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Copolymers and Fibers from Vinylidenedicarbonitrile.

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Copolymers and Fibers from Vinylidenedicarbonitrile [*I
BY B. S. SPRAGUE, H. E. GREENE, L. F. REUTER, AND R. D. SMITH
CELANESE FIBERS COMP., CHARLOTTE, N. C., U. S. A.
Vinylidenedicarbonitrile ( Vinylidene cyanide) on free radical catalyzed copolymerization
shows a much stronger tendency to form I :I alternating copolymers than acrylonitrile.
While bulk poly(vinylidene cyanide) fails to crystallize, despite its molecular symmetry,
several alternating copolymers are readily crystallizable, notably those containing butadiene,
isoprene, isobutylene, or vinylidene chloride. Fibers have been prepared from a number
of the higher melting copolymers and examined for physical properties. Fibers from
the vinyl acetate and vinyl chloride copolymers show exceptional elastic behavior
both when dry and wet The fiber from the vinylidene cyanidelvinyl acetate alternating
copolymer (Darvan@ nytril fiber) is only moderately oriented and is characterized by
exceptional softness and excellent elastic recovery and resilience, both when dry and wet.
Introduction
Vinylidenedicarbonitrile (vinylidene cyanide) was first
synthesized in the laboratories of the B. F. Goodrich
Company in 1947 [l], and its synthesis and properties
have been described by Ardis and co-workers [2]. It is a
colorless liquid which boils at 150°C and freezes at
9 "C; for comparison, acrylonitrile boils at 89 "C and
freezes at -82°C. The monomer is rather unusual in
that it will polymerize readily by an ionic mechanism in
the presence of very weak bases [31. Any source of
hydroxyl ion causes almost instantaneousconversion into low molecular weight poly(viny1idene cyanide). If
properly stabilized, however, the monomer may be
stored for long periods of time.
This paper will discuss the structure and properties of a
series of copolymers prepared from vinylidene cyanide,
and of fibers prepared from these copolymers. Appropriate comparisons will be made with acrylonitrilecopolymers. Properties of a vinylidene cyanidelvinyl acetate
alternating copolymer, and the fiber Darvan will be
considered in some deteil.
@
(r1xr2), as proposed by Mayo and Lewis [5], has been
used to determine the tendency to form alternating
copolymers, as shown in Table 1. As the product of the
reactivity ratios approaches zero, the structure approaches perfect alternation, and conversely, as their
product approaches unity, the copolymer approaches a
Table 1. Reactivity ratio products of copolymer systems
x r2 with
Vinylidene cyanide
r1x r2 with
5 x 10-6
I x 10-5
7.7~
10-5
5 . 9 10-5
~
5 . 9 10-5
~
1 . 4 1~0 - 4
1 x 10-2
9~ 10-3
2x 10-2
6.1 x 10-2
3.3x 10-1
4 . 2 10-1
~
2 . 4 10-1
~
1 x 10-2
11
Comonomer
Styrene
Butadiene
2-Chlorobuta- 1,3-diene
Vinylidene chloride
Vinyl acetate
Methyl methacrylate
Vinyl chloride
Acrylonitrile
r1xr2 + 1 : random
r l x r l + 0: alternating
completely random structure. The strong tendency of
vinylidene cyanide to form alternating polymers with
common mmonomers is quite apparent.
I
Copolymerization Characteristics
The free radical catalyzed copolymerization of vinylidene
cyanide with other monomers gives a striking demonstration of the unusual behavior of this material as
compared to acrylonitrile [4]. With many comonomers,
vinylidene cyanide shows a strong tendency to form
alternating copolymers,rather than the random copolymers associated with the free radical copolymerization
of acrylonitrile. The product of the reactivity ratios
[*] Lecture at the Meeting of the Gesellschaft Deutscher Chemi-
ker, Section "Kunststoffe und Kautschuk", on April 10th. 1962
at Bad Nauheim (Germany).
[ I ] H . Gilbert, U.S.Patent 2514387 (1950).
[2] A . E. Ardis et al., J. Amer. chem. SOC.72, 1305 (1950).
[3] H . Gilbert et al., J. Amer. chem. SOC. 76, 1074 (1954).
[4]H . Gilbert et al., J. Amer. chem. SOC. 78, 1669 (1956).
