Antimony-free polyester industrial yarn and melt direct spinning production process thereof

Abstract

The invention discloses an antimony-free polyester industrial yarn and a melt direct spinning production process thereof, and belongs to the technical field of new materials. In order to solve the problems of heavy metal antimony pollution and high production energy consumption in the existing polyester industrial yarn production, the invention adopts an antimony-free bimetallic coordination composite titanium catalyst, and the catalyst is formed by coordination of a titanium central atom, an oxalate ligand, a 1, 6-hexanediol ligand and zinc acetate. The process comprises the following steps: under the action of the catalyst, preparing a basic polyester melt from terephthalic acid and ethylene glycol through esterification and melt polycondensation; and carrying out a liquid-phase tackifying reaction on the basic melt at a relatively low temperature of 262-275 DEG C to obtain a high-viscosity polyester melt, and directly carrying out spinning forming and post-processing on the high-viscosity polyester melt. The invention also discloses the antimony-free polyester industrial yarn prepared by the process. The method is short in technological process and low in energy consumption, heavy metal pollution is completely eradicated from the source, and the prepared polyester industrial yarn has the advantages of being high in breaking strength and good in mechanical property uniformity.

Description

TECHNICAL FIELD

[0001] The present application belongs to the technical field of new materials, and particularly relates to an environmentally-friendly polyester fiber material and a production method thereof, and more particularly to a non-antimony polyester industrial yarn and a melt direct spinning production process thereof. BACKGROUND

[0002] Polyester (polyethylene terephthalate, PET) is the largest variety of chemical fibers, accounting for about 80% of the total output of chemical fibers. Among them, polyester industrial yarn, as a high-end product of polyester fiber, has a strength about twice that of ordinary textile and garment polyester fiber. Due to its outstanding cost performance, it is widely used in various industrial fields such as conveyor belts, automobile safety belts, tire cord, geotextiles, and its application range is still expanding.

[0003] However, the existing production technology of polyester industrial yarn mainly has the following two problems: First, in the polyester synthesis process, a compound containing heavy metal antimony is generally used as a catalyst. This leads to the possibility of heavy metal antimony being precipitated and entering the wastewater during the subsequent fiber or fabric dyeing process, causing water pollution. At the same time, the discarded polyester products containing antimony also pose a long-term pollution threat to the soil environment. In order to solve this problem, the industry has tried to use non-antimony titanium catalysts. However, the traditional titanium catalyst has too high reactivity, which significantly accelerates the side reactions while catalyzing the main reaction, resulting in high color value (yellowing) and low melt viscosity of the polyester product. These defects make titanium catalysts generally only suitable for producing ordinary polyester fibers with low intrinsic viscosity (such as 0.65~0.73 dL / g), and difficult to be used for preparing high intrinsic viscosity (such as 0.92 dL / g or higher) polyester meeting the requirements of industrial yarn, otherwise it will face technical bottlenecks such as difficulty in increasing viscosity, high yarn breakage rate, etc.

[0004] Second, in terms of production process, the traditional polyester industrial yarn production mostly uses the intermittent solid phase polycondensation (SSP) process. This process requires the polyester melt to be made into chips first, then the intrinsic viscosity of the chips is improved by solid phase viscosity increasing equipment, and finally the viscosity-increased chips are melted for spinning. This process not only involves repeated heating and cooling, resulting in long process flow and huge energy consumption, but also has high equipment investment cost. In recent years, although melt direct spinning technology using liquid phase viscosity increasing has appeared to replace solid phase polycondensation technology, the temperature of the melt viscosity increasing reaction, high viscosity melt conveying and spinning process of these technologies is usually maintained at 275~295℃, or even higher. Therefore, its production energy consumption still has room for further reduction. SUMMARY

[0005] The present application aims at the defects of heavy metal pollution caused by using antimony-containing catalyst, long production process, high energy consumption and unstable product quality in the existing production technology of polyester industrial yarn, and provides a melt direct spinning production process of antimony-free polyester industrial yarn, which realizes the continuous production of antimony-free polyester industrial yarn with low energy consumption and high quality by using a specially designed antimony-free bimetallic (titanium-zinc) coordination composite catalyst and combining with an optimized low-temperature melt direct spinning process.

