CA1233009A

CA1233009A - High speed process for forming fully drawn polyester yarn

Info

Publication number: CA1233009A
Application number: CA000462957A
Authority: CA
Inventors: Cornell Whitley; David F. Whitley; Gregory K. Morris; Robert D. Johnson; James J. Bruening
Original assignee: Celanese Corp
Current assignee: Celanese Corp
Priority date: 1983-09-14
Filing date: 1984-09-12
Publication date: 1988-02-23
Also published as: DE3477407D1; EP0140559A2; JPS6088121A; MX159093A; EP0140559A3; KR850002489A; EP0140559B1

Abstract

IMPROVED HIGH SPEED PROCESS FOR FORMING
FULLY DRAWN POLYESTER YARN
Abstract of the Disclosure An improved process is provided for producing fully drawn multifilamentary polyethylene terephthalate yarn via a high speed melt spinning process wherein the multifilamentary material following solidification is passed through a heated conditioning zone wherein substantial crystallization takes place. Such multifilamentary product is withdrawn from the conditioning zone at a speed in excess of 8000 feet per minute and a conventional drawing step is not required. In accordance with the concept of the present invention it surprisingly has been found that the uniformity of the multifilamentary product is enhanced by the inclusion of a minor substantially uniformly dispersed concentra-tion of particulate silicon dioxide (e.g. fumed silica) in the molten polyethylene terephthalate polymer prior to extrusion and such subsequent processing. In a particularly preferred embodiment the particulate silicon dioxide is substantially uniformly dispersed within the polyethylene terephthalate as a result of its prior admixture with the reactants which were poly-merized to form the polyethylene terephthalate.

Description

33~

Background of the Invention Polyethylene terephthalate multi filamentary yarns have -been produced on the prior art under a variety of conditions.
For instance, in much of the prior art polyester filaments have been melt extruded, quenched, and taken up at relatively low speeds under relatively low stress conditions. Such filaments must be subsequently drawn in a separate processing step at an elevated temperature in order to produce a fully drawn yarn which possesses tensile properties satisfactory for commercial use (e.g. as textile fibers). In some instances particulate materials including titanium dioxide and silicon dioxide have been included in polyethylene terephthalate fibers and films of the Prior art.
It more recently has been disclosed that polyethylene terephthalate fibers possessing fully drawn properties may be prepared in the absence of a conventional drawing step by passing the filaments immediately following quenching through a condo-toning zone provided with a gaseous atmosphere at a temperature above the glass transition temperature and below the melting temperature thereof and withdrawing the same at a relatively high speed. While passing through the conditioning zone substantial crystallization of the previously solidified filamentary material takes place. Such processing conditions offer the significant advantage of eliminating the time and equipment requirements associated with a subsequent conventional drawing step. See particularly, United States Patent Nos. 3,946,100 and 4,195,161 to Herbert L. Davis, Michael L. Gaffe, and Michael M. Basso, and United States Patent No. 4,246,747 to Joseph A. Plunkett and James R. Talbot. See also Swiss Patent No. 530,479, German 3~30~9 Offenlegungschrift 2,117,659, In some instances in the prior art, particulate material such as titanium dioxide has been included in fibers formed by such high speed spinning. As is known in the prior art, such titanium dioxide particles impart a semi-dullor dull appearance to the resulting filaments.
It has been observed that when forming a fully drawn polyethylene terephthalate multi filamentary yarn product via a high speed spinning process which utilizes a conditioning tube that some non-uniformity may be observed upon a careful inspection of the resulting multi filamentary product. Such non-uniformity may manifest itself by random thick filament sections wherein a filament (or filaments) within the multi-filamentary yarn has undergone a lesser level of drawing. Upon ; subsequent dyeing such filaments of increased thickness will tend to absorb a greater quantity of dye and this greater dye absorption may be visually apparent as darker streak areas in fabric which is formed from the same. Also, the overall dye uptake variability as measured by the standard deviation prom the mean may be greater than desired. In the prior ark it has been observed that such non-uniformity is more apt to occur if the multi filamentary material is of a greater total denier (eye.
a total denier above about I and/or if titanium dioxide particles are not present in the polyethylene terephthalate polymer at the time of melt spinning.
It is an object of the present invention to provide an improved high speed process for forming a fully drawn polyethylene terephthalate yarn.

