IMPROVEMENTS IN SIZING OF PAPER
Year: 1884

page_text: I, ALEXANDER MITSCHERLICH, Professor of Chemistry and Doctor of Philosophy,
residing at 6 Leopold street at Friburg, Grand Duchy of Baden, German Empire,
do hereby declare the nature of my said invention for "IMPROVEMENTS IN SIZING
OF PAPER to be as follows:-
According to the following method, it will be possible to utilise in the paper
manufacture and other branches of industry, materials which, on account of the
large quantity in which they are obtained, are without value, and the removal
whereof causes very often great expenses; cheap fabrics of a good quality will on
'the contrary be prepared from them.
In the manufacture of sulphite cellulose and in other similar processes for
treatment of parts of plants, tannic acid and many other substances are obtained in
an aqueous solution (extract) as bye-products. Hitherto these bye-products have
very rarely been used for other purposes; for the most part they flowed off into
the water-gutters without being utilised and caused very often the manufacturers
great inconveniences by dirtying the gutters, destroying the 'vegetation, killing
the fishes &c.
According to my present invention, a good and easily performable utilisation of
these materials on a large scale will be rendered possible.
"3
In the paper manufacture for instance an immense quantity of substances is
daily used for the so-called "
Bizing process, which substances are partly of
vegetable and partly of animal origin. These substances can, advantageously,
mostly be replaced by the above named bye-products obtained in the manufacture
of sulphite cellulose, whereby this sizing process itself will be rendered a great deal
less expensive.
In the paper manufacture these materials can be applied either separately or in
conjunction with other suitable substances, as shewn in the following examples.
Sizing is best performed with such extracts of sulphite boilings, which are but
slightly colored, that is to say, which are as light as possible, as such, for instance,
which occur in the sulphite boiling of fir (Picea Abies L or Picea excelsa), the use
of dark colored extracts is of course eventually not excluded.
The sizing process itself can be carried out in several ways, and for more
simplicity some methods only of sizing paper may be described, namely―
1, Sizing of the finished paper by means of the extract.
2, Sizing by adding a large quantity of the extract to the paper pulp.
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page_text: These modes of sizing can of course be employed separately as well as under
certain circumstances combined one with another or with the modes already
known.
1) The sizing of the finished paper by means of the extract is effectuated in the
same manner as usually when glue is used and it is carried out after the extract
has been suitably concentrated.
It will often be desirable to alter the properties of this extract by means of
chemicals, for instance by reduction and oxidation, or to remove out of the extract
by means of precipitation, bodies which act for certain purposes of the paper
manufacture in a detrimental manner as the inorganic salts for instance, or to add
other substances to the extract, as for instance alum, starch etc.
2) If sizing is to be effectuated by adding large quantities of extract to the
paper pulp the extract is mixed either directly to the pulp or after the latter has
been treated in the same manner as described under 1). The same result is
obtained when the extractive matters remain in the cellulose in consequence of a
alight washing of the boiled wood, that is to say, when these matters are used
together with the cellulose (The lixiviation of the extractive matters existing in
the cellulose after the boiling goes on so slowly, that, unless they are not lixiviated
during a very long space of time, a quantity sufficient for the following sizing
process will still remain).
By this method of sizing is obtained not only that the paper can be used as
writing paper, but also that all the fibres of the paper intimately cohere because
the single fibres are close glued together.
The reason for this is, that not as it is the case in the usual sizing, by means of
glue, the glue-materials close only essentially the pores on the surface, but that the
sizing takes place throughout the whole body into the smallest particles of the
fibres. It is manifest that by this means the strength of the so produced paper
will considerably increase.
According to this method a higher or lower degree of transparency and sound
can be given if desired to the paper by a more or, less considerable addition of
extract or by exposing it to a stronger or weaker pressure.
3a) Hitherto resin soap was generally used in the paper manufacture for the
vegetable sizing in order to produce a precipitation by means of sulphate of alumina.
As the acids of the extract here in question precipitate resin with a part of the
extractive matters a particular sizing is obtained by using this extract in lieu of
the sulphate of alumina. Simultaneously with this sizing substance other sizing
bodies are generated, namely compounds of the tannic acids with the alkalies of
the resin-soap.
