PET切片干燥过程中的固相缩聚

本文通过测定干燥后PET切片的特性粘度及所纺成纤维的强伸度,研究了直接酯化法生产的PET切片在连续式充填干燥器中干燥过程中所发生的固相缩聚。研究结果表明干燥温度和干燥时间对固化反应的速度和程度都有很大影响,固相缩聚后的干切片粘度和分子量有所提高,并将导致熔体温度和POY强度提高。干燥温度和时间的波动会导致干切片特性粘度的不均,并进一步导致纤维的不匀率提高。     

Study of polypropylene/poly(ethylene terephthalate) bicomponent melt‐blowing process: The fiber temperature and elongational viscosity profiles of the spinline

Although there are significant differences between high‐speed melt spinning and melt blowing (MB), they are similar in many important components. This study, motivated by the need to better understand the bicomponent MB process, used the basic theories of high‐speed melt spinning to estimate the fiber temperature and elongation viscosity profiles of the polypropylene/poly(ethylene terephthalate) (PP/PET) bicomponent MB process. During the MB process, the filament temperature decreased dramatically within the first 2 in. from the MB die. The fiber temperature‐decay profiles of PP, PET monocomponent, and PP/PET bicomponent filaments followed similar trends. PP filaments attenuated faster than PET filaments and the bicomponent filaments attenuated at a medium rate between that of PP and PET. Accordingly, the elongational viscosity increased significantly in the first 2 in. from the die. PET filaments exhibited higher elongational viscosity than that of 100% PP filaments. The elongational viscosity profile of 75%PP/25%PET was between that of PP and PET monocomponent filaments. These data provided important information on understanding the MB process and filament attenuation. It also suggested that the filament elongational viscosity profile is the key factor in production of finer bicomponent MB fibers. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 89: 1145–1150, 2003     

Structure development of poly(L‐lactic acid) fibers processed at various spinning conditions

Poly(L ‐lactic acid) (PLA) filaments were spun by melt‐spinning at 500 and 1850 mm^?1, and further drawn and heat‐set to modify the morphology of these PLA filaments. PLA yarns were characterized by wide‐angle X‐ray diffraction (WAXD) and sonic method. WAXD reveals that PLA yarns spun at 500 mm^?1 are almost amorphous while the PLA filaments spun at 1850 mm^?1 have about 6% crystallinity. This is different from PET filaments spun at the same speed that have almost no crystallinity. Both drawn‐ and heat‐set PLA filaments showed much higher crystallinity (60%) than do as‐spun fibers produced at 500 and 1850 mm^?1 speed, which is also higher than the usual heat‐set PET yarns. It appears that crystalline orientation rapidly reaches a value in the order of 0.95 at 1850 mm^?1 and that drawn‐ and heat‐set yarns have almost the same crystalline orientation values. Molecular orientation is relatively low for as‐spun PLA yarn, and molecular orientation increased to ～0.5 after drawing or heat–setting or both. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 101: 1210–1216, 2006     

固相缩聚反应温度与时间对PET结晶的影响

研究了聚对苯二甲酸乙二醇酯(PET)切片在固相缩聚反应中特性粘数和结晶度随反应条件的变化及其热行为。结果表明:固相缩聚PET特性粘数随反应温度和反应时间不断增大,反应温度为215～ 225℃时较佳,随反应的进行新结晶产生,一定时间后结晶度增加缓慢并趋于平衡;DSC分析表明固相缩聚反应后的PET存在一个特征熔融峰(253℃左右)和固相缩聚峰,随着反应温度和反应时间的增加,固相缩聚峰不断向特征熔融峰靠拢,一定反应温度和反应时间后融合为单峰,之后低温峰跨过特征熔融峰向高温移动。     

Melt spinning and drawing of 2‐methyl‐1,3‐propanediol‐substituted poly(ethylene terephthalate)

