Polymer materials granulation technology parsing

Most of the polymer before make the final product, must cooperate with mixing, granulation, then become to sales of raw materials.There are many different granulating machine design, but all granulation can be divided into two categories: the surface of cold pelletizing system and eagerly particle system.The main difference is that the granule process of both the arrangement of the time.Cold pelletizing system, at the end of the process from the solidification of the polymer pelletizing;In the mold surface eagerly grain system, when the molten polymer from the mouth of the mould in the cut grain, and cooled to aggregate in the downstream.Two kinds of pelletizing systems have their advantages and disadvantages.

The cold pelletizing systemCold pelletizing system including mold, cooling area (air cooling or water cooling), dry area (if the water) and grain cutting room.Cold pelletizing system has two kinds big, namely material granulator and strip material granulator.Crisps granulator molten polymer from mixing equipment through a die or roller conveyor for refining machines, rolling into a certain thickness of polymer material.Piece of material in transit through a distance solidification and cooling, and then in a bin with diced knife cut into round or square aggregate.1Crisps granulation is the oldest method of manufacturing aggregate, from nylon to PVC can be used for a variety of different polymer. According to the report accuracy is quite good, granulating capacity can reach 1843.69 kg/h. This is a method of cold cut grain noise emissions than from the molten polymer pelletizing method is high.Solidification state cutting short life polymer cutter, generate powder is often a problem.For some polymer can see some "bead chain" phenomenon.The use of the strip material granulator history almost as long as pieces of seed pelleting machine.Including mold, cooling section (water bath or blower), dry (if the water) and dicing cutter.With extruder or gear pump extrusion of polymer melt through a horizontal installation the mouth of the mould to form a strip material (the mouth of the modern mold precision machining, uniform heating, stable quality of a material to output).Strip material from the mouth after discharge, the box fan or air/vacuum facilities for cooling, or use cool water bath.If using water, strip material through a dry period, with forced ventilation blowdown water, and then will be sent to the grain cutting chamber.Using a pair of the shearing action of fixed and rotating knives, the article is expected to precisely cut into the required length.Aggregate diameter is 3.175 mm, 3.175 mm long, clear edges and corners.Article of the traditional control method is stretching the material by cooling segment (bath) is the most commonly used, sometimes cause stock dropped or size is not consistent.The strength of the most common in molten poor polymer, such as polypropylene, polyester and nylon, etc.When the stock fell, material or scrap, so operators need to pay close attention to.If the stock control, downstream aggregate need sieving.Into a method on the model of other without operators close monitoring, the way is driven by motor grooved feed conveyor, in from the mouth to the dicing machine supporting and splitter bar.The size of this article by spin force transmission is evener,

