Note: Descriptions are shown in the official language in which they were submitted.
1~394~
This invention relates to latent contractable
elastomers~ composite yarns therefrom and methods of forma-
tion and use.
Elastic yarns~ notably spandex yarns, are frequently
used in a variety of woven and knitted articles~ especially
garments, to enhance fit, comfort, and/or to provide compression
support. The use of such yarns is relatively expensive, not
only because of the cost of the fiber, but also because in
order to obtain the maximurn benefits of the elastic properties
of the yarn, the yarn must be woven or knitted in a stretched
condition, requiring specially adapted machinery, which
operates at processing speeds less than those employed with
conventional non-elastic yarns.
In contrast 9 the yarns of the invention can be
processed in a non-stretched mode, as a conventional yarn,
and when formed into a processed, e.g.~ woven, knitted or
tufted article, can be conkracted to provide an elastic
article.
Composite yarns comprising elastic yarns and a
covering of entangled relatively inelastic filaments are
taught in U.S. Patent 3,940,917. These yarns are formed by
conductlng the entangling step when the elastic yarn is in
a stretched condition.
The invention is illustrated by means of the follow-
ing drawings, in which:
Figure 1 is a schematic representation of a process
for entangling a hard fiber yarn about an uncontracted melt
extruded filament of the invention.
Figure 2 illustrates a composite yarn obtained by
the process of Figure 1.
Figure 3 is a schematic representation of a process
for e~truding an elastomer according to the invention.
Figure 4 shows the elongation of original and boiled-
off elastic yarns to the breaking point.
Figure 5 is the same as E'igure 4 except that the
yarns are set for maximum elongation.
Figure 6 shows a stress/strain test for the combina-
tion of 50/2 elastic yarn with a 20/5 stretch nylon companion.
In accordance with a broad aspect of the invention~
there is provided a latent contractable melt extruded segmented,
inherently elastic thermoplastic polymer filament characterized
by containing interspersed relatively hard segments and rela-
tively soft segments, which contracts at least 15% in length
when subjected to an elevated temperature, as compared to the
length of the melt extruded filament prior to contraction to
yield an elastic filament.
In accordance with another broad aspect o-f the
invention, there is provided a method of forming a latent-
contractable elastic filament by melt extruding a polymer as
defined above and then exposing the melt extruded polymer to
an elevated temperature above about 80C to linearly contract
the melt extruded polymer at least 15% to provide an elastic
filament.
This invention relates to melt extruded latent
contractable filaments which are formed by melt extruding
certain segmented physically crosslinked thermoplastic polymers
to form filaments, which filaments, when heat processed at
elevated temperatures, significantly contract to yield an
elastic filament. This invention also relates to the forma-
tion of composite covered yarn comprising said latent contract-
able melt extruded filaments. In addition, this invention
relates to processes for forming articles from said latent
contractable filaments or covered yarns and subsequently
contracting said yarns to forrn an elastic article.
-- 2 --
The latent contrac-table filaments of this invention
are formed by melt extrusion of certain segmented~ cross-
linked thermoplastic polymers, which, when in an elastic
state, display a relatively hard or crystalline segrnent and
a relatively amorphous soft segrnent. W~ile not intending to
be bound by any theory, it is believed that during melt
extrusion, the ordinarily relatively unoriented soft segment
is oriented, at least to some degree, followed by cooling,
which fixes the filament in a relatively oriented state.
Subsequently, as hereinafter described, when the filament is
subjected to heat processing at an elevated temperature, the
orientation of the soft segment created by the melt extrusion
is dissipated, causing contraction of the filament and the
creation of substantially increased elastic properties in the
filament.
The polymers, which can be employed in the yarns and
processes of the invention, include virtually any physically
crosslinked polymer containing interspersed relatively soft and
relatively hard segments which, when melt extruded into a
filament and solidified and then subjected to heat, contracts
at least 15% in length compared to its extruded length to
provide an elastic filament~
It is believed that the polymers which can be employed
are polymers consisting of a hard segment and a soft segment
capable of forming one phase in the melt, which yield a poorly
phase separated morphology when quenched and that, upon latent
contraction by a heat treatment, produce a well phase separated
morphology.
A particularly useful class of elastomers are
described in U.S. Patent No. 4,262,114, issued April 14,
1981. These elastomers comprise thermoplastic segmented
copolyester polyethers, consisting essentially of a multipli-
.~.,.
-- 3 --
city of randomly occurring intrachain segrnents of long-chain
(soft segments) and short-chains (hard segments) ester units 9
said long--chain ester units being represented by the follow-
ing structure:
O O
Il 11
-OLO-C-R-C-
~a)
where L is a divalent radical remaining after removal of
terminal hydroxyl groups from poly (oxyalkylene) glycols
having at least 1 nitrogen containing ring per molecule, a
carbon to nitrogen ratio of from about 3~1 to about 350~1,
and a molecular weight between 200 and 8,000, and R is a
divalent radical remaining after the removal of the carboxyl
groups from a dicarboxylic acid having a molecular weight
of less than 300.
Short-chain ester units are represented by the
following structureo
O O
Il 11
-OEO-C-R-C-
(b)
where E is a divalent radical remaining after removal of
hydroxyl groups from a low molecular weight dlol having 2 to
15 carbon atoms per molecule and a molecular weight between
50 and 250, and R is the divalent radical described for (a)
above.
The introduction of a foreign repeat unit in the
backbone of a crystallizable soft segment, such as a polyether~
has an effect on the soft segment crystallization process.
Such a foreign unit must be stable to processing temperatures
and must not be so rigid as to reduce the mobility (raise the
glass transition temperature) of the soft segment itself. The
foregoing unit should be nonreactive during the synthesis of
-- 4 --
the segmented therrnoplastic elastomer, and should be present
in the concentration of at least 1 unit per polyether molecule.
The polyether unit (or ~OLO~ in formula (a) above)
of the soft segment may be represented by the following
structures, in which the foreign repeat unit X is alkoxylated:
~OCH2CH2~mX~CH2cH~O~n
( c )
or
~ 2 H2)mx(cH2cH2o)ncH2cH2-x-cH2cH2 ~O_
(Cl)
In (c), the unit X is placed near the center of the polyether
chain, and may be one foreign unit or a series of foreign
units covalently linked together. In (d~, the unit X is one
or more foreign repeat units as in (c), but these units are
placed along the length of the linear polyether chain.