- =
~33C~
r It is an object of the present invention to Provide an improved high speed process for forming a fully drawn polyethy~
tone terephthalate yarn in which the uniformity is enhanced of the filaments which are present therein.
It is an object of the present invention to provide an improved high speed process for forming a fully drawn polyethy-tone terephthalate yarn wherein each filament present within the yarn possesses a more constant thickness along its length and is capable of exhibiting less dye uptake variability than commonly observed in the prior art.
It is an object of the present invention to provide an improved high speed process for forming a fully drawn polyethy-tone terephthalate multi filamentary yarn of enhanced uniformity which is operable when forming yarns of either high or low total denier and with or without the presence ox a titanium dioxide delusterant.
It is another object of the present invention to provide an improved high speed process for forming a lustrous multi filamentary polyethylene terephthalate yarn of enhanced uniformity having a total denier of approximately 40 and which lacks the presence of particulate titanium dioxide dispersed therein.
It is a further object of the present invention to provide an improved high speed process for forming a multi-filamentary polyethylene terephthalate yarn in which the susceptibility of the Polymer to thermal and oxidative degradation is diminished.
These and other objects and advantages, as well as the scope, nature and utilization of the claimed invention, will be - =

I

v. . apparent to ooze skilled in the art from the following detailed description and appended claims.

; Summary of the Invention It has been found that in a process for the formation of a highly spin oriented polyethylene terephthalate yarn comprising (a) extruding molten fiber-forming polyethylene terephthalate through a plurality of orifices to form a molten multi filamentary material, (by passing the molten multifoil-Monterey material in the direction of its length through a solidification zone provided with a gaseous atmosphere at a temperature below the glass transition temperature thereof wherein the multi filamentary material is quenched and is trays-formed to a solid multi filamentary material, (c) passing the resulting multi filamentary material in the direction of its length through a conditioning zone provided with a gaseous atmosphere at a temperature above the glass transition tempera-lure thereof and below the melting temperature thereof wherein substantial crystallization of the previously solidified multi filamentary material takes place, and (d) withdrawing the resulting multi filamentary material from the conditioning zone at a speed in excess of 8000 feet per minute; that improved results are achieved by substantially uniformly dispersing within the fiber-forming polyethylene terephthalate prior to step (a approximately 0.05 to 1.5 percent by weight of particulate silicon dioxide having a weight average particle size of less than 1 micron which serves to enhance the uniformity of the I

filaments which compose the resulting multifilamentarv material, A particularly preferred embodiment of the improved process for the formation of a highly spin oriented polyethylene terephthalate yarn in accordance with the concept of the present invention comprises:
(a) polymerizing monomers capable of forming polyethy-tone terephthalate while in admixture with particulate fumed silica having a nominal particle size of less than 0.1 micron as determined by the BET method to form a fiber-forming polymer having an intrinsic viscosity of approximately 0.5 to 0.8 determined with a solution of 0.1 gram of the polymer dissolved in 100 ml. of ortho-chlorophenol at 25C., b) extruding the resulting polyethylene terephthalate while in molten form and containing approximately 0.1 to 1.0 percent by weight of the particulate fumed silica introduced in step (a) substantially uniformly dispersed therein through a plurality of orifices to form a molten multi filamentary material, (c) passing the molten multi filamentary material in the direction of its length through a solidifica-lion zone provided with a gaseous atmosphere at a temperature below the glass transition temperature thereof wherein the multi filamentary material is quenched and is transformed to a solid multifoil-Monterey material, 3L~33~

(d) passing the resulting multi filamentary material in : the direction of its length through a conditioning zone provided with a gaseous atmosphere at a temperature above the glass transition temperature thereof and below the melting temperature thereof wherein substantial crystallization of the prove-ouzel solidified multi filamentary material takes place, and (e) withdrawing the resulting multi filamentary material from the conditioning zone at a speed in excess of ~,000 feet per minute up to approx-irately 16,000 feet per minute with the presence of the particulate fumed silica serving to enhance the uniformity of the filaments which compose the resulting multi filamentary material/

