U.S. patent number 3,742,104 [Application Number 05/033,180] was granted by the patent office on 1973-06-26 for production of shaped synthetic articles having improved dyeability.
This patent grant is currently assigned to Celanese Corporation. Invention is credited to Saunders E. Jamison, John W. Soehngen.
United States Patent |
3,742,104 |
Jamison , et al. |
June 26, 1973 |
PRODUCTION OF SHAPED SYNTHETIC ARTICLES HAVING IMPROVED
DYEABILITY
Abstract
A chemical relaxation treatment for increasing dyeability of wet
spun difficultly meltable filamentary material such as high melting
polyamides, polyurethanes and polyureas which filaments are spun
from a concentrated sulfuric acid solution and coagulated in an
aqueous sulfuric acid bath. The residual sulfuric acid contained in
the filamentary material is subsequently activated to increase the
dyeability of the resulting product.
Inventors: |
Jamison; Saunders E. (Summit,
NJ), Soehngen; John W. (Berkeley Heights, NJ) |
Assignee: |
Celanese Corporation (New York,
NY)
|
Family
ID: |
21868962 |
Appl.
No.: |
05/033,180 |
Filed: |
May 8, 1970 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
Issue Date |
|
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481587 |
Aug 23, 1965 |
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Current U.S.
Class: |
264/78; 8/539;
264/210.4; 264/343; 8/130.1; 264/184; 264/210.8; 264/289.6 |
Current CPC
Class: |
D01F
11/08 (20130101); D01F 6/605 (20130101) |
Current International
Class: |
D01F
6/58 (20060101); D01F 6/60 (20060101); D01F
6/72 (20060101); D01d 005/12 (); D01f 003/10 () |
Field of
Search: |
;264/344,78,342,343,210,184 ;8/130.1,137,173 |
References Cited
[Referenced By]
U.S. Patent Documents
Primary Examiner: Woo; Jay H.
Parent Case Text
This invention which is a continuation application of copending
application, Ser. No. 481,587, filed Aug. 23, 1965, now abandoned
relates broadly to the production of shaped articles and, more
particularly, shaped synthetic articles having improved dyeability.
Claims
What is claimed is:
1. A method for producing polyamide fibers comprising:
A wet-spinning a solvent solution of a difficultly meltable,
filament-forming, poly(polymethylene)terephthalamide polymer
through a shaped orifice into a liquid coagulating bath in which
the said polymer is insoluble thereby to obtain a filamentary
material in gel state,
the solvent in which the said polymer is dissolved being sulfuric
acid containing at least 75 percent by weight of H.sub.2 SO.sub.4,
and
the liquid coagulating bath into which the said solvent is extruded
being aqueous sulfuric acid having a concentration lower than that
of the sulfuric acid in which the polymer is dissolved and such
that the solution of the polymer is coagulated into the form of a
gelled, filamentary material containing residual sulfuric acid;
B orienting the molecules of the gelled filamentary material by
stretching;
C subsequently activating the aqueous sulfuric acid in the oriented
filamentary material, before washing the latter, by heating the
said filamentary material at a temperature of from about
40.degree.C. to about 100.degree.C. in an aqueous solution of
polyethylene glycol for a period sufficient to increase the
dyeability of the final product;
D washing the resulting heat-treated filamentary material to remove
the excess sulfuric acid; and
E drying the washed filamentary material.
2. A method as in claim 1 wherein the aqueous sulfuric acid
contained in the oriented filamentary material is activated by
contacting the said filamentary material with hot, liquid
polyethylene glycol represented by the general formula
HOCH.sub.2 (CH.sub.2 OCH.sub.2).sub.n CH.sub.2 OH
where n is a number such that the average molecular weight of the
said polyethylene glycol is within the range of from about 500 to
about 10,000.
3. The method as in claim 1 wherein the polymer is a polymer
melting above 275.degree.C.
4. The method as in claim 1 wherein the poly(polymethylene)
terephthalamide is polyhexamethylene terephthalamide.
Description
Still more particularly the invention is concerned with a method of
preparing a particular class of shaped synthetic articles in film,
fiber or other form. This class includes shaped, wet-formed
difficultly-meltable polymers, especially fiber-forming
(fiber-formable) condensation polymers having nitrogen and/or
oxygen atoms, and preferably both nitrogen and oxygen atoms, as a
part of the polymer chain. More specific examples of such
condensation polymers are the high-melting polycarbonamides,
particularly those melting above 275.degree.C. such as
polyhexamethylene terephthalamide.
By "difficultly-meltable" polymers such as used herein are meant
polymers that cannot be shaped easily using melt-extrusion
techniques because they tend to degrade materially and/or to
polymerize further to a useless, infusible mass when heated
sufficiently to melt them.
It was known prior to the present invention that polymers to which
this invention is applicable could be formed into shaped articles,
specifically filaments or fibers. See, for example, U.S. Pats. Nos.
3,154,512 and 612 of Parczewski; 3,154,609-Cipriani;
3,154,610-Denyes; and 3,154,613-Epstein et al., each dated Oct. 27,
1964; and 3,179,618-Roberts, dated Apr. 20, 1965.
In the aforementioned U.S. Pats. Nos. 3,154,609, 610 and 613 it is
disclosed that condensation polymers of the kind with which this
invention is concerned can be dissolved in sulfuric acid containing
at least 75 percent by weight of H.sub.2 SO.sub.4 and that the
resulting solution can be extruded through an opening of
predetermined cross-section having at least one thin dimension into
a liquid coagulating or spin bath of aqueous sulfuric acid having
an acid concentration lower than that of the sulfuric acid in which
the polymer was dissolved and such that the polymer is coagulated
into a shaped article, e.g., a filamentary material, in gel
state.
The present invention is especially concerned with means for
increasing the dyeability of the final product, more particularly
by activating the aqueous sulfuric acid contained in the shaped
article, e.g., filamentary material (especially oriented
filamentary material) thereby to improve the dyeability, including
acid and disperse dyeability, of the washed and dried article or
material.
