CA2039851A1 - Drawn polyester yarn having a high tenacity, a high initial modulus and a low shrinkage - Google Patents

Abstract

ABSTRACT OF THE INVENTION
A DRAWN POLYESTER YARN HAVING A HIGH TENACITY, A HIGH INITIAL MODULUS AND A LOW SHRINKAGE

The instant invention is directed to a drawn polyester yarn.
This yarn is characterized by an initial secant modulus greater than 150 grams per denier/100%. The yarn may be further characterized by either a shrinkage of less than 8% or a tenacity of greater than 7.5 grams per denier. Alternatively, the yarn is characterized by a tenacity of at least 10 grams per denier, an initial modulus of at least 120 grams per denier/100% and a shrinkage of less than 8%.

Description

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A DRAWN POLYESTER YARN HAVING A HIGH TENACITY
A HIGH INITIAL MODULUS AND A LOW SHRINKAGE

Field of the Invention The instant invention is directed to a drawn polyester yarn having a high tenacity, a high initial modulus and a low shrinkage.

Backqround of the_Invention Since fiber-forming, melt-spinnable, synthetic polymers were introduced, fiber manufacturers have Iooked for ways to increase the strength and stability properties of the fibers made from those polymers. The additional strength and stability propertie~ of th~
fibers are needed so that applications beyond textile uses could be opened for their products. Such non-textile uses (also known as "industrial uses") include: tire cord; sewing thread; sail cloth;
cloth, webs or mats used for road bed construction or other geo-textlle applications; industrial belts; composite materials;
architectural fabrics; reinforcement in hoses; laminated fabrics;
ropes; and the likQ.

Originally, rayon was used in some o~ these industrial uses.
Thereafter, nylon supplanted rayon as the material of choice. In the 1970's, conventional polyesters, such as polyethylene terephthalate, were introduced into competition against nylon. In about 1985, higher per~ormance polyesters, l.e. higher strength and greater stability, were introduced.

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A brief review of some of the patent prior art, summarized below, indicate~ that three general areag have been investigated as possible ways of enhancing the strength and stability properties of these synthetic fibers. Those general areas include: processes directed to drawing; processes directed to the polymer; and processes directed to the spinning. Hereinafter, the term "drawing" shall refer to the heating and stretching performed on an as-spun yarn. The term "treatment to the polymer" shall refer to those things done to the polymer prior to spinning. The term "spinning" shall refer to processes for forming fllaments from polymer, but excluding drawing.

The processes directed to drawing are a~ follows:

In U. S. Patent No. 3,090,997, multistage drawing of polyamides, ~or use as tire cords, ls dlsclosed. The fibers (nylon) are melt-spun in a conventional fashion. Thereafter, spun fibers are drawn in a threQ-stage process (drawn, then heated, then drawn again) to obtain a drawn nylon having the following properties: tenacity ranging from 10.4 to ll.l grams per denier ~gpd); elongation ranging from 12.9 to 17.1%J and initial modulus o~ 48 to 71 gpd/100%.

In U. S. Patent No. 3,303,169, there 1~ dlsclo~ed a slngl--stage drawing procese ~or polyamides that yields high modulus, high tenacity, and low ~hrinkage polyamide yarns. The spun polyamide is drawn and heated to at lea~t 115C to obtain a yarn having: tenacity in the range of 5 to 8.7 gpd; elongation ranging from 16.2 to 30.3~:

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initial modulus of 28 to 5sgpd/100%; and shrinkaga ranging from 3.5 to 15%.

In U. S. Patent No. 3,966,867, a two-stage drawing process for polyethylene terephthalate having a relative viscosity of 1.5 to 1.7 i5 disclosed. In the first stage, the fibers are sub;ected to a temperature between 70 and 100C and a draw ratio of 3.8 to 4.2. In the second stage, the fibers are subjected to a temperature between 210 and 250C and a draw ratio, in the aggregate of the first draw ratio and second draw ratio, in the range of 5.6 to 6.1. The dxawn yarn obtained has the following properties: tenacity, 7.5 and 9.5 gpd: elongation, approximately 2 to 5% at a load of 5 gpd; elongation at break, 9 to 15~: and shrinkage, 1 to 4~.

In U. S. Patent No. 4,003,974, polyethylene terephthalate spun yarn, having an HRV of 24 to 28, is heated to 75 to 250c while being drawn, i8 then passed over a heated draw roll, and finally relaxed.
The drawn yarn has the following properties: tenacity, 7.5 to 9 gpd;
shrinkage, about 4~; elongatlon at break, 12 to 20S; and load bearing capaclty o~ 3 to 5 gpd at 7~ elongation.

Those processes directed to enhancing yarn properties by treatment to the polymer are as follows:

In U. S. Patent Nos. 4,690,866 and 4,867,963, the intrinsic viscosity ~I.V.) o~ the polyethylene terephthalate is greater than 2~`39~
0.90. In U. S. Patent No. 4,690,868, the as-spun (undrawn) fiber properties are as follows: elongat~on at break, 52 to 193%:
birefriengence, 0.0626 to 0.136; and degree of crystallinity, 19.3 to 36.8%. The drawn fiber properties are as follows:
tenacity, 5.9 to 8.3 gpd: elongation, 10.1 to 24.4~: and dry shrinkage (at 210C), 0.5 to 10.3~. In U. S. Patent No. 4,867,936, the drawn fiber properties are follows: tenacity, about 8.5 gpd:
elongation at break, about 9.9%: and shrinkage tat 177C), about 5.7~.

Those processes directed to spinnlng are as follows:

In U. S Patent No. 3,053,611, polyethylene terephthalate after leavlng the sp~nneret is heated to 220C in a spinnlng shaft two meters long. Thereafter, cold water is sprayed onto the fibers in a second shaft. The fibers are taken up at a speed of 1,600 meters per minute ~mpm) and are subsequently drawn to obtain a tenaclty of 3.5 gpd.

