MXPA99008518A - Load leveling yarns and webbings - Google Patents

Abstract

The present invention provides load leveling and impact energy absorption webbing comprising warp yarn. If the webbing is used in seat belts, the webbing provides load leveling behaviour from about 450 pounds (about 2,000 Newtons) to about 1,800 pounds (about 8,000 Newtons) in vehicle collision. The yarn comprises a multiplicity of fibers, all of said warp yarns having substantially the same force-displacement profile, are made from polymer having a glass transition temperature in the range from about -40°C to about +70°C, and are not made from polybutylene terephthalate homopolymer.

Description

THREADS AND TISSUES FOR LEVELING LOADS BACKGROUND OF THE INVENTION A safety belt system for typical vehicles is designed to restrict the displacement of an occupant with respect to the sitting position of the occupant inside the vehicle when the vehicle experiences a sudden and sudden deceleration. See commonly assigned US patent 3,322,163. A typical seatbelt system has three main parts: a retractable belt, the torso belt, and the lap belt and the operation of each belt can be characterized by its force displacement curve. The area under the force displacement curve is referred to as the energy absorbed by the safety restrictor. The current safety belts for vehicles are made of fully stretched polyethylene terephthalate (PET) fiber which is partially relaxed (2.7%) having a tenacity of at least 7.5 g / denier and 14% elongation at the fracture. However, there is a problem with the current PET safety belts. Studies in crashes indicate that after the initial impact of the vehicle occurs (eg, speed of approximately 35 miles / hour (56 km / h)), the occupant tends to move forward from their sitting position until the belt is hook to create restraining forces. As indicated in Figure 1, the relatively non-yielding belt made of PET fibers exerts a load of at least 2,000 pounds (907 Kg) (approximately 9,000 Newtons) against the occupant in a manner that causes the occupant chest injuries and in the ribs in the torso position of the belt and also injuries in the neck and back when the occupant bounces and hits against the back structure of the seat assembly. Regulations in the United States require that seat belts must support loads of up to 6,000 pounds (2,721 kg). When a car is hit at a speed of 35 miles / hour (56 km / hr), an energy impact to which a person of average car height is subjected is at least 500 joules in the torso belt. Although the current PET fiber can absorb the impact energy, damage to the vehicle occupant still occurs due to the undesirable force displacement curve. In 70 milliseconds, a passenger of average size will experience large forces of up to 2,000 pounds (907 kg) (cersa of 9,000 Newtons) as shown in Figure 1. U.S. Patent 3,530,904 discloses a woven fabric which is constructed by weaving two types of yarns that have relatively different physical properties that demonstrate energy absorption capacity. U.S. Patents 3,296,062; 3,464,459; 3,756,288; 3,823,748; 3,872,895; 3,926,227; 4,228,829; 5,376,440 and Japanese Patent 4-257336 further disclose fabrics which are constructed of multiple types of twisted yarns having different tenacity and elongations at the point of rupture. The fabric shows multiple fracture points and different absorbent characteristics. Those with skill in the technique have resonated the deficiencies by using at least two different types of threads as shown in the previous references. U.S. Patent 4,710,423 and Kokai Patent Publication 298209 published December 1, 1989 (Publication 298209) disclose that when at least two different types of yarn are used, energy absorption occurs in a staggered manner and therefore, the mesh does not absorb energy continuously and smoothly. Therefore, after one type of wire absorbs a portion of the impact energy, and before the other type of wire absorbs another portion of the impact energy, the human body is exposed to an unwanted stroke. In addition, these types of safety belts are not reusable. The patent 3,486,791 discloses devices energy absorbers such as a coiled device which separates a loose section of the belt from the taut section for body restraint by means of lashing which are under a predetermined restraining force to gradually feed the loose section so that the section Tense is lengthened allowing the restricted body to move with controlled speed. The reference also describes a device which anchors the belt to the vehicle by an anchor member fixed on the belt and integrated into an energy absorbing plastic. These types of mechanical devices are expensiveThey are not reusable, they provide poor energy absorption and are difficult to control. An improvement in the above devices is presented in U.S. Patent 5,547,143 which discloses