Various ways may be employed to secure effective activation of the
aqueous sulfuric acid contained in the gelled filamentary material
or other shaped article. For example, various liquid media may be
used for this purpose. (By "liquid" media are meant treating agents
that are in liquid state at the treating temperature; they may be
non-liquids, e.g., solids or semi-solids, at ambient temperature.)
The media employed should provide effective thermal contact for
activation of the aqueous sulfuric acid contained in the gelled
structure. Additionally, the available evidence indicates that
water-miscibility and a low rate of diffusion of the liquid
treating agent into the gelled body are desirable characteristics
of effective liquid media.
Examples of the aforementioned treating or activating agents are
polyethers having the recurring unit represented by the formula
[ O--R ].sub.n O-- I
wherein R represents a divalent organic radical, more particularly
a divalent hydrocarbon radical, and n is a number such that the
average molecular weight of the polymer is within the range of from
about 500 to about 10,000. Preferably the polyethers embraced by
Formula I are those which are water-soluble or miscible.
Thus, we may use as the treating agent in practicing this invention
polyoxyalkylene polyols having an average molecular weight within
the range of from about 500 to about 10,000 such as those available
from Wyandotte Chemicals Corporation, Wyandotte, Michigan, under
the names of PLURACOL V-5 and V-7.
More specific examples of treating agents that may be employed are
those represented by the general formula
ROCH.sub.2 (CH.sub.2 OCH.sub.2).sub.n CH.sub.2 OR' I I
wherein R and R' each represent a member of the group consisting of
hydrogen and monovalent organic radicals, more particularly
monovalent hydrocarbon radicals, and n is a number such that the
compound has an average molecular weight within the range of from
about 500 to about 10,000. Preferably the hydrocarbon radicals
embraced by the definitions of R and R', and which may be the same
or different, are either a lower alkyl radical containing not more
than seven carbon atoms, e.g., methyl, ethyl, and propyl through
heptyl radicals (both normal and isomeric forms); or a phenyl or
tolyl radical; or a benzyl radical.
When R and R' in Formula II each represent a hydrogen atom, the
compound is a polyethylene glycol which may be represented by the
general formula
HOCH.sub.2 (CH.sub.2 OCH.sub.2).sub.n CH.sub.2 OH III
wherein n has the same meaning as given above with reference to
Formula II.
Other examples of treating or activating agents that may be
employed include chlorinated hydrocarbons such as compounds that
are commercially available under the name of Arochlors (chlorinated
diphenyls); aromatic ethers such as diphenyl ether, methyl phenyl
ether, ethyl phenyl ether, the ditolyl ethers, etc; and
high-boiling, straight-chain alcohols such as lauryl alcohol and
others of the homologous series which, when not soluble in water,
are soluble in organic solvents, e.g., ethanol, and hence can be
washed from the gelled article.
The treating agents used in carrying the present invention into
effect, including those mentioned above by way of illustration, are
members of the class of substances that properly may be described
as being inert (substantially completely inert), heating (or
heat-transfer) media. This is indicated by the fact that some
beneficial effect in improving the dye-receptivity of the final
product is obtained by the use of heat alone, as is more fully
described later herein.
The treating or activating agents employed are preferably those
having an atmospheric boiling point or range of boiling points not
lower than about 150.degree.C., or, more preferably, not lower than
about 175.degree.C.; additionally, as indicated hereinbefore, it is
preferred that the treating agent have at least some miscibility
with, or solubility in, water or in an aqueous solution of sulfuric
acid. Preferably, too, the treating agent is one which is
immiscible with the polymer. It is also preferred to use a treating
or relaxation agent that does not have any appreciable vapor
pressure at the treating temperature; and this is especially true
with respect to certain chlorinated compounds the vapors of which
might have unfavorable physiological effects upon the
operators.
It is not essential that the treating agent be one that has at
least some solubility in water so long as it is soluble in some
organic solvent whereby the excess agent can be washed from the
treated acid-laden gelled article. However, the use of such a
non-aqueous washing fluid adds to the cost of the process unless it
is an inexpensive or a by-product fluid medium that may also serve
some other useful function concurrently with the washing
operation.
Another technique for activating the aqueous sulfuric acid
contained in the gelled article, e.g., gelled filamentary material,
is to heat the acid-laden structure after it has been removed from
the coagulating bath and while it is traveling through air. For
example, after orienting the molecules of a gelled filamentary
material along the fiber axis by stretching between stretch rolls,
the aqueous sulfuric acid contained in the oriented gelled
filaments is activated, before washing the latter, by heating the
said filamentary material at a temperature of from about
40.degree.C. to about 100.degree.C., preferably not higher than
about 90.degree.C., for a period sufficient to increase the
dyeability of the final product. The resulting heat-treated
filamentary material is treated, as by washing, to remove the
sulfuric acid, followed by drying.
The novel features of our invention are set forth in the appended
claims. The invention itself, however, will be most readily
understood from the following description taken in connection with
the accompanying drawing, which is illustrative of the invention,
and wherein
FIG. 1 illustrates schematically one embodiment of the
invention;
FIG. 2 illustrates schematically another embodiment of the
invention; and
FIG. 3 illustrates schematically still another embodiment of the
invention.
THE POLYMERIC MATERIAL
The polymers that are wet-formed into filamentary or other shaped
structures or bodies and then treated in accordance with this
invention to improve their dyeability are difficultly meltable,
fiber-forming polymers. Preferably the treatment is applied to
those polymers having repeating =NCO-- groups, more particularly
-NRCO- groups where R represents hydrogen or a monovalent organic
radical, e.g., a hydrocarbon radical such as a lower-alkyl radical.
Such polymers include the difficultly meltable polyamides such as
those wherein the --NRCO-- groups are attached to carbon atoms on
each side; the polyurethanes which contain repeating =NCOO--
groups, more particularly --NRCOO-- groups; the polyureas which
contain repeating =NCON= groups, more particularly --RNCONR--
groups, and similar condensation polymers.