In U. S. Patent No. 3,291,880, a polyamlde is ~pun ~rom a splnneret and then cooled to about 15C, then the fiber ls sprayed wlth llve steam. The as-spun fiber has a low orlentatlon and a low birefriengence.

In U. S. Patent No. 3,361,~59, a synthetlc organlc polymer is ~pun into a fiber. AB the flbers exit the spinneret, they are 2039~
subjected to ~controlled retarded cooling". This cooling is c~ducted over the firs~ seven inches from the spinneret. At the top (i.e. adjacent the spinneret), the temperature is ~00C and at the bottom (i.e. approximately 7 inches from the spinneret), the minimum te~perature is 132C. The as-spun yarn has a low birefriengence (ll to 35 x 10 3) and drawn yarn properties are as follows: tenacity, 6.9 to 9.4 gpd; initial modulus, 107 to 140 gpd/100%; and elongation at break, 7.7 to 9.5%.

In u. s. Patent Nos. 3,936,253 and 3,969,462, there is disclosed the use o~ a heated shroud (ranging in length from one-half foot to two feet) with temperatures ranging from about 115 to 460C. In the former, the temperature is greater at the top of the shroud than at the bottom. The drawn yarn propertles of the former are as follows:
tenacity, 9.25 gpd; elongation, about 13.5%; and shrinkage, about 9.5%. In the latter, the temperature is constant within the shroud and the drawn yarn properties are as follows: tenacity, 8 to 11 gpd; and elongation at break, 12.5 to 13.2%.

In U. S. Patent No. 3,946,100, flbers are spun from a spinneret and solidified at a temperature below 80C. The solidified fibers are then reheated to a temperature between the polymer's glass transition temperature (Tg) and its melting temperature. This heated fiber is withdrawn from the heating zone at a rate of between 1,000 to 6,000 meters per minute. Spun yarn propertles are as follows: tenacity, 3.7 to 4.0 gpds initial modulus, 70 to 76 gpd/100%s and birefriengence, 0.1188 to 0.1240.

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2~3~51 ~ n U.S. Patent No. 4,491,657, polyester multifilament yarn is melt-spun at high speed a~d solidlfled. Solidification occurs in a zone comprising, in series, a heating zone and a cooling zone. The heating zone is a barrel shaped heater (temperature ranging from the polymer's melting temperature to 400C) ranging in length from 0.2 to 1.0 meters. The cooling zone is cooled by air at 10 to 40C. Drawn yarn made by this process has the following properties: initial modulus, 90 - 130 gpd: and shrinkage (at 150C) less than 8.7%.

In U. S. Patent No. 4,702,871, fiber is spun into a chamber having a subatmospheric pressure. Spun yarn properties are as follows:
strength, 3.7 to 4.4 gpd: birefriengence, 104.4 to 125.8 (x 10 3): and dry heat contraction, 4.2 to 5.9% at 160C Sor 15 minutes.

In U. S. Patent No. 4,869,958, the fiber is spun in the absence of heat and then taken up. At this point, the fiber has a low degree of crystallinity, but it is highly oriented. Thereafter, the fiber is heat treated. The drawn fiber propertles are as follows: tenacity, 4.9 to 5.2 gpd: initial modulus, 92.5 to 96.6 gpd/100%; and elongatlon, 28.5 to 32.5%.

The foregoing review of patents indicates that while some of the fibers produced by these various processes have high strength or low shrlnkage properties, none of the foregoing patents teach o~ a yarn or a proces~ ~or producing such a drawn yarn having the combination of high tenacity, high lnltlal modulus, and low shrinkage.

The patents which come closest to teaching such a drawn yarn are U. S. Patent Nos. 4,101,525 and 4,195,052, related patents that are assigned to the assignee of the instant invention. In these patents, the polyester filaments (the polymer having an intrinsic viscosity of 0.5 to 2.0 deciliters per gram) are melt spun from a spinneret. Molten filaments are passed through a solidification zone where they are uniformly quenched and transformed into solid fibers. The solid fibers are drawn from the solidification zone under a su~stantial stress (0.015 to 0.15 gpd). These as-spun solid fibers exhibit a relatively hlgh birefrlengence (about 9 to 70 x 10 3). The a~-spun flbers are khen drawn and subsequently heat treated. The drawn filament ~roperties are as follows: tenacity, 7.5 to 10 gpd; initial modulus, 110 to 150 gpd/100%: and shrinkage, less than 8.5% in air at 175C.

Summary of the Invention The instant invention i9 directed to a drawn polyester yarn.
This yarn is characterized by an initial secant modulus greater than 150 grams per denier/100%. The yarn may be ~urther characterized by either a shrinkage o~ le~s than 8% or a tenacity o~ greater than 7.5 grams per denier. Alternatlvely, the yarn is characterized by a tenacity of at least 10 gram~ pQr denler, an lnltlal modulus of at least 120 grams per denier/100% and a shrinkage of les6 than 8%.

DescriPtion of the Drawinq For the purpose of illustrating the invention, there is shown in the drawing a 6chematic of the process which is presently preferred:

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it being understood, however, that this invention is not limited to the preci~e arrangement and instrumentalities shown.

Figure 1 is a schematic elevational view of the spinning process.

Figure 2 is a schematic elevational view of the drawing process.

Detailed Descri~tion of the Invention High tenacity, high initial modulus, and low shrinkage drawn yarns and the process by which such yarns are spun are discussed hereinafter. The term "yarn" or "~llament" or "~lber" shall refer to any fiber made from a melt spinnable synthetic organic polymer. Such polymers may includa, but are not limited to, polyesters and polyamides. The invention, however, has particular relevance to polyesters such ac, for example, polyethylene terephthalate (PET), blends of PET and polybutylene terephthalate (P~T), and PET
cross-linked with multifunctional monomers (e.g. pentaerithritol). Any of the foregoing polymers may include conventional additives. The yarn I.V. (~or PET based polymer) may be between 0.60 and 0.87. The instant lnvention, however, i5 not dependent upon the intrinsic visaosity (I.V.) o~ the polymer.

