EP0579083B1 - Method of drawing heated yarns, thereby obtained polyester yarns and their end uses - Google Patents

Description

The present invention relates to a method using the same high-speed yarns quickly, gently and evenly across the cross-section a desired elevated temperature can be heated, polyester multifilaments higher Strength, high modulus and low shrinkage, which after the Process according to the invention can be produced, and the use these fibers as reinforcing materials or for the production of textiles Fabrics.

Play in the technique of manufacturing and processing yarn Heating processes play a major role; there are therefore already a large number of Heating methods and heating devices are known (see for example DE-A-1 660 314).

These methods and devices can be, for example, according to the type of Differentiate heat input. So it is common to use heat Heat transfer media, such as by means of heated liquids or Gases to be fed by contacting the thread. It is also common that Heat by radiation from heated surfaces or by contact with to transfer heated surfaces.

Also in a number of processing processes of high-speed yarns, e.g. heating is required when stretching or fixing. It is general known that in such processes the heat as quickly and gently as possible should be fed.

As is known, the speed of heat transfer depends essentially on Temperature differences between the heat supplier and the object to be heated. Around To achieve the fastest possible heat transfer is usually chosen as far as possible high excess temperatures of the heating medium. An excessively high temperature however leads to overheating of parts of the yarn bundle, such as those hanging out Single filaments or loops. The demands for faster and gentle treatment is therefore in the opposite direction.

DE-A-3,431,831 describes a process for drawing polyester yarns known in which is stretched on a strip mill. The procedure is at reduced speeds. Details on how to heat the This document does not show running yarns.

From EP-A-114,298 a heating chamber for running yarns is known, in which the threads are treated with saturated water vapor of more than 2 bar. The Heating chamber is through a special way of sealing the yarn entry and exit characterized with a good sealing effect, which is a simple Threading allowed and with a quick adjustment of the operating state threading is possible. After the description, the heat transfer takes place especially through condensation of the saturated steam on the yarn in the heating chamber, whereby a high uniformity of the treatment temperature is achieved. The Yarn emerging from the heating chamber generally contains condensed yarn Water that evaporates again in the following steps. The The treatment temperature in this heating chamber cannot easily be varied, since it corresponds to the temperature of the saturated steam.

A heating device for a crimping machine is known from EP-A-193,891. This device has a thread guide tube heated on its outer circumference on, which is arranged vertically or obliquely. To improve the Heat transfer to the running yarn is on the yarn inlet side of the Thread guide tube set an air nozzle through which fresh air into the Thread running ear is blown. With this device, the heat treatment be made more effective. The actual heating of the fresh air takes place only in the heating device itself. With this heating device no one can Heat treatment can be carried out at constant temperatures since the Air in the thread guide tube has an undefined temperature.

DE-A-2,927,032 discloses a device for texturing yarns, in which these are heated directly in thread channels through which warm air flows. The thread channels are fed with the warm air and are equipped with a suction pipe connected. The device is through a special arrangement of the feed and Discharges for the hot air and the heater for the hot air featured; Furthermore, inlet and outlet nozzles are on the thread channels for the supply and removal of the yarns provided. With the arrangement described precise temperature control and a large temperature equality within the Device can be achieved. The yarns are from an even flow of hot air directly surrounding, which means an even heating of the yarns at constant Temperature and air speed results. The device requires suction the used warm air via a separate suction pipe.

From DE utility model 83 12 985 is a device for texturing Yarns known in which a heating device is provided, in which Warm air heats a running yarn in a thread channel. The device is through the special type of air flow in the thread channel, each one Flow line between at least two return lines for the hot air having. With the device, the lowest possible temperature drop in Thread channel can be achieved between its input and output. The yarn will similar to an injector nozzle hit at one point by the hot air and then yarn and air move together or opposite, whereby the Air loses temperature.