an energy absorbing retractor comprising: a rotating reel, a safety belt mesh secured to the reel; and at least one mobile horn, which responds to charges generated during a collision situation, to deform a portion of the reel and thereby dissipate a certain amount of energy. U.S. Patent 4,710,423 and Publication 298209 disclose a mesh composed of PET yarns having a tenacity of at least 4 grams / denier and a terminal elongation of between 50% and 80%. Due to the inherent physical properties of the PET yarn, the examples show that, at 5% elongation, the energy has reached more than 700 Kg (1,500 pounds). Damage to the occupant by the seat belt still exists and therefore, the belt requires additional modification. Examples of these two patents also show that if the PET yarn is relaxed, the toughness drops to 2.3 grams / denier. Kokai Patent Publication 90717 published April 4, 1995 discloses an energy absorbing mesh based on polybutylene terephthalate hypopolymer (PBT). The tenacity of the fiber is greater than 5.8 grams / denier, the elongation at break is greater than 18. 0%, and the effort at 10% elongation is less than 3.0 grams / denier. However, this reference does not show the PBT fiber in its initial effort requirement which fixes the seatbelt to protect the occupant and the means to control the initial barrier of effort. It would be desirable to have an improved safety belt for absorbing energy which has a smoother operation than that of the known stitched mesh or with the use of two different known fibers, which is unusable not as the known fastening approach and which is also directed to the ability to control the initial stress barrier and the absorption of impact energy. Compendium of the Invention We have developed meshes which respond to the prior need in the art. The meshes, if used in safety belts, have a different behavior in load leveling between 450 pounds (204 Kg) (2,000 Newtons) and 1,800 pounds (816 Kg) (8,000 Kg) Newtons) during the collision of a vehicle. In order to meet these requirements, the mesh comprises twisted yarn and the twisted yarn has a force-displacement profile interfaced by: (a) when the yarn is subjected to an initial stress barrier of 0.2 grams / denier at or less than 1.4 grams / denier, the yarn is stretched to less than 3 percent of the initial module ranges of between 20 grams / denier to 150 grams / denier; (b) by submitting the yarn an initial stress barrier greater than and less than or equal to 1.8 grams / denier, the yarn is additionally stretched to less than 10 percent and the energy absorbed from 0 to the elongation at 1.8 grams / denier is when minus 0.0008 Joules / denier • meter; and (c) by subjecting the yarn to more than 1.8 grams / denier, the modulus is increased and the yarn is further stretched until the yarn breaks at a tension force of at least 5 grams / denier, where the yarn It comprises a multiplicity of fibers, all twisted yarns having the same force displacement profile, are made of polymers that have a glass transition temperature within the range between -40 ° C and + 70 ° C, and are not made of polybutylene terephthalate hypopolymer. The term "modulus" as used herein means the slope of the force displacement curve. Figure 2 illustrates the force displacement profile of one of the present yarns and meshes. The initial stress barrier is indicated as IBS in Figure 2. The present mesh is advantageous because it has a better impact absorption and a smoother operation than in the known stitched mesh approach or the known use of at least two fibers, it is reusable not as the known fixation approach and also has the ability to control the initial barrier of stress and the absorption of impact energy. Other advantages of the present invention will be apparent in the following detailed description, accompanying drawings and Associated claims. Brief Description of the Drawings Figure 1 shows the operation of a PET safety belt in the torso position. Figure 2 illustrates the force displacement profile of one of the present yarns and meshes. Figure 3 illustrates the force displacement profile of the wire of Example of the Invention 3. Figure 4 illustrates the force displacement profile of the wire of Example of the Invention 4. Figure 5 illustrates the force displacement profile of the wire of the Example of the Invention 5. Figure 6 illustrates the force displacement energy profile in a high speed Instron mesh test of 0.5 inches (1.27 cm) of the Example of the Invention 6. Figure 7 illustrates the force displacement energy profile in a high-speed Instron mesh test of 0.5 inches (1.27 cm) of the Example of the Invention 7. Figure 8 illustrates the operation of the mesh of the Example of Invention 8 in the torso position. Figure 9 illustrates the operation of the mesh of Example of Invention 9 in the torso position.

