acute-angled and deep, and have an excellent
design quality. When tiles are secure thereto, the tiles tend not
to become detached. Wohen the distance from the apex of the
projections to the base point of the recesses is less than 2 mm,
the recess and projection shapes are not acute-angled and deep, and
therefore do not have a sufficient design quality When the distance
from the apex of the projections to the base point of the recesses
is greater than half the distance from the apex of the projections
to the rear face, the strength is reduced, and cracking tends to
occur during a hardening and curing process, a drying process, a
transportation process and so on, so that the wood cement board may
be broken during transportation.
[0024] Furthermore, the average specific gravity of the wood cement
board as a whole, and the specific gravities of the projections and
the recesses are each 1.1 or more, and the difference between the
specific gravity of the projections and the specific gravity of the
recesses is less than 0.1. Therefore, it is possible to prevent
occurrence of cracking in the wood cement board during a hardening
and curing process, a drying process, a transportation process and
so on, and to achieve an improvement in terms of the absorption of
a coating material into the substrate during a coating process. As
a result, it is possible to prevent the problems of a reduction in
the strength, the water resistance, the freeze resistance, and the
weatherability of a product of the wood cement board, an increase
in the amount of the coating material required, and nonuniform
coating. In addition, there is a secondary effect in that the wood
cement board can be produced even if the pressing capability is not
so large.
[0025] According to a second aspect of the present invention, the
wood cement board according to the first aspect includes a surface
layer and a core layer, and raw material mixtures of the surface
layer and the core layer have different compositions, and the
surface layer has a denser structure than that of the core
layer.
[0026] According to this aspect of the present invention, a wood
cement board can be produced, for example, by a method for
producing a wood cement board, including the steps of: dispersing a
surface layer raw material mixture onto a template provided with
recesses corresponding to the portions of a wood cement board on
which projections are formed, while conveying the template, thereby
forming a surface layer mat; dispersing a core layer raw material
mixture onto the surface layer mat to form a core layer mat;
pressurizing only certain sections of the raw material mixtures of
the core layer mat and the surface layer mat that are layered on
the recesses of the template from above; leveling the surface of
the partly pressurized core layer mat; further dispersing the
surface layer raw material mixture onto the core layer mat whose
surface has been leveled to form a surface layer mat; and pressing
the resulting mat having a three-layer structure and the template,
followed by hardening and curing. With the above-described
production method, the mass of the raw material mixtures layered on
the recesses of the template is larger than the mass of the raw
material mixtures layered on the projections of the template. That
is, the mass of the raw material mixtures on the portions of the
wood cement board on which the projections are formed is larger
than the mass of the raw material mixtures on the portions on which
the recesses are formed. This makes it possible to press the mat
uniformly, thereby increasing the specific gravities of the
projections and the recesses of the mat after pressing, and
decreasing the specific gravity difference between the projections
and the recesses.
[0027] Note that, although the surface layer and the core layer
each include a hydraulic material, a silica-containing material,
and a wood reinforcement, they differ in composition of the raw
material mixture. The surface layer has a dense structure
containing fine raw materials, contains 35 to 70 mass % of a
hydraulic material, 0 to 50 mass % of a silica-containing material,
and a 5 to 25 mass % of a wood reinforcement, and serves to
increase the strength, the water resistance and the like of the
wood cement board. On the other hand, the core layer is a
composition of coarse raw materials, contains 30 to 60 mass % of a
hydraulic material, 0 to 60 mass % of a silica-containing material,
and 10 to 30 mass % of a wood reinforcement, and serves to reduce
the weight of the wood cement board. The blending ratio of the
surface layer and the core layer in terms of mass is 1:1 to 1:6,
preferably 1:1 to 1:4, and the thickness of the core layer is
preferably larger than that of the surface layer.
[0028] Also according to this aspect of the present invention, it
is possible to prevent occurrence of cracking in the wood cement
board during a hardening and curing process, a drying process, a
transportation process and so on, and to achieve an improvement in
terms of the absorption of a coating material into the substrate
during a coating process. Moreover, the surface layer makes it
possible to maintain the strength, the water resistance, the freeze
resistance, and the weatherability of the wood cement board, and to
prevent the problems of an increase in the amount of the coating
material required, and nonuniform coating. In addition, there is a
secondary effect in that the wood cement board can be produced even
if the pressing capability is not so large.