There is no particular advantage in wet-forming, e.g.,
wet-spinning, many of the polymers of the classes broadly described
in the preceding paragraph, more particularly those which are
adapted to be melt-extruded through orifices, slots or other shaped
openings to form the shaped body. However, in the case of the
high-melting or difficultly meltable polymers, such polymers must
be wet-spun rather than melt-spun. Wet-spinning often leads to
voids that adversely affect certain properties, e.g., dyeability of
the spun filaments of yarn. The present invention is one solution
to this problem. It provides practical means for altering and/or
aiding in the alteration of the internal structure of the polymer
so as to remove such voids thereby to improve the dyeability,
luster and other useful and desirable properties of the article;
and, especially, to do so as a step in a continuous process.
Thus, the technique of the instant invention is most useful when
applied to shaped articles formed of high-melting polymers, more
particularly those melting above 210.degree.C. and especially above
275.degree.C.; polyurethanes and polyureas melting above
179.degree.C., especially above 210.degree.C.; and, in general,
polymers having cyclic groups such as 1,4-cyclohexylene and/or
heterocyclic groups such as piperazylene or an alkyl-substituted
piperazylene group, e.g., 2-(lower-alkyl) piperazylene such as
2,6-dimethylpiperazylene, as an integral part of the polymer
molecule.
Some contemplated polyamides are, for example, those having
repeating structural units of the formula
--NR--Y--NR'--CO--Y'--CO--
that result from the condensation of a dicarboxylic acid or a
derivative thereof, e.g., a salt, acyl halide, or ester of such an
acid, with a diamine, wherein the R's, which may be the same or
different, are hydrogen or monovalent organic radicals, e.g.,
lower-alkyl radicals such as methyl or ethyl, and the Y's, which
also may be the same or different, are divalent organic radicals
such as alkylene, e.g., ethylene, tetramethylene or hexamethylene,
arylene such as para- and meta-phenylene, para- and meta-xylene,
and para- and meta-diethylene-benzene, cycloalkylene such as 1,
4-cyclohexylene and divalent heterocyclic radicals such as those
derived from piperazine, and monoalkyl- and dialkylpiperazines,
e.g., 2-methyl- and 2,5-dimethylpiperazines and 2-ethyl- and
2,5-diethylpiperazines, wherein the open bonds are attached to the
nitrogen atoms, and wherein the chemical structure of the polymer
and/or the polymerization technique used is such that a relatively
high-melting polymer is obtained.
An important group of polyamides within the above group, and to
which the present invention is especially applicable in treating
shaped articles wet-formed therefrom, includes those in which Y
and/or Y' is or contains a para- or metaphenylene radical or a
1,4-cyclohexylene radical. Particularly important are condensation
products of a diamine and terephthalic acid or a derivative of
terephthalic acid, e.g., tere-phthalyl chloride or a dialkyl
terephthalate. Some specific polymers within this latter group are
poly(polymethylene) terephthalamides wherein the polymethylene
groups contain from two to 10 carbon atoms, inclusive, e.g.,
polyhexamethylene terephthalamide, polyoctamethylene
terephthalamide, polytetramethylene terephthalamide, polyethylene
terephthalamide, and polypiperazylene terephthalamide. Other
polyterephthalamides are poly(o-, m-, and p-phenylene)
terephthalamides, poly(o-, m-, and p-xylylene) terephthalamides and
poly(o-, m-, and p-diethylenephenylene) terephthalamides, the
latter produced, for example, by condensing an ester-forming
derivative of terephthalic acid with para-bis(beta-aminoethyl)
benzene.
The treatment of this invention is applicable in the production of
filaments and other shaped articles of high-melting polyamides of
aromatic acids other than terephthalic acid, e.g., of isophthalic
acid, 2,6-naphthalenedicarboxylic acid, p,p'-dicarboxydiphenyl,
(p,p' -dicarboxydiphenyl) methane, phenylenediacetic acid,
phenylenedipropionic acid, and phenylenedibutyric acid. The diamine
moieties of these other aromatic carboxylic acids may be the same
as in the aforementioned polyterephthalamides. Illustrative, then,
of polyamides other than the polyterephthalamides are the
polyisophthalamides, especially polyethylene isophthalamide. The
treatment of the present invention also may be employed in making
shaped bodies from high-melting polyamides resulting from a
condensation reaction between (a) alkylene dicarboxylic acids such
as adipic acid and (b) cyclic diamines such as p-xylene diamine and
p-bis(amino-ethylbenzene).
Also contemplated is the treatment of shaped, high-melting,
autocondensation polymers (e.g., those melting above 275.degree.C.)
of an aminocarboxylic acid or a lactam or other derivative of such
an acid, which polymers have repeating structural units of the
formula --NR--Y--CO-- wherein R and Y are as defined above. Some
specific polyamides melting above 275.degree.C. within this group
are polymers of the following: 1-carboxymethyl-4-aminocyclohexane
or its lactam, 1-carboxy-4-aminocyclohexane or its lactam and
1-carboxymethyl-3-aminocyclopentane or its lactam.
Polyurethanes that may be wet-formed and treated in accordance with
this invention are polymers having repeating structural units of
the formula
--NR--Y--NR'--CO--O--Y'--CO--O--
and resulting, for example, from the condensation of a diisocyanate
with a dihydric alcohol or phenol or the condensation of a diamine
with a bis(chloroformate) of a dihydric alcohol or phenol, where
the R's and Y's are as described above in connection with the
polyamides, and the chemical structure of the polymer and/or the
polymerization techniques used are such that a polymer melting
above 179.degree.C., preferably above 210.degree.C., is obtained.
Particularly useful in practicing this invention are polyurethanes
prepared from dihydric alcohols or phenols containing a meta- or
para-phenylene or a 1,4-cyclohexylene radical. Some specific,
shaped polyurethanes which may thus be treated are the condensation
product of piperazine with the bis(chloroformate) of
bis(p-hydroxyphenyl)-propane-2,2, the condensation product or
piperazine with the bis(chloroformate) of hydroquinone and the
condensation product of tetramethylene diamine with the
bis(chloroformate) of butanediol-1,4, each of which has a melting
point above 210.degree.C.
