Note: Descriptions are shown in the official language in which they were submitted.
lOS;~O~S
This invention relates to a process for the
production of a synthetic fibre from the melt. In particular,
the fibre of this process is an acrylonitrile-containing -~
material.
Fibres made from polymers of acrylonitrile have
long been known in the art. Such polymers usually contain at
least 75% by weight of acrylonitrile, frequently at least 85%,
and most usually 90-99%, of acrylonitrile. Typical monomers ~;~
copolymerized with the acrylonitrile include vinyl pyridine,
styrene, vinyl chloride and vinyl acetate, each monomer when
copolymerized with the acrylonitrile causing a change in one
or more properties of the fibre, especially dye-ability. Such
acrylonitrile polymers are formed into fibres by spinning from
a solution of the polymer in a suitable solvent or from a
suspension of the polymer in a suspending agent~ They cannot
Be spun into fibres from the melt. In order to achieve
reasonable strength or tenacity the fibre usually has to be
after-stretched, which leads to the development of orientation
in the polymer molecules in the fibre, the stretching being -
at an elevated temperature and producing at least a 100-200%
increase in length, followed by cooling of the fibre.
It has now been discovered that a synthetic
fibre may ~e produced by spinning from the melt of a polymer
of acrylonitrile, styrene and isobutylene. The fibre so
produced has a high tenacity without the need for being after-
stretched~
It is an objective of this invention to provide a
process for the production of a synthetic fibre by spinning
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from the melt of a polymer of acrylonitrile, styrene and
~; isobutylene-
The polymers of this invention which are used to
produce the fibres are polymers which contain from 65 to 75
weight % of acrylonitrile, from 13 to 18 weight % of styrene
and from 13 to 18 weight per cent of isobutylene. Preferably
the polymer contains from 66 to 71 weight % of acry~onitrile,
from 14 to 17 weight % of styrene and from 14 to 17 weight %
of isobutylene. Such polymers are advantageously prepared
by a free radical aqueous emulsion polymerization process
and recovered from the aqueous phase by conventional
coagulation techniques. The recovered water-wet polymer is
dried, for example, in a forced-air dryer at a temperature
of at least about 180F. For convenience in subsequent use
~of the polymer, the product from the dryer may ~e further
treated by passage through a vacuum extruder in order to
reduce residual water to a minimum and the extruded product
may then be pelletized. `
Such a polymer may be used to prepare fibres.
8ecause polymers containing high levels of acrylonitrile
tend to absorb moisture on storage, it is desirable to
vacuum dry the pelletized polymer ~mmediately prior to :
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; forming into fibres. The so dried polymer is then supplied
to an extruder for formation into filaments. The extruder
is operated at a high enough temperature to melt the polymer
and to cause good flow of the molten polymer. The product
from the extruder exits through a spinning pack filter system
before passing to a spinneret which contains a number of
small holes of fixed dimension. Such spinnerets are well
~nown in the industry. Temperatures of about 350~ to about
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500F are suitable for the operation of the extruder, spinning
pack filter system and spinneret. Preferably, the temperature
at which the extruder is operated is from 350F to 425F. A
; preferred temperature range for the opera~ion of the spinning
; pack filter system is from 400 to 500F; pressure in the
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' spinning pack filter system will usually be from 1,000 to
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3,500 psi and preerably from 2,000 to 3,000 psi. The fila-
ments flowing from this spinneret are cooled, suitably by one
of cool gas or liqu~d and most suitably by cool air. The rate
of cooling is usually controlled at a uniform rate. The
cooled filament is then wound onto a suitable bobbin. This
windup process may be used to cause draw-down of the filament
or it may be wound up without imparting any stretch to the
filament. The windup may be at a constant speed or at a
constant tension. When the filament is subjected to draw-down
the useful range of draw-down ratios is from about 10:1 to
about 100:1, with a preferred range~being from about 20:1 to
about 50:1. The denier of the filament may range from about
S up to about 100 or more, depending upon the use to which
the final fibre is going to be put. The wound up filament
or fibre may then be handled in a variety of manners depending
on tha use to be made of the fibre. The fibre may be
sub~ected to after-stretching, either hot or cold, to enduce
a greater degree of orientation within the fibre and thereby
impart higher strength, it may be cut into short lengths
or it may be used directly in a weaving process, either
alone or blended with other fibres. The fibre of this
invention has sufficient strength that it may be used
without after-stretching either alone or blended with
another fibre, for instance polypropylene. The polymer of
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of this invention may also be al1oyed with another fibre- ',
forming material such as polypropylene, and the alloy then
formed into fibres. The fibre of this invention has good
elongation properties as shown by good knot tensile strength.