[0029] With the wood cement board according to this aspect of the
present invention, the distance from the apex of the projections of
the wood cement board to the rear face is 9 mm or more, the
distance from the apex of the projections to the base point of the
recesses is 2 mm or more, and is equal to or less than half the
distance from the apex of the projections to the rear face, the
average specific gravity of the wood cement board as a whole, and
the specific gravities of the projections and the recesses are each
1.1 or more, and the specific gravity difference between the
recesses and the projections is less than 0.1. Accordingly, it is
possible to achieve a sufficient strength, prevent occurrence of
cracking that may possibly occur in the wood cement board during a
hardening and curing process, a drying process, a transportation
process and so on, and to achieve an improvement in terms of the
absorption of a coating material into the substrate during a
coating process. Consequently, it is also possible to prevent the
problems of a reduction in the strength, the water resistance, the
freeze resistance, and the weatherability of a product of the wood
cement board, an increase in the amount of the coating material
required, and nonuniform coating. Furthermore, the distance from
the apex of the projections of the wood cement board to the base
point of the recesses is 2 mm or more, and is equal to or less than
half the distance from the apex of the projections to the rear
face, so that the recess and projection shapes are acute-angled and
deep, and have an excellent design quality. When tiles are secure
thereto, the tiles tend not to become detached.
BRIEF DESCRIPTION OF THE DRAWINGS
[0030] FIG. 1 is a diagram showing a wood cement board having
projections on its surface.
[0031] FIG. 2 is a diagram showing an example of an apparatus, used
for producing the wood cement board shown in FIG. 1, that
pressurizes a section of a mat raw material mixture.
[0032] FIGS. 3A to 3H are schematic diagrams illustrating the flow
of a production process for producing the wood cement board shown
in FIG. 1 by showing the state of a mat produced in each step.
[0033] FIGS. 4A to 4H are schematic diagrams illustrating another
example of the flow of a production process for producing the wood
cement board shown in FIG. 1 by showing the state of a mat produced
in each step.
[0034] FIGS. 5A to 5F are schematic diagrams illustrating yet
another example of the flow of a production process for producing
the wood cement board shown in FIG. 1 by showing the state of a mat
produced in each step.
[0035] FIGS. 6A to 6F are schematic diagrams illustrating a further
example of the flow of a production process for producing the wood
cement board shown in FIG. 1 by showing the state of a mat produced
in each step.
[0036] FIG. 7 is a diagram showing a wood cement board having
recesses on its surface in two directions.
DETAILED DESCRIPTION OF THE INVENTION
[0037] Hereinafter, the best mode for carrying out the present
invention will be specifically described with reference to FIGS. 1
to 6F.
Embodiment 1
[0038] FIG. 1 is a diagram showing an example of a wood cement
board A having projections A1 on its surface. Here, five linear
projections A1 extending in the longitudinal direction are formed
on the surface of the wood cement board A.
[0039] FIG. 2 is a diagram showing an example of an apparatus B,
used for producing the wood cement board A shown in FIG. 1, that
rotates and pressurizes a section of a mat raw material used for
molding the wood cement board A. The apparatus B includes a
rotating shaft B1 and a plurality of rollers B2 that are formed
around the rotating shaft B1, and is placed above a conveyer for
conveying a mat, in a direction orthogonal to the traveling
direction of the mat. By rotation of the rotating shaft B1, the
rollers B2 can be brought into pressure contact with necessary
portions of the mat raw material, thereby pressurizing the mat.
Note that the rollers B2 can be adjusted in operating position and
height. In addition, the apparatus B can be detached from the
production line. Accordingly, if an apparatus B including rollers
B2 arranged and adjusted corresponding to a pattern of the recesses
of a wood cement board that is to be produced, and is switched
depending on the pattern of the recesses of a wood cement board
that is to be produced, the production efficiency of the wood
cement board can be prevented from being reduced, with excellent
workability.
[0040] FIGS. 3A to 3H are schematic diagrams illustrating an
example of the flow of a production process for producing the wood
cement board A shown in FIG. 1 by showing the states of a mat
produced in each step.