In both formulas (c~ and (d), X is a nitrogen con-
taining heterocyclic ring, giving the polyether soft segment
a carbon to nitrogen ratio of from about 3/1 to about 350/1,
and a molecular weight between 200 and 8,000. The sum of m
plus n is within the range of 5 to 180, and x in formula (d)
has a maximum value of 10.
The nature of X is such that it may covalently enter
the polyether chain to influence crystallization. Covalent
links to the polyether in (c) or (d) may be the amide link or
the imide link, both of which are capable of withstanding high
temperature processing. These links, the polyester units them-
selves, and the foreign unit(s) X in (c) or (d) form the soft
segment.
The introduction of the repeat unit X into the
poly(oxyethylene) chain, where X is greatly different from
poly(oxyethylene~, disrupts chain regularity and suppresses the
melting point of the soft segment, preventing crystallization at
~9~
room temperature. This allows the use of higher molecular
weight polyethers, or stated differently, lower mole per-
centage of the soft segment. The lower mole percentage of
soft segment increases the melting point of the copolymer
due to higher mole percentage of the hard segment. Also, a
more regular chain is obtained, which may result in better
separation o~ the hard and so~t phases. Better phase separa
tion results in a higher tenacity, a lower glass transition
temperature for the soft segment, and an improved elastomeric
performance.
The term "foreign repeat unit" as applied to the
soft segments refers to heterocyclic, nitrogen-containing rings
which may covalently link (as amide or imide) along the soft
segment chain as described previously. Representative units
are: l,3-divalent-5~5-dialkylhydantoin (including alkyl groups
connected in a cyclic fashion to the 5,5 positions), 2,5-
divalent-1,3,4-triazole, 2,5-divalent-173~4-oxadiozole,
2,-5-divalent-1,3,4-thiadiazole, 1,3-divalent-1,2,4-
triazolidine-3,5-dione, 4,5-divalent-1,2-isothiazole, 4,5-
divalent-172-oxaæole, 475-divalent-1,3-diazole; 2~5-divalent-
1~3 oxazole, 2,4-divalent-imidazole, divalent (N position)
hypoxanthine, and 2,5-divalent-1,3-thiazole. A pref(~rred
unit is 5,5-dialkyl hydantoin having the following formula:
R" O
R'- ~
H _ ~ ~ N H
o
wherein R' and R" are lower alkyl, e.g.~ methyl, ethyl, propyl,
which can be converted to a polyoxyalkylene glycol represented
by (e) or (f~ by oxyalkylation with ethylene oxide as disclosed
in the above mentioned U.S. Patent No. 4,262,114.
"
-- 6 --
9~
The term "long-chain es~er units" as applied to units
in the copolymer chain refers to the reaction product of a long
chain glycol with a dicarboxylic acid. Such "long-chain ester
units", which is selected Erom repeating units ln the co-
polyesters of thi~s invention, correspond ts formula (a) above.
The long-chain glycol are polymeric glycols having terminal
hydroxy groups and a molecular weight above about 400 and
preferably about 1,000 to 3,000 for (c). The long-chain
glycol used to prepare the copolyesters of this invention are
poly~oxyal]cylene) glycols having foreign repeat units represent-
ed by formulas (e) and (f).
H~OCH2CH2~mX~CH2CH2 O~nH
(e,
X ( CH2CH2 O~nCH2CH2-X-(~H2CH2~H
(f)
The poly(oxyalkylene) glycols have carbon to nitrogen
ratios between about 3/1 and about 350/1, molecular weights
between 200 and 8,000, m plus n is within the range of 5 to
180, and x in formula (f) has a maximum value of 10. In a
preferred embodiment, the poly(oxyalkylene) glycols have carbon
to nitrogen ratios between about 8.5/1 and about 23/1 and
molecular weights between 450 and 8,000. ~epresentative long-
chain glycols are poly(oxyethylene) glycol, poly(oxypropylene)
glycol, poly~oxymethylethylene) glycol, poly(oxytetramethylene)
glycol, and random or block copolymers of ethylene oxide and
1,2-propylene oxide.
The term "short-chain ester units" as applied to units
in the copolymer chain refers to low molecular weight compounds
for polymer chain units having molecular weights less than about
500. They are made by reacting a low molecular weight diol
(below about 250) with a dicarboxylic acid to form ester units
represented by formula (b) above.
-- 7
Included among the low molecular weight diols which
react to form the short-chain ester units are a cyclic,
alicyclic~ and aromatic dihydroxy compounds. Preferred are
diols with 2 to 15 carbon atoms, such as ethylene, propylene,
1,4-butane~ pentamethylene, 2,2-dimethyl trimethylene, hexa-
methylene~ and decamethylene glycol, dihydroxycyclohexane,
cyclohexane dimethanol~ resorcinol, hydroquinone, 1,5-dihydroxy
naphthaline, etc. Especially preferred are aliphatic diols
containing 2 to 8 carbon atoms. Equivalent ester-forming
derivatives of diols are also useful (e.g., ethylene oxide
or ethylene carbonate can be used in place of ethylene glycol).
The term "low molecular weight diols" as used herein should be
construed to include such equivalent ester-forming derivatives,
provided, however, that the molecular weight requirement pertains
to diol only and not to its derivatives.
Dicarboxylic acids which are reacted with the fore-
going long-chain glycols (L in formula a) and low molecular
weight diols (E in formula b) to produce the copolyesters of
this invention are aliphatic, cycloaliphatic, or aromatic
dicarboxylic acids of a low molecular weight, i~e~ having
a molecular weight of less than about 300. The term "dicarboxy-
lic acids" as used herein includes equivalents of carboxylic
acids having 2 functional carboxyl groups which perform sub-
stantially like dicarboxylic acids in reaction with glycols
and diols in forming copolyester polymers These equivalents
include esters and ester-forming derivatives, such as acid
halides and anhydrides. The molecular weight requirement
pertains to the acid, and not to its equivalent ester of
ester-forminy derivative. Thus, an ester of a dicarboxylic
3Q acid having a mol~cular weight greater than 300 or an acid
equivalent of a dicarboxylic acid having a molecular weight
greater than 300 are included, provlded the corresponding
-- 8 --
.3~1t;0
acid has a molecular weight below about 300. The dicarboxylic
acids can contain any substituent groups or combinations which
do not substantially interfere with the copolyester polymer
forma~ion and use of the polymer of this invention.
Aliphatic dicarboxylic acids, as the term is used
herein, refers to the carboxylic acids having 2 carboxyl groups,
each attached to a saturated carbon atom. If the carbon atom to
which the carboxylic acid group is attached is saturated and
is in a ring, the acid is cycloaliphatic. Aliphatic or cyclo-
aliphatic acids having conjugated unsaturation often can be
used, provided they are thermally stable at polymerization
temperatures and do not undergo homopolymerization.