[0006] In order to achieve the above application purposes, the present application adopts the following technical solutions: a melt direct spinning production process of antimony-free polyester industrial yarn comprises the following steps: a) performing esterification reaction and melt polycondensation reaction in the presence of a bimetallic coordination composite titanium catalyst without antimony, using terephthalic acid and ethylene glycol as reaction monomers, to prepare a base polyester melt; b) conveying the base polyester melt to a tackifying reactor to perform liquid phase tackifying reaction at a temperature of 262-275 DEG C, to obtain an industrial yarn grade high-tack polyester melt; c) directly spinning and forming the high-tack polyester melt and performing post-processing to prepare the antimony-free polyester industrial yarn; The bimetallic coordination composite titanium catalyst without antimony is a solid composite formed by coordination of titanium central atoms with oxalate ligands, 1,6-hexanediol ligands and zinc acetate, and the molar ratio of titanium to zinc is 1:1.2.

[0007] Further, the intrinsic viscosity of the base polyester melt is 0.60-0.75 dL / g, and the intrinsic viscosity of the industrial yarn grade high-tack melt is 0.92-1.25 dL / g.

[0008] Further, the amount of the catalyst is 1-20 ppm of the total mass of ethylene glycol and terephthalic acid based on the titanium metal content.

[0009] Further, a heat stabilizer is added when preparing the base polyester melt, and the main component of the heat stabilizer is a phosphite compound and a benzoic anhydride compound.

[0010] Further, the post-processing step comprises at least two drawing steps and two heat setting steps.

[0011] Further, the post-processing step adopts a process of three-stage drawing and two-stage heat setting, wherein the first-stage drawing temperature is 90-230 DEG C, and the first-stage heat setting temperature is 160-250 DEG C.

[0012] Further, the spinneret draw ratio in the spinning and forming process is 90-200, and the total draw ratio is 5.0-8.8.

[0013] A kind of antimony-free polyester industrial yarn is polymerized from terephthalic acid and ethylene glycol, and contains the residual of bimetallic catalyst of titanium and zinc, the catalyst is solid complex formed by titanium central atom and oxalate ligand, 1,6-hexanediol-based ligand and zinc acetate coordination, wherein the molar ratio of titanium and zinc is 1:1.2; And the breaking strength of the antimony-free polyester industrial yarn is 7.4~9.0 cN / dtex, the breaking elongation is 11.5~15.8%, and the dry heat shrinkage under the condition of 177℃×10min×0.05 cN / dtex is 2.1~7.5%.

[0014] Further, the CV value of breaking strength of the industrial yarn is not more than 2.5%, and the CV value of breaking elongation is not more than 6%.

[0015] Further, the elongation of the industrial yarn under the load of 4.0 cN / dtex is 2.4~7.5%.

[0016] Compared with the prior art, the present application has the following beneficial effects: 1. Green and environmentally friendly, eliminate heavy metal pollution: the present application uses a composite titanium catalyst without antimony to synthesize polyester from the source, which completely avoids the environmental pollution problem caused by the precipitation of heavy metal antimony during product production and use after being discarded.

[0017] 2. Energy saving, reducing production cost: the present application adopts melt direct spinning process, which eliminates the intermediate link of traditional solid phase polycondensation and avoids the huge energy consumption caused by repeated temperature rising and falling. More importantly, thanks to the efficient catalyst system, the melt polycondensation and tackifying reaction temperature of the present application can be controlled in the lower range of 262~275℃, which is significantly lower than the operating temperature of 275~295℃ of the existing melt direct spinning technology, further reducing the production energy consumption. At the same time, the simplified process flow also reduces the equipment investment cost.

[0018] 3. Excellent product quality and good uniformity: the bimetallic catalyst used in the present application effectively suppresses the side reaction through titanium-zinc divisional catalysis, solves the problems of product yellowing and viscosity reduction caused by traditional titanium catalyst, and obtains high-quality high-viscosity polyester melt. Combined with fine regulation of spinning and post-processing process, the final polyester industrial yarn has excellent properties such as high breaking strength (7.4~9.0 cN / dtex), stable breaking elongation, controllable dry heat shrinkage, and the CV values of strength and elongation are less than 2.5% and 6% respectively, indicating that the product performance is highly uniform and stable.