[0041] In the production process shown in FIGS. 3A to 3H, a surface
layer raw material mixture E and a core layer raw material mixture
F that differ in formulation are used.
[0042] First, a template C provided with recesses C1 corresponding
to portions on which projections are formed is placed on a conveyer
(not shown) such that the recesses C1 of the template C face
upward, as shown in FIG. 3A. While conveying the template C placed
on the conveyer, the surface layer raw material mixture E is
dispersed onto the entire surface of the template C to form a
surface layer mat as shown in FIG. 3B. Note that raw materials
having a smaller particle diameter than that of the core layer are
blended in the surface layer raw material mixture E so that the
surface of the resulting wood cement board is dense.
[0043] Next, while continuously conveying the template C on which
the surface layer raw material mixture E is deposited, the core
layer raw material mixture F is dispersed onto the entire surface
of the surface layer raw material mixture E. The core layer raw
material mixture F is dispersed in an amount larger than that of
the surface layer raw material mixture E so that the thickness of
the core layer mat is larger than that of the surface layer mat,
thereby forming a core layer mat as shown in FIG. 3C. Note that,
above the conveyance path, a brush (not shown) is provided so as to
be lightly in contact with the surface of the core layer raw
material mixture F thereby leveling the surface of the core layer
raw material mixture F. The surface leveling may be performed by
blowing air. Then, the template C on which the raw material
mixtures E and F are deposited is further conveyed with the
conveyer, and, as shown in FIG. 3D, only certain sections of the
raw material mixtures E and F that are layered on the recesses C1
of the template C are pressurized from above using the rollers B2
of the apparatus B shown in FIG. 2, which is provided above the
conveyer, thereby obtaining a mat including portions E1 and F1
resulting from pressurizing only certain sections of the raw
material mixtures that are layered on the recesses C1 of the
template C, as shown in FIG. 3E. Then, the mat including the
pressurized portions E1 and F1 is brought into light contact with
the surface of the brush (not shown) provided above the conveyance
path, or subjected to air blowing, while conveying the mat, thereby
obtaining a mat whose surface has been leveled, as shown in FIG.
3F. Note that, in order to achieve a leveled surface, portions
other than E1 and F1 that are higher than E1 and F1 may be scraped
off with a brush or air (not shown) to level the surface of the
mat.
[0044] The template C on which the raw material mixtures E and F
are deposited is further conveyed on the conveyer, and the surface
layer raw material mixture E is dispersed again onto the entire
surface of the raw material mixture F, thereby forming a surface
layer mat on the core layer mat, as shown in FIG. 3G. Then, as
shown in FIG. 3H, a flat pressing plate D is placed on the surface
of the thus obtained mat, and the mat is pressurized together with
the template C, followed by hardening and curing.
[0045] The above-described production process carries out the
dispersal of the raw material mixtures, the partial pressurization
of the raw material mixtures, and the surface leveling of the raw
material mixtures while conveying the template C, and therefore
provides a good production efficiency. Furthermore, only certain
sections of the raw material mixtures E and F that correspond to
the recesses C1 of the template C are pressurized, and the surface
of the core layer mat is leveled after the pressurization.
Accordingly, a uniform load is applied to the mat during pressing,
so that it is possible to produce the wood cement board even if the
pressing capability is not so large, and to decrease the specific
gravity difference between the recesses and the projections on the
surface of the wood cement board A, thereby achieving an
improvement in terms of the occurrence of cracking in the wood
cement board A and of the absorption of a coating material into the
substrate. Furthermore, since the amount of the raw material
mixture E in the surface layer remains unchanged, it is possible to
maintain the strength, the water resistance, the freeze resistance,
and the weatherability of the wood cement board A, and to prevent
the problems of an increase in the amount of the coating material
required, and nonuniform coating.
[0046] FIGS. 4A to 4H are schematic diagrams illustrating another
example of the flow of a production process for producing the wood
cement board A shown in FIG. 1 by showing the state of a mat
produced in each step.