Description of Preferred Embodiments The Starling Material The starting material selected for use in the process of the present invention is principally fiber-forming polyethy-tone terephthalate which has substantially uniformly dispersed therein a minor concentration of finely divided particulate silicon dwelled which surprisingly has been found to enhance the uniformity of the multi filamentary yarn which is formed under the conditions described herein.
The polymer which it selected for use in the process contains at least 85 mole percent of polyethylene terephthalate, and preferably at least 90 mole percent polyethylene terephtha-late. Accordingly, the term "polyethylene terephthalate" as used 33~39 in the present description ma optionally include minor amounts of other ester-forming ingredients which may be copolymerized with the dominant polyethylene terephthalate units. Illustrative examples of other ester-forming ingredients which may be copolymerized with the polyethylene terephthalate units include glycols such as diethylene glycol, tetramethylene glycol, hexamethylene glycol, etc., and dicarboxylic acids such as hexahydroterephthalic acid, bibenzoic acid, adipic acid, sebacic acid, azelaic acid, etc. In a particularly preferred embodiment of the process the polymer employed is substantially all polyp ethylene terephthalate.
The polyethylene terephthalate which is selected for use in the improved process of the present invention preferably exhibits an intrinsic viscosity, i.e. IVY., of approximately 0.85 to 1~0, and most preferably approximately 0.5 to 0.8 ego.
approximately 0.7) determined with a solution of 0.1 gram of the polymer dissolved in 100 ml. of ortho-chlorophenol at 25C. the IVY. of the melt-spinnable polyethylene terephthalate may be conveniently determined by the equation lit lnnr coo c where no is the "relative viscosity" obtained by dividing the viscosity of a dilute solution of the polymer by the viscosity of the solvent employed measured at the same temperature), and c is the polymer concentration of the solution expressed in grams/100 ml. The polyethylene terephthalate when spun into fibers, commonly exhibits a glass transition temperature of about 75 to 80C., and a melting point of about 250 to 265C~ (e.g. approx-- Jo r ~.23 imat~1v Noah Swahili he apparent to those skilled in the art, the Polymer melting point will be influenced by polymer modifications, the degree of orientation achieved, etc.
The finely divided silicon dioxide is substantially uniformly dispersed in the polyethylene terephthalate prior to extrusion in a concentration of approximately 0.05 to 1.5 (e.g.
approximately 0.1 to 1.0) percent by weight. In a particularly preferred embodiment silicon dioxide is substantially uniformly dispersed in the polyethylene terephthalate in a concentration of approximately 0.1 to 0.4 (e.g. approximately 0.2 to 0.4) percent by weight. Such finely divided silicon dioxide exhibits a weight average particle size of less than 1 micron. Suitable particle size analyzers for use when making such particle size determine-lion are available from Micro metrics Instrument Corporation of Nor cross, Georgia and the Leeds and Northrup Corporation of Saint Petersburg, Florida (Microtrac particle size analyzer).
The silicon dioxide Particles may be obtained from a variety of sources and May be termed fumed silica, colloidal silica, precipitated silica, etc. In a preferred embodiment silicon dioxide particles are selected which have a substantial concentration of available sullenly groups present upon their surfaces. preferred silicon dioxide for use in the improved process of the present invention is fumed silica having a nominal particle size of less than 0.02 micron as determined by the BET
method while assuming that the silicon dioxide particles are spherical in configuration. A representative particularly preferred example of such material is Cab-O-Sil~ fumed silica, Grade M-5, which is commercially available from the Cabot Corporation of Boston, Massachusetts. Such particles possess an 1233~05~

enormous surface urea (eye 200 25 Miriam. are covered with a substantial concentration of sullenly groups, and tend to assume a chain-like structure which may be broken up to some degree by shearing prior to use.
The particulate silicon dioxide may be substantially uniformly dispersed within the polyethylene terephthalate prior to the melt spinning of the same by any suitable blending tech-unique commonly employed to introduce particulate materials into a melt-processable polymer. For instance, known melt compounding techniques using single screw extrudes, co-rotating twin screw extrudes, counter-rotating twin screw extrudes, kneaders, etc.
may be employed provided the required substantially uniform dispersal is achieved. In the event additional particulate material such as titanium dioxide is present, it too may be introduced by the same technique.
In a preferred embodiment the particulate silicon dioxide is intimately admixed with the reactants or monomers capable forming polyethylene terephthalate prior to polymerize-lion and is present with such reactants while they are polymerized in accordance with conventional techniques. For instance, dimethylterephthalate and ethylene glycol may be reacted to form the polyethylene terephthalate~ Alternatively, terePhthalic acid and ethylene glycol may be the monomers employed during the polymerization reaction.
Regardless of the manner in which the silicon dioxide particles become blended with the polyethylene terephthalate it is believed that interaction inherently takes place between the silicon dioxide particles and the polymer which it beneficial during the course of the present process. The nature of this r 33~0~

interaction is not fully understood and is considered to be complex and incapable of simple explanation. For instance, such interaction is believed to be more than simple hydrogen bonding, and beneficially alters the structural and spinning behavior of the polymer when processed as described hereafter.
It should be understood that the polyethylene turf-thalate additionally may contain various chemical and physical modifiers which are routinely provided in such polymer. For instance, small amounts of monomers may be included which serve as cat ionic Diablo polymer modifiers and/or other modifiers such as isophthalic acid, 5-sulfoisophthalic and, etc. may be present. Polymer meeting the specified requirements may additionally or alternatively contain minor amounts of materials used in conventional yarns such as stabilizers (e.g. phosphorus-containing stabilizers), delusterants, optical brightness, polymer modifiers, and the like. In a preferred embodiment, when forming a semi-dull or dull multi filamentary product approx-irately 0.05 to 1.5 percent by weight of particulate titanium dioxide having a weight average particle size of less than 2 microns additionally is substantially uniformly dispersed in the polyethylene terephthalate.