[0019] 4. Stable and controllable production process: The present application ensures the absolute uniformity of the melt quality and the controllable viscosity in the conveying process by implementing strict condition control and quality monitoring in each stage of the preparation of the base melt, the preparation of the high-viscosity melt, the melt conveying and the spinning forming, and optimizing the equipment layout (such as ensuring that the spinning unit is equidistant from the reactor), thereby laying a solid foundation for the stable performance of the final polyester industrial yarn and the stability of the spinning process. BRIEF DESCRIPTION OF DRAWINGS

[0020] Figure 1 is a process flow diagram of the present application. DETAILED DESCRIPTION

[0021] The technical solutions in the embodiments of the present application will be clearly and completely described below with reference to the drawings in the embodiments of the present application. Obviously, the described embodiments are only part of the embodiments of the present application, rather than all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art belong to the scope of protection of the present application.

[0022] The present application provides a kind of antimony-free polyester industrial yarn and its melt direct spinning production process. The core of this process is that by using a special designed, antimony-free double metal complex titanium catalyst, and matching a set of optimized low temperature melt direct spinning process, the continuous production of environment-friendly, low consumption, high quality polyester industrial yarn is realized.

[0023] As shown in Figure 1 The total process of the production process described in the present application is roughly as follows: first, terephthalic acid (PTA) and ethylene glycol (EG) are used as reaction monomers to prepare a base polyester melt with a specific viscosity by esterification and melt polycondensation reaction in the presence of the antimony-free double metal catalyst described in detail below. Subsequently, the base melt is sent to a liquid-phase viscosity-increasing reactor to carry out viscosity-increasing reaction at a lower temperature than the prior art, so as to obtain a high-viscosity polyester melt that meets the requirements of industrial yarn spinning. Finally, the high-viscosity melt is directly conveyed to the spinning assembly for spinning and forming without the solid-phase slicing step, and is subjected to a series of fine-tuned post-processing, and is finally wound into the finished antimony-free polyester industrial yarn.

[0024] A key technical core point of the present application is the antimony-free double metal complex titanium catalyst. The catalyst is a solid composite, which specifically comprises: titanium (Ti) as the central atom, and rigid oxalate ligand, flexible 1,6-hexanediol ligand and zinc acetate for coordination. The molar ratio of titanium to zinc is 1:1.2. Of course, the zinc here can be replaced by any one of magnesium, calcium, sodium and potassium.

[0025] The design of the catalyst overcomes the defects of traditional titanium-based catalysts, such as excessively high reactivity, easy initiation of side reactions, yellowing and thermal degradation of polyesters. The mechanism is as follows: 1. The synergistic effect of the rigid oxalate chelate structure and the hydrophobic barrier of the flexible hexanediol chain effectively resists the destruction of the catalyst by water generated by esterification, ensuring the catalytic activity and stability of the catalyst.

[0026] 2. Titanium and zinc form a bimetallic oxygen bridge structure, which realizes the division of labor of the catalytic function: titanium atoms dominate the ester exchange and polycondensation main reaction, while zinc atoms can effectively capture free radicals generated in the reaction process, thereby inhibiting the occurrence of side reactions.

[0027] 3. The 1,6-hexanediol chain segment has a "homologous segment self-dispersing" effect, which can effectively eliminate the local overheating points that may occur around the catalyst particles, thereby avoiding the thermal degradation and yellowing of the polyester.

[0028] Another key technical core of the present application is that, with the above-mentioned efficient and stable catalyst, the liquid-phase tackifying reaction of the present application can be efficiently carried out in a low temperature range of 262-275°C. This temperature is significantly lower than the reaction temperature of 275-295°C or higher commonly used in existing melt direct spinning technology, thereby greatly reducing the energy consumption of the production process.

[0029] The present application will be further described in detail through specific examples. It is worth mentioning that the equipment used in the present application is all existing technology, and the improvement point of the present application is the method, and the basic steps of melt direct spinning are also existing technology.

[0030] Example 1 This embodiment provides a preparation method of antimony-free polyester industrial yarn, and the specific steps are as follows: (1) Preparation of polyester melt: terephthalic acid (PTA) and ethylene glycol (EG) are fed according to the conventional molar ratio (for example, in the range of 1:1.1 to 1:1.5, and the best ratio is generally 1:1.2-1:1.3, the excess ethylene glycol ensures the generation of sufficient oligomers, and as a reaction medium, it is beneficial to the stirring and heat transfer of the slurry, making the reaction system more uniform), and a bimetallic coordination complex titanium-based catalyst is added as a catalyst. The addition amount of the catalyst is 1 ppm based on the titanium metal content in the final polyester. First, esterification is carried out at 230°C, and then melt polycondensation reaction is carried out at 265°C to prepare a base polyester melt with an intrinsic viscosity of 0.60 dL / g and a carboxyl end group content of 32 mol / t.

