Note: Descriptions are shown in the official language in which they were submitted.
CA 02565478 2006-10-24
INSECT PROOF BOARDS
BACKGROUND OF THE INVENTION
Field of the Invention
[0001]
The present invention relates to an insect proof board used
as, for example, a building b"oard.
Description of the Prior Art
[0002]
Building boards used for buildings desirably possess insect
proof property so as to be not invaded by harmful insects such
as termite or the like.
[0003]
In order to impart insect proof property to boards, there
have conventionally been provided a constitution in which a top
paint containing an insecticide is lightly applied to the top
layer of a colored steel board (for example, JP-A-2003-127272) ,
a constitution in which a coating composition incorporated with
colloidal silica, a silane-based water repellent agent, a
repellent for ant and the like in an aqueous resin emulsion is
applied to a substrate (for example, JP-A-1999-256076) , and a
constitution in which a liquid insecticide is adsorbed on silica
gel particles and is fixed to the surface of a substrate via
an adhesive layer (for example, JP-A-2001-158702).
[0004]
According to the prior art techniques in which an
insecticide mixed with a coating composition is applied to a
substrate, there has been a problem that the insecticide is
diluted with a resin which is a main component of the coating
composition, and thus the concentration of the insecticide
present on the surface of the coat is low, thereby failing to
sufficiently exhibit insecticidal effects of the insecticide.
Furthermore, when an insecticide is mixed with a coating
composition, the coating composition after application to the
surface of a substrate is usually subjected to heat-drying at
a temperature of about 100 to 150 C, whereby the insecticide
may be denatured and deteriorated by the heat-drying.
In the constitution in which silica gel particles having
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a liquid insecticide adsorbed thereon are fixed to the surface
of a substrate via an adhesive layer, the silica gel particles
are liable to be peeled off from the adhesive layer, . and thus
it is difficult to provide lasting insecticidal effect.
SUMMARY OF THE INVENTION
[0005]
In order to solve the above problems, the present invention
provides an insect proof board obtained by applying, to the
surface of a coat on a substrate applied with coating, an
insecticidal treatment liquid which contains an insecticide in
an aqueous dispersion of colloidal silica.
Usually, an insecticidal treatment liquid is prepared by
adding an insecticide to a dispersion of colloidal silica in
a mixed solvent of water and an alcohol. In this case, it is
desirable to add a surfactant as a dispersant to the dispersion
of colloidal silica in a mixed solvent of water and an alcohol.
[Effect of the Invention]
[0006]
[Mode of Action]
Since the insecticidal treatment liquid of the present
invention is a treatment liquid in which an insecticide is added
to an aqueous dispersion of colloidal silica and does not contain
a coating composition which contains a resin as a main component,
the insecticide is not diluted with the resin but is firmly fixed
to the microscopic concavo-convex surface of the colloidal
silica, and the colloidal silica is fixed to the coat on the
surface of a substrate via hydrogen bonding.
[0007]
[Effect]
Accordingly, in the present invention, an insecticide is
present at a high concentration on the surface of a coat on the
substrate via colloidal silica used as a medium, and thus
insecticidal effect of the insecticide is effectively exhibited
and a board having a significant insecticidal effect is
obtainable even if the insecticide is used in an small amount.
In addition, since the insecticide is firmly fixed to the coated
surface via colloidal silica used as a medium, lasting
insecticidal effect can be obtained.
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DETAILED DESCRIPTION OF THE INVENTION
[0008]
The invention will be explained below in detail..
[Substrate]
The substrate to be applied in the present invention
includes cement boards (wood fiber cement boards) incorporated
with wood reinforcements such as wood flakes, woody pulp, wood
fiber or the like, cement extrUsion-molded boards, pulp cement
boards, plaster boards, calcium silicate boards, magnesium
carbonate boards, plywoods, hardboards, medium density fiber
boards, iron plates, metal building boards and the like.
[0009]
Coating is applied to the surface of the substrate. Usually,
as the coating, multi-ply coating including under coating,
intermediate coating, top coating and clear coating is applied.
It is desirable to use an aqueous emulsion-type coating
composition such as a coating composition of an aqueous emulsion
of acrylic resin or aqueous emulsion of silicone-acrylic resin
for the under coating, intermediate coating, top coating and
clear coating. However, a solution-type coating composition
such as a clear solution type coating composition of an acrylic
resin may be used, and combination of the aqueous emulsion-type
coating composition and the solution-type coating composition
may be used.