The Melt Extrusion Step _ The extrusion orifices may be selected from among those commonly utilized during the melt extrusion of polyethylene tere~hthalate via a high speed process to form a fully drawn multi filamentary yarn. The orifices may be provided in a variety of cross-sectional configurations so as to form substantially uniform filaments having different cross-sectional shapes. For ~L~33~0~3 r instance? the orifices may be round trilobal etc. The spinnerets selected will commonly have from approximately 6 to 200 holes Such holes when round commonly are approximately 9 to 60 miss in diameter (eye., 9 to 40 miss) or the equivalent thereof if not round. Spinnerets preferably are selected having approximately 20 to I holes.
The molten polyethylene terephthalate having the particulate silicon dioxide substantially uniformly dispersed therein is supplied to the extrusion orifices at a temperature above the melting point of the polyethylene terephthalate. For instance, such polymeric material will commonly be supplied to the extrusion orifices at a temperature of approximately 270 to 310C., and most preferably at a temperature of approximately ~80 to 300C. (e.g. 282C.). As the polyethylene terephthalate is extruded through the extrusion orifices, A molten multifilamen-try material is formed.

The Solidification Step Subsequent to extrusion through the extrusion orifices the resulting molten multi filamentary material is passed in the direction of its length through a solidification or quench zone provided with a gaseous atmosphere at a temperature below the glass transition temperature thereof wherein the molten filament try material is transformed to a solid multi filamentary material. The gaseous atmosphere commonly it provided at a temperature below about 75 to 80C. within the solidification zone the molten material passes from a melt to a semisolid consistency, and from the semi-solid consistency to a solid consistency. While present in the solidification zone, the ~2330~

multi filamentary material undergoes substantial orientation while present as a semisolid The gaseous atmosphere present within the solidification zone preferably circulates so as to bring about more efficient heat transfer. In a preferred embodiment of the process the gaseous atmosphere of the solidification zone is provided at a temperature of approximately 10 to 40C., and most preferably at a temperature of approximately 25 to 30C. The chemical composition of the gaseous atmosphere is not critical to the operation of the process provided the gaseous atmosphere is not unduly reactive with the polyethylene terephthalate. In a particularly preferred embodiment of the process the gaseous atmosphere of the solidification zone is air. Other represent-live gaseous atmospheres which may be selected for utilization in the solidification zone include inert gases such as helium, argon, nitrogen, etc.
The gaseous atmosphere of the solidification zone preferably impinges upon the extruded polyethylene terephthalate so as to produce a substantially uniform quench. The uniformity of the quench may be demonstrated through the ability of the multi filamentary product to exhibit no substantial tendency to undergo self-crimping upon the application of heat. A flat multi filamentary yarn accordingly is produced in a preferred embodiment of the process.
The solidification zone is preferably disposed immedi-lately below the extrusion orifices and the extruded polyethylene terephthalate is present while axially suspended therein for a residence time of approximately 0.0008 to 0.4 second, and most preferably for a residence time of approximately 0.033 to 0.14 second. Commonly the solidification zone possesses a length of ~33~

approximately 1 to 7 feet. standard cross-flow quench may be employed. Alternatively, a center flow quench or any other technique capable of bringing about the desired quenching alter-natively may be utilized.

I' The Conditioning Step Immediately following passage through the solidifica-lion zone the resulting multi filamentary material is passed in the direction of its length through a conditioning zone provided with a gaseous atmosphere at a temperature above the glass transition temperature thereof and below the melting temperature thereof wherein substantial crystallization of the multifilamen-try material takes place. As previously indicated, the glass transition temperature of the filaments will typically be approximately 75 to 80C., and the melting point of the polyethy-tone terephth~late commonly will be approximately 250 to 265C.
(eye., approximately 260C.).
The gaseous atmosphere within the conditioning zone commonly is provided at a temperature within the range of approximately 90 to 220C. (e.g. approximately 135 to 220C.), and the previously solidified multi filamentary material commonly is present therein for a residence time of approximately 0.0001 to 0.8 second (e.g., approximately 0.001 to 0.8 second). The optimum residence time required to produce substantial crystal-ligation may vary with exact composition of the polyethylene terephthalate involved. Longer residence times may commonly be used without commensurate advantage.
The chemical composition of the gaseous atmosphere provided within the conditioning zone is not critical to the ' ~233~10~

operation of the process provided the gaseous atmosphere is not unduly reactive with the multi filamentary material. Static air conveniently may be selected. Other representative gaseous atmospheres which may be employed in the conditioning zone include helium, argon, nitrogen, etc. Band heaters or any other heating means may be provided so as they maintain the condition-in zone at the required temperature. The conditioning zone commonly will have a length of approximately 0.5 to 12 feet, and preferably a length of approximately 3 to 12 feet.
As discussed in United States Patent Jo. 3,946,100, while present in the conditioning zone, the multi filamentary material is heat treated under constant tension. During this heat treatment, small amounts of thermally induced elongation may occur, but this process is to be differentiated from a convent tonal draw process because of the constant tension rather than the constant strain criteria. The level of tension on the multi filamentary material in the conditioning zone is important to the development of the desired properties and is primarily influenced by the rate of withdrawal from the conditioning zone. No stress isolation results along the multi filamentary material intermediate the extrusion orifices and the point of withdrawal from the conditioning zone (e.g., the multi filamentary material is axially suspended in absence of external stress isolating devices intermediate the spinnerets and the point of withdrawal from the conditioning zone). Should one omit the passage of the multifilamentarY material through the conditioning zone, the denier of the product commonly is found to be identical to that obtained while employing a conditioning zone.

