Note : Les descriptions sont présentées dans la langue officielle dans laquelle elles ont été soumises.
3~
FIELD OF INVENTION
The present invention relates to a composition
for wood treatment. More particularly it relates to
aqueous ammoniacal wood-treating compositions containing copper, and/or zinc, and quaternary ammonium compounds.
~ACKGROUND OF THE ~V~NTIO~/P~ T
In the treatment of wood material to render it
resistant to biological attack, i~ is common practice to
treat it with a fluid-borne treating chemical. The
treatment of the wood material usually comprises soaking
or impregnating the wood material with the fluid-borne
treating chemical. The second of these techniques which
is perhaps the most widely used one is practised in a
number of variants, eg. the full cell process, where the
pores of the wood material are partially evacuated before
impregnation in order to increase the fluid retained
therein; or the empty cell process which is similar to the
full cell process except that the preliminary step of
evacuation is omitted.
One of the more widely used impregnating
compositions is an acidic solution of chromium, copper and
arsenic. Another aqueous composition commonly used in the
impregnation of wood material, comprises an ammoniacal
solution of water-insoluble treating chemicals such as
salts comprising copper and arsenic. While these
compositions are generally satisfactory, they both contain
arsenic.
It is therefore the object of this invention to
provide an effective wood treating composition having low
mammalian toxicity.
BRIEF DESCRIPTION OF THE INVENTI0~7
The formulation of the present invention
comprises an aqueous ammoniacal solvent comprising
- 2 -
ammonium hydroxide having a wood treating composition
dissolved therein, wherein the composi~ion contains ~
quaternary ammonium compound and at least one of copper
and zinc, where the quaternary ammonium compound can be
represented by the general formula
( RlR2R3R4~ ) X
~wh~re ~l and R2 are independently chosen ~rom ~he
group consisting of alkyl groups having 1 to 3 carbon
atoms, R3 is chosen from the group consisting of alkyl
groups having 8 to 20 carbon atoms, and R4 is chosen
from the group consisting of alkyl groups having ~ to 20
carbon atoms, aryl groups and aryl-substituted alkyl
groups where the alkyl groups have 1-3 carbon atoms, and
X is chosen so as to render the quaternary ammonium
compound soluble in the ammoniacal solvent. The ammonium
hydroxide concentration is 1.5-2.5 times that of the
metall~c species expressed as the metal oxide.
This invention also includes a method of
preserving wood which comprises impregnating a wood
substrate with a wood preservative formulation comprising
an aqueous ammoniacal solvent comprising ammonium
hydroxide having a wood treating composition dissolved
therein; where said composition contains a quaternary
ammonium compound and a metallic cation consisting
essentially of at least one of copper and zinc, where said
quaternary am~onium compound can be represented by the
general formula
~ RlR2R3R4~ ) X
where Rl and R2 are independently chosen from the
group consisting of alkyl groups having 1 to 3 carbon
atoms, R3 is chosen from the group consisting of alkyl
groups having 8 to 20 carbon atoms, and R4 is chosen
from the group consisting of alkyl groups having 8 to 20
carbon atoms, aryl groups and aryl-substituted alkyl
groups where said substituted alkyl groups have 1 to 3
carbon atoms and X is chosen 80 as to render said
-- 3 --
quaternary ammonium compound soluble in said ammoniacal
solvent where said quaternary ammonium compound and said
metallic cation are present in 6aid formulation in
biocidally effective amounts, and where the ratio of ^aid
quaternary ammonium compound to said metallic cation
ranges from a~out .003 to about 30, and the invention
extends also to a wood product obtained by the foregoing
method.
DETAILED DESCRIPTION OF THE IMVE~TION
Accordingly, the present invention relates to a
formulation for the treatment of wood material having
acceptable preservative ability and additionally at least
partially obviating the problems of the prior art
formulations.
As noted above, the formulation comprises an
aqueous ammoniacal solvent having a wood treating
composition dissolved therein. This composition will
comprise a quaternary ammonium compound, and at least one
of copper and zinc. The quaternary ammonium compounds
~ contemplated for use in this composition can be
represented.by the general formula
( RlR2R3R4N ) X
where Rl and R2 are independently chosen from the
group consisting of alkyl groups having 1 to 3 carbon
atoms, R3 is chosen from the group consisting of alkyl
groups having 8 to 20 carbon atoms, and R4 is chosen
from the group consisting of alkyl groups having 8 to 20
carbon atoms, aryl groups and aryl-substituted alkyl
groups, where the alkyl groups have 1-3 carbon atoms. ~ne
anion X will be chosen so as to solubilize the
quaternary ammonium compound and will preferably be chosen
from the group consisting of hydroxide, chloride, bromide,
nitrate, bisulfate, acetate, bicarbonate and carbonate
formate, borate and fatty acid salts. Quaternary ammonium
compounds preferred for use in this composition are
alkylbenzyldimethylammonium chloride where the alkyl can
- 4 -
represent C12 - C16 alkyl groups, and
dialkyldimethylammonium chloride, where the alkyl can
represent C8 - C12 alkyl groups. The aryl-substituted
alkyl group will preferably ~e the benzyl group.
