close

Вход

Забыли?

вход по аккаунту

?

Патент USA US2407897

код для вставки
Patented Sept. 17, 1946
2,407,896
UNITED STATES PATENT OFFICE
2.407.898
METHOD OF RECOVEBJNG THE SALT
FORMING COMPONENTS OF NYLON
Clovis D. Myers, Ardcntown, DeL, assignm- to E. I.
du Pont de Nemours & Company, Wllminston.
DeL, a corporation of Delaware
1
No Drawing. Application June 29, 1943,
Serial No. 492,718
‘I (Balms. (Cl- 280-78)
2
This invention relates to a method or recover
ing, for reuse, the components from which syn
thetic linear condensation products are made.
More particularly, the invention relates to in Proc
ess of recovering, for reuse, of the salt-forming
components from which nylon is made.
For convenience, the invention will be de—
scribed in terms of Dolyhexamethylene adip
amlde, which is the common nylon on the mar
ket, although it will be understood that the in
vention is applicable to the related linear super
polyamides and lnterpolyamides.
Normal operation of a nylon plant results in
the unavoidable collection of waste material at
different points in the process. Economic opera
and the solid adiplc acid, which separated on
cooling, was removed by ?ltering in a vacuum
nutsche using a. glass ?lter cloth. The ?ltrate
was hydrolyzed for a second 5-hour period and.
after cooling, the adipic acid was again removed.
The filtrate containing sulfuric acid, the diamine
sulfate, and small dissolved quantities of adipic
acid were slowly added to a slurry of lime in wa
ter (1:7) maintained at a temperature of 70°
10 C. to neutralize the sulfuric acid and to obtain
a water solution containing free diamine. The
solid calcium sulfate and unreacted lime were
tion suggests that this expensive material be re—
removed by ?ltration. The calcium sulfate cake
was rc-slurried with water two or three times and
the washings added to the main solution. The
dlamine was obtained in a pure state by ?rst
worked into useful form. Moreover, there is
distilling water from the solution at atmospheric
today a great shortage of nylon and the raw ma
pressure and then distilling the diamine under
terials from which it is made, so that it is advis
35 mms. pressure at a temperature of 108° C.
able to rework even worn fabrics into useful ma 20 The adipic acid was puri?ed by treatment with
terials. Attempts to accomplish this by a partial
decolorizing carbon and by two crystallizations
depolymerization and re-polymerization has re
in water. Thehexamethylene diamine and the
sulted in only limited applicability. Such proc
adipic acid recovered by the process proved to be
ess can only be used for the reworking of quite
entirely pure and acceptable for making new
pure nylon waste of de?nitely known history and 25 nylon products which compared favorably with
is, therefore, not a practical solution to the pres
those made from the original raw material.
ent~day problem.
It is an object of this invention to provide a
Example II
practical method for isolating and quantitatively
recovering in the pure state, from nylon waste, 80 A batch of mrlon waste containing a blend of
the salt-forming components from which the
dyed polyhexamethylene adipamide stocking
nylon was made. It is a further object to pro
vide a process for recovering these raw mate
rials from any source of nylon waste, whether
dyed or undyed or mixed with other materials, 35
waste. undyed polyhexamethylene adipamide
woven fabric and polyhexamethylcne adipamide
scrap ?ake and containing about 4% cellulose
in the form of rayon was thoroughly washed,
dried and hydrolyzed as in Example I for 5 hours.
such as cotton, silk, wool, linen, etc. Other ob
Jects will appear hereinafter.
The hydrolysis mixture was cooled and the solid
adipic acid, together with the cellulose. was re
The objects of the invention are accomplished,
in general, by hydrolyzing the nylon with strong
moved by centrifuging. The hydrolysis proce
acids and repeatedly removing the acid compo 40 dure was repeated for two cycles of 5 hours each,
nents of the nylon salt. The following examples,
with the removal of adiplc acid by centrifuging
in which percentages are by weight, illustrate
after each operation. The ?ltrate was neutral
methods of recovering the salt-forming compo
ized with lime as in Example I, care being taken
nents from which the nylon under treatment was
that the agitation and rate oi’ addition were such
originally made in accordance with this inven 45 that the temperature did not exceed 90° C. The
tion.
'
solid calcium sulfate and unreacted lime were
separated by centrifuging.
Example I
The diamine was recovered from the ?ltrate by
A lot of dyed waste polyhexamethylene adip
distillation as in Example I. A small amount of
amide in the form of used stockings which had
sodium hydroxide was added to the still pot dur
been thoroughly washed, dried and graded to
ing the charging to permit the recovery of di
contain less than 4% of extraneous ?ber was
treated with sulfuric acid in water in the ratio of
1:1:1 at 115° C. to 120° C. under gentle re?ux
for 5 hours. The hydrolysis mixture was cooled 55
amine carbonate as diamlne. After the water
was removed, the diamine was distilled over at
a pressure of 30 nuns. and was caught in distilled
water.