GB-A-1,216,519 describes a method for heating a thermoplastic Yarn known, using a device designed as a contact heater becomes. In this process, a continuously moving yarn is passed through a thread channel configured as a capillary. The inner diameter of the Thread channel is chosen so that fluids do not exist within this channel can move freely, but due to the capillary nature of the thread channel results in a sealing effect. A pressure is placed in this thread channel standing heating fluid, for example air, superheated steam or saturated steam, initiated so that this along the direction of yarn together with the The yarn can move through the heating channel and the yarn is plasticized by contact. Due to the construction of this device, it can be assumed that a strong temperature gradient along the yarn running direction in the thread running channel builds up and that due to the small amounts of heating fluid in the capillary of Thread channel must be worked with a temperature of the heating fluid that far is above the desired yarn temperature.

DE-PS-967,805 describes a method and a device for fixing known yarns when generating false twist. The procedure involves the contactless movement of a surface-moistened and twisted yarn by a heater that contains hot air. The fixation the false twist takes place using a high relative movement between the hot air and the moving yarn. According to the description, it will Process designed so that there is a high temperature gradient between the Hot air and the yarn trains; the surface is then moistened the purpose of protecting the yarn from thermal damage.

DE-AS-1,908,594 describes a device for the heat treatment of relaxed synthetic yarn known in which a yarn through a hollow Heating cylinder is passed. At the yarn inlet, one with a primary gas flow is off Fuel gas operated injector is provided, which is designed as an annular nozzle, and a additional inlet for a secondary gas flow. The device is thereby characterized in that the additional inlet for the secondary gas stream so is arranged that this current seen in the direction of movement of the yarn behind the injector orifice in the heating cylinder meets the primary gas flow. The device is intended to avoid the formation of eddies in the heating cylinder and the quality of the treated yarns should be improved. The danger of Vortex formation occurs because the primary gas flow is relatively high Speed enters the heating cylinder and slows down there.

DE-A-2,347,139 describes a method for texturing thermoplastic Yarn known that fixation of the twisted yarn by means of hot steam includes the speed of sound through the heater is passed through. The heating medium is also supplied here at the yarn entry point of the heating device by means of an annular nozzle. The procedure is characterized by high productivity. The yarn is heated by contact with a comparatively small mass of turbulent, fast flowing steam, this steam being a compared to desired end temperature of the running yarn has increased temperature.

Finally, DE-A-3,344,215 is a yarn heater with a heated yarn path known. This heater is characterized in that it contains means by which a heated medium in the area of the yarn inlet on a lengthways this Moving yarn strikes. The supply of the heating medium is also done here by means of an annular nozzle. With the heater, the heating output should be increased so that shorter heaters can be used than usual. This publication provides details on the temperature profile in the thread channel not to be removed.

With these previously known methods of heating yarn either come no high-speed yarns to use or in the case of high-speed ones Yarns are sometimes set to high temperatures in the heating unit, to keep the desired temperatures on the running yarn with short dwell times reach, or you get larger in the thread channel of the heating devices Temperature gradients, e.g. Turbulence of the heating medium occur. Inevitably, the heating takes place unevenly from the outside in the yarn or in the bundle of yarn. The quality of the treated yarns or Yarn bundles thus generally leave something to be desired. One generally poses found that rapid and increased heating resulted in a decrease in the Strength or lead to uneven dye absorption of the yarn, because Parts of the yarn bundle are heated unevenly.

Other known heating methods in which the most uniform possible Heating of the yarn in the thread channel is required, require a special one Management of the heating medium and are difficult to implement.

The object of the present invention was to provide a simple method for To provide stretching of heated free-running yarn in the said Yarns should be warmed as gently and evenly as possible.