[0031] (2) Liquid phase tackifying: the above base polyester melt is sent into a liquid phase tackifying reactor, at a reaction temperature of 265°C, the melt residence time is controlled to be 20 minutes, to obtain an industrial yarn grade high tack polyester melt with an intrinsic viscosity of 0.92 dL / g and a carboxyl end group content of 30 mol / t. Preferably, 2 or more than 2 spinning units are connected to each tackifying reactor, each spinning unit is equidistant from the tackifying reactor, to ensure absolute uniformity of the melt viscosity and properties, and to avoid residence time differences. (The liquid phase tackifying residence time is long, and the viscosity is high).

[0032] (3) Spinning and post-processing (basic steps include metering pump metering, spinning assembly spinning, air blowing, cooling solidification, bundle oiling, drafting, heat setting, network processing, and winding forming in sequence): the high tack melt is transported to the spinning assembly through the melt pipeline, and the spinning assembly temperature is set to 275°C. After the melt is extruded through the spinneret, side blowing cooling is adopted, the blowing temperature is 20°C, the wind speed is 0.4 m / s, and the blowing humidity is 60%. Then three-stage drafting and two-stage heat setting are carried out, and the process parameters of each process are as follows: First pair of rollers (first-stage drafting): temperature 220°C, speed 400 m / min; Second pair of rollers (second-stage drafting): temperature 100°C, speed 450 m / min; Third pair of rollers (third-stage drafting): temperature 160°C, speed 1500 m / min; Fourth pair of rollers (first-stage heat setting): temperature 230°C, speed 2700 m / min; Fifth pair of rollers (second-stage heat setting): temperature 220°C, speed 2600 m / min; Sixth pair of rollers: speed 2400 m / min.

[0033] Among them, the length of the airless cooling in the cooling solidification stage is 0.4 m. The oiling stage adopts oil nozzle two-way oiling, the oil agent oiling rate is 0.2 ml / min, and the total oiling rate is 0.35%; the spinning head draw ratio during spinning is 90; the drafting ratio is 5.0; and the heat setting relaxation ratio is 1.05.

[0034] (4) Winding: after network processing, it is finally wound into shape at a speed of 3500 m / min.

[0035] (5) Product performance: the prepared antimony-free polyester industrial yarn has a breaking strength of 7.4 cN / dtex, an elongation at break of 15.8%, and a dry heat shrinkage rate of 7.5% under the condition of 177°C x 10 min x 0.05 cN / dtex. The CV value of breaking strength is 2.5%, and the CV value of elongation at break is 6%.

[0036] Example 2 This example is basically the same as Example 1, except that some process parameters are adjusted.

[0037] (1) Preparation of polyester melt: the amount of catalyst added is 20 ppm based on the titanium metal content in the final polyester. The esterification reaction temperature is 250°C, and the melt polycondensation reaction temperature is 275°C, to obtain a base polyester melt with an intrinsic viscosity of 0.75 dL / g and a carboxyl end group content of 12 mol / t.

[0038] (2) Liquid phase tackification: the liquid phase tackification reaction temperature is 275°C, and the melt residence time is 45 minutes, to obtain an industrial yarn grade high tack polyester melt with an intrinsic viscosity of 1.15 dL / g and a carboxyl end group content of 16 mol / t.

[0039] (3) Spinning and post-processing: the spinning assembly temperature is set to 290°C. The side blowing temperature is 25°C, and the wind speed is 0.7 m / s. The process parameters of each process are as follows: First pair of rollers (primary draft): temperature 235°C, speed 600 m / min; Second pair of rollers (secondary draft): temperature 130°C, speed 800 m / min; Third pair of rollers (tertiary draft): temperature 200°C, speed 2500 m / min; Fourth pair of rollers (primary heat setting): temperature 250°C, speed 3600 m / min; Fifth pair of rollers (secondary heat setting): temperature 235°C, speed 3800 m / min; Sixth pair of rollers: speed 3500 m / min.