Polyureas that may be wet-formed and subjected to the treatment of
this invention include those having repeating structural units of
the formula
--CO--NR--Y--NR-- CO--NR'--Y'--NR'--
wherein the R's and Y's are as defined above. They may be
synthesized, for example, by the addition of a diisocyanate to a
diamine, the condensation of a diurethane with a diamine, the
condensation of a carbon oxyhalide such as phosgene with a diamine,
or by heating an alpha,beta-diurea with a diamine, the chemical
structure of the polymer and/or the polymerization technique being
such that a polymer melting above 170.degree.C., preferably above
210.degree.C., is obtained. Some specific polyureas that may be
employed in practicing this invention are those obtained from the
reaction of hexamethylene diisocyanate with hexamethylene diamine
and from the reaction of m-pheynlene diisocyanate with m-phenylene
diamine, each of which polyurea melts above 210.degree.C.
The polymer-containing solvent solutions or dopes which are
prepared and extruded to produce a shaped article are preferably
made by dissolving the polymer in sulfuric acid containing at least
75 percent, more particularly at least 80 percent, by weight of
H.sub.2 SO.sub.4. Preferably, too, the sulfuric acid is
concentrated sulfuric acid containing 95 to 100 percent by weight
of H.sub.2 SO.sub.4. Fuming sulfuric acid, e.g., such acid
containing up to 6 or 7 percent by weight or even higher of free
SO.sub.3, also may be employed. A suitable concentration of polymer
in the dope is in the range of, for example, from 5 to 30 percent
by weight.
The use of solvents for the difficultly meltable condensation
polymer other than sulfuric acid is not precluded. For example,
instead of using sulfuric acid as a solvent, one may employ a
solvent containing over 85 percent by weight of phosphoric acid
(see U.S. Pat. No. 3,154,612, supra); or a solvent comprising at
least 70 percent by weight of antimony trichloride and formic acid
or acetic acid as a diluent in an amount up to 30 percent by weight
of the solvent (see U.S. Pat. No. 3,154,512, supra).
The liquid coagulant or spin-bath composition is a liquid in which
the solvent employed to dissolve the polymer is soluble but in
which the polymer is insoluble. Generally it is desirable to use,
as the liquid coagulant, a liquid containing a lower concentration
of the same solvating agent employed in making the polymer
solution, said lower concentration being such that the polymer is
coagulated into a gelled structure such as a sheet, film, tape,
ribbon, band, rod, tube, bar, cylinder, monofilaments,
multifilaments (including tow), and the like. Thus, when the
solvent in which the polymer is dissolved is sulfuric acid
containing at least 75 percent, or at least 80 percent, by weight
of H.sub.2 SO.sub.4, the liquid coagulating bath is preferably
aqueous sulfuric acid having a concentration of H.sub.2 SO.sub.4
lower than that of the sulfuric acid in which the polymer is
dissolved and, as aforementioned, such that the solution of the
polymer is coagulated into the form of a gelled structure or
body.
When using the preferred liquid coagulant, i.e., aqueous sulfuric
acid, the concentration of sulfuric acid in said liquid coagulant
may be varied considerably depending upon, for example, the
particular technique employed in activating the aqueous sulfuric
acid contained in the gelled material and/or other modifications of
the process and/or the properties other than improved dyeability
that are wanted in the final product. However, such acid
concentration, especially when wet-forming polyterephthalamides
such as polyhexamethylene terephthalamide, i.e.,
poly(hexamethyleneterephthalamide), may be below about 60 percent
by weight H.sub.2 SO.sub.4, e.g., from 0 percent to 50 percent. By
"0 percent" it is meant that water alone is the liquid coagulant
into which the sulfuric acid solution of the polymer is extruded to
form the gelled structure, the liquid coagulant then becoming
acidified with H.sub.2 SO.sub.4 as it extracts this acid from the
gelled structure during passage of the latter through the liquid
coagulating bath.
When gelled films (especialy such films which yield a transparent
film as a final product) are to be prepared, the use of lower
sulfuric acid concentration of the liquid coagulant, for example
below about 40% H.sub.2 SO.sub.4, more particularly within the
range of from 0 percent to 30 or 35 percent H.sub.2 SO.sub.4, are
conducive to the formation of thicker films if and when
desired.
The temperature of the coagulating bath may be varied as desired or
as may be required depending for example, upon the particular
polymer employed, the particular solvent used to dissolve the
polymer, the particular liquid coagulant used, the extrusion rate,
the particular properties desired in the final product, and other
influencing factors. Thus, the bath temperature may range, for
example, from room temperature (20.degree.-30.degree.C.) to about
100.degree.C., but preferably is within the range of from about
40.degree.C. to about 60.degree.C. When necessary, heating coils or
other sources of heat may be provided in order to maintain the
coagulating bath at the desired temperature above ambient
temperature.
In the embodiment of the invention illustrated in FIG. 1 and which
shows one technique for making filamentary material, the gelled
filaments are continuously pulled through the coagulating bath.
However, while in the coagulating bath the filaments are brought
into contact with at least two, smooth, curved surfaces which are
so positioned with respect to each other, and with respect to the
direction of travel of the moving filamentary material, that the
said filamentary material is caused to so reverse its direction
that its angle of bend is at least about 40.degree.. Thus, the
angle of bend or snubbing angle in effecting orientation of
filamentary material may be within the range of from about
40.degree. to about 120.degree., more particularly from about
60.degree.to 90.degree., e.g., 60.degree., 70.degree., 80.degree.
or 90.degree.. In similarly orienting films, the snubbing angle may
be up to 180.degree..
The smooth, curved surfaces to which reference has been made in the
preceding paragraph may take the form of two rods or pins that are
so positioned as to provide the aforementioned angle of bend. Such
rods or pins may be formed of, or at least surfaced with, a smooth,
hard, wear-resistant surface such as those that are commercially
available under such names as Alsimag (and which is understood to
be an aluminum magnesium silicate), Heanium (mainly Al.sub.2
0.sub.3), and the like.
