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Yuanlei Small Classroom | Requirements of Calcium Carbonate for Plastic Film and Production Technology of Masterbatch

Release time:

2024-01-29 09:35

 

Yuanlei Small Classroom | Requirements of Calcium Carbonate for Plastic Film and Production Technology of Masterbatch

 

CarbonCalcium acid is widely used in plastics, which can not only reduce the cost, but also improve the performance of some aspects of plastic materials. For example, the activated light calcium carbonate can improve the impact toughness of polyvinyl chloride plastics, the heavy calcium with a certain fineness can significantly improve the impact toughness of polyethylene plastics and polypropylene plastics through interface control treatment, and the polypropylene woven bag with ordinary fineness heavy calcium carbonate, its surface slip resistance and printability are improved, etc.

 

1. Requirements for calcium carbonate for plastic film

 

At present, the use of polyethylene plastic film is1250 Objective Heavy Calcium. The 1250 mesh referred to herein means that the maximum particle diameter is not more than 10 μm. Some companies have d97For how many microns to indicate the particle size of heavy calcium,.Plastic film is concerned that the maximum particle size should not exceed 10 μmBecause there are many film products (such as plastic film), the thickness of itself is less than 10μm, even if the large particles only account for one ten thousandth, the absolute number (number of particles) will be very large, and each large particle may cause quality accidents of plastic film.

 

It must be noted that it is not that heavy calcium thicker than 1250 mesh cannot be used, nor is it that heavy calcium thinner than 1250 mesh is so bad. In the case of good dispersion, the smaller the particle size of heavy calcium, the better the mechanical properties and appearance of the plastic film at the same filling amount.

 

Considering that the finer the price of heavy calcium is higher, and the current technical conditions that mainly rely on high-speed mixers for surface treatment of heavy calcium, the heavy calcium used in polyethylene plastic film should be 1250 mesh, and the fineness is too fine, which will lead to problems that are difficult to solve in surface treatment and dispersion.

 

Whether light calcium can be used in polyethylene plastic filmSo far, no one has used light calcium, but it does not mean that it cannot be used. Ordinary light calcium is mostly a few microns of particles of agglomerates, to disperse them more difficult. In addition, the crystal form of light calcium particles is very different from calcite, and the difference in refractive index has a more significant effect on the light transmission of PE film.

 

Nano calcium carbonate is essentially light calcium carbonate, there is also the problem of particle agglomeration, and because the price is much higher than ordinary light calcium, so no one is interested.

 

2, Calcium carbonate masterbatch production process technology points

 

(1) The issue of reunion

 

In order to make the calcium carbonate particles in the filling masterbatch evenly dispersed into the matrix plastic, the calcium carbonate particles must be completely coated. If the calcium carbonate has agglomerated during the production of the filler masterbatch, the agglomerated particles cannot be opened in the blown film extruder, and numerous white spots are inevitably formed on the film. Even white hard particles may form "clouds".

 

Solving the problem of agglomeration of calcium carbonate particles is first to prevent excessive friction during surface treatment, and once static electricity is generated due to friction, agglomeration is extremely easy to occur. The second isAdequate amount of surface treatment agent. When the surface of the particles is changed to lipophilic by the coupling agent, the surface energy is greatly reduced, and it is not easy to coagulate with each other.

 

(2) Filling ratio problem

 

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 particle size of calcium carbonate particles is small, the number of particles is large, and the total surface area is also large, more carrier resin is needed to cover it. Not only the melt viscosity of the carrier resin is required to be small, but also a sufficient amount. In order to obtain a film-grade filling masterbatch with good performance,The weight percentage of calcium carbonate is generally not more than 80%, and the weight percentage of carrier resin is generally not less than 13%.

 

(3) Material form problem

 

There are different views on what form the material in the high mixer should be stirred. Some people have tried to stir into a complete paste and then put the material and only mechanically mix it evenly. The particles of the carrier resin still maintain the original particle form and put the material. There is no obvious difference in the application effect of the filling masterbatch made by the two extreme cases in the film.

 

Our experience isIt is best that the carrier resin has begun to melt, and the surface-treated heavy calcium is fully contacted to form a noodle-like shape but not into a paste. At this time, the material is immediately released.. If it is pasted, it is very difficult to discharge the material, which reduces the production efficiency. If the material still maintains the state of particles and powder, not only cannot the components be uniform and consistent, but also the particles and powder are separated again when feeding into the twin-screw extruder, resulting in more heavy calcium and more resin in the product, which will lead to uneven material when blowing the film, and "clouds" or white spots are easily occurred.

 

(4) Extrusion equipment

 

The extruder used for material mixing, kneading and granulation is also very important, and the co-rotating parallel twin-screw extruder is far better than the single-screw extruder with mixing section. The advantages of mixing granulation equipment can make up for the lack of surface treatment of calcium carbonate in high mixer and initial mixing with carrier resin, so the selection of artificial extrusion mixing granulation equipment and the selection and arrangement of thread sleeve are also very important.

 

(5) Granulation problem

 

In the granulation part, the operation mode of water cooling should be avoided as far as possible, because of the level of manual operation and the problem of responsibility, once the material carries water, it will bring major hidden dangers to the blown film. If polyethylene resin is used as the carrier resin, it is appropriate to choose the air-cooled mold surface hot cutting process.

 

The shape and size of the particles are very particular, generally with a diameter of 3~5mm disc is appropriate, the thickness of about 1mm can be, mainly in order to blow the film, easy to mix with the particles of the matrix resin, in a short period of time to melt quickly and facilitate the matrix resin material mixed with each other.

 

When the diameter of the extruder is large (for example, the diameter is above Φ72mm) and the output is higher than 300 kg/h, the hot-cut head of the air-cooled die surface is difficult to do well, the temperature is not easy to control, the particles cannot be cooled down, and it is easy to adhere. At this time, it is advisable to use the conveyor belt cooling method, and this method is suitable for the production of various filling masterbatches or modified special materials, but it requires a longer distance cooling and requires a larger site.

 

 

 

 

Requirements, particle, calcium carbonate, resin, film, surface, filling, problem, plastic film, material

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