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Application of black masterbatch in plastic products

2020-03-04 392

In the plastic product molding process, almost everyone has used the black masterbatch, which is used for dyeing, anti-aging, conductive products and so on. Many problems in the use often bother us. We will discuss some issues of common concern and hope to bring you harvest.

1. What is the composition of black masterbatch?

The materials of black masterbatch are: A. carbon black; B. carbon black carrier; C. carbon black wetting agent; D. carbon black dispersant; e. other processing aids.

2. Please introduce carbon black for black masterbatch.

According to the international classification, there are more than 30 varieties in China. It is mainly divided into rubber and non rubber. In rubber carbon black, it is mainly wear-resistant carbon black, which can effectively improve the wear resistance of rubber tires; in non rubber carbon black, there are only a few carbon black that can be used as black masterbatch. Bath carbon black is the most widely used in plastics because of its rich source, high purity and small particle size. Among them, there are high pigment carbon black (particle size 9-17mm), medium pigment carbon black (particle size 18-25mm) and low pigment carbon black (particle size 26-37mm). Due to different varieties of carbon black, the price varies greatly. Due to its own multi activity, carbon black particles rarely exist as primary particles, and almost all exist as agglomerated particles with a certain range of particle size.

3. What about the carbon black carrier?

Carrier is the material carrying carbon black. General plastic products use what raw materials, the carrier will use what raw materials. The black masterbatch produced in this way has good compatibility with plastic raw materials. For example: PS (polystyrene) plastic products, its use of black masterbatch carrier is PS. For polyethylene plastic products, the carrier is polyethylene. However, LDPE (high pressure polyethylene) is generally selected, because LDPE has the strongest carbon black bearing capacity and good processing performance. Other HDPE and LLDPE can only produce low concentration black masterbatch. For PP (polypropylene) plastic products, only the black masterbatch with PP and LDPE as carriers can be used, but the black masterbatch with HDPE, LLDPE and other plastics as carriers cannot be used. Of course, it also uses recycled materials as carrier black masterbatch.

4. Why does carbon black need wetting agent?

The specific gravity of carbon black is about 2G / cm. Because the particle size of carbon black is very small, the performance density is very small, and it appears to be fluffy and light. In order to process smoothly, the carbon black must be wetted first. The selection of wetting agent is very important. In order to reduce costs, there are not a few enterprises that use a large number of white oil or paraffin products, which will seriously affect the strength of processed products.

5. What dispersants are used for carbon black masterbatch?

There are two kinds of dispersants: organic dispersant and inorganic dispersant. High grade black masterbatch uses organic dispersant, which is mainly used for plastic products with high environmental requirements, such as drip irrigation products. Low grade black masterbatch uses inorganic dispersant, commonly calcium carbonate. It can be judged from the color masterbatch packaging that only half a 25 kg bag must be filled with inorganic dispersant, and the black masterbatch filled with organic dispersant. The use of inorganic dispersant can greatly reduce the cost of black masterbatch, but it is fatal that calcium carbonate can accelerate the aging of plastic products.

6. Does black masterbatch need processing aids?

Of course. In order to process smoothly, antioxidant, internal lubricant, external lubricant, modifier and antistatic agent should be selected correctly.

7. What are the processing methods of black masterbatch?

There are three methods: single screw method, double screw method and close love method. Single screw method: after the materials are mixed by the mixer, the single screw extruder is used to stretch and granulate the materials. Generally, the carbon black concentration is 18-20%. The process is backward, and the environmental conditions at the production site are poor, so it is a eliminated process. Some small factories just started are still using this method for processing. Twin screw method: after the materials are mixed by the mixer, they are drawn by the twin-screw extruder or granulated by the water ring. Due to the limited mixing capacity of the twin-screw extruder, the carbon black concentration of the masterbatch is generally 25-32%. Internal mixing method: after the materials are mixed by the mixer, kneaded by the mixer, fed by the feeder into the twin-screw extruder, and cut into particles through the water ring or underwater, the carbon black concentration of the masterbatch is generally 40-45%.

8. Does the processing method affect the performance of Color Masterbatch?

Yes. Obviously, the internal mixing method improves the carrying capacity of the carrier for carbon black, and carbon black can enter the carrier more evenly. The other two methods can't be replaced by the other two methods, which make use of the mechanical kneading advantage of internal mixer to break the agglomerated particles and greatly reduce the agglomerated particle size of carbon black particles.

