Note: Descriptions are shown in the official language in which they were submitted.
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This invention relates to zinc chelates of tereph-
thaloyl-terephthal/oxal copolyhydrazide, flame resistant
films and fibers from these chelates, and processes for their
preparation.
Terephthaloyl-terephthal/oxal copolyhydrazides have
already been described in U. S. Patent No. 3,748,298. They
are obtained by copolycondensation of terephthaloyl chloride,
terephthalic acid dihydrazide and oxalic acid dihydrazide~
Some metal chelates of polyisophthaloyl-isophthalhydrazide and
isophthaloyl-isophthal/terephthal-copolyhydrazide are also
known: A. H. Frazer and F. T. Wallenberger, Journal of
Polymer Science, Part A., Vol. 2, pp. 1825-1832(1964). With
the exception of zn2 and Cd2 chelates these products have
a pronounced color, are virtually impossible to work up
and dissolve only in concentrated sulfuric acid, and so only
while undergoing decomposition. Films of these polyhydrazide
chelates become brittle at temperatures above 350C and decom-
pose. In the case of copolyhydrazide chelates, only the film
chelated with mercury was found to be colorless in va_uum, but
in the presence o~ air it discolored ~uickly, in U.V~ light
it assumed a dark gray color and decomposed. While fibers
Dbtained from the metal chelates of these polyhydrazides or
copolyhydrazides had a higher melting temperature compared to
nonchelated material, their thermal stability is nok improved.
New copolyhydrazide metal chelates have now been
found which in terms of use characteristics are superior to
the above-described compounds.
The subject matter of the invention are 2inc
chelates of terephthaloyl-terephthal/oxal-copolyhydrazides
of a mole ratio of oxalic acid dihydrazide to terephthalic acid
dihydrazide structural units ranging between 19:6 and 6:19.
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The polymer substrate of the metal chelates of the
invention, terephthaloyl-terephthal/oxal-copolyhydrazides in
the indicated mole ratio of oxalic acid dihydrazide to tere-
phthalic acid dihydrazide structural units are readily soluble
in the polycondensation mix~ Using mole ratios outside the
indicated range yields high viscosity gels which cannot be
worked up. Fibers and films can be obtained in a known manner
from these copolyhydrazides by copolycondensation of tere-
phthaloyl chloride, terephthalic acid dihydrazide and oxalic
acid dihydrazide, e.g. according to the process described in
U. S. Patent ~o. 3,748,298 in N, N' dimethylacetamide/5 wt. %
lithium chloride and subsequent precipitation of the polymer
or molding of the polymer solution obtained in this manner.
The poly- or copolyhydrazides may also be dissolved according
to the process of German ~atent 1,694,328 in dilute aqueous
alkali hydrazides and transformed to films or fibers by casting
or spinning the alkaline solutions into acid precipitation
baths.
The metal chelates of the invention are obtained by
reaction of terephthaloyl-terephthal/oxal-copolyhydrazides
with a zinc salt solution.
The copolyhydrazide n7ay be a solid, e.g. a powder,
film, fabric, or granules in which form it can be treated in
an immersion bath with the solution of the zinc salt. It is
also possible e.g~ to spray the zinc salt solution onto the
solid copolyhydrazide. It is furthermore possible to react
dissolved copolyhydrazide e.g. as solution in dimethyl
acetamide/LiCl or as dilute aqueous alkali hydroxide solution.
Zinc salts suitable for reaction are inorganic and
organic salts. Examples are chlorides, nitrates, acetates, sul
fates and formates.
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Suitable for reaction with the copolyhydrazides are
solutions of the zinc salts in water, in dilute aqueous bases,
in organic solvents, e.g. dimethyl acetamide, n-methyl-
pyrrolidone, dimethyl formamide, pyridine and in aliphatic
amines, as well as in mixtures of cited solvents. Especially
suitable are solvent mixtures of water and ammonia as well as
of water and aliphtatic amines.
