双向拉伸聚酯薄膜铸膜工艺研究

提出双向拉伸聚酯薄膜铸膜过程的模头拉伸比计算方法;研究了模头拉伸比与模唇开度和铸膜厚片的关系,模唇开度的确定程序,铸膜厚片颈缩的影响因素,薄膜边膜厚度梯度要求及控制措施;探讨了熔体膜厚度方向在冷鼓上的冷却固化温度分布、静电附片方式以及制约铸膜速度的因素。     

BOPET薄膜生产线中铸膜系统的研究

主要讨论了BOPET(双向拉伸聚对苯二甲酸乙二醇酯)生产线中的铸膜系统，分别论述了模唇开度与静电电极位置对生产的影响，确立了模唇开度与静电电极位置的调整方法。     

双向拉伸PET薄膜生产线技术(续三) (一)双向拉伸PET薄膜生产工艺及设备

(一)双向拉伸PET薄膜生产工艺及设备2.4铸片系统铸片是将挤出系统输送来的均匀稳定的熔体通过模头流延在转动的急冷辊上,使之形成无定型的厚片,供下道工序拉伸用。铸片系统由模头、急冷辊     

双向拉伸PET薄膜生产线技术(续三) (一)双向拉伸PET薄膜生产工艺及设备

(一)双向拉伸PET薄膜生产工艺及设备2.4铸片系统铸片是将挤出系统输送来的均匀稳定的熔体通过模头流延在转动的急冷辊上,使之形成无定型的厚片,供下道工序拉伸用。铸片系统由模头、急冷辊     

铸片系统对BOPP薄膜的影响研究

介绍了双向拉伸聚丙烯（BOPP）薄膜铸片系统的设备结构和工作原理，详细地论述了铸片系统中模头、气刀、压边嘴、激冷辊以及水槽对BOPP薄膜的生产过程和性能的影响，并提出了一些注意事项和解决方法，对生产实践有相当的参考价值。     

改进模头区域加湿方法,提高薄膜生产效率

针对聚酯薄膜生产的关键工序铸片单元易出现花斑、唇印、拉丝等不良问题,且清洗模唇间隔时间短生产效率低下的问题,通过改善模头区域的湿度问题,改善清洗模头的工装,稳定模头区域的工作环境,改进清洗过滤器碟片的检查方法,有效解决铸片的品质问题,同时极大地提高了聚酯薄膜生产效率。     

含氟薄膜流延法制备方法

正1种含氟薄膜流延法制备方法 ,其中含氟树脂(FEP、PFA、ETFE)经螺杆挤出得到熔融含氟聚合物,再经流延模头挤出得到熔膜,熔膜经流延辊和冷却辊冷却定型,再经在线厚度检测,并自动反馈信息,模头进行自动调节模唇开度,得到厚度偏差控制在±2%以内的薄膜,再进行静电消除及分切收卷,最终得到的薄膜具有很好的表面平整度、光洁度和极     

精诚引进国际先进模唇加工技术

挤出平模头的核心部分在于流道的设计及模唇的加工精度控制,特别是模唇平直度、表面光洁度和模唇尖角。它直接影响着最终制品的质量,在要求比较高的光学级板片材和薄膜制品中应用就显得更     

高压静电净化器在ABS挤出机模头废气治理中的应用

当采取吸附法治理ABS装置挤出机模头废气时,若废气中颗粒物质量浓度超过1 mg/m3或含有吸附后难以脱附的成分时,则必须在吸附器之前进行预先处理。在挤出机模头废气组分中,除了挥发性有机气体外,还包含动物脂肪酸等影响吸附剂净化效率的物质,因此采用高压静电净化器对其脱除是一个不错的应用方向。     

基于Fluent仿真的流延辊流道设计研究

在流延薄膜的生产过程中,熔融聚合物从模头挤出后在流延辊上冷却的过程对流延薄膜的质量起着至关重要的作用。选取双进双出的矩形截面螺旋形流道的流延辊为研究对象,在利用F luent对其换热过程进行数值模拟仿真的基础上,分析研究流延辊的流道结构和尺寸参数对流延辊换热能力的影响,所得结果可为合理设计流延辊的结构、优化流延辊的参数提供指导。     

Numerical simulation of the wire‐pinning process in PET film casting: Steady‐state results

Poly(ethylene terephthalate) (PET) film casting involves melt flow through a slot die, across a small span, and onto a fast moving quench drum. In the “wire‐pinning” casting process, a thin electrified wire close to the line of contact with the drum creates a strong pinning force that delays air entrainment to higher line speeds. Nonuniform wetting of the die lips by the extruded melt is thought to be responsible for the formation of streaks, a defect in the machine direction. A finite element model of the film casting process with wire pinning was developed to assist in understanding what causes significant wetting of the lips and whether this can be avoided by electrostatic pinning. The solution of the governing equations provide the location of the static and dynamic contact lines, thus finding the wetting and pinning points in the process. The simulations investigate the sensitivity of the static wetting line locations on the die lands to the imposed values of static contact angle and die‐lip gap. It was found that while the contact angle has a small effect on the extent of die‐lip wetting within the parameter ranges examined, there is a considerable chance that the feed slot surfaces can be dewetted. This seems to be the greatest danger for causing streaks rather than excessive wetting of the die lands. © 2011 American Institute of Chemical Engineers AIChE J, 2012     

Experimental studies on the development of a cast film

The cast film process is of significant industrial interest. This work presents quantitative experimental results for the characterization of a film casting operation in the region between the die exit and the chill roll. The polymer melt employed is a commercial PET sample that has been characterized in both shear and extension‐dominated flows. Pointwise measurements of both the film temperature and the local velocity are made over the entire region between the die and the chill roll. The velocity increases in the gap, although the strain rate decreases as the polymer moves from the die to the chill roll. For a particular axial position, the velocity decreases significantly near the edges of the film. There are modest (～20 °C) decreases in the temperature between the die and the chill roll, with the greatest variations again occurring near the edges of the film. The experimental results are explained by the coupling between the temperature, velocity fields, and geometry of the experimental apparatus. POLYM. ENG. SCI. 45:443–450, 2005. © 2005 Society of Plastics Engineers.     