[0010]
[Insecticidal treatment liquid]
The colloidal silica used in the insecticidal treatment
liquid of the present invention is such a substance that about
primary fine particles each having a particle diameter of
5 to 10 nm have associated to form a secondary fine particle
and microscopic concavo-convex pattern is formed on the surface
thereof. The colloidal silica may contain slight amounts of
other components such as aluminum oxide in addition to silicon
oxide.
[0011]
It is desirable in the present invention to add an alcohol
to water used as a dispersion medium of the colloidal silica.
The alcohol used in the present invention is desirably a
water-soluble alcohol such as methanol, ethanol or isopropanol.
The alcohol decreases the surface tension of the insecticidal
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treatment liquid of the present invention, and increases the
affinity of the insecticidal treatment liquid to the underlying
coat to enhance wettability of the insecticidal treatment
liquid.
[0012]
It is desirable to add a surfactant as a dispersant to the
insecticidal treatment liquid of the present invention. As the
surfactant may be used any of usual anionic, nonionic and
cationic surfactants. Examples of the anionic surfactant
include higher alcohol sulfates (Na salts or amine salts),
alkylaryl sulfonates (Na salts or amine salts),
alkylnaphthalene sulfonic acid salts (Na salts or amine salts),
alkylnaphthalene sulfonate condensates, alkyl phosphates,
dialkyl sulfosuccinates, rosin soaps, and fatty acid salts (Na
salts or amine salts). Examples of the nonionic surfactant
include polyoxyethylene alkyl ethers, polyoxyethylene alkyl
phenol ethers, polyoxyethylene alkyl esters, polyoxyethylene
alkyl amines, polyoxyethylene alkylol amines, polyoxyethylene
alkyl amides, sorbitan alkyl esters, and polyoxyethylene
sorbitan alkyl esters. Examples of the cationic surfactant
include octadecyl amine acetate, acetates of imidazoline
derivatives, polyalkylene polyamine derivatives and their
salts, octadecyltrimethyl ammonium chloride,
trimethylaminoethylalkyl amide halogenides, alkyl pyridinium
sulfates, and alkyltrimethyl ammonium halogenides. A mixture
of two or more of the surfactants may be used. These examples
do not restrict the invention.
The surfactant, together with the alcohol, lowers the
surface tension of the insecticidal treatment liquid of the
present invention, favorably disperses the colloidal silica in
the insecticidal treatment liquid, and increases the affinity
of the insecticidal treatment liquid to the underlying coat.
[0013]
The insecticidal treatment liquid of the present invention
usually contains 0.1 to 2.0% by mass of the colloidal silica,
2 to 10% by mass of the alcohol, 0. 01 to 0. 25 o by mass of the
surfactant, and a balance amount of water.
If the alcohol is contained in an amount less than 21 by
mass, the wettability of the insecticidal treatment liquid is
deteriorated, whereas if it is contained in an amount more than
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1015 by mass, volatility of the solvent increases to adversely
affect the coating operation. If the surfactant is contained
in an amount less than 0. 01 % by mass, surface tension-.lowering
effect and colloidal silica-dispersing effect become
unremarkable, whereas if it is contained in an amount more than
0.25% by mass, the film formed by the insecticidal treatment
is adversely affected in terms of strength, water resistance,
durability and the like. Thus, it is desirable that the
insecticidal treatment liquid has a surface tension not more
than 20 dyne/cm at 250C
[0014]
The insecticide to be added to the insecticidal treatment
liquid is desirably selected from pyrethroid compounds in view
of safety to the human body. Examples of the pyrethroid
compounds include permethrin, allethrin, tralomethrin,
silafluofen, ethofenprox, phenothrin and the like.
The insecticide is added in an amount of usually about 0.01
to 5% by mass of the insecticidal treatment liquid.
[0015]
[Application of Insecticidal Treatment Liquid]
After coating the substrate, the coat is usually dried by
heating to 100 to 150 C in the final drying process. After
drying the coat by heating, the substrate is allowed to cool
at normal temperature. Application of the insecticidal
treatment liquid is effected when the temperature of the coat
lowered to desirably not higher than 80 C, more desirably not
higher than 70 C . At a temperature not higher than such
temperature, there will not be danger of denaturation by heat
of the insecticide. Although the insecticidal treatment liquid
is usually applied by spray coating, well known application
methods such as coater coating and roll coating may be used.
[0016]
The amount of application is not restricted, but is usually
such an amount as to give an insecticidal layer in a range of
approximately 30 to 80 nm in thickness obtained by applying the
insecticidal treatment liquid and then drying.