Re~errlng to Figure 1, a spinning apparatus 10 is illustrated. A
conventional extruder 12 for melting polymer chip is in fluid communication with a conventional spinnlng beam 14. Within spinning beam 14, there i8 a conventional spinning pack 16. Pack 16 may be of ... .

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an annular design and it filters the polymer by passing the polymer through a bed of finely divided particle~, as is well known in the art. Included as part of the pacX 16 is a conventional spinneret (not shown). Flow rates of polymers through the pack may range from about 10 to 55 pounds per hour. The upper limit of 55 pounds is defined only by the physical dimensions of t~e pack 16 and greater flow rates may be obtained by the use of larger pac~s. The spun denier per filament (dpf) ranges from 3 to 20: it being found that the optimum properties and mechanical qualities for the yarn appear between 5 and 13 dpf.

Optionally, the fiber, as it leaves the spinneret, may be guenched with a hot inert gas (e.g. air). See U. S. Patent No.
4,378,325 which is incorporated herein by reference. Typically, the gas i8 about 230C and i9 provided at about six standard cubic feet per minute (scfm). If the air is too hot, i.e. over 260c, the spun yarn properties are significantly deteriorated.

Immediately below and snugly (i.e. airtlght) mounted to spinning beam 14 ls an elongated column 18. The column comprlses an insulated tube havlng a length o~ about 5 meters or greater. Column length will be discussed in greater detail below. The tube's internal dlameter ls sufflciently large (e.g. twelve inches) so that all fllaments from the spinneret may pa6~ the length of the tube without obstruction. The column is equipped with a plurallty of conventlonal band heaters so that the temperature within the tube can be controlled along its 2 ~
length. Column temperatures will be discussed ln greater detail below. The column is, pre~erably, subdivided into a ~umber o~
discrete temperature zones for the purpose of better temperature control. A total of 4 to 7 zones have been used. optionally, the column 18 may include an air sparger 17 that is used to control temperature in the column. sparger 17 is designed to evenly dlstribute an inert gas around the circumference of the column.

Inside the bottom-most end of the column 18 is a perforated, truncated cone 19, i.e. a means for reducing air turbulence. The cone 19, which is preferably three feet in length and havlng a dlameter co-extensive with the tube diameter at its uppermost end and a diameter of about one half that at the bottom end, is used to exhaust air, via a valved exhaust port 21, from the bottom-most end of the tube so that movement in the thread line, due to air turbulence, is sub~tantlally reduced or ellminated co~pletsly.

3elow the bottom-most end of the column, the thread line is converged. This convergence may be accomplished by a finish applicator 20. This i8 the first contact che yarn encounters after leaving the spinneret.

The length of the column, non-convergence of the individual filaments, and the air temperature profile within the column are of particular importance to the instant invention. With regard to the temperature profile, it is chosen so that the fibers are maintained at a temperature above their Tg over a significant length o~ the column .

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(e.g. at least 3 meters). This temperature could be maintained over the entire length of the column, but the wound ~ilaments would be unstable. Therefore, for practical reasons, the temperature within the column is reduced to below the Tg, so that the filaments will undergo no further changes in crystal structure before being wound up.
Preferably, the temperature profile is chosen to reflect the temperature profile that would be established within the tube if no external heat was applied. However, the "no external heat" situation is impractical because of numerous variables that influence the column temperature. So, the temperature profile is controlled, preferably in a linear fashion, to eliminate temperature as a variable in the proces~.

The air temperature within the column i~ controlled by the use of the band heaters. Preferably, the column is divided into a plurality o~ sections and the air temperature in each section ls controlled to a predetermined value. Thus, the temperature within the column can be varied over the length of the column. The temperature within the column may range from as high as the polymer spinning temperature to at or below the gla~s transitlon (Tg) temperature c~ the polymer (Tg ~or polyester ls about 80C). The polymer spinning temperature occurs around the spinneret, i . e. as the molten polymer exits the spinneret.
However, air temperatures within the column are preferably controlled from about 155C to about 50C. At wind-up speeds less than 14,000 feet per minute, the first section ad~acent the spinneret is preferably controlled to a temperature o~ about 155C and the section furthest from the spinneret is controlled to about 50C.

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However, a linear temperature profile i5 not the only temperature pattern that wlll yield the beneficial results disclosed herein. At taXe-up (or wind-up) speeds greater than 14 , ooo fpm (4, 300 mpm), the temperature profile (when the column is divlded into four discrete zones) may be as follows: (starting from the spinneret downJ the first zone - about 105C to about 110C; the second zone - about 110C to about 115C; the third zone - about 125 to about 130C; and the fourth zone - 115C to about 120C.

With regard to column length, a minimum column length of five meters (with column temperature over the polymer's Tg for at least 3 meters) with filament convergence thereafter appears to be necessary for the instant lnvention. Column lengths between five and nlne meters are suitable for the inventlon. The upper limit of nine meters is a practical limit and may be increased, room permitting. To optimize the tenacity propQrties, a column length of about seven meters is preferred.

The fibers are converged after exiting ths column 18. This convergence may be accomplished by use of a finish applicator.

Following the first application of the finish (i.e. at finish applicator 20), the yarn is taken around a pair of godet rolls 22.
Thereafter, a second application of finish may be made (i.e. at finish applicator 23). The first finleh application may be made to reduce statlc electricity built up on the fibers. But this finieh is 2 ~
sometimes thrown off as the fibers pass over the godet rolls~ Thus, the finish may be reapplied after the godet rolls.