The rods or pins mentioned in the preceding paragraph may be
disposed in the coagulating bath so that they extend vertically
downwardly into the bath of liquid coagulant. Since the amount of
tension imposed upon the filamentary material (for the same rod or
pin diameter) is dependent upon the relative orientation of the
rods, it is desirable to mount both rods upon a common head. Such a
head may take the form of a fork mechanism for mounting a pair of
rods as is shown in the copending application of one of us
(Saunders E. Jamison), Ser. No. 233,827, filed Oct. 29, 1962, and
assigned to the same assignee as the present invention. Thus, by
merely rotating a shaft to which is attached a mounting head
carrying the two rods in spaced relationship, the said two rods can
be readily disposed at the desired angular position with regard to
the direction of travel of the gelled filamentary material.
With regard to the foregoing comment concerning the amount of
tension imposed upon the filamentary material by the rods or pins,
it may be further mentioned that the amount or degree of tension
exerted by such rods or pins is proportional to the friction
imposed upon the moving filamentary material and that the latter,
in turn, depends upon the contact distance. Hence the diameter of
the snubbing pin or rod is important. In the technique herein
described with reference to the angle of bend or snubbing angle of
the moving filaments, the diameter of the pin or rod over which the
filamentary material was passed, when calculating the snubbing
angle, was one-fourth inch. Consequently, it is to be understood
that in the description herein given with reference to the angle of
bend of the moving filamentary material, the stated angle of bend
provides friction or tension corresponding to that obtained when
the moving filamentary material is passed, at the specified angle
of bend, over a rod or pin one-fourth inch in diameter.
It is not essential that the rods or pins extend vertically
downwardly into the bath of liquid coagulant. Thus, if desired,
they may be positioned horizontally in the coagulating bath.
Also, it is not essential that one use stationary rods or pins in
the coagulating bath as tension-inducing members positioned to
provide the desired angle of bend. For example, a pair of
positively driven rotating rolls may be utilized. Such rolls are
each rotated at the same speed, which speed is less than that of
the take-up roll. Accordingly, by winding the gelled filamentary
material about each of such rotating rolls positioned in the
coagulating bath and about the take-up roll, more or less tension
(as desired or as conditions may require) can be imposed upon the
filamentary material while it is in the coagulating bath. The
amount of induced tension can be controlled by varying the
differential in speed of rotation between the pair of such rollers
in the bath of liquid coagulant and the take-up roll.
After being oriented by snubbing in the coagulating bath as
described above, the oriented filamentary material is withdrawn
from the coagulating bath by any suitable means and contacted with
a liquid medium or a plurality of different liquid media which are
effective in activating the aqueous sulfuric acid retained or held
by the oriented, gelled filamentary material. The concentration of
the H.sub.2 SO.sub.4 in the solvent in which the polymer is
dissolved to form the spinning dope, the concentration of the
H.sub.2 SO.sub.4 in the spin bath, the temperature of the said bath
and the distance the coagulated filaments are led through the bath
before being withdrawn therefrom are preferably so adjusted that
the concentration of H.sub.2 SO.sub.4 in the aqueous sulfuric acid
retained by the filamentary material when it is removed from the
bath is within the range of, by weight, from 51 to 58 percent,
preferably from 54 to 57 percent, thereof.
From the spin bath the oriented filamentary material is led over
guide or skew rolls, or any other suitable guide means, to a liquid
treating means for activation of the aforesaid H.sub.2 SO.sub.4
retained by the filamentary material. The liquid activating agent
or treating medium may be applied to the filamentary material by
any suitable means, e.g., while it is continuously moving in a
helical path over a pair of converging or skew rolls; or, as shown
in FIG. 1, by passage through a bath of the liquid treating
agent.
The general characteristics of liquid media that are useful as
activators of the aqueous sulfuric acid retained by the gelled
material in filamentary or other form have been given hereinbefore.
Particularly useful are the polyethylene glycols (polymers of
ethylene oxide). Typical properties of the latter compounds, which
are commercially available, are the following: ##SPC1##
In general, the application temperatures (i.e., the temperature at
which the treating agent is applied to the gelled material) are
within the range of from about 50.degree.C. up to a temperature
just below (e.g., about 5.degree. or 10.degree.C. below) the
temperature of incipient softening of the polymer. Usually, the
upper temperature limit is not higher than about 150.degree.C. In
all cases the temperature employed is such as will convert the
treating agent to liquid state if it is not initially in such
state.
The period of time that the treating agent remains in contact with
the shaped polymer in gel state, under the particular temperature
conditions employed, is in all cases sufficient to improve the
useful and desirable properties, especially dye-receptivity, of the
treated material. It is difficult to state this time period with
exact precision since there are so many different variables that
may influence it. These include the constitution of the polymer
being treated, its denier if in filamentary form or its thickness
if in film, sheet or other form, the particular wet-forming
technique employed, the temperature at which the treating agent is
applied, the particular concentration of H.sub.2 SO.sub.4 in the
aqueous sulfuric acid retained by the gelled polymeric material
being treated, and other influencing factors.
For obvious reasons, it is desirable that the time and temperature
employed in applying the liquid treating agent, and the
concentration of H.sub.2 SO.sub.4 in the aqueous sulfuric acid
retained by the gelled body undergoing treatment, are not such as
will result in excessive softening of the shaped polymer, and
especially when the latter is in the form of multifilamentary
material. Such excessive softening can lead to coalescence (i.e.,
sticking or fusing together) of the individual filaments, which is
undesirable.
The available evidence indicates that the contact time at the
application temperature should, for optimum results, be sufficient
to result in a rapid and efficient transfer of heat from the
treating agent to substantially all of the aqueous sulfuric acid
retained by the shaped, gelled polymer. At treating temperatures
within the range of about 50.degree.-150.degree.C., this time is
usually less than 5 minutes. The time will vary depending upon the
particular temperature employed within this range; the internal
structure (e.g., size, arrangement and number of voids in the
structure) of the particular gelled polymer being treated; the
viscosity of the treating agent at the treating temperature and its
degree of miscibility with water; and other influencing factors.
