JP2015501887A - Method for producing composite fiber containing polytrimethylene terephthalate - Google Patents

Abstract

Disclosed is a method for producing crimped conjugate fibers from two polytrimethylene terephthalate starting materials having different intrinsic viscosities. One starting material is characterized by an intrinsic viscosity of ≰0.7 dL / g. This relatively low intrinsic viscosity allows the use of low melting temperatures, reduces the occurrence of acrolein, and does not significantly degrade the properties or processability of the composite fiber.

Description

  The present invention relates to a melt spinning method for producing a composite fiber containing polytrimethylene terephthalate.

  Melt spun composite fibers are well known in the art. They are particularly useful in the technical field of forming bulky fibers and yarns. Bicomponent fibers are formed when two or more melt streams containing different polymers join at a spinneret to form a single fiber. A crimped fiber can be made from a composite fiber having a side-by-side or eccentric sheath / core type structure when the shrinkage properties of the two polymers that make up the two components are different. In order to shrink the fiber, the just-spun composite fiber is usually treated by heat treatment, so that the fiber has a helical shape due to the different shrinkage, thereby developing a crimped structure. The polymer constituting the two components can be chemically different, such as a composite fiber in which one component is polyethylene terephthalate and the other component is polytrimethylene terephthalate (PTT). Alternatively, the two components can be chemically the same but have different physical properties related to shrinkage.

  US Pat. No. 7,147,815 to Chang et al. Includes a first fiber component comprising a first composition comprising a first polytrimethylene terephthalate (PTT) and a second comprising a second PTT. A parallel type or eccentric sheath / core type composite fiber comprising a second fiber component comprising the composition of claim 2, wherein the intrinsic viscosity of the first and second PTT is 0.03 to 0.5 dL / g of each other Only different composite fibers are disclosed. Chang uses a PTT starting material characterized by an IV in the range of 0.86 to 1.01 dL / g. Chang uses melting temperatures up to 270 ° C. to reduce 0.86 dL / g IV of the starting material to 0.70 dL / g in a one-component melt flow to achieve high crimp shrinkage. Teaches.

In JP 2000-256918 by Yoshimura et al., Sheath / core type or side-by-side type composite fibers, one containing (A) at least 85 mol% polytrimethylene terephthalate and the other (B) 0. Contains at least 85 mol% polytrimethylene ₃₀ terephthalate copolymerized with 05-0.20 mol% trifunctional comonomer; or at least 85 mol with the other not copolymerized with (C) trifunctional comonomer A bicomponent fiber is disclosed that contains 0.1% polytrimethylene terephthalate and has an inherent viscosity of (C) that is 0.15 to 0.30 lower than that of (A).

  In one aspect, the present invention provides a composite fiber consisting essentially of a first polytrimethylene terephthalate fiber component and a second polytrimethylene terephthalate fiber component, wherein the composite fiber is> 2.2 Characterized by a molecular weight distribution indicating a sex index and an intrinsic viscosity in the range of 0.72 to 0.84, and the first fiber component and the second fiber component are used to develop crimp in the composite fiber. Provided are composite fibers that are arranged together in a suitable structure.

  The present invention is also characterized in that the first polytrimethylene terephthalate starting material is melted with an intrinsic viscosity of ≦ 0.7 dL / g, and the melting temperature is less than 250 ° C. Forming a first melt stream, wherein the first melt stream has an intrinsic viscosity less than or equal to 0.03 dL / g less than the intrinsic viscosity of the first starting material; Melting a second polytrimethylene terephthalate starting material characterized in that the viscosity is> 0.7 dL / g to form a second melt stream, wherein said first and second The difference in intrinsic viscosity of the melt flow is> 0.1 dL / g; and the first and second melt streams are fed to a spinneret where the first melt stream is fed to the second melt stream. Contacting with the spinneret; Extruding the molten fiber from: rapidly cooling the molten fiber to form a solid composite fiber characterized in that the first component and the second component are arranged in a structure suitable for the formation of crimps And a process for producing a composite fiber.