It has now surprisingly been found that one can contact by a Heating device high-speed yarns, which are moving at a speed of more than 300 m / min based on the speed of the yarn when leaving the heating device, move in a gentle manner in a can heat and stretch the desired elevated temperature.

i) Vorerwärmen eines Wärmeüberträgergases auf eine Temperatur, die oberhalb der gewünschten Garntemperatur liegt,

ii) Zuführen des vorerwärmten Wärmeüberträgergases in den Fadenkanal, so daß dieses im wesentlichen senkrecht auf das laufende Garn entlang einer solchen Länge einströmt, daß sich das Garn innerhalb der Erhitzungsvorrichtung auf die gewünschte erhöhte Temperatur erwärmt, und wobei die Länge der Anblaszone so gewählt wird, daß durch ständiges Wegreißen der Grenzschicht durch die Anströmung des Wärmeüberträgergases das Garn direkt mit diesem in Kontakt kommt und somit eine sehr rasche Aufheizung des Garns erfolgt, und

iii) Spannen des berührungslos durch die Erhitzungsvorrichtung laufenden Garns in einer solchen Weise, daß dieses beim Durchlaufen durch besagte Erhitzungsvorrichtung eine Verstreckung erfährt.

The method according to the invention comprises the following measures:

i) preheating a heat transfer gas to a temperature which is above the desired yarn temperature,

ii) supplying the preheated heat transfer gas into the thread channel so that it flows essentially perpendicularly to the running yarn along a length such that the yarn within the heating device heats up to the desired elevated temperature and the length of the blowing zone is chosen so that by continuously tearing away the boundary layer due to the flow of the heat transfer gas, the yarn comes into direct contact with it and thus the yarn heats up very quickly, and

iii) tensioning the yarn running contactlessly through the heating device in such a way that it undergoes drawing as it passes through said heating device.

In the method according to the invention, the yarn is blown over a certain length with a uniformly heated heat transfer gas, so that the heat transfer process takes place more by movement of the heat transfer gas (convection) than by heat transfer by means of a temperature gradient. Through this type of blowing, the adhering air boundary layer, which counteracts the heat transfer due to its insulating effect, is blown away over a longer yarn path and the heated heat transfer gas can release its heat quickly and evenly to the yarn. The temperature of the heat transfer gas only needs to be a little above the yarn temperature, because most of the heat is transported by convective air movement and only a small part by temperature differences. This convective type of heat transfer is very efficient and overheating of the yarn material is avoided, so that gentle and uniform heating is achieved.
In the context of this invention, the term “yarn” is understood to mean all endless threads, that is to say both multifilament yarns and staple fiber yarns or monofilaments. Depending on the area of application, yarn titres of 50 to 2500 dtex are customary, preferably yarn titres of 50 to 300 dtex (for textile applications) and 200 to 2000 dtex (for technical applications).
The term "fiber" is understood in the context of this invention as a generic term in its broadest meaning, for example as yarn or as staple fiber. With regard to the fiber-forming material, the method according to the invention is not subject to any restrictions. Both yarns made from inorganic material, for example glass, carbon or metal yarns, and yarns made from organic material, e.g. yarns based on aliphatic or aromatic polyamide, polyester, in particular polyethylene terephthalate, or polyacrylonitrile, can be used.

In the context of this invention, the term “high-speed” is customary Speeds of more than 300 m / min, preferably 400 to 6000 m / min, to understand in particular 400 to 3000 m / min; this information relates to the speed of exiting the heater.

Any gases can be used as the heat transfer gas the yarn to be heated is inert under the respective treatment conditions are. Examples of such gases are nitrogen, argon or, in particular, air. The Gases can also contain additives, for example a certain content of Humidity; however, the moisture content must not be so high that in the Heating device a significant condensation takes place on the yarn.

The heat transfer gas can be preheated in any conventional manner will; for example by contact with a heat exchanger, passing through by heated pipes or by direct heating via heating spirals. The The temperature of the preheated heat transfer gas is higher than that in the individual case desired yarn temperature; the heat transfer gas is preferably heated to temperatures up to 20 ° C above and ensures that between the Preheating and the actual heating of the yarn is not worth mentioning Temperature drop occurs.