For example, at higher temperatures approaching the point of
incipient softening of the gelled polymer and when the treating
agent employed has a relatively low viscosity at the treating
temperature, it may be necessary to limit the time of the treatment
to one-fourth second or lower (that is, to cause it to occur almost
instantaneously) in order to avoid or minimize fiber
coalescence.
The upper time limit of the application temperature is critical
only to the extent that it should not be so long that the sulfuric
acid in the gelled material during the treatment adversely affects
the useful properties of the final product. For instance, as has
previously been indicated, the time should not be so long as to
result in excessive (if any) coalescence of individual filaments of
a multifilamentary material. The maximum treating time in some
cases may be as long as 12 to 24 hours, or even 2 or 3 days or
more, provided that there are no adverse effects such as an
objectionable decrease in tensile strength, failure to obtain
optimum improvement in dyeability (especially with acid and
disperse dyes), discoloration, loss of luster, and the like.
The liquid treating or activating agent, together with any aqueous
sulfuric acid that may still be retained by the gelled, shaped
polymer in filamentary or other form, is removed from the gelled
structure by any suitable means. For example, washing may be
effected while the gelled material, especially when it is a
filamentary structure, is passing in a helical path over a pair or
a plurality of pairs of wash rolls or reels. Or, a wash trough or
vessel, as illustrated in FIG. 1, or a series of wash troughs or
vessels through which the unwashed, treated, gelled material
passes, may be employed. Preferably, the unwashed material passes
countercurrently to the flow of the washing fluid.
The washing fluid may be water alone or a combination of water and
other washing fluids in different permutations. For example, an
initial wash with water may be followed at a second station by an
alkaline wash (e.g., a water solution of ammonia, or an aqueous
solution of sodium or potassium carbonate or bicarbonate), followed
by another water wash at a third station; or the alkaline wash may
be applied first followed by a water wash and then by a wash with a
more volatile wash fluid than water, e.g., acetone, methanol,
ethanol or the like. Any desired or required number of wash
stations may be employed to remove the excess acid and/or
activating agent from the treated, gelled material, e.g., 1,2 or 3
through 10 stations, or more, if necessary.
The washed, gelled material is then dried by any suitable means
either before or after collection on a take-up roll. In many cases,
passage of the gelled structure (particularly if in film form)
through air at room temperature causes the film to dry sufficiently
for take-up (without sticking of contacting layers on the roll),
especially if a volatile solvent such as acetone or methanol has
been applied as a final wash before take-up, and the time of
exposure to air has been sufficiently long to volatilize
substantially all of the solvent. Washed films also may be dried
by, for example, passing the film through a drying zone such as a
heated oven while held on a support. Preferably washed, gelled,
filaments, sheets, films and other elongated structures of
continuous (i.e., indefinite) length are dried by passage over the
warm or hot (up to about 130.degree.C.) surfaces of a heated roll.
Where discoloration under heat may be objectionable, e.g., in the
production of thin transparent films, drying at an elevated
temperature is preferably done in a non-oxidizing atmosphere, e.g.,
nitrogen, helium, argon, etc.
Instead of using snubbing pins as illustrated in FIG. 1 to effect
orientation of the freshly spun, gelled or coagulated filaments,
the filamentary material may be passed over a guide and led out of
the coagulating bath for stretching between rolls as illustrated in
FIG. 2. (Draw ratios in practicing this invention are preferably
below 4.0, e.g., from 2.5 to 3.8.) The stretched filamentary
material is then contacted with a hot liquid treating agent as
hereinbefore described with reference to FIG. 1, e.g., by passing
through a bath of such a treating fluid. Or, the treating agent may
be applied as illustrated in FIG. 2 and wherein the gelled yarn or
filamentary material is advanced over skewed rolls, the lower of
which is partly immersed in a trough of the hot treating agent.
The treated filamentary material is then washed as previously has
been described with reference to FIG. 1. For example, it may be
washed as illustrated in FIG. 2 using skewed rolls and a trough
containing water or other washing fluid as mentioned in the
preceding paragraph with reference to the application of the
treating agent. The treated and washed material is then dried as
hereinbefore described.
Another technique for activating the aqueous sulfuric acid
contained in the gelled filamentary material does not necessitate
the use of a hot liquid activating agent. This embodiment of the
invention, which is illustrated in FIG. 3, merely involves
heat-treatment of the acid-laden gelled structure. For example, the
gelled material after leaving the coagulating bath may be heated
while passing through air or other gaseous medium to a temperature
within the range of from about 40.degree.C. to about 100.degree.C.,
preferably not higher than about 90.degree. or 95.degree.C. This
technique is especially applicable when the gelled material has
been oriented by snubbing in the coagulating bath as previously has
been described. Alternatively, orientation by stretching as shown
in FIGS. 2 and 3 may be employed.
The procedure illustrated in FIG. 3 involves passing the shaped,
gelled structure such as a yarn bundle to several sets of skewed
rolls, the lower roll of the first set of which dips in a trough
containing spin-bath solution, more particularly aqueous sulfuric
acid having a concentration of H.sub.2 SO.sub.4 of about 50 weight
percent. The second set of rolls is operated at approximately the
take-up speed, its excess in speed over that of the first pair
providing the principal stretching factor for orientation of the
fibers. Washing is begun with passage of the yarn over the third
pair of rolls. Heat is applied by any suitable means to the yarn
while it is passing between the stretch and the wash rolls. For
example, heating may be effected with a radiant source of heat such
as electrical heating coils, infra-red lamps, etc. A further
increase in the dyeability of the final product is obtained by
heating the continuously moving filamentary material or the like
while it is in relaxed or untensioned state, or merely under a low
tension only sufficient to keep the filaments mvoing in a
continuous path. This can be done, for instance, by heating the
gelled material while the wash rolls are operating at a speed
somewhat below that of the stretch rolls.
The washing fluids and the washing techniques employed may be the
same as has been described above with reference to the embodiments
of the invention illustrated in FIGS. 1 and 2. Advantageously
washing is effected by applying the washing fluid to the upper (or
upon both upper and lower) of a pair of skewed rolls as the gelled
material, e.g., a continuous length of gelled filaments, is moving
in a helical path over the surfaces of the rolls; or, as
illustrated in FIG. 3, by having the lower of a pair of skewed
rolls partly immersed in a bath of the washing fluid.
