外文翻译--成型机及其工艺的调节

- 1 - 附录 1 成型机及其工艺的调节 成型机 剪切性能高低由挤出机的螺杆结构所决定。但挤出质量优劣与挤出效率高低，还在于挤出工艺与挤出机剪切性能相适应。否则低剪切挤出机采用过高挤出速度挤出，难以生产挤出高质量型材制品，高剪切挤出机在过低挤出速度下运行，难以有效发挥挤出效率。不同剪切性能挤出机都有一定的工艺控制范围，是有限度的。业内倡导的挤出工艺路线为 “ 马鞍型 ” 即加热区设定温度要高一些，恒温区设定温度要低一些，保温区设定温度要高一些。但不同剪切性能挤出机在不同挤出速度下运行， “ 马鞍型 ” 的 “ 鞍 ” 与“ 座 ” 高低是完全不同的 。 在 木塑复合型材 挤出时，要最大限度发挥不同剪切性能挤出机的挤出效率，建立螺杆加热区供料段、压缩段与恒温区熔融段、计量段所需热量与所供热量的平衡是关键所在。依据挤出机剪切性能特点，不同剪切性能挤出机，挤出不同规格塑料异型材，应分别采取不同的挤出工艺，以适应制品质量性能的需求 。木塑复合 型材挤出，物料由玻璃态转化为熔融态共计有两种热源，一种是由电加热器提供的外加热，一种是由螺杆在旋转过程中对物料压延、摩擦、剪切产生的热量。在开机生产时，物料的熔融主要以外加热为主，在正常生产阶段，物料的熔融主要以螺杆对物料压延、摩 擦、剪切产生的内热为主。具有关资料表明：在型材挤出中，内热所占挤出机所供热量的比例，大致在 65以上。外加热温度控制系统主要是通过电器仪表元件实施温度设定与显示。当显示温度超过设定温度指标参数时，加热圈即刻断电，停止加温，并由螺杆油冷装置与螺筒风冷装置进行强制冷却；当显示温度达不到设定温度指标参数时，加热圈就一直不间断工作。由于内热主要受挤出机螺杆特性、加料与挤出速度的制约，不受外加热温度控制系统的影响。当低剪切挤出机挤出速度过高时，即使供料段与压缩段外加热圈工作频率提高，间歇时间很短，其显示温度亦可能达不 到设定温度；即使熔融段与计量段外加热停止工作并启动螺杆与螺筒冷却装置运行，显示温度仍可能远远高于设定温度。同时由于反映显示温度的测温点热电偶安装在挤出机螺筒壁上，与螺筒内物料有一定距离，仪表显示温度与物料实际温度在不同工况下则有一定梯 - 2 - 度，存在不同对应关系。一般情况下加料段与压缩段物料即存在外加热，又存在剪切热，为双向加热，显示温度基本等同于物料温度；熔融段与计量段物料显示温度未达到设定温度时，亦为双向加热。当显示温度超越设定温度时，热量开始由内向外传递，可称之为逆向传热，显示温度低于物料温度。由此可知低剪切 挤出机挤出速度较高时，螺杆熔融段、计量段物料实际温度不仅高于设定温度，也高于显示温度。因此当显示温度在设定温度区域运行时，设定温度参数基本等同于物料温度，是物料塑化熔融的控 制目标与依据。当显示温度偏离设定温度区域运行时，显示温度可假定为物料温度，即取代设定温度成为物料塑化熔融的控制目标与依据。设定温度只是增加或减少外供热的调控手段。对于低剪切挤出机，由于给料段、压缩段压缩比较小，所提供的内热远远满足不了玻璃态物料塑化要求，故给料段、压缩段温度设定应高一些，因配方不同，大致在 190200 左右，尽管在提高 挤出速度情况下，显示温度依然偏低，但提高设定温度的目的，是为了供料段、压缩段电加热圈，一直不间断工作，只要显示温度在 180185 区间，物料紧包裹于螺杆，处于微熔状态，不出现排气孔冒料现象，可视为正常；熔融段、计量段设定温度应低一些，因配方不同，大致在 165175 左右，尽管在提高挤出速度情况下，显示温度依然偏高，但降低设定温度的目的，是为了熔融段、计量段电加热圈适时停止加热，并启动螺杆油冷与螺筒风冷对物料进行冷却，只要显示温度在 180185 区间，挤出型坯截面未出现气孔、麻点等症状，可视为挤出速度正常 。反之即使给料段、压缩段温度设定的再高，加热圈不间断工作，排气孔物料疏松，呈豆腐渣状，未包裹住螺杆，从螺筒排气孔出现冒料现象；熔融段、计量段设定温度再低，电加热圈已停止工作，螺杆油冷与螺筒风冷一直对物料进行冷却，挤出型坯已出现气孔、麻点等症状，可视为挤出速度已到极限，应及时降低挤出速度或加料与挤出速度。 排气孔冒料是低剪切挤出机塑化不良的表征。但并非排气孔冒料都是低剪切挤出机所造成的。导致排气孔冒料主要有以下原因： 加料速度过快，所增加的剪切热不足于平衡所增加的给料量需要的热量，导致的塑料塑化不良； 挤出速 度过快，所增加的剪切热不足于平衡物料在给料段与压缩段停留时间减少而损失的热量，导致的塑料塑化不良； 配方采用 CPE 抗冲改性剂时，加工助剂添加量偏少，物料摩擦性能差，到排气孔时塑化不良； 配方中润滑剂过量，物料在挤出机内移动挤出速度过快，到排气孔时塑化不良； 挤出机螺杆与螺筒轴向间隙过大，漏流严重或螺杆给料段、压缩段温度过 - 3 - 高，导致物料 “ 过塑化 ” ，已转化为体的物料经历了压缩段第一次压力高峰后，到排气孔时应力释放，体积膨胀，粘附在螺棱端面，随螺杆转动被排气段螺筒刮落在排气孔管壁上，积累到一定程度从排气孔溢出。前两 种排气孔冒料均和挤出机剪切性能差有关，第三种与第四种排气孔冒料主要与配方有关，第五种排气孔冒料主要与挤出机磨损及剪切性能高有关。在判断排气孔冒料原因时，应综合考虑，不可盲目而定。如属于试验配方发生的排气孔冒料应调整配方；如属于挤出机磨损，应调整挤出机螺杆与螺筒间隙；如发现物料在排气孔 “ 过塑化 ” 应调整加料挤出速度比；前三种排气孔冒一般表现为扭距升高，后两种排气孔冒一般表现为扭矩降低。 4 附录 2 Shear properties in the molding machine height determined by the extruder screw structure. But extrusion quality fit and unfit quality and extrusion efficiency high and low, but also in the extrusion process with the shear properties in the extruder. Otherwise low shear extrusion machine adopts the high speed extrusion, it is difficult to produce extrusion profiles products with high quality, high shear extrusion machine running under low speed, difficult to play extrusion efficiency effectively. Different shear performance extruder has certain scope of process control, there is a limit. Industry advocacy of extrusion process route is saddle type means heating area set temperature, lower temperature zone set temperature, heat preservation zone set temperature. But different shear extrusion machine performance under different extrusion speed run, saddle type of saddle and bridge is completely different. When wood plastic composite profiles extrusion, to play a