An Improved Process for the Manufacture of Artificial Silk
Year: 1897

page_text: ted as amended in accordance with the decision of the Comptroller-
General dated the 17th day of October 1906.
(The Amendments are shown in erased type.)
PROVISIONAL SPECIFICATION. .
"An Improved Process for the Manufacture of Artificial Silk”
I, Dr. HERMANN PAULY, a subject of the German Emperor, residing at
Gerbergasse 38, Basel, Switzerland, Chemist, do hereby declare the nature of this
invention to be as follows:-
For making artificial silk, in most cases, it has been proposed to employ solutions
of nitro-cellulose, which are sometimes mixed with oils or the like, for the purpose,
it is stated, of increasing the gloss of the ultimate product. Since however this
nitro-cellulose is extremely easily-combustible, the said solutions have either been
mixed with reducing agents in order to effect a denitration of the artificial threads
or fibres, or it has been sought to effect this denitration by applying suitable
chemicals to the already prepared threads or fibres, so as to thus obtain a
material free from nitro-groups. Since such methods of manufacture present
difficulties with regard to a sufficient denitration, it has also been suggested
to start from the pure cellulose and to convert this, by the aid of sulphuric
acid and phosphoric acid, into a viscous syrup, which is formed into threads
or fibres. No process of this kind has, up to the present, been carried into
practice. From a viscous thick jelly of this kind, artificial fibres which
resemble the natural silk fibres in their external character, cannot be obtained
in practice. Also the chloride of zinc cellulose solutions proposed for the manufacture
of cellulose threads or fibres for the production of carbon filaments for glow lamps,
cannot be used for this purpose.
The applicant has discovered that, by the employment of none of such suggested
solutions, is it possible to obtain threads which form an effective substitute for
natural silk, but that these solutions are at best only suitable for producing objects
of such form, that is to say, of such thickness, as are suitable for the manufacture
of carbon filaments. If it be desired to use cellulose solutions for making
artificial silk, it must be possible to make fibres therefrom of about 0·004. to
0.009 millimetres in diameter, whilst for the manufacture of carbon filaments the
said artificial cellulose threads or fibres, for the same length, have a thousand times
the volume. In the experiments it was shown that such solutions are not adapted
to flow or be pressed through such fine openings, and thus produce an uninterrupted
strong thread of the desired fineness, and are therefore not applicable to the
purpose of the present invention. Moreover the 60 to 80 percent. of chloride
of zinc which they contain, which has to be washed out with alcohol, is detrimental
to the applicability and strength of the fibres. Nothing has therefore become

page_text: known, from additional experiments, as to how artificial silk can be made by means
of chloride of zinc cellulose solutions, since such experiments, even if they have
been made, were likewise void of result.
Further experiments showed me, moreover, that, by the application of a suitable
solvent, which can dissolve sufficient cellulose, and in which the solution produced
possesses the suitable consistency and capability of being filtered, it is possible
to make sufficiently fine and strong threads or fibres like silk fibres. Accordingly
in my invention I employ a suitable ammoniacal solution of cupric oxide
(cupraminonia) and I have discovered that, by such use of aminoniacal solution
of cupric oxide I am able to fulfil the above-mentioned requirements necessary
for the manufacture of artificial silk, and thus, by employing cheaper chemicals
which can, moreover, be recovered in a useful form in a simpler manner than
those employed with nitrocellulose, to obviate the circuitous methods heretofore.
necessary in the manufacture of artificial silk from nitro-cellulose, in which
expensive unrecoverable materials, such as nitric acid, alcohol, ether and denitrating
chemicals are employed. I' have also recognized it as a necessary condition for
the manufacture of, artificial silk, that the decomposition of the dissolved cellulose
must be avoided and that consequently in the manufacture and application of
cellulose solution, attention must be paid to the prevention of this decomposition,
since otherwise the manufacture of artificial silk in a practical manner is not
possible.