Study of the stability of the film casting process

A theoretical study of the film casting process has been carried out. In this industrial process, a molten polymer is extruded through a flat die, then stretched in air and cooled on a chill roll. This involves mainly an extensional flow. Between the die and the chill roll, thick edges are formed and a neck-in phenomenon is observed. Above a critical take-up speed, a drawing instability, known as draw resonance, may occur. In this paper, a one-dimensional model adapted from the classical model of the fiber spinning is developed (for a Newtonian or a Maxwell fluid). The influence of the processing parameters (draw ratio, Deborah number, and aspect ratio) on geometry of the lateral free surface (the so-called neck-in phenomenon) is studied. An unattainable zone very similar to the one encountered in fiber spinning is predicted, which only slightly depends on the stretching geometry (initial film width and stretching distance). The onset of draw resonance is studied through the linear stability method. A stability zone, depending on the geometry of the process, the elasticity of the polymer, and the draw ratio, has been obtained. This instability is observed with simultaneous width and thickness film variations. It is proved that the aspect ratio (stretching distance divided by die width) has a strong influence on the onset of the draw resonance instability.     

双向拉伸聚丙烯薄膜铸片成型水槽水循环系统的设计

冷辊水槽铸片成型法是生产双向拉伸聚丙烯(BOPP)薄膜常用的方法,通过优化升级改进了原有结构冷却效果不佳,调节不便等缺陷,使系统结构稳定可靠、操作维护便捷,铸片片材能够快速冷却定型,有效提高了薄膜的生产效率。     

Measurement and modelling of the film casting process: 2. Temperature distribution along draw direction

In the case film process a polymer melt is extruded through a slit die, stretched in air and cooled on a chill roll. During the path in air the melt cools and a reduction of both thickness and width takes place; obviously, temperature distribution, thickness and width reductions are function of draw ratio and stretching distance.Temperature distribution along the draw direction was measured as function of flow rate during film casting experiments performed with an iPP resin. A non-contacting method of measurement, based on a narrow-band IR pyrometer, was adopted.A good qualitative agreement is shown between experimental temperature data and predictions of a model accounting of radiation emissivity dependence upon film thickness. Differences are consistent with discrepancies of film thickness evolution along draw direction, indeed the model slightly over predicts both film thickness reduction and, parallel, temperature decrease along the draw direction.     

Numerical simulation of the cast film process

The cast film process is studied and a numerical simulation is performed using a finite element method. Two dimensional equations involving the thickness and a mean velocity are used by considering the film as a thin layer. The process is assumed to be isothermal between the die exit and the quick cooling on the chill roll. The width of the film is computed iteratively as a free surface problem by means of a finite element method. The thickness distribution of the film is obtained by a finite volume method. This approach allows modeling of the well known “dog-bone” or “edge bead” defect with a reasonable computation time.     

Determining the thickness of liquid film in laminar condition on a rotating drum surface using CFD

This is a pioneering paper that deals with the semi-steady-state liquid film thickness on a rotating drum partially submerged in liquid using CFD. The CFD predictions have been compared with both experimental results and analytical solutions. The liquid film thickness and the film rising on a circular curved wall were monitored for various rpm of the rotating drum. The 2D simulations were performed neglecting the end effects (assuming the rotating drum is very long). As the rotating drum speed was increased, the film thickness was found to increase at the film rising side and at the minimum film thickness point (top of the rotating drum). There was never been a steady-state condition reached, the opposite was expected as a wiper is used in the CFD calculation (same as the experimental investigation). The liquid that leaves the domain by the wiper (as outflow boundary condition) is forced to enter to the domain from far end to keep the level of the free surface constant.     

Orientation and crystallinity in film casting of polypropylene

In the cast film process a polymer melt is extruded through a slit die, stretched in air, and cooled on a chill roll. During the path in air the melt cools while being stretched. Film casting experiments were carried out with an isotactic polypropylene resin. The temperature and width distributions were measured along the draw direction. Further, the crystallinity and Hermans orientation factor were measured on the final film. The process was described by a simple thermomechanical model derived elsewhere. The evolution of the molecular orientation parameters was calculated on the basis of a dumbbell model coupled with velocity and temperature distributions provided by the thermomechanical model. The experimental crystalline orientations of the final films collapsed into a single step‐shaped curve (from low to high orientation) if plotted versus the stress calculated by the model at the frozen line. The experimental values of the crystallinity and Hermans orientation factors are discussed on the basis of predictions of the dumbbell model for melt orientation at the frozen line and the crystallinity data obtained in quiescent conditions under the same cooling rate. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 84: 1981–1992, 2002; DOI 10.1002/app.10422