[0047] The production process shown in FIGS. 4A to 4H is the same
as the production process shown in FIGS. 3A to 4H in that the
surface layer and the core layer differ in formulation and
thickness of the raw material mixture used and the surface layer
raw material mixture E and the core layer raw material mixture F
are used, the core layer raw material mixture F is dispersed onto
the surface layer raw material mixture E, the core layer mat has a
thickness larger than that of the surface layer mat, only certain
sections of the raw material mixtures E and F that correspond to
the recesses C1 of the template C are pressurized using the
apparatus B shown in FIG. 2, which is provided above the conveyer,
thereby producing a mat including the pressurized portions E1 and
F1, and the surface of the mat including the pressurized portions
E1 and F1 is leveled before dispersing the surface layer raw
material mixture E onto the entire surface of the raw material
mixture F, followed by pressing, and hardening and curing. However,
the production process shown in FIGS. 4A to 4H differs from the
production process shown in FIGS. 3A to 3H in that the flat
pressing plate D is placed on the conveyer first, as shown in FIG.
4A, the dispersal of the raw material mixtures, the partial
pressurization of the raw material mixtures, and the surface
leveling of the raw material mixtures are carried out while
conveying the flat pressing plate D, as shown in FIGS. 4B to 4G,
and the template C provided with the recesses C1 corresponding to
the portions on which the projections are formed is placed on a mat
having a three-layer structure, as shown in FIG. 4H. Note that the
template C is placed on the mat with the recesses C1 facing
downward, and the pressurized positions correspond with the
positions of the recesses C1.
[0048] The above-described production process also carries out the
dispersal of the raw material mixtures, the partial pressurization
of the raw material mixtures, and the surface leveling of the raw
material mixtures while conveying the pressing plate D, and
therefore provides a good production efficiency as with the
production method shown in FIGS. 3A to 3H. Furthermore, only
certain sections of the raw material mixtures E and F that
correspond to the recesses C1 of the template C are pressurized,
and the surface of the core layer mat is leveled after the
pressurization. Accordingly, a uniform load is applied to the mat
during pressing, so that it is possible to produce the wood cement
board even if the pressing capability is not so large, and to
decrease the specific gravity difference between the recesses and
the projections on the surface of the wood cement board A, thereby
achieving an improvement in terms of the occurrence of cracking in
the wood cement board A and of the absorption of a coating material
into the substrate. Furthermore, since the amount of the raw
material mixture E in the surface layer remains unchanged, it is
possible to maintain the strength, the water resistance, the freeze
resistance, and the weatherability of the wood cement board A, and
to prevent the problems of an increase in the amount of the coating
material required, and nonuniform coating.
[0049] FIGS. 5A to 5F are schematic diagrams illustrating another
example of the flow of a production process for producing the wood
cement board A shown in FIG. 1 by showing the state of a mat
produced in each step.
[0050] The production method shown in FIGS. 5A to 5H uses a single
formulation of a raw material mixture, i.e., only a raw material
mixture G.
[0051] First, a template C provided with recesses C1 corresponding
to the portions on which projections are formed is placed on a
conveyer such that the recesses C1 of the template C face upward as
shown in FIG. 5A. Next, the raw material mixture G is dispersed
onto the entire surface of the template C placed on the conveyer
while conveying the template C, thereby forming a mat as shown in
FIG. 5B. Note that, above the conveyance path, a brush (not shown)
is provided so as to be lightly in contact with the surface of the
raw material mixture G, thereby leveling the surface of the raw
material mixture G. The surface leveling may be performed by
blowing air. Then, the template C on which the raw material mixture
G is layered is further conveyed on the conveyer, and only a
section of the mat raw material mixture G that is layered on the
recesses C1 of the template C is pressurized from above using the
rollers B2 of the apparatus B shown in FIG. 2, which is provided
above the conveyer, thereby obtaining a mat including portions G1
resulting from pressurizing only a section of the raw material
mixture that is layered on the recesses C1 of the template C, as
shown in FIG. 5D. Then, the mat including the pressurized portions
G1 is brought into light contact with the surface of a brush (not
shown) provided above the conveyance path in the conveyance
direction, or subjected to air blowing, thereby leveling the
surface as shown in FIG. 5E. Thereafter, as shown in FIG. 5F, a
pressing plate D having a flat surface is placed on the resulting
mat, and the mat is pressed together with the template C, followed
by hardening and curing. Note that, in order to achieve a leveled
surface, portions other than G1 that are higher than G1 may be
scraped off with a brush or air (not shown) to level the surface of
the mat.