The heated heat transfer gas can be placed anywhere in the thread run channel be introduced. The heat transfer gas is preferably conducted to the Thread run channel in such a way that this along the entire thread run channel can come into contact with the yarn. The length is preferably the blowing zone to more than 6 cm, in particular to 6 to 200 cm. In the case, the length is that the heating device is integrated in a drawing step the blowing zone preferably to 6 to 20 cm. In the event that Heating device is integrated in a fixing step, the length of the Blow zone preferably to 6 to 120 cm, in particular 6 to 60 cm.

The heat transfer gas is preferably passed in perpendicular to the direction of the yarn the thread run channel, the heat transfer gas on the one hand from the current Yarn is entrained and the heating device through the yarn outlet leaves together with the running yarn, and on the other hand against the direction of the yarn moves and the heater over the yarn inlet leaves.

In a preferred embodiment, the heat transfer gas is in the middle Part of the thread channel over a length of about 1/4 to 1/2 of the channel length blown small openings perpendicular to the yarn and escapes in and against the thread running direction from the thread run channel. In a likewise preferred Modification of this embodiment is carried out with a cross-blowing Extraction on the opposite side.

Contacting the heat transfer gas in the heater with the running yarn has to take place under such conditions that the yarn within the heater to the desired elevated temperature heats up and the heat transfer gas practically in the heating device cools very little.

A number of measures are available to the expert with the help of which these specifications can be set. For example, it is possible to Comparison to the yarn mass moving through the thread channel per unit of time, relatively large masses of heat transfer gas per unit time through the To let thread channel flow, so that despite the effective and rapid Heat transfer to the yarn only a slight cooling of the Heat transfer gas results. In contrast to blowing on practically one The location of the moving yarn results when blowing along one certain zone a particularly intensive interaction of the heating gas with the Yarn, because the boundary layer between yarn and surrounding medium in this Zone is constantly being torn away. This way it is possible to use just one low temperature change of the gas to an effective heating of the yarn achieve. The control of the temperature profile of the heat transfer gas lets yourself by choosing the heat capacity of the gas or by the Control the flow rate of the gas in a manner known per se.

In particular, it is possible to control the individual positions or groups Regulate the heating power so that a predetermined temperature prevails on the thread, by using one or more sensors near the yarn via a control loop Control heating output. Because the time constant of electronic control loops is below of 1 second, starting operations can be regulated very quickly so that the proportion of pre-processed goods that are outside of the desired Specifications, is lowered, and loss wrap or transfer This eliminates the need for salable coils.

The temperature of the heat transfer gas in the heater changes are only insignificant under the operating conditions; i.e. this gas does not experience any noteworthy when passing through the heating device Temperature change. This is due to suitable insulation of the gas-carrying parts of the To achieve device.

A particular advantage is that the regulation described above the temperature loss of heat between the heater and yarn can be disregarded because the heating device after the Temperature is controlled near the yarn. This can make the elaborate Avoid wall heating in the air duct between the heater and yarn will. Even fluctuations in the insulation effect from place to place can be regulated by this type of regulation.

A particular advantage of the stretching process according to the invention is considered fibers with increased strength and high Dimensional stability can be generated. The upper limit of the temperature of the Heat transfer gas is less critical in the method according to the invention because the compact yarn because of its heat content of the hot gas temperature not follows immediately. Here, temperatures of Heat transfer gas can be worked that is higher than the melting temperature of the yarn material.