Angew. Chem. internat. Edit. 1 Vol. I (1962) I No. 8
I
I
t
"0
TiJiJ
I
I
I
20
LO
60
80
101
Fig. 1. Composition of copolymers from vinyl acetate and (-)
vinylidene cyanide or (- -) acrylonitrile.
Ordinate: Mole % vinyl acetate in polymer
Abscissa : Mole% vinyl acetate charged
-
[5] F. R. Maya and F.
(1944).
M.Lewis, J. Amer. chem.
SOC. 66, 1954
425
The tendency of vinylidene cyanide to form copolymers
of equimolar composition is also demonstrated by the
relatively constant composition of vinylidene cyanidel
vinyl acetate copolymers over a very wide range of
monomer ratios in the starting mixture. This contrasts
strongly, for instance, with the behavior of the acrylonitrile/vinyl acetate system, where the polymer's composition is very dependent upon the monomer ratio
charged (Figure 1).
Gilbert [3] has ascribed the unusual polymerization
properties of vinylidene cyanide to polarization of the
n-electrons of the double bond and the C=N triple
bond (I).
(d)
(C)
Fig. 2.
X-Ray diffraction diagrams of bulk homopolymers and
drawn fibers
a) Bulk poly(viny1idene cyanide)
b) Bulk poly(acrylonitri1e)
c) Poly(viny1idene cyanide), drawn film
d ) Poly(acrylonitrile), drawn fiber
Structure and Physical Properties of Copolymers
been described by Saum [7] for alkyl cyanides and dicyanides (11).
The symmetry of vinylidene cyanide might be expected
to result in strong crystallization of the homopolymer,
but surprisingly, X-ray diffraction powder diagrams
indicate that poly(viny1idene cyanide) is less ordered
than poly(acrylonitri1e) (Figure 2). Even when highly
drawn fibers or films are made from the homopolymers,
the poly(viny1idene cyanide) behaves similarly to poly(acrylonitrile), displaying only high lateral order but no
crystallinity, as indicated by the lack of reflections other
than equatorial (Figure 2) [6]. It is probable that the low
degree of crystallinity of poly(viny1idene cyanide) polymer and fiber results from the inability of the molecules
to arrange themselves with sufficient 3-dimensional
regularity, owing to the occurrence of numerous ex-
CEN
8-
s+
N=C
JI
-c-c-
N=C
The ability to crystallize seems to be improved considerably with certain alternating copolymers. A series
of such copolymers and their softening or crystalline
melting points are given in Table 2. Comonomers such
as butadiene, isoprene, chloroprene, and piperylene
(which react by 1,4-trans additions), isobutylene and
Table 2. Properties of copolymers of vinylidene cyanide
Comonomer
Mole %
comonomer
in the copolymer
Styrene
Propylene
Isobutylene
Butadiene
50
50
50
50
270
Chloroprene
Isoprene
50
50
155
180
Piperylene
Vinyl chloride
Vinylidene chloride
Vinyl acetate
Methyl methacrylate
Vinyl formate
50
50
50
50
55
50
110
220
205
180
130
175
Crystallizable
tremely strong intermolecular attractions, which set up a
highly stable random network of chains, leading to an
extremely high glass transition temperature. It is
believed that the intermolecular attractive forces concerned are principally dipole-pair bonds such as have
[ 6 ] C. R . Bohn, J. R. Schaefgen, and W. 0. Statton, J. Polymer
Sci. 55, 531 (1961).
426
Softening or
melting pt.
I"Cl
190
110
115
Soluble in
ketones
ketones
ketones
hot
dimethylformamide
dimethylformamide
hot
dimethylformamide
ketones
dimethylformamide
dimethylformamide
dimethylformamide
ketones
dimethylformamide
very high
high
high
low
good
good
good
very poor
low
low
poor
very poor
low
high
high
high
high
high
good
poor
poor
poor
exceUent
poor
vinylidene chloride give rise to strong crystallinity in
the bulk copolymer, whereas unsymmetrical comonomers such as styrene, vinyl chloride, and vinyl acetate
do not (see Figures 3 and 4). It appears that overall
symmetry of the copolymer molecule, together with
some modification or reduction of the tendency of
[7] A . M . Saum, J. Polymer Sci. 42, 57 (1960).
