Note : Les descriptions sont présentées dans la langue officielle dans laquelle elles ont été soumises.
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Wood preservative
The present invention relates to the provision
of agents for the pressure impregnation of (solid) wood,
which are based on aqueous formulations of a copper salt,
S m~noethanol~ne and, if requ;red, further components, in
particular fungicidal salts whose action is attributabLe
to the anion, for example salts of boric acid.
To date, chromate-containing, fixing wood pre-
servatives have been employed for protecting wood which
is exposed to weathering or humidity or, as part of a
structure, ;s ;n contact with earth. These wood preserva-
t;ves are used in the form of aqueous solutions, eg. from
2 to 6~ solut;ons, depend;ng on the level of risk to
which the ;mpregnated wood is subsequently exposed~ the
treatment being carried out with the aid of large ;ndus-
trial impregnation plants (pressure ;mpregnat;ng process).
For use ;n contact with earth, the agents used
are exclusively those which conta;n not only chromate
but also copper, owing to the fact that they have to be
2Q effective against wood rot caused by fungiO A d;st;nct;on
is made between the CC type (based on copper and chromium),
the CC~ type (based on copper, chromium and boron), the
CCF type (based on copper, chromium and fluor;ne) and
the CCA type (based on copper, chrom;um and arsen;c).
2S Fixing in these wood preservatives is via the
chromate part. After ;mpregnat;on, the chromates react
with the sonstituents of the wood and are reduced to
trivalent chromium compounds; as a result, the pH in the
wood increases so that copper compounds and chromium com-
pounds are prec;p;tated ;n the wood as water-insoluble
compounds and are fixed.
However, chromates, ie. hexavalent chromium com-
pounds, constitute a considerable risk for the environment
when leakage or weather effects during the fixing process
result in these compounds being washed out, so that sur-
face water, ground water and tap water are contaminated.
The maximum concentration currently tolerated is, for
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example, 0.05 ppm. Even if the chromium in the wood is
present in trivalent form, it can, bey oxidation, be converted to
hexavalent chromium compounds, which may then be washed outoftheash;
thisgivesrisetoproblemswithregardtodisposal.
To date, chromium-free, copper-contain;ng, water-
soLuble wood preservatives for large-scale industrial
impregnation have been proposed, in which, for example,
copper arsenate and borate are converted to a water-soluble
alkaline form by complex formation with ammonia~ These
agents are fixed in the wood by evaporating the ammonia
and as a result of buffering with wood constituents (the
pH of the wood itself is about 5). Apart from the odor
nuisance, these impregnating solutions, or the concentrates,
may lose their stability through the evaporation of the
ammonia, so that the solutions are no longer suitable
for further impregnation. Furthermore, when the ammonia
content is insufficient, penetration of the preservative
into the wood is hindered.
Amines having good complexing properties, eg.
ethylenediamine, have also been recommended for wood
preservatives containing copper and fluorine, for the
protection of wood-based materials, eg. particle boards.
- These agents are mixed into the resin in highly concen-
trated form and, together with the resin, are sprayed
onto the chips. They are unsuitable for preserving solid
wood s;nce the ethylenediamine complexes are stable, even
at the p~ of the wood itself t5-6) and do not fix; they
are washed out of the wood by ~ater.
Copper is fixed only when water-insoluble organic
copper salts can form. For example, wood preservatives
which contain copper salts of N-nitrosocyclohexylhydroxyl-
amine tnew name: copper salt of N-cyclohexyldioxydiazenium
oxide, Cu-HD0) have been described. The Cu-HDO is con-
verted, via polyaminPs, eg. ethylenediamine or diethylene-
triamine, into wood preservative concentrates, which aredissolved in water in order to carry out impregnation~
They become fixed in the wood as a result of buffering
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with the aid of wood constltuents from about pH 7.5.
However, this fixing takes place so rapidly that pene-
tration of the Cu-HDO is preven-ted during pressure impreg-
nation. For example, even in the case of pine, which
can be easily impregnated, the Cu-HDO only penetrates
an outer layer of about 10 - 15 mm. Dispersing of the
preservative toward the inside falls off rapidly.
If other amines, eg. alkanolamines, in parti-
cular monoethanolamine, are used for complexing, the
Cu-HDO is completely dissolved only in highly con-
centrated solutions; dilution with water to the concen-
tration for use precipitates it once again.
We have found that the disadvantages described
above can be overcome if use is made of an agent for
solid wood preser~ation comprising a water-dilutable
formulation of a water-soluble or insoluble, inorganic
copper compound, such as copper sulfate, copper fluoro-
borate, copper hydroxide, copper borate, copper fluoride,
copper carbonate or copper oxychloride, in admixture
w it h m on oe t h an o 1 a m i ne p r e s e n t
in an amount such that when the formulation composition
is diluted with water to a wood treatment concentration
of about 1 to 5% of the non-aqueous components in the
aqueous solution, a pH of not less than 8 is established
in the resulting aqueous composition.
The water-dilutable agents contain the copper
in concentrated form, in general in an amount of from
1 to 15~ by weight, calcula-ted as the element.
Suitable concentrates contain, for example,
from 5 to 50% by weight of a copper salt, from 5 to 50%
by weight of monoethanolamine, up to 50% by weight of
a salt of a fungicidal anion and up to 5% by weight of
free alkali, the percentages summing -to 100, and, if
desired, minor amounts of other components, such as
amines, ammonia, corrosion inhibitors and, if required,
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water, the amount of which can, however, generally be
kept small and essentially facili-tates handling. However,
t~e present invention also relates to the impregnating
solutions of appropriately lower specific concentrations,
these solutions being prepared by dilution with water.
