Technical Field
[0001] The present invention relates to a board for a concrete form panel usable for building
construction and civil engineering works. More particularly, the present invention
relates to such a board for a concrete form panel, which is capable of providing good
recyclability, high strength, good hold of nails hammered therein together with easiness
in removing nails therefrom, as well as good workability.
Background Art
[0002] There have been proposed and used various types of boards used for fabricating concrete
form panels, including plywood boards and metal boards. Recently, larger and larger
concrete form panels are desired in order to achieve higher efficiency in building
construction and the like, but the larger concrete form panels may be often difficult
to handle due to the greater weights; plywood boards and metal boards inherently have
relatively heavy weights.
[0003] In order to fabricate light-weight concrete form panels, there have been also proposed
various types of light-weight boards which have a multi-layered structure comprising
a core layer formed of a light-weight, high-expansion foamed synthetic resin material
and a pair of skin layers formed essentially of a synthetic resin material and prodded
on and covering the both side surfaces of the core layer
[0004] One example of such light-weight boards is shown in Published Japanese Utility Model
Application No. Hei-7-25114 (No. 25114/1995), which discloses a multi-layered board
comprising a core layer formed of a thermoplastic synthetic resin foam and a pair
of skin layers provided on and covering the both side surfaces of the core layer,
wherein the skin layers are formed of a synthetic resin material reinforced by a mat
of uniformly oriented glass fibers embedded in the synthetic resin material. Published
Japanese Patent Application No. Hei-8-93217 (No. 93217/1996) disdoses a board for
a concrete form panel comprising a core layer formed of an urethane-resin foam and
a pair of skin layers provided on and covering the both side surfaces of the core
layer, wherein the she layers are formed of a polypropylene material embedded with
glass fibers. Finally, Published Japanese Patent Application No. Hei-8-100523 (No.
100523/1996) discloses a board for a concrete form panel, the board being formed of
a synthetic resin foam, such as a styrene resin foam, wherein the board comprises
an inner core layer formed of that synthetic resin foam highly expanded, and a Pair
of skin layers formed of that synthetic resin foam less expanded and with glass fibers
embedded therein.
[0005] These prior-art boards used for fabricating a light-weight concrete form panel, however,
has several shortcomings due to the use of glass fibers, as shown below.
(i) A board for a concrete form panel using glass fibers tends to be excessively hard,
so that it is often difficult to hammer nails into the board
(ii) Sawing such a board tends to result in dispersion of glass powder originating
from the glass fibers into environment. Further, the teeth of the saw may be often
damaged by the glass fibers.
(iii) When an amount of concrete is filled in the cavity formed by concrete form panels,
the aggregate in the concrete tends to cause abrasion in the surface of the panels,
so that some of the glass fibers are exposed to the outside of the panels to make
intimate contact with the surface of the formed concrete. This often makes it difficult
to remove the panels from the surface of the formed concrete.
(iv) Any synthetic resin materials with glass fibers embedded therein are difficult
to recycle, although it is more and more desired in the context of the raise in the
consciousness of the global environmental protection.
On the other hand, any prior-art boards for concrete form panels formed of synthetic
resins, such as polypropylene and polystyrene, and using no glass fiber have a shortcoming
that:
(v) they provide poor hold of nails hammered in them.
Disclosure of the Invention
[0006] The inventors of the present invention has approached to the above-mentioned problems
to find the solution.
[0007] According to the present invention, there is provided a board for a concrete form
panel comprising: a core plate formed of a first synthetic resin material and having
both side surfaces; and a pair of skin layers formed of a second synthetic resin material
and provided on and covering the both side surfaces of the core plate. The first synthetic
resin material for the core plate is cellular such that the core plate provides hold
of nails hammered therein. The skin layers have water-impermeability and strippability
from a surface of formed concrete. In addition, the first synthetic resin material
for the core plate and the second synthetic resin material for the skin layers have
substantially the same composition.
[0008] The first synthetic resin material for the core plate may preferably have an elastic
modulus in flexure greater than 5,000 kgf/cm
2 (about 490 megapascals).