In the sizing by means of resin-soap and sulphate of alumina the paper remains
weakly transparent unless it is exposed to a very strong pressure and unless it
receives a very large surplus of these substances, if the latter be too large, another
inconvenience will occur as the paper becomes too brittle.
By this new method of sizing certain paper materials quite particular advantages
are obtained. In sizing for instance the sulphite cellulose by use of a sufficient
quantity of this glue material (extract and resin-soap) under otherwise equal
conditions, I get by the afterwards described proceeding a transparent and
very strong product, which comparatively is not too brittle and similar to the
paper-parchment.
The fibres of the cellulose consist of cells, which have hollow spaces, the walls of
the cells are soft and provided with a great number of pores. If under ordinary
circumstances a pressure is exerted upon the cleaned cell, this latter will so be
compressed, that the hollow space and the small pores will appear again (though
probably somewhat reduced) in consequence of the elasticity of the substance, when
the pressure has ceased; if however a glutinous substance is introduced into the
hollow space of the cells themselves and into the walls in consequence of the
chemical process of their production or the addition of the extract, each cell and
also the whole mass will be glued when the pressure has ceased. In consequence

page_text: of the above mentioned circumstances, by this new method of sizing, a more or
less glued mass is obtained, according as the fibre has been thoroughly washed, and
by this means a paper is produced which is provided comparatively with very few
hollow spaces and pores and appears in proportion to the quantity of extractive
matters more or less transparent and may mostly be used as paper-parchment.
36) In lieu of resin soap, other bodies may be used in this extract in order to
produce precipitation especially suitable for sizing paper. Particularly I name of
these the precipitate produced by glue. The extract by addition of a glue solution
like the other tannins gives precipitates; which, the extract being slightly colored
(as for instance that produced by sulphite boilings from fir wood) are slightly
colored themselves. These precipitates are excellent sizing substances.
If a cellulose is used, which to the purpose of sizing is but superficially washed,
or if some extract has been added to the paper pulp traces of the sizing substances
are deposited everywhere on the fibres by the addition of glue and by sufficiently
stirring up the pulp and an excellent sizing is thus obtained (leather-sizing). The
paper thus obtained, without being easily transparent, has a good sound and is of
an excellent strength which is generally a great deal superior to that of the papers
sized by means of resin.
This leather-sizing can also be performed in the following way; the paper after
having been sized by means of extract, is afterwards sized again by means of glue;
the order of these operations can also be inverted.
It is even possible, by means of leather sizing in the pulp, to prepare a strong
paper from ordinary wood paste whereby at the same time any considerable loss of
fibres will be avoided in consequence of the wood paste being more effectually
cemented together in the liquid than when the sizing is not applied to the pulp.
The resistance against tearing of thus sized paper has been examined and it has
been found that paper prepared only from ordinary wood-paste was capable to bear
even 24 lbs, while ordinary gazette paper of the same breadth and approximately
of the same weight bore only from 5 lbs to 13 lbs.
In lieu of the extract other bodies may be applied which precipitate the glue for
instance other tannin solutions; instead of glue, other bodies may also be employed
which precipitate tannin substances, as casein, albumen &c.
The principal advantages of the latter method of sizing (leather-sizing) are the
following ones.
(1) Sizing in the paper-pulp in contra-distinction to the sizing by means of glue
which requires a special operation.
2) Great strength of the sized paper.
3) Slight transparency of the same together with this strength.
4) A small quantity of rags or no rags at all (respectively no cellulose) are
necessary for the manufacture of useful paper.
5) Comparatively small expenses.
When the hollow spaces of the paper, treated as above described especially those
which are sized according to the method described under 3a, are farther filled up
with a body like linseed oil for instance, papers are obtained of a very great
strength and of nearly perfect transparency. The strength of such paper generally
exceedingly increases by the treatment with linseed-oil, even up to 70%.
The excellent transparency, strength and imperviousness to water of such paper
are properties which hitherto scarcely may have been reached and which make this
paper fit not only for tracing paper, but also for being used instead of dim-panes
of glass and generally for the manufacture of such transparent papers as are
intended to give protection against atmospheric influences at a very low expense
and further for many other similar applications.
Other impregnating materials as wax, paraffine etc. have not given a good result,
because the strength of the paper is prejudiced by them.