X_L =

Gasdurchsatz in Nm³/h (Nm = Normkubikmeter)

v =

Garngeschwindigkeit in m/min

fd =

Garntiter in dtex

c_pf =

Wärmekapazität des Garnmaterials in kJ/Kg * K

q_L =

Dichte des Wärmeüberträgergases in kg/m³

C_pl =

Wärmekapazität des Wärmeüberträgergases in kJ/Kg * K

An x _L value, which should preferably be exceeded, is used to estimate a suitable value for the throughput of the heat transfer gas through the heating device. This value x _L can be calculated using the following formula: X L = 1.5 * 10 -5 * (v * fd * c pf ) / (q L * C pl ). Here mean:

X _L =

Gas throughput in Nm ³ / h (Nm = standard cubic meter)

v =

Yarn speed in m / min

fd =

Yarn titer in dtex

c _pf =

Heat capacity of the yarn material in kJ / Kg * K

q _L =

Density of the heat transfer gas in kg / m ³

C _pl =

Heat capacity of the heat transfer gas in kJ / Kg * K

Preferred X _L values for a specific yarn material and heat transfer material are in the range of the values calculated by the above formula up to four times this value. A common X _L value is 2.2 Nm ³ / h.

In a particularly preferred variant, the method according to the invention can be in the production of high-strength multifilament yarns, preferably based on polyester, especially based on polyethylene terephthalate.

In the case of polyethylene terephthalate multifilaments, the temperature of the heat transfer gas controlled drawing / fixing temperature usually in the range from 160 to 250 ° C., preferably from 210 to 240 ° C. The Drawing tension is usually 1.5 to 3.0 cN / dtex, preferably 2.3 to 2.8 cN / dtex, based on the final titer.

In this way, polyester multifilament yarns stretched and fixed surprisingly have about 5 to 10 cN / tex higher strength than Polyester multifilament yarns using conventional heat sources have been stretched.

Unexpectedly, polyester fibers show that according to the invention Processes have been stretched in one step (e.g. stretching between delivery and Discharge godets with an intermediate heater), a very high one Degree of fixation and a very high degree of crystallization have low Residual shrinkage values and thus high dimensional stability. These fibers are After the single-stage stretching, technically usable as low-shrink fibers and have a shrinkage of less than 8% at 180 ° C.

In order to produce low-shrinkage polyester fibers by conventional methods a second stage of the process is necessary, in which part of the shrinkage at high Temperature is let out. Because of the decline in thread orientation when shrinking, these threads are susceptible to post-expansion in Finishing process. In contrast, the manufactured according to the invention Polyester fibers already have low shrinkage values with maximum orientation Molecules on. Subsequent expansion is then practically no longer possible. The on Fibers obtainable in this way can be determined by strength index Fl and molecular Orientation MO or through compliance NG and memory module index SP be marked.

The invention therefore also relates to polyester multifilaments obtainable by the drawing process according to the invention, which are characterized by the following properties: strength index F1 greater than or equal to 50, in particular 58 to 65, and molecular orientation MO greater than or equal to 20, in particular 25 to 35, or by resilience NG of less than or equal to 12, in particular from 2 to 8, and memory module index SP of greater than or equal to 100, in particular from 115 to 150, or by a combination of the parameters F1, MO, NG and SP in the ranges given above, where FI = a 1 * Q - a 2nd * There 2nd * S, MO = a 3rd * SG - a 2nd * There 2nd * S, NG = a 2nd * D + a 2nd * S - a 4th * KAO, and SP = a 1 * F - 4 * (a 2nd * D + a 2nd * S) + A 4th * KAO + a 3rd * SG - a 2nd * KG, where a ₁ = 1 * (tex / cN), a ₂ = 1 * (1 /%), a ₃ = 10 * (sec / km) and a ₄ = 10 * (1 /%), F is the tenacity in cN / tex, D the maximum tensile force elongation in%, S the shrinkage in% at 200 ° C measured in a convection oven, SG the speed of sound in km / sec measured at 25 ° C, KAO the crystallite axis orientation in% expressed by the "Hermannian orientation Function "and KG means the degree of crystallization in% measured by the method of the density gradient column.

The sizes on which the above definitions for FI, MO, NG and SP are based are determined as follows:

The tenacity F and the maximum tensile elongation D are according to DIN 53834 determined.