[0052] The above-described production process carries out the
dispersal of the raw material mixture, the partial pressurization
of the raw material mixture, and the surface leveling of the raw
material mixture while conveying the template C, and uses only a
single formulation of a raw material mixture, and it therefore
provides a better production efficiency than that of the production
processes shown in FIGS. 3A to 3H, and 4A to 4H. Additionally, only
a section of the raw material mixture G that corresponds to the
recesses C1 of the template C is pressurized, and the surface of
the mat is leveled after the pressurization. Accordingly, as with
the production processes shown in FIGS. 3A to 3H, and 4A to 4H, a
uniform load is applied to the mat during pressing, so that it is
possible to produce the wood cement board even if the pressing
capability is not so large, and to decrease the specific gravity
difference between the recesses and the projections on the surface
of the wood cement board A, thereby achieving an improvement in
terms of the occurrence of cracking in the wood cement board A and
of the absorption of a coating material into the substrate.
Furthermore, as with the production processes shown in FIGS. 3A to
3H and 4A to 4H, it is possible to maintain the strength, the water
resistance, the freeze resistance, and the weatherability of the
wood cement board A, and to prevent the problems of an increase in
the amount of the coating material required, and nonuniform
coating.
[0053] FIGS. 6A to 6F are schematic diagrams illustrating yet
another example of the flow of a production process for producing
the wood cement board A shown in FIG. 1 by showing the state of a
mat produced in each step.
[0054] The production process shown in FIGS. 6A to 6F is the same
as the production process shown in FIGS. 5A to 5F in that it uses a
single formulation of a raw material mixture, i.e., only the raw
material mixture G, the raw material mixture G is dispersed during
conveyance on the conveyer, only a section of the mat raw material
mixture G that corresponds to the recesses C1 of the template C is
pressurized from above using the rollers B2 of the apparatus B
shown in FIG. 2, which is provided above the conveyer, thereby
producing a mat including the pressurized portions G1, and the
surface of the mat including the pressurized portions G1 is leveled
before pressing, and hardening and curing. However, the production
process shown in FIGS. 6A to 6F differs from the production method
shown in FIGS. 5A to 5F in that the raw material mixture G is
dispersed onto the pressing plate D first, as shown in FIG. 6A, the
dispersal of the raw material mixture, the partial pressurization
of the raw material mixture, and the surface leveling of the raw
material mixture are carried out while conveying the flat pressing
plate D, as shown in FIGS. 6B to 6E, and the template C provided
with the recesses C1 corresponding to the portions on which the
projections are formed is placed on the mat, as shown in FIG. 6F.
Note that the template C is placed on the mat with the recesses C1
facing downward, and the pressurized positions coincide with the
positions of the recesses C1.
[0055] The above-described production process carries out the
dispersal of the raw material mixture, the partial pressurization
of the raw material mixture, and the surface leveling of the raw
material mixture while conveying the pressing plate D, and uses
only a single formulation of a raw material mixture, and it
therefore provides a good production efficiency as with the
production processes shown in FIGS. 5A to 5F. Additionally, only a
section of the raw material mixture G that corresponds to the
recesses C1 of the template C is pressurized, and the surface of
the mat is leveled after the pressurization. Accordingly, as with
the production processes shown in FIGS. 3A to 3H, 4A to 4H, and 5A
to 5F, a uniform load is applied to the mat during pressing, so
that it is possible to produce the wood cement board even if the
pressing capability is not so large, and to decrease the specific
gravity difference between the recesses and the projections on the
surface of the wood cement board A, thereby achieving an
improvement in terms of the occurrence of cracking in the wood
cement board A and of the absorption of a coating material into the
substrate. Furthermore, as with the production processes shown in
FIGS. 3A to 3H, 4A to 4H, and 5A to 5F, it is possible to maintain
the strength, the water resistance, the freeze resistance, and the
weatherability of the wood cement board A, and to prevent the
problems of an increase in the amount of the coating material
required, and nonuniform coating.
[0056] It should be appreciated that the present invention is not
limited to the above-described embodiment.