In a similar manner as in the manufacture of paper, the extract can be applied
also in other manufactures either by itself or in its precipitations, as for instance in
the manufacture of board and papier-maché textures and so forth,

page_text: If a comparatively large quantity of glutinous substance and a small quantity
of cellulose is employed, materials are obtained which are plastical and may
consequently be used for the manufacture of objects of greater hardness and tenacity
and also for cementing.
In the paper manufacture etc, sizing of fibrous material is taking place; if in
lieu of fibres a powder is used, bodies are obtained which have another appearance
but which are notwithstanding produced by the same process which in the paper
manufacture is called "sizing." This expression sizing may therefore also
correctly be employed in the following processes.
"
Like as the extracts 1 and 2 are used, as above indicated, somewhat as
impregnating material, they are also applied in the manufacture of objects prepared
from fine-grained powder, as gypsum, chalk and so forth. They may be put on
the object either afterwards or stirred with the powder to a pap. The latter
receives by them cementing and plastic properties and becomes solid when water-
absorbing powders, as gypsum for instance, are used, even the atmospheric air being
cut off. The precipitates of the extract as well as those of the tannin containing
substances obtained by glue, albumen, casein etc. may further very advantageously
be used as paste and generally as glutinous substance. This latter distinguishes
itself by comparatively insignificant alteration in the atmospheric air and also by
exceedingly great glutinating power. This latter property particularly appears
when finely divided matters, as chalk for instance, are mixed to these substances.
By a small admixture substances are obtained which act as paste, and by a larger
admixture excellent cements and matters which are very suitable to plastic
purposes. For the latter it will be very effective when pulverous and water
absorbing substances, preferably gypsum are added to the above mentioned
glutinous substance. The gypsum is mixed with the concentrated solution of the
extract, or with the slimy precipitates.
This mass according to the quantity of gypsum contained therein can be kept in
a soft state during a long time even during several days. The plastic property in
the wet state and the great strength in the dry state of this matter after having
become solid enables an application thereof on a very large scale in the arts as well
as in industry.
The execution of the above described method is for every competent party so
clear that any further explanation will not be needed.

page_text: COMPLETE SPECIFICATION.
I, ALEXANDER MITSCHERLICH, Professor of Chemistry and Doctor of Philosophy,
residing at 6 Leopold Street at Friburg, Grand Duchy of Baden, German Empire,
do hereby declare the nature of my invention for "IMPROVEMENTS IN SIZING OF
PAPER and in what manner the same is to be performed to be particularly
described and ascertained in and by the following statement:-
,,
My invention consists in a new method for the sizing of paper materials wherein
substances having a tanning action which precipitate animal glue are employed,
by which new method a new product, with peculiar qualities, also results.
The methods principally now in use for sizing paper are those by means of glue
and resin sizing. In the first of these methods, the ready made paper receives a
coating of sizing, whereas the internal parts remain unsized; in the case of the
second method, the separate fibres of paper are surrounded on their upper surface
by the sizing material and are stuck together by it.
According to the present invention, the sizing of paper materials is effected by
precipitating glue or resin soap by means of fluids containing tanning materials
that precipitate glue, and this method offers very material advantages over other
systems of sizing paper, in particular on account of the fact that thereby a paper
easily soluble in water is obtained.
The methods hereinafter described are based on the property of the solutions of
the tanning materials in dilute condition, to produce with a solution of resin soap
or of glue, precipitates of a strongly glutinous nature, which, provided the
precipitation in the pulp is carried out in a proper manner, envelopes the surfaces
of the fibres in such a way that the latter are mainly cemented together from the
outside.
According as resin soap or glue has to be precipitated by the tanning material
solution, the practical carrying out of this method will have to be modified both as
regards the proportions of the quantities and also in some other points, and
consequently they must be described separately.
In order to carry out the sizing with tanning material solution and resin soap,
there is poured over the pulp ready prepared in the rag-engine for sizing, for
every 260 lbs. thereof about 20 pints of fluid containing tanning material resulting
from sulphite boiling and corresponding in its effect with 6.5% tannin solution (or
other solutions containing tanning material having a similar effect may be used) and
after the solution is poured in, the pulp must be stirred up well so that the fibres
get properly soaked through with the tanning material fluid; a clear solution of
resin soap, made as neutral as possible, and containing, as best suited for this
purpose, 20% of resin soap, is then poured in gradually and in the proportion of
about 40 pints to about 260 lbs. of pulp, taking care to stir the latter up continually.