~330(3 9 As discussed in united States Patent Nos. 3,94~,100 and 4,195,101, the passage of multi filamentary material through the -conditioning zone modifies the internal morphology of the filaments and renders a subsequent conventional hot drawing step unnecessary. Accordingly, the multi filamentary product exhibits properties generally analogous to those of a fully drawn yarn.

The withdrawal Step The resulting multi filamentary material is withdrawn from the conditioning zone at a relatively high speed in excess of 8,000 feet per minute. Commonly withdrawal speeds in excess of 8,000 feet per minute up to approximately 16,000 feet per minute are selected (e.g., approximately 11,000 to 13,000 feet per minute). A representative technique for accomplishing the high speed withdrawal is to pass the multi filamentary material to pairs of godet rolls situated at the exit end of the conditioning zone prior to packaging. As will be apparent to those skilled in the art, a substantial draw down will occur along the spin line while operating under such conditions The Improved MultifilamentarY Product It surprisingly has been found that the presence of the particulate silicon dioxide substantially uniformly dispersed within the polyethylene terephthalate prior to melt extrusion beneficially enhances the uniformity of the multi filamentary product formed in accordance with the overall process described herein. Such uniformity enhancement is possible regardless of whether particulate material other than silicon dioxide (e.g., a conventional titanium dioxide delusterant is present therein).

ox ~3300~3 - The multi filamentary product of the present invention is particularly suited for use in textile applications and may be readily woven or knitted. Such multi filamentary polyethylene terephthalate product will commonly consist of approximately 6 to 200 continuous filaments each having a substantially constant denier of approximately 1 to 5.
The enhanced uniformity of the multi filamentary product is evidenced by an inspection of the individual filaments present therein under magnification. It is found that a more constant thickness or diameter along the length of individual filaments is observed. accordingly, there is a lesser incidence of undesir-able thick filament areas which were drawn to a lesser degree.
Such thick areas are detrimental since they often tend to absorb dye more readily and can lead to darker streaks in a dyed textile product where they occur. Additionally, the mean deviation in overall dye uptake variability is lessened when practicing the improved process of the resent invention. It further has been observed that the susceptibility of the polymer to thermal and oxidative degradation is diminished because of the presence of the silicon dioxide particles.
In a particularly preferred embodiment of the process of the present invention a lustrous multi filamentary yarn of enhanced uniformity having a total denier of approximately 40 and which lacks the presence of particulate titanium dioxide dispersed therein is formed. In further preferred embodiments a semi-dull multi filamentary yarn of enhanced uniformity having a total denier of approximately 20 to 200 (e.g., 40 to 150) is formed which also includes titanium dioxide particles dispersed therein.

1233~ r The following Examples are presented as specific thus-tractions of the claimed invention. It should be understood, however, that the invention is not limited to the specific details set forth in the Examples.

Example I
To a standard polymerization charge used to form polyp ethylene terephthalate comprising dimethylterephthalate and ethylene glycol is added with mixing a quantity Cowboys fumed silica Grade M-5, commercially available from the Cabot Corporation of Boston, Massachusetts. Jo other solid particles such as titanium dioxide are introduced into the polymerization vessel. The silicon dioxide particles as purchased possess a nominal particle size of 0.014 micron assuming a spherical configuration as determined by the BET method, a surface area of 200 25 m2/gram, and are presheared ho milling prior to introduction into the polymerization vessel. The weight average particle size accordingly is well below 1 micron, The resulting polyethylene terephthalate exhibits an intrinsic viscosity of approximately 0.675 determined with a solution of 0.1 gram of polymer dissolved in 130 ml. of ortho-chlorophenol at 25C., and the silicon dioxide particles are substantially uniformly dispersed therein in a concentration 0.2 percent by weight.
The spinnerets selected for melt extrusion possesses 30 trilobal orifices with each lobe having a maximum width of 0.005 inch, a length of 0.009 inch measured from the center point, and a depth of 0.018 inch. Such trilobal orifices are equivalent in size to a 0.013 inch round extrusion hole. At a rate of 2.06 lbs./hr., the molten polyethylene terephthalate containing the ~33~0~

