The granulation process of PVC rubber pellets is a process for producing polymer resins and various additives and auxiliaries by metering, bonding, plasticizing and granulating. Granular plastic. Plastic pellets are semi-finished products in the plastic molding industry and are also extruded.
Injection molding, hollow blow molding and foaming and other molding processing materials.
The resin is available in both powder and granule form.
Granulation extrusion is the most basic and simplest method of granulation, and its application is extensive.
For various plastic molding processes, the advantages of using granular particles compared to directly processing the particles are as follows:
(l) Convenient feeding, no need to install a forced feeder in the hopper.
(2) The relative density of the particles is greater than the relative density of the powder material, and the strength of the plastic article is good.
(3) The mixing of the resin with various solid powder materials or liquid auxiliaries is relatively uniform, and the physical properties of the plastic products are relatively uniform.
(4) Plastic products are evenly colored.
(5) The particulate material contains less air volatiles, making the plastic article less prone to air bubbles.
(6) The particles are free from contamination on the extruder and production environment.
Production Process:
l. Preparation before ingredients
Preparation before batching includes screening and fractionation of resin, plasticizer requires advanced filtration and refinement, purification of powdered additives, preparation of masterbatch powder, drying of bulk additives, and heating and melting of blocks The polymer resin can be mixed with mechanical impurities or other impurities during production, packaging and transportation. In order to prevent damage to the granulation equipment and to reduce the quality of the product, the resin must be sieved and used. Powdered polyvinyl chloride is usually a 4O mesh screen.
Granular polyethylene or polypropylene is sieved and sieved through a fine mesh slightly larger than the resin.
In order to prevent mechanical impurities or black waste in the plasticizer from affecting the performance of the product, when producing cable materials, the plasticizer is usually filtered with a filter of 60 to 120 mesh [6O mesh is a large viscosity, and the l2O mesh is small. Viscosity.
For powdery additives which are coarser or easier to aggregate, it is preferred to first refine the slurry with a plasticizer, add the slurry, and mix and disperse in the resin to make it more uniform.
The refining equipment is a three-roll mill. The ratio of the general additive to the plasticizer in the refined formulation is about 1:1, and the slurry fineness index is 6O-8Oμm. The ratio of the slurry formulation is the ratio by weight. The proportion of the slurry is mainly determined based on the apparent density of the powder. The apparent density of the powder is large, and the amount of the plasticizer added is large.
Plasticizers typically use a low viscosity DOP.
In the amount of plasticizer added, the amount added during the refining process should be subtracted.

For rigid polyvinyl chloride products, since no plasticizer is added, a high concentration of polyvinyl chloride is usually prepared by first preparing a masterbatch powder and then adding it to a kneader for mixing.
For example, the method is used for dyeing rigid polyvinyl chloride tubes.
When the masterbatch is produced by a kneader, a suitable stabilizer should be added to prevent decomposition of the resin.
For hygroscopic resins and additives, water must be removed prior to kneading or extrusion.
For example, nylon resin and ABS resin are easily absorbed, and must be dried to a water content of less than 0.1%, a drying apparatus: a boiling dryer, a vacuum dryer or a vacuum drying hopper.
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Some functional masterbatches, such as antistatic masterbatch, anti-stick masterbatch, pearlescent masterbatch, filled masterbatch, etc., are easy to absorb moisture, and should be dried before being added to the extruder, otherwise it will affect the production or reduce the product.

Both stearic acid and paraffin are used as lubricants in plastic processing.
If added directly to the kneader, it will strike the baffle at high speed in the high speed kneader and damage the baffle. Therefore, it must be heated and melted before being added to the kneader.
Stearic acid has a melting point of 69.6O ° C, and paraffin has a melting point of 60 ° C
2, formula weighing
When the raw material is put into a kneader or a mixer for stirring and chewing, the feed amount should be estimated based on the volume and feed coefficient of the equipment.
According to the accurate weighing of the feed amount, the weighing must be accurate, otherwise the quality of the product will be unstable.
Weighing scales and automatic metering devices should be regularly inspected and calibrated to prevent quality fluctuations due to metering errors.
The third point, kneading
Kneading can be divided into heating kneading and cooling kneading, using a high speed kneader.
Heating and kneading process conditions: soft polyvinyl chloride kneading time lO ~ l5min, discharge temperature 95 ~ lOO ° C; rigid polyvinyl chloride kneading time 5 - lOmin, discharge temperature lOO - lO ° C.
Further, the order of addition at the time of kneading has an influence on the kneading quality.
The temperature of the material from the high speed kneader cooled and kneaded is higher than 100 ° C. If it is placed in a storage cylinder, it is prone to discoloration, agglomeration and even decomposition of the material.
Therefore, cooling mixing must be carried out immediately to lower the temperature of the material below 50 ° C for storage in the extruder.
The cooling mixing process conditions are soft and rigid polyvinyl chloride, the kneading time is 5 - 10 min, and the discharge temperature is lower than 5O ° C.
The process conditions for mixing the soft masterbatch are as follows: soft polyvinyl chloride and polyethylene with a 5OL internal mixer. The soft vinyl chloride is mixed for 3 to 5 minutes at a mixing temperature of 90 to 110 ° C and the temperature of the material is discharged.
lOO ~ llO ° C; polyethylene mixing time 8 - lOmin, mixing temperature 8O - lOO ° C, discharge temperature l4O - l45 ° C.
The mixed material is an agglomerate and no unplasticized powder or granules can be released.
Fourth small point, extrusion granulation
Extrusion granulation can be carried out using single screw and twin screw extruders.
Mainly controls extrusion temperature, screw speed, cutting speed and particle cooling.
The particles are not bonded, the particle size is uniform, and the plasticization is better.
The cutting speed was adjusted to a particle length of 3 to 4 mm.
Adjust the screw speed so that the particles are not sticky.
Extrusion of soft PVC rubber cable material, single screw extruder with diameter of 65mm is l4O——l5O° C, l6O~l7O°C, l5O~l6O°C, l5O~l6O°C, rotation speed is 2O~3Or / min; diameter 5l
——The temperature of l5Omm twin-screw extruder is l3O——l4O°C, l4O——l45°C, l5O——l55°C, l45——l5O°C, screw speed is l5——2Or / min.
Granular polyethylene, 6mm diameter parallel twin-screw extruder, temperature 2OO - 22O ° C, 23O - 24O ° C, 24
O - 25O ° C, 25O - 26O ° C.