CA1052065A

CA1052065A - Melt-spinning of polymer of acrylonitrile, styrene and isobutylene

Info

Publication number: CA1052065A
Application number: CA200,529A
Authority: CA
Inventors: Michael H. Richmond
Original assignee: Polysar Ltd
Current assignee: Polysar Ltd
Priority date: 1974-05-22
Filing date: 1974-05-22
Publication date: 1979-04-10
Also published as: FR2272199A1; DE2522733A1; FR2272199B1; GB1464055A; JPS50160521A

Abstract

ABSTRACT OF THE DISCLOSURE

Synthetic fibre is produced by spinning from the melt of an acrylonitrile-containing polymer, such fibres having high tenacity without the need for after-stretching.

Description

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 :~

- 2 -..
:
.~ .

;; i 1~ 0~i5 .~ I
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 :
.. ~
; 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 ., .

~ - 3 -~", "

. ' ~ ~5;~0~i5 r . ,j 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 ..
' spinning pack filter system will usually be from 1,000 to . ~

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

- 4 -,~ .

~o' ~
~, .
~:

~os~o~s 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 ~, .
lO invention and not to limit the scope thereof.
ExamPle 1 ':' : 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 ..
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

- 5 -, ?

105~0~5 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 .
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 . ~
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 ~, ;

- 6 -i ': ' .

;~ "

lOS'~0~;5 ~ ..s:
and passed to a windup bobbin. The extruder was operated at ,:
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 i 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. -;;
~; The fibres produced in this example were found -~
. . ~
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.
.''.' ,.'' ~ .

~ 30 .~
. .. .

~ - 7 -' .
, . ..... , .. . .
;~ .;, . . .

Claims

The embodiments of the invention in which an exclusive property or privilege is claimed, are defined as follows:

1. A process of forming a fibre which comprises spinning from the melt a polymer containing from 65 to 75 weight per cent of acrylonitrile, from 13 to 18 weight per cent of styrene and from 13 to 18 weight per cent of isobutylene.

2. The process of Claim 1 wherein said polymer con-tains by weight 66 to 71 per cent of acrylonitrile, 14 to 17 per cent of styrene and 14 to 17 per cent of isobutylene.

3. The process of Claim 1 wherein said polymer is fed through an extruder to a spinning pack filter system to a spinneret.

4. The process of Claim 3 wherein said extruder, spinning pack filter system and spinneret are operated at temperatures of from about 350°F to about 500°F.

5. The process of Claim 4 wherein said extruder is operated at a temperature of from 350°F to 425°F and the spinning pack filter system at a temperature of 400°F to 500°F at a pressure of 1,000 to 3,500 psi.

6. The process of Claim 5 wherein said spinning pack filter system is operated at a pressure of 2,000 to 3,000 psi.

7. The process of Claim 3 wherein the product from the spinneret is subjected to draw-down within the range of from 10 to 1 to 100 to 1.