Views:89 Author:Site Editor Publish Time: 2019-07-15 Origin:Site
Five issues to be aware of during the production of calcium carbonate filler masterbatch:
1. Surface modification treatment of calcium carbonate
In order to uniformly disperse the calcium carbonate particles in the filler masterbatch into the base plastic, the calcium carbonate particles must be completely coated. If calcium carbonate has agglomerated during the production of the filler masterbatch, such agglomerated particles can not be opened in the blown film extruder, and a large number of white spots are bound to form on the film. Even white hard particles may form a "cloud."
To solve the problem of agglomeration of calcium carbonate particles, pay attention to two aspects:
The first is to prevent excessive friction during surface treatment. Once static electricity is generated by friction, it is prone to agglomeration.
Secondly, the amount of the surface treatment agent is sufficient. When the surface of the particles is changed to lipophilicity by the action of the coupling agent, the surface energy thereof is greatly lowered, and it is difficult to cohere with each other.
2, calcium carbonate filling ratio
The higher the proportion of calcium carbonate in the filler masterbatch, the lower the raw material cost of the product and the more competitive the market. Since the calcium carbonate particles have a small particle size, a large number of particles, and a large total surface area, more carrier resin is required for coating, and it is required not only that the carrier resin has a small melt viscosity but also a sufficient amount.
In order to obtain a film-grade filler masterbatch having good performance, the weight percentage of calcium carbonate is generally not more than 80%, and the weight percentage of the carrier resin is generally not less than 13%.
3, physical mixing state
There are different opinions on what form the material in the high-mixer should be stirred up. Some people have tried to stir into a complete paste and then discharge the material evenly, and the particles of the carrier resin remain in the original particle form, and the effect of the application of the filler masterbatch in the two extreme cases in the film is not significantly different.
Our experience is that the best carrier resin has begun to melt, and the surface treated heavy calcium is in full contact to form a dough-like shape, but not to be paste, and the material is discharged immediately. If it becomes paste, it is very difficult to discharge, and the delay time reduces the production efficiency. If the material still maintains the state of particles and powder, not only can the composition be uniform, but also when the material is fed into the twin-screw extruder, the powder is again Separation, resulting in more calcium in the product, and some resin, there will be uneven material when blowing the film, it is easy to occur "cloud" or white spots.
4, the choice of extruder
Extruders for material mixing and granulation are also very important. Co-rotating twin-screw extruders are far superior to single-screw extruders with mixing sections, while reciprocating single-screw extruders are super-production. The film-level filling masterbatch with fine heavy calcium as the main raw material has better effect than the co-parallel twin-screw extruder.
The advantages of the mixing and granulating equipment can make up for the shortage of the surface treatment of calcium carbonate in the high-mixer and the initial mixing with the carrier resin. Therefore, the selection of the manual extrusion mixing and granulating equipment and the selection and arrangement of the threaded sleeve are also essential. of.
5, cooling method
In the granulation part, the operation mode of the strip water cooling should be avoided as much as possible. Because of the level of manual operation and the responsibility of the material, once the material is brought with water, it will bring a major hidden danger to the blown film.
If polyethylene resin is used as the carrier resin, it is suitable to use an air-cooled die face hot cutting process. The shape and size of the particles are very particular. Generally, a wafer with a diameter of 3 to 5 mm is suitable, and the thickness thereof is about 1 mm, which is mainly for mixing the particles of the matrix resin when the film is blown. Rapid melting in a short time facilitates blending with the matrix resin material.
When the extruder has a large diameter (for example, the diameter is above Φ75mm) and the output is higher than 300kg/h, the head of the air-cooled die face is difficult to do well, the temperature is not easy to control, the particles are not cooled down, and it is easy to stick. At this time, it is preferable to use a belt cooling method, and this method is suitable for the production of various filler masterbatch or modified special materials, but requires a long distance to cool, requiring a larger site.