FIG. 1 is a schematic diagram showing the configuration of a composite fiber spinning device suitable for the method of the present invention. FIG. 2 is a schematic diagram illustrating an apparatus suitable for use in drawing, annealing, and winding of composite fibers produced by the method of the present invention. FIG. 3 is a schematic diagram illustrating a resin melting and feeding system suitable for use in the method of the present invention.

  When a range of values is given herein, it is intended to include both ends of the range unless otherwise indicated. The numerical values used herein have accuracy as numerical values with significant digits in accordance with the standard procedure for significant digits in chemistry outlined in ASTM E29-08 Section 6. For example, the numerical value 40 includes the range of 35.0 to 44.9, and the numerical value 40.0 includes the range of 39.50 to 40.49.

  As used herein, a “composite fiber” includes a pair of polymers bonded together along the length of the fiber so that the cross-section has a side-by-side, eccentric sheath-core, or useful crimp, for example. By other suitable cross-sections that can be developed is meant.

  Unless otherwise specified, “polytrimethylene terephthalate” (PTT) is meant to include homopolymers and copolymers containing at least 70 mol% of trimethylene terephthalate repeat units.

  PTT is prepared by polycondensation of dimethyl terephthalate or the corresponding diacid with 1,3-propanediol. Appropriate copolyesters can be prepared by adding a third reactant to the polycondensation reaction. The third component can be an additional diester or diacid, or an additional glycol. Comonomers are typically included in the copolyester in proportions ranging from about 0.5 to about 15 mole percent, and can be included in amounts up to 30 mole percent. Preferably, PTT is a homopolymer.

  A suitable PTT can contain small amounts of other comonomers, and such comonomers are usually selected so as not to have a significant adverse effect on properties. Such other comonomers include, for example, sodium 5-sulfoisophthalate in a proportion ranging from about 0.2 to 5 mole percent. In order to control the viscosity, trace amounts of trifunctional comonomers, such as trimellitic acid, can be added.

The molecular weight of PTT can be measured by any of various methods. One such method commonly used in the technical field of polyester polymers is the so-called intrinsic viscosity (IV) measurement. The IV of the polymer is determined by extrapolating the measured viscosity of the polymer solution to the zero concentration of the polymer. The intrinsic viscosity so determined is then Charles E. As described in the Carrahar edition, Polymer Chemistry, 5th edition, Marcel Dekker (2000), it can be related to the weight average molecular weight (M _w ) of the polymer by the Mark-Houwink equation. There is some discrepancy in the art with respect to the designation “IV” for the solution viscosity of the polymer. In this technical field, in some cases, “IV” is taken to indicate a so-called “inherent viscosity” that is related to but not equivalent to intrinsic viscosity. For the purposes of the present invention, the abbreviation “IV” always refers to intrinsic viscosity.

Another method for measuring molecular weight is by so-called size exclusion chromatography (SEC). A method of performing SEC suitable for the polymer of the present invention will be described later. SEC has the advantage of defining the overall molecular weight distribution, while intrinsic viscosity defines a point on the distribution. The ratio of the weight average molecular weight (M _w ) to the number average molecular weight (M _n ), known as the polydispersity index (PDI) of the polymer, is an indicator of the spread of the molecular weight distribution. Polycondensation reactions used for the preparation of PTT and the like are known to exhibit a PDI of about 2.0 ± 0.1.

  The inherent error in measuring molecular weight by either SEC or IV listed herein was about 3%.

  In one aspect, the invention provides a composite fiber comprising a first polytrimethylene terephthalate fiber component and a second polytrimethylene terephthalate fiber component, wherein the composite fiber has a polydispersity index of> 2.2. The molecular weight distribution shown and the intrinsic viscosity in the range of 0.72 to 0.84, and the first fiber component and the second fiber component are suitable for the development of crimp in the composite fiber To provide a composite fiber disposed on each other.

