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Патент USA US2408979

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Patented Oct. 8, 1946
2,408,978
UNITED STATES PATENT ‘OFFICE’?
Bror Olof Hager, Stockholm, Sweden, assignor to
Boliclensv Gruvaktiebolag, Stockholm, Sweden, a.
joint-stock company limited of Sweden
'
No Drawing. ‘ Application February 3, 1943, Se.
rial No. 474,627. In Sweden January 13, 1941
9‘Claims. (Cl.167——38.5)
1
2
Among the substances which, especially lately,
have come into use as preservatives forwood
and other organic materials are salts ‘of arsenic
acid and hydro?uoric acid. Such salts are very
e?ective against WOOd destroyers. In applying
Parts
N azCrzOmZHzO ________________________ __ 6-15
Ala (S04) 3.181-120 _____________________ __>_ 0.25
them, efforts have been made to precipitate these
znsolnnzo
salts in the material in a di?icultly soluble form
.
0-25
H3AsO4.¥/2H2O _______________________ __‘__' 5-20
methods have given successful results with ar
senic acid, while hydro?uoric acid has not [been 10
su?iciently ?xed, but has been leached out of
,
~
NazHAsOn'lI-IzO _______________________ __ 0-20
in order to prevent their leaching out. Certain
the wood.
.
composition of suitable preservatives accordingto
the present invention.
NaF
'
'1-10
Ca(NO3)2.4H2O 0r Mg-SO4.7H2O _________ __ 5-30
~ The proportions must not be varied arbitrarily
within the above limits: The preservatives must
contain 1-—20 parts of arsenic pentoxide (AS205)
vision of wood preservatives, containing both
arsenic acid and hydro?uoric acid and in which 15 to 1 part of ?uorine (F) and 2-5 parts of arsenic
pentoxide to 1 part of chromium (Cr). The
both the arsenic and the hydro?uoric acids are
preservative must moreover contain sufiicient
precipitated in the material in a di?icultly sol
uble form.
chromium compounds and metal salts for the
effective ?xation of both the arsenic and the
The preservatives according to the present
invention consist of acid solutions or pastes con 20 ?uorine in form of di?icultly soluble compounds
and the acidity of the preservative must be su?i
taining (a) arsenic acid and/or alkali metal
cient to keep the salts dissolved in water. In
arsenate, (b) hydro?uoric acid and/or alkali
practice, impregnating solutions are used in
metal ?uoride, and (c) bichromate and/or chro
which the arsenic pentoxide and ?uorine con
mate and/or chromic acid and, in addition, either
(1) salts of one or more metals which are capable 25 tents are about 1 per cent by weight of the
The object of the present invention is the pro
of forming both di?icultly soluble arsenates and
dif?cultly soluble ?uorides, or (2) salts of two
or more metals of which one or more are capable
solution.
The following is given as an example of a pre
servative composed according to the present in
vention.
of forming only di?icultly soluble arsenates and
Per cent
the other or others are capable of forming only 30 Na2Cr20'L2H2O __________________________ __ 14
dil?cultly soluble ?uorides. For this purpose,
A12 (S04),3.18H2O __________________ __— _____ __ 16
soluble salts of the metals Ca, Mg, Zn or A1
are preferred.
When such a preservative has been introduced
Na2HAsO4.7H2O _________________________ __ 15
HsAsO4.%H2O __________________________ __ 18
into the wood it is supposed that the following 35 NaF
reactions take place. Certain substances in the
Ca(NO3)2.4HzO
wood will reduce the hexavalent chromium of
the chromium compound to a tervalent form,
causing precipitation of dii?cultly soluble chro
7
or MgSO4.7H2O ___________ __ 213
100
Having thus described my invention I declare '
mium arsenates. These reactions reduce the 40 that what I claim is:
acidity of‘the preservative; other arsenates and
l. A wood preservative composition character
?uorides di?icultly soluble in water which are
ized in that it contains (a) an arsenic compound
present or produced in the preservative will con
selected from the class consisting of arsenic acid
sequently also be precipitated.
and alkali metal arsenates, (b) a ?uorine com
When elaborating the present preservatives it
pound selected from the class consisting of hy
was found that zinc and aluminium salts are the
dro?uoric acid and alkali metal ?uorides, (c) a
chromium compound selected from the class con
most suitable metal salts for ?xing the arsenic
sisting of chromic acid, alkali metal bichromates
acid, and that the presence of both these metal
salts in the preservatives will facilitate the dis 50 and alkali metal chromates, and (d) at least one
water-soluble salt of at least one of the metals
solution of the salt mixture and improve the
selected from the class consisting of Ca, Mg, Zn
durability of the solution. For ?xing the hydro
and Al; said composition being further charac- _
?uoric acid calcium and magnesium salts were
terized in that, upon treatment of wood, both
found most suitable.
