Table of Contents
What is calcium carbonate filler masterbatch？
A calcium carbonate filler masterbatch is made by mixing calcium carbonate and PP carrier. It is a kind of particle with a similar volume to the base resin of plastic products made by mixing granulating calcium carbonate and carrier resin. It has extensive application value in the plastic industry. The surface modification of calcium carbonate powder prior to the processing of the masterbatch can greatly improve the cross-linking with the resin by increasing its dispersion.
Application and Advantages
The main purpose of calcium carbonate filler masterbatch is to reduce production costs. Most of them are made of inorganic powder or industrial waste with low prices and extensive sources such as filling materials and adding appropriate additives and resins. Such as red mud+PVC, additives, etc., to produce flowerpot products. There are also glass beads screened from the industrial waste residue of thermal power plants, which can be used as filling materials for injection moulding products. While reducing production costs, they can significantly improve the rigidity and impact strength of products.
(1) Calcium carbonate filler masterbatch can reduce the cost of plastic products, improve production efficiency and obtain good economic benefits.
(2) Calcium carbonate filler masterbatch can enhance the rigidity of plastic products and increase the weight of products.
(3) Calcium carbonate filler masterbatch can reduce the shrinkage of plastic products and deformation caused by shrinkage.
(4) Calcium carbonate filler masterbatch has good dispersibility: it has good compatibility with polypropylene and polyethylene, so even if a large amount of filler is added, the appearance of a good surface finish can still be obtained.
(5) Calcium carbonate filler masterbatch has high whiteness and can be flexibly prepared to produce various color products.
(6) During the processing of calcium carbonate filler masterbatch, the use of coupling agents, dispersants and other treatments can make the calcium carbonate filler masterbatch maintain good mechanical properties when the filling amount is large.
Calcium carbonate is the core of the masterbatch, which determines the basic properties of the masterbatch. The content of calcium carbonate powder in calcium carbonate masterbatch is generally about 80-85% when produced by a twin screw extruder and about 88% when produced by the continuous internal mixer. There are many varieties of calcium carbonate, which can be divided into heavy calcium carbonate and light calcium carbonate, and heavy calcium carbonate can be divided into calcite calcium carbonate, marble calcium carbonate and dolomite calcium carbonate. Calcite calcium carbonate can be divided into calcite calcium carbonate and small calcite calcium carbonate. Considering the oil absorption value: the oil absorption value of light calcium carbonate is far greater than that of heavy calcium carbonate. If the formula contains liquid additives, heavy calcium carbonate should be selected. In terms of properties, light calcium carbonate is beneficial to impact strength modification, while heavy calcium carbonate contributes greatly to tensile strength. In terms of price, heavy calcium carbonate with the same particle size is about 30% cheaper than light calcium carbonate. Considering the filled resin: light calcium carbonate is preferred in PVC products. Because light calcium carbonate is more alkaline, it can timely absorb the decomposed acid HCl and improve the thermal stability in PVC processing.
The carrier resin should have good compatibility with the matrix resin
(1) Theoretically, in order to ensure the full compatibility of the carrier resin and the matrix resin, the same resin shall be selected as far as possible, such as PE for PE and PP for PP. However, sometimes the same resin cannot be selected, and only other resins with good compatibility can be selected. For example, PE chooses PP, POE, EVA and other resins with good compatibility, while PVC, PC, PET, PA and other resins often choose EVA with good compatibility as the carrier resin.
(2) The fluidity of carrier resin is higher than that of matrix resin
Theoretically, the fluidity of the carrier resin should be higher than that of the matrix resin, and the higher the better. Only in this way can the masterbatch have a good dispersion in the matrix resin. But in fact, the choice of the carrier should balance the dispersion and the strength of the filled composite. The greater the MI of the carrier resin, the better the dispersion of the masterbatch, but the lower the strength of the composite. Therefore, under the condition of ensuring dispersion, the smaller the MI of the carrier, the better.
(3) The melting temperature of the carrier resin shall be lower than that of the matrix resin
The melting temperature of the carrier resin shall be lower than or at least not higher than that of the matrix resin to ensure that the carrier resin is melted before the matrix resin is melted, which is conducive to the dispersion of inorganic powder in the masterbatch. Based on this principle, LDPE, LLDPE, HDPE, PP or blends can be used as carriers for PP and HDPE, while LLDPE and LDPE can only use LLDPE, LDPE or blends as carriers. Remember that HDPE and PP cannot be used as carriers for LDPE. That is to say, if HDPE is selected as the carrier, it cannot be used for LDPE and LLDPE matrix resin, but only for HDPE or PP matrix; If copolymerized PP is selected as the carrier, it can only be used for HDPE or PP matrix resin.
