Simulation of polyester melt spinning with axial quench for increasing productivity

Production of polyester filament involves melt spinning into partially oriented yarn (POY), followed by drawing to enhance the bulk and mechanical properties. The industrial demand of increasing productivity is generally met by increasing POY melt spinning speeds, which is limited by increasing polymer chain orientation (and reducing residual drawability) in the POY produced at higher spinning speeds. Modification of the quench geometry during melt spinning is claimed to allow reduction of air drag and polymer chain orientation, permitting an increase in productivity during melt spinning into POY. We present a simple way for modeling the quenching of molten filaments under the modified (axial) air flow. Numerical simulations of the melt spinning are developed to demonstrate the influence of the quench geometry modification as we compare the process with the conventional cross‐flow quench and the modified axial quench. We find that increasing quench air flow reduces the polymer chain orientation, in contrast to the well known effect in cross‐flow quench. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010     

170dtex/192 f直纺涤纶POY生产工艺探讨

采用特性粘数0.640-0.650 dL/g的PET熔体直接纺丝生产170 dtex/192f涤纶POY,使用熔体冷却器可有效控制输送过程中的熔体降解,选择纺丝温度290℃,侧吹风速度0.4 m/s,卷绕速度2 750 m/min, 适当控制其它条件,可得到涤纶POY的断裂强度2.29 cN/dtex,断裂伸长率128.2%,生产中毛丝量1.15%。     

多孔细旦涤纶POY工艺的探讨

介绍熔体直纺生产多孔细旦涤纶POY的工艺。熔体输送温度控制在288292℃,纺丝温度控制在289292℃,组件的初始压力控制在1216MPa。喷丝板下安装缓冷装置,增加风窗过滤网的密度,选择合适的风温、风速和相对湿度,缩短喷丝板至侧吹风距离等。     

Controlling micro‐ and nanofibrillar morphology of polymer blends in low‐speed melt spinning process. Part I. Profiles of PLA/PVA‐filament parameters along the spinline

The profiles of PLA/PVA filament parameters (e.g., temperature, velocity, tensile stress, and apparent elongational viscosity) along the spinline in the low‐speed melt spinning process under various spinning conditions were investigated. Owing to the combination of the filament velocity and filament temperature measurements using laser doppler velocimetry (LDV) and infrared thermography, respectively, the fiber formation zone was determined. The length of the fiber formation zone obtained from filament velocity profiles is always shorter than that obtained from the filament temperature profiles ( . Obviously, this unexpected phenomenon occurs for low spinning speeds due to the axial heat conduction effect of the filament along the spinline and the nonuniform radial temperature distribution through the cross‐sectional thick filament. Another remarkable finding is related to the Nusselt number which has been found as nearly constant along the spinline in the low‐speed melt spinning process. Thus, mathematical simulations of the filament temperature profiles will be simplified drastically. © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016 , 133, 44258.     

Comparison of tensile,thermal, and thermo‐mechanical properties of polyester filaments having different cross‐sectional shape

One of the most important morphological features of fibers is their cross‐sectional shape. Nowadays, the circular fiber cross‐section is the most common shape of melt‐spun man‐made fibers. Other shapes are beginning to emerge for a variety of reasons such as performance, comfort, pilling propensity, bulkiness, tactility, processing etc. The filaments' cross‐section can be easily varied by changing the spinneret hole shape. Synthetic fibers that are predominantly spun by the melt spinning method with spinnerets having the noncircular hole geometry are called profiled or noncircular fibers. Modifications of the fiber cross‐section allow designing surface properties in yarn and fabric. However, the effect of profiled fibers on yarn properties has not been well documented yet. In this article, the influence of different filament cross‐section geometry on fiber properties was studied. PET (polyethylene terephthalate) filament yarns having two different cross‐sectional shaped filaments, circular and cruciform, were manufactured by melt spinning. Differences in tensile properties of filament yarn and as well as of individual filament depending on the cross‐sectional type were studied and revealed. More over, thermal and thermomechanical properties of filament yarn of both the cross‐sections were studied and revealed by DSC and TMA method, respectively. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