Detailed Description of Preferred Modes The present thread has the following force displacement profile. (a) When the yarn is subjected to an initial barrier effort of between 0.2 grams / denier to less than or equal to 1. 4 grams / denier, the yarn is stretched to less than 3 percent. The initial module comprises between 20 grams / denier at 150 grams / denier and the preferred initial module comprises between 50 grams / denier at 150 grams / denier. The high initial modulus is necessary to attach the safety belt and the initial barrier force height ensures that all occupant energy will be absorbed under the subsequent load leveling portion of the force displacement curve. (b) By subjecting the yarn to an initial barrier strength of less than or equal to 1.8 grams / denier, the yarn is further stretched to at least 10 percent. Preferably, the yarn is stretched between 3 percent to 20 percent and the energy absorbed between 0 to the elongation at 1.8 grams / denier is at least 0.0008 Joules / denier-meter. This portion of the displacement curve is the load leveling portion of the fiber which prevents the passenger from experiencing excessive loads. (c) By subjecting the yarn to more than 1.8 grams / denier, the modulus increases rapidly and the yarn is further stretched until the yarn breaks at a tensile strength of at least 5 grams / denier. In a safety belt assembly comprising the previous thread, the load on the passenger's torso can be reduced to 450 pounds (204 kg) (2,000 Newtons) even at a collision speed of 35 miles / hour (56 km / h hr). The reduced force minimizes or eliminates potential damage to the passenger. The yarn is made of a polymer having a glass transition temperature in the range between -40 ° C and + 70 ° C, preferably between -20 ° C and + 6 '° C, and more preferably between -10 ° C. ° C and + 40 ° C. The polymer can be a homopolymer, random copolymer, block copolymer, block copolymer or segmented block copolymer. Examples of preferred homopolymers include polyethylene terephthalate; polyisobutylene terephthalate; and long chain alkyl ether terephthalates and naphthalate polymers. Examples of random copolyesters include copolyester which, in addition to the ethylene terephthalate unit, contains components such as ethylene adipate, ethylene sebacate or other long-chain alkylene terephthalate units. This component is present in an amount greater than 10 percent. Examples of block copolymers include two-block copolymer structures, three-block copolymers and segmented block copolymer. The block copolymers comprise at least one crystalline aromatic polyester block and at least one soft amorphous aliphatic polyester block. The crystalline aromatic polyester includes homopolymers such as polyethylene terephthalate; polyethylene terephthalate; polybutylene terephthalate; polyisobutylene terephthalate; poly (2,2-dimethylpropyleneterephthalate); poly [bis- (hydroxymethyl) cyclohexenterephthalate]; other polyalkylene or polycycloalkylene naphthalates and the mixed polyesters, in addition to the ethylene terephthalate unit, contain somponents such as ethylene isophthalate; ethylene adipate; ethylene sebacate; 1,4-cyclohexylenedimethyleneterephthalate; or other long-chain alkylene terephthalate units. A mixture of aromatic polyesters can also be used. The most preferred aromatic polyesters include PET and PEN. Preferred lactones With regard to the amorphous aliphatic polyester block, it is made of lactone monomer. The e-caprolactone is the most preferred. In addition, you can also use propiolactone, butyrolactone, valerolactone, high cyclic lactones and two or more types of lactones. When PBT is used, the amorphous aliphatic polyester block is present in an amount greater than 10 percent. The disclosures of the co-pending patent application commonly assigned with serial number 08 / 788,895 of February 22, 1997 (entitled DIBLOCK POLYESTER COPOLYMER AND PROCESS FOR MAKING) and the request for a patent. continuing co-pending patent in part with serial number of March 18, 1997 (Titled (DIBLOCK POLYESTER COPOLYMER AND PROCESS FOR MAKING) (DOUBLE BLOCK POLYESTER COPOLYMER AND MANUFACTURING PROCESS) are incorporated herein by reference Examples of preferred block copolymers include those comprising (a) a first block of polyester in where the first block is made of aromatic polyester and (b) a second polyester block wherein the second block is made of lactone monomer.More preferably, the aromatic polyester has: (i) an intrinsic viscosity which is measured in a mixture 60/40 by weight of phenol and tetrachloroethane and is at least 0.6 deciliters / grams and (ii) a Newtonian melt viscosity of at least 7,000 poises at 280 ° C. Examples of preferred aromatic polyesters include polyethylene terephthalate (PET), polyethylene naphthalate (PEN), polybutylene terephthalate (PBT), polybutylene naphthalate, poly [bis (hydroxymethyl) cyclohexentrephthalate], poly [bis- (hydroxymethyl) cyclohexennaphthalate]; polymethylene terephthalate; polyisobutylene terephthalate; poly (2,2-dimethylpropyleneterephthalate); other polyalkylene or polycycloalkylene naphthalates and mixed polyesters which in addition to the ethylene terephthalate unit, contain components such as ethylene isophthalate, ethylene adipate, ethylene sebacate, 1,4-cyclohexylenedimethylene terephthalate, or other alkylene terephthalate units. A mixture of aromatic polyesters can also be used. Commercially available aromatic polyesters can be used. The most preferred aromatic polyesters include PET and PEN. The viscosities, measured in a mixture