[0009] The first synthetic resin material for the core plate may preferably comprise a foamed
synthetic resin material expanded with an expansion ratio lower than 400%.
[0010] The second synthetic resin material for the skin layers may preferably comprise a
non-foamed synthetic resin material.
[0011] The first synthetic resin material for the core plate and the second synthetic resin
material for the skin layers may comprise a copolymer of a rubber-like resin monomer
and a non-rubber-like resin monomer.
[0012] Alternatively, the first synthetic resin material for the core plate and the second
synthetic resin material for the skin layers may comprise an alloy of a rubber-like
resin and a non-rubber-like resin.
[0013] The rubber-like resin may be selected from the group consisting of butadiene rubber,
butylene rubber, isoprene rubber and chloroprene rubber.
[0014] The non-rubber-like resin may comprise a styrene resin.
[0015] The core plate may consist essentially of said first synthetic resin material.
[0016] The skin layer may consist essentially of said second synthetic resin material.
[0017] The skin layer may have an outer surface with a relief pattern formed therein.
[0018] The ratio in thickness of the core plate to the skin layer may fall in the range
from 20:1 to 4:1.
Brief Description of the Drawings
[0019]
Fig. 1 is a perspective view of a concrete form panel fabricated by using a board
in accordance with an embodiment of the present invention; and
Fig. 2 is a sectional view of a part of the concrete form panel shown in Fig. 1.
Best Mode for Carrying Out the Invention
[0020] A board for a concrete form panel in accordance with the present invention comprises
a core plate formed of a first synthetic resin material and having both side surfaces.
The board further comprises a pair of skin layers formed of a second synthetic resin
material and provided on and covering the both side surfaces of the core plate. The
first synthetic resin material for the core plate may preferably have an elastic medulus
in flexure greater than 5,000 kgf/cm
2 (about 490 megapascals), which can provide sufficient strength for use as a board
for a concrete form panel. The first synthetic resin material may be preferably flexible
and cellular such that the core plate provides good hold of nails hammered in the
core plate. The first synthetic resin material may preferably comprise a thermoplastic
synthetic resin material in order to provide good recyclability of the board
[0021] An example of cellular synthetic resin materials suitable for the core plate is a
foamed synthetic resin material. The formed synthetic resin material may be preferably
expanded with a relatively low expansion ratio lower than 400%, and more preferably
lower than 300%, in order to provide the board with high rigidity, high impact, high
strength and good bold of nails hammered therein. The foamed synthetic resin material
may be preferably a closed-cell foam, which generally have higher strength than an
open-cell foam.
[0022] The first synthetic resin material for the core plate and the second synthetic resin
material for the skin layers may contain a rubber-like resin so as to provide the
board with flexibility As an example, the first and second synthetic resin materials
may comprise a copolymer of a rubber-like resin monomer and a non-rubber-like resin
monomer. As another example, they may comprise an alloy of a rubber-like resin and
a non-rubber-like resin. Suitable rubber-like resins include, but are not limited
to, butadiene rubber, butylene rubber, isoprene rubber and chloroprene rubber. A synthetic
resin material containing a rubber-like resin is highly preferable for the present
invention because the concrete form panel using the board formed of such a material
would provide high strength and good bold of nails hammered therein together with
easiness in removing nails therefrom. The amount of such a rubber-like resin in the
total of the synthetic resin material may be preferably about 5% to about 30% by weight.
[0023] In accordance with the present invention, the pair of skin layers formed of the second
synthetic resin material and provided on and covering the both side surfaces of the
core plate serve to reinforce the core plate and improve the rigidity of the board.
The first synthetic resin material for the core plate and the second synthetic resin
material for the skin layers have substantially the same composition. The skin layers
have water-impermeability and strippability from a surface of formed concrete. While
the second synthetic resin material for the skin layers may be a foamed resin material
or may be a non-foamed resin material, it may be preferably a non-foamed resin material
in order to provide the board with higher rigidity.