Angew. Chem. internat. Edit. 1 VoI. I (1962) I No. 8
It is of interest that the inclusion of a methyl group, as in
copolymers with isoprene or piperylene, or a chlorine
substituent, as with chloroprene copolymers, drastically
modifies the crystalline melting point, even though sufficient
stereoregularity is maintained to provide a crystallizable
polymer.
Even with the non-crystallizable copolymers, very high
softening points are attained as compared to the corresponding copolymers based on acr) lonitrile. For example, the
vinylidene cyanide/styrene copolymer softens at 190 'C, and
the vinylidene cyanide/vinyl acetate copolymer at 180 "C,
whereas the corresponding copolymers based on acrylonitrile
are rubbery above 60-80 "C. The fact that copolymers with
methyl methacrylate and vinyl formate soften at a somewhat
lower temperature than the vinyl acetate copolymer is
unexpected; this suggests that some interaction may occur
between the cyanide group and adjacent group on the
same chain.
(3
(C)
Fig. 3. X-Ray diagrams of symmetrical or stereoregular
copolymers of vinylidene cyanide
a) Copolymer with butadien
b ) Copolymer with vinylidene chloride
c) Copolymer with isoprene
d) Copolymer with piperylene
Fibers from Vinylidene Cyanide Copolymers
While all of the copolymers discussed above are potential fiber formers, those with melting or softening points
lower than 170-180 "Chave been eliminated as being of
little practical interest. In addition, poor melt stability
and difficulty in obtaining sufficiently concentrated
solutions for satisfactory solution spinning resulted in
elimination of the butadiene and isoprene copolymers,
while low yields eliminated the styrene copolymer from
serious consideration. Fibers have been spun from the
copolymers of vinylidene cyanide with vinyl chloride,
vinylidene chloride, and vinyl acetate by solution techniques, and from the vinylidene cyanidelbutadienel
styrene terpolymer by a modified melt spinning technique and assessed for mechanical properties, as shown
in Table 3. Typical properties of a polyacrylonitrile fiber
are listed for comparison.
(b)
(a)
Fig. 4. X-Ray diagrams of unsymmetrical copolymers of vinylidene
cyanide
a) Copolymer with vinyl acetate
b) Copolymer with styrene
vinylidene cyanide to form dipole-pairbonds, is required
to promote crystallization in the bulk polymer. In no
case do the corresponding 50 % acrylonitrilecopolymers
display crystallinity, although some lateral order is
observed with the acrylonitrile/vinyl chloride copolymer
in fiber form. The butadiene/vinylidenecyanide
(Dyne1@)
copolymer has an exceptionally high melting point
While these small scale spinning experiments did not
yield optimum fibers, the data obtained were sufficiently
typical to indicate the most desirable copolymers for
further study. In spite of the crystallizability of the
Table 3. Mechanical properties of fibers prepared from copolymers of vinylidene cyanide
~~
Mole %
comonomer
in the
copolymer
Comonomer
Butadienelstyrene
Vinylidene chloride
Vinyl chloride
Vinyl acetate
Poly(acrylonitri1)
40/10
50
50
50
100
Tenacity
Idden. 1
Elong.
I %I
Elastic recovery from
3 % elongation [*I
Modulus of
elasticity
[g./den.1
TSR[%]
3.0
2.8
1.6
2.0
2.7
14
6.5
19
30
30
40
34
45
34
47
51
55
79
70
64
dry
WR[%1
I
wet
TSR[%I
I WR[%I
37
43
28
33
45
35
25
68
70
35
38
34
16
-
-
[*I Method of Beste & Hoffman
TSR-tensile strain recovery
WR-work recovery (resilience)
(270 "C), in contrast to the corresponding copolymer
based on acrylonitrile. The latter is a rubber at room
temperature, as are the other acrylonitrile/dienecopolymers. A 50/40/10 vinylidene cyanide/butadiene/styrene
terpolymer also crystallizes but has a significantly lower
melting point. X-ray diffraction studies indicate that its
crystallinity is associated only with the vinylidene
cyanidelbutadiene portions of the molecule.
Angew. Chem. internat. Edit.