Studies on melt spinning. II. Steady-state and transient solutions of fundamental equations compared with experimental results

In the part installment of the present paper, the authors formulated the dynamics of melt spinning by introducing a set of fundamental equations that consist of the equations of heat, force, and material balances. Some steady-state solutions were also given. Additional steady-state solutions corresponding to many different spinning conditions for polyester and polypropylene filament yarns consistently show good agreement with experimental results. These steady-state solutions that give filament cross-section A (x) and filament temperature t(x) as functions of position x are correlated with yarn qualities: yarn density and birefringence, crystallinity and molecular orientation, are correlated respectively with the speed of Polymer cooling at 100°C. and the maximum tensile stress (F/A)_w acting on the filament. A transient solution of the fundamental equations computed on an IBM 1401 machine shows that the filament cross-section A at the take-up roll forms a large transient peak after a stepwise increase in the speed v_y of cooling air. This agrees with experiments fairly well. The fundamental equations, therefore, clarify the dynamic relations between cooling air speed and yarn weight variations.     

五叶形涤纶POY生产工艺探讨

采用半消光聚对苯二甲酸乙二酯(PET)切片为原料,熔融纺丝生产出262 dtex/72 f五叶形涤纶POY,探讨了其主要的生产工艺。结果表明:选择五叶形喷丝孔喷丝板,纺丝温度为295℃;侧吹风温度22℃,速度0.30～0.45 m/min,相对湿度(70±5)%;含油率控制在0.4%,生产的五叶形涤纶POY截面形状清晰,异形度为61.4%,断裂强度2.32 cN/dtex,断裂伸长率119.4%,条干不匀率1.41%。     

干湿法PAN纤维截面成形条件的研究

对干湿法纺丝中PAN纤维的截面形状影响因素进行了研究。研究发现,凝固浴浓度和温度是影响纤维截面的主要因素,随着凝固浴浓度的增大和温度的升高,纤维截面逐渐由扁平形变为圆形,纤维截面的异形度逐渐减小;干湿法比湿法纺丝更有利于得到圆形截面的纤维;随着空气层高度的增大,纤维截面的异形度减小,但当空气层高度超过10mm时,纤维截面形状不再变化;在一定条件下,喷丝头拉伸比对纤维的截面形状有一定影响,后拉伸过程和干燥对纤维截而形状基本上没影响。     

Studies on high‐speed melt spinning of noncircular cross‐section fibers. III. Modeling of melt spinning process incorporating change in cross‐sectional shape

A numerical analysis program for high‐speed melt spinning of flat and hollow fibers was developed. Change in cross‐sectional shape along the spin line was incorporated adopting a formulation in which energy reduction caused by the reduction of surface area was assumed to be equal to the energy dissipation by viscous flow in the plane perpendicular to the fiber axis. In the case of flat fiber spinning, the development of temperature distribution in the cross section was considered. It was found that the empirical equations for air friction and cooling of the spin line of circular fibers can be applied for the flat fiber spin line if the geometrical mean of long‐axis and short‐axis lengths was adopted, instead of fiber diameter, as the characteristic length for Reynolds number and Nusselt number. Three features expected through the high‐speed spinning of noncircular cross‐section fibers could be reproduced: (1) although cooling of the flat fiber spin line was enhanced, calculated tension at the position of solidification was not affected much by the difference in cross‐sectional shape; (2) change in cross‐sectional shape proceeded steeply near the spinneret; and (3) temperature at the edge became significantly lower than that at the center in the cross section of flat fibers. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 80: 1589–1600, 2001     