2,407,896
The crude adipic acid cakes were puri?ed by
dissolving in 85° C. water. treatlnclwith decolor
izing carbon, ?ltering hot, and recrystallizlng.
The crystals were washed free of mother liquor
by restricted water washing. Both the hexa
methylene diamlne and the adipic acid so recov
ered were found to be entirely satisfactory for
use in the manufacture oi’ nylon.
The steps of hydrolyzing, cooling, in a heat
4
01’, and such components can be used in recon
structing the polymer. Polyamides oi the di
amine dlbasic acid type, described in the Caroth
ers Patents Nos. 2,130,523 and 2,130,948, may be
treated according to this invention to obtain the
salt-forming components, i. e. the dibasic acid
and the dlamine and the polyannde reconstructed
therefrom. The process of this invention can be
used to treat polyamides of the amino acid type,
exchanger, the hydrolysis mixture, ?ltering the l0 described in the Carothers Patent No. 2,071,253,
to obtain the amino acid. The principles of this
mixture to remove the adipic acid. and returning
invention can be applied to linear condensation
the ?ltrate to the hydrolyze: for further hydroly
products of the type formed by reacting a dipri
sis can be continuous in operation until the adipic
mary
diamine of radical length at least 4 and
acid is substantially removed, as hereinbeiore de
15 a polycarboxylic acid which is a tricarboxylic
scribed.
acid or a tetracarboxylic acid, the tricarboxyllc
In the examples, preference has been shown for
acid having at least one pair of carboxyl groups
a plurality of hydrolysis steps of 5 hours each.
attached
to adjacent carbon atoms, and the tet
The invention importantly depends on the dis
racarboxyllc acid having two and only two pairs
covery that the process will proceed satisfactorily
only if the adipic acid is removed from the hy— 20 of carboxyllc acid groups attached to adjacent
carbon atoms, as described in copending appli
drolysis mixture a plurality 0! times; for exam
cation Serial No. 456,383, for the purpose of re
ple, a 10- or 15-hour single hydrolysis step is not
covery of the acid which is employed in the prep
the equivalent of two 5-hour or three 5-hour di
aration of the condensation product. Likewise.
gestions, with removal of adipic acid between the
steps. In the former cases, the percentage re 25 a polyester of the type described in the Carothers
Patent No. 2,071,250 can be treated according
covery of adipic acid and hexamethylene dlamine
to this invention to obtain the ester-forming
is quite low, whereas, in the latter preferred cases,
components thereof. Similarly, the process will
it is substantially quantitative. It is not fully
be found advantageous in the handling of inter
understood why this is critical.
It will be understood, of course, that the es 30 polymers, such as interpolyamides, even without
separation of the individual diamines and indi
sence of the invention comprises a plurality of
vidual dibasic acids for the reason that fre
hydrolysis steps and a corresponding number of
quently it is desired to reconstruct the same
adipic acid removals and that the number of
interpolyamides.
treatments and the length of them are not criti
It is readily admitted that the cost oi‘ produc
cal within limits; for example, each digestion
ing nylon by starting with waste nylon yarn,
may proceed as long as 10 or more hours, if de
hydrolyzing it to the components of the original
sired, or as little as 3 hours. This is dependent
salt and reconstructing the polymer and spin
in part on the concentrations of waste yarn in
ning into yarn is more expensive than starting
the mixture, the concentration of sulfuric acid
and the hydrolyzing temperature. Generally. 40 with the components of the salt in the ?rst place.
However, in the present economic cycle, any
concentrations of sulfuric acid of about 50% are
step which can be taken to increase the quantity
preferred, but equally good results are secured
of nylon or nylon yarn available is important.
within the range of 30% to ‘70%. Similarly, a
Moreover, in a more ordinary economy, there will
temperature of about 120° C. is preferred. but
be an accumulation of nylon waste products of
temperatures within the range of 75° C. to 140° C.
such diverse characteristics that they cannot be
are fairly operative.
reworked and reused by a simple physical method.
While preference is had for the use of sulfuric
By reason of this invention, a truly commer
acid, in view of its cost and its ease or removal
cial process is now available for the production
as insoluble salts, the spirit of the invention in
cludes other strong mineral acids, such as hydro 50 from waste nylon products of the components
of the original salt from which the polymer was
chloric and phosphoric acids. Similarly, lime is
made. These materials are recovered in as pure
a known convenient agent for neutralizing the
form as they would be made synthetically and
spent acid but it is merely illustrative of known
they are recoverable on a ‘commercial basis in
agents, including caustic soda, soda ash and ba
65 quantities of about 90% of that which is theoret
rium hydroxide.
ically possible. The process or recovering these
In the examples, the nylon waste has been
materials in nowise interferes with the orderly
graded to include not more than 4% 0i extrane
manufacture of nylon and it involves the use of
ous fiber, such as cotton or regenerated cellulose.
relatively simple equipment.