  The molecular weight of the composite fiber herein, as indicated by the distribution given by SEC, or the IV value, cannot be accurately predicted considering the molecular weight of the starting material. It is known in the art that the molecular weight of PTT is reduced by heat. The extent of the reduction will depend on factors such as the starting molecular weight, the melting temperature, the residence time at that temperature, the presence or absence of a thermal stabilizer. However, certain features are specific to composite fibers.

  The conjugate fibers herein are produced in a manner that does not differ so much that the two components differ in molecular weight, but the analysis by SEC can describe two different populations. In the experiments described below, a single molecular weight distribution curve was observed, but the width of the curve was greater than would be observed with a single condensation polymer. That is, PDI was greater than 2.2.

  Similarly, the IV of the starting material did not completely determine the IV of the spun composite fiber. Experiments have shown that starting materials characterized by IV ≦ 0.7 dL / g can be processed according to the methods described herein according to the method described herein because PTT with a relatively low molecular weight can be processed at very low temperatures. When processed in the temperature range of 250 ° C., the IV reduction was shown to be 4% or less.

  Thus, the bicomponent fibers described herein have one component with a very low IV that makes the overall bicomponent fiber IV very low, ie in the range of 0.72 to 0.84.

  In one embodiment of the conjugate fiber described in the present specification, the first fiber component and the second fiber component are arranged in a parallel structure in the conjugate fiber.

  In another embodiment, the first fiber component and the second fiber component are arranged in an eccentric sheath / core structure in the composite fiber.

  In one embodiment, the composite fiber is a staple fiber. In other embodiments, the staple fibers have a length of 0.5 to 6 inches.

  In one embodiment, the composite fiber is crimped.

  In one embodiment, the plurality of bicomponent fibers described herein are interwoven or entangled with one another in the form of a yarn.

  In one embodiment, the composite fibers are oriented. Fiber orientation can be determined by measuring birefringence in a manner well known in the art. The greater the birefringence of the fiber, the greater the degree of orientation.

  In another aspect, the invention features melting a first polytrimethylene terephthalate starting material characterized by an intrinsic viscosity of ≦ 0.7 dL / g and having a melting temperature of less than 250 ° C. Forming a first melt flow, wherein the first melt flow has an intrinsic viscosity of 0.03 dL / g or less less than the intrinsic viscosity of the first starting material. Melting the second polytrimethylene terephthalate starting material, characterized in that the intrinsic viscosity is> 0.7 dL / g, to form a second melt stream, wherein said first And the difference in intrinsic viscosity of the second melt stream is> 0.1 dL / g; and the first and second melt streams are fed to a spinneret where the first melt stream is fed to the second Contacting with a molten stream of A step of extruding a molten fiber from a spinneret; and rapidly cooling the molten fiber so that the first component and the second component are arranged in a structure suitable for the formation of crimps. The manufacturing method of a composite fiber including the process to form is provided.

  In one embodiment of the method described herein, the first component and the second component are arranged in a parallel structure with respect to each other.

  In other embodiments of the methods described herein, the first component and the second component are placed in a sheath / core structure with respect to each other.

  One embodiment of the method described herein is characterized in that the first starting material is an IV in the range of 0.60 to 0.68.

  In one embodiment, the second starting material is characterized by an IV of> 0.8 dL / g. In another embodiment, the second starting material is characterized by an IV of> 0.9 dL / g.

  In one embodiment of the method described herein, the first melt stream is at a temperature in the range of 240-245 ° C.

  In one embodiment of the method described herein, the difference in intrinsic viscosity of the first and second melt streams is> 0.2 dL / g.

  In the process of the present invention, the first starting material, which is usually commercially available as 1/8 ″ pellets, is characterized by IV ≦ 0.7. The lower limit of a suitable first starting material IV depends on the specific conditions of the fiber spinning process, such as fiber denier, the ratio of the two components, the temperature of the low IV component, and the like. The time when the lower IV component is broken or cracked during spinning, post-processing, or during normal use is when the lower limit of IV is exceeded.