The structure and properties of fibers prepared from copolymers of poly(ethylene terephthalate) (PET) in which 2‐methyl‐1,3‐propanediol (MPDiol® Glycol is a registered trademark of Lyondell Chemical Company) at 4, 7, 10, and 25 mol% was substituted for ethylene glycol were studied and compared with those of PET homopolymer. Filaments were melt spun over a range of spinning conditions, and some filaments that were spun at relatively low spinning speeds were subjected to hot drawing. The filaments were characterized by measurements of birefringence, differential scanning calorimetry (DSC) crystallinity, melting point, glass transition temperature, wide‐angle X‐ray diffraction patterns, boiling water shrinkage, tenacity, and elongation to break. Filaments containing 25 mol% MPDiol did not crystallize in the spinline at any spinning speed investigated, whereas the other resins did crystallize in the spinline at high spinning speeds. However, compared with PET homopolymer, increasing substitution of MPDiol reduced the rate at which the crystallinity of the melt spun filaments increased with spinning speed and reduced the ultimate crystallinity that could be achieved by high‐speed spinning. The rate of development of molecular orientation, as measured by birefringence, also decreased somewhat with increasing MPDiol content. Shrinkage in boiling water decreased at high spinning speeds as the amount of crystallinity increased; however, the shrinkage decreased more slowly with increase in spinning speed as MPDiol content increased. Tenacity also decreased slightly at any given spinning speed as MPDiol content increased, but there was no significant effect on elongation to break. The addition of MPDiol in amounts up to 7 mol% increased the maximum take‐up velocity that could be achieved at a given mass throughput. This result indicates that the use of higher spinning speeds could potentially increase the productivity of melt spun yarns. Copolymer filaments spun at low speeds were readily drawn to produce highly oriented fibers with slightly less birefringence, crystallinity, and tenacity than similarly processed PET homopolymer. Preliminary dyeing experiments showed that the incorporation of MPDiol improved the dyeability of the filaments. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 88: 2598–2606, 2003     

Spinning fibers from poly(ethylene terephthalate) bottle‐grade waste

Poly(ethylene terephthalate) bottle‐grade (BG) waste was converted into spinnable chips and spun on a laboratory‐scale melt‐spinning apparatus into filaments. Virgin fiber‐grade (FG) polyester chips were blended with BG waste during melt spinning so that the influence of blending on the fiber properties could be studied. Subsequently, the scaling‐up of the process was carried out in a polyester recycling plant so that staple fibers could be obtained. In this part of the study, the spinning of blends of BG waste and FG waste was carried out. The BG waste was found to be superior feed stock for melt processing. Fibers with unique properties were obtained from the BG waste. Staple fibers obtained by the blending of FG and BG waste showed properties different from those of fibers spun from BG waste alone. This study also showed that using blends of BG and FG waste could improve the melt processing and staple‐fiber properties. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 90: 3536–3545, 2003     

Effect of solid‐state shearing of poly(ethylene terephtalate) on isothermal crystallization and fiber structure formation

Solid‐state shearing was applied on recycled poly(ethylene terephtalate) (PET) using twin‐screw extruder. The shearing effect on isothermal crystallization was investigated by DSC. Structure formation in melt spinning was also studied by characterizing the spun fibers. It was found that the solid‐state shearing imposes a great influence on its crystallization behavior. Crystallization peak temperature of the sheared PET (199°C) was much higher than that of the PET without shearing (188°C). Overall isothermal crystallization rate was found to be accelerated to more than 50 times by the shearing. The shearing effect remained even after fiber spinning (melt processing). Differences in crystallization behavior, fiber structure formation, and tensile properties of the fibers were found. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 104: 787–791, 2007     

Computer Simulation of Polyester High‐Speed Thermal Channel Spinning

A mathematical model to describe the thermal channel spinning (TCS) process in PET high‐speed melt‐spinning has been developed. This model, which is based on the spinning process kinematics, includes the effects of acceleration, gravity, and surfacial air friction. It incorporates the constitutive equation of PET polymer, the heat transfer related to the transverse air blowing and, in particular, to a convection and radiation combining procedure in the thermal channel, while taking into account the nonisothermal crystallization kinetics related to temperature and molecular orientation as well as the elongational viscosity of PET polymer connected with temperature, intrinsic viscosity and crystallinity. The developments of crystallinity, molecular orientation and morphological features of high‐speed‐spun PET fiber in the TCS process are investigated at take‐up speeds ranging from 3 600–4 400 m/min and thermal channel temperatures ranging from 160–200°C. The simulated results of this model are compared with the measured crystallinity, diameter, and birefringence of the spun yarn. The “necking point” in the TCS spinline can be predicted by this model.     

Studies on fiber formation of thermotropic copolyesters

Thermotropic copolyesters PET/60 PHB and PET/80 PHB fibers are melt spun at different extrusion temperatures and at different draw-down ratios. The flow behavior of PET/60 PHB is studied at different temperatures and shear rates. The melt of (PET/60 PHB) at temperatures above 265°C exhibit low viscosity and low activation energy of flow. The modulus and strength for both PET/60 PHB and PET/80 PHB fibers increase with the increase in extrusion temperature and draw-down ratio in the ranges studied. High birefringence, indicating the presence of mesophase is observed between 265 and 300°C on a hot stage polarizing microscope. X-ray diffraction patterns show that the molecular orientation increased with increasing draw-down ratio. Scanning electron microscopy of these fibers shows a well-developed highly oriented fibrillar structure. Superior mechanical performance of fibers spun at around 275°C are attributed to the presence of nematic mesophase in the polymer melt. © 1993 John Wiley & Sons, Inc.     