The shrink S is made by heat treatment in a forced air oven at 200 ° C and a dwell time of 5 minutes and then with a load that corresponds to the Weight of 500 meters of the original yarn is measured.

The speed of sound SG is with a load of 1 cN / dtex Dynamic Modulus Tester PPM-5 from Morgan & Co./Massachusetts USA measured.

The degree of crystallization KG is determined from the density according to the two-phase model, 1.331 g / cm ^{3 being} assumed for the density of the amorphous phase and 1.455 g / cm ³ for the density of the crystalline phase. The density is measured using the gradient method in zinc chloride / water.

The crystallite axis orientation KAO is expressed by the "Hermannian orientation function" f _c = 1/2 * (3 * <cos ² (theta)> - 1). The azimuthal intensity distribution of the (-1,0,5) reflex of polyethylene terephthalate is measured and from it calculated according to the formula f _{c given} above. The X-ray examinations were carried out using the X-ray diffractometer D 500 (Siemens) according to the method of Biangardi, publication series "Kunststoff-Forschung" 1, TU Berlin.

The polyester multifilaments according to the invention can advantageously be used on all of them Use areas in which high-strength, high-modulus and low-shrink fibers Find use.

The polyester multifilaments according to the invention are preferably used as Reinforcement materials for plastics or for the production of textiles Fabrics such as woven, knitted or crocheted.

A preferred area of use of the polyester multifilaments according to the invention relates to Use as reinforcing materials for elastomers, especially for Manufacture of vehicle tires or conveyor belts.

Another preferred use of the polyester multifilaments according to the invention relates to the manufacture of dimensionally stable textile fabrics, such as tarpaulins.

The following examples describe the invention without limiting it. In the values for Fl, MO, NG and SP given in these examples were calculated using the Definitions and measurements described above for F, D, S, SG, KAO and KG determined. Viscosity data in the following examples refer to the intrinsic viscosity. measured by solutions of the Polyester in o-chlorophenol at 25 ° C.

Examples 1 to 7:

Polyethylene terephthalate (PET) is melt-spun in the usual way and stretched over a single-stage drafting system consisting of delivery and withdrawal godets. Examples 1 to 6 describe embodiments in which the heating device according to the invention is used, while example 7 relates to a commercially available high-strength and high-modulus PET thread which has been produced without the heating device according to the invention. The following Tables Ia, Ib and Ic show the process conditions and the properties of the threads obtained.

The results in Table Ic are shown graphically in FIGS. 1 and 2.

Claims (20)

1. A process for drawing and heating yarns passing contactlessly through a heating apparatus at a high speed of more than 300 m/min, based on the speed of the yarn as it leaves the heating means, comprising the steps of:

   i) preheating a heat transfer gas to a temperature which is above the desired yarn temperature,

   ii) feeding the preheated heat transfer gas into the yarn duct so that it impinges essentially perpendicularly on the moving yarn along a length such that the yarn heats up to the desired elevated temperature within the heating apparatus, the length of the impingement zone being such that continuous removal of the boundary layer by the impinging heat transfer gas ensures that the yarn comes into direct contact with the heat transfer gas and thus heats up very rapidly, and