  A suitable polytrimethylene terephthalate is available from E.I., Wilmington, Delaware under the trademark Sorona®. I. Available from du Pont de Nemours and Company.

  During spinning of the fiber, the PTT in the melt phase receives a large shearing force at the spinneret that forms the fiber, and then receives a greater shearing force when the fiber is drawn while being rapidly cooled. In order to maintain the mechanical integrity of the polymer during these high stress processes, the molecular weight of the polymer must be large enough. For these reasons, PTT fibers, including composite fibers, are generally formed from a PTT starting material characterized by an IV of 0.86 or higher, as taught in the aforementioned Chang et al. ing.

The melting process of the PTT can result in the generation of toxic by-products of acrolein (C ₃ H ₄ O- prop-2-defining) are known in the art. Experiments have been conducted to investigate the effect of treatment temperature on the formation rate of acrolein. The result was a 10-fold increase in the amount of acrolein produced from molten PTT when the temperature was increased from about 240 ° C. to about 280 ° C. with a residence time of 5 minutes.

  When the process of the present invention is carried out, it is possible that a composite fiber with good physical properties could be produced if one component of the starting material is characterized by IV ≦ 0.7 dL / g. all right. Furthermore, starting materials characterized by a relatively low IV of ≦ 0.7 dL / g can be melted and processed at a melting temperature in the range of 240 to 250 ° C., preferably 240 to 245 ° C. It was found that the composite fiber described in the specification can be spun smoothly and with good controllability. Starting materials with higher IV, as disclosed in the aforementioned Chang et al. Document, cannot be stably spun into fibers at temperatures in the range of 240-250 ° C.

  The low IV component in the above-mentioned Chang et al. Documented a very high IV polymer at 270 ° C., a temperature sufficiently high to cause a very low degree of degradation of the polymer to a very low IV at the same time. This is accomplished by exposure to a temperature associated with the occurrence of acrolein. The resulting PTT has much more carboxylate end groups than the low IV starting material of the present invention.

  Due to the low melting temperature characteristics of the methods described herein, a) low temperature, so that IV does not substantially change throughout the process and process controllability is improved; b) sufficient for low IV components Acrolein compared to methods that require one component to be heated to about 270 ° C. in order to obtain a low IV and to achieve other processability improvements that may result from its lower molecular weight The effect of significantly reducing the production of is obtained.

  FIG. 1 is a schematic diagram of an extruder, pump block and spinning block that constitute a suitable composite fiber spinning machine extrusion system. The spinning machine includes two polymer extrusion systems, designated W for the “West” system and E for the “East” system. The geographical names “east” and “west” have no meaning. Otherwise, it's just a convention, used to distinguish between two systems that are otherwise nearly identical. In FIG. 1, a Ktron KCLK720 weight loss feeder (1W / 1E) feeds polymer pellets to Werner and Pfleiderer's 28 mm co-rotating twin screw extruder (2W / 2E). The melt flow thus formed is fed to the pump block (4W / 4E). Each pump block is provided with an accompanying ballast pump (3W / 3E) and a spinning pump (5W / 5E). The ballast pump is used to discard part (or all) of the melt stream and the remainder of the melt stream is processed by the spinning pump. The ballast pump is a 1.32 cc / revolution Zenith gear pump. The speed of each spinning pump is adjusted to increase or decrease the throughput. By relatively adjusting the pump speed of the east and west extruders, the relative concentration of each polymer component in the spun fiber can be adjusted. The west spinning pump (5W) is a 3.30 cc / revolution Zenith gear pump. The east spinning pump (5E) is a 1.98 cc / revolution Zenith gear pump. Two melt streams are fed from each spinning pump and merge in a single spinning block 9 having a recess fitted with an annular composite filtration pack 10 and a spinneret 11 prevention pack. In the examples described below, the filtration pack 10 consisted of one 50 mesh filtration screen, three 200 mesh filtration screens, and about 20 millimeter 10/25 glass chips. The composite post-join spinneret 11 having a diameter of 3.12 inches had 34 pairs of holes (not shown) arranged in two circular shapes. Each hole had a diameter of 0.63 mm and a length of 4.24 mm. In the examples, a thermocouple (7W / 7E) provided at the outlet of the extruder was used to measure the temperature of the melt flow. The temperature of the melt flow in the pump block (6W / 6E) and the spinning block can be optimized by controlling the pack pressure.