PBT／PET并列型复合纺丝的研究

就ＰＢＴ、ＰＥＴ两种聚合物材料的流变性能和ＰＢＴ／ＰＥＴ并列型复合纤维的熔纺温度之间的关系进行了讨论，指出ＰＢＴ宜低温熔融、高温纺丝，ＰＥＴ则相反．同时．还考察了复合比对初生丝热性能、ＤＴ丝卷缩性能的影响，表明随着ＰＢＴ组份量的增加，Ｔｇ转变和冷结晶放热峰移向较低温位．且后者峰面积相应缩小；ＰＢＴ熔融吸热峰面积增大．ＰＥＴ的则相应缩小；ＤＴ丝的卷缩率增大．卷缩稳定性则变差．此外．还就纺丝速度对初生丝热性能和结晶度的影响进行了探讨．发现随着纺丝速度的提高，初生丝ＤＳＣ扫描曲线上的冷结晶移向较低温位，而两组份的熔融吸热峰似无变化；初生丝结晶应随纺速的提高而略有增加．但增幅不大．     

Modification of PET in high‐speed melt spinning by blending with PEN

Blends of polyethylene terephthalate (PET) and polyethylene naphthalate (PEN) were melt spun using a high‐speed winding process in a single‐screw extruder combined with a spinning setup. The filaments had a single T_m and T_g, which indicates excellent compatibility in both the amorphous and crystalline phases. Birefringence and wide angle X‐ray measurements indicated that compounding PEN into PET suppresses stress‐induced orientation and decreases the stressinduced crystallization in the filaments. Adding PEN to PET relaxes the formation of skin‐core structures for as‐spun fibers and reduces the occurrence of broken filaments. Although the addition of PEN reduced crystallinity, it did not affect the tenacity and the shrinkage of the compounded filaments. The elongation of the fibers could be reduced by 30% to 40%, eliminating the need for a further drawing. These results are attributed to PEN's rigid backbone. Adding PEN to PET improves PETs spinnability during high‐speed spinning.     

熔体直纺工艺中粘度波动对长丝质量的影响

讨论了熔体粘度波动时熔体的可纺性、POY的物性指标及后加工性能、DTY的质量指标及其染色等情况。结果表明;熔体粘度偏低时,前纺飘丝断头增多,后纺伸头困难,POY和DTY的强度降低、伸长度增大,DTY有较多的点状僵丝,袜带吸色较深且有较多的色斑点;熔体粘度偏高时,熔体泵前压力偏低,后加工张力高,纸筒管易于破裂。POY和DTY纤度偏小,强度增大,伸长度减小,各种不匀增大,袜带吸色较浅且较为均匀。初步确定熔体粘度的波动范围应控制在1.615—1.650.     

Crystal‐crystal transformations in isotactic polybutene‐1 oriented filaments and in thick molded rods

This paper reports two related studies of the Form II → Form I crystal‐crystal transformation in isotactic polybutene‐1. First, it was found that in melt spun filaments, the rate of transformation is higher in filaments possessing higher levels of crystalline orientation. Second, we consider the occurrence of this phase transformation in thick quenched cylindrical rods. It was found that the phase transformation occurs more rapidly in the core than at the surface of the part. It is hypothesized that the mechanism of the higher transformation rate in the core is due to the development of residual quench stresses associated with densification at solidification. These stress levels have been calculated and our results compared with earlier studies.     

Aspects of the yield behavior in poly(ethylene terephthalate) fibers

The yield behavior during cold drawing of commercially spun poly(ethylene terephthalate) (PET) filament yarn was investigated. Microscopic examination revealed the presence of inherent flaws within the spun filaments; these act as points for localized stress concentration. These inhomogeneities appear to be either internal cracks or crazes developed during the fiber melt spinning process. During elongation, stress magnification at these flaws results in shear band formation, indicating the onset of inhomogeneous yielding. At the yield bend in the load-elongation curve a circumferential crack propagates within these shear band regions. This yield crack develops into the classical neck geometry which further localizes additional plastic deformation within the sample at the neck.     

