Improvements in Treating Wood and other Vegetable Fibres for Preserving, Waterproofing, and the like.
Year: 1898

page_text: Date of Application, 26th Nov., 1898-Accepted, 21st Jan., 1899
Improvements in Treating Wood and other Vegetable Fibres for
Preserving, Waterproofing, and the like.
I, FRITZ HASSELMANN, of Kurgarten, Nymphenburg, near Munich, Bavaria,
German Empire, Architect, do hereby declare the nature of this invention and in
what manner the same is to be performed, to be particularly described and ascer-
tained in and by the following statement:
-
The object of the present application is a process for the treatment of wood and
other vegetable fibres, in order to render them resistant to the action of the
atmospheric bacteria and the like, as well as against the influence of rot and fungi,
investing it at the same time with a great degree of incombustibility, while retain-
ing the natural appearance.
In the British Patent No. 25240 of the 11th September 1896, a process for the
impregnation of wood and turf is set forth, consisting essentially in treating the
wood or the like with solutions of sulphate of alumina and sulphate of iron, and
then treating them in the like manner with solutions of chloride of calcium and
caustic lime. The said process consequently consists of two consecutive baths
and has the effect that the wood so treated is increased in durability and power of
resistance, and is protected against the action of the fungi, attacks of insects and
rot, but at the same time the natural colour of the wood is more or less affected,
which may be desirable in the case of special applications (as for instance, for
cabinet making) for the purpose of obtaining certain coloured effects, but is in
general unfavourable to the applicability of the wood. A further drawback of this
otherwise satisfactory process is found to consist in the somewhat complicated and
expensive double boiling. I have now succeeded in inventing a process whereby:
1. The prepared wood retains its natural colour.
--
2. The double boiling is avoided and this without sacrificing any of the advan-
tages of the process set forth in the patent above cited.
My improvement consists in the application of potash and magnesia salts instead
of chloride of calcium and caustic lime, and in practice I prefer to make use of the
double salt of chloride of potassium and sulphate of magnesium, the product known
technically as kainit or as sylvinit. My process is carried into effect as follows:-
The wood is heated in a bath of green vitriol (consisting of a crystallized mixture
of sulphate of iron and about five to fifteen per cent. of sulphate of copper), and a
proportion of sulphate of alumina in solution of about one part to thirty. When
this bath has reached a temperature of 105° C., there is added kainit in solution
of about one part to thirty, and in quantity corresponding to the application and
the kind of the wood. The boiling is then conducted at from 135° to 140° C., and
at a pressure of about 2 to 3 atmospheres. This is continued for from two to
four hours according to the nature of the wood, leaf wood requiring a shorter time

page_text: and coniferous wood a longer time. As set forth in the prior patent cited there
occurs an extensive change or chemical alteration of the soluble constituents of
the wood and both the cell-walls of the wood, as also their contents form an in-
soluble chemical compound with the impregnating materials, whilst the inter-spaces
(lumina) of the cells of the wood remain quite free, consequently the elasticity of
the wood is not affected, but its durability is very considerably increased. The
compound used in my new process is, however, entirely different from that of the
above cited English patent. In the prior patent the basic sulphates of alumina
and of iron precipitate upon the fibres and are converted by the following boiling
with chloride of calcium and caustic lime into oxyhydrate of iron and hydrate of
alumina with separation of sulphate of lime; by this means on the one hand,
the dark colour of the impregnated wood is obtained and on the other hand the
hardness thereof is increased by the crystallisation of the gypsum. In my new
process, however, although basic iron and alumina salts are precipitated they
remain such and therefore they exist only slightly coloured on the wood fibres
(there being no other base present) and moreover the essential point of the process
consists in that the potassium of the kainit combines with the lignine to form a
new and hitherto unknown combination, which confers upon the impregnated wood
a horny quality. If wood and the like be boiled with concentrated solutions of
chloride of zinc at a temperature from 135° C. or thereabouts, the same dissolves
to form a tough gelatinous translucent mass, in which the metal is no longer
recognisable by ordinary re-agents, because it is chemically combined; this tough
gelatinous mass becomes like harn in water, and is unaffected by acids. I find that
also the chloride of potassium contained in kainit shews the same properties as
chloride of zinc and chloride of magnesium, and the chemical re-actions under
high pressure and at high temperature are the same with weak solutions, as those
contained with concentrated solutions at atmospheric pressure. From this there
follows the important and hitherto quite unknown fact, that a component part of
the wood combines with the potassium chloride of the kainit and serves to impreg
nate it with a fixed chemical combination which is insoluble or at any rate cannot
be extracted by water. It should be here remarked that the potassium already
present in the wood which remains as potash when wood is burned, must be com-
bined in similar form, because it also can only be extracted by lixiviation in a very
small degree. Wood treated according to the process set forth is much harder
than wood which is not so treated, it is consequently very suitable for polished
work because it is as tough as before, it is insensible to the action of atmospheric
spores or to rot or fungi, and has retained its natural colour, so that it is applicable
for all purposes, even for such for which wood treated according to the patent
process No. 25240 of 1897 would not be applicable, and finally the wood if treated
by my process with a sufficient quantity of kainit is rendered very difficult of com-
bustion, almost incombustible. From the foregoing will be perceived the differ-
ence and the novelty of my process as compared with that of the prior patent cited.
The advantages of the present process over the previous one consist briefly in
that:-
--
1. Only one boiling and consequently only about one half the expense is neces-
sary.
2. The natural colour of the wood is retained.
3. The combustibility of wood treated according to this process is much less than
that treated according to the previous process.
my
said
Having now particularly described and ascertained the nature of
invention and in what manner the same is to be performed, I declare that what
I claim is:
1. The above set forth process for impregnating wood and the like materials by
treating the same with boiling solution of sulphate of alumina and of a mixture
of sulphate of iron and sulphate of copper in solution in proportion of about one
to thirty to which a solution of kainit in the proportion of about one to forty is

page_text: subsequently added, and the material subjected to boiling for several hours at a
temperature of from 135° to 140° C. and under a pressure of about 2 to
3 atmospheres, substantially as described.
Dated the 26th day of November 1898.
W. P. THOMPSON & Co.,
322, High Holborn, London, W.C., Patent Agents for the Applicant.