The fibers are then passed onto a conventional tension control winder 24. The wind-up speed is typically greater than 3,000 mpm ~9,800 fpm~ with a maximum speed of 5,800 mpm (19,000 fpm). An optimum range exists of about 10,500 to 13,500 fpm (about 3,200-4,100 mp~). The most preferred range exists between about 3200 and 3800 mpm (10,500 and 12,500 fpmJ. At speeds below 9,800 fpm (3,000 mpm), the yarn uniformity properties deteriorate.

The as spun polyester yarn produced by the foregoing process may be generally characterized as having relatively small crystals and a relatively high orientation. It is believed that these qualities of the as spun yarn enable the attainment of the unique drawn yarn propertie~ discussed below.

~ o quantify the general characterization of the as spun polyester yarn, the small crystals are de~ined in terms of crystal size (m-a~ured in ~) and orientation is de~ined in one o~ the following terms: optlcal birefringence: amorphous bire~ringence; or crystal blre~ringence. Additlonally, the spun polyester yarn is characterized ln term o~ cry~tal size and long period spacing ~the distance between crystals). In broad terms, the as spun polyester yarn may be characterized as having a crystal size less than 55~ and either an optlcal blrefringence greater than 0.090 or an amorphous bire~ringence ;

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greater than 0.060 or a long period spacing of leg8 than 300~. More preferred, the as spun polyester yarn may be characterized as having a crystal size ranging from about 20 to about 55~ and either an optical birefringence ranging from about 0.090 to about 0.140 or an amorphous birefringence ranging from about 0.060 to about O.loO or a long period spacing ranging from about 100 to about 250~. Most preferred, the as spun polyester yarn may be characterized as having a crystal size ranging from about 4~ to about 54~ and either an optical birefringence ranging from about 0.100 to about 0.130 or an amorphous birefringence ranging from about 0.060 to about 0.085 or a long period spacing ranging from about 140 to about 200~.

As will be apparent to those of ordinary skill in the art, the crystal size of the spun yarn is about 1~3 that of conventional yarns ln the optlmum wind-up speed range. The crystal size increases with speed, but it still remains low. The spun amorphous orientation i9 very high, about twice normal. This spun yarn has such a high orlentation and low shrinXage, that lt could be used without any drawing.

In addltlon, the spun polyester yarn has the following propertle6: a crvstal content (i.e. cry~tallinity level as determined by density) o~ 10 to 43~: a ~pun tenacity of about l.i to 5.0 gpd; a spun modulus ln the range of 10 to 140 gpd/100%: a hot air shrinkage of about 5 to 45%; and an elongatlon of 50-160%.

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Thereaftar, the spun yarn is drawn. Refer to Figure 2. Either a one or two stage drawing operation may be used. However, it has been determined that a second stage offers little-to-~o additional benefit.
It is possible that the spinning operation may be coupled directly to a drawing operation (i.e., spin/draw proces~).

The as-spun yarn may be fed from a creel 30 onto a feed roll 34 that may be heated from ambient temperatures up to about 150C.
Thereafter, the fiber is fed onto a draw roll 38 which may be heated from ambient temperatures to approximately 255C. If heated rolls are not available, a hot plate 36, which may be heated from 180 - 245, may be used. The hot plate 36 (having a six inch curved contact surface) is placed in the draw zone, i.e., between feed roll 34 and draw roll 38. The draw speed ranges from 75 to 300 meters per minute.
The typical draw ratlo is about 1.65 (for spun yarn made at about 3,800 meters per minute). The optimum feed roll temperature, givlng the highest tensile strsngth, was found to be about 90C. The optimum draw roll temperature is about 245C. If the hot plate is used, the optimum temperature is between about 240 - 245C. The draw roll temperature gives some control over hot air shrinkage. In general, low ~hrlnXage~ are deslrable as they give rise to the best treatéd cord stablllty ratlngs. However, at least one end use, sail cloth, requlres higher drawn yarn shrlnkages and these can be controlled wlth lower draw roll temperatures.

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Based on the foregoing, the drawn fiber properties may be controlled as follows: Tenacity may range from 4.0 to 10.8 grams per denier. T~e elongatio~ may range from 7% to approximately 80%. The initial secant modulus may range from 60 to 170 gpd/100%. The hot air shrinkage (at 177C) is 6% to 15%. The denier of the fiber bundle may range from 125 to llOo (the latter number may be obtained by plying tows together) and the denier per filament ranges from 1.5 to 6 dpf. Such a yarn could be used as the fibrous reinforcement of a rubber tire.

Polyester (i.e., PET) drawn yarns, made according to the process described above, can obtain an initial secant modulus greater than 150 grams per denier/100. Moreover, those yarns may also have a shrinkage of less than 8%, or those yarns may have a tenacity of greater than 7.5 grams per denier.

Another preferred embodiment of the drawn polyester yarn may be characterized as follows: a tenacity of at least 8.5 grams per denier;
an lnitial modulus of at least 150 grams per denierJ100%, and a shrlnkage of less than 6%. Another preferred embodiment of the drawn polyester yarn may be characterized as follows: a tenacity of at least 10 grams per denier; an initial modulus of at least 120 grams per denier/100%s and a shrinXage of less than 6%. Yet another preferred embodiment of the drawn polyester yarn may be characterlzed as follows: a tenacity ranging from about 9 to about 9.5 grams per denler; an initial modulus ranging from about 150 to about 158 grams per denier/100%s and a shrinkage les~ than 7.5%.

- 2~3~8~1 Any drawn yarn, made according to the above described process, may be utilized in the following end uses: tire cord, sewlng thread;
sail cloth; cloth, webs or mats used in road bed construction or other geo-textile applications; industrial belts; composite materials:
architectural fabrics; reinforcement ln hoses; laminated fabrics;
ropes: etc.

The following critical tests, which are used in the foregoing dlscusslon of the inventlon and the subsequent examples, were performed as follows:

Tenacity refers to the "oreaking tenacity" as defined in ASTM
D-2256-80.