The fibre has also been found to have good temperature
stability as determined by simple ironability tests. The
commercial advantages of spinning a fibre directly from
the melt are well ~nown in the industry.
The following example serves to illustrate the
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lO invention and not to limit the scope thereof.
ExamPle 1
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: Polymer PreParation
A polymer suitable for forming into fibres was
prepared by an emulsion polymerization process. To a
. reactor equi~ped with inlet means, agitating mèans and
~` temperature regulating means was added 200 parts by weight
of water, 2 parts by weight of the di-sodium salt of a
straight chain ethoxylated alcohol half ester of sulfosuccinnic
acid9 2 parts by weight of sodium mono alkyl - phenoxy benzene
disulphonate, 0.2 parts by weight of sodium bisulphite and
15 parts by weight of isobutylene. The temperature of the
contents of the reactor was raised to 122F and the agitation -
`~ means was put into operation. In a separate container was
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prepared a mi~ture cf 70 parts by weight of acrylonitrile,
15 parts by weight of styrene and 0.5 parts by weight of
tertiary dodecyl mercaptan. Also in a separate vessel was
~ prepared a 0.5 weight % solution of potassium persulphate
;i in water. Sufficient potassium persulpha~e solution was
added to the reactor to correspond to 0.5 parts by weight
,~ 30 of potassium persulphate. Essentially simultaneously, the
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addition was ~tarted of the acrylonitrile/styrene/mercaptan
mixture, the rate of addition being uniform and such that the
- addition was complete after a total of five hours. At four
hours from the start of the addition of the acrylonitrile/
styrene/mercaptan mixture, an increment of potassium persul-
phate solution, corresponding to 0.25 parts by weight of
potassium persulphate was added to the reactor. The poly-
- merization was stopped at se.ven hours after the start of the
add~tion of the polymerizable monomers, the conversion of
`~ lD total monomers to polymer being 92%, an aqueous slurry of analkylated aryl phosphite was added to the latex in an amount
~- equivalent to 1 part by wt. per 100 parts by wt. of polymer.
The polymer was recovered by adding the latex to a 1% solu-
tion of calcium chloride at a temperature of 190F and separa-
ting off the coagulated polymer which was then water washed
and dried in a forced air dryer at a temperature of 180 to
190F. The so dried polymer was then further dried by being
put through a vacuum extruder and the extruded product was
pelletized. The polymer was found to contain, by weight,
69% of acrylonitrile, 16% of styrene and 15% of isobutylene.
Fibre PreParation
The pelletized polymer was dried in a vacuum oven
for 1 hour at 80C and then fed to an extruder. The
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experimental fibre spinning system contained an extruder
having a diameter of 1 inch and an L:D ratio of 25:1 with a
three-zone temperature control system on the barrel. The
output from the extruder was fed through a valve adapter to
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a spinning pack containing a 100 mesh screen and into a
spinneret having 104 holes of 0.02 inch diameter. The
filament from the spinneret was cooled by a stream of air
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and passed to a windup bobbin. The extruder was operated at
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a screw s~eed of 18 rpm and at a:temperature of 360F on all
~ three barrel sections and the spinning pack was maintained at
i~ 485F, the pressure in the spinning pack being 2,700 psi.
; The cooling air was maintained at a pressure of 10 psi and
the windup bobbin was run at a speed such that the rate of
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windup waæ 48 ft. per minute. Draw-down of the filament
from the spinneret was 40 to 1.
Fibre ProPerties
The fibre so produced had an average denier of
59 and an average diameter of 126 microns. The average
tensile strength of the straight fibre was 1.9 grams per
denier and the elongation to break was 27%. Knotted fibre
had an average tensile strength of 1.5 grams per denier and
àn elongation of 16%, showing about 80% retentior of the
strength at the knot. -
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~; The fibres produced in this example were found -~
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to show little evidence of sticking to an iron when subjected
to conventional ironing at medium temperature settings. -~
This example shows that a fibre having good
strength properties, without having undergone after-stretching,
i8 readily produced from the polymer of this invention. .
The polymer may be alloyed with, for example,
polypropyIene in the extruder and a fibre produced from the
alloy. Also the pure fibre may be blended with polypropylene
fibres for other applications.
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