by weight of 60/40 of phenol and tetrachloroethane, of the preferred polyesters are 0.8 for PET and 0.6 for PEN. The most preferred IV for PET is 0.9 and for PEN it is 0.7. Preferred lactones include e-caprolactone, propiolactone, butyrolactone, valerolactone and high cyclic lactones. Two or more types of lactones can be used simultaneously. For use in load leveling belts, the two-block copolymer, PET-polycaprolactone can have a preferred concentration between 10 and 45 percent by weight, and more preferably between 20 and 30 percent by weight. In the two-block copolymer, the concentration of polycaprolactone can be varied to obtain the desired initial stress barrier and absorption of impasto with load leveling operation. The catalysts used in the polymerization of lactones can be used in the two-block copolymerization. The preferred catalysts are organometallic based on metals such as lithium, sodium, potassium, rubidium, cesium, magnesium, inorganic acid salts, organic acid salts and calcium alkoxides, barium, strontium, zinc, aluminum, titanium, cobalt, * germanium, tin, lead, antimony, arsenic, cerium, boron, cadmium and manganese; and its organometallic complexes of tin, aluminum and titanium. The most preferred catalysts are tin diacylate, tin tetraacrylate, dibutyltin oxide, dibutyltin dilaurate, tin octanoate, tin tetraacetate, aluminum triisobutyl, tetrabutyl titanium, germanium dioxide, antimony trioxide, porphyrin and phthalocyanine complexes of these metals . Two or more types of catalysts can be used in parallel. Useful catalysts are commercially available. Preferably, the amount of catalyst used is between 0.01 to 0.2 percent by weight based on the combined weight of the aromatic polyester and lactone monomer. The aromatic polyester is added to an extruder. The aromatic polyester can be melted and then added to the extruder or the aromatic polyester can be added to the extruder and then melted in the extruder. We have found that the preferred extruder is a twin screw extruder and therefore, the mixing and reaction of the polymer melt with material having a drastic viscosity difference becomes feasible. Useful double screw extruders are commercially available. The preferred twin-screw extruders are counter-rotating twin-screw extruders providing an inter-mixed mixing mode, in comparison with other extruders, provide good dispersive mixing, and a strict residence time distribution and an effective devolatilization. The profile of the screw is designed to allow the feeding of polyester shot, molten polyester shot, injection of lactone monomer, mixing, reaction, devolatilization and final pelletizing or centrifugation. The design of the extruder also allows the feeding of the initiating aromatic polyester melt. Efficient distributive and dispersed mixing must occur at the position where the lactone monomer is injected into the polyester melt. The initial extrusion temperature exceeds the melting point (measured by the Perkin-El Differential Calorimeter (DSC) of the maximum endotherm resulting from sensing a 2 mg sample at 20 ° C per minute) of the aromatic polyester used. The melting points of the preferred aromatic polyesters are 250 ° C for PET and 266 ° C for PEN. The initial extrusion zone temperature is at least 30 ° C above the melting point of the aromatic polyester. Therefore, the initial extrusion temperature for PET is at least 280 ° C while the preferred initial extrusion temperature for PEN is at least 296 ° C. To promote the formation of the two-block copolymer and to minimize the transesterification occurrence, the residence time and the extrusion temperature profile are important.

After the aromatic polyester has melted, the melt temperature is preferably lowered by 20 ° C and more preferably by 50 ° C due to mixing with the injected lactone monomer and the sachallizer. Preferably, the catalyst is added to the monomer e-caprolactone at room temperature and the e-caprolactone monomer / catalyst mixture is injected into the molten aromatic polyester. Therefore, the extrusion reactive temperature for PET is preferably 260 ° C and more preferably between 230 and 260 ° C while the extrusion temperature for PEN is preferably 276 ° C and more preferably between 246 and 276 ° C. The term "residence time" in the extruder as used herein means the volume of the extruder divided by the exit range. The aromatic polyester and the lactone are extruded at a residence time of less than 30 minutes and at a temperature sufficient to form the two-block copolymer. The preferred residence time is less than 15 minutes. The most preferred residence time is less than 10 minutes and the most preferred residence time is less than 5 minutes. This short residence time minimizes transesterification while ensuring complete polymerization which means grafting the monomer e-caprolastone to form the block in the final PET line and completing the consumption of the injected e-caprolactone monomer. Turbulators are used to increase the volume of the extruder without sacrificing the production range and to control the residence reaction time. To determine the residence distribution, we added colored pellets which served as a marker for the polyester pellets. The term "distribution time" means the range that starts from the appearance of color until the disappearance of color, as those skilled in the art know, increasing the distribution time increases the uniformity of the product. preferred distribution is less than 4 minutes The most preferred distribution time is 2 minutes and more preferred less than 1 