maximum efficiency of different shear performance of the extruder extrusion, establish screw heating zone feeding section, compression and constant temperature zone melting section, the metering section of calories and heating load balance is the key. Extruder based on shear properties, shear properties in the different extrusion machine, extrusion plastic different profile with different specs, should respectively take different extrusion process, in order to meet the needs of the product quality performance. Wood plastic composite profiles extrusion, the glassy state material into molten total there are two kinds of heat source, one kind is provided by the electric heater heating, one kind is by screw for material in the process of rotary rolling, the heat generated by the friction, shear. During post production, material outside heatings molten core, in normal production, the molten material mainly by the screw on the rolling material, friction, shear internal heat. With relevant data show that in profile extrusion, the internal heat of extruder by heating load, the proportion of roughly the above 65%. Outside the heating temperature control system mainly through electrical instrumentation components implement temperature setting and display. When temperature more than set temperature parameters, heating coil power immediately, stop the heating, and the screw barrel screw oil cooling device with air cooling device for cooling； When the temperature of the display is short 5 of set temperature parameters, heating coil has been uninterrupted work. Due to internal heat mainly by extruder screw characteristics, feeding and extrusion speed, not affected by heating temperature control system. When low shear extruder extrusion speed is too high, even if the feeding section and compression section of outer heating coil working frequency increases, intermittent time is short, its temperature also may not reach setting temperature； Even if fused segment and outside heating metering section to stop working and start the screw and screw cylinder cooling device operation, display temperature could still far higher than the set temperature. And due to reflect the temperature of the temperature measuring point thermocouple installed on the extruder screw are compared.in addition, a certain distance with screw tubes inside material, instrument show the actual temperature and material temperature under different conditions has a certain gradient, there are different corresponding relations. Usually charging and compression section material is heated, again there is a shear heat, heating for two-way, according to basic equivalent material temperature； Fused segment and the metering section material according to the temperature did not reach the set temperature, also for two-way heating. When the temperature beyond set temperature, heat started by passing outside introversion, could be called reverse heat transfer, temperature is lower than the temperature of the material. Thus the low shear extruder extrusion at high speeds, screw the molten material actual temperature, measuring paragraphs not only higher than the set temperature, also higher than that of temperature. So when the temperature in the operation of the region set temperature, set temperature