[0024] The outer surface of the skin layer, which will be in contact with the surface of
the concrete filled in the cavity defined by the concrete form panels, may preferably
have a relief pattern formed therein. The relief pattern may be an ornamental pattern,
such as a woodgrain pattern and a lattice pattern, which is transferred onto the surface
of the formed concrete. The relief pattern may also serve to improve adhesion of mortar
to the surface of the formed concrete if the surface is to be covered by finish mortar
or if tiles are furnished onto the surface through a mortar layer formed between the
tiles and the surface of the formed concrete. The relief pattern may be formed through
a known technique, such as embossing. The difference in height between higher and
lower portions of the relief pattern may be preferably a few millimeters or less.
[0025] The skin layers may preferably comprise a highly crosslinked polymer material in
order to improve durability against deterioration factors including abrasion, exposure
to the ultraviolet radiation and others.
[0026] As described above, a board for a concrete form panel according to the present invention
comprises a core plate formed of a first synthetic resin material and having both
side surfaces; and a pair of skin layers formed of a second synthetic resin material
and provided on and covering the both side surfaces of the core plate, wherein the
first synthetic resin material for the core plate and the second synthetic resin material
for the skin layers have substantially the same composition.
[0027] The core plate may consist essentially of the first synthetic resin material and
the skin layers may consist essentially of the second synthetic resin material, so
that the core plate and the skin layers do not need any glass fibers to be embedded
therein.
[0028] This highly facilitates recycling of boards for concrete form panels, in which used
boards may be reformed into recycled pellets and bed mixed with new pellets for fabricating
core plates of new boards. The recycled pellets may be mixed with the new pellets
up to 80% by weight of the resultant, mixed pellets. Thus, a board for a concrete
form panel in accordance with the present invention provides improved recyclability.
[0029] The skin layer has a thickness smaller than the core plate. The ratio in thickness
of the core plate to the skin layer may be preferably 20:1 to 4:1. With the thickness
ratio falling in this range, the elastic modulus in flexure of the board itself greater
than 18,000 kgf/cm
2 (about 1,760 megapascals) may be achieved where the elastic modulus in flexure of
the first synthetic resin material for the core plate is greater than 5,000 kgf/cm
2 (about 490 megapascals). This provides the board with a sufficient strength for eliminating
glass fibers embedded therein.
[0030] Figs. 1 and 2 show a board 1 for a concrete form panel 4 according to an embodiment
of the present invention.
[0031] The board 1 comprises a core plate 2 formed of a first synthetic resin material and
having both side surfaces, and a pair of skin layers 3 formed of a second synthetic
resin material and provided on and covering the both side surfaces of the core plate
2. The board 1 is rectangular in shape. Wooden stiffeners 5 are provided along the
peripheral edges and the longitudinal center line of the board 1 and secured to the
board 1 by means of nails 6 hammered therein, so as to form the concrete form panel
4.
[0032] Suitable nails for securing the stiffeners 5 to the board 1 include those having
a shank with a diameter of two to five millimeters.
[0033] The board 1 provides good hold of nails hammered therein, so that it hardly allow
the nails to loosen even six months after they are hammered in the board 1.
[0034] The present invention will be described in more detail below with reference to an
exemplified board of the present invention.
[0035] The exemplified board was fabricated to comprise a core plate having both side surfaces
and a pair of skin layers provided on and covering the both side surfaces of the core
plate, as described above. The core plate was formed of a first synthetic resin material
and the skin layers were formed of a second synthetic resin material. Either of the
first and second synthetic resin materials comprised a thermoplastic styrene resin
material, which was a copolymer comprising about 86% by weight of a styrene resin
monomer (non-rubber-like resin monomer) and about 14% by weight of a butylene rubber
monomer (rubber-like resin monomer).
[0036] The core plate was rectangular in shape and has a thickness of 8 millimeters, a width
of 600 millimeters and a length of 1800 millimeters. The skin layer was made from
a sheet of the above-mentioned styrene resin material having a thickness of 2 millimeters
and was applied and attached onto a respective side surface of the core plate by means
of adhesive. The core plate was formed of the above-mentioned styrene resin material
foamed and expanded with an expansion ration of about 300%. The sheets for the skin
layers were formed of the above-mentioned styrene resin unexpanded or non-foamed.