Initial modulus (or "lnitial secant modulus") i5 defined per ASTM
D-2256-80, Section 10.3, except that the line representing the initial straight line portions of the stress-strain curve is specified as a secant line passing through the 0.5% and 1.0% elongation points on the stress-straln cur~e.

All other tensile propertles are as defined in ASTM D-2256-80.

. ShrinXage (HAS) is defined as the linear shrinkage in a hot air environment maintained at 177+1C per ASTM D-885-85.

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Density, crystal size, long period spacing, crystal blrefringence, and amorphous birefringence are the same as set forth in U.S. Patent No. 4,134,882 which is incorporated herein by reference. Specifically, each of the foregoing may be found in U.S.
Patent No. 4,134,882 at or about: density - column 8, line 60; crystal size - column 9, line 6; long period spacing - column 7, line 62;
crystal birefringence - column 11, line 12; and amorphous birefringence - colYmn 11, line 27.

Blrefringence (optical birefringence or ~n) is as set forth in U.S. Patent No. 4,101,525 at column 5, lines 4-46. U.S. Patent No.

4,101,525 is incorporated herein by reference. "Bi CV" is the coefficient of variation of optical birefringence between filaments calculated from 10 measured filaments.

Other tests referred to herein are performed by conventional methods.

Reference should now be made to the Examples whlch will more rully lllu~trat- the instant lnventlon.

Example I
In the followlng set o~ experimental runs, a conventional polyester polymer (PET, IV-0.63) was spun. The spinning speeds were increased from 12,500 fpm to 19,000 fpm. The column length was 6.4 meters and divided into four temperature control zones. The 203~

temperature was controlled by measuring the air temperature close to the wall at the center of each zone. The polymer was extruded at a rate of 22.9 pounds per hour through a spinning beam at 285C and a 40 hole spinneret (hole size 0.009 inches by 0.013 inches). The fibers were not quenched. The spun fibers were not drawn, but they were heat set. The results are set forth in TA~LE I.

TABLE I
No. 1 No. 2 No. 3 No. 4 No. 5 No. 6 No. 7 No. 8B

Spin Speed, fpm 12,500 13,500 14,500 15,500 16,500 17,500 18,500 19,000 Col - ~op, 'C110 108 105 104 105 105 106 105 T~mp. 2nd, ClOS 104 104 107 109 110 106 110 3rd, C131 130 129 132 132 132 130 133 ~otto~, C 109 107 105 111 111 111 109 119 Denler340 310 290 270 255 240 225 220 dpf 8.5 7.8 7.2 6.8 6.4 6.0 5.6 5.5 ~True Stress"
st Bresk gpd6.51 6.41 6.55 6.65 7.23 6.98 6.86 7.14 Spun: Denier340 316 289 270 254 240 228 222 s Tensclty, gpd 3.93 3.89 4.10 4.18 4.55 4.52 4.57 4.71 Elong, ~ 65.7 64.8 59.8 59.2 59.0 54.5 50.0 51.6 Tl~ 31.8 31.3 31.7 32.3 34.9 33.4 32.3 33.8 I.M.,gpd/100~ 54 0 56.4 52.1 59.2 65.4 60.1 66.6 76.2 HAS, ~-350'F 6.0 6.5 7.0 7.5 7.2 7.5 7.0 7.2 Uster, ~.96 1.29 1.14 1.28 1.33 1.59 1.34 1.52 Finlsh, ~ .098 .358 .119 .168 .263 .037 .160 .267 IV .623 .630 ,629 .631 .630 .629 .626 .627 ~ Cryst.3 34.2 35.3 37.2 39.0 40.3 42.2 43.2 43.3 Qn x 10 108 106 115 112 118 124 127 130 BlCV ~ 2 4.3 6.5 5.8 4.7 6.7 6.9 8.4 Donslty,gmJ/cc 1.3728 1.3742 1.3766 1.3788 1.3804 1.3827 1.3840 1.3841 Ylelt Polnt Tenaclty, gpd 1.18 1.26 1.38 1.48 1.57 1.67 1.75 1.80 Heae-Set: Denler 338 308 287 271 252 240 226 231 Tenaclty, gpd 4.06 4.19 4.26 4.34 4.33 4.46 4.65 4.64 Elong, ~ 62.3 58.6 53.2 51.0 49.5 46.6 44.4 45.1 Tl ~ 32.0 32.1 31.1 31.0 30.5 30.5 31.0 31.2 I.M.,gpd/100~ 60.2 62.2 66.3 70.0 68.8 64.0 73.2 72.6 HAS, ~-350-F 2.0 2.2 2.8 2.8 3.0 3.2 3.0 2.5 Cryst.3 55.7 55.9 56.6 56.9 S6.9 57.0 57.3 57.2 ~n x 10 152 142 143 145 150 146 156 160 BlCV ~ 5;8 7.9 7.9 6.3 7.0 6.5 9.1 6.3 Density,gQs/cc 1.3996 1.3999 1.4007 1.4011 1.4011 1.4013 1.4016 1.4015 Yleld Point Tenscity, gpd 0.89 0.97 1.04 1.11 1.19 1.25 1.33 1.30 ... .. . . -20~9~5~
Example II
In the following set of experimen~al runs, a conventional polyester (PET, IV-0.63) was spun. The column temperatures were varied as indicated (air temperature, center of zones). The column length was 6.4 meters. The polymer was extruded at a rate of 23.1 pounds per hour through a spinning beam at 300C and a 72 hole spinneret (hole size o.Oo9 inches by 0.012 inches). The fibers were not quenched. The spun fibers were subsequently drawn (as indicated).
The results are set forth in TABLE II.

