EP2177651B1 - Method for making PTT fibres with improved curling - Google Patents

Abstract

The PTT fiber is spun conventionally. In the new process it is stretched at up to 70[deg] C. Following stretching and before entry into the crimping chamber it receives no heat treatment. It is preferably held to a temperature no greater than 85[deg] C. When in the crimping chamber it is heated, reaching a temperature up to 100[deg] C. During crimping it is fixed whilst still in the crimping chamber. The temperature during stretching is up to 60[deg] C and after stretching up to 70[deg] C. The temperature before entry into the crimping chamber is up to 70[deg] C, preferably up to 60[deg] C and most especially between room temperature and 40[deg] C. In the crimping chamber the temperature is up to 95[deg] C, preferably being held in the range 85-90?C. It is then fixed by introducing superheated steam. Before entering the crimping chamber the fibers are preheated to a temperature at least 20[deg] C greater than that after stretching, but to no more than 85[deg] C; further alternative temperature conditions are cited. Steam is used for heating in the crimping chamber. The individual filament titer of the PTT fiber filaments is preferably about 2.4 dtex. 3.9-8.9 crimps/cm are produced, preferably 5.5 crimps/cm. The crimping ratio (delta l/L) is preferably at least 17%. Following fixing, the PTT fibers are cut and used as staple fibers. An independent claim IS INCLUDED FOR the PTT fibers so produced.

Description

The invention relates to a process for producing crimped polytrimethylene terephthalate ("PTT") fibers with improved crimping

Polyethylene terephthalate ("PET") and polybutylene terephthalate ("PBT"), commonly referred to as "polyalkylene terephthalates", are common commercial polyesters. Polyalkylene terephthalates have excellent physical and chemical properties, heat and light resistance, high melting points and high strength values. Consequently, they have always been widely used for technical and textile applications.

Polytrimethylene terephthalate ("PTT") has gained increasing commercial interest as a fibrous material because of the increased cost of raw materials, because recently in the low cost area, development has progressed to 1,3-propanediol (PDO), which is one of the monomer components of the polymer backbone of PTT. It has long been desired to have PTT in fiber form because of its dispersion dyeability at atmospheric pressure, its low flexural modulus, its elastic recovery, and its elastic resilience property.

While commercial availability of PTT fibers is relatively new, research has been ongoing for a long time. For example, British patent no. 1 254 826 Polyalkylene filaments, staple fibers and yarns, including PTT filaments and staple fibers. The main subject matter is carpet pile materials and fiber fillers. Described are the introduction of a filament bundle into a stuffer box texturing apparatus, the heat treatment of the crimped product in the form of a tow, being subjected to temperatures of about 150 ° C for a period of 18 minutes, and cutting the heat-set cable to staple lengths of 6 each Inch.

EP 1 016 741 describes the use of a phosphorus-containing additive and certain limiting constraints to achieve better whiteness, melt and spin stability in PTT polymers. The filaments and short fibers produced after spinning and stretching receive a heat treatment at 90-200 ° C.

JP 11-107081 describes the relaxation of an undrawn fiber of a PTT multifilament yarn at a temperature below 150 ° C, preferably at 110-150 ° C, for 0.2 to 0.8 seconds, preferably for 0.3 to 0.6 seconds, with a subsequent one False-twist texturing of the multifilament yarn.

JP 11-189938 describes the preparation of PTT short fibers (3-200 mm) and a wet heat treatment operation at 100-160 ° C for 0.01 to 90 minutes or a dry heat treatment operation at 100-300 ° C for 0.01 to 20 minutes. In working example 1, a PTT fiber is spun at 260 ° C. at a yarn spinning take-up speed of 1800 m / min. After stretching, the fiber is subjected to a heat treatment at 150 ° C in a liquid bath for 5 minutes to obtain a constant length. Then it is curled and cut. Working Example 2 illustrates the treatment of the drawn fibers with a dry heat treatment at 200 ° C for 3 minutes.

In U.S. Patent No. 3,584,103 describes a method for melt-spinning asymmetric birefringence PTT filaments. Spirally-crimped textile fibers of PTT material are prepared by melt-spinning filaments to have asymmetric birefringence throughout their diameter, the filaments, by stretching, being given a molecular orientation, the drawn filaments are heat-treated at 100-190 ° C while they are being drawn are kept at a constant length, and wherein the heat-treated filaments for 2-10 minutes in a relaxed state at more than 45 ° C, preferably at about 140 ° C, are heated.