minute The fiber formation can be obtained by spinning either directly from a twin screw extruder or separately from an extruder The two processes consist of extrusion, centrifuging, and stretching and relaxing phases.In the twin screw extruder, the combined reaction can be effected in the polymer melt with an appropriate screw profile and appropriate process conditions. In the single screw extruder, the polymer pellets can be fed and fused with an appropriate screw design and condition. process. A homogeneous melt is fed to a centrifuge container which contains a screen packing and a centrifuge. The extruded filaments pass through a hot screen, are cooled by ambient air and taken by a blade at a certain speed. The spun yarn is stretched to its maximum stretch range to obtain maximum strength. The relaxation stage shrinks the yarn and produces a yarn with the desired stress-strain curve. The relaxation of the fiber affects the maximum load which the passenger will experience in the collision of the vehicle. For example: using a PET / 25% polycaprolactone copolymer, the load experienced by the passenger can change from 1,500 (680 Kg) pounds to 900 (408 Kg) pounds when fully stretched fiber is relaxed by 5% at fifteen%. Depending on the intended use of the present mesh, additives such as UV stabilizers may be used in the fiber. The term "fiber multiplicity" as used herein means at least two ends of yarn and preferably, at least 342 ends for safety belts. The safety belts are normally twisted yarn fabrics of between 1,000 and 1,500 denier and a breaking strength of at least 5 grams / denier and a woven yarn with a denier of 500 to 900 and a breaking strength of at least 5 grams / denier. The fabric conditions are selected so that for the safety belts they maintain the stress / tension properties of the yarn and maintain the strength of the fabric. Our results indicate that the most desirable tissue pattern for energy absorption is 2X2 crossover tissue. The present mesh provides the desired load leveling characteristics in the absence of mooring device as presented in the United States Patent 3, 486,791; seams as presented in U.S. Patent 3,550,957; and a mechanical energy absorbing device such as the constant force retractor shown in commonly assigned U.S. Patent 5,547,143. The mesh and the present yarn provide desirable load leveling characteristics and are made of material other than the PBT homopolymer shown by Publication 90717. The present mesh provides the load leveling characteristics using twisted yarns having substantially the same displacement profile of force instead of the plurality of force displacement profiles shown by United States Patents 3,756,288; 3,823,748; 3,872,895; 4,288,829 and 5,376,440. The present mesh provides the desired load leveling characteristics and is made of polymer different from the PET homopolymer shown by U.S. Patent 4,710,423 and Publication 298209. The present mesh is useful for safety belts, parasaida harnesses and lines, shoulder harnesses, cargo handling, safety nets, trampolines, safety belts or harnesses for workers at high altitudes, military suppression tapes for stopping aircraft, towing lines for skiers and rope applications such as for mooring of yachts or moorings of oil towers. Test Procedures: Tenacity is measured on an Instron equipped with two lashings which hold the wire at meter lengths of 10 inches (25.4 cm.). The wire is pulled to the stress range of 10 inches / minute (25.4 cm per minute), the data is recorded by a load cell, and stress strain curves are obtained. Tenacity is the breaking force (in grams) divided by the denier of the fiber. The following examples are illustrative and not limiting.

Example 1 of the Invention: Dry PET pellets (IV = 0.9, MV = 15,000 poises at 280 ° C) were fed in a rotary twin screw extruder (diameter = 27 m, length = 1404 mm) at a ratio of 12 pounds / hour (5.44 Kg / hour). The length of an area was four times the diameter of the screw. The pellets started the casting and were advanced forward by means of a pumping element. After the PET was melted, the pre-mixed e-caprolactone and catalyst (tin octoate, 0.09% PET caprolactone) was injected by means of a piston pump into the extruder at a rate of 4 pounds / hour (1.8 Kg). /hour) . An advance mixer is located below the injection point. The injected liquid was quickly mixed with the PET melt by means of distributive and dispersive mixers. The mixture of PET and e-caprolactone was advanced to reaction zones and the reaction was completed with a residence time of 3.7 minutes. At the end of the polymerization, the melt was devolatilized by vacuum. The extrusion conditions are in Table I. The polymer melt (PET (75%) -polycaprolactone (25%)) was fed either to a spin pot which contained a spindle to form fibers, or extruded through a die with three perforations, cooled in water and cut into pellets. The two-block copolymer has a melting point of 231 ° C and an IV = 0.98 which shows that PET copolymerizes with e-caprolactone. Table I Zone Zone Zone Zone Zone Zone Zone 1 (° C) 2 (° C) 3 (° C) 4 (° C) 5 (° C 6 (° C) 7 (° C) 8 (° C) 1 292 290 255 255 245 240 240 235 2 292 290 260 250 250 245 245 240 Table I (cont. Zone Zone Zone Zone Zone 9 (° C) 10 (° C) 11 (° C) 12 (° c) 13 (° C) 1 235 235 235 235 235 2 240 240 252 242 240 Table I ( cont.) Speed Torque Temp. Pressure Vacuum Production Fusing screw (mbar) (lbs / hr) (RPM) (° C) fusion (psi) 150 48 256 60 -1000 16 150 55 264 90 -750 Table I (cont.) Time Res. Distribution Time (min.) Residence (min.) 3.7 1 12 Not determined