Improvements in the Manufacture of Cellulose Tetracetate.
Year: 1898

page_text: Date of Application, 25th Aug., 1898
Complete Specification Left, 18th May, 1899 -Accepted, 1st July, 1899
PROVISIONAL SPECIFICATION.
Improvements in the Manufacture of Cellulose Tetracetate.
We, CARL OTTO WEBER, of Greengate, Salford, Lancashire, Chemist, CHARLES
FREDERICK CROSS, of 4, New Court, Lincoln's Inn, in the County of London,
Analytical Chemist, and ISIDOR FRANKENBURG, of Greengate Works, Salford,
Lancashire, do hereby declare the nature of this invention to be as follows:-
The manufacture of cellulose acetate by heating an equimolecular mixture of
cellulose and magnesium acetate with two molecules of acetyl chloride with or
without further addition of acetic anhydride cannot be carried out on a largo
scale owing to the impossibility to control the reaction which, although slow to
begin with, invariably proceeds at an increasing rate, causing a rise of tempera-
ture fatal to the desired result. Moreover the final product obtained if not
destroyed or at least seriously affected by the heat of the reaction is obtained in
the shape of a cake of enormous toughness, the further working of which almost
amounts to a practical impossibility.
All these difficulties could be readily avoided if the reaction between the acetyl
chloride and the cellulose would take place in the presence of a quantity of some
solvent sufficient to dissolve the acetyl cellulose at the rate at which it is formed.
Such a solvent is at present quite unknown, and by adding any of the generally
used solvents to the above mentioned acetylising mixture the reaction either
never starts at all or results in the formation of a product other than cellulose
tetracetate. It has been observed that in preparing an acetylising mixture as
above described and allowing the reaction to start certain solvents may now be
added in at first very small quantities, increasing, however in volume as the
reaction proceeds. Under these circumstances the addition of the solvent
although distinctly restraining the reactive energy of the acetylising mixture is
no longer able to stop the reaction altogether, which in this manner is easily
kept under control and finally results in the formation of a perfect thinly viscous
solution of cellulose tetracetate. Of solvents to be used in this manner only
very few of the known indifferent solvents are, however, applicable of such it has
been found nitro-benzene, its homologues, epichlorhydrine, and dichlorhydrine to
give very good results.
In carrying out this invention three pounds of an equimolecular mixture of
cellulose and magnesium acetate is employed that is to say, a mixture of 16 lbs.
of cellulose preferably such as is obtained from the well known sulphocarbonate
of cellulose with 14 of magnesium acetate. To this is added 1.8 lbs. of acetyl-
chloride and 1 lb. or thereabouts of acetic anhydride.
This mixture is now placed into a kneading machine provided with a heating
or refrigerating jacket and the mass most intimately mixed. As soon as the
reaction has gained an appreciable start, one gallon of nitro-benzene is added or
any of its homologues, or epichlorhydrine, or dichlorhydrine, at first in very
small quantities, adding a further quantity only after the previous addition is

page_text: absolutely homogenously incorporated into the acetylising mixture, the addition
as to quantity and time being regulated in such a manner that the last, and
largest portion of the above named quantity of solvent is added at about the time
when the reacting mixture has reached its temperature maximum which should
not exceed 70° centrigrade.
The agitation of this mixture is then continued for three consecutive hours
when a thinly viscid solution of the tetracetate is obtained containing only mere
traces of lower acetates, or unaltered cellulose.
This solution now, while still in the hot state, is strained and then immediately
run into 5 gallons of alcohol. The acetate separates out in the form of fine white
flakes which are separated from the mother liquor by filtration, washed with
warm alcohol, which washings are added to the mother liquor and then filter-
pressed.
The product thus obtained is without previous drying broken up and stirred
in a very thin pulp with water which is then heated to boil until all traces of
the organic solvent are driven off.
The acetate is now again filtered, washed first with warm water slightly acidu-
lated with hydrochloric acid in order to remove the last portions of magnesium
salts and the washing is then carried to neutrality with clean warm water. The
product is then pressed and dried at a temperature not exceeding 80° Centigrade.
The peculiar nature of the solution formed as above described becomes strik-
ingly apparent as the stage of precipitation with alcohol is reached when a pre-
cipitate results which instead of falling out in the usual form of slimy clots,
drying into very hard and even horny masses, which are only difficultly and
slowly soluble, forms a mass of fine flakes which after drying represent an
extremely light and soft product readily soluble in any of the solvents for cellu-
lose acetate.
Dated this 25th day of August 1898.
ABEL & IMRAY,
Agents for the Applicants.
DIBULIOIION.
Improvements in the Manufacture of Cellulose Tetracetate.
We, CARL OTTO WEBER, of Greengate, Salford, Lancashire, Chemist, CHARLES
FREDERICK CROSS, of 4, New Court, Lincoln's Inn, in the County of London,
Analytical Chemist, and ISIDOR FRANKENBURG, of Greengate Works, Salford,
Lancashire, do hereby declare the nature of this invention and in what manner
the same is to be performed, to be particularly described and ascertained in and
by the following statement:-
The manufacture of cellulose acetate by heating an equimolecular mixture of
cellulose and magnesium acetate with two molecules. of acetyl chloride with or
without further addition of acetic anhydride cannot be carried out on a large
scale owing to the impossibility to control the reaction which, although slow to
begin with, invariably proceeds at an increasing rate, causing a rise of tempera-
ture fatal to the desired result. Moreover the final product obtained if not
destroyed or at least seriously affected by the heat of the reaction is obtained in
the shape of a cake of enormous toughness, the further working of which almost
amounts to a practical impossibility.
All these difficulties could be readily avoided if the reaction between the acetyl
chloride and the cellulose would take place in the presence of a quantity of some
solvent sufficient to dissolve the acetyl cellulose at the rate at which it is formed