The zinc uptake is influenced by a number of
parameters' however, process conditions which are particularly
suitahle for the preparation of a special copolyhydrazide
chelate can be readily determined by a series of simple tests.
The following influence factors were determined:
1. The amount of zinc which can be taken up by
the polymer depends, provided all other para-
meters are constant, to a minimal degree upon
the chemical composition of the polymer.
2. Increasing the concentration of the zinc salt
in the treatment bath will, for the same treat-
ment time, increase the zinc uptake.
3. An increase in temperature will as a rule in-
crease the rate of zinc uptake. However, in
most cases zinc uptake proceeds speedily
enough so that treatment of the copolyhydrazide
with the zinc salt solutions is advantageously
carried out at room temperature.
4, Zinc uptake is very much a function of the pH
of the zinc salt solution. It increases with
increasing pH. It is preferred to carry out
the chelation reaction at a pH of 11-12 or
higher.
5. The rate of zinc uptake is greater for high
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swelling polymer material~ Swelling can be
produced either by the solvent of the zinc salt
solution and/or by another swelling agent.
A preferred treatment solution is a solution of
zinc chloride in a~ueous 2N. ammonium hydroxide. The metal
content of the chelates ranges from very small ~antities,
e.g. 0.1 wt.%, to the saturation limit.
The copolyhydrazide chelates of the invention exhibit
useful properties. They are practically nonsoftening and thus
relatively dimensionally stable in the presence of thermal
influences. They are yellow, whereas nonchelated copolyhy-
drazides are white. The chelates can be molded. They represent,
furthermore, valuable metallic compounds, which can be used
where corresponding low molecular compounds cannot be used,
e.g. because of their solubility. This is often the case with
catalytic processes~
With a zinc content of at least 5 wt. %, the copoly-
hydrazide chelates of the invention are flame resistant and
the flame resistance increases with increasing zinc content.
With a zinc content of about 6 to 8 wt. % and higher, the
products are even nonflammable. Based on these characteristics,
the copolyhydrazide chelates of the invention are suitable
for the production of film and fiber materials.
Another subject matter of the invention are zinc-
containing terephthaloyl-terephthal/oxal-copolyhydrazide
materials obtained by reaction of the above-described tere-
phthaloyl-terephthal/oxal-copolyhydrazide zinc chelate with
an oxalic acid solution. Solvents for oxalic acid are in part-
icular, water and water/alcohol mixtures. The concentration
of the oxalic acid solution is preferably 0.2 to 3 wt. %.
The reaction is carried out at temperatures of 10 to 80C,
reaction time is preferably 15 to 90 minutesO
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During oxalic acid treatment, the chelates are
gradually de-chelated and lose their yellow color. The formerly
chelate-like bonded zinc is converted to a low solubility com-
pound which remains monodispersely distributed in the polymer.
During oxalic acid treatment, the products lose part
of the zinc. With previously dried chelates as starting
material, zinc loss is comparatively small, i.e. treatment with
oxalic acid can be continued until the product has turned
absolutely white. Dechelation progresses much more rapidly
with freshly precipitated and chelated copolyhydrazides, to pre-
vent large zinc losses, intermediate setting is recommended,
i.e. brief drying of the material to be aftertreated, for
instance at 40C in vacuum for to hours. Under these
conditions, it is also possible with freshly prepared copoly-
hydrazide to achieve decoloration without significant zinc
loss. These oxalic acid-treated products are also eminently
suitable for the production of film and fiber materials.
They are likewise flame-resistant or flameproof. Compared
with zinc chelates, they have in addition the advantage of
being white.
The flame resistant films and fibers of the above-
described materials are obtained according to the invention by
reacting films or fibers of terephthaloyl-terephthal/oxal
copolyhydrazides having a mole ratio of oxalic acid dihydrazide
to terephthalic acid dihydrazide structural units ranging from
19:6 to 6:19 with solutions of one or more inorganic or organic
~inc salts, followed under certain conditions by reaction with
an oxalic acid solution. For the above-described zinc-contain-
ing terephtaloyl-terephthal/oxal copolyhydrazide materials, use
is preferably made hereby of 0.2 to 3 wt. % of oxalic acid
solutions, reaction temperatures of 10 to 80C and reaction
time of 15 to 90 minutes.