The zone temperature had little deviation from the set points TABLE II Ex e-caprolac- e-capro-viscosity transesterifilactone (%) intrinsic lactone in the absence of copolymer copolymer react block block (%) double (dl / g) 1 25 0 0.98 5 2 15 0 0.94 6 Example 2 according to the invention: Dry PET pellets (IV = 0.9, MV = 15,000 poises at 280 ° C) were fed in a double counter rotating screw extruder (diameter = 27 mm, length = 1404 mm) at a rate of 4.26 pounds / hour, the pellets started to melt and were transported forward by means of pumping elements. of PET, e-caprolactone and catalyst (tin octoate, 0.03% by weight PET-caprolactone) were injected into the extruder through a piston pump at a rate of 0.75 pound / hour. The amount of e-caprolactone in PET was 15% by weight. The injected liquid was quickly mixed with a PET mixture by means of both distributive and dispersion combing mixers, grouped below the region of the injection port. e-caprolactone solubilized the PET fusion and reduced the melting temperature of PET at 225 ° C. The mixture of PET and e-caprolactone was transported forward in reaction zones. Turbulators in the reaction zone housed 61% of the volume of extrusion between turbulators and barrel. The total extrusion volume and the production rate (5.01 / hour) dictated the residence time of approximately 12 minutes. The melt in the polymerization process was found under the continuous agitation of geared turbulators and homogenization. At the end of the polymerization, the PET-polycaprolactone copolymer melt was fed to the devolatilization zone under vacuum (-750 mbar). The extrusion conditions are in Table I. The polymer (PET (85%) -polycaprolactone (15%)) was extruded through a die with three perforations, cooled with water and cut into pellets. The two-block copolymer had a melting point of 227 ° C and an IV = 0.94 which shows that the copolymerized PET is e-caprolactone. For each of the following Examples, the formation of PET / caprolactone fibers was effected centrifuged from a single screw extruder. The process consisted of extrusion, centrifugation, stretching, and relaxed stage. The pellets were fed to an extruder of 1 inch (2.54 cm.) MPM (L / D) = 30: 1), equipped with a screw with a long measuring zone to stabilize the melt pressure at the end of the extruder. An inverse temperature profile was selected for the purpose of melting the pellets completely in the first and second zones, decreasing the melt temperature, increasing the viscosity of the melt before pumping to a centrifuge container. The centrifuge container contained a sieve pack and a spindle with 25 syringe holes (0.024 inches X 0.072 inches) (0.60 cm X 0.68 cm). The extruded filaments passed through a heated sleeve and were cooled by ambient air in a 5 meter chimney. The thread was coated with a finish in the twisted line and taken to a godet at a certain speed to form a package. When the twisted yarn is stretched under different conditions at its maximum stretch ratio. The drawn yarn was relaxed at high temperature to produce the fiber with the desired strain stress curve. Example 3 of the Invention: The polymer shot (Example 1 of the invention) was dried and fed to the extruder with the temperature profile indicated in Table II at the screw speed of 46 RPM. Extrusion conditions gave barrel pressure and centrifuge container pressure of 1,200 psi and 500 psi, respectively. Since the twisted yarn had 25 filaments and 650 denier and was stretched under conditions a in Table IV and had a tenacity of 7.8 grams / denier. The fully drawn yarn was 200 denier with a melting temperature of 224 ° C. The fully drawn yarn was fed at a speed of 300 meters / minute to a roll at room temperature, moved to a second roll at 135 ° C with a second time of contaste and 15% entaged, cooled on a roll at room temperature, and sent to a furler. The relaxed thread had a 230 denier. The tension stress curve of the yarn (PET / 25% polycaprolactone) is presented in Figure 3. When the yarn was subjected to an initial stress barrier 0.6 grams / denier, the yarn was lengthened to less than 2% and the initial modulus It was 52 grams / denier. When the yarn was submitted between 0.6 grams / denier to 1.8 grams / denier, the yarn was lengthened between 2 and 20 percent and the energy absorbed between 0 and 20 percent was 0.00174 Joule / denier meter. By subjecting the yarn to more than 1.8 grams / denier, the modulus increased rapidly and the yarn lengthened between 20 and 31 percent until the yarn broke at a tension strength of 5.8 grams / denier. Example 4 of the Invention: The polymer shot (Example 2 of the invention, PET / 15% polycaprolactone) were dried and fed to the extruder with the temperature profile indicated in Table II and screw speed of 40 RPM. The extrusion conditions gave barrel and centrifuge container pressure of 800 psi and 400 psi, respectively. As the yarn stretched under conditions b in Table IV gave a fiber with toughness of 6.5 grams / denier. The fully drawn yarn was 259 denier with a melting point of 220 ° C. The previous fully drawn yarn was fed at a speed of 300 meters / minute to a first roll at room temperature, moved to the second roll at 150 ° C with a contact time of 1 second and shrunk 10%, cooled on a roll at a temperature environment and sent to rolled. See the tension stress curve of the wire (PET / 15% polycaprolactone) in Figure 4. Figure 4 shows the desired initial stress barrier. If the fiber is relaxed additionally to a tota-1 of 15%, the other properties of the fiber of the invention can be obtained.