[0037] The board thus fabricated was tested to show an elastic modulus in flexure of about
18,000 kgf/cm
2 (about 1,760 megapascals), which can provide a sufficient rigidity for a board used
for fabricating a concrete form panel.
[0038] Concrete form panels as shown in Figs. 1 and 2 were fabricated using such boards
and assembled to define a cavity for a concrete wall, an amount of concrete was filled
in the cavity, and the concrete panels were removed after the concrete was hardened
The concrete wall thus constructed was found to have both appearance and characteristics
as excellent as those of a concrete wall which may be constructed using typical concrete
form panels comprising a plywood board.
[0039] The concrete form panels fabricated using the boards of the present invention were
retained in the assembled state during about six months. It was found that the concrete
form panels provided good hold of the nails hammered in the boards of panels, so that
rehammering of the nails was unnecessary during that six-month period. The concrete
form panels were reused twelve times and then inspected to show adhesion of little
concrete on the surfaces of the boards of the panels. The nails were removed from
the boards as easily as from a typical plywood board for a concrete form panel.
Industrial Applicability
[0040] As understood from the above, the present invention provides a board for a concrete
form panel, which is capable of providing good recyclability, high strength, good
hold of nails hammered therein together with easiness in removing nails therefrom,
as well as good workability.
1. A board for a concrete form panel comprising:
a core plate formed of a first synthetic resin material and having both side surfaces;
and
a pair of skin layers formed of a second synthetic resin material and provided on
and covering said both side surfaces of said core plate;
wherein said first synthetic resin material for said core plate is cellular such that
said core plate provides hold of nails hammered therein;
wherein said skin layers have water-impermeability and strippability from a surface
of formed concrete; and
wherein said first synthetic resin material for said core plate and said second synthetic
resin material for said skin layers have substantially the same composition.
2. Aboard for a concrete form panel according to claim 1, wherein:
said first synthetic resin material for said core plate has a elastic modulus in flexure
greater than 5,000 kgf/cm2 (about 490 megapascals).
3. Aboard for a concrete form panel according to either claim 1 or 2, wherein:
said first synthetic resin material for said core plate comprises a foamed synthetic
resin material expanded with an expansion ratio lower than 400%.
4. A board for a concrete form panel according to claim 3, wherein:
said second synthetic resin material for said skin layers comprises a non-foamed synthetic
resin material.
5. A board for a concrete form panel according to any one of claims 1 to 4, wherein:
said first synthetic resin material for said core plate and said second synthetic
resin material for said skin layers comprise a copolymer of a rubber-like resin monomer
and a non-rubber-like resin monomer.
6. A board for a concrete form panel according to any one of claims 1 to 4, wherein:
said first synthetic resin material for said core plate and said second synthetic
resin material for said skin layers comprise an alloy of a rubber-like resin and a
non-rubber-like resin.
7. Aboard for a concrete form panel according to ether claim 5 or 6, wherein:
said rubber-like resin is selected from the group consisting of butadiene rubber,
butylene rubber, isoprene rubber and chloroprene rubber.
8. Aboard for a concrete form panel according to any one of claims 6, 7 and 8, wherein:
said non-rubber-like resin comprises a styrene resin.
9. A board for a concrete form panel according to any one of claims 1 to 8, wherein:
said core plate consists essentially of said first synthetic resin material.
10. Aboard for a concrete form panel according to any one of claims 1 to 9, wherein:
said skin layer consists essentially of said second synthetic resin material.
11. Aboard for a concrete form panel according to any one of claims 1 to 10, wherein:
said skin layer has an outer surface with a relief pattern formed therein.
12. A board for a concrete form panel according to any one of claims 1 to 11, wherein:
the ratio in thickess of said core plate to said skin layer fells in the range from
20:1 to 4:1.