9. What are the outstanding aspects of black masterbatch?

In terms of plastic products dyeing, black masterbatch only needs 0.6% - 0.8%, it will be extremely black, and no matter how much it is added, it will not be blacker. According to the test data, if the products used outdoors in Xinjiang need to rely on the black masterbatch for anti-aging, as long as the high-quality black masterbatch is used (instead of the kind of recycled material as the carrier, white oil wetting, calcium carbonate dispersion, etc.), the content of carbon black in the products reaches 2-2.5%, that is, 5-6 parts (weight) of masterbatch containing 40% carbon black in every 100kg of raw materials play a far more important role Any anti-aging products, product life can reach more than 10 years. That's why drip irrigation products, water delivery products and communication cable products are all black. In addition, carbon black has a special contribution to the strength and conductivity of products.

10. It seems that there are not so many copies of black masterbatch used in actual production?

You're right. In the actual production, about 2 parts of black masterbatch are generally used, and anti-aging additives are added. The synergistic effect of anti-aging and carbon black is used to reduce the product cost. In addition, the length of outdoor use time and the requirements of product life also determine that the use of black masterbatch should be reduced appropriately, provided that carbon black must form a continuous phase in the product, that is, carbon black "film" protective plastic. If the black masterbatch is added too little, the carbon black phase (i.e. the part with high concentration of small pieces) is not continuous in the product. At the boundary between the phase and the phase, the plastic molecule is the most vulnerable, and it is directly hit by ultraviolet light to accelerate the oxygen aging reaction. At this time, the carbon black in the product is like impurities, so it is better not to add. When the boundary between phases is less than 280mm, UV light can be avoided, and the products are safe.

11. How to judge the quality of black masterbatch from its appearance?

Good quality black masterbatch with good luster and moderate hardness. Too much oil indicates too much oil, and too little luster indicates that the carrier is recycled or too much calcium carbonate. Good quality black masterbatch is bited with teeth, soft with crispness. Too soft indicates too much organic dispersant, soft and loose indicates that the carbon black concentration is low and contains more calcium carbonate, too brittle indicates that the carbon black content is too high, or the carrier is recycled.

12. What's the matter with the small pockmarked surface on the product surface after using black masterbatch?

If the pockmarked surface is a small protruding point, it means that the product processing equipment has limited ability to disperse the masterbatch and cannot shear the carbon black agglomerated particles uniformly in the masterbatch, so the black masterbatch with lower concentration should be used; or the masterbatch has too much calcium carbonate and too much white oil, which is extruded by single screw and twin-screw machines under high pressure to form small rigid blocks and cannot be dispersed. If the pockmarked surface is concave, it is caused by the volatilization of small molecules in the masterbatch, indicating that there is more white oil.

13. Can the black masterbatch containing calcium carbonate be used?

Take a comprehensive view. First of all, if the fineness of calcium carbonate in the black masterbatch is 1000 mesh and the content is within 10%, it is a good choice for products without outdoor exposure requirements, and the price is low. The appearance of the product is glossy, the carbon black is evenly distributed in the processing, the blackness is not affected, and the influence on the product strength is small. If the fineness of calcium carbonate is less than 1000 mesh, it may appear dull luster, rough surface and decreased product strength. If the amount of 1000 mesh calcium carbonate is more than 10%, the surface of the product will be dull and gray, the blackness will not be enough, and the strength of the product will decrease. Secondly, in any outdoor products with anti-aging requirements, it is not good to contain calcium carbonate, depending on the service life of the product.

Finally, the use of such black masterbatch requires the use of high shear capacity equipment.

14. Do you choose black masterbatch with high carbon black content to reduce the cost?

The higher carbon black content means that the more difficult it is to disperse, the higher the shear capacity of the equipment, and the larger the length diameter ratio, the mixing section and the wear-resistant screw are needed, which depends on the equipment. For the equipment with good mixing effect, the masterbatch with high carbon black concentration is used, and the corresponding amount of addition is small, of course, saving money. For the equipment with limited mixing capacity, the masterbatch with high carbon black concentration is used, which is unevenly dispersed and has prominent pockmarks, resulting in a high rate of waste products. Perhaps the use of carbon black content 40% of the masterbatch when the production is not normal, use 35%, the effect is very good.

15. How about adding anti-aging agent to black masterbatch?

This is related to the storage and use of black masterbatch. Carbon black for plastics produced in China has the problem of high oxygen content, no matter high, medium or low pigment.