[0040] Among them, the length of the cooling solidification stage without air cooling is 1.2 m. The oiling stage adopts two-way oiling with an oil nozzle, the oiling rate is 2 ml / min, and the total oiling rate is 1.1%; the spinneret draw ratio during spinning is 200; the draft ratio is 6.8; and the heat setting relaxation ratio is 0.93.

[0041] (4) Winding: finally wound into shape at a speed of 6000 m / min.

[0042] (5) Product performance: the prepared antimony-free polyester industrial yarn has a breaking strength of 8.7 cN / dtex, an elongation at break of 11.5%, and a dry heat shrinkage rate of 2.1% under the condition of 177°C x 10 min x 0.05 cN / dtex. The CV value of breaking strength is 2.0%, and the CV value of elongation at break is 5%.

[0043] Example 3 This example is basically the same as Example 1, except that some process parameters are adjusted.

[0044] (1) Preparation of polyester melt: the amount of catalyst added is 10 ppm based on the titanium metal content in the final polyester. The esterification reaction temperature is 240°C, and the melt polycondensation reaction temperature is 270°C, to obtain a base polyester melt with an intrinsic viscosity of 0.68 dL / g. In this step, 0.1% (within the range of 0.05-0.2%) of PTA mass of a heat stabilizer is also added, which is a compound of phosphite and phthalic anhydride. The phosphite here can play a stabilizing role, easily forming a relatively stable compound with the oxygen atom in unstable peroxide, interrupting the decomposition of peroxide into active free radicals, thereby preventing the development of chain reactions; the anhydride can react with polyester to increase the steric hindrance of polyester, reduce the reactivity of the terminal hydroxyl group, and improve the thermal stability.

[0045] (2) Liquid-phase viscosity increase: the liquid-phase viscosity increase reaction temperature is 270°C, and the melt residence time is 45 minutes, to obtain an industrial yarn grade high-viscosity polyester melt with an intrinsic viscosity of 1.05 dL / g.

[0046] (3) Spinning and post-processing: the spinning assembly temperature is set to 285°C. The process parameters of each process are as follows: First pair of rollers (primary draft): temperature 230°C, speed 500 m / min; Second pair of rollers (secondary draft): temperature 115°C, speed 650 m / min; Third pair of rollers (tertiary draft): temperature 180°C, speed 2000 m / min; Fourth pair of rollers (primary heat setting): temperature 240°C, speed 3200 m / min; Fifth pair of rollers (secondary heat setting): temperature 230°C, speed 3100 m / min; Sixth pair of rollers: speed 2900 m / min.

[0047] Among them, the length of the air-cooling-free cooling stage in the cooling and solidification stage is 0.8 m. The oiling stage adopts two-way oiling of the oil nozzle, the oiling rate of the oil agent is 1.1 ml / min, and the total oiling rate is 0.725%; the draw ratio of the spinning nozzle during spinning is 145; the draft ratio is 5.9; and the heat setting relaxation ratio is 0.99.

[0048] (4) Winding: finally wound into shape at a speed of 5200 m / min.

[0049] (5) Product performance: the prepared antimony-free polyester industrial yarn has a breaking strength of 8.1 cN / dtex, an elongation at break of 13.5%, and a dry heat shrinkage rate of 4.5% under the condition of 177°C x 10 min x 0.05 cN / dtex. The CV value of breaking strength is 2.2%, and the CV value of elongation at break is 5.5%.

[0050] Comparative Example 1 The main difference between this comparative example and Example 3 is that a conventional butyl titanate is used as the catalyst, and the addition amount is also 10 ppm in terms of titanium metal content in the final polyester, and the rest of the process parameters are kept as consistent as possible.

[0051] It is found that the melt viscosity increases slowly during the liquid-phase tackifying reaction, and the melt color is obviously yellow (the b value increases significantly). During the spinning process, the melt has poor thermal stability, and the viscosity fluctuates greatly, resulting in unstable spinning process, frequent broken ends, and inability to continuously and stably produce. The mechanical property test results of the small amount of sample finally obtained by force show that the breaking strength is less than 6.0 cN / dtex, and the CV values of strength and elongation are much higher than those of Examples 1-3, and the product quality is unqualified.