Aromatic dicarboxylic acids, as the term is used
herein, are dicarboxylic acids having 2 carboxyl groups attached
to a carbon atom in an isolated or fused benzene ring. It is
not necessary that both functional carboxyl groups be attached
to the same aromatic ring, and where more than 1 ring is
present, they can be joined by aliphatic or aromatic divalent
radicals or divalent radicals such as -0- or -SO2-~
Representative aliphatic and cycloaliphatic acids
which can be used for this invention are sebasic acidS 1,3-
cyclohexane dicarboxylic acid, l,4-cyclohexane dicarboxylic
acid, adipic acid, glutaric acid, succinic acid, carbonic
acid, oxalic acid, azelaic acid, dimethylmalonic acid, allyl-
malonic acid, 4-cyclohexene-1, 2-dicarboxylic acid, 2-ethyl
suberic acid, 2,2,3,3-tetramethyl succinic acid, cyclopentane
dicarboxylic acid, decahydro-1,5-naphthalene dicarboxylic
acid, 4,4 -bicyclohexyl dicarboxylic acid, decahydro-2,6-
naphthalene dicarboxylic acid, 4,4'-methylene bis(cyclo-
hexane carboxylic acid~, 3,4-furan dicarboxylic acid, and
l,l-cyclobutane dicarboxylic acid. Preferred aliphatic acids
are cyclohexane dicarboxylic acids and adipic acid.
~ g _
9~60
Representative aromatic dicarboxylic acids which
can be used include terephthalic, phthalic and isophthalic
acids, dibenzoic acid, substituted dicarboxylic acids with
two benzene nuclei such as Bis(p~carboxyphenyl)methane ? P-
oxy(p-carboxyphenyl)benzoic acid, ethylene-Bis(p-oxybenzoic
acid), 1,5-naphthalene dicarboxylic acid, 2,6-naphthalene
dicarboxylic acid, 2,7-naphthalene dicarboxylic acid,
phenanthrene dicarboxylic acid, anthracene dicarboxylic acid,
4,4'-sulfonyl dibenzoic acid, and cl-cl2 alkyl and ring sub-
stitution derivatives thereof, such as halo, alkoxy, andaryl derivatives. Hydroxy acids such as (~-hydroxy ethoxy)
benzoic acid can also be used, provided an aromatic dicarboxy-
lic acid is also present.
- Aromatic dicarboxylic acids are a preferred class
for preparing the copolyester polymers. Among the aromatic
acids, those with 8 to 16 carbon atoms are preferred, parti-
cularly the phenylene dicarboxylic acids, i.e., terephthalic,
phthalic and isophthalic acids.
Polymers described herein can be made conveniently
by a conventional ester interchange reaction such as that
described in detail in U.S. Patent 3,763,109. Other special
polymerization techniques, for example, interfacial polymeriza
tion, may prove useful for preparation of specific polymers.
Both batch and continuous methods may be used for any stage of
copolyester polymer preparation. Poly condensation of pre-
polymers can also be accomplished in the solid phase by heating
divided solid prepolymer in a vacuum or in a stream of inert
gas to remove liberated low molecular weight diolO This method
has the advantage of reducing degradation, because it must be
used at temperatures below the softening point of the prepolymer. --
Although the copolyesters possess many desirableproperties, it is advisable to stabilize certain of th~
-- 10 --
~:L99~
compositions to heat or ultraviolet radiation, and this can
be done by incorporating stabilizers into the polyester
compositions. Satisfactory stabilizers comprise phenols
and their derivatives, amines and their derivatives, com-
pounds containing both hydroxyl and amine groups, hydroxy-
azine, oximes, polymeric phenolic esters and salts of
multivalent metals in which the metal is in its lower valent
state. Particularly useful stabilizers of the preferred
segmented co-polyester polyethers are derivatives of 2,2,6,6-
tetramethyl piperidine described in Johnson et al Canadia
application No. 381,354, filed ~uly 8, 1981.
The properties of these copolyesters can be modified
by the incorporation of various conventional inorganic com-
pounds such as titanium dioxide, carbon black 9 silica gel,
alumina, clays, and chopped fiberglass.
A particularly preferred polymer within the above
described class is a polymer consisting essentially of about
30/O to about 60/~ by weight of polybutyleneterephthalate units
and about 40~/0 to about 70/O by weight of hydantoin polyether
units and further characterized as above.
Another group of polyester-polyether polymers are
the so-called Hytrel type copolyesters which contain a
dimethylterephthalate-polytetramethylene ether glycol
(molecular weight about 600 to 3000) derived soft segment and
a dimethylterephthalate-1,4 butanediol derived hard segment.
Preferably, these polymers contain at least about 40/O soft
segment.
Similar polyethylene terephthalate-polytetramethylene
glycol copolymers as well as other polyester-polyether polymers
are described in U.S. Patents 3,880,976, 3,023,192, 3,651,014
and 3,701,755.
Urethane based elastomers, assuming that they can be
" ~ *Trade Mark - 11 -
g~O
melt extruded to provide sufficient phase separation to display
elasticity upon rnelt extrusion, will display the latent con-
traction phenomenon of this invention.
Yet another useful polymer group are segmented
polyester copolymers, having both polyester hard segments
and polyester soft segments. Segmented polymers of this
type can be prepared by forming acid chloride terminated hard
segments, for example, formed by reacting terephthalic acid
chloride with ethylene glycol and then reacting this hard
segment with a soft segment polyester, for example, hydroxyl
terminated polybutyleneadipate. Preferably, these polyester-
polyethers contain at least about 35% soft segment and most
preferably at least about 4~/~ soft segment.
The latent contractable filaments of the invention
are formed by melt extruding the inherently elastomeric polymer
in a conventional manner, preferably to form a filament having
a denier of less than about 300, preferably between about 2 and
about 250 denier, and most preferably between about 10 and about
75 denier.
The resultant melt extruded filaments at least have
a reduced degree of elasticity as compared to the subsequent
contracted filament.