The washed, gelled yarn or the like may be collected in gel state
on a take-up roll as illustrated in FIG. 3 and then subsequently
dried by any suitable means. Or, if desired, and as illustrated by
the phantom view in FIG. 3, the gelled yarn may be taken directly
from the wash rolls to drying means. The drying means may take the
form of, for example, heated drying rolls over which the gelled
yarn is continuously passed; or a drying oven, tube or hot slot
which is internally and/or externally heated by any suitable means
may be employed. Alternatively, drying may be effected merely by
exposure to air at ambient temperature for a prolonged period or
for a shorter period of time in warm air, after which the dried
yarn is collected on a take-up roll. Lubricating and/or antistatic
and/or other finishes may be applied to the yarn before, after or
both before and after drying the yarn or other shaped article.
From the foregoing description it will be noted that a solvent
solution or dope is prepared by dissolving a difficultly meltable
condensation polymer in a concentrated solution of sulfuric acid;
and that this dope is then coagulated into a gelled, shaped article
by extrusion through a shaped orifice into a coagulating bath
having a lower concentration of sulfuric acid than that used in
dissolving the polymer. At the face of the extrusion orifice(s) or
spinneret the concentration of H.sub.2 SO.sub.4 in the aqueous
sulfuric acid retained by the freshly coagulated shaped article,
e.g., filamentary material, is much higher than it is at its point
of exit from the coagulating bath. In practicing the present
invention optimum results are obtained in improving the
dye-receptivity of the final product by withdrawing the yarn or the
like from the bath at that point in the bath where the gelled yarn
contains a concentration of sulfuric acid that makes it effective
as a treating agent for chemically relaxing the yarn, more
particularly from 51 to 58 percent H.sub.2 SO.sub.4 and preferably
from 54 to 57 percent H.sub.2 SO.sub.4.
The addition of the treating or activating agent (inert heating
medium) used in practicing this invention to the gelled yarn at the
stage of acid concentration in the yarn that was mentioned in the
preceding paragraph makes the yarn more tractable. In other words,
it makes the yarn more amenable to the action of acid of the most
effective concentration from the standpoint of time and temperature
required to relax the yarn and thereby improve the dyeability of
the final product.
The process of the present invention is then, in effect, a
two-stage coagulation process wherein the initially bound coagulant
comprised of aqueous sulfuric acid is activated (reactivated) with
the result that the internal structure of the polymer is altered or
modified in a manner whereby the dye-receptivity of the final
product is improved; and, specifically, a more readily dyed
filamentary material or film is obtained.
In order that those skilled in the art may better understand how
the present invention can be carried into effect, the following
examples are given by way of illustration and not by way of
limitation. All parts and percentages are by weight unless
otherwise stated.
EXAMPLE 1
An extrudable solution having a Synchro-Electric viscosity at
25.degree.C. of about 5,000 poises, is made from the following:
Parts Polyhexamethylene terephthalamide 10.8 Sulfuric acid, 98
percent 83.0 Ammonium sulfate 6.2
The ammonium sulfate is added to the concentrated sulfuric acid at
room temperature (20.degree.-30.degree.C.), and the mixture is
stirred at the same temperature until the ammonium sulfate goes
into solution. The polyhexamethylene terephthalamide in finely
divided state is added to, and admixed with, the solution of
ammonium sulfate in the sulfuric acid. Mixing is effected at about
40.degree.-50.degree.C., and is continued until the polymer has
substantially completely dissolved, e.g., for about 2 hours. The
polymer component of this solution has an inherent viscosity (I.V.)
of about 2.0 measured as a solution of 0.4 gram of polymer per
deciliter of concentrated sulfuric acid solvent at 25.degree.C.
A dope bomb under nitrogen pressure is used in feeding the
above-described dope, after deaeration and filtration, through a
platinum spinneret with 40 holes of 0.10 mm. diameter into a liquid
coagulating bath consisting of sulfuric acid at 50.degree.C. This
coagulating bath is circulated through a rectangular trough formed
of clear poly(methyl methacrylate) by an external Jabsco pump
equipped with a bypass. Constant temperature in the coagulating
bath is maintained with a glass-enclosed electric heater and a
glass-enclosed thermoregulator.
Snubbing pins for effecting orientation of the gelled filamentary
material are positioned vertically in the bath from above. The pins
are comprised of a pair of one-fourth inch Alsimag rods held
five-eighths inch between centers in a 2-hole rubber stopper which
is fixed in a clamp above the bath. The stopper is rotated to
provide the desired snubbing angle, specifically 60.degree.,
70.degree., 80.degree. and 90.degree. in this example.
After passing through the coagulating bath for a distance of about
38 inches the oriented, gelled yarn is continuously removed from
the bath to a pair of skewed rolls (2 inches in diameter), the
speed of which is adjusted by means of Heller or Graham drive
systems. These rolls function primarily as guide rolls and as means
for drawing the yarn past the snubbing pins and out of the
coagulating bath.
After passing over the aforementioned skewed rolls, the yarn is
passed to a small stainless steel trough containing hot (about
120.degree.C.) polyethylene glycol having an average molecular
weight of 570-630, specifically CARBOWAX 600. The yarn is immersed
in this bath of treating or activating agent for a distance of 16
inches. The take-up speed is such that the yarn has a residence
time in the bath of about 0.8 second. The "control" yarns, that is,
gelled yarns containing aqueous sulfuric acid from the coagulating
bath, by-pass the above-described bath of polyethylene glycol.
Yarn to which the treating agent has been applied is led from the
treatment bath through a traversing mechanism to a perforated
Viscose-type take-up bobbin where it is wound at 30 meters per
minute under a cascade of hot tap water. The hot tap water removes
nearly all of the polyethylene glycol and most of the sulfuric
acid. The bobbin of yarn is then washed completely free of H.sub.2
SO.sub.4 by immersion for about 16 hours in cold, running, tap
water. Thereafter it is dried in air at room temperature.