EP 1 230 450 describes crimped PTT staple fibers with high tear resistance. The fibers are spun at a temperature of 245 to 285 ° C into filaments which are quenched and then preferably drawn according to a two-step process at a first temperature of 10 ° to 50 ° C and at a second temperature of 70 ° to 150 ° C. The patent teaches a compensation of the fibers by treatment with heat, preferably after stretching and before crimping, at temperatures of 85 to 115 ° C. The drawn filaments are crimped with a steam-assisted mechanical crimper to a crimp degree of 3 to 12 crimps per cm, relaxed at a temperature of 50 to 120 ° C, and then cut into staple fibers. The staple fibers are 0.8 to 6 denier (0.88 to 6.6 dtex) per filament. The crimp pick-up is preferably 10% and above. The tear strength is at least 3.5 grams per denier (3.1 cN / dtex).

EP 1 230 451 describes a process for producing a fibrous web, a fiber fabric or a fiber filling product from crimped PTT staple fibers. The fibers are spun at a temperature of 245 to 285 ° C into filaments which are quenched and then preferably drawn according to a two-step process at a first temperature of 10 ° to 50 ° C and at a second temperature of 70 ° to 150 ° C. The patent teaches a heat treatment of the fibers, preferably after drawing and before crimping, at temperatures of 85 to 115 ° C. The drawn filaments are crimped with a steam-assisted mechanical crimper to a crimp degree of 3 to 12 crimps per cm, relaxed at a temperature of 50 to 130 ° C, and then cut into staple fibers. The crimp pick-up is preferably 10% and above, the tear strength is at least 3.0 grams per denier (2.65 cN / dtex).

According to both documents EP 1 230 450 and EP 1 230 451 For example, the PTT fibers are subjected to elevated temperature both during drawing and before entering the crimping chamber. The stretching takes place according to both patents at a temperature of more than 70 ° C and before entering the crimping chamber, the fibers are heated to above 85 ° C.

There is a need for improvements in the PTT fiber process, particularly PTT staple fiber process, which recovers fibers having suitable processing properties in commercial operations utilizing carding and garnishing operations. The solution to these problems, which have been developed over the years for PET or PBT fibers, is often not transferable to PTT fibers, due to the particular properties underlying the chemistry of the PTT polymer.

In practice, it has been found, in particular, that in the case of fine fibers below about 3.6 dtex, it is not possible to achieve sufficiently high crimping, endurance and / or stability of the crimping, in particular for the textile further processing process, using these previously used methods.

The object of the present invention is therefore to provide a process for producing PTT fibers, preferably PTT staple fibers, with improved puckering.

This is achieved with the method according to the invention for producing PTT fibers.

The inventive method relates to the production of polytrimethylene terephthalate (PTT) fibers with improved crimping, characterized in that the stretching of the PTT fibers produced by conventional melt spinning processes at a temperature of up to 70 ° C and the PTT fibers after drawing and be subjected to no heat treatment before entering the crimping and in particular kept at a temperature below up to 85 ° C, then heated in the crimping chamber up to 100 ° C and fixed during the crimping.

Polytrimethylene terephthalate useful in the process of the invention and processes for its preparation have long been known. The preparation is carried out batchwise, continuously, etc. Further information on the production can be found for example in the U.S. Patents 5,015,789 and 6,277,289 . EP 0 998 440 . WO 98/57913 and in S. Schauhoff, "New Developments in the Production of Polytrimethylene Terephthalate, (New Developments in the Production of Polytrimethylene Terephthalate (PTT))", Man-Made Fiber Year Book (September 1996 ).

According to the invention, polytrimethylene terephthalates are used which are commercially available. Such polytrimethylene terephthalates are described, for example, by EI du Pont de Nemours and Company, Wilmington, Delaware (trade name "Sonora") and by Shell sold. Crystalline PTT is particularly suitable for use in the process according to the invention.