   iii) tensioning the yarn moving contactlessly through the heating apparatus in such a way that it undergoes drawing as it passes through said heating apparatus.
2. The process of claim 1, wherein the yarn duct is additionally heated.
3. The process of claim 1, wherein the heat transfer gas used is nitrogen, argon or in particular air.
4. The process of claim 1, wherein the heat transfer gas is applied to the yarn essentially along the entire path of the yarn in the heating apparatus.
5. The process of claim 1, wherein the heat transfer gas impinges on the moving yarn radially from out to in.
6. The process of claim 1, wherein the heat transfer gas is blown perpendicularly onto the yarn from small openings in the middle portion of the yarn duct over a length of about 1/4 to 1/2 of the duct length and escapes from the yarn duct in the yarn transport direction and in the opposite direction.
7. The process of any one of claims 1 to 6, wherein the heating is controlled by single-location or group control in such a way that the yarn is at a predetermined temperature by controlling the heating via a control circuit with one or more sensors in the vicinity of the yarn.
8. The process of claim 1, wherein the heat transfer gas throughput through the heating apparatus in standard m³/h is at least x_L, x_L being determined by the formula xL = 1.5*10-5 * (v * fd * cpf) /(qL * cpl) where v is the yarn speed in m/min, fd is the yarn linear density in dtex, c_pf is the heat capacity of the yarn material in kJ/(kg * K), q_L is the density of the heat transfer gas in kg/m³, and c_pl is the heat capacity of the heat transfer gas in kJ/(kg * K).
9. The process of claim 8, wherein the heat transfer gas throughput through the heating apparatus is between x_L and 4 * x_L.
10. The process of claim 1, wherein the yarn is a multifilament yarn based on polyester, in particular on polyethylene terephthalate, the heat transfer gas is preheated to a temperature of from 160 to 250°C, and the drawing tension is set to from 1.5 to 3.0 cN/dtex, preferably from 2.3 to 2.8 cN/dtex, based on the final linear density.
11. The process of claim 1, wherein the drawing of the yarn takes place in a single stage.
12. Polyester multifilament yarns having a yarn linear density of 50-2500 dtex, obtained by the process of at least one of claims 1-11, having a tenacity index TI equal to or greater than 50 and a molecular orientation MO equal to or greater than 20, where TI = a1 * T - a2 * BE - a2 * S, and MO = a3 * SS - a2 * BE - a2 * S, in which a₁ = 1 * (tex/cN), a₂ = 1 * (1/%) and a₃ = 10 * (sec/km), T is the tenacity in cN/tex, BE is the breaking extension in %, S is the shrinkage in % measured at 200°C in a through-circulation oven and SS is the speed of sound in km/sec measured at 25°C.
13. The polyester multifilament yarns of claim 12 having a compliance COM equal to or less than 12 and a storage modulus index SMI equal to or greater than 100, where COM = a2 * BE + a2 * S - a4 * CAO, and SMI = a1 * T - 4 * (a2 * BE + a2 * S) + A4 * CAO + a3 * SS - a2 * DC, in which a₁ = 1 * (tex/cN), a₂ = 1 * (1/%), a₃ = 10 * (sec/km) and a₄ = 10 * (1/%), T is the tenacity in cN/tex, BE is the breaking extension in %, S is the shrinkage in % measured at 200°C in a through-circulation oven, SS is the speed of sound in km/sec measured at 25°C, CAO is the crystallite axial orientation in % expressed by the Hermann orientation function, and DC is the degree of crystallization in % measured by the method of the density gradient column.
14. The polyester multifilament yarns of claims 12 and 13 having a tenacity index TI equal to or greater than 50, a molecular orientation MO equal to or greater than 20, a compliance COM equal to or less than 12 and a storage modulus index SMI equal to or greater than 100, where TI, MO, COM and SMI are each as defined in claims 12 and 13.
15. The polyester multifilament yarns of any one of claims 12 to 14, wherein TI is from 58 to 65, MO is from 25 to 35, COM is from 2 to 8 and SMI is from 115 to 150.
16. The polyester multifilament yarns of any one of claims 12 to 15, wherein the polyester is polyethylene terephthalate.
17. The use of the polyester multifilament yarns of any one of claims 12 to 16 as reinforcing materials for plastics or for producing textile fabrics.
18. The use of the polyester multifilament yarns of any one of claims 12-16 as reinforcing materials for elastomers.
19. The use of the polyester multifilament yarns of any one of claims 12-16 for producing vehicle tires or conveyor belts.
20. The use of the polyester multifilament yarns of any one of claims 12-16 for producing dimensionally stable textile fabrics, in particular tarpaulins.

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