Example 5 of the Invention: A two-block polymer (PET (70%) - polycaprolactone (30%)) was prepared in a manner similar to that indicated above. The polymer pellets (PET / 30% polycaprolactone) were dried and fed to the extruder with the temperature profile indicated in Table III at the screw speed of 42 RPM. The extrusion conditions gave a barrel pressure and centrifuge container pressure of 900 psi and 500 psi, respectively. As the twisted yarn stretched under conditions c in Table IV gave a fiber tenacity of 5.9 grams / denier. The fully drawn yarn was fed at a speed of 300 meters / minute to the first roll at room temperature, moved to the second roll at 150 ° C with 1 second of contact time and shrunk 10%, cooled on a roll at room temperature, and sent to a furler. The tension stress curve for the yarn (PET / 30% polycaprolactone) is shown in Figure 5. When the yarn is subjected to an initial stress barrier of 0.2 grams / denier, the yarn was stretched to less than 2 percent and the initial module was 20 grams / denier. When the yarn was subjected to between 0.2 grams / denier to less than or equal to 1.8 grams / denier, the yarn was lengthened between 2 and 14 percent and the energy absorbed between 0 to 14 percent was 0.00096 Joule / denier meter . By submitting the yarn to more than 1.8 grams / denier, the modulus increased rapidly and the yarn lengthened between 14 and 26 percent until the yarn broke at a tension strength of 5 grams / denier. Table III Extruder Example Zone 1 Zone Zone 3 Zone 4 Block ((°° CC)) ((°° CC)) (° C) (° C) (° C) 3 277 277 277 270 260 4 304 293 293 288 271 5 260 260 260 254 260 Table III (cont.) Centr. Performance Temp. of Manga Speed (° C) (g / min / hole) (° C) Shot (m / min) 260 2 185 280 271 1.6 200 180 260 1.6 200 180 Table IV Ex. Temp. 1st Roll turns Temp. Shoe Temp.2 ° roll (° C) (° C) (° C) to 40 7 140 140 b 40 7 150 90 c 30 7 160 160 Table IV (cont'd) Laps Stretch Ratio 10 8.4 10 7.7 10 7.4 Example 6 of the Invention: Based on the selection of the 2X2 screening fabric pattern, 91 ends of 1,400 denier of PET twist / 25% polycaprolactone of Example 3 of the invention were woven with 840 denier PET / 25% polycaprolactone Thread in a 1/2 inch strip (1.27 cm.) Wide. The sample was tested in a High speed Instron at a load ratio of 2,200 inches / minute (5,588 cm / minute) with a meter length of 3 inches (7.6 cm.). This corresponds to an automotive collision of 35 miles / hour (56 km / hour). Figure 6 showed that the mesh was elongated to 20% stress under the load of up to 250 pounds (113.4 Kg), and the energy was absorbed at 11.4 Joules. This corresponded to 663 Joules absorbed by a torso safety belt (50 inches long, 2 inches wide) (124 cm long, 5.08 cm wide) before the load on the passenger increased to 1,000 pounds ( 454 Kg). Example 7 of the Invention: A 12 inch long (30.48 cm) PET / 25% polycaprolactone (inch wide (1.27 cm)) mesh of Example 6 of the invention, mounted on a frame, was impregnated in a Red bath for 10 minutes The mesh with 30% absorption was pre-dried at 110 ° C for 3 minutes and dried at 120 ° C for an additional 3 minutes Finally, the tinted mesh was cooled to room temperature. Both senses were analyzed under an optical microscope and it was clearly shown that both directions of the fibers were uniformly and completely loosened.A minimum amount of shrinkage (<2%) of the original dimension was observed. The tinted mesh is shown in Figure 7 and compared to the unstained sample, the results indicated that the load leveling behavior was retained in the dyeing process.In the test sled, the safety belt size or Real (2 inches wide, 5.08 cm) was assembled into a cartridge with the functions of winding and braking the belt. Then, the assembly was installed inside a car and instrumented with load cells to measure the force on the safety belt. Comparative Example A: In order to establish a baseline for testing at 35 miles / hour (56 km / hr), a dummy (50th percentile hybrid) was secured with a 2-inch-wide safety belt (5.08 cm) .) PET. At the time of a simulated accident in the test on the sled, the load on the safety belt reached a maximum at 70 msec. After the collision The maximum force recorded was 9,200 N (2070 pounds) in the torso position shown in Figure 1. Example 8 of the Invention: 342 