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TABLE II
No. 1 No._4No. 5 No. 2No. 3No. 6 No. 7 Spin Speed-fpm-lOOO's 10.5 10.5 10.5 12.5 12.5 12.5 12.S
Hot Quench-scfm/C 6/230 Air Bleed*-scfm/C 30/35 Col. Temp Top C70 68 120 80 98 121 135 2nd C83 101 99 81 88 101 107 3rd C75 88 85 75 78 86 88 Bottom C 62 72 79 64 65 80 81 Spun: Denier 370 367 369 344 342 342 342 Tenacity-gpd 2.87 3.68 3.77 3.50 3.72 3.86 3.75 Elong-~ 122 81.8 83.2 82.6 79.6 70.9 69.0 I~M~-gpd/ioo% 63 93 93 86 86 73 75 HAS-~ 350F65.5 27.2 41.0 49.5 42.0 11.2 9.5 Uster-~ 1.38 1.14 1.41 '.99 1.13 1.23 2.29 Finish-~ '1.82 .44 .74 .96 .85 .50 .54 IV 3 . .63 .64 .64 .64 .64 .64 .64 ~n x 10 78 11,5 113 105 111 107 106 3 Cryst~11.0 17.9 16.6 14.8 15.9 20.5 24.7 Max Draw Ratio (D.R.)1.70 1.80 1.80 1.60 1.57 1.77 1.74 Denier 224 210 213 218 227 202 206 ' Tenacity-gpd5.60 8.72 8.63 7.31 7.04 8.74 8.67 elong-~ 18.4 8.9 8.6 11.0 11.6 7.5 8.1 l.M.-gpd/100~ 92 137 133 127 110 146 140 HAS~ 350-F 6.2 10.0 9.8 9.2 7.8 10.0 lO.0 M~x D.R. - .03 1.65 1.77 1.77 1.S4 1.54 1.74 1.72 Denler 230 214 217 227 231 205 205 Tenaclty-gpt5.34 8.30 8.72 7.04 7.09 8.61 8.31 Elong~ 19.9 9.3 9.2 13.1 13.1 7.7 7.6 I,M. gpt/100~ 82 120 137 123 107 145 124 HAS~ 350'F 6.0 9.8 10.0 9.0 7.8 10.2 10.0 *Alr sparger, item 17, Figure 1 In the above set of experimental runs (i.e., those set forth in TABLE II), Nos. 4, 5, 6 and 7 represent the instant invention.

Example III
In the following sets of experimental runs, conventional polyester (PET, IV-0.63) was spun. The fibers were wound up at a rate - ~ .

~)3~8~
of 10,500 fpm. The polymer was extruded at a rate of 19.5 pounds per hour through a 72 hole spinneret (hole size 0.009 inches by 0. 012 inches) and a spinning beam at 300C. The fibers were quenched with 6.5 scfm air at 232C. The column was 6.4 meters long and divided into 4 sections having the following air temperature profile (in descending order): 135C; 111C; 92C; and 83C at the center of the zones. The spun yarn had the following properties: denier - 334;
tenacity - 4.09 gpd; elongation 71.7% initial modulus - 55.0 gpd/100%; hot air shrinkage - 11.8% at 350F.; Uster 1.10; I.V.
-0.647: FOY - 0. 35%, birefringence - 110 x 10 3; and cry tallinity -21.6%.

In TABLE IIIA, the effect of draw ratio on drawn yarn properties ig illustratQd.

TABLE IIIA

Draw_Ratlo _ _ 1.65 1.60 1.54 Den er 209 218 226 Tenacity gpd 8.15 7.53 7.12 Elongatlon % 8.4 3.9 10.4 Inltlal Modulus gpd/100O 123 115 115 Hot Alr Shrinkage % 350 F 12.0 12.4 12.0 In Table III13, the effect of the heating method during stretching is illustrated (the draw ratio was 1.65 and the yarn was not ,relaxed).

.

20398~1 TABLE IIIB
Hot Air Feed Hot Draw Initial Shrinkage Roll Plate Roll Denier TenrlcitY ElonR~ion Modulus 350F Temp. TemP. Temp.
gpd ~ gpd/L00~ ~ C C C
334 4.09 71.7 55 11.8 (As Spun) 209 8.15 8.4 12312.0 Amb 245 Amb 214 6.67 9.2 95 19.0 78 Amb Amb 212 8.05 9.3 86 8.0 78 245 A~b 209 8.05 9.0 93 9.0 78 Amb 200 211 8.45 9.1 110 9.2 78 245 200 211 7.96 8.8 110 9.2 100 245 200 211 8.18 9.2 108 9.2 120 245 200 In Table IIIC, the effect of higher drawing temperatures and draw ratios is illustrated (the feed roll is at ambient temperature and the draw roll is at 240C).

TABLE IIIC
Draw Ratio 1.76 1.72 1.70 1.67 1.64 1.61 D~nier 195 194 199 203 209 208 Tenac~ty gpd9.50 9.22 8.89 8.73 7.76 6.71 Elongatlon ~ 6.1 6.1 6.3 6.7 6.6 7.5 Hot Alr Shrlnkago ~-350F 6.8 7.0 6.86.5 6.8 6.5 Example IV
In the following set of experimental runs, a conventional polye~ter (PET, IV-0.92) wa~ spun. In runs Nos. 1-5, the fibers were spun and drawn in accordance with the methods set forth in U. S.
Patent Nos. 4,101,525 and 4,195,052. NOB. 6-9 were made as follows:

PET with a molecular weight characterized by an I.V. of 0.92 was drlod to a moi~ture level of 0.001% or less. This polymer was melted , ~ .

203~
and heated to a temperature of 295C in an extruder and subse~uently forwarded to a spinning pack by a metering pump. This pack was of an annular design, and provided filtration of the polymer by passing it through a bed of f inely divided metal particles. After f iltration the polymer was extruded through an 80 hole spinneret. Each spinneret hole had a round cross section with a diameter of 0.457 mm and a capillary length of 0.610 mm.