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The process whereby chelation ls performed during
the molding of a copolyhydrazide solution is less suitable for
the production of chelate films and fibers, since it yields
molded articles of low strength. It is therefore recommended
to carry out the chelation in a separate, subsequent chelation
bath.
The flame resistant or nonflammable chelated fibers
obtained according to the process of the invention exhibit
good textile properties. They can be processed without problems
to yarns, staple fiber blend yarns, woven fabrics, knitted
fabrics, nonwovens, etc~ Generally, both strength and elonga-
tion data of filaments with a metal content of about 14 to
16 wt. % are only about 20% lower than those of the correspond-
ing, nonchelated copolyhydrazide fibers. Fibers with a low
metal content exhibit strengths and elongations which are only
slightly lower than those of the corresponding nonchelated
copolyhydrazide fibers. Dry strengthc; of up to 30 cN/tex
and dry elongations to 20% were obtained for flameproof copoly-
hydrazide chelate fibers.
Since it is highly desirable to obtain the flame-
resistant and, under certain conditions, flame-proof zinc
chelate films and fibers in a white form, the process variant,
whereby chelated films or fibers are aftertreated with a
solution of oxalic acid, is a preferred version of the invention
process. The resulting films and fibers exhibit likewise
very good, in some cases, better textile properties than pro-
ducts not receiving such aftertreatment, especially in terms
of flame resistance.
Compared with known polyhydrazide or copolyhydrazide
chelates, the products of the invention are distinguished by
their flame resistance, their good physical properties as
well as by their relatively light coloration.
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Example 1
Dissolve in a 2 liter plane ground reaction vessel
50 grams dried lithium chloride and 1 liter anhydrous dimethyl
acetamide. Add to the solution 0.15 mole ~17.7 gram) oxalic
acid hydrazide and 0.05 mole (9.75 g) terephthalic acid hydra-
zide. After cooling the solution to 273K, add under vigorous
stirring 0.2 mole (40.6 g) terephthaloyl chloride in powder
form. After 15 minutes, the cooling bath is removed and the
reaction solution is allowed to heat up gradually to room
10 temperature. After 1 hour, the hydrochloride resulting from
the polycondensation is partially neutralized with 10 g
LiOH . H2O in 5 ml water, the reaction mass which has become
hi~hly viscous is converted after stirring for 12-16 hours
into a homogeneous~ high viscosity solution. Copolyhydrazide
content is 5%. Inherent viscosity is 6.5 (0.5 gram/dl
DMA + 5% LiCl at 298K). The solution was subsequently
poured into water. The precipitated copolyhydrazide was
washed with alcohol and dried.
Subsequently, the copolyhydrazide was reacted at
20 room temperature (22C) with an aqueous in zinc chloride
solution, which had previously been adjusted to pH 12 with
aqueous ammonia. After 3, 6 and 18 hours, respectively, the
copolyhydrazide had taken up 12, 18.1 and 18.8 wt. % zinc.
Examples 2 to 4
According to the above-described method, three
different terephthaloyl-terephthal/oxal copolyhydrazides were
prepared from 50 mole % terephthaloyl chloride as well as from
oxalic acid dihydrazide and terephthalic acid dihydrazide in
a molar ratio of
38:12 (I)
25:25 (II)
12:38 (III)
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and treated for 17 hours with the zinc chloride solution.
As shown in the following table, the metal uptake
depends only to a minor extent upon the composition of the
copolyhydrazide.
