Views:19 Author:Site Editor Publish Time: 2017-03-30 Origin:Site
Resin is divided into powder and granular. PVC plastic granules have good processing properties. There are many PVC plastic granules can be made from plastic in our life, such as food waste bags, sandals, wire, plate, agricultural film, pipe, barrels, pots.Granulation by extrusion is the most basic and simple method of granulation and it is widely used.
Compared with the direct processing of powder material,the advantages of using PVC plastic granules are as follows:
(1) Convenient feeding, no need to install the forced feeder in the hopper.
(2) The relative density of PVC plastic granules than the powder material, plastic products, good strength.
(3) Resin and a variety of solid powder or liquid additives mixed more uniform, plastic products, the physical properties of more uniform.
(4) Plastic products uniform color.
(5) The PVC plastic granules contain less volatile matter, so that the plastic products are not easy to produce bubbles.
(6) Pellets are not contaminated by extruders and production environments.
1. Before the preparation of ingredients
Preparation of ingredients before the preparation, including resin screening, plasticizer filtration, powder additives, refining, color masterbatch powder preparation of raw materials drying, lump of additives such as heating and melting processes.
Polymer resin in the production, packaging, transportation process, may be mixed with mechanical impurities or other impurities, in order to prevent damage to granulation equipment and reduce product quality, the esin must be sieved after use, powder PVC generally use 40 mesh screen, Granular polyethylene or polypropylene sieves can be sieved with fine filaments larger than the resin size.
In order to prevent the plasticizer within the mechanical impurities or black garbage mixed products, affecting product performance, the production of cable material, the plasticizer generally used 60 ~ 120 mesh filter [viscosity with 60 mesh, small viscosity 120 mesh.
It is preferable to use a plasticizer for the thickening or easy agglomeration of the granules. The slurry is added to the slurry, and the mixture is dispersed more uniformly in the resin. Refining equipment for the three-roll grinding machine, grinding formula General additives and plasticizer ratio of 1: 1 or so, the slurry fineness index of 60 ~ 80μm.
The ratio of the slurry formulation is the ratio of parts by weight, the proportion of which is mainly based on the apparent density of the powder, and the apparent density of the powder is large. Plasticizers generally have a small viscosity of DOP. In the amount of plasticizer feeding, should be deducted when the amount of grinding.
For rigid polyvinyl chloride products, because of the addition of plasticizers, it is generally first to produce a high concentration of polyvinyl chloride masterbatch powder, and then add a kneader to mix. For example, this method is used for hard PVC pipe dyeing. When making the masterbatch with a kneader, the stabilizer should be added as appropriate to prevent the decomposition of the resin.
For easy absorption of moisture resin and additives, in the kneading or extrusion must be dry before removing water. For example, nylon resin and ABS resin are easy to absorb water, must be dried to less than 0.1% water content, drying equipment: boiling dryer, vacuum dryer or vacuum drying hopper and so on.
Some functional masterbatches, antistatic masterbatches, anti-blocking masterbatches, pearlescent masterbatches, filler masterbatches, etc., are easy to absorb moisture, before adding the extruder should be dry, otherwise it will affect the production or reduce the product quality.
As a block of stearic acid and paraffin are used in plastic processing more lubricants. If the kneading machine is directly fed into the kneading machine, the baffle plate may be damaged by high-speed kneading machine, and the baffle plate may be damaged by heating and melting. Stearic acid has a melting point of 69.60 ° C and a melting point of paraffin at 60 ° C.
2.The formula weighing
Into the kneading machine or mixer for mixing, plasticizing the raw materials, the first should be the volume of equipment and feeding coefficient, to estimate the amount of feeding.
Accurate weighing according to the amount of feeding, weighing must be accurate, otherwise it will make the product quality is not stable. Weighing and automatic weighing devices should be regularly checked and corrected to prevent fluctuations in quality due to measurement errors.
The kneading can be divided into a kneading with heating and kneading with a high speed mixer.
Heating and mixing process conditions: soft polyvinyl chloride mixing time 10 ~ 15min, discharge temperature 95 ~ 100 ℃; hard polyvinyl chloride mixing time 5 ~ 10min, discharge temperature 100 ~ 110 ℃. In addition, the feeding order at the time of kneading has an influence on the kneading quality.
Cooling mixing from the high-speed mixing machine out of the material temperature is higher, more than 100 ℃, if put into the storage tube, prone to discoloration, knot and even material decomposition. Therefore, the need for immediate cooling and mixing, so that the material temperature dropped to below 50 ℃, in order to store for the extruder. Cooling and mixing conditions regardless of soft, hard polyvinyl chloride are mixing time 5 ~ 10min, the material temperature below 50 ℃.
Mixing with 50L Banbury mixer, mixing soft polyvinyl chloride and polyethylene masterbatch of the process conditions are as follows, soft vinyl chloride mixing time 3 ~ 5min, mixing temperature of 90 ~ 110 ℃, the material temperature 100 ~ 110 ℃; polyethylene mixing time 8 ~ 10min, mixing temperature 80 ~ 100 ℃, the material temperature 140 ~ 145 ℃. Dense material for the group-like material, can not have non-plastic powder or pellets release.
Extrusion granulation available single screw and twin screw extruder. Mainly control the extrusion temperature, screw speed, cutter speed and pellet cooling. So that aggregates do not occur particles, particle size uniform, better plastic. Cutter speed adjustment to the pellet length 3 ~ 4mm. Screw speed adjustment to the pellets does not occur adhesion. Extruded soft polyvinyl chloride cable material, the diameter of 65mm single screw extruder temperature 140 ~ 150 ℃, 160 ~ 170 ℃, 150 ~ 160 ℃, 150 ~ 160 ℃, the speed of 20 ~ 30r / min; diameter 51 The temperature of the twin-screw extruder is 150 to 150C, the temperature is 150 to 155C, and the screw rotation speed is 15 to 20 r / min. Diameter 6mm parallel twin-screw extruder granulated polyethylene, the temperature is 200 ~ 220 ℃, 230 ~ 240 ℃, 240 ~ 250 ℃, 250 ~ 260 ℃.