It has been found that, when the quantity of
In the claims the term “mass” is meant to
such extraneous fiber exceeds 6%, di?iculties of 60
cover the material which is originally subjected
handling and ?ltration occur. While the process
to the ?rst hydrolyzing treatment and the liquid
is operative, it is usually better to lower the ex
remaining after a hydrolysis and removal of the
traneous ?ber by grading.
dibasic acid therefrom.
As a matter of convenience, the invention has
Since it is obvious that many changes and
been described in terms 0! the hydrolysis of poly 65
modi?cations can be made in the above-described
hexamethylene adlpamide yarn. since that is the
details without departing from the nature and
common nylon of the market. The invention is,
spirit of the invention, it is to be understood that
however, not restricted to this speci?c polymer,
the invention is not to be limited thereto except
since it will be obvious to those skilled in the art
that the process will work equally well with re 70 as set forth in the appended claims.
I claim:
lated polyamides and with suitable modi?cations
1. A process of recovering adipic acid and hexa
with related polymer yarns.
methylene
diamlne suitable for reuse from poly
The invention, in general, can be used with any
meric hexamethylene adipamide waste, which
hydrolyzable linear condensation polymer waste
to obtain the monomolecular components there 75 comprises repeatedly hydrolyzlng a mass con
5
2,407,898
tainlng the said adipamide with a mineral acid,
and removing the adiplc acid from the hydrolyzed
mixture of each hydrolyzing step.
2. A process of recovering adipic acid and hexa
methyiene diamine suitable for reuse from poly
meric hexamethylene adipamide yarn, which
comprises repeatedly and in sequence hydrolyz
ins a mass containing the said adipamide with a
mineral acid at a temperature of approximately
ture of each hydrolyzing step, thereafter adding
the solution remaining after the last removal of
the adipic acid to a slurry of lime and water to
neutralize said sulfuric acid and form calcium
sulfate, removing said calcium sulfate, and sep
arating the hexamethylene diamine from the re
sulting solution.
6. A process of recovering adipic acid and hexa
methylene
diamlne suitable for reuse from poly
75° C. to 140° 0., cooling the resulting hydrolyzed 10 meric hexamethylene
adipamide yarn by hydroly
mixture of each hydrolyzing step, and removing
sis, which comprises repeatedly hydrolyzlng a mass
the adiplc acid therefrom.
of said adipamlde with sulfuric acid, removing
3. A process of recovering adipic acid and hexa
the adipic acid from the hydrolyzed mixture of
methylene dlamine suitable for reuse from poly
meric hexamethylene adipamide yarn, which com 15 each hydrolyzing step, thereafter adding the so
lution remaining after the removal of the adlplc
prises repeatedly and in sequence hydrolyzing a
acid to a slurry of lime and water to neutralize
mass containing the said adipamide with sulfuric
said sulfuric acid and form calcium sulfate, the
acid of a concentration of approximately 59% at
rate of adding the solution being such as not to
a temperature of approximately 115° C. to 120°
0.. cooling the resulting hydrolyzed mixture of 20 increase the temperature of the neutralized mix
ture above 90'’ 0., removing said calcium sulfate,
each hydrolyzing step, and removing the adipic
and separating the hexamethylene diarnine from
the resulting solution.
7. A process of recovering adipic acid and hexa
methylene diamine suitable for reuse from poly
meric hexamethylene adipamide yarn by hydroly 25 meric
hexamethylene adipamide yarn by hydroly
sis, which comprises repeatedly hydrolyzing a
sis, which comprises repeatedly hydrolyzlng a
mass of said adipamide with a mineral acid,
mass of said adipamide with sulfuric acid, re
removing the adipic acid from the hydrolyzed
moving the adipic acid from the hydrolyzed mix
mixture of each hydrolyzing step, thereafter neu
tralizing the mineral acid in the solution remain 30 ture of each hydrolyzing step. thereafter adding
the solution remaining after the last removal of
ing after the last removal of the adlpic acid, and
the adipic acid to a slurry of lime and water to
separating the hexamethylene diamlne there
neutralize said sulfuric acid and form calcium
from.
sulfate, removing said calcium sulfate, and sep
5. A process of recovering adiplc acid and hexa
methylene dill-mine suitable for reuse from poly 85 arating the hexamethylene diamine from the re
sulting solution by ?rst distilling of! the water
meric hexamethylene adipamide yarn by hydroly
and then distilling oil’ the hexamethylene di
sis, which comprises repeatedly hydrolyzing a
amine.
mass of said adipamide with sulfuric acid, re
CLOVIS D. MYERS.
moving the adipic acid from the hydrolyzed mix
acid therefrom.