[0052] As can be seen from the comparison of the above examples and comparative examples, the specific double-metal coordination complex titanium catalyst of the application and the melt direct spinning process matched therewith can stably produce environmentally friendly antimony-free polyester industrial yarn with excellent performance and uniform quality at a lower energy consumption.

[0053] The part of the application not described in detail is the prior art, so the application does not describe it in detail. In particular, the above various performance index detection methods, such as intrinsic viscosity, carboxyl end group content, etc., are all conventional detection methods in the field, and different detection methods can be selected according to actual needs, so the application does not describe them in detail.

[0054] It can be understood that the term "one" should be understood as "at least one" or "one or more", that is, in one embodiment, the number of one element can be one, and in another embodiment, the number of the element can be multiple, and the term "one" cannot be understood as a limitation on the number.

[0055] Although professional terms are used more frequently in this document, the possibility of using other terms is not excluded. The use of these terms is only to more conveniently describe and explain the essence of the application; any interpretation of them as any kind of additional limitation is contrary to the spirit of the application.

[0056] The application is not limited to the above best embodiment, and anyone can derive other various forms of products under the inspiration of the application, but regardless of any changes in shape or structure, any technical solution with the same or similar technical solutions as the application falls within the protection scope of the application.

Claims

1. A melt direct spinning production process of antimony-free polyester industrial yarn, characterized by, Includes the following steps: a) Using terephthalic acid and ethylene glycol as reactants, esterification and melt polycondensation reactions were carried out in the presence of an antimony-free bimetallic coordination composite titanium catalyst to obtain a basic polyester melt. b) The base polyester melt is fed to a thickening reactor and subjected to a liquid-phase thickening reaction at a temperature of 262~275°C to obtain an industrial-grade high-viscosity polyester melt; c) The high-viscosity polyester melt is directly spun and post-processed to obtain antimony-free polyester industrial yarn. The antimony-free bimetallic coordination composite titanium catalyst is composed of a solid complex formed by coordination of a titanium central atom with an oxalate ligand, a 1,6-hexanediol ligand, and zinc acetate, and the molar ratio of titanium to zinc is 1:1.

2.

2. The melt direct spinning production process according to claim 1, characterized in that, The intrinsic viscosity of the basic polyester melt is 0.60~0.75 dL / g; the intrinsic viscosity of the industrial filament-grade high-viscosity melt is 0.92~1.25 dL / g.

3. The melt direct spinning production process according to claim 1 or 2, characterized in that, The amount of catalyst used, based on the titanium metal content, is 1 to 20 ppm of the total mass of ethylene glycol and terephthalic acid.

4. The melt direct spinning production process of claim 1, wherein, In the preparation of the basic polyester melt, a heat stabilizer is also added, the main components of which are phosphite compounds and benzoic anhydride compounds.

5. The melt direct spinning production process of claim 1, wherein, The post-processing steps include at least two stretching steps and two heat setting steps.

6. The melt direct spinning production process of claim 1, wherein, The post-processing steps employ a three-stage drawing and two-stage heat setting process, wherein the first-stage drawing temperature is 90~230℃ and the first-stage heat setting temperature is 160~250℃.

7. The melt spinning production process according to claim 1, characterized in that, The spinneret draw ratio during the spinning process is 90~200, and the total draw ratio is 5.0~8.

8.

8. An antimony-free polyester industrial yarn, characterized in that, It is a solid complex formed by the polymerization of terephthalic acid and ethylene glycol, and contains a bimetallic catalyst residue of titanium and zinc. The catalyst is a solid complex formed by the coordination of a titanium central atom with an oxalate ligand, a 1,6-hexanediol ligand and zinc acetate, wherein the molar ratio of titanium to zinc is 1:1.

2. Furthermore, the antimony-free polyester industrial yarn has a breaking strength of 7.4~9.0 cN / dtex, a breaking elongation of 11.5~15.8%, and a dry heat shrinkage rate of 2.1~7.5% under the conditions of 177℃×10min×0.05cN / dtex.

9. The antimony-free polyester industrial yarn according to claim 8, characterized in that, The industrial filament has a breaking strength CV value of no more than 2.5% and a breaking elongation CV value of no more than 6%.

10. The antimony-free polyester industrial yarn according to claim 8 or 9, characterized in that, The industrial filament has an elongation of 2.4 to 7.5% under a load of 4.0 cN / dtex.

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