/
Vol. I (1962)1 No. 8
vinylidene cyanidelvinylidene chloride copolymer. the
fiber elongation is poor and its elastic behavior is not
outstanding. In contrast, fibers from the vinylidene
cyanide/vinyl chloride and vinylidene cyanide/vinyl
acetate copolymers show remarkably good elastic behavior both when dry and wet. In fact, the wet elastic
behavior is so important with respeLi to end-use performance that these two copolymers are by far the most
427
interesting for further study. It has been found that the
vinyl chloride copolymer is somewhat unstable at high
temperatures, since it tends to lose HCl. Accordingly,
detailed examination of fiber properties will be limited
to the vinylidene cyanidelvinyl acetate copolymer.
Fiber from Vinylidene Cyanide/Vinyl
Acetate Copolymer
The fiber from the 1 : 1 alternating copolymer of vinylidene cyanide and vinyl acetate has been studied extensively in comparison with other acrylic and modified
acrylic fibers [*I.
The specific fibers utilized for comparison are identified
in generic terms, as follows:
a) Nytril - a fiber composed of a 1 : 1 alternating copolymer of vinylidene cyanide and vinyl acetate.
b) Acrylic I - a fiber composed of acrylonitrilewith less
than 10 % polar vinyl comonomers - cationic dyeable.
c) Acrylic I1 - a fiber composed of acrylonitrile with not
more than 1 0 % polar vinyl comonomers - acid
dyeable.
d) Modacrylic - a fiber composed of an approximately
1 :1 copolymer of acrylonitrile and vinyl chloride.
The nytril fiber, produced by a solution spinning and
drawing technique, has only low orientation and no
crystallinity, as seen in the X-ray diagram of Figure 5,
rn
(a)
Table 4. Mechanical properties of fibers
nytril
nytril
steam
set
acrylic
I
acrylic
I1
modacrylic
Tenacity [g./den.]
23 "C,6 5 % r . h .
23 "C,wet
70 O C , wet
2.2
1.8
1.5
2.1
1.8
1.4
3.0
2.3
0.7
2.4
1.8
0.9
3.0
3.0
2.1
Elongation [ %]
23 "C, 6 5 % r. h.
23 "C, wet
70 "C. wet
26
30
31
3536
40
33
40
77
42
44
65
36
37
50
Modulus [g./den.]
23 "C, 6 5 % r. h.
23 "C, wet
70 "C, wet
25
20
I1
22
17
10
46
41
27
26
A
A
35
28
16
Energy to uncrimp
Ig.xcm./den.xcm.] x 1 0 4
1.8
0.8
3.6
5.4
4.0
quate for textile applications, and under hot wet conditions is distinctly superior to that of the acrylics. The
initial relatively low level of the modulus of elasticity,
which is, however, maintained to a high degree in the
presence of heat and moisture, as well as the low level of
uncrimping energy, contributes to the exceptionally soft
feel of the nytril fiber.
The high resistanes of the fiber to hot water may also
be noted in Figure 6, where modulus is plotted as a
(b)
Fig. 5. X-Ray diffraction of (a) nytril and (b) acrylic I fibers
the diffraction being produced by a small amount of
lateral order only. Acrylic I, in contrast, has somewhat
higher orientation, although it too displays only lateral
order. This may be noted by observing the absence of
any non-equatorial diffraction in Figure 5. The specific
gravity of the fiber is 1.21 as compared to 1.19 for
acrylic I and 1.31 for the modacrylic fiber [8]. The
nytril fiber becomes sticky at 170°C compared to
235 "Cfor acrylics I and 11. The modacrylic fiber shrinks
drastically at temperatures above 135 "C[9].
Other physical properties of the nytril fiber are compared with those of acrylic and modacrylic fibers in
Table 4.
The strength of the nytril fiber, while somewhat lower
than that of the acrylic and modacrylic fibers, is ade-
[*I The fiber, known commercially as Darvan@,was developed
by the 3. F. Goodrich Co. However, the rights to the fiber are
now owned by the Celanese Corporation of America, and the
data cited below were obtained through the joint efforts of
Goodrich and Celanese personnel.
[8] E. R. KasweN: Textile Fibers, Yarns, and Fabrics. Reinhold,
New York 1953, p. 11.
[9] See [8], p. 112.