silicon dioxide particles dispersed therein while at a tempera-lure of 282C. is extruded through the extrusion orifices to form -a molten multi filamentary material. The apparatus arrangement selected generally corresponds to that illustrated in United States Patent No. 3,946,100.
The molten filamentary material passes downward in the direction of its length through a cross-flow quench zone having a length of approximately 3 feet which is provided with flowing air at a temperature of approximately 30C. While present in such quench zone, the molten multi filamentary material is uniformly quenched and is transformed to a solid multi filamentary material.
Situated immediately below the solidification zone is a conditioning zone having a length of approximately 3 feet through which the multi filamentary material next passes in the direction of its length. The conditioning zone is a cylindrical tube into which heated air is introduced at the bottom. The air is present in the conditioning zone at a temperature above the glass tray-session temperature of the polyethylene terephthalate and below the melting temperature thereof. At the midpoint of the conditioning zone the temperature is approximately 155C. Upon being withdrawn from the solidification zone the multi filamentary material is immediately passed through such conditioning zone where it is structurally modified as described in United States Patent Nos. 3,946,100 and 4,195,161 and substantial crystallize-lion takes place.
The resulting multi filamentary material is next withdrawn from the conditioning zone at a rate of approximately 11,500 feet per minute with the aid of godet rolls, has a finish ~33~

Apple thyroid it passed tprou~h a pneumatic intermingling jet to improve handle ability, and is packaged.
The resulting 30 filament multi filamentary yarn will have a total denier of approximately 40, possesses a lustrous appearance, and will exhibit a tenacity of approximately 4.4 grams per denier at room temperature, an elongation of approximately 55 to 60 percent at room temperature, and a boiling water shrinkage of approximately 4.5 percent.
It further will be observed that the multi filamentary product exhibits enhanced uniformity when compared to a similarly prepared multi filamentary yarn wherein no silicon dioxide is added to the Polyethylene terephthalate prior to melt extra-soon. More specifically, the yarn prepared as described above as well as a control yarn, may be knitted in a warp knit configu-ration and dyed with Eastman Blue 210 dye using jet dyeing in accorflance with standard dyeing conditions and the uniformity of the dye uptake observed. Over a 100 foot section of the dyed knitted fabric composed of the multi filamentary yarn formed in accordance with the present invention no streak areas will be observed where non-uniform filaments of increased thickness have adsorbed a greater quantity of the dye. On the contrary, a similarly prepared knitted fabric which lacks silicon dioxide particles dispersed therein will exhibit approximately 50 darkened streak areas where non-uniform filaments of increased thickness have absorbed a greater quantity of the dye.
Additionally, when fabrics are subjected to a load extension test, similar to the Downfall test, in order to measure short term uptake, the fabric containing filaments formed in accordance with the present invention will exhibit reduced signal ~L233~

variability in grams of standard deviation from the Jean. More specifically, the fabric of the present invention will exhibit a value of approximately 3.3, while the control which lacks silicon dioxide will exhibit a greater standard deviation from the mean of approximately 4.
It further it observed that when the multi filamentary yarn of the present invention is subjected to electronic spin resonance or differential scanning calorimetry analysis, that the polyethylene terephthalate of the same will have undergone a lesser degree of thermal degradation during melt processing when compared to the control which lacks silicon dioxide.
Jo Example IT
Example I is substantially repeated with the exceptions indicated pro the standard polymerization charge additionally is added finely divided titanium dioxide having a weight average particle size of approximately 1.06 micron. The titanium dioxide particles are substantially uniformly dispersed in the resulting Polyethylene terephthalate in a concentration of 0.3 percent by weight.
The spinnerets selected for the melt extrusion possesses 30 round orifices each having a diameter of 0.013 inch and a length of 0.018 inch. The molten polymer containing the silicon dioxide particles dispersed therein is supplied to the spinnerets at a rate of 3.6 lbs./hr. The resulting multi filamentary yarn product exhibits a total denier of approximately 70 and a semi-dull appearance.

{ ~L~33~)09 Over a 100 foot section of the dyed knitted fabric composed of the multi filamentary yarn formed in accordance with the present invention no streak areas will be observed. On the contrary a similarly prepared knitted fabric which lacks silicon dioxide particles dispersed therein will exhibit approximately 150 darkened streak areas where non-uniform filaments of increased thicknesses have absorbed a greater quantity of dye.
Additionally, when fabrics are subjected to a load extension test in order to measure short term dye uptake, the fabric containing filaments formed in accordance with the present invention will exhibit a reduced signal variability in grams of standard deviation from the mean of approximately 5.0, while the control which lacks silicon dioxide will exhibit a value of approximately 6.2.