4. A process of recovering adipic acid and hexa
methylene diamine suitable for reuse from poly
Certi?cate of Correction
, Patent No. 2,407,896.
September 17, 1946.
OLOVIS D. MYERS
It is hereby certi?ed that error appears in the rinted speci?cation of the above
numbered patent requiring correction as follows:
the word "removaP’ insert last; and that the said olumn 6, line 15, claim 6, before
Letters Patent should be read with
this correction therein that the same may conform
to the record of the case in the
Patent O?ice.
Signed and sealed this 19th day of November, A. D. 1946.
[ml
LESLIE FRAZER,
First Assistant Uomrniuiomr of Patents.
5
2,407,898
tainlng the said adipamide with a mineral acid,
and removing the adiplc acid from the hydrolyzed
mixture of each hydrolyzing step.
2. A process of recovering adipic acid and hexa
methyiene diamine suitable for reuse from poly
meric hexamethylene adipamide yarn, which
comprises repeatedly and in sequence hydrolyz
ins a mass containing the said adipamide with a
mineral acid at a temperature of approximately
ture of each hydrolyzing step, thereafter adding
5
the solution remaining after the last removal of
the adipic acid to a slurry of lime and water to
neutralize said sulfuric acid and form calcium
sulfate, removing said calcium sulfate, and sep
arating the hexamethylene diamine from the re
sulting solution.
6. A process of recovering adipic acid and hexa
methylene
diamlne suitable for reuse from poly
75° C. to 140° 0., cooling the resulting hydrolyzed 10 meric hexamethylene
adipamide yarn by hydroly
mixture of each hydrolyzing step, and removing
sis, which comprises repeatedly hydrolyzlng a mass
the adiplc acid therefrom.
of said adipamlde with sulfuric acid, removing
3. A process of recovering adipic acid and hexa
the adipic acid from the hydrolyzed mixture of
methylene dlamine suitable for reuse from poly
meric hexamethylene adipamide yarn, which com 15 each hydrolyzing step, thereafter adding the so
lution remaining after the removal of the adlplc
prises repeatedly and in sequence hydrolyzing a
acid to a slurry of lime and water to neutralize
mass containing the said adipamide with sulfuric
said sulfuric acid and form calcium sulfate, the
acid of a concentration of approximately 59% at
rate of adding the solution being such as not to
a temperature of approximately 115° C. to 120°
0.. cooling the resulting hydrolyzed mixture of 20 increase the temperature of the neutralized mix
ture above 90'’ 0., removing said calcium sulfate,
each hydrolyzing step, and removing the adipic
and separating the hexamethylene diarnine from
the resulting solution.
7. A process of recovering adipic acid and hexa
methylene diamine suitable for reuse from poly
meric hexamethylene adipamide yarn by hydroly 25 meric
hexamethylene adipamide yarn by hydroly
sis, which comprises repeatedly hydrolyzing a
sis, which comprises repeatedly hydrolyzlng a
mass of said adipamide with a mineral acid,
mass of said adipamide with sulfuric acid, re
removing the adipic acid from the hydrolyzed
moving the adipic acid from the hydrolyzed mix
mixture of each hydrolyzing step, thereafter neu
tralizing the mineral acid in the solution remain 30 ture of each hydrolyzing step. thereafter adding
the solution remaining after the last removal of
ing after the last removal of the adlpic acid, and
the adipic acid to a slurry of lime and water to
separating the hexamethylene diamlne there
neutralize said sulfuric acid and form calcium
from.
sulfate, removing said calcium sulfate, and sep
5. A process of recovering adiplc acid and hexa
methylene dill-mine suitable for reuse from poly 85 arating the hexamethylene diamine from the re
sulting solution by ?rst distilling of! the water
meric hexamethylene adipamide yarn by hydroly
and then distilling oil’ the hexamethylene di
sis, which comprises repeatedly hydrolyzing a
amine.
mass of said adipamide with sulfuric acid, re
CLOVIS D. MYERS.
moving the adipic acid from the hydrolyzed mix
acid therefrom.
4. A process of recovering adipic acid and hexa
methylene diamine suitable for reuse from poly
Certi?cate of
Correction
, Patent No. 2,407,896.
_
September 17, 1946.
OLOVIS D. MYERS
It is hereby certi?ed that error appears in the rinted speci?cation of the above
numbered patent requiring correction as follows:
the word "removaP’ insert last; and that the said olumn 6, line 15, claim 6, before
Letters Patent should be read with
this correction therein that the same may conform
to the record of the case in the
Patent O?ice.
Signed and sealed this 19th day of November, A. D. 1946.
[ml
LESLIE FRAZER,
First Assistant Uomrniuiomr of Patents.
Документ
Категория
Без категории
Просмотров
0
Размер файла
553 Кб
Теги
1/--страниц
Пожаловаться на содержимое документа