Note: Descriptions are shown in the official language in which they were submitted.
CA 02234130 1998-04-01
Alumina Wood ~odification-Decay, Stain, and Termite Protection
The present
invention relates to a method for chemically modifying wood
with reactive ionic alumina derived from sodium aluminate or
p~tassium aluminate, the decay and stain resistance which
results, and t]he termite resistance noted when copper complexes
are added to the wood modifying agents.
Background of the Invention
Wood is commonly protected from decay and stains by treating
with toxic chemicals which are water insoluble or become water
insoluble in the wood. These toxic chemicals represent hazards
to humans and the environment. Protecting wood by chemical
modification of the wood cellulose with substances common in
the environment represents an ideal solution to the problems
posed by fungicidal wood treating chemicals. Copper is one of
the more permanent, and least hazardous wood termite inhibitors.
Cellulose modification is discussed with clarity by Dr.
R. G. Siu in Microbial Decomposition of Cellulose. Dr. Siu
discusses the advantages of protecting cellulose from decay
by modification rather than using toxic substances for
protection. The requirements he outlines for an ideal
modification method are mostly met by sodium and potassium
aluminates. Wood modification according to the teaching of Dr.
Siu has not become a commercial reality. It is believed the
modification treatments attempted did not fix well.
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It is one object of my invention to protect wood from decay
and from many undesirable wood stains without the use of anionic
fungicidal chemicals. These anionic chemicals may react with
the aluminates and render them unsuitable for cellulose
modification. The aluminum salts formed may protect the wood;
but that protection is from the anionic portion of the salt.
It is possible to use the aluminates in stoichiometric
excess of the added anions, and thus achieve wood modification
in the presence of anionic fungicides. This approach leads to
r~dundant protection from decay and stains. It is also possible
to use fun~icidal anions at less than fungicidal levels with
the aluminates of my invention in an effort to circumvent my
claims. My invention precludes fungicidally effective amounts
of certain anions with the aluminates.
The sodium aluminate and potassium aluminate used in the
practice of my invention have a long history of use in paper
making, in water purification, and in other commercial processes.
In none of these applications do the aluminates exhibit
fungicidal activity. The alumina from the aluminates which modify
the cellulose occurs commonly in the environment, and certainly
is no fungicide. In fact aluminum is the third most common
element found in the environment.
It is known that certain aluminum or alumina salts, like
salts of calcium and potassium, have fungicidal activity.
Aluminum salts of N-nitrosocyclohexylhydroxylamine compounds
and aluminum salts of certain phosphonic acids are known to
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be fungicides. My invention does not encompass treating wood
with aluminum salts whether or not those salts inhibit fungi.
Those skilled in the art will recognize that references
in the literature to compositions prepared by adding sodium
aluminate or potassium aluminate with acids or salts does not
mean these Eormulations contain sodium aluminate or potassium
aluminate once they are mixed together. The aluminates are low
cost sources of water soluble aluminum often used for the
preparation of aluminum salts. They offer the formulation chemist
an opportunity to prepare creative compositions containing
aluminum compounds.
When acids or acidic salts are mixed with aluminates, the
salts of aluminum and acid anions are formed. When alkaline
salts and aluminates are mixed together, the aluminum salts
of the alkal:ine salt anions are formed providing those aluminum
salts are less water soluble or less ionized than the alkaline
salts. When phosphonic acids are mixed with aluminates, aluminum
phosphonate salts are formed. When water soluble salts of N-
nitrosocyclohexylhydroxylamine are mixed with aluminates, the
aluminum salts of this fungicidal anion are formed. These salts,
like most other insoluble aluminum salts, are soluble in
solutions containing alkali hydroxides.
While additives, which convert reactive alumina to aluminum
salts, can not be used in the practice of my invention, other
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additives may be used if they do not change the ionic nature
of the alumina. Treated wood leaching tests can indicate whether
anionic additives form aluminum salts when used with aluminates.
If the anion leaches little, it has formed an insoluble aluminum
salt. If it: leaches much, there is no legitimate reason for
its presence in a system which requires permanence.
Wood is treated in the practice of my invention by
contacting it with concentrations of sodium aluminate, potassium
aluminate, or a combination of these. The treating concentrations
may also contain acceptable additives. The wood may be contacted
by any suitable means such as brushing, spraying, dipping,
soaking, pressure treating, or by applying a bandage. Contacting
methods which result in greater aluminate concentration
retentions require less aluminate in the treating concentration
for effective wood modification. I have found at least a 0.5%
aluminate concentration is required for consistently effective
protection from decay and staining even when treating methods
are used which result in the highest retentions. The treating
concentration best for a specific treating application can only
be determined by extensive testing of treated wood. A suitable
concentration for one species of wood may not be suitable for
another species.
Additives especially useful in the alumina wood modification
treatments are those capable of protecting the wood from insect
attack. I have found that certain cationic copper complexes
produced by reacting copper or copper compounds with ammonia
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or amines are useful additives which provide insect protection
to treated wood, and do not negate the decay protection afforded
by alumina wood modification. The copper is cationic and can
not react with cationic alumina. Several cationic copper
complexes are available commercially.