(4) It is better to choose a variety of resins to form a mixed carrier. Based on the above principles, calcium carbonate filler masterbatch carrier is mainly composed of LDPE, HDPE, LLDPE and PP with a high melt index. According to performance needs, the mixed-use of these carriers is often used to increase the functionality of the carrier, specifically LDPE/HDPE, HDPE/LLDPE, LDPE/LLDPE, PP/HDPE, etc. According to performance requirements, mLLDPE, POE, EVA, etc. can also be properly added. For example, mLLDPE can significantly increase the tensile strength, heat sealing strength and puncture resistance of the film, POE and EVA can significantly improve the impact strength of the film, and EVA and PCL can improve the heat sealing strength. Finally, it is better to choose powder resin, so that the particle size of powder resin and inorganic powder is close, and it is easier to mix evenly.
In addition to carrier resin and inorganic powder, additives that must be added to the formula include aluminate coupling agent, polymer wax dispersant, lubricant, etc.
The purpose of adding a coupling agent in the formula is to change the hydrophilicity of inorganic powder into lipophilicity, increase the compatibility with lipophilic resin, increase the thickness of the interface, improve the performance of filler materials or reduce the influence on the performance of filler materials.
Before coupling treatment, pay attention to the treatment condition of the purchased powder: if it has been treated with stearic acid, pay attention to using a titanate coupling agent for a different treatment, which will reduce the coupling effect; If the water-based grinding aid is added and treated with an oleophilic coupling agent, the amphiphilic function can be formed, and the treatment effect is good. For example, the oil absorption value of calcium carbonate can be reduced to 22%, the viscosity can be reduced by as much as 3 times, and the electron microscope picture shows that the interface thickness is significantly thickened. If the surface has not been treated, any method can be used for subsequent treatment. For whether a coupling agent is added to the formula, if the strength of composite materials with inorganic powder is not desired, it can also be considered not to add a coupling agent.
For calcium carbonate, the best coupling agent is aluminate, which is supplied by the powder itself, and the additional amount is about 1% of the powder. Another coupling agent that can be used is titanate, which has the same effect as aluminate. The disadvantage is that the product has a taste, and it is difficult to add the product’s liquid supply to the powder. Two coupling agents can also be added together to improve the effect.
The amount of coupling agent is generally controlled at about 1% of the powder. The finer the particle size, the larger the specific surface area and the amount of coupling agent should be increased accordingly. Calcium carbonate powder with a high oil absorption value will increase the coupling dosage to be treated. For example, if the oil absorption value of calcium carbonate increases from 40ml/100mg to 50ml/100mg, the amount of coupling agent will increase by 30%.
The function of a dispersant is to promote the uniform dispersion of powder in the substrate. Different dispersants are selected for different carriers. Waxes corresponding to carrier resins are mainly used, PE wax or PP wax is used for PE, PP wax is used for PP, oxidized polyethylene wax is used for medium polar resins such as PS and ABS, and EVA wax is used for polar resins such as PC, PET, PA, etc.
The quality of wax is mainly reflected in its molecular weight. It is best to have a molecular weight of about 5000, generally not less than 3000. The melting point of wax with normal quality is within the range of 110-120 ℃. If it is melted by adding 100 ℃ water, the wax is unqualified. The melting point of wax shall be higher than 110 ℃ to prevent the molecular weight of wax from being too low or doped with small molecular weight paraffin. However, 58-degree paraffin can also be added to low-grade products as a dispersant to ensure adequate lubrication for powder extrusion. However, a large amount of low-molecular-weight paraffin lubrication will affect the heat sealing strength and surface printing performance, increase the residue of film extrusion, and increase the volatile smoke of the die head.
Many lubricants, such as stearic acid and EBS, have dispersant effects to varying degrees. If the formula contains them, the amount of dispersant can be reduced. Disperse wax also has a certain role as an internal and external lubricant. If the formula contains dispersant wax, the amount of lubricant can be reduced. The dosage of the dispersant is related to the following factors:
Particle size: the larger the particle size is, the smaller the specific surface area is, and the easier it is to disperse. The added dispersion dose can be reduced. If the particle size is greater than 800 meshes, it can be considered not to add a dispersant.
The finer the particle size and the larger the specific surface area of the powder, the more difficult it is to disperse evenly, and the more dispersants need to be added.
Particle shape: the higher the spherical shape of calcium carbonate powder, the easier it is to disperse. The order of good and bad dispersion is a particle (marble calcium carbonate)>column (light calcium carbonate, calcite calcium carbonate). Therefore, the higher the spherical shape of calcium carbonate particles, the less the amount of dispersant.
Internal lubrication can reduce the friction between materials and promote the fluidity of materials; External lubrication can reduce the friction between materials and equipment, reduce the scratches on