parameters of the basic equivalent to the material temperature, is the material plasticizing melting control goal and the basis. When run display area of temperature deviates from the set temperature, temperature can be assumed to material temperature, namely the replaced set temperature as plasticizing molten material control goal and the basis. Outside the set temperature is increasing or decreasing heating control. For low shear extrusion machine, due to compression, compression paragraphs are small, provided by the internal heat is far cannot satisfy the glassy state material plasticizing requirements, therefore, feeding temperature setting, compressed paragraphs should be higher, because of the different formula, roughly around 190 200 , although in improving extrusion speed case, show the temperature is still low, but to increase the temperature of the set purpose, in order to feed, 6 compressed paragraphs electric heating circle, has been non-stop work, as long as the temperature within the range of 180 185, tightly wrapped in screw, material in micro molten state, not a vent to risk phenomenon, can be regarded as normal. Melting, metering section set temperature should be lower, because of the different formula, roughly around 165 175 , although in improving extrusion speed case, show the temperature still on the high side, but reduce the purpose of the set temperature, to melt, metering section electric heating circle timely stop heating, and start the screw oil cooling and screw cylinder air-cooled cooling, the supplies as long as the temperature within the range of 180 185 , extrusion parison section did not appear the symptom such as porosity, pitting, can be regarded as normal extrusion speed. And even feeding high temperature setting, compressed paragraphs, heating coil non-stop work, vent loose materials, and shows shape of bean curd, wrapped in not screw, screw tubes from vent appear to take material phenomenon； Molten set temperature, measuring paragraphs again low, electric heating circle has stopped work, screw oil cooling and screw cylinder air-cooled cooling, have been carried out on the material extrusion parison has symptoms such as porosity, pitting, can be regarded as extrusion speed has been to the limit, should be timely to reduce speed or charging and extrusion speed. Vent risk is low shear extrusion machine characterization of plasticizing adverse. But not vent take material are caused by the low shear extrusion machine. Lead to vent at material basically has the following reasons: 1) feeding too fast, the increase of shear heat enough to balance the increased quantificationally need quantity of heat, caused by the plastic plasticizing bad； (2) the speed too fast, the increase of shear heat enough to balance the material stay in feeding period and compression time reduced and the heat loss, caused by the plastic plasticizing bad； (3) formula using CPE impact modifier, processing AIDS add quantity is less, the material friction performance is poor, to vent plasticizing bad； (4) the formula of lubricant, excessive material in the extruder mobile speed too fast, to vent plasticizing bad； (5) with screw extruder screw barrel axial clearance is too large, serious leakage flow or screw feeding period, compression temperatur