The polytrimethylene terephthalate useful in the present invention usually has an intrinsic viscosity (IV) of 0.60 deciliter / gram (dl / g) to 1.5 dl / g, preferably 0.70 dl / g to 1.4 dl / g, more preferably 0.80 dl / g to 1.2 dl / g and particularly preferably 0.90 dl / g to 1.1 dl / g (measured in 50:50 phenol / 1,1,2,2- Tetrachloroethane at 20 ° C).

Polytrimethylene terephthalate homopolymers and polytrimethylene terephthalate copolymers of polytrimethylene terephthalate and polyethylene terephthalate and / or polybutylene terephthalate are used in the practice of the present invention. Particularly advantageous are fibers which consist of at least 85 mol% of polytrimethylene terephthalate, preferably at least 90 mol%, particularly preferably at least 95 mol%.

The PTT fibers can be made by spinning the polymers into filaments and then processing them into fibers, stretching and crimping the fibers, and optionally applying a leveling agent, relaxing the fibers (optionally while the leveling agent hardened) and optionally an antistatic agent is applied to the fibers. In the case of staple fiber production, the fibers are then cut and packed in bales.

The preparation of the PTT fibers according to the invention is carried out using conventional methods and equipment, as are preferred in the art in the context of polyester fibers. For example, numerous methods of spinning in US 3,816,486 . U.S. 4,639,347 . GB 1 254 826 and JP 11-189938 described.

The spinning speed at PTT is preferably 600 meters per minute or more, and is typically 1200 meters per minute or less. The spinning temperature is typically 245 ° C to 285 ° C and preferably 250 ° C to 275 ° C. More preferably, melt spinning is carried out at about 260 ° C.

The spinneret is a conventional spinneret of the type used in conventional polyesters, with hole size, location and number depending on the desired fiber and spin line.

The quenching of the melt-spun PTT filaments in this manner may be carried out in a conventional manner using air or other fluids as described in the art (e.g., nitrogen). Cross-flow, radial, asymmetric or other cooling methods can be used.

After cooling, conventional spin finishes can be applied using standard methods.

The obtained PTT fiber filaments according to the invention, which are produced for clothing textiles (eg knitted fabric and woven textiles) and for nonwovens, typically have a single filament titer of 0.88 dtex to 6.6 dtex, preferably 1.7 dtex to 3.6 dtex and more preferably about 2.4 dtex. Larger value fibers may be used for non-textile applications, such as e.g. for fiber fillers, be useful.

The PTT fiber filaments thus produced are first deposited in cans for further processing. However, it is also possible to process them directly.

According to a preferred method, the melt-spun PTT fiber filaments are taken up on a spinning-cable cylinder, and then a plurality of spinning-cable cylinders are assembled and a large tow is produced from the fiber-filaments. Thereafter, the fiber tows can be drawn using conventional techniques, preferably at 10 to 110 m / min. The draw ratios are preferably from 1.25 to 4, and more preferably from 1.25 to 2.5. The stretching is cold, i. at a temperature of up to 70 ° C, preferably up to 60 ° C, more preferably up to 50 ° C, in particular up to 40 ° C, most preferably between room temperature (20 ° C) and 40 ° C.

After stretching it is important to ensure that the temperature of up to 85 ° C, preferably up to 70 ° C, more preferably up to 60 ° C, in particular up to 40 ° C, is not exceeded. Preferably, the temperature is between after stretching Room temperature (20 ° C) and up to 70 ° C, in particular between room temperature (20 ° C) and up to 60 ° C, more preferably room temperature (20 ° C) and 60 ° C, and most preferably between room temperature (20 ° C ) and 40 ° C.

In an alternative approach, the fiber tow may be heated at least 20 ° C after drawing and prior to entering the subsequent crimping chamber, but not more than the maximum temperature specified above of up to 85 ° C, preferably up to 70 ° C , more preferably up to 60 ° C, more preferably at a temperature in the range of 30 ° C to 60 ° C. Before and during drawing, one or more finishes may be applied using conventional techniques.