The latent contractable, melt extruded filaments are
contracted by heat processing at an elevated temperature which
is a contraction inducing temperature below the polymer soften-
ing temperature generally in the range of about 40-125C,
preferably between about 80-100C and for a time sufficient
to contract the length of the melt extruded filament at least
25% and preferably at least 40/O as compared to its precontracted
len~th. Generally, the temperature employed is at least about
15C lower than the polymer softening point. The time required
for contraction varies with the type of polymer and the tempera-
- 12 -
ture. Thirty minutes at ~0 lOO~C is generally effective to
obtain significant contraction. As most filaments employed
in fabric are at some point wet processed, the preferred
rnethod of the invention comprises processing the filaments
in an aqueous medium at a contraction-inducing temperature
of at least about 40-60C for a time sufficient to cause
the filament to linearly contract at least about 15% and
preferably at least about 4~/O of its original length.
The contractable inherently elastic filaments of
the invention are especially useful in a process which general-
ly comprises forming a stretchable textile article which com-
prises forming a predetermined over-sized article with yarns
comprising a latent contractable filament which contracts at
least 15% as compared to its original length when exposed to
an elevated contraction-inducing temperature to provide an
elastic filament and exposing the resultant textile article
to an elevated temperature sufficient to contract said latent
contractable filament at least about 15% to form a stretch-
able article of desired size. Usually the contractable
filament is employed in conjunction with other inelastic
yarns and is interspersed unidirectionally or multidirection-
ally within the textile article.
In a preferred embodiment, the melt extruded fila-
ments, prior to wet processing, are processed into a textile
article, either as the sole filament, or most usually inter-
mixed with other fibers, typically in a manner such that the
melt extruded latent contractable filament is unidirectionally
or biaxially directed and spaced apart within the textile to
provide a desired stretch characteristic to the fabric, in a
manner generally known in the textile art. ~owever, contrary
to the conventional practice, the textile articles of the
invention are processed to a relaxed size which is larger
- 13 -
than the desired finished end product. The woven, knitted or
otherwise processed textile product is then subjected to wet
processing at a temperature and for a time sufficient to
cause the melt extruded elastomeric polymer to contract and
achieve its ultimate desired elasticity. ~s a result of this
contraction, the dimensions of the te~tile article are reduced,
resulting in a textile article having desired dimensions and
elastic stretchability.
It is noted that the wet processing step of the
invention need not he carried out as a separate step, but can
be and most desirably is conducted in conjunction with at
least one other aqueous, elevated temperature treatment step
such as washing, dyeing, sizing and the like.
The original precontracted dimensions of the textile
article can be readily determined based upon the latent con-
traction characteristic of the particular melt extruded
elastomeric polymer employed and the quantity of polymer
filaments per unit area, coupled with the heat processing
conditions employed. If necessary, a few trials will readily
determine the necessary originally woven or knitted textile
dimensions required to achieve a heat processed elastically
stretchable textile article having the desired finished
dimensions.
The heat-processed contracted elastic filaments of
the invention have an elastic modulus of at least about ~01
g/D, preferably between ahout .05 g/D and about 0.5 g/D and
most preferably between about 0.2 g/D and about 0.4 g/D,
measured at 100% extension. The preferred filaments of the
invention are those which have a medium elastic modulus, i.e.
between about 0.~ g/D and 0.4 g/D at 100% extension. These
filaments provide processed articles which provide relatively
high compression and relatively low extension.
- 14 -
9~
Many different textile fabrics and types of garments
made therefrom utilizing the contractable elastic filaments of
the invention having useful stretch properties are contemplated,
including some desirably having relatively high compression
forces at low elongation. Some typical uses of stretch fabrics
falling within the invention include undergarments, such as
panty hose, girdles, bras and waist bands; outergarment~, such
as socks, jeans, ski apparel, swimsuits~ tube tops, etc., and
elastic bandages. I'he contractable elastic filaments them-
selves may be especially useful in certain applications, e~g.,elastic string for packaging, and label cords.
The latent-contractable filaments of this invention
can be processed into a textile product as extruded. However,
in order to protect the filament from abrasion, to provide
strength at a maximum extension so that the filament will not
be broken, to provide lower running friction and to enhance
the appearance and feel of a textile, it is desirable to cover
the filaments of the invention with relatively inelastic
filaments (i.e., hard fibers) which can be any of the synthetic
filaments or fibers commonly used for textile purposes. Elastic
yarn covering techniques are known in the art. However, in the
prior processes, the elastic yarn was covered in a stretched
condition in order to prevent the covering hard fibers from
retarding desired extensibility.
In the present invention, the latent-contractable
elastic filaments are covered in their melt extruded pre-
contracted state. If desired, the elastic filaments of the
invention may be single wrapped with a yarn, i.e., one or more
covering yarns being wrapped spirally in a single direction
with the elastic filament, or double covered, an additional
yarn also being wrapped about the composite yarn with opposite
direction of false twist from the first cover yarn. These
- 15 -
wrapping procedures upon the latent-contractable elastic
~ilaments in an essentially uns-tretched state in a manner
such that the wet processed contracted elastic filaments
when stretched will be limited in its extensibility by the
extensibility of the wrapping hard fiber yarns.
In the preferred assembling process of the invention,
the precontraction melt extruded filaments of the invention
are comingled with at least one and preferably at least three
relatively inelastic filaments (hard fibers) to protect the
elastic filament and provide desirable textile properties. The
resultant composite yarn upon heat (preferably wet~ processing
yields a contracted bulky, elastic yarn which is capable of
being extended at least 5~/O and preferably 100~/o of its con-
tracted relaxed length when stretched until the relatively
inelastic filaments first become load-bearing. When stretched
until the hard fibers first become load-bearing, the composite
yarn is characterized by load-bearing, relatively inelastic
filaments entangled with the elastic yarn in intermittent
zones of random braided structure and otherwise extending
substantially parallel to the elastic yarn, there being an
average entanglement spacing of less than 10 centimeters and
the filaments being free from crunodal or other surface loops
when the composite yarn is examined in the stretched condition.
The composite yarn preferably has substantially æero
unidirectional torque. The relatively inelastic filaments
preferably have crimp when relaxed. The crimp is preferably
such that the relatively inelastic filaments form undulations
and twist pigtails when the composite yarn is relaxed. In
accordance with a pre~erred embodiment, the relatively in-
elastic filaments form reversing helical coils when thecomposite yarn is relaxed. The relatively inelastic filaments
may be bicomponent filaments which crimp when relaxed before
- 16 -
or after crlmp developrnent.
The composite yarn after latent con-traction preferably
has a break elongation of 50 to 350 percent or more~ Generally,
the elastic portion of the composite yarn shows no evidence of
crimp, twist or torque produced by the operation of combining
the hard fiber filaments with the elastic yarn.