The formulation will be prepared by dissolving
metallic copper and/or zinc in the aqueous ammonium
hydroxide or by dissolving a sui~able copper or zinc salt
such as cuprGus oxide, cupric hydroxide, æinc oxide or
cupric carbonate in ammonium hydroxide ~ontaining a
suitable amount of anion such as ~luoride, acetate.
carbonate, formate or borate which is added to dissolve
the metal in adequate concen~ration. When metallic
copper, zinc or cuprous oxide are used, an oxidation of
the solution will be required. This can be done by
sparging the solution with air; and in this case, the
quaternary ammonium compound should be added after its
termination in order to avoid excessive foaming.
Quaternary ammonium compounds are usually supplied in the
form of a concentrate, at about a 50-80% (by weight)
concentration of the compound, and will normally be added
as the undiluted concentrate.
Typically, in such compositions, the
concentration of the metallic cation in the solution viz.
that of copper and/or zinc will lie in the range of
25 Q.5-lS~, the quaternary ammonium compound from 0.05-15% of
the formulation and the ammonia which will be present in
sufficient quantity to solubili~e the metallic cations can
range from 1-29~ by weight of the solution. The ammonia
concentration should be 1.5-2.5 times that of the metallic
species expressed as the metal oxide.
Wood material can be treated with this
composition in the usual manner (eg. by soaking,
impregnating, etc.)~ The composition impregnates wood
material relatively easily and following impregnation is
highly leach-resistant. Since the quaternary ammonium
compound demonstrates an affinity ~or the wood material
and is preferentially absorbe~ thereby, low concen~rations
may result in inadequate penetration and accordingly it
may be necessary to use rela~ively high concentrations of
the quaternary ammonium compound if deeper penetration is
desired. The empty cel~ treatment may be used in such
cases in order to remove exceg6 quaternary ammonium
co~pound
The composition can be modified in a number of
ways which will be evident to tho~e skilled in ths art;
eg. fatty acids for water repellancy or colouring agents
can be added to the composition.
The present invention provides an aqueous
ammoniacal arsenic-free composition which finds
application in wood preservation. Despite its low
mammalian toxicity, the formulation has effective biocidal
properties as demonstrated by the existence of threshold
retention levels for various fungi which are surprisingly
less than corresponding values for a conventional
arsenic-containing formulation. The significant decrease
~ in the aggregate threshold retention of the preservative,
as compared to ths threshold retention levels of the
individual components when small amounts of quaternary
ammonium compound are added to the ammoniacal copper
containing solution strongly su~gests the possibility of
synergism between the two components.
The following examples will serve to illustrate
the invention.
Example 1
The formulation prepared according to the present
invention containing copper added as copper carbonate,
alkylbenzyldimethylammonium chloride dissolved in a 3%
ammonium hydroxide solution, was impregnated into 3/4" x
3/4" x 3/4" blocks of red pine ~apwood material at various
levels of preservative retention. The blocks were then
subjected to leaching with water by soaking them in 50 ml.
of water per block, and changing the water every day for
- 6 ~ 5~6
14 da~s. The blocks were air dried to constant weight in
a chamber held at 70% R.H. The conditioned blocks were
weighed and placed in soil block test jars containing
innocula of "Lenzites trabea", "Poria monticola" and
"Lentinus lepideus" fungi, in accordance with AWPA soil
block test procedur~ M10-77. ~ter 1~ ~eek~, *he ~oil
blocks were reweighed, and the minimum level of
preservative retention required to result in weight losses
of less than 2~ for each species of fungus was
determined. These threshold retention levels (in pounds
per cubic foot), for various fungi are summarized in Table
A below.
This experimental procedure was carried out with
two alternative formulations of the present invention
lS containing different ratios of copper to the quaternary
ammonium compound. For the purposes of comparison, this
procedure was repeated using a conventional aqueous
ammoniacal solution of copper arsenate, and the
corresponding threshold retention values obtained.
An examination of Table A will yield the
observation that smaller threshold retentions of the
present invention formulations are required to obtain the
same level of protection when compared to the conventional
formulation.
7. ~2~L5~
TABLE A
CONVENTIONAL ORGANISM THRESHOLV RETENTION
FORMULATIO~ LEVELS
(pounds per cubic foot)
Ammoniacal Copper Arsenate Lenzites trabea 0009
Poria monticola 0.14
PRESE~T INVENTIO~
FORMULATION
CuO: Quaternary: 6:1 Lenzites trabea 0.07
Poria monticola 0.09
Lentinus lepideus 0.035
CuO: Quaternary: 2:1 Lenzites trabea 0.07
Poria monticola 0.19
Lentinus lepideus 0.04
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- 8 - ~2~
Example 2
This example compares the preser~ative properties
of the treating solution with the preservative properties
of its constituent treating chemicals by comparing the
respective threshold retention levels. Procedurally, the
experiments in this example are essentially the same as
those in the preceding examples. 3/4" x 3/4" x 3/4"
blocks of red pine sapwood material were impre~nated with
aqueous ammoniacal solutions of copper carbonate only, the
quaternary ammonium compound ABDA only, and the
preservative composition having a ratio of copper (as CuO)
to quaternary ammonium compound of 4:1. Preservative
solutions with copper to quaternary ammonium compound
ratios of 6:1 and 2:1 were also impregnated into wood
blocks. The blocks were then leached and dried, and
placed in soil block test jars which contained innocula of
"Lenzites trabea", "Poria monticola" and "Lentinus
lepideus". This permitted a determination of the
threshold retention levels which are summarized in Table B
below.