By this means, the resin soap solution comes into close contact with the fluid
containing tanning material, and a strongly glutinous precipitate forms on the fibres,
which is accelerated and completed if, after pouring in the solution of resin soap, the
pulp is properly stirred up for a time. It is advantageous to have in this case an
excess of the tanning material fluid, its existence being indicated in the acid reaction,
о

page_text: of the mass.
These operations can be carried out in the reversed order. The
proportions of quantities can of course be altered according to the degree of sizing
required.
Paper sized in this way distinguishes itself in many respects from other sorts of
paper prepared according to the common methods of sizing, and in some paper
materials, results of a very peculiar nature have been obtained. Thus, for instance,
in the case of sulphite cellulose, when sized according to the above method and
under similar proportions, a comparatively very firm and not too brittle material is
obtained, which is easily soluble again in a large quantity of water.
Sizing by precipitation of glue by means of fluids containing tanning material,
is also carried out in the pulp and in the most advantageous manner as will be
explained hereinafter, for two entirely different kinds of fibre-materials.
An acid reaction, perceptible by the aid of litmus paper, is produced in the pulp
by adding an acid to it, for instance, muriatic acid, in the case of sulphite cellulose,
whereupon about 44 lbs. of glue dissolved in as little fluid as possible containing
about 27 pints of tanning material are mixed with every 260 lbs. of pulp. The
tanning material fluid results from sulphite-boiling and corresponds in its effect on
the glue solution with 6.5% of tannin solution. The mixing is carried out in the
following manner:
°
A jet of the tanning material solution is fed in continuously from one side of
the rag engine containing the pulp, while the glue solution is injected from the
other side. Care must be taken that the solutions get as much mixed as possible
with the pulp by means of the action of the rag engine, the mass being then
rapidly diluted to a considerable extent. By the contact of the two diluted
solutions, the two bodies are precipitated continuously out of the fluid. The
precipitation thus effected envelopes the surface of the smallest particles of palp
with a glutinous substance. The influx of the solutions must not be too rapid, as
otherwise the precipitations will not descend in fine subdivision but in coarse masses
upon the fibres and will cause detrimental spots in the paper.
As soon as the necessary quantities of glutinous substances have been imparted
to the pulp, tanning material solution may advantageously be added, this being
thoroughly mixed up with the pulp and the mass then left alone for a quarter
of an hour.
It has been found that in sizing wood paste by itself as a paper material, the
most practical proportions when this process is used are about 104 lbs of sizing and
about 60 pints of the above tanning material fluid to every 260 lbs. of stuff.
The proportions of quantities between paper materials and the glutinous
substances, as also the operation and the kind of tanning material, can be altered
according to the qualities the product is required to have.
Too great an addition of the sizing materials can easily cause the paper to adhere
to the machine, which evil can however mostly be easily remedied by adding such
substances as, for instance, starch paste, etc.
"
The method herein described renders it possible to prepare from wood paste
alone, a paper that shall have a greater strength than common printing paper. The
resistance of paper thus sized offers to attempts to tear it has been tested, and it 4
was found that such paper was able to bear even 28 lbs. whereas common printing
paper of the same breadth and of about similar weight could not bear more than
from 5 to 15 lbs.
Papers sized according to the method above described have besides the particular
characteristic, that their sizing can be quickly removed by means of plenty of 5
water, by which means the paper is converted in a short time, and without injuring
the fibres very materially, into serviceable pulp, which can be immediately used
again.
In the case of paper which is strongly sized with tanning material and glue, it is
advisable, in order to make it dissolve easily in water, to warm it beforehand if 5
even only for a short time

page_text: Having now particularly described and ascertained the nature of my said
invention and in what manner the same is to be performed I declare that what
I claim is
1, The production of paper sized by means of glue or resin-soap in combination
with tanning materials that will precipitate glue, such paper being easily soluble in
plenty of water substantially as described.
2, The method of sizing paper materials by precipitating into aqueous fibre pulp
resin soap or glue by means of solutions of tanning materials substantially as and
for the purpose set forth.