Crystallization in polymer melt spinning

The crystallization behavior of poly(ethylene) terephthalate (PET) melt spun into fiber monofilaments was examined using a laboratory set-up. The wind-up speeds ranged from free fall under gravity to 1500 m/min. The major additional variables that were manipulated included the mass flow rate and the filament temperature profile. The structure of the as-spun fibers was probed using tensile tests, differential scanning calorimetry, optical birefringence, and x-ray diffraction. It was found that while the filaments that had been spun nonisothermally were essentially amorphous, those that had been made under isothermal conditions at temperatures ranging from 180°C to 240°C were oriented and crystalline. In addition, the rate of oriented crystallization was much greater than that under quiescent conditions at the same temperature. This is perhaps the first published study which shows that highly crystalline (up to 40% crystallinity) PET fibers can be obtained at low spinning speeds merely by altering the fiber temperature profile while the material is still above the polymer glass transition temperature.     

PP/PA6复合超细纤维的研制

以 PP和 PA6为原料 ,采用复合纺丝技术 ,制成单丝纤度 2～ 3 dtex的常规纤维 ,该纤维在后加工过程中可以剥离成单丝纤度小于 0 .5 dtex的复合超细纤维。介绍了复合纺丝工艺 ,讨论了对纤维物理性能指标产生较大影响的工艺参数 ,试验制得的复合超细纤维截面清晰 ,在常温常压下可染 ,织物服用舒适性良好。     

Correlation between entry pressure losses and elongation viscosity of polyethylene melts

The correlation between the entry pressure drop and elongation viscosity during entry converging flow of polymer melts was discussed in this article. The entry pressure drop during extrusion of a low density polyethylene (LDPE) melt and a linear low density polyethylene (LLDPE) melt was measured by means of a capillary rheometer under test conditions with temperature of 170 °C and shear rate varying from 10 to 300 s⁻¹. The results showed that the entry pressure drop increased nonlinearly with an increase of the shear stain rate, and the variation of entry pressure drop of the two melts was close to each other. The melt elongation viscosity of the two resins was estimated using Cogswell equation from the measured entry pressure drop data, and the predictions were compared with the melt extension viscosity measured by using a melt spinning technique published in literature. It was found that the melt extension viscosity from entry converging flow was slightly lower than that from melt spinning technique under the same temperature and extension strain rate.     

PET吸管冷却熔融纺丝动力学及计算机模拟

对ＰＥＴ吸管冷却纺丝侧吸风速度（Ｖｙ＊）及吸管内空气温度（Ｔ＊）沿纺程的分布进行了理论分析,并得到纺程上丝条的应力、速度、温度以及吸管内空气温度沿纺程分布的偏微分方程组,由此计算吸管冷却条件下的纺丝动力学量。由计算机模拟结果表明,Ｖｙ＊最大处刚好就是丝条形变速度最大处,也就是丝条开始凝固处或最需冷却处。吸管内丝条的环境温度是一个分布。在靠近喷丝板的区域,Ｔ＊较高,即相当于吸进热风。随着与喷丝板距离的加大,Ｔ＊迅速下降并趋近于室温,即相当于吸进冷风。     

Influence of melt spinning conditions on dye uptake of poly(ethylene terephthalate) fibres

The effects of quenching air temperature, quenching air speed and winding speed in the melt spinning process of poly(ethylene terephthalate) fibres with a titre of 147 dtex and 96 filaments on dye uptake were investigated. The ranges used for quenching air temperature, quenching air speed and winding speed were 17–27 °C, 0.3–0.7 m/s and 2600–3800 m/min, respectively. Specimens were dyed and their colour strengths (K/S values) were measured using a spectrophotometer. The results were statistically analysed.     