An insulated heated tube 9 meters in length was mounted snugly below the pack and the multifilament spinning threadline passed through the entire length of thi~ tube before being converged or coming into contact with any guide surfaces. The tube was divided down its length into seven zones for the purposes of temperature control. Individual controllers were used to set the air temperature at the center of each of these zones. Using a combination of process heat and the external heaters around the tube, individual controller settlngs were selected to arrive at a uniform air temperature profile down the vertical dlstance of this tube. In a typical situation the air temperature was 155C at the top zone of the tube and the temperature was reduced ln an approxlmately uniform gradie~t to 50C
at the bottom.

Approximately 10 cm below the tube the threadline was brought into contact with a finish applicator which also served as the convergence guide and the first contact that the yarn encountered. At the exit of the tube the cross section o~ the un-converged yarn was 21~3~51 very small due to the proximity of the finish guide. This pexmitted a very small aperture to be used, thus minimizing the amount of hot air lost from the tube.

Following the application of spin finish the yarn was taken to a pair of godet rolls and then to a tension controlled winder. Wind up speeds were typically in the range 3200 - 4100 mpm.

Drawing of this yarn was effected in a second step, in which the as spun yarn was passed over one set of pretension rolls to a heated feed roll maintained at a temperature set between 80 and 150C. The yarn was then drawn between these rolls and a set of draw rolls maintained at a set point chosen in the range 180 to 255C. A typical draw ratio for a spun yarn made at 3800 mpm would be 1.65, with samples spun at higher and lower speeds requiring lower or higher draw ratios, respectively.

The results are set forth in TABLE IV.

2~39~1 .
T~LE IV
Fecd Roll Ten~erature C

InitiR~ Initi6~
Ten~cityMcdulus Dr~n Y-rnTenoc~ty Modu~ Dr~n rarn sPd ~ OOX Shrink~e % gpd ~d/100X Shr~nkl~g~ X
SpimingS~ flrn 150-F 350-F
Speed 3irefringence ~o. ~f~n) x10 3 5000 21.9 7.94 115.00 7.30 5.9~ ~8,00 5.30 26000 30.1 7.85 118.W 7.00 6.90 103.00 6.70 3 7W0 45.2 3.3S 120.00 7.00 7.21 108.00 6.50 -4 ôO00 60.5 ~.51 130.00 7.80 7.31 113.00 6.00 59000 7~ 8.56 122.00 6.80 7.67 110.00 6.00 610500 104 9.52 158.00 7.50 10.94173.00 7.30 711500 115 9.03 150.00 6.80 9.52 152.00 7.00 812500 121 9.08 152.00 7.50 9.53 160.00 7.30 913500 119 9.32 15~.00 6.00 9.58 161.00 ~.?0 EXAMPLE V
Polyester with a molecular weight characterized by an I.V. of 0.92 was dried to a moisture level of 0.001%. This polymer was melted and heated to a temperature of 295C ln an extruder and the melt subsequently forwarded to a spinning pack by a metering pump. After filtration in a bed of finely divided metal particles, the polymer was oxtrudod through an 80 hole spinneret. ~ach spinneret hole had a dia~-ter of 0.457 mm and a capillary length o~ 0.610 mm. on extrusion the measurQd I.V. of this polymer was 0.84.

, The extruded polymer was spun into heated cylindrical cavity 9 meters in length. An approximately linear temperature profile ~gradient) was maintained over the length of thls tube. At the center of the top zone the air temperature was 155C and at the bottom of the ....

2 ~ 3 ~
tube this temperature was 50C. The multifilament yarn bundle was not converged until it came in contact with a finish guide just below the exit of the heated tube. From this point the yarn was advanced by a pair of godet rolls to a tension controlled winder. Und~r these conditions a series of four spun yarns were made at dif~erent splnning (wind-up) speeds. These yarns are referred to as examples A through D
in Table V. A.

In another series of experiments the heated tube was shortened by taking out some of its removable sections. Examples E and F in Table V. A were spun through 7 and 5 meter columns. Other polymers with different molecular weights (I.V.'s) were also spun on this system to give Examples G and H. Example I in Table VA illustrates a case in which lower column temperatures were used. In this case a linear gradient from 125C to 50C was established down the column.

All spun yarns in the series A through I were drawn in a single stage proCess using an ambient feed roll and a 245C draw roll.

In a rurther serles of tests the same spun yarn which was described in Example A was drawn using different feed roll temperatures. The results from testing these yarns are given in Examples A, J and K in Table V. 3.

2~3~
TABLE V. A
S~innin~ Conds Spin Temp Spun Spun Yarn Draw Drawn Yarn Exa~ple LenRth Speed C _V Bir Cryst Ratio Ten I.M. HAS
mpm ~ gpd gpd/100~ ~-350F
A 9 3200 155 0.84 .104 30.5 1.89 9.52 158 7.s B 9 3500 155 0.84 .115 34~4 1.79 9.03 150 6.8 C 9 3800 155 0.84 .121 35.9 1.74 9.08 152 7.5 D 9 4100 155 0.84 .119 38.9 1.72 9.32 154 6.0 E 7 3200 155 0.84 .101 30.1 1.79 8.99 142 7.3 F 5 3200 155 0.84 .073 25.0 1.98 9.52 159 7.0 G 9 3200 155 0.76 .110 34.0 1.65 8.63 123 6.0 H 9 3200 155 0.66 .102 22.9 1.57 7.25 110 5.0 I 9 4100 125 0.84 .120 31.9 1.53 7.34 116 5.3 TABLE V. ~ -Feed Roll Draw Drawn Drawn Hot Air ExampleTemp C RatioTenacityI Modulus Shrink gpd gpd/100% ~-350F
A 25 1.89 9.52 158 7.5 J 90 1.82 10.94 173 7.7 K 150 1.87 10.30 158 7.4 EXUiMPLE VI

In the ~ollowing experimental run, a conventional polymer, nylon, was spun accordlng to the inventive process and compared to nylon made by conventlonal processes.