428
Fig. 6. Modulus temperature relationship (measured at 1 % strain)
- 0 -0 - wet nytril fiber
-m-mdry nytril fiber
-A-A- wet acrylic fiber I
dry acrylic fiber I
Ordinate: Modulus of elasticity [g./den.l
Abscissa : Temperature [ "CI
-v-v-
function of teniperature both dry and wet, in comparison
to acrylic I. These data suggest the presence of a major
wet glass transition temperature (Tg) in the region of
50°C for acrylic I, but no detectable wet glass transition temperature below 100" for the nytril fiber.
Treatment of the nytril fiber in saturated steam reveals
that considerable shrinkage sets in at temperatures of
120-130 "C, indicating the presence of a wet glass
transition temperature in this region. This is reinforced
by the fact that dye penetration (to be discussed below)
is highly accelerated by pressure dyeing above 120 "%.
Angew. Chem. internat. Edit.I Vol. 1 (1962)1 No.8
The setting of impressed configurational geometry such
as crimp can be achieved best by treatment in steam
at a pressure of 20 lbs./sq. in. (127 "C), in contrast to
the acrylic and modacrylic fibers, where the low wet
glass transition temperature allows configurational
A
0
I
I
I
I
I
1
2
3
4
5
IA201.91
lniolll
Fig. 7. Effect of steam setting on the stress-strain behavior of nytril
fiber
Curve A : untreated
Curve B: steam set
Ordinate: Stress [g./den.]
Abscissa : Strain [%I
setting to be effected during the drying of wet fiber. This
hot setting procedure also provides some relaxation of
internal stresses in the nytril fiber, resulting in a
slightly "softer" stress-strain curve (Figure 7). The
setting procedure has a considerable effect on the elastic
Fig. 9. Proportion of strain energy immediately recoverable
-A-Anytril fiber
-D-mnytril fiber, steam set
-0-0silk
-v-v- wool
-6-4- acrylic fiber I
Ordinate: Energy index of elasticity
Abscissa : Extension [%I
behavior of the fiber, as seen in Table 5 ; it improves
both work recovery (resilience) and permanent set well
above the level of acrylic1under all conditions examined.
This elastic behavior is one of the most important
attributes of the nytril fiber, resulting in retention of
Table 5. Elastic properties of nytril, acrylic I, and modacrylic fibers [*I
I
23 "C, 5 6 % r. b .
23 "C, wet
70 "C, wet
43
[*I ASTM method D-l774-61.T, 5 % Extension.
0
rn
I
I
I
I
I
1
2
3
4
5
Fig. 8. Proportion of strain immediately recoverable
-A-Anytril fiber
-m-mnytril fiber, steam set
silk
-0-0-
-V-T
-
-*-*-
WOO1
acrylic fiber I
Ordinate: Immediate elastic deflection [%I
Abscissa : Extension [%I
Angew. Chem. internat. Edit.
Vol. I (1962) 1 No. 8
20
WR - work recovery
33
17
PS - psrmanent set
shape and appearance throughout the wearing and
laundering of garments. The elastic behavior has also
been examined by sonic modulus techniques, using
methods developed by Hamburger [lo]. The data shown
in Figure 8 indicate the proportion of strain immediately
recoverable, while the energy available for immediate
recovery from strain is given in Figure 9. The nytril
fiber is seen to compare very favorably with silk and
wool, in contrast to the acrylic fiber. Steam setting
improves the performance slightly.
Dyeing behavior of the nytril fiber is a broad subject
and will be discussed only briefly here. The fiber displays affinity primarily for disperse (non-ionic) dyes and
is only penetrated with difficulty without the use of
carriers or elevated pressure and temperature. In fact,
such conditions must be used to build up heavy shades.
As discussed above, it appears likely that the improvement in dyeability experienced under pressure above
120°C results from a major increase in the diffusion
rate which is brought about by exceeding the wet glass
transition temperature. The mechanism by which
[lo] W. 1.Hamburger er al., Textile Res. J. 22, 695 (1952).
429
carriers promcite disperse dyeability of the nytril fiber
at 100 "C is not completely understood but may involve
an increase in both affinity and diffusion rate. Typical
carriers such as methyl p-toluate and o-phenylphenol
combine strongly with many disperse dyes and, when
inside the fiber, may act as temporary dye sites. In
addition, these compounds are strong solvating agents
for sites of dipole interaction and thus may be expected
to lower the wet glass transition temperature to some
degree, resulting in improved diffusion rate.