[0057] In the production processes shown in FIGS. 3A to 3H, and 4A
to 4H, the surface layer raw material mixture E provided on the
front side and the surface layer raw material mixture E provided on
the rear side may have different formulations, or the surface layer
raw material mixture E may not be provided on the rear side.
[0058] When the recesses are formed in two orthogonal directions as
shown in FIG. 7, it is possible to form a mat having recesses in
two directions by providing two conveyers for performing the
longitudinal conveyance and the transverse conveyance, and placing
the apparatus B shown in FIG. 2 above each of the conveyers.
[0059] Furthermore, 5 mass % of aluminum sulfate as a hardening
accelerator was externally added to a raw material mixture
containing 40 mass % of portland cement as a hydraulic material, 38
mass % of silica sand as a silica-containing material, and 11 mass
% of wood chip and 11 mass % of pulp as wood reinforcements. Using
the resulting raw material mixture, a wood cement board as shown in
FIG. 1 was produced by the wood cement board production process
shown in FIGS. 5A to 5E The obtained wood cement board was
subjected to autoclave curing at 165.degree. C. under 6
kgf/cm.sup.2 for six hours, thereby obtaining Example 1, which was
a wood cement board composed of a single layer and having an
overall thickness of 16 mm. Note that, in the wood cement board,
the distance from the apex of the projections to the base point of
the recesses was set to 4 mm in order to form acute-angled and deep
recess and projection shapes. The pressing pressure applied to the
mat and the template for the wood cement board to have an overall
thickness of 16 mm was 45 kgf/cm.sup.2.
[0060] As another example, 5 mass % of aluminum sulfate as a
hardening accelerator was externally added to a raw material
mixture containing 38 mass % of portland cement as a hydraulic
material, 38 mass % of silica sand as a silica-containing material,
24 mass % of pulp as a wood reinforcement, to prepare a surface
layer raw material mixture. Meanwhile, 3 mass % of aluminum sulfate
as a hardening accelerator was externally added to a raw material
mixture containing 40 mass % of portland cement as a hydraulic
material, 40 mass % of silica sand as a silica-containing material,
and 20 mass % of wood chip as a wood reinforcement to prepare a
core layer raw material mixture. Using these raw material mixtures,
a wood cement board as shown in FIG. 1 was produced by the wood
cement board production process shown in FIGS. 3A to 3H. The wood
cement board was subjected to autoclave curing at 165.degree. C.
under 6 kgf/cm.sup.2 for six hours, thereby obtaining Example 2,
which was a wood cement board composed of three layers and having a
thickness of 16 mm. Note that the blending ratio in terms of mass
of the surface layer and the core layer was 1:4, and the distance
from the apex of the projections to the base point of the recesses
was set to 4 mm also for this wood cement board. In Example 2, the
pressing pressure applied to the mat and the template for the wood
cement board to have an overall thickness of 16 mm as with Example
1 was 45 kgf/cm.sup.2.
[0061] Further, for comparison with Example 1, Comparative Example
1, which was composed of a single layer, was obtained in the same
manner as in the production method of Example 1, except for
omitting pressurizing only a section of the raw material mixture
that is layered on the recesses of the template from above, and
leveling the surface of the partly pressurized mat. In Comparative
Example 1, the pressing pressure applied to the mat and the
template for the wood cement board to have an overall thickness of
16 mm as with Example 1 was 50 kgf/cm.sup.2.
[0062] Further, for comparison with Example 2, Comparative Example
2, which was composed of three layers, was obtained in the same
manner as in the production method of Example 2, except for
omitting pressurizing only a section of the raw material mixture
that is layered on the recesses of the template from above, and
leveling the surface of the partly pressurized mat. In Comparative
Example 2, the pressing pressure applied to the mat and the
template for the wood cement board to have an overall thickness of
16 mm as with Example 2 was 50 kgf/cm.sup.2.
[0063] For Examples 1 and 2 and Comparative Examples 1 and 2
described above, the average specific gravity of each of the wood
cement boards as a whole, the specific gravities of the projections
and the recesses, as well as the surface water absorption and the
bending strength of each of the wood cement boards were measured,
and the results are shown in Table 1. The bending strength was
measured in accordance with JIS A 1408 using test samples of
500.times.400 mm. The surface water absorption was measured by a
frame placement method in which a frame of 0.2.times.0.2 m was
provided on the surface of a coated plate, and the coated plate was
stood still for 24 hours, with a certain amount of water placed
within the frame. The change in mass of the coated plate before and
after the measurement was calculated using Formula (1), and shown
as the surface water absorption.