Another important feature is the crimp (crimp) K1, a measure of the filling of the fiber that is imparted to it through a mechanical crimping process. Crimp picking is an important feature that is important for both the processing of fibers and the characteristics of textile and fiber fill products, particularly staple fibers. In crimp picking, the springback property is measured on the fiber as transmitted through the mechanical crimping process. This has an effect on their handling characteristics as well as on the processing in the subsequent process steps.

wobei L_k die Länge der gekräuselten Stapelfaser im entspannten freiliegenden Zustand ist und L_v die Länge der gleichen, jedoch gestreckten Faser, d.h. die Faser liegt dann praktisch geradlinig ohne Kräuselung vor. Die Streckung erfolgt unter Anwendung der sogenannten Entkräuselungskraft. Diese wird in Vorversuchen mit Hilfe einer an das Kraft-Dehnungsdiagramm der jeweiligen Faser angelegten Tangente ermittelt.Circling in the context of the invention means the following ratio: $$\mathrm{K}\mathrm{1}\mathrm{=}\frac{\mathrm{lv}\mathrm{-}\mathrm{lk}}{\mathrm{lv}}$$

where L _{k is} the length of the crimped staple fiber in the relaxed, exposed state and L _{v is} the length of the same but stretched fiber, ie, the fiber is then practically straight without crimping. The stretching is carried out using the so-called Entkräuselungskraft. This is determined in preliminary tests by means of a tangent applied to the force-strain diagram of the respective fiber.

The fiber curl also influences the load behavior of the three-dimensional structure. The fiber crimp may be two-dimensional or three-dimensional, and is conventionally generated by mechanical means or may be inherently due structural differences or compositional differences in the fiber. Assuming a constant fiber weight, fiber size, geometry and surface properties, typically a low crimp fiber (ie, high amplitude, low crimp frequency) fiber will have a higher bulk content (ie, a high bulk, three dimensional, low density structure which will be slightly deformed under a given standard load due to a small amount of entanglement of the crimped fibers). In contrast, higher crimp fibers (low amplitude, high frequency) tend to produce three-dimensional structures with higher density and reduced volume retention. Such higher dimensional three-dimensional structures will not deform so easily when a standard load is applied due to a higher degree of fiber entanglement in the structure. In typical filled articles, the applied load (ie, the load for which the article was sized to hold it) is sufficiently high to cause relative displacement of the fibers in the structure. However, this load is not large enough to cause plastic deformation of the individual fibers.

The degree of crimp also affects the fiber's ability to recover after compression. Low crimp fibers do not recover as easily as high crimp fibers because the low crimp fibers lack the "springiness" provided by higher crimp. On the other hand, low crimp fibers are more easily loosened, due to the smaller amount of fiber entanglement. The user of filled articles typically wishes for both retention and volume retention. These two properties are strongly influenced by the crimp frequency, but in opposite and contradictory ways. In order to obtain a high volume content, use is made of a small crimp. In contrast, one uses a high crimping to get a strong hold. Other variables that can be modified include changing the mechanical properties of the fiber, adjusting the fiber diameter, and / or changing the fiber cross-section.

For the crimping of the fibers stretched as described above, conventional methods of mechanical crimping can be used with crimping machines known per se be applied. Preferred is a mechanical device for staple fiber crimping with steam assist, such as a stuffer box.

In order to obtain the invention improved crimping of fine PTT fibers, the drawn fibers prior to entering the crimping chamber and initially in the crimping chamber according to the invention to below up to 85 ° C, preferably below up to 70 ° C, more preferred below up to 60 ° C, especially below up to 40 ° C, most preferably between room temperature and 40 ° C held. The crimp itself takes place in the crimping chamber by heating, preferably with steam, to below up to 100 ° C, preferably below up to 95 ° C, more preferably about 85 ° to 90 ° C.

Using conventional methods, another finish can be applied in the crimper.

The PTT fiber obtained according to the invention preferably has a degree of crimping of at least 3 crimps (crimps) per cm, preferably 3 sheets per cm to 9.8 sheets per cm and more preferably 3.9 sheets per cm to 8.9 sheets per cm. In applications for the production of textile surfaces, values for the degree of crimping of about 5.5 sheets per cm are particularly preferred, for fiber fillings the degree of crimping is particularly preferably about 3.9 sheets per cm.

The crimp K1 according to the invention is preferably 15% or more, preferably 17% or more.

Preferably, after smoothing and before relaxation, a smoothing agent is applied and / or a commercial lubricant is applied for further processing (converting). Exemplary smoothing agents useful in the present invention are disclosed in U.S. Pat US 4,725,635 described.