The composite yarn of this invention can be produced
at feed rates of up to about 2000 meters per minute, or higher,
by continuously feeding the elastic yarn with the relatively
inelastic filaments through jetted high velocity fluid and
impinging the jetted fluid on the yarn axis at an angle of
90 - 45 to entangle the filaments around the elastic yarn
in intermittent zones of random braided structure. Usually,
the precontraction melt extruded filament is fed to the jetted
fluid under predetermined tension sufficient to stretch the
filament, if desired, or merely to maintain it relatively
taut. The relatively inelastic filaments (hard fibers) are
simultaneously fed at a rate which is approximately equal to
the rate at which the melt extruded filament is fed or which
provides a net overfeed of hard fibers to the jetted fluid.
Preferably, the composite yarn is wound on a package under
controlled tension.
Suitable hard fiber filaments or fibers include any
synthetic textile filaments or fibers of relatively inelastic
m~terial such as nylon, e.g.~ nylon 6 and nylon 6,6, a poly-
ester, e.g., polybutylene terephthalate, and polyethylene
terephthalate, polypropylene, cellulose acetate, re~enerated
cellulose, etc. The hard fiber filaments may be fed to the
jetted fluid or a single filament or as a bundle of prefer-
ably at least three filaments and may be of more than onematerial. The bundle preferably has less than 1/2 turn per
inch of twist and the filaments must be capable of being
- 17 -
46~;JP
separated by the jetted fluid~
If desired 7 two or more precontraction melt extruded
filaments may be fed and comingled with the inelastic filaments 9
the plurality of melt extruded filaments being separated at
least temporarily by the jetted fluid to, if desired, insert
portions of the relatively inelastic filaments between the
melt extruded filaments.
The fluid used is preferably compressed air, although
other fluids can be used, it is usually at ambient temperature.
The fluid is preferably impinged on the yarn from more than
one direction, each substantially perpendicular to the yarn
axis.
The rate of feed of the inelastic filaments in
relation to the precontraction melt extruded filament is
determined by the degree of extension desired in composite
yarn before the inelastic filaments become load-bearing. For
any given filament and intended heat processing conditions,
one can determine the amount of contraction to be obtained.
~ince it is desired that the contracted elastic filament of
the invention be extendable at least 50/O and preferably between
about 100% and 350/O~ the amount of inelastic filament fed
should be that amount which becomes load-bearing at the
desired maximum extension of the contracted elastic filament.
Thus, since typically the desired extensibility of
the contracted elastic filament is the contracted relaxed
length multiplied by about 1.75 to about 6 and, since typically
the contracted relaxed length of the heat processed elastic
filament is about 40/O to about 75% of the precontraction melt
extruded filament length, the desired rate of feed of the in~
elastic filament and the precontraction melt extruded filament
can be readily calculated for a ~iven desired composite yarn.
For example, if a heat processed elastic filament is contracted
- 18 -
5~/O based on the starting melt extruded filament and the
desired extensibility is 100~ (contracted length x2~ the
rates of feed of the inelastic filaments and the melt
extruded filament should be equal. On the other hand, if
the desired extensibility of the 50% contracted relaxed
elastic filament is 15~/o ~contracted relaxed length x2.5),
the rate of feed of the inelastic filaments should be 25%
greater than the rate of feed of the melt extruded filament.
These calculations assume no extensibility is inherent in
the inelastic companion filament. ~owever, where the in-
elastic companion filament is crimped or otherwise yieldable,
obviously the relative feed rates must be adjusted to attain
the desired maximum extensibility of the resultant composite
yarn~
Ln order that the relatively inelastic yarn protects
the elastic filament from breaking9 it is preferable that
elastic filament be intermingled with the inelastic yarn in a
manner so that the relatively inelastic yarn becomes load-
bearing at at least less than about ~5% of the break elongation
of the elastic filament.
With reference to Figure 1, a precontraction melt
extruded filament 1 of the invention, from a supply source,
is supplied, at a given rate, by driven feed roll 2 to a fluid
jet intermingling device 7, while relatively inelastic fila-
ments 3, from a supply source, are supplied at a given rate
by rolls 4, 5 and 6, the same as or different from the melt
extruded filament supply rate to the fluid jet intermingling
device 7. The two filament supplies pass through a fluid
intermingling jet with the device 7, ~hich may have filament
guides at the entrance and e~it to center the filaments with-
in the jet which intermingles the hard fiber filaments with
the melt extruded fi]ament. The resultant composite yarn ~
-- 19 --
g~
then passes one or more wraps about roll 9 and then to a
windup device and package 10~
With reference to Figure 2, a useful composite yarn
comprises, for example, two heat contracted elastic filaments
11 and 12, intermingled with five inelastic filaments 13, 14
15, 16 and 17.
The fluid jet intermingling device may be one of
those shown in Bunting et al. U.S. Patent Nos. 3,364,537 and
3,115,691 or McCutchan UOSO Patent No. 3,426,405, for example,
in which one or more fluid streams impinge on the yarn line
at an angle of 90 + 45~. The essential requirement is that
the hard fiber filaments be subjected to a fluid stream having
an appreciable component of force at right angles to the fila-
ments to separate them and force them around the inherently
elastic yarn and around and between other hard fiber filaments
to intermingle the hard fiber filaments by a random braiding
action intermittently along the length of the composite yarn.
If fluid jets are clirected at the yarns at an angle of less
than 45, the fluicl forces parallel to the yarns tend to be
greater than those transverse to the yarns, thereby tensioning
the filaments and tending to form stable loops rather than
braiding them. It is also necessary to avoid a predominantly
unidirectional fluid twisting vortex, since such action tends
to wrap the filaments around the yarn rather than randomly
braiding them. Jets having a unidirectional twisting effect
are suitable for the present process only when a yarn
oscillates rapidly between a region of fluid torque operating
in one direction and a region of opposite torque, as in Bunting
et al. U.S. Patent No~ 2,990,671.
While in the intermingling process, the melt extruded
filament and the inelastic companion filaments can be fed at
greatly varying rates relative to each other, because of the
- 20 -
subsequent contractability of the melt extruded filament it
is not necessary to overfeed the inelastic companion fila-
ments at rates as high as heretofore considered appropriate.