  FIG. 2 shows a cross flow melt spinning apparatus suitable for use in the method of the present invention. The quench gas 21 passes from the plenum 24, through the hinge baffle 28, through the screen 25, into the zone 22 below the spinneret face 11, and across the molten fiber 26 exiting the spinneret. A gas flow is created. The baffle 28 is hinged at the top so that its position can be adjusted to change the flow of quench gas across the zone 22. The spinneret surface 11 is recessed by a distance A at the top of the zone 22 so that the quenching gas does not contact the fiber just after spinning until after a lag time where the fiber could be heated by the side of the recess. In the examples described later, the rapidly cooled fibers were moved from the spinning floor to the lower floor roller array (see FIG. 3) via the baffle 27. The fiber that became solid was finished by bringing it into contact with the finishing roller 210.

  In FIG. 3, the fiber 26 is guided from the finishing roller to the driven roller 31, the idle roller 32, and then the heating roller 33. The temperature of the roller 33 can range from about 50 ° C to about 70 ° C. Thereafter, the fiber moves to the heat drawing roller 34. The temperature of the roller 34 can range from about 50 ° C to about 170 ° C, preferably from about 100 ° C to about 120 ° C. The fiber then moves from roller 34 to heating roller 35, optionally around an unheated roller 36 (adjusting the yarn tension for good winding) and moving to a winding device 37. The draw ratio (34 speed divided by 33 speed) ranges from about 1.4 to about 4.5, preferably from about 3.0 to about 4.0. There is no need to apply a large tension between the roller pair 33 or between the roller pair 34 (beyond the tension required to keep the fiber on the roller). Heat treatment can also be performed with a heating chamber such as one or more other heating rollers, a steam jet, or a “hot chest”. The heat treatment can be performed at a substantially constant length, for example, with the roller 35 of FIG. 3 that heats the fiber to a temperature in the range of about 110 ° C. to about 170 ° C., preferably about 120 ° C. to about 160 ° C. .

  The heat treatment time depends on the yarn denier. What is important is that the fibers can reach substantially the same temperature as the roller. If the heat treatment temperature is too low, crimping may be reduced and shrinkage may be increased when tension is applied at high temperatures. If the heat treatment temperature is too high, the fiber will break frequently and the process will be difficult to perform. In order to keep the fiber tension substantially constant at this point in the process, thereby avoiding a reduction in fiber crimp, it is preferred that the heat roller speed and the draw roller speed be substantially the same. .

  Alternatively, the supply roller can be unheated, and the stretching can be performed by a heated stretching roller that also serves as a stretching jet and a heat treatment of the fiber.

  The combined jet can optionally be positioned between the stretch / heat treatment roller and the winding device.

  Finally, the fiber is wound up. The winding speed when producing the product of the present invention is typically about 2500 meters per minute (mpm). Usable winding speeds are about 2,000 mpm to 6,000 mpm.