Optionally, upon further relaxation of the filaments, further textile equipment, e.g. an antistatic finish can be applied.

Furthermore, if desired, the fibers can be made pillar free.

To make staple fibers, the textured fibers are taken up, followed by cutting and packaging in bales. The staple fibers of the present invention are preferably cut on a relaxation downstream mechanical cutter. Cable types are packed uncut in bales and fed to a separate cutting process (converting).

The staple fibers can be fixed before cutting. The main fixing takes place according to the invention in the crimping chamber by introducing superheated steam by means of conventional devices. Thereafter, before cutting at about 90 ° C to 120 ° C can be postfixed to control crimping and shrinkage. Methods of fixation and times used may vary and may be seconds using UV devices, or even longer using a furnace. Furnace temperatures are 80 ° to 130 ° C, preferably 100 ° C to 120 ° C, more preferably 110 ° C to 115 ° C.

The invention will be explained in more detail with reference to the following example:

Example:

Dry PTT granules (residual moisture <10 ppm, drying at a maximum of 130 ° C) with a viscosity of IV = 0.92 (20 ° C, 50:50 phenol / 1,1,2,2-tetrachloroethane) is in an extruder melted, spun through a spinneret with 400-1200 holes and withdrawn the yarn sheet obtained in the range of 900-1200 m / min and placed in sliver cans.

In order to achieve the desired target cable thickness of 90 ktex at a fiber unit titer of 2.4 dtex after drawing, the tow is presented at the sliver line. During further processing, in particular during and after drawing, the fiber cable is not exposed to temperatures of up to reaching the stuffer box crimping machine exposed to more than 30 ° C. In the crimping chamber itself, the material is fixed by introducing superheated steam in a crimped form. The choice of chamber and roller pressure depends on the desired crimping. In one variant, a supporting pre-tempering of the cable at 30-60 ° C takes place at the last roller septet in front of the crimping chamber.

After crimping, a post-fixation is carried out at 90-120 ° C. The choice of temperature depends on the desired residual shrinkage (measured as thermal shrinkage at 200 ° C.) of the fiber.

Claims (11)

1. A method for the production of polytrimethylene terephthalate (PTT) fibers having improved curling, characterized in that the drawing of the PTT fibers produced by means of customary melt-spinning methods is performed at a temperature of up to 70°C and that after the drawing and entering the crimping chamber, the fibers are held at a temperature of less than up to 85°C, then heated to up to 100°C in the crimping chamber and fixed during the crimping while still being in the crimping chamber.
2. The method according to claim 1, characterized in that the temperature is up to 60°C during the drawing and up to 70°C after the drawing.
3. The method according to claim 1 or 2, characterized in that before entering the crimping chamber the temperature is up to 70°C, preferably up to 60°C, particularly preferably between room temperature and 40°C, is then heated to up to 95°C, preferably 85 to 90°C, in the crimping chamber and thereafter set by introducing superheated steam.
4. The method according to claim 1 or 2, characterized in that before entering the crimping chamber, the fibers are preheated by at least 20°C compared with the temperature after the drawing, but to no more than up to 85°C.
5. The method according to any of the preceding claims, characterized in that before entering the crimping chamber, the fibers are preheated by at least 20°C compared with the temperature after the drawing, but to no more than up to 70°C, preferably to no more than up to 60°C, particularly preferably to between 30 and 60°C.
6. The method according to any of the preceding claims, characterized in that the heating in the crimping chamber is carried out with steam.
7. The method according to any of the preceding claims, characterized in that the PTT fiber filaments have a single filament titer of 0.88 dtex to 6.6 dtex, preferably 1.7 dtex to 3.6 dtex und particularly preferably about 2.4 dtex.
8. The method according to any of the preceding claims, characterized in that the degree of crimping is at least 3 crimps per cm, preferably within the range of 3 crimps per cm to 9.8 crimps per cm and particularly preferably within the range of 3.9 crimps per cm to 8.9 crimps per cm.
9. The method according to any of the preceding claims, characterized in that the degree of crimping is 5.5 crimps per cm.
10. The method according to any of the preceding claims, characterized in that the curling of the fibers is at lest 15%, preferably at least 17%.
11. The method according to any of the preceding claims, characterized in that the PTT fibers are cut and available in the form of staple fibers after the fixing.