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Complexing can be carried out in the presence
of fungicidal anions, eg. borates or fluorides. Dissolv-
ing the copper compounds in the alkanolamine, in particular
monoethanolamine, if ne~essary with the addition of water,
gives highly concentrated ~ater-soluble pastes or l;quid
concentrates which, when dissolved in water, can be used
for impregnating ~ood. The pH of the aqueous impregnating
solut;ons is 8 or higher, in particular from 9 to 10 (con-
centration-dependent). ~hen impregnation is carried out
by the pressure process, the copper component penetrates
thoroughly into the ~ood. During the impregnation pro-
cess, the novel preservatives are buffered by the wood
acids present in the wood, the copper being precip;tated
;n the ~ood from abou~ pH 7. From pH 7 - 7.5, the com-
1S plex-forming power of the alkanolamines is in fact no
longer su~ficient to keep the copper in solut;on, so that
the copper is fixed. The extent to which the copper is
fixed is of the same order of magnitude as for the pre-
v;ous chromate-containing and copper-containing wood pre-
ser~ati~es, ie. not less than 85~, and on average from
~ 90 to 95~, of the copper component is fixed in the wood.Fixing is partly dependent on the additional alkanolamine
content which is required for adjusting the pH in the case
of strong acids or fungicidal anions; a certain effect in
respect of pH shift can~ however~ also be achieved by
adding~ for example, an alkali metal hydro~ide solution,
for example sufficient to produce a pH shift of up to
about 1. In g2neral, th;s measure applies to the amount
of fungicidal anions or acid radicals; it can also be
brought to the required pH, independently of complex
formation, by an alkali, ammon;a or another water-soluble
amine.
For economic reasons, -the complexing agent is
monoethanolamine. The novel wood preservatives may
3~ howeve.r also contain other alkanolamines,
eg. isopropanolamine, 1,1- or 1,2-diaminoethanol, am;no-
ethylethanolamine, diethanolamine, dimethylethanolamine,
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etc. The amount of alkanolamines added is such that it
is sufficient for complex formation with copper (1 g atom
of copper generally requires 4 mol equivalents of amine)
and, if necessary, for forming alkanolamine salts of the
fungi~idal anions additionally used (fluoride, borate
or fluoroborate) or esters, so that the aqueous impreg-
nating solution is brought to a pH of 8 or higher, prefer-
ably from 9 to 10.
To test the invention in practice, the following
procedure was adopted: the concentrates, in the amount
stated in each case (4 or 3%) were diluted with water,
and the product was used to impregnate small pine blocks.
After drying, the stated blocks were washed for 4
weeks with distilled water, the water being changed daily.
The amount of copper washed out was then determined.
EXAMPLE 1
A mixture of
33.3% by weight of CuS04.5H20,
33.3% by weight of monoethanolamine and
33.4% by weight of water
is dissolved in water in a concentration of 40 9 per
liter of water (referred to below as 4% strength solution).
Amount of copper washed out 7.5%~
EXAMPLE 2
25 ZO.OX by weight of 3Cu(OH)2.CuCl2,
40.5% by weight of monoethanolamine and
40.0Z by weight of water
(4X strength aqueous solution).
Amount of copper washed out 10.5%.
EXAMPLE 3
15.0% by weight of Cu(OH)2.CuC03,
16.0% by we;ght of monoethanolamine,
16.0Z by we;ght of aminoethylethanolamine,
25.0% of H3~03 and
35 38.0% of Hzû
t4% strength aqueous solution).
Amount washed out:
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Cu 10.5%
85.5%.
EXAMPLE 4
13.5% of Cu(OH)2,
25.0% of boric a~id,
17.5% of monoethanolamine,
17.5% of àminopropanol and
26.5% of water
(4~ strength aqueous solution).
Amount washed out:
Cu 7.7%
8 86.5%.
EXAMPLE S
50% of CU(8F4)2 solution (dissoLved in water to give
a Sû~ strength solution),
30% of monoethanolamine and
2û% of H2û
(3% strength aqueous solution, defined as above).
Amount washed out:
Cu 10.5%
F 70.0%
8 7S.û~.
EXAMPLE 6
16.5% of Cu(OH)2.CuC03,
10X of NH4HF2,
36.0% of monoethanolamine and
3.5X Of H20
~3X strength aqueous solution).
Amount washed out:
Cu 0.5%
F 78.5%.
EXAMPLE 7
15.0% of Cu(OH)2.CuC03,
30% of aminoethanolamine,
25.0% of boric ac;d and
27.0% of HzO
(4% strength aqueous solution)~
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Amount washed out:
Cu 12.5~
B 88.0%.
EXAMPLE 8
70% of copper borate paste (dispersed in water to give
a 50% strength dispersion) and
30% of monoethanolamine
(4~ strength aqueous solution).
Amount washed out:
`lO Cu 7~5%
a 85 . 0% .
EXAMPLE 9
75% of copper borate paste (dispersed in water to give
a 50% strength dispersion) and
25X of monoethanolamine
(4% strength aqueous.solution).
Amount washed out:
Cu 6.2%
B 66.1%.
COMPARATIVE EXPERIMENT 1
Chromiu~-containing salts:
1a~ Type CC8
Cu content 8.6%
Cr content 13.4~
8 content 4.4%
lb) Type CCF
Cu content 7.7%
Cr content 25.5X
F content 14.5%
30 1a) Type CC8Amount washed out, in %
Cu 8.0
Cr 2.0
. B 93.5
1b) Type CCFAmount washed out, in %
Cu 13.5
Cr 18.5
F 72.5.
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COMPARATIVE EXPERIMENT 2
(not according to the invention)
12.0% of CuO,
Z2.0% of ethylenediamine,
12.0~ of KHF2 and
54.0% of water
dissolved in water to give a 3~ strength solution.
Amount washed out:
Cu 75.5~
F 92.5~.
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