Test Method Measurement of Crimp Shrinkage Each fiber was formed into a total denier (5550 dtex) wrinkle of about 5000 ± 5 using a wrinkle frame and a tension of about 0.1 gpd (0.09 dN / tex). Then, in order to accommodate in the inside of the oven used for heat setting, the basket was folded in half and the length was halved. The central part of the folded folds was hooked and conditioned for at least 16 hours at 70 ± 1 ° F. (21 ± 1 ° C.) and relative humidity 65 ± 2%. Thereafter, the central part of the folded bag was suspended substantially vertically on the hook of the rack, and a weight of 1.5 mg / den (1.35 mg / dtex) was suspended at the lower end through the two rings of the folded basket. . The loaded cocoon is then heated in an oven at 250 ° F. (121 ° C.) for 5 minutes, after which the rack and cocoon are removed and cooled for 5 minutes, with a 1.5 mg / den weight between subsequent tests. Conditioning was performed for at least 2 hours at 70 ± 1 ° F. (21 ± 1 ° C.) and a relative humidity of 65 ± 2%, with the cocoons on the heel. The heel length was measured to within 1 mm and recorded as “Ca”. A 1000 gram weight was then hung at the lower end of the heel to reach equilibrium, and the heel length was measured to within 1 mm and recorded as “La”. The crimped shrinkage “CCa” value (%) was calculated according to the following formula.
CCa = 100 × (La−Ca) / La

Measurement of IV The intrinsic viscosity (IV) was determined by the Goodyear R-103b method.

Measurement of Molecular Weight Distribution Molecular weight distribution was measured using size exclusion chromatography (SEC), a technique well known in the art, used in measuring the molecular weight distribution of polyesters. The polydispersity index (PDI) was determined as PDI = M _w / M _n (where M _w is the weight average molecular weight and M _n is the number average molecular weight, which is a value determined by SEC).

Fabrication of Fiber Three grades of Sorona® polytrimethylene terephthalate resin pellets were obtained from E.I., Wilmington, Delaware. I. Obtained from DuPont de Nemous and Company. One grade is characterized by an IV of 1.02 dL / g, the second is characterized by an IV of 0.96 dL / g, and the third is characterized by an IV of 0.66 dL / g. It was something to do. In preparation for melt spinning, each grade was dried in a vacuum oven under nitrogen and under a 25 inch mercury column at a temperature of 120 ° C. for 15 hours. The resin pellets thus dried were immediately transferred to a nitrogen-purged supply hopper of the spinning machine of FIG.

  The melt spun composite filament was quenched with air. Referring to FIG. 1, quenching air 1 was supplied at room temperature, and was made to collide with the extruded linear yarn 6 at 0.12 m / sec as measured 0.61 meters below the spinneret.

Comparative Example A
Sorona (registered trademark) pellets having an IV of 1.02 were dried and fed to both the extruders. The nine zones of both extruders were set to the same heating profile as 180/240/250/250/255/255/250/255/255 ° C. The temperature of the melt flow measured at the exit of the extruder was 256 ° C.

  The speed of both the east and west spinning pumps (5W5E in FIG. 1) was set to 14.4 g / min. The speed of both ballast pumps was set at 6.6 g / min. Referring to FIG. 3, a linear yarn was wound six times around an unheated supply roller / separation roller 31/32 operating at a linear velocity of 796 m / min. Thereafter, a linear yarn was wound around the drawing roller 33 at around 65 ° C., which is also operating at a linear speed of 796 m / min, five times. Thereafter, the linear yarn was wound nine times around the annealing roller 34 operating at 150 ° C. and a linear velocity of 2550 m / min. Thereafter, the linear yarn was wound 9 times around the unheated tension relaxation roller 35 operating at a linear velocity of 2550 m / min. Thereafter, the linear yarn was wound 6 times around the additional set of unheated tension relief rollers 36 operating at a linear velocity of 2550 m / min. The yarn was collected on a paper tube at a linear speed of 2480 m / min with a Barmag SW6 2s 600 winder (Barmag AG, Germany) 37.

  The results for the fibers produced in Comparative Example A (CE A) using the method described in the fiber production section are shown in Table 1. Table 1 shows the properties of fibers made from two identical melt streams. Table 1 also shows the properties of a fiber (CE A-1) operating at the same speed as described for one component of a bicomponent fiber and formed from a single melt stream. The term “n / a” means “not applicable”.

  The IV and molecular weight distribution were determined for the as-spun fibers. Further, crimp contraction and CCa were measured. In this comparative example, a very low CCa value was obtained.