Mass (g) after measurement (after 24 hours)-Initial mass (g)
0.2.times.0.2 (frame area: m.sup.2) (1)
TABLE-US-00001 TABLE 1 Com. Com. Ex. 1 Ex. 2 Ex. 1 Ex. 2 raw single
portland cement 40% -- 40% -- material layer silica sand 38% -- 38%
-- (mass %) wood chip 11% -- 11% -- pulp 11% -- 11% -- aluminum
sulfate 5% -- 5% -- (externally added) surface portland cement --
38% -- 38% layer silica sand -- 38% -- 38% pulp -- 24% -- 24%
aluminum sulfate -- 5% -- 5% (externally added) core layer portland
cement -- 40% -- 40% silica sand -- 40% -- 40% wood chip -- 20% --
20% aluminum sulfate -- 3% -- 3% (externally added) pressing
surface pressure (kgf/cm.sup.2) 45 45 50 50 physical average
specific gravity of wood 1.15 1.16 1.06 1.08 properties cement
board as a whole specific gravity of projections of 1.12 1.14 1.00
1.00 wood cement board specific gravity of recesses of 1.18 1.19
1.15 1.16 wood cement board surface water absorption (g/m.sup.2)
800 700 1800 1500 bending strength (N/mm.sup.2) 13 14 10 11
[0064] As shown in Table 1, in Examples 1 and 2, the average
specific gravity of the wood cement board as a whole, and the
specific gravities of the projections and the recesses were 1.1 or
more, and the difference between the specific gravity of the
projections and the specific gravity of the recesses is less than
0.1. Therefore, Examples 1 and 2 are excellent in terms of the
surface water absorption and the bending strength. However, in
Comparative Examples 1 and 2, the average specific gravity of the
wood cement board as a whole, and the specific gravities of the
projections and the recesses were less than 1.1, and the difference
between the specific gravity of the projections and the specific
gravity of the recesses is greater than 0.1. Therefore, Comparative
Examples 1 and 2 are inferior to Examples 1 and 2 in terms of the
surface water absorption and the bending strength.
[0065] Additionally, wood cement boards with an overall thickness
of 8 mm in which the distance from the apex of the projections to
the base point of the recesses was 4 mm were produced in the same
manner as in the production methods of Examples 1 and 2. The wood
cement boards were broken during conveyance, and exhibited poor
strength.
[0066] Furthermore, wood cement boards in which the distance from
the apex of the projections to the base point of the recesses was 1
mm were produced in the same manner as in the production methods of
Examples 1 and 2. The wood cement boards exhibited approximately
the same level of physical properties as those of Examples 1 and 2,
but the recesses and the projections were not observed to be
acute-angled, and therefore had a poor design quality.
[0067] As has been described above, with the wood cement board
according to the present invention, the distance from the apex of
the projections of the wood cement board to the rear face is 9 mm
or more, the distance from the apex of the projections to the base
point of the recesses is 2 mm or more, and is equal to or less than
half the distance from the apex of the projections to the rear
face. Moreover, the average specific gravity of the wood cement
board as a whole, and the specific gravities of the projections and
the recesses are each 1.1 or more, and the specific gravity
difference between the recesses and the projections is less than
0.1. Accordingly, it is possible to provide a sufficient strength,
prevent cracking that may occur in the wood cement board during a
hardening and curing process, a drying process, a transportation
process and so on, and to achieve an improvement in terms of the
absorption of a coating material into the substrate during a
coating process. Consequently, it is also possible to prevent the
problems of a reduction in the strength, the water resistance, the
freeze resistance, and the weatherability of a product of the wood
cement board, an increase in the amount of the coating material
required, and nonuniform coating. Furthermore, since the distance
from the apex of the projections of the wood cement board to the
base point of the recesses is 2 mm or more, and is equal to or less
than half the distance from the apex of the projections to the rear
face, the recess and projection shapes are acute-angled and deep,
and also have an excellent design quality. When tiles are secured
thereto, the tiles tend not to become detached.
* * * * *