Thus, a preferred process comprises continuously feeding at
least one of the melt extruded filaments a first predetermined
feed rate and relatively inelastic filaments at a second pre-
determined feed rate through jetted high velocity fluid to
entangle the inelastic filament around the melt extruded
filament at spaced intervals, the rate of feed of the in-
elastic filaments being adjusted to the rate of feed of themelt extruded filaments so that the rate of feed of the in-
elastic filaments is less than twice the rate of feed of the
melt extruded filament and is a rate such that after the
resultant composite yarn is exposed to an elevated contract-
ion inducing temperature whereby the melt extruded filament
i5 contracted at least about 15% to provide an elastic fila-
ment, when the resultant composite yarn is stretched, the
inelastic filaments become load-bearing at a predetermined
percent of elastic stretching below the break elongation of
the elastic fi~ament. That is to say, the precontraction
melt spun filament and inelastic filament are fed at rates
adjusted to form a composite yarn which has the desired
elastic extensibility properties after the composite yarns
have been heat treated to contract the melt spun filament.
Because the elastic filament formed by the heat treatment is
shortened, the inelastic filament need not be overfed or at
least need not be overfed to high rates to achieve the desired
elastic extensibility. In any event, upon stretching, it is
desired that the inelastic filaments become load-bearing before
the break elongation of the elastic filament is reached.
The hard fiber multifilaments consist of relatively
inelastic continuous filaments of any commonly available
- 21 -
textile material. Nylon is generally preferred because of
its high strength and low friction. Either uncrimped or
crimped yarn may be employed, but crimped or crirnpable
yarns must be capable of being held loop-free at the tension
required to entangle the filament around the core and wind
the composite yarn on a package. Tension-stable textured
yarn of Breen U.S~ Patent No. 2,783,609, for example, which
has crunodal surface loops when held at tension, is un-
satisfactory for the purpose of the present invention. Iwo
or more different multifilament yarns may be employed, for
example, nylon to give strength at ultimate extension and
cellulose acetate to provide luxurious textile aesthetics
when the fabric i5 relaxed. Two yarns having differential
shrinkage properties may be employed for certain effects.
For example, an untextured polyester yarn having high potential
shrinkage may be fed with a textured nylon yarn and be en-
tangled around a melt extruded core yarn wherein both hard
fiber yarns are at the same tension during entangling and,
in contrast to those of Breen above, remain loop~free when
wound on the package. When such yarn is made into fabric, and
the fabric is heat treated under relaxed conditions, the poly-
ester will shrink while the nylon develops crimp. When the
treated fabric is then stretched, the polyester will become
the load-bearing member to limit the ultirnate extension of the
composite yarn and will permit the textured nylon to retain a
degree of crimp and bulk even at ultimate extension of the
composite.
When the hard fiber component o~ the present com-
posite yarn is crimped or crimpable, the retractive power of
such yarn may be less than that normally required when these
filaments are used alone, since the elastic portion of the
present composite yarn furnishes the major retractive power
- 22 -
3~
o~ the composite. ~he hard fiber filarnents, therefore~
need only have sufficient crimping ahility to form the
crimps 9 twists, or coils desired for imparting bulk, opacity
or tactile aesthetics to the final fabric~ These filaments,
therefore, will be processed at higher speeds or under less
stringent texturing conditions than would normally be
required. This may permit falsetwist te~turing, for example 5
to be performed on hard fiber which is then fed directly
into the entangling step in a single continuous processO
There should be at least one and preferably at
least three hard fiber filamentsO More filaments are
generally desirable to provide more chances for intermingling,
`and more thorough protection for the elastic yarn. Low denier
per filament in the hard fiber yarn is generally conducive to
better intermingling, the smaller filaments being more easily
formed into a random braid. In the case of stretch textured
or bicomponent yarns, low denier per filament favors formation
of small, rine coils when relaxed. Low bending modulus in the
hard fiber ~ilaments is also conducive to improved intermingl-
ing.
The hard fiber feed yarns should have low twist,preferably not more than the 0.2 to 0.5 turns per inch known
as "producer twist", or most preferably zero twist. High
twist interferes with opening of the filament bundle during
the process o~ intermingling and surrounding the elastic
core. Feed yarns having zero or low twist may have interlace
as described in Bunting et alO U.S~ Patent No. 23985,995~ but
they should not have such a large degree of interlace that
the filaments are unable to separate for random braiding in
the present process. For the present purposes, a yarn having
the lowest degree of interlace consistent with processing,
winding, and unwinding is pre~erred 7 no interlace being most
- 23 -
preferable.
The yarns should not have size or finish of such a
cohesive nature that it prevents the bundle from opening
during the intermingling process although certain finishes
may be desirable which allow the bundle to open but aid in
retaining;ntermingling subsequently. Finishes disclosed in
Gray U~S. Patent 3J701,248, for example, may be used to
improve the performance of yarns of this invention.
Yet another useful process for providing a covered
yarn comprises spinning cut or staple fibers about the con-
tractable inherently elastic filament by techniques known in
the art as "core spinning". Core spinning is described in
U. S. Patents 3,380,244, 3,009,311, 3,017,74Q, and 3,038,295.
It is noted that while it has generally been considered
necessary to stretch the core filament (elastic filament)
to provide a useful composite core-spun elastic yarn, in
the present invention, if desired) it is not necessary to
appreciably stretch the melt extruded filament during the
core spinning process. The latent contraction, when heat
activated subsequent to core spinning the relatively inelastic
staple fibers about the melt extruded filament, allows sub-
sequent elastic ~xtension of the resultant core-spun yarn
before the inelastic yarn becomes load-bearing.
There follow a number of Examples which illustrate
the invention and what are now considered its best embodiments~
As throughout the specificationg all parts ana percentages are
by weight, and all tempexatures are degrees Centigrade 9 unless
otherwise specified.
EXAMPLE 1
An ester interchange reactor was charged with 38~9
pounds of dimethylterephthalate, 23 ~2 pounds of 1,4-butanediol,
66.0 pounds of Dantocol DHE 20 , i.e.:
-- 24 --
9~
CH3
( 2 2)n ~ ~ ~ CH2CH20)n H
where m + n = 20, as well as 220 grams of Antioxidant 330, 220
grams of Tinuvin 770TM~ U.V. light stabilizer and 160 grams of
titanium dioxide delusterant~ The ester interchange reaction
was conducted to recover about 12 pounds of methanol. The
resultant reaction product was transferred to a polycondensation
vessel and the reaction continued to recover about 10.6 pounds
of l,4-butanediol and about 102 pounds of the elastomeric
polymer.
With reference to Figure 3, the above 40 wt% PBT-60
wt% HPOE elastomer in the form of polymer chips stored in bunker
(A) were extruded through a 1/2" extruder (B), the zones I, II
and III of the extruder being at temperatures of 215C, 21~C
and 220C, respectively. The extruder melt temperature was
205-207C and the pump yield for a 50 denier elastic yarn was
2.0 g/min. The polymer was extruded through a 2-hole spinneret
(250~ x 400~) into a water bath (C) which was at room tempera-
ture (~22C). The water bath temperature was maintained at
approximately 20-22C by constant inflow and outflow of water.