The carrying into practice of the invention will be more clearly explained by the
following example, iz
Cellulose of any origin, first freed from fat or oil by washing with a dilute
solution of an alkali, is carefully dried and then dissolved in ammoniacal solution
of cupric oxide. The latter can advantageously be produced by the action of air
on metallic copper in the presence of ammonia water, or by adding an insoluble
electro-negative metal, such for example, as platinum, or by the agency of the
electric current, in all of which methods the air can also be replaced by pure oxygen
gas. The solution should preferably contain at least about 15 grams of copper per
litre, whilst the ammonia gas can amount to about ten times that. About 45
grams of cellulose, or somewhat more, are dissolved per litre in such an ammoniacal
solution of cupric oxide. Thé complete solution requires about eight days. Since
the solubility of the cellulose in the ammoniacal solution of cupric oxide decreases
as the temperature incréases and on the other hand, the decomposition of the
cellulose in the above solution increases as the temperature increases, it is advan-
tageous to keep the vessel in which the solution takes place as cool as possible.
In order to enable a solution of this kind, for the preparation of which a particular
temperature is consequently necessary, to be employed in the manufacture of arti-
ficial silk, it is necessary that it shall be perfectly homogeneous, it must therefore
be carefully filtered before use. As a filter, fabrics of wool, gun-cotton glass-wool,
and also sand can be employed; the filtration can be carried out by the aid of
suction or centrifugal force in suitable known apparatus.
The solution then enters, through fine apertures into a liquid which precipi-
tates the cellulose, for example, dilute acetic acid, and is rolled moist onto a roller
rotating in a bath of dilute acid, for example, acetic acid, after removal of the
copper and the ammonia (which can both be recovered from this bath as the
corresponding salts), unrolled from the said roller, and in this unrolling dried by
means of warm air or heated rollers and then spooled.
In contrast with the processes of manufacturing artificial silk heretofore
employed, in which it was necessary to use solutions the solvents whereof (such
as alcohol, ether) easily evaporated and thus moreover were lost, in my improved
process, the artificial silk is made by. a wet method in which the chemicals
employed can be completely recovered. Also this circumstance renders the process
forming the present invention technically useful.
If desired; silk-waste can also be dissolved with the cellulose, or substances can
be added which serve for weighting as well as for.increasing the gloss, the rigidity, &c.,

page_text: the same, however, does not forin an essential part of the invention, which
consists in employing a cellulose solution in the preparation of which decomposition
of the cellulose is avoided, and which has the required consistency, and is perfectly
homogeneous.
Dated the 4th day of December 1807
· An improved Process for the Manufacture of Artificial Silk”.
I, Dr. HERMANN PAULY, Chemist, now of München-Gladbach, in the German
Empire, late of Gerbergasse 38, Basel, Switzerland, do hereby declare the nature
of this invention and in what inanner the same is to be performed, to be particu-
larly described and ascertained in and by the following statement :-
For making artificial silk, in most cases, it has been proposed to employ solutions
of nitro-cellulose, which are sometimes nixed with oils or the like, for the purpose,
it is stated, of increasing the gloss of the ultimate product. Since however this
nitro-cellulose is extremely easily-combustible, the said solutions have either been
mixed with reducing agents in order to effect a denitration of the artificial threads or
fibres, or it has been sought to effect this denitration by applying suitable chemicals to
the already prepared threads or fibres, so as to thus obtain a material free from
nitro groups. Since such methods of manufacture present difficulties with regard
to a sufficient denitration, it has also been suggested to start from the pure
cellulose and to convert this, by the aid of sulphuric acid and phosphoric acid,
into a viscous syrup, which is formed into threads or fibres. No process of this
kind has, up to the present, been carried into practice. From a viscous thick jelly
of this kind, artificial fibres which resemble the natural silk fibres
in their external character, cannot be obtained in practice. Also the chloride of
zinc cellulose solutions proposed for the manufacture of cellulose threads or fibres
for the production of carbon filaments for glow lamps, cannot be used for the pur-
pose of my invention.