Don't fall and therefore less scrap.Some of this kind of method can make its production capacity up to 6803.89 kg/h, and compared to stretch into a method only about 1814.37 kg/h, because operators can only look after a finite number of strip material.Material production line cost is not high, the operation is simple, convenient and clean.It has advantages for pigment mixing, because two batches of different pigment changes must be thoroughly cleaning equipment.Build a downside, however, is cooling section to take up the space, its length to determine according to the requirements of the temperature of the polymer.Die eagerly systemDie-face eagerly system there are three basic types, namely the airflow granulator, water spray (water ring) granulator and underwater pelletizer.Although this kind of system can have different design, typical system including mouth die, blanking room, electric knife rotating blades, cooling medium and the method of dry granular materials (if the water).Mouth mold is an important part of a mold surface heat granulation system.It vertical or horizontal installation, usually oil, steam drum or belt type electric heater heating.Electric heating is usually used in the mouth of the smaller;But the mouth of the larger die usually use steam or oil heating.Mouth structure material with different material, but regardless of the material or what kind of heating medium, mouth die orifice diameter must be uniform,Want to have enough heat to sustain the whole extrusion process of polymer temperature;Dicing blade on the rotation surface must be tough smooth - these are necessary for manufacturing uniform aggregate.When molten polymer squeezed export mode, with high speed rotating cutting knife to cut it into aggregate.Typically dicing knife or contact or very close to the surface.Aggregate, after being cut off by the effect of centrifugal force is cast a knife, and delivery to the cooling medium.Dicing cutter size, shape, material and installation can be different.Some grain cutting knife in the system have a spring applied load automatically adjusts spacing between grain cutting knife, mouth mould;And some of the system must adjust dicing cutter by hand to mouth of spacing.Because the cutting material cutting knife life depends on a die for accuracy, polymer abradability and operator's aggressive, cutting polymer materials under the molten state is desirable.Airflow granulator recommended for sensitive to heat and long residence time of polymer, such as PVC, TPR and crosslinked polyethylene.Polymer pelletizing rate as high as 4989.52 kg/h from extruder to pelletizing chamber flow path to keep as short as possible, and using the least amount of heat.When polymer mode when it is squeezed through the mouth, stick surface rotation of spinning force is going to cut it into aggregate.Aggregate after cut off, and then be clear of rotating knife, specially designed for cutting is captured by the grain of the forced circulation flow of air in the room.Air flow of the aggregate surface preliminarily quenched, and put it out of the grain cutting chamber and sent to the cooling zone.Fluidized bed drier is often used to cool the aggregate.Aggregate along an adjustable inclined plane slip, while the circulation fan drum wind through the aggregate.Adjust the bevel Angle can be extended or aggregate residence time in the dryer.Another common cooling method is the aggregate from the grain cutting room discharged into a water tank, and then with a fluidized bed dryer or centrifugal dryer moisture removal.Water spray granulator, besides low melt viscosity or sticky polymer, suitable for most polymers.This kind of equipment is also known as water ring dicing machine, granulation rate of 13607.77 kg/h.

Molten polymer from the hot die out, is to mould the rotation of the rotating knife cut into aggregate.The characteristics of gansu granule system is its special design of water jet cutting room.Water in spiral wound for flow, until out of gansu grain of chamber.Aggregate after cut, is thrown into the water, a preliminary quenched.Aggregate water slurry into the slurry tank was further cooling, and then into the centrifugal dryer moisture removal.Underwater pelletizer and airflow granulator and water spray granulator similar, different is that it has a smooth flow through the die surface, and direct contact with surface.Cut the size of a grain of room with just enough to make dicing blade rotation freely across the surface without limit flow.Molten polymer from die extrusion, rotating knife cut aggregate, aggregate is after tempering of hose out pelletizing chamber into the centrifugal dryer.In the dryer, water back to the storage tank, cooling and circulation to use;Aggregate by centrifugal dryer to remove moisture.Underwater pelletizer use uniform heat distribution and have the mouth of the special facilities for adiabatic mode.Small granule cutter adopts electric heating;Large grain cutting knife need to use the mouth of oil heat or steam heating mode.Process water normally heated to high temperatures, but the heat should be enough to cause harmful effects to the free flow of aggregate.Underwater pelleting machine used for most polymers, some models can reach 22679.62 KGLH ability of granulation.When used in low viscosity or adhesive polymer pelletizing when water flows through a mouth mold die way below is a big advantage, but for some polymers such as nylon and polyester the characteristics of some brands may cause mouth mold to freeze.Other advantages are: because in the molten state incised, and water plays a sound barrier effect, low noise emissions;Compare with cold cutting system of dicing blade fewer.Centrifugal granulatorCentrifugal granulator due to only use mouth or only need a minimum quantity of heat, not hot die surface cutting machine, and because of molten polymer pelletizing, nor cold cutting system, but is sui generis.Characteristics of this kind of pelleting machine is to use cylindrical mold, extruding hole distribution along its circumference.Molten polymer under ordinary conditions of feeding.By the depth of the melt on the rotor, the rotor speed and the relative density of polymer extrusion pressure.With cylindrical mouth mold with the spindle rotating at high speed, centrifugal force role make molten polymer evenly to every orifice of mouth on the mold.After the polymer flow from extruding hole, the mouth of the rotating die will flow out of the material to cut knife.Dicing cutter can use fixed, area often make it in the form of the "band saw two very slowly turn the wheel.Such a slow turning helps to keep the dicing cutter wear uniform and low temperature.Cut after aggregate, aggregate because of its own momentum, along a straight line trajectory into a warehouse indoor water for cooling, then adopt similar to other hot die surface granulator application method and dry.