The distance between the spinneret and the water bath was
approximately 5 inches. A standard polyester finish was applied
by means of a kiss-roll finish applicator (~) The speed of the
two godets (E and F) is 500 meters/min. The elastic yarn was
tangled with the companion yarn (G), 20/5 cationic dyeable
textured nylon, by feeding both the yarns through a tangling
jet (H). The air pressure for tangling used was 60 psi. The
combined yarn was wound on a 6" long tube (0.25" thickness)
using a Leesona winder (J~.
An elastic yarn package containing the combination of
- 25 -
~.~L9~
the above elastic filament and companion filament in a total
denier of 60, which is 40 denier 2 filament (abbreviated as
40/2 elsewhere herein~ elastic yarn and 20/5 stretch nylon
cationic dyeable companion yarn, was positioned on a horizontal
creel of a four-feed hiyh speed (~00 RPM) Sl gauge panty ho.se
machine. The elastic yarn was knit in every fourth course of
the panty portion at about 3 gram tension. The other 3 feeds
~nitted a 50 denier stretch nylon cationic dyeable filament
yarnO The stitch construction was set on a 1 x 1 rib.
The band was made in a 3 x 1 construction of a
conventional 560 denier base spandex with a 50 denier cationic
dyeable nylon filament, so that the entire panty hose top
could be dyed with basic dyes for style purposes. The leg
portion, knitted from regular dyeable nylon stretch filament
yarn, plain or in combination with regular nylon covered
spandex, can be dyed with acid dyes. After knitting, the
toes of the hosiery panels were closed and the panty portions
were slit to construct the total panty hose panty, while a
pre-knitted cotton crotch was sewn in.
The completed panty hose garment was dyed starting
with clean hosiery paddle dyeing machines.
Dyeing formulations were added and initial dyeing
was run for 10-15 minutes. The bath temperature was raised
to 212F at a rate of 3 per minute, at which temperature the
hose were dyed for 30 to 40 minutes. The latent contraction
of the elastic filaments occurred during the dyeing step.
After draining the bath, and gradually cooling the
yarn, two 5-minute rinses were given where in the final rinse
a 2% softener or finish was added for hand and stretch perform-
ance.
Additional samples were made, as above, in which the
ratio of hard segments to soft segments were 50:50 and 60:40,
- 26 -
6~
respectively. The boiling water contraction of the 50:50
PBT/HPOE was 37%, while that of the 60:40 PBT/HPOE was 17%.
EXAMP_E 2
Exposing the elastic composite yarn of Example 1 in
straight but relaxed condition to dry hot air at 240~F
(115.6C) for 30 minutes produced the sarne yarn contraction
as exposing the yarn in straight relaxed condition for 30
minutes in boiling water. As was the case with the boiled-off
elastic yarn, the hot air contraction was also completely
recoverable.
In addition, the elastic modulus of the elastic
filament and the composite yarn o~ Example 1 were studied.
On the ~inear elongation/load tester, Instron Model 1140 with
reversing program possibilities, stress/strain diagrams were
made from melt spun elastic yarn with and without companion
yarn. Both yarn types were measured before and after boil-off.
The yarn in this e~ample was a 50/2 elastic yarn with a 20/5
textured nylon companion yarn. The boiled-off yarn contraction
measured ~1.1%. The denier of the elastic yarn after boil-off
measured 83~
In Figure 4, both the original and boiled-off elastic
yarns were elongated to the breaking point. The original 5 cm
gauge length for the untreated elastic yarn, the solid line, was
reduced to 3 cm, to adjust for contraction of the boiled-off
elastic yarn, the dotted line. The diagram shows a reduction
in the elastic force for the boiled-off yarn, a reduction in
modulus, and a breaking elongation of 56~o~ which is 2 times
the elongation of the untreated elastic yarn of 28~o~ The
crosshead and chart speeds during the measuring were both 50
cm per minute.
In Figure 5, the same yarn types were rneasured under
the same conditions as was the case in Figure 4, with the
~ 27 ~
exception of the setting for maximum elongation. In this
example, the Instron was reversed at reaching 80% of the
breaking elongation in order to measure the relaxation
modulus. The chart and crosshead speeas of the return part
of the cycle were maintained at 50 cm/minute.
In Flgure 6, the combination of 50/2 elastic yarn
with the 20/5 stretch nylon companion yarn was subjected to
the stress/strain test. ~ecause of the higher stress forces
and the lower elongations of the composite yarn, the full-
scale load was doubled and the crosshead speed reduced to10 cm/minute~ One unit (1.5 cm) oE the "force" coordinate
represents a load of 20 grams, while 3 cms on the "elongation"
coordinate equals 20% elongation for the 3-cm sample length
of the contraction adjusted boiled-off yarn, the dotted line.
For the 5-cm gauge length of the original sample, the solid
line, 20% elongation e~uals 5 cm on the horizontal coordinate.
Also, here the chart direction was reversed after reaching 8G%
of the brea~ing elongations for the respective samples in
order to exhibit the contraction modulus. ~e diagram of the
boiled-off yarn exhibits the typical elastic characteristics
of the elastic composite yarn in finished fabrics. Eighty
percent of the breaking elongation measures, in this case, 136%
stretch at a load oE 70 grams. In textile garment applications,
the elastic yarn will usually perform in the 60%~100% elonga-
tion range and between 10-25 grams elastic force.
EX~MPLE 3
A comparison of elastomeric yarns for contraction after
exposure to various fabric processing conditions was made.