While a discussion of the properties and performance of
fabrics made from Darvan@nytril fiber is beyond the scope
of this paper, it should be stated that the postulates concerning performance which have been derived from fiber
properties have been borne out by extensive fabric trials. Soft
texture, resilience, shape retention throughout wearing and
laundering, and a high degree of resistance to wrinkling
have been experienced with such fabrics.
Relationship of Properties to Fiber Structure
The outstanding features of softness,elasticity,resilience,
and resistance to moisture displayed by the nytril fiber
may be traced directly to its chemical constitution and
fine structure. The relatively low degree of orientation
and lateral order, together with the large number of
points of intermolecular attraction provided by the
polarized cyano groups, result in a strong, flexible
network of molecules. This, in turn, is responsible for
the soft, resilient texture of the fiber. The strength of
the dipole-pair intermolecular bond, which is of the
order of 8-10 kcal./mol. for alkyl cyanides [7] and
which is probably much higher for vinylidene cyanide,
owing to resonance, together with the large number of
such bonds, probably accounts for the high degree of
elastic recovery, the good wrinkle resistance, and the
relative insensitivity to hot water. These same factors,
of course, would tend to increase the wet glass transition
temperature and reduce the dye diffusion rate.
I t is impossible to give individual credit for specific aspects
of the work in aproject of such broad scope. The staffs of
the Research Center, B. F. Goodrich Co. Brecksville,
Ohio; the Development Center, B. F. Goodrich Chemical
Co., AvonLake, Ohio; the Summit ResearchLaboratories,
Celanese Corporation of America, Summit, N. J. ; and
the Application and Product Development Dept., Celanese
Fibers Co., Charlotte, N . C . have all made significant
contribi~tionsto the work reported here.
Received, April 2nd. 1962
[A 201/33 IE]
Pyrrolidone, Capryllactam and Laurolactam as new Monomers
for Polyamide Fibers [*]
BY DR. K. DACHS AND DR. E. SCHWARTZ
BADISCHE ANILIN- & SODA-FABRIK A.G., LUDWIGSHAFEN AM RHEIN (GERMANY)
The industrial production of capryllactam (I-azacyclononan-2-one) and of laurolactam
(I-azacyclotridecan-2-one)starts with cyclization of acetylene or butadiene to give cyclooctatetraene or cyclooctadiene, or cyclization of butadiene to give cyclododecatriene.
Further steps are: oxidation of the cyclic hydrocarbon to the ketone, formation of the
oxime, and rearrangement of the latter with sulfuric acid. Pyrrolidone can be prepared
from acetylene and formaldehyde by way of butyrolactone. The behavior of the lactams
during polycondensation is described and the properties of the resulting fibers are compared
with those of the known polyamide fibers.
I. Introduction
Of the great number of aliphatic homopolyamides
known, 33 of which are listed in Table 1, only two are
of substantial importance in the fiber industry. Apart
from Nylon-6.6, the polyamide made from hexamethylenediamine and adipic acid (production in 1961, approx.
350000 tons), Nylon-6, a polyamide made from E caprolactam, is gaining importance. The ease of polymerization of caprolactam, the good thermal stability
of the polymer, and its suitability as a raw material for
[*I From a lecture delivered at the meeting of the Plastics and
Rubber Section of the Gesellschaft Deutscher Chemiker on
April 9th, 1962, in Bad Nauheim (Germany).
430
fibers were recognized by P . Schlack in 1938. In 1962,
an annual production of approximately 250000 tons of
this lactam polymer should be available in the Western
world. A third polyamide, Nylon-11, made from waminoundecanoic acid, is relatively unimportant, its
annual production, including that used for plastics,
being only approximately 1 % of Nylon-6 andNylon-6.6
production combined.
Technically feasible syntheses have recently been found
for other lactams, too, for instance, pyrrolidone,
enantholactam, capryllactam and laurolactam. The
example of Nylon-11 shows that fibers from other polymers of the lactam series may also be of interest. However, considering that there is little difference in the
Angew. Chem. internat. Edit. 1 Vol. I (1962) No. 8
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