page_text: Such a solvent is at present quite unknown, and by adding any of the generally
used solvents to the above mentioned acetylising mixture the reaction either
never starts at all or results in the formation of a product other than cellulose
tetracetate. It has been observed that in preparing an acetylising mixture as
above described and allowing the reaction to start certain solvents may now be
added in at first very small quantities, increasing however in volume as the
reaction proceeds. Under these circumstances the addition of the solvent
although distinctly restraining the reactive energy of the acetylising mixture is
no longer able to stop the reaction altogether, which in this manner is easily
kept under control and finally results in the formation of a perfect thinly viscous
solution of cellulose tetracetate. Of solvents to be used in this manner only
very few of the known indifferent solvents are, however, applicable of such it has
been found nitro-benzene, its homologues including di-nitrocompounds-epi-
chlorhydrine, and dichlorhydrine to give very good results.
In carrying out this invention three pounds of an equimolecular mixture of
cellulose and magnesium acetate is employed, that is to say, a mixture of 16 lbs.
of cellulose preferably such as is obtained from the well known sulphocarbonate
of cellulose with 14 of magnesium acetate. To this is added 18 lbs. of acetyl-
chloride and 1 lb. or thereabouts of acetic anhydride.
This mixture is now placed into a kneading machine provided with a heating
and refrigerating jacket and the mass most intimately mixed. As soon as the
reaction has gained an appreciable start one gallon of nitro-benzene is added or
any of its homologues including di-nitrocompounds-or epichlorhydrine, or
dichlorhydrine, at first in very small quantities, adding a further quantity only
after the previous addition is absolutely homogenously incorporated into the
acetylising mixture, the addition as to quantity and time being regulated in such
a manner that the last, and largest portion of the above named quantity of solvent
is added at about the time when the reacting mixture has. reached its tempera-
ture maximum which should not exceed 70° centrigrade.
The agitation of this mixture is then continued for three consecutive hours
when a thinly viscid solution of the tetracetate is obtained containing only mere
traces of lower acetates, or unaltered cellulose.
This solution now, while still in the hot state, is strained and then immediately
run into 5 gallons of alcohol. The acetate separates out in the form of fine white
flakes which are separated from the mother liquor by filtration, washed with
warm alcohol, which washings are added to the mother liquor and then filter-
pressed.
The product thus obtained is without previous drying broken up and stirred
in a very thin pulp with water which is then heated to boil until all traces of
the organic solvent are driven off.
The acetate is now again filtered, washed first with warm water slightly acidu-
lated with hydrochloric acid in order to remove the last portions of magnesium
salts and the washing is then carried to neutrality with clean warm water. The
product is then pressed and dried at a temperature not exceeding 80° Centrigrade.
The peculiar nature of the solution formed as above described becomes strikingly
apparent as the stage of precipitation with alcohol is reached when a pre-
cipitate results which instead of falling out in the usual form of slimy clots,
drying into very hard and even horny masses, which are only difficultly and
slowly soluble, forms a mass of fine flakes which after drying represent an
extremely light and soft product readily soluble in any of the solvents for cellu-
lose acetate.
Having now particularly described and ascertained the nature of this inven-
tion and in what manner the same is to be performed, we declare that what we
claim is:
-
The manufature of cellulose tetracetate in the pure state by combining with
the acetylising mixture, essentially as above described, the use of solvents such

page_text: as nitro-benzene its homologues including di-nitrocompounds or dichlorhydrine
or epichlorhydrine essentially in the manner set forth for the purpose of restrain-
ing and controlling the reactions involved in the acetylising process.
Dated this 18th day of May 1809
ABEL & IMRAY,
Agents for the Applicants.