Example III
Example I is substantially repeated with the exceptions indicated.
To the standard polymerization charge additionally is added finely divided titanium dioxide having a weight average particle size of approximately 1.06 micron. The titanium dioxide particles are substantially uniformly dispersed in the resulting polyethylene terephthalate in a concentration of approximately 0.3 percent by weight.
The spinnerets selected for the melt extrusion possesses 30 round orifices each having a diameter of 0.013 inch and a length of 0.018 inch. The molten polyethylene terephthalate containing the silicon dioxide particles dispersed therein is supplied to the spinnerets at a rate of 6.43 lbs./hr. It will be noted that this extrusion rate is greater than that employed in Example II. The resulting multi filamentary product exhibits a -total denier of approximately 125 and a semi-dull appearance.
Over a 100 foot section of the dyed knitted fabric composed of the multi filamentary yarn formed in accordance with the present invention approximately 5 darkened streak areas will be observed. On the contrary, a similarly prepared knitted fabric which lacks silicon dioxide particles dispersed therein will exhibit approximately 1000 darkened streak areas where non-uniform filaments of increased thickness have absorbed a greater quantity of dye.
Additionally, when fabrics are subjected to a load extension test in order to measure short term dye uptake, the fabric containing filaments formed in accordance with present invention will exhibit a reduced signal variability in grams of standard deviation rerun the mean of approximately 12.8, while the control which lacks silicon dioxide will exhibit a value of approximately 15Ø
Although the invention has been described with preferred embodiments, it is to be understood that variations and modifications may be employed without departing from the concept of the invention defined in the following claims.

Claims

WE CLAIM:

1. In a process for the formation of a highly spin oriented polyethylene terephthalate yarn comprising (a) extruding molten fiber-forming polyethylene terephthalate through a plurality of orifices to form a molten multifilamentary material, (b) passing said molten multifilamentary material in the direc-tion of its length through a solidification zone provided with a gaseous atmosphere at a temperature below the glass transition temperature thereof wherein said multifilamentary material is quenched and is transformed to a solid multifilamentary material, (c) passing said resulting multifilamentary material in the direction of its length through a conditioning zone provided with a gaseous atmosphere at a temperature above the glass transition temperature thereof and below the melting temperature thereof wherein substantial crystallization of said previously solidified multifilamentary material takes place, and (d) withdrawing said resulting multifilamentary material from the conditioning zone at a speed in excess of 8000 feet per minute; the improvement of substantially uniformly dispersing within said fiber-forming polyethylene terephthalate prior to step (a) approximately 0.05 to 1.5 percent by weight of particulate silicon dioxide having a weight average particle size of less than 1 micron which serves to enhance the uniformity of the filaments which compose said resulting multifilamentary material.

2. An improved process for the formation of a highly spin oriented polyethylene terephthalate yarn according to Claim 1 wherein said polyethylene terephthalate prior to step (a) has an intrinsic viscosity of approximately 0.35 to 1.0 determined with a solution of 0,1 gram of the polymer dissolved in 100 ml of ortho-chlorophenol at 25°C.

3. An improved process for the formation of a highly spin oriented polyethylene terephthalate yarn according to Claim 1 wherein said gaseous atmosphere of step (b) is provided at a temperature of approximately 10 to 40°C.

4. An improved process for the formation of a highly spin oriented polyethylene terephthalate yarn according to Claim 1 wherein said gaseous atmosphere of step (b) is air.

5. An improved process for the formation of a highly spin oriented polyethylene terephthalate yarn according to Claim 1 wherein said gaseous atmosphere of step (c) is provided at a temperature of approximately 90 to 220°C.

6. An improved process for the formation of a highly spin oriented polyethylene terephthalate yarn according to Claim 1 wherein the gaseous atmosphere of step (c) is air.

7. An improved process for the formation of a highly spin oriented polyethylene terephthalate yarn according to Claim 1 wherein in step (d) said resulting multifilamentary material is withdrawn at a speed in excess of 8,000 feet per minute up to approximately 16,000 feet per minute.

8. An improved process for the formation of a highly spin oriented polyethylene terephthalate yarn according to Claim 1 wherein said multifilamentary material which is withdrawn from step (d) consists of approximately 6 to 200 continuous filaments each having a substantially constant denier within the range of approximately 1 to 5.

9. An improved process for the formation of a highly spin oriented polyethylene terephthalate yarn according to Claim 1 wherein particulate silicon dioxide is substantially uniformly dispersed in said polyethylene terephthalate in a concentration of approximately 0.1 to 1.0 percent by weight.

10. An improved process for the formation of a highly spin oriented polyethylene terephthalate yarn according to Claim 1 wherein said particulate silicon dioxide is substantially uniformly dispersed within said fiber-forming polyethylene terephthalate prior to step (a) as a result of its prior admix-ture with the reactants which were polymerized to form said polyethylene terephthalate.

11. An improved process for the formation of a highly spin oriented polyethylene terephthalate yarn according to Claim 1 wherein said polyethylene terephthalate from which said multi-filamentary material is extruded is free of solid particulate material other than said silicon dioxide and the resulting filamentary product possesses a lustrous appearance.

12. An improved process for the formation of a highly spin oriented polyethylene terephthalate yarn according to Claim 1 wherein said polyethylene terephthalate from which said multi-filamentary material is extruded additionally contains substantially uniformly dispersed therein approximately 0.05 to 1.5 percent by weight of particulate titanium dioxide having a weight average particle size of less than 2 microns and the resulting filamentary product possesses a semi-dull or dull appearance.