采用远红外加热技术干燥聚酯切片

介绍了采用远红外线加热干燥含水切片的试验过程,分析了此项技术的可行性。通过试验测试了不同的加热温度、料板距离和干燥时间对干燥后切片含水率的影响。试验结果表明,采用远红外线加热干燥后的切片含水率是可以达到螺杆挤压机纺制聚酯短纤维和熔喷非织造布的工艺条件和技术要求的,从而扩大了远红外线的应用范围。     

Reactive blending of poly(ethylene terephthalate) with a liquid crystalline copolyester and polyhydroxyether

Poly(ethylene terephthalate) modified with a dianhydride (PET–anhydride) was melt‐blended with a liquid crystalline copolyester (Vectra A) in the presence of a small amount of a liquid crystalline polyhydroxyether. The mechanical properties of a blend consisting of PET–anhydride/Vectra A/polyhydroxyether were drastically improved compared to blends without polyhydroxyether or without anhydride. Melt‐spun fibers of PET–anhydride/Vectra A/polyhydroxyether in a 80/20/0.75 weight ratio displayed a much higher tensile modulus (17 GPa) and tensile strength (214 MPa) than did a 80/20 PET–anhydride/Vectra A blend (4 GPa and 60 MPa, respectively). A similar increase in modulus and strength was found for a 90/10/0.75 relative to a 90/10 blend. The tensile moduli of the blends can well be described by the Tsai–Halpin equation. A better fibril formation was observed, which was attributed to an improved viscosity ratio. Reactions between the various functional groups during melt processing were indicated by viscosity measurements. The polyhydroxyether may act as a reactive compatibilizer which improves the interfacial adhesion, chemically and/or physically. WAXD recordings of both blends showed a crystalline and highly oriented Vectra phase. The PET phase was unoriented and amorphous in a PET/Vectra blend and semicrystalline and weakly oriented in a PET/Vectra/polyhydroxyether blend. Postdrawing of the various blend fibers to λ = 4 increased the modulus by about 40% and the tensile strength by more than 100%, mainly through orientation of the PET phase. © 1999 John Wiley & Sons, Inc. J Appl Polym Sci 71: 1107–1123, 1999     

Properties of high‐speed spun high molecular weight poly(ethylene terephthalate) filaments

High‐speed spinning of high molecular weight poly(ethylene terephthalate) (PET) having an intrinsic viscosity of 0.98 dL/g was performed at the take‐up velocity range of 2.5–5.5 km/min. The structure of the as‐spun filaments was analyzed by density, birefringence, WAXS, DSC, boiling water shrinkage, and tensile properties. Stress‐induced crystallization takes place above 3 km/min, which is confirmed by the steep increase in density, the growth of the crystal size, melting point increase, and the decrease in boiling water shrinkage. The plot of crystallinity versus birefringence shows that crystallinity increases drastically after birefringence reaches the value of about 0.075. A comparison with the data of other researchers will clearly present the effects of molecular weight on the properties of PET filaments spun at high speed, for example, the take‐up velocity range of the steep increase in density for high molecular weight PET is lower than that for low molecular weight PET by about 1 km/min. © 1999 John Wiley & Sons, Inc. J Appl Polym Sci 71: 1283–1291, 1999     

CDP/PET共纺低弹丝的研制

介绍了以ＣＤＰ，ＰＥＴ切片为原料，采用ＰＯＹ－ＤＴＹ路线研制双组分共纺低弹丝的工艺特点和关键技术。通过对ＣＤＰ，ＰＥＴ切片进行热分析和流变性能分析，认为：ＣＤＰ，ＰＥＴ组分应采用不同的干燥工艺，需选择不同特性粘数的切片来保证二者熔体粘度的匹配，纺丝组件的设计要考虑纺丝工艺的特殊性等。并与单一组分ＰＥＴ的高速纺丝和变形工艺进行了比较，从理论上解释了两者的差异。     

高强高模锦/涤皮芯复合长丝工艺的探索

用高粘度聚酯切片和高分子量聚酰胺切片在自制的(?)20mm双螺杆复合纺丝机上纺制了锦/涤皮芯复合轮胎帘线.探讨了纺丝温度、拉伸温度与倍数,并与高强涤纶及高强锦纶的纺丝工艺进行了比较.     

Effect of molecular weight on high-speed melt spinning of nylon 6

An extensive experimental study of the structure and properties developed in as-spun nylon 6 filaments is reported. Five polymers representing different molecular weights in the range 25,000–73,000 g/mol (viscosity average) were studied. These polymers were melt spun over a range of spinning speeds using an air drag type of drawdown device. Maximum take-up velocities achieved were in the neighborhood of 4000 m/min. The structure and properties of the as-spun filaments were characterized using density, DSC, WAXS, SAXS, birefringence, and tensile tests. The structural characteristics and properties of the filaments are strongly dependent on molecular weight. Generally, higher molecular weight leads to higher modulus and filament tenacity and lower elongation to break in the as-spun filaments. The structural changes with molecular weight are rather complicated; the complications are explained in terms of changes of crystallization rate and attainable crystallinity.