Example No.Copolyhydrazide Zinc Content (wt.%)
2 I 21.1
3 II 18.8
4 III 18.8
Example 5
10- A 5% polycondensation solution obtained according to
Example 1 from 50 mole % terephthaloyl-terephthal hydrazide
and 50 mole % terephthaloyl-oxal hydrazide structural units in
dimethyl acetamide/lithium chloride of an inherent polymer
viscosity of 8 is deaerated under vacuum and used as spinning
solution. The polymer solution is spun through a spinneret with
24 orifices, each having a diameter of 250 microns, into dis-
tilled water at a draw off rate of 35 meter/min. without drawing.
The filaments are washed on a spool in a pressure wash. The
running yarn is dried in heated air about 643 ~Ko Draw off
rate lS 15 m/min. The dried filaments have a denier of 210-218
dtex, strength of 26.5 cN/tex and an elongation of 16%.
The dry copolyhydrazide filaments were knitted and
chelated. Chelation is accomplished at room temperature in 1
molar aqueous zinc chloride solution adjusted to pH 12 with
ammonia. After treatment for 6 hours in the chelation bath,
the knitted material is removed and washed with ample distilled
water to neutral reaction of the wash water. Zinc content of
the knit is 18.3%.
The air-dried knit is then aftertreated in a solution
of 1% oxalic acid in water/methanol 1:1 for about 1 hour until
the fabric has become colorless. After repeated washing with
_ 9 _
water, the knit is dried at 313-323K in the circulating air
oven. The colorless knit material has a zinc content of 15~6%.
Examples 6 to 11
To characterize the flame behavior of zinc compounds
according to the invention, copolyhydrazides of examples 2 to
4 were prepared according to the method described in example 1,
then as described in example 5 spun, knitted, and chelated.
Part of the knit material was aftertreated with a 1 wt. %
aqueous oxalic acid solution at ~0C. Untreated and after-
treated specimens were subjected to the LOI test.
The LOI (Limiting Oxygen Index) is defined as the
oxygen content (in %) of an oxygen-nitrogen mixture in which
a vertical specimen ignited at the top will just burn. The
LOI was measured according to ASTM-D 2863 making use of a
measuring instrument manufactured by Stanton Redcroft, England.
Furthermore, the knit materials were subjected to
the burning test according to DI~ 53 906 (vertical method).
For control, a nonchelated copolyhydrazide knit
material was also tested.
The results are compiled in the fo]lowing table.
In the column "burning test" the plus sign indicates that the
specimen did not ignite after being exposed for 15 seconds to
a flame. The minus sign indicates that within this time the
samples ignited and gradually burned. The degree of flame
resistance of these specimens can be derived from the listed
LOI values.
It follows from the table that according to the LOI
test the three untreated copolymer knits are not significantly
different in burning behavior. Chelation significantly in-
creases the flame resistance of the knits. Artertreatment of
the chelated knits to achieve a white color leads to a loss of
metal and as a rule causes the LOI to decline somewhat.
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Example 12
A polycondensation solution of 25 mole % oxalic
hydrazide, 25 mole % terephthalic hydrazide and 50 mole %
terephthaloyl chloride in dimethyl acetamide/LiCl of a
polymer content of 5.5% is deaerated under vacuum. The
high viscosity copolymer solution is evenly applied with a
spreader onto glass plates to a thickness of 0,25 mm, After
drying for 5 hours in a vacuum drying oven at 348 K and
0.18 bar, the film is stripped under water from the glass
plate. The film is dried for 2 hours at room temperature
in a metal frame, the film is then introduced into a 10%
zinc chloride solution adjusted with ammonia to pH 12,
After 1.5 hours the film is washed with distilled water,
mounted in a metal frame and dried in the vacuum drying
oven. The result is a transparent yellow film having a
zinc content of 21%,
By way of aftertreatment, the zinc chelated film
is dried for only one hour at 313-348" K and subsequently
treated in a bath with 1% oxalic acid solution at 333 K
(about 10 minutes), until the film has become colorless.
The film is washed with distilled water to neutral reaction
of the wash water and then dried in a frame in the vacuum
drying oven. The result is a colorless film with a zinc
content of 18%.
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