[0017]
In the insecticidal treatment liquid, plural primary
particles of the colloidal silica are associated and
agglomerated to form a secondary particle and thus microscopic
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concavo-convex pattern is forme.d on the surface of the particles
as described in the above. Therefore, the insecticide is
captured by and adsorbed on the microscopic concavo-convex
surface of the colloidal silica. It is considered that the
colloidal silica which has captured and absorbed the insecticide
is fixed to the surface of the coat (clear coat) on the substrate
via hydrogen bonding.
[0018]
In the following, examples are illustrated to explain the
present invention more specifically.
The following insecticidal treatment liquids 1 and 2 were
prepared.
insecticidal insecticidal
treatment treatment
liquid 1 liquid 2
Colloidal silica
(secondary particle
Size:5,um) 2% by mass 2% by mass
Insecticide
(permethrin) 0.2% by mass 0.02% by mass
Ethanol 4% by mass 4% by mass
Surfactant* 0.02% by mass 0.02% by mass
Balance water water
*Polyothyethylenealkyl phenol ether
The surface of a wood fiber cement board substrate was
subjected to under coating, intermediate coating and top coating
with a coating composition of an aqueous emulsion of acrylic
resin and to clear coating with an acrylic resin solution-type
coating composition, and the substrate was dried by heating to
100 to 110 C in a heating furnace for 20 minutes.
[0019]
After drying by heating, the coated substrate was taken out
from the heating furnace and allowed to cool at room temperature.
When the temperature of the surface of the clear coat lowered
to 65 C, insecticidal treatment liquids 1 or 2 was applied
thereto by spraying. Then the substrate was left to stand at
normal temperature to dry the coat of the insecticidal treatment
liquid by the remaining heat of the clear coat. Thus, an
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insecticidal layer of 50 nm thick was formed to give sample 1
(insecticidal treatment liquid 1) and sample 2 (insecticidal
treatment liquid 2).
[0020]
As comparisons, the following comparative samples were
prepared: comparative sample 1 in which an insecticidal
treatment liquids was not applied to the coated substrate
(untreated sample); comparative sample 2 in which the substrate
was coated with a clear coating composition containing 0.216 by
mass of permethrin; comparative sample 3 in which permethrin
was directly applied to the surface of the coated substrate;
and comparative sample 4 in which insecticidal treatment liquid
1 was applied to the coated substrate similarly to sample 1 when
the temperature of the surface of the coat was 80 C.
[0021]
Sustention of harmful insect-avoiding effect was evaluated
on samples 1-2 and comparative samples 1-4.
Method of evaluation was pursuant to the test method
according to Japan Environmental Sanitation Center.
The harmful insect-avoiding effect of each sample was
measured immediately after application and drying of an
insecticidal treatment liquid, after leaving the substrate
outside for 40 days and after leaving the substrate outside for
6 months. The experiment commenced on May 1, 2004 and ended
6 moths after therefrom, i.e. on November 1, 2004.
The results of the avoidance rate thus obtained are shown
in Table 1.
[0022]
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[Table 1]
Avoidance rate (%)
Immediately After 40 days After. 6 months
af ter
application
Sample 1 96.3 87.4 76.2
Sample 2 95.6 86.6 74.3
Comparative 0 0 0
Sample 1
Comparative 97.9 88.6 68.4
Sample 2
Comparative 100 87.4 61.4
Sample 3
Comparative 89.7 81.2 71.1
Sample 4
[0023]
The avoidance rate (%) was calculated according, to the
following equation 1:
[Equation 1]
Avoidance rate (o)
=(1-number of insects in a tested sample/number of insects
in a control sample*)
*control sample: comparative sample 1
[0024]
Referring to Table 1, it was confirmed that there was no
much difference in avoidance rate between samples 1 and 2, and
that good insecticidal effect was sustained even after 6 months
in both samples. Thus, it was confirmed that there is not much
correlation between the amount of an insecticide and
insecticidal effect.
With regard to comparative sample 2 in which an insecticide
was added to a coating composition, insecticidal effect largely
decreased after 6 months. With regard to comparative sample
3 in which an insecticide was directly applied, insecticidal
effect more largely decreased after 6 months. With regard to
comparative sample 4 in which insecticidal treatment liquid 1
was applied when the temperature of the surface of the coat was
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80 C , the insecticide denatured by the heat and thus the
insecticidal effect thereof was lower than that of sample 1.
[Industrial Applicability]
[0025]
The present invention can provide boards having lasting and
effective insecticidal effect, and thus is industrially
applicable.
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