The applicant has discovered that, by the employment of none of such suggested
solutions, is it possible to obtain threads which form an effective substitute for
for natural silk, but that these solutions are at best only suitable for producing
objects of such form, that is to say, of such thickness, as are suitable for the manu-
facture of carbon filaments. If it be desired to use cellulose solutions for making
artificial silk, it must be possible to make fibres therefroin of about 0.004 to
0.009 millimetres in diameter, whilst for the manufacture of carbon filaments the
said artificial cellulose threads or fibres, for the same length, have a thousand
times the volume. In the experiments it was shown that such solutions are not
adapted to flow or be pressed through such fine openings, and thus produce an
uninterrupted strong thread of the desired fineness, and are therefore not applicable
to the purpose of the present invention. Moreover the 60 to 80 percent of
chloride of zinc which they contain, which has to be washed out with alcohol, is
detrimental to the applicability and strength of the fibres. Nothing has therefore
become known, from additional experiments, as to how artificial silk can be made
by means of chloride of zinc cellulose solutions, since such experiments, even if
they have been made, were likewise void of result.
Further experiments showed, moreover, that by the application of a suitable
solvent, which can dissolve sufficient cellulose, and in which the solution produced
possesses the suitable consistency and capability of being filtered, it is possible to

page_text: make sufficiently fine and strong threads or fibres like silk fibres. Accordingly in
iny invention I employ a suitable aminoniacal solution of cupric oxide (cupram-
monium hydroxide) and I have discovered that, by such use of aminoniacal
solution of cupric oxide, I am able to fulfil the above-mentioned requirements
necessary for the manufacture of artificial silk, and thus, by employing cheaper
chemicals, which can, moreover, be recovered in a useful form in a simpler manner
than those employed with nitro-cellulose, to obviate the circuitous methods hereto-
fore necessary in the manufacture of artificial silk from nitro-cellulose, in which
expensive unrecoverable inaterials, such as nitric acid, alcohol, ether and denitra-
ting chemicals, are employed. I have also found it to be a necessary condition for
the manufacture of artificial silk, that the decomposition of the dissolved cellulose
must be avoided and that consequently, in the manufacture and application of
cellulose solution, attention must be paid to the prevention of this decomposition,
since otherwise the manufacture of artificial silk in a practical manner is not
possible.
The carrying into practice of the invention will be more clearly explained by
the following example, viz.
Cellulose of any origin, first freed from fat or oil by washing with a dilute solu-
tion of an alkali, is carefully dried and then dissolved in ammoniacal solution of
cupric oxide.
The manufacture of the ammoniacal solution of cupric oxide is preferably per-
formed by placing shavings or the like of copper into upright cylinders of earthen-
ware or other suitable material, pouring caustic ammonia liquor upon these
shavings and forcing air through such mixture; for this operation I prefer to
introduce the air near the bottom of the cylinder into the same and consequently
from below through the said mixture. This forcing of the air through the
mixture of ammoniacal liquor and copper shavings or the like is preferably con-
tinued until the solution thereby produced contains the necessary amount of
copper.
The solution of the copper (i.e. the formation of aminonia-copper-solution) may
be facilitated and accelerated by adding to the copper shavings to be employed in
the described process, pieces or shavings of a metal more electronegative than
copper platinum may be adapted for this purpose, the said solution of copper
may also be facilitated or accelerated by forcing, instead of air, pure oxygen
through the described mixture of ammoniacal liquor and copper shavings or the
like, whereby instead of the copper shavings or the like, copper shavings or the
like in conjunction with a metal more electronegative than copper (e.g. platinum),
may be employed.
or.
Generally the advantages obtained by the admixture of platinum shavings
the like and by the introduction of pure oxygen instead of air are not so consider-
able that the increase of the costs thereby caused would appear to be justified.
The described manufacture of the ammonia-copper-solution may be assisted by
the electric current in the following manner. One branch of an U-shaped tube
filled with aminoniacal liquor is charged with copper-shavings or the like and con-
tains a copper anode whilst in the other branch an iron cathode is immersed. After
having connected the anode and the cathode with the corresponding poles of a
source of electricity, oxygen is developed at the copper anode which causes the
formation of cupric oxide, the latter dissolving in the ainmoniacal liquor. Since
however the oxygen developed at the anode simultaneously causes oxidation of the
ammonia with the formation of nitrous acid, in most cases it would appear to be
preferable to abandon this troublesome and costly method.