Instead of washing and drying the yarn as described above, it may
be washed and dried by any other means or combination of means such
as those illustrated in FIGS. 1, 2 and 3 or by other means
described earlier in this specification.
The properties and dyeability measurements of treated and control
yarns obtained at various concentrations of H.sub.2 SO.sub.4 in the
coagulating bath and at various snubbing angles are given in Table
I. The dyeability values given in this table represent the percent
up-take on the weight of the fiber (i.e., owf) of the acid dye,
Alizarine Sky Blue BS-CF (C.I. No. Acid Blue 78). from an
"infinite" dye bath in 3 hours at 95.degree.C. and at a pH of 3. By
"infinite" dye bath it is meant that the amount of the dye is more
than 100 times the weight of the fiber.
It will be noted from the data given in this table that the
increase in dyeability of the treated yarn is from 2.2 to over 4.3
times that of the untreated yarn and with, in most cases, only a
minor decrease in fiber tenacity. Such results were wholly
unobvious and in no way could have been predicted. ##SPC2##
EXAMPLE 2
Essentially the same procedure is followed as described under
Example 1 with the exception that the polymer employed in making
the spinning dope is polyhexamethylene terephthalamide having an
I.V. of 1.9, and 11.6 percent thereof is used instead of 10.8
percent as in Example 1.
The dope is extruded through the above-described 40-hole spinneret
into a coagulating bath consisting of aqueous sulfuric acid having
an H.sub.2 SO.sub.4 concentration of 50.0 percent. The coagulating
bath is maintained at 50.degree.C., and the snubbing pins are
arranged at an angle of 70.degree.. The treating or activating
agent employed is a commercially available polyoxyalkylene polyol,
viz., PLURACOL V-7 (produced and sold by Wyandotte Chemicals
Corporation, Wyandotte, Michigan). It has an average molecular
weight within the range hereinbefore mentioned. The bath of
polyethylene glycol is maintained at a temperature of about
95.degree.C. instead of 120.degree.C. as in Example 1.
The properties and dyeability values for the control and the
treated yarns are tabulated below:
Filament Tenacity Elongation Dye* Up-take Yarn Denier g./d % % owf
Control 1.8 5.7 24 0.5 Treated 1.8 5.2 21 1.9 *An acid dye,
specifically Alizarine Sky-Blue BS-CF, as in Example 1.
When the control and treated yarns are dyed with a disperse dye,
specifically Eastone Red N-GLF (C.I. No. Disperse Red 35), the dye
up-take of the treated yarn is more than twice that of the control
yarn.
EXAMPLE 3
The same procedure is followed as described in Example 2 with the
exception that, instead of using snubbing pins in the coagulating
bath to orient the gelled yarn as in Examples 1 and 2, the said
pins are omitted and the yarn is oriented by stretching between
stretch rolls as is illustrated in FIG. 2. As there shown, the
coagulated yarn is led out of the spin bath under a guide roll to a
godet in the form of a pair of 2-inch rolls and then to a pair of
stretch rolls, also 2 inches n diameter. in stretch rolls are
operated at a peripheral speed sufficiently faster than the godet
so as to provide a draw ratio of about 3.0.
The stretch-oriented yarn is then treated with a polyoxyalkylene
polyol as in Example 2, washed and dried. A control yarn is
processed in the same way with the exception that the treatment
rolls shown in FIG. 2 are by-passed. The control and treated yarns
are then tested for dye-receptivity to both acid and disperse dyes
as in Example 2. With both acid and disperse dyes the dye up-take
of the treated yarn is from 2 to 3 times that of the control
yarn.
EXAMPLE 4
This example illustrates a technique for activating the aqueous
sulfuric acid retained by a gelled structure formed from a
condensation polymer of the kind used in this invention without
using an inert liquid activating agent. More particularly, the
procedure is essentially the same as that illustrated in FIG 3.
A spinning dope prepared as described under Example 2 is extruded
through a spinneret having 5,040 holes, each with a diameter of
0.10 mm., into a trough containing a spin-bath solution of 49.8
percent H.sub.2 SO.sub.4 at 45.degree.C. In the trough, the gelled
yarn bundle or tow is passed through a tube, having a length of 120
inches and an inside diameter of 3 inches, to the first of a set of
skew rolls as illustrated in FIG. 3, and thence to final take-up at
a speed of 50 meters per minute.
The first set of rolls dips into a trough containing spin-bath
solution having a concentration of 49.8 percent H.sub.2 SO.sub.4.
These rolls are operated at a peripheral speed considerably lower
than the take-up speed. The second set of rolls is operated at
approximately the take-up speed, except as indicated below. The
excess in speed of the second pair of rolls over that of the first
pair provides the principal stretching factor for effecting
orientation of the fibers. Washing is begun, as indicated in FIG.
3, with passage of the yarn over the third pair of rolls.
Application of heat, specifically by means of infrared lamps, to
the bundle of filaments as it passes between the stretch and wash
rolls increases the dye-receptivity of the filamentary material.
This improvement in dyeability is further enhanced by reducing the
wash-roll speed somewhat below the speed of the stretch rolls. The
temperature of the unwashed, stretched yarn is increased from about
25.degree.C. to about 40.degree.C. by the heat treatment.
In this example the dye up-take is measured in a finite bath
containing the acid dyestuff Alizarine Sky Blue BS-CF in the amount
of 4 percent by weight of the fiber sample. More detailed data and
results are given in Table II. ##SPC3##
Instead of using polyhexamethylene terephthalamide in making dope
solutions from which are produced filamentary materials and other
shaped articles having improved dye-receptivity in accordance with
the present invention, one may similarly make and treat shaped
articles of the polyisophthalamides, e.g., polyethylene
isophthalamide, polyhexamethylene isophthalamide, or of any other
difficultly meltable polymer of the kind with which this invention
is concerned and of which numerous examples have been given
hereinbefore both broadly and specifically.
It is to be understood that the foregoing detailed description is
given merely by way of illustration and that many variations may be
made therein without departing from the spirit of the
invention.
* * * * *