聚酯熔体直纺长丝环吹技术及应用

聚酯熔体纺丝采用环吹风装置,有压缩空间位置、节省吹风成本等诸多优点,而环吹风风量、风温等条件对纤维的结构与性能有非常重要的影响。通过对涤纶长丝环吹风工艺条件进行摸索,并与侧吹风工艺进行了比较,得到了环吹风风量、风压、无风区高度与纤维品质指标、品种之间的关系,验证了涤纶长丝环吹风技术及成本优势。     

Studies on melt spinning of nylon 6. I. Cooling and deformation behavior and orientation of nylon 6 threadline

The melt spinning of nylon 6 filament yarns was studied by measuring the filament tensions at the takeup roll, the filament temperatures θ(x), filament diameters d(x), and birefringence Δn(x) as functions of distance x from the spinneret, and by observing how the molecular orientation was affected by these differences in cooling and thinning. Results were as follows: The thinning of the filament line, d(x), is affected little by the spinning temperature or by the degree of polymerization of the yarns taken up; it however depends heavily on the takeup speed V_Tu and the rate Q of production. Trouton viscosity β(T) as a temperature function derived from these experiments on nylon 6 is expressed consistently by the equation β ? 0.34 exp (3250/T), where T is absolute temperature. Nylon 6 filaments exhibit higher Trouton viscosity values than polyester or polypropylene filaments under the same spinning temperature. Filament temperature θ(x) versus distance x agreed well with theoretical values. The speed of molecular orientation was highest in the temperature range from 120°C to 40°C (the latter being the glass transition temperature of nylon 6). Furthermore, the larger the time rate of polymer deformation and the longer the residence time of polymer in the above temperature range, the higher was the orientation of the filament yarns taken up.     

Studies on melt spinning process of hollow polyethylene terephthalate fibers

Dimensional change and profile development in the melt spinning process of polyethylene terephthalate hollow fibers were studied through the numerical simulations and experimental results. The simulation predicts the final dimensions and profiles development of the hollow fibers at various positions from the die. Experimental results show that the melt extruded from the spinneret coalesces initially to form a hollow inner core and the cross‐sectional shape holds for over the whole spinline with only variation in the hollow portion. Analysis of the effect of spinning parameters on hollow portion shows that the spinning temperature, mass throughput rate, and take‐up speed are the most critical variables in controlling the hollow portion followed by quench air velocity. The quench air temperature has relatively less effect than the other variables. As the mass throughput rate and quench air velocity increase and the take‐up speed and spinning temperature decrease, the hollow portion increases. To investigate the effect of die geometry, die having a different ratio of inner to outer diameter was used. The effect of change of process variables decreases as the die gap becomes narrow. POLYM. ENG. SCI. 46:609–616, 2006. © 2006 Society of Plastics Engineers     

杜邦公司涤纶短纤维生产技术特点分析

介绍了杜邦公司涤纶短纤维装置工艺技术特点及生产运行特点 ,重点叙述了其纺丝机结构紧凑、纺丝压力高、上环下侧的冷却吹风方式、卷绕丝束采用空气喂入、室温空气中干法拉伸等工艺特点 ,分析杜邦公司工艺对熔体质量及工艺控制的特殊要求 ,认为杜邦技术生产的涤纶短纤维成品丝质量好 ,装置能耗低     

On the dynamics of melt spinning

The dynamics of melt spinning was examined in the case of a Lethersich liquid taking also into account a phenomenologic way as well the transition zone between shear and elongational flow. The shape of the fluid jet was measured under many spinning conditions; the filament temperature and the fluid viscosity were then calculated. The experimental viscosity temperature relationship was compared with the W. L. F. equation, and the comparison makes it clear that the Newtonian model is not adequate whereas all the experimental evidence is in qualitative accordiance with the proposed model.     

三叶形截面碳化硅纤维纺丝工艺的研究

对三叶形截面碳化硅纤维的制备工艺进行了研究 ,分析了纺丝工艺中温度、压力、收丝速率对纤维异形度和当量直径的影响 ,发现纺丝温度是影响纤维异形度的主要因素 ,且较低的纺丝温度有利于制备异形度较大的纤维。实验表明 :制备异形截面碳化硅纤维的工艺条件为纺丝温度高出熔点 30～6 0℃ ,氮气压力 1.4～ 1.8MPa和适当的收丝速率的配合