Summary of the Invention
The present invention comprises a method for chemically
modifying wood with reactive alumina, which consists of
contacting said wood with aluminates chosen from the group
consisting of sodium aluminate and potassium aluminate in
concentrations greater than 0.5%, without fungicidally effective
amounts of anions from N-nitrosocyclohexylhydroxylamine salts.-
The current invention additionally comprises a method for
protecting wood from decay and staining, which consists of
contacting said wood with reactive alumina derived from
aluminates, chosen from the group consisting of sodium aluminate
and potassium aluminate in concentrations greater than 0.5%,
without fungicidally effective amounts of anions from
N-nitrosocyclohexylhydroxylamine salts. My invention further
comprises a method for protecting wood from decay and termites,
which consists of contacting said wood with reactive alumina,
derived from aluminates, chosen from the group consisting of
sodium aluminate and potassium aluminate, in concentrations
greater than 0.5%, with ethanolamine copper complexes added,
but without fungicidally effective amounts of anions from
N-nitrosocyclohexylhydroxylamine salts.
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Detailed Description of the Invention
The following examples illustrate contacting wood with
aluminate concentrations so as to achieve alumina wood
modification, contacting wood with aluminate concentrations
plus ethanolamine copper complexes so as to achieve alumina
wood modification and copper insecticidal protection, and the
performance of the treated wood when it was exposed in Tate
County, Mississippi, U.S.A.
Example 1
A fresh cut and peeled pine pole was wrapped on one end
with a towel which had been spread with a one-fourth inch
thickness of 95% sodium aluminate powder. After one week, the
towel was removed and the pole exposed in the weather for six
weeks. After this exposure, the pole was free of stain in the
treated area, but badly discolored where it was not contacted
by the aluminate. After another year of exposure above ground,
the untreated end of the pole was infected with decay while
the treated end was bright and free of decay.
Example 2
Seasoned pine boards, free of stain, were full cell treated
with a 0.5% concentration of sodium aluminate in water. These,
and untreated boards, were placed outdoors on the ground for
six weeks. At the end of this period only the treated boards
were free of stain.
Example 3
Seasonecl pine boards were full cell treated with a 5%
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concentration of sodium aluminate in water. These, and untreated
boards, were placed in a forest area, and covered with two inches
of soil. After a period of two years the untreated boards were
destroyed by decay and insects. After the same period, the
treated boards were attacked by insects; but they were not
attacked by decay.
Example 4
A fresh cut and peeled elm pole, which contained a heavy
concentration of sugars near the surface, was treated on one
end, with a 10% concentration of sodium aluminate in water,
by brush coat. This treating was performed during the middle
of the summer when mold growth is most prolific. This pole was-
exposed where mold spores were regularly stirred by grass mowing.
At the end of two weeks mold growth was prolific on both ends.
The pole was allowed to remain exposed above ground for another
year. At the end of the year, the untreated end was decayed
on the surface while the treated end was free of decay. The
aluminate treatment modified the cellulose and it was not used
by decay organisms. The aluminate did not modify the wood sugars,
and they were available to support mold growth.
Example 5
Western red cedar siding was removed from a house where
it had darkened over a period of years. One end of each board
was brush coated with a 10% solution of sodium aluminate in
water. The center portion was left untreated while the opposite
end was brush coated with a 10% solution of sodium hydroxide
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in water. After one week of outdoor exposure, the treated ends
were both bleached, with the sodium aluminate treatment being
somewhat whiter than the sodium hydroxide treatment. After
another year of outdoor exposure, the sodium hydroxide treatment
had stained while the sodium aluminate treatment rem~;ned bright
and free of stain. The untreated center of the boards did not
change significantly during this period.
Example 6
A fresh cut and peeled hackberry pole, which contained
a heavy concentration of sugars near the surface, was treated
on one end with a 10% concentration of potassium aluminate in
water. The treating and early testing was performed as in Example
4. After two weeks, molds covered the untreated and treated
ends. After another two months of exposure, the treated end
was again brush coated with 10% potassium aluminate in water.
This bleached out the mold growth after one week of exposure~
After another year of exposure, the treated end remained free
of both molds and decay, while the untreated end was molded
and decayed.
Example 7
One end of pine boards were soaked for one week in water
solutions containing 2% sodium aluminate and 2% potassium
aluminate. The opposite end of the boards remained untreated.
The boards were exposed in a forest area where they were covered
with two inches of soil. At the end of a three year period,
the untreated ends of the boards were destroyed by decay and
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termites. At the end of the three year period the treated ends
of the boards were free of decay. They were-attacked by termites;
but the degree of attack was much less than the termite attack
on the untreated ends.
Example 8
One end of pine boards were soaked for one week in a water
solution containing 3% sodium aluminate. The center of the boards
was left untreated. The opposite ends of these boards were later
soaked for one week in a water solution containing 3% sodium
aluminate plus 0.1~ copper derived from a commercial ethanolamine
copper complex product. These boards were dried, then exposed
in a forest area under two inches of soil. At the end of a three
year period, the centers of the boards were destroyed by decay
and termites. The ends treated with 3% sodium aluminate were
free of decay, but exhibited some termite attack. The ends
treated with 3% sodium aluminate plus 0.1% copper were free
of attack by both decay and termites.
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