The solution when prepared should preferably contain at least about 15 grams
of copper per litre, whilst the ammonia gas can amount to about ten times that.
About 45 grains of cellulose, or somewhat more, are dissolved per litre in such an
ammoniacal solution of cupric oxide. The complete solution requires about eight
days. Since the solubility of the cellulose in the ammoniacal solution of cupric
oxide decreases as the temperature increases and on the other hand, the decom-

page_text: position of the cellulose in the above solution increases as the temperature
increases, the vessel in which the solution takes place should be kept as cool as
possible. I find it advantageous to keep the temperature in the said vessel below
thirty degrees Celsius. In order to enable a solution of this kind, for the prepara-
tion of which a particular temperature is consequently necessary, to be employed
in the manufacture of artificial silk, it is necessary that it shall be perfectly
homogeneous, it must therefore be carefully filtered before use. As a filter, fabrics
of wool, gun-cotton, glass-wool, and also sand can be employed; the filtration can be
carried out by the aid of suction or centrifugal force in suitable known apparatus.
The solution then enters, through fine apertures, into a liquid which separates
the cellulose, for example, dilute acetic acid, and is rolled moist onto a roller
rotating in a bath of dilute acid, for example, acetic acid, after removal of the
copper and the ammonia (which can both be recovered from this bath as the
corresponding salts), unrolled from the said roller, and in this unrolling dried by
means of warin air or heated rollers and then spooled.
Thus in contrast with the processes of manufacturing artificial silk heretofora
employed, in which it was necessary to use solutions the solvents whereof (such as
alcohol, ether) easily evaporated and thus moreover were lost, in my improved
process, the artificial silk is made by a wet method in which the chemicals employed
can be completely recovered. This circumstance renders the process forming the
present invention technically useful.
If-desired;-silk-waste-ean-also-be-dissolved-with-the-cellulose,--or-substunees-can
be-added--which--serve--for--weighting--as--weil-as--for--increasing--the-gloss,--the
rigidity, &e.
To-the-eellulose-solution,-substanees-which-are-soluble-in--ammonia--copper--solu-
tion-may-be-added, such-substances-are-preferably,-natural-silk-(waste-silk-or-the
like),-of-which one-part-may-be-added-to-five-parts-of-cellulose-;-or-horn;-caseine-or
other-organic-substanees-can-be-admixed-with-the-cellulose:
The artificial silk produced according to the present invention can be weighted-
especially in dyeing such silk-in the manner and by the means usually employed
for weighting natural silk. Experiments have shown that, e.g. in dyeing black, the
silk (either natural or artificial silk) can be weighted with up to 100 per cent of
weighting substances.
The artificial silk produced according to the present invention and consisting of
cellulose is adapted in a high degree to take up alumina, and such artificial silk
takes up from acetate of aluminium, large proportions of hydrate of alumina.
The addition-of-the-said-substanees, however,-is-not-necessary-to-the-success-of
the-invention-as-I-propose-mainly-to-employ-a-cellulose-solution-only:---But-in--the
preparation--of--this--cellulose--solution--decomposition--of--the--cellulose--must--be
avoided, as--far--as--possible--and--it-must-have-the--required--consistency,--and--be
homogenous-as-hereinbefore set-forth.
Having now particularly described and ascertained the nature of my said inven-
tion and in what manner the same is to be performed, I declare that what I
claim is:-
The manufacture of artificial silk by a process wherein a solution of cellulose
(with-or-without-other-material-as-above-set-forth) in cuprammonium hydroxide
is prepared at a low temperature, and is allowed to issue through fine apertures into
a liquid (for example, acetic acid) which will separate the cellulose, and wherein, if
desired, the threads are wound onto a roller rotating in this liquid.
Dated the 29th day of Amet 1000
D. YOUNG & Co.,
11 and 12 Southampton Buildings, London, W.C.,
Agents for the Applicant.