Table 1

Examples 1-3
Similar to CE A, Sorona® resin pellets with an IV of 1.02 were again fed to the West extruder. However, the East Extruder was supplied with Sorona® resin pellets with an IV of 0.66. The temperature profile of the nine heating zones of the east extruder was set to 140/200/235/245/245/245/245/245/245 ° C. The temperature of the melt flow measured at the exit of the extruder was 245 ° C.

  The supply roller and the stretching roller were rotated at 850 m / min to produce a product having a stretching ratio of 3.0. The supply roller and the drawing roller were rotated at 796 m / min to collect products having a drawing ratio of 3.2. The supply roller and the stretching roller were rotated at 750 m / min to collect products having a stretching ratio of 3.4. All other roller speeds and temperatures were maintained the same as in Comparative Example 1.

  The results for the fibers produced in Examples 1-3 are shown in Table 2.

  Table 2 also shows the properties of the fibers (Ex 1-1 and Ex 1-2) operating at the same speed as described for each component of the bicomponent fiber and formed separately from each melt stream. Both extrudates so produced were dissolved in trichloroethane and analyzed by SEC.

Table 2

Example 4
Example 3 except that the starting material of the west extruder has an IV of 0.96 and the profile of the extruder is 180/255/255/255/255/255/255/255 ° C. The following conditions were used. The temperature of the line carrying the melt stream from the west extruder was 256 ° C.

  Table 3 also shows the properties of the fibers (Ex 4-1 and Ex 4-2) operating at the same speed as described for each component of the bicomponent fiber and formed separately from each melt stream. Both extrudates so produced were dissolved in trichloroethane and analyzed by SEC.

  The results of the fibers produced in Example 4 are shown in Table 3.

Examples 5-7
As shown in Table 4, Example 1 was repeated except that the pump flow rate of the spinning pump was changed. The results for the fibers produced in Examples 5-7 are shown in Table 4.

Table 4

Claims (12)

  Melting a first polytrimethylene terephthalate starting material characterized by an intrinsic viscosity of ≦ 0.7 dL / g to form a first melt stream characterized by a melting temperature of less than 250 ° C. And wherein the first melt stream has an intrinsic viscosity that is 0.03 dL / g or less less than the intrinsic viscosity of the first starting material; the intrinsic viscosity is> 0.7 dL Melting the second polytrimethylene terephthalate starting material to form a second melt stream, characterized in that the intrinsic viscosity of the first and second melt streams is A difference of> 0.1 dL / g; supplying the first and second melt streams to a spinneret where the first melt stream is contacted with the second melt stream; Molten fiber from the spinneret A step of rapidly cooling the molten fiber to form a solid composite fiber characterized in that the first component and the second component are arranged in a structure suitable for the formation of crimps. Including methods.   The method of claim 1, wherein the first component and the second component are arranged with each other in a side-by-side structure in the conjugate fiber.   The method according to claim 1, wherein the first component and the second component are arranged with respect to each other in an eccentric sheath-core structure in the conjugate fiber.   The method of claim 1, wherein the first starting material is an IV in the range of 0.60 to 0.68.   The method of claim 1, wherein the second starting material has an IV of> 0.8 dL / g.   6. The method of claim 5, wherein the second starting material is> 0.9 dL / g IV.   The method of claim 1 wherein the first melt stream is at a temperature in the range of 240-245 ° C.   The method of claim 1 wherein the difference in intrinsic viscosity of the first and second melt streams is> 0.2 dL / g.   Wherein the first starting material has an intrinsic viscosity in the range of 0.60 to 0.68, and the second starting material has an intrinsic viscosity of> 0.8 dL / g, The method of claim 1 wherein the difference in intrinsic viscosity between the first and second melt streams is> 0.2 dL / g.   The method of claim 9 wherein the first melt stream is at a temperature in the range of 240-245 ° C.   11. The method of claim 10, wherein the second starting material has an intrinsic viscosity of> 0.9 dL / g.   The method of claim 1, further comprising exposing the composite fiber to an elevated temperature, thereby developing crimps.

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