The following schedule gives the limits for the 55 di?icultly soluble arsenates and di?icultly soluble
?uorides are formed in the wood in situ.
2,408,978
4
5. A wood preservative according to claim 1
characterized by containing 1-20 parts of arsenic
pentoxide (AS205) to 1 part of ?uorine (F).
6. A wood preservative according to claim 1,
characterized by containing 2-5 parts of arsenic
pentoxide (AS205) to 1 part of chromium (Cr).
v
2. A wood preservative composition character
ized in that it contains (a) an arsenic compound
selected from the class consisting of arsenic acid
and alkali metal arsenates, (b) a ?uorine com
pound selected from the class consisting of hy
dro?uoric acid and alkali metal ?uorides, (c) a
‘_'_I. A wood preservative- characterized by the
chromium compound selected from the class con
following composition:
sisting of chromic acid, alkali metal bichromates
and alkali metal chromates, (d) a water-soluble
'
'
' '
-
Parts
salt or a metal selected from the class consisting
of Ca and Mg, and (e) a water-soluble salt of a
metal selected from the class consisting of Zn
Na2Cl‘20'z.2H2O ________________________ __ 6-15
A12(SO4)3.18H2O _______________________ -._ 0-25
and A1; said composition being further charac-_
NazHASO4.7H2O _______________________ __ 0-20
ZnSO4.7H2O ____ -n _____________________ .._ 0-25
I-I:iAsO4.1/_:HzO__.._v _____________________ .._ 5-20
terized. in that, upon treatment of wood, both
di?icultly soluble arsenates and dif?cultly soluble
_
3. A wood preservative characterized by the.
following composition:
20
'
A12(SO4) 3.18H2O _____________________ ._.-.__' 0-25
ZHSO4.7H2O ______________ -.4 ____ __-__.-____;. 0-25
NarHAsOa'IHzO _______________________ .._ 0—20
H3ASO4. 1/2H2O _________________________ __ 5-20
NBF _________________ -.i ______________ __'__ 1-10
25
CB,(NO3)2.4H2O ______________________ _;.__ 5-30
'4. A wood preservative characterized by hav
ing substantially the following composition:
Per cent
NaaCnOmZHzO _________________________ __
14
A1z(SO4) 3.181120 ______ _.-_ ________________ __
16
ZnSO4.'7I-I2O ______ __' ____________________ __
'7
N a2HASO4.7I-I2O ________________________ __
H3ASO4. 1/2H2O __________________________ .._
15
18
--_..-
rI
Ca (N03) 2.4H2O _________________ _-_ ______ __
23
____
100
30
'
Per cent
Na2Ci‘2O7.2H2O _________________ .._' ______ _ _
14
A1a(SO4) 3.181120 ________________________ __
16
ZnSO-r?I-IzO ____________________________ .._
'7
Na2HAsO4.7H2O ________________________ .. ..
15
H3ASO4.1/2H2O __________________________ _ ..
18
NaF __..
NaF
1-10
,8. A wood preservative characterized by having
substantially the following composition:
Parts
N a2Cr2O'1.2I-I2O ________________________ _ _ 6-15
»
_
MgSO4.7H2O____, ______________________ __ 5-30
?uorides are formed in the ‘wood in situ.
i
NaF _
_ --_
‘
__
7
MgSO4.7H2O ___________________________ __
23
100
9. A wood preservative according to claim 2,
characterized by an ASaOs/F ratio of 1 to 20v parts
of the former to 1 part of the latter, and by an
ASzOs/Cr ratio of 2 to 5 parts of the former to 1
part of the latter.
BROR OLOF HAGER. ‘
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