ends of 1,500 denier PET / 25% twisted yarn polycaprolactone of Example 3 of the invention were fabrics with PET / 25% polycaprolactone yarn of Example 3 of the invention in a safety belt with 2X2 screening pattern. The belt was tested with a mannequin (50th percentile hybrid). At a speed of 35 miles / hour (56 km / hour), the moment when the force reached the maximum was delayed to 100 msec. After the collision The maximum force measured was 5,700 N (1,280 pounds) in the torso position. As shown in Figure 8, the new mesh worked well and showed load leveling behavior at 5,700 Newtons which is a great contrast to the operation of Comparative Example A in Figure 1. Example 9 of the Invention: 342 ends of 1,500 denier PET / 25% twisted yarn polycaprolactone of Example 3 of the invention were woven with PET / 25% polycaprolactone yarn of Example 3 of the invention in a safety belt with 2X2 patterned pattern. The new mesh was cut to have the length of retractor and torso and sewn with a PET lap belt. A large mannequin (95th percentile hybrid) was secured for a sled test. At 35 miles / hour (56 km / hour), the moment when the maximum force in the torso position was delayed to 100 msec after the collision. The maximum force measured was 6,800 N (1,530 pounds) in the torso position. As shown in Figure 9, the new mesh worked well and showed a load leveling behavior at 6,800 Newtons which is a great contrast to the unwanted sputtering of Comparative Example A of Figure 1.

Claims (6)

1. CLAIMS. A yarn with a profile of force displacement such that: (a) When said yarn is subjected to an initial barrier effort between 0.2 grams / denier and less than or equal to 1.4 grams / denier, said yarn is stretched to less than 3 percent and the initial module comprises between about 20 grams / denier and about 150 grams / denier; (b) By subjecting said yarn to an effort greater than said initial barrier effort and less than or equal to 1.8 grams / denier, said yarn is lengthened to at least 10% and the energy absorbed from 0 to elongation to 1.8 grams. / denier is less than 0.0008 Joule / denier • meter; and (c) By subjecting said yarn to more than 1.8 grams / denier, the modulus increases rapidly and said yarn is further stretched until said yarn breaks at a tensile stress of at least 5 grams / denier, wherein said yarn it comprises a multiplicity of fibers, all said fibers have substantially the same force displacement profile; They are made of polymers that have a transition temperature within the range of -40 ° C to + 70 ° C, and are not made of polybutylene terephthalate homopolymer.
2. 2. The yarn of Claim 1 wherein said yarn of part (a) is stretched to less than about 2 percent.
3. 3. The yarn of Claim 1 wherein said yarn is made of homopolymers, random copolymers, two-block copolymers, three-block copolymers and segmented block copolymers. The yarn of Claim 1 wherein said yarn is made of said two-block copolymer, three block copolymer or segmented block copolymer comprising: (a) at least one polyester block wherein said first block is made of aromatic polyester; and (b) at least one second polyester block wherein said second block is hesho of lactone monomer. 5. The yarn of Claim 4 wherein the aromatic polyester resin is seleaded from the group consisting of polyethylene terephthalate, polyethylene naphthalate, polyakylene naphthalates, polycycloalkylene naphthalates; polybutylene terephthalate; and polytrimethylene terephthalate. 6. The thread of Claim 4 wherein said lactone polymer is made of monomer selected from the group consisting of e-caprolactone, propiolactone, butyrolactone, and valerolactone. The yarn of Claim 4 wherein the amount of said lactone polymer present is selected from 10 to 45 weight percent to obtain the desired initial barrier stress and impact energy absorption with load leveling operation. A mesh comprising twisted yarn, twisted yarn thread comprises the yarn of Claim 1. A security belt comprising the mesh of Claim 8.. A method to restrict an occupant of a vehicle in a vehicle solision that involves the steps of: using the mesh with impact energy absorption and load leveling which restricts said occupant of the vehicle with force of about 450 pounds ( 2,000 Newtons) at 1,800 pounds (8,000 Newtons) and comprises said mesh of Claim 8.