13. An improved process for the formation of a highly spin oriented polyethylene terephthalate yarn according to Claim 1 wherein said particulate silicon dioxide possesses a nominal particle size of less than 0.1 micron as determined by the BET
method.

14. An improved process for the formation of a highly spin oriented polyethylene terephthalate yarn according to Claim 1 wherein said particulate silicon dioxide is fumed silica.

15. A highly spin oriented polyethylene terephthalate yarn formed in accordance with the process of Claim 1 which consists of approximately 6 to 200 continuous filaments each having a substantially constant denier within the range of approximately 1 to 5.

16. An improved process for the formation of a highly spin oriented polyethylene terephthalate yarn comprising:
(a) polymerizing monomers capable of forming polyethy-lene terephthalate while in admixture with particulate fumed silica having a nominal particle size of less than 0.1 micron as determined by the BET method to form a fiber-forming Polymer having an intrinsic viscosity of approximately 0.5 to 0.8 determined with a solution of 0.1 gram of the polymer dissolved in 100 ml. of ortho-chlorophenol at 25°C., (b) extruding said resulting polyethylene terephtha-late while in molten form and containing approximately 0.1 to 1.0 percent by weight of the particulate fumed silica introduced in step (a) substantially uniformly dispersed therein through a plurality of orifices to form a molten multi-filamentary material, (c) passing said molten multifilamentary material in the direction of its length through a solidifi-cation zone provided with a gaseous atmosphere at a temperature below the glass transition temperature thereof wherein said multifilamentary material is quenched and is transformed to a solid multifilamentary material, (d) passing said resulting multifilamentary material in the direction of its length through a condi-tioning zone provided with a gaseous atmosphere at a temperature above the glass transition temperature thereof and below the melting tempera-ture thereof wherein substantial crystallization of said previously solidified multifilamentary material takes place, and (e) withdrawing said resulting multifilamentary material from the conditioning zone at a speed in excess of 8,000 feet per minute up to approx-imately 16,000 feet per minute, with the presence of said particulate fumed silica serving to enhance the uniformity of the filaments which compose the resulting multifilamentary material.

17. An improved process for the formation of a highly spin oriented polyethylene terephthalate yarn according to Claim 16 wherein said monomers which are polymerized in step (a) to from polyethylene terephthalate are dimethylterephthalate and ethylene glycol.

18. An improved process for the formation of a highly spin oriented polyethylene terephthalate yarn according to Claim 16 wherein said monomers which are polymerized in step (a) to form polyethylene terephthalate are terephthalate acid and ethylene glycol.

19. An improved process for the formation of a highly spin oriented polyethylene terephthalate yarn according to Claim 16 wherein said polyethylene terephthalate exhibits an intrinsic viscosity of approximately 0.7 determined with a solution of 0.1 gram of polymer dissolved in 100 ml. of ortho-chlorophenol at 25°C.

20. An improved process for the formation of a highly spin oriented polyethylene terephthalate yarn according to Claim 16 wherein said particulate fumed silica is substantially uniformly dispersed in said polyethylene terephthalate in a con-centration of approximately 0.10 to 0.40 percent by weight.

21. An improved process for the formation of a highly spin oriented polyethylene terephthalate yarn according to Claim 16 wherein said particulate fumed silica has a nominal particle size of less than 0.02 micron as determined by the BET method.

22. An improved process for the formation of a highly spin oriented polyethylene terephthalate yarn according to Claim 16 wherein said gaseous atmosphere of step (c) is provided at a temperature of approximately 10 to 40°C.

23. An improved process for the formation of a highly spin oriented polyethylene terephthalate yarn according to Claim 16 wherein said gaseous atmosphere of step (c) is air.

24. An improved process for the formation of a highly spin oriented polyethylene terephthalate yarn according to Claim 16 wherein said gaseous atmosphere of step (d) is provided at a temperature of approximately 90 to 220°C.

25. An improved process for the formation of a highly spin oriented polyethylene terephthalate yarn according to Claim 16 wherein said gaseous atmosphere of step (d) is air.

26. An improved process for the formation of a highly spin oriented polyethylene terephthalate yarn according to Claim 16 wherein in step (e) said resulting multifilamentary material is withdrawn at a speed of approximately 11,000 to 13,000 feet per minute.

27, An improved process for the formation of a highly spin oriented polyethylene terephthalate yarn according to Claim 16 wherein said multifilamentary material which is withdrawn from step (e) consists of approximately 6 to 200 continuous filaments each having a substantially constant denier within the range of approximately 1 to 5.

28. A highly spin oriented polyethylene terephthalate yarn formed in accordance with the process of Claim 16 which consists of approximately 6 to 200 continuous filaments each having a substantially constant denier within the range of approximately 1 to 5.