The nylon made by the inventive process was spun under the ~ollowing conditions: throughput- 37 lbs. per hour; spinning speed -2,362 fpm; denier - 3500; number of filaments - 68; spun relative viscosity - 3.21 (H2 S04) or 68.4 ~HCOOH equiv.) quench air - 72 scfm;
winding tension 80g; column length - 24 ~t; column temperature top 240C and bottom 48C. The as-spun properties o~ thls yarn were as .

2 [139~
follows: tenacity - 0.95 gpd; elongation 235% TEl/2 - 14.6.
Thereafter the yarn was drawn under the following conditions: draw ratio 3.03; draw temperature 90C. The drawn yarn properties are as follows: tenacity 6.2 gpd: elongation -70%: TEl/2 - 52: 10% modulus -0.87 gpd; hot air shrinkage (HAS) at 400F - 1.4%.

One comparative nylon was spun in the following conventional fashion: throughput - 23.4 lbs. per hour, spinning speed - 843 fpm:
denier - 5556; number of filaments - 180; spun relative viscosity -3.3 (H2 S04) or 72.1 (HCOOH equiv.): quench - 150 scfm. Thereafter, the yarn was drawn under the following conditions: Draw ratio - 2.01;
draw temperature - 90C. The drawn yarn properties are as follows:
tenacity 3.8 gpd: elongation - 89%: TEl/2 - 33; 10% modulus - .55 gpd.

Another comparative yarn was spun in the following conventional ~ashion: throughput - 57.5 lbs. per hour; spinning speed - 1048 fpm;
denier - 12400; number of filaments - 240; spun relative viscosity -42 (HCOOH equlv.); quench air - 150 scfm. Thereafter, the yarn was drawn under the following conditions: draw ratio - 3.60; draw tamperature - 110C. The drawn yarn properties ar~ as follows:
tenacity - 3.6 gpd; elongation - 70%; TEl/2 - 30.1~ modulus at 10%
elongation - 0.8 gpd; HAS (at 400F) - 2.0%.

EXAMPLE VII
In the followlng experimental runs, low I.V. (e.g. 0.63) and high I.V. ~e.g. 0.92) conventlonal polyester (i.e. PET) as gpun yarn is compared with as spun yarn set ~orth in U.S. Patent No. 4,134,8~2.

2~3~
Examples 1-8 are low I.V. polyester (PET~ and are made in the manner set forth in Exa~ple I. Examples 9-ll are high I.V. polyester (PET) and are made in the manner set forth in Example V. Examples 12-17 correspond to Examples l, 5, 12, 17, 36 and 20 of U.S. Patent No.
4~134~8a2.

For each example, the spinning speed (fpm), density (gms/cc), crystal size (~, OlO), long period spacing (LPS), birefringence (biref.), crystal birefringence and amorphous birefringence are given.
The results are set forth in Table VII.
TABLE VII
Spin CS LPS
Speed Density 0~0 0 Crystal Amorphous No. (fpm) ~ms/cc A A Biref.Biref. Biref.

1 12500 1.3728 45 147 0.10800.1982 0.067 2 13500 1.3742 45 160 0.10600.1994 0.061 3 14500 1.3766 47 155 0.11500.2004 0.070 4 15500 1.3788 50 158 0.11200.2021 0.060 16500 1.3804 51 145 0.11800.2035 0 066 6 17500 1.3827 53 152 0.12400.2042 0 071 ~ 18500 1.3840 55 147 0.12700.2055 0.073 8 19000 1.3841 54 150 0.13000.2052 0.078 9 10000 1.3485 21 192 0.07610.1824 0.063 10000 1.3653 43 192 0.10470.1930 0.075 11 12500 1.3749 52 183 0.12150.1994 0.083 12 16500 1.3700 61 313 0.09580.2010 0 045 13 1800G 1.3770 73 329 0.10820.2010 0 057 14 19500 1.3887 72 325 0.11530.2030 0.054 lS 21000 1.3868 68 330 0.12410.2050 0.063 16 21000 1.3835 64 0.12360.1980 0.073 17 16500 1.3766 65 0.09650.2060 0.038 The present invention may be embodied in other specific forms without departing from the spirit or essential attributes thereof and, accordlngly, re~erence should be made to the appended claims, rather than to the ~oregoing speci~ication, as indicating ths scope of the invention.

Claims (9)

1. A polyester drawn yarn being characterized by: an initial secant modulus greater than 150 grams per denier/100%.

2. The polyester drawn yarn according to claim 1 being further chracterized by: a shrinkage of less than 8%.

3. The polyester drawn yarn according to claim 1 being further characterized by: a tenacity greater than 7.5 grams per denier.

4. A polyester drawn yarn being characterized by:
a tenacity of at least 7.5 grams per denier:
an initial secant modulus of at least 150 grams per denier/100%; and a shrinkage of less than 8%.

5. A polyester drawn yarn being characterized by a tenacity of at least 8.5 grams per denier, an initial secant modulus of at least 150 grams per denier/100%; and a shrinkage of less than 8%.

6. A polyester drawn yarn being characterized by a tenacity of at least 10 grams per denier, an initial secant modulus of at least 120 grams per denier/100%; and a shrinkage of less than 8%.

7. A polyester drawn yarn being characterized by a tenacity greater than 9.0 grams per denier, an initial secant modulus greater than 150 grams per denier/100%, and a shrinkage of less than 7.5%.

8. The yarn according to claims 1 or 4 or 5 or 6 or 7 wherein said polyester is polyethylene terephthalate.

9. The yarn according to claims 1 or 4 or 5 or 6 or 7 wherein said yarn comprises a plurality of fibers having a denier per filament ranging from about 1.5 to about 6.