An examination of the entries in the table below
indicates the efficacy of the formulation taught herein.
In each of the cases, the threshold retention
concentration of the present invention formulation was at
most equal to (and often less than) the corresponding
values for the individual constituents. More
particularly, in the case of "Poria monticola", which is
tolerant to both copper (threshold retention of 0.5
p.c.f.) and ABDA (threshold retention of 0.2 - 0.~
p.c.f.); the use of the present for~ulation results in a
decrease in the retention levels of copper to 0.06 - 0.09
p.c.f. and ABDA to 0.02 - 0.10 p.c.f.; while the total
threshold retention level lies in the range 0.09 - 0.19
p.c.f., (depending on the CuO:ABDA ratio) indicating an
interaction between the two components.
9 ~ 06
TABLE _
THRESHOLD RETENTIONS
(Leached Blocks)
Threshold
Retention Concentration at
(pcf CuO Threshold Retention (pcf)
Preservative Organism + ABDA) CuO ABDA
CuCO3 Lenzites trabea 0.07 0.07
Poria monticola 0.5 0.5
t*) ABDA Lenzites trabea 0.3 - O.3
Poria monticola 0.2-0.4 - 0.2-0.4
Lentinus lepideus 0.07 - 0-07
~+) ACQ 6:1 Lenzites trabea 0.07 0.05 0.02
Poria monticola 0.09 0.07 0.02
Lentinus lepideus 0.035 0.025 0.010
ACQ 4:1 Lenzites trabea 0.06 0.04 0.02
Poria monticola 0.10 0.06 0.04
Lentinus lepideus 0.016 0.010 0.006
ACQ 2:1 Lenzites trabea 0.07 0.03 0.04
Poria monticola 0.19 0.09 0.10
Lentinus lepideus 0.04 0.02 0.02
(*) ABDA - alkylbenzyldimethylammonium chloride.
[~ ACQ - composition of the present inventiont ratio indicated is
that of CuO to ABDA.
.
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- 10
Example 3
This example de~onstrate6 the desirable
impregnation characteristics of the present invention. A
2" x "2 x 22" piece of Douglas-fir sapwood was end-sealed
with epoxy resin and impregnated with a solution
containing 1.5% cupric oxide (added as basic copper
carbonate), 0.5% ~l~ylbenzyl-di~ethyl~mmonium chloride
(ABDA), and 3.0% ammonium hydroxide by applying a v~cuum
of 22" of mercury for half an hour and then applying a
pressure of 115 psi for 4 1/2 hours at 22C. The
retention achieved (CuO ~ ABDA) was 0~58 pcf. After
drying, a 2" section was cut from the center of each 22"
piece and this 2" cube was then sectioned so that the
retention gradient of the copper and ABDA could be
determined. The results for the four faces of the
cross-section were averaged and are shown in table C
below, and indicate the desirable impregnation
characteristics of the present invention.
TABLE C
PENETRATION INTO DOUGLAS FIR SAPWOOD USING
SOLUTION OF COPPER TO ABDA RATIO OF 2.4:1
¦CONCENTRATION IN WOOD (~)¦
¦ Location Cu ABDA (*~¦
0-1/8" 3.30 0076
l/8-1/4" 2.22 0.43
ll/4-3/8" 2~11 0.3
l3/8-5/8" 1.93 0.27
15/8-1" 1.93 0.20
_
(*) ABDA: Alkylbenzyldimethylammonium chloride.
Example 4
This example presents the penetration results of
the present composition into red pine sapwood. A piece of
red pine sapwood was treated ~ith a solution containing
1.5% copper oxide (added as copper carbonate), 2~ of
alkylbenzyldimethylammonium chloride (ABDA), and 3% of
a~monium hydroxide using .the ~ame tr~at~ent and-analytical
procedure as the preceding example. A retention (CuO +
ABDA) o~ 1.2 p.c.f. was obtainedO The penetration
results, which are shown in Table D below, indicate the
desirable penetration characteristics of the treating
solution.
TABLE D
PENETRATION OF RED PINE SAPWOOD WITH
A COPPER TO ABDA RATIO OF 0.6:1
¦ CONCENTRATION IN WOOD (%)¦
¦ Location Cu ABDA ~*~¦
l0-1/8" 3.66 2.76
l/8-1/4" 1.54 2.13
ll/4-1/2" 1.44 1.52
ll/2-3/4" 1.45 1.37
3/4-1" 1.75 1.74
Modifications to the above will be evident to
those skilled in the art, without departiny from the
spirit of the invention as defined in the appended claims.