Three fabric processes were simulated, atmospheric dyeing alone,
atmospheric dyeing followed by hot air drying and pressure
dyeing~ These test exposures were carried out, comparing a 40/O
polybutylene t~rephthalate hard segment, 60% hydantoin polyether
- 28 -
soft segment segmented copolyester elastomer yarn
(PBT/HPOE) prepared in accordance with U.S. Patent
~o. 4,262,114, and two non-melt extruded
elastomers, Globe Manufacturing 70/1 S5 Lot 525 Glospan
spandex, and duPont 70/8 Type 126 LycraTM spandex. These
three yarns were exposed to the three fabric processing
conditions at no extension (relaxed). Exposures were
conducted on 25-meter skeinsO Length measurements were made
using a 20-gram weight for load. The resultant contraction
data follow:
Conditions YarnContraction ~%)
97C/60 min./Wet/Air Dry PBT-HPOE 53.6
Glospan Lot 5257.8
LycraTM Type 126 6.8
97C/60 min./Wet/Oven PBT-HPO~ 49.6
Dry 120C/5 min. TM
Glospan Lot 52510.5
Lycra Type 1267.3
130C/60 min./Wet PBT-HPOE 62.9
(Pressure) T~
Glospan Lot 525 8.9
'LycraT Type 126 9.7
The primary observation resulting from this data was
a confirmation that, when exposed to a boiling water process
for one hour, the untensioned PBT/HPOE elastomeric yarn con-
tracts to approximately 50/O of its original length. This is
in marked contrast to less than 10% contraction for duPont's
LycraO The contraction of elastomeric yarns upon exposure
to atmospheric boiling water processes appears to be fully
recoverable as stretch - the property most desirable in
elastomeric yarns. In order to verify this fact, modified
elongation tests were used.
In order to demonstrate that the latent contrac~ion
.
;, ..
- 29 -
developed under atmospheric dyein~ conditions would be fully
recoverable as stretch, the yarns exposed to the three fabric
processes above were tested for elongation, but under con-
ditions which corrected the developed contraction of the
yarns. In simple terms, when a developed specimen was tested
in the tensile testing machine, the yau~e length was reduced
by the percentage which the yarn had contracted. The other
machine settings were unaltered. Thus if 1.0" of PBT/IIPOE
elastomeric yarn would stretch to 2.51' before breaking, and
if the developed contraction is fully recoverable, then 0.5"
of the developed PBT-HPOE should stretch to a length of 2.51'
before breaking. The developed yarn could be said to have
twice the elongation of the undeveloped y~rns. Or, if the
elongations are both reported on the basis of the gauge length
used for testing the undeveloped yarn (as is done in the follow-
ing data table3, both undeveloped and developed yarns would be
said to have 2500/o elon~ation, showing that no total extensi-
bility was lost during contraction~
% Elongation - Adjust-
ed for Con_raction _
0/0 ext Relaxed Condi-
Conditions Yarn tion
-
Control PBT-HPOE 250
Glospan Lot 525 870
LycraT Type 126 690
97C/60 min./Wet/~ir PBT~HPOE 250
Dry GlospanT Lot 525 890
Lycra Type 126570
97C/60 min./Wet/Oven PBT'HPOE 290
Dry/120C/5 min.GlospanTM I.ot 525 940
Lycra Type 126630
130C/60 min./Wet/Air PBT-HPOE 130
Dry (Pressure) ~lospan Lot 525 980
Lycra Type 126790
The data in this table demonstrates that the contraction was
fully recoverable as stretch.
~ 30 -
f~
In addition~ elongation, breaking strength tests
were also conducted, the resul-ts of which follow:
Breaking Strength (g)
Conditions Yarn 0/O Ext Relaxed Cond tion
Control PBT-E~POE 47
GlospanT Lot 525 56
Lycra Type 126 85
97C/60 min./Wet/ PBT-HPOE 40
Air GlospanT Lot 525 62
LycraT Type 12689
97C/60 min./Wet/ PBT-HPOE 38
120C/5 min. TM 62
Lycra Type 126 98
130C/60 min~/Wet/ PBT-HPOE 17
Air Dry GlospanT Lot 525 44
(Pressure)
Lycra Type 126 101
EXAMP1E 4
Samples of HytrelT polyether:polyester (polyester
hard segments:poly(ethylene terephthalate), polyether soft
segments; poly(tetrahydrofuran)~ (for preparation, see U.S.
Patent 3 ~763 ~109) were extruded in the manner generally shown
in Example l and separate samples of the extruded filament
exposed to hot air (80C) and boilir.3 water for 30 minutes
and the extent of latent contraction measures:
_atent Contraction (%)
Polymer Denler Hot Alr Boilinq
Hytrel T-4056TM 147 30.2 30.6
50/O hard segment,
50/O soft segment
Hytrel T-5556T 94 13.4 15.2
60% hard segment.
40% soft segment
Hytrel T-6346 77 12.0 14~0
80% hard segment,
20% soft segment
Hytrel T-7246TM 87 9.2 10.2
85% hard segment
15% soft segment
- 31 -
6~
EXAMPLE 5
_ _
In the general manner of Example 1, a segmented
polyether:polyester was prepared consisting of 40/0 poly-
butyleneterephahalate hard segment and 6~/o polyoxyethylene
(mol. wt. 1000) soft segment. The polymer was melt extruded
into a 40 denier filament using a small laboratory ram
extruder. Due to the long residence time inherent in the use
of this extruder, a relatively weak fiber was produced having
a tenacity (gm/denier) of about 0.2, and an elastic modulus
at 100~/o extension of 0.1 gram~denier. The filament, upon
exposure to boiling water for 30 minutes, was an elastic fila-
ment which displayed a 33% contraction from its pre heat
exposure length.
EXAMPLE 6
A 60% poly(butyleneterephthalate) 40/O poly(butylene
adipate) polyester:polyester with soft and hard segments formed
through urethane links, made in accordance with European Appli-
cation ~o. 7900022 published on July 23, 1980 under Publication
No. 0 013 401 , was melt spun in a Killian 1/2-inch ex-
truder at 210C through a 1000~ x 3000,u spinneret, into
water at ambient temperature, and taken up at 300 meter/
minutes, to yield a filament having a denier of 73. The
filament, upon exposure to boiling water for 30 minutes,
displayed a 33% contraction of its original length. ~he
filament prior to heat treatment had an elongation of 213%
and after heat treatment had an elongation of 382%, The
relative viscosity is converted to intrinsic viscosity using
the following modification of the Bellmeyer equation when the
solution concentration is 1%:
(~) = rel ~ 1 + 3(1n ~ rel)
where (~) = intrinsic viscosity and ln - the natural logarithm.
Intrinsic viscosity was measured using a 60~40 phenol/1,1,2,2
- 32 -
1~9~6~
tetrachloroethane mixed solvent containing 5.0 ml of Karl
Fischer reagent per liter of solvent. 0.18 to 0.22 grams of
the dry polymer chips were weighed into a flask and the
phenol/tetrachloroethane solvent containing Karl Fischer
reagent added to make a one percent solution. The samples
were oscillated on a hot plate at gO to 95C until completely
dissolved. The samples were cooled and relative viscosity
determined in a Ubbelohde viscometer in a constant temperature
bath at 25+ 0.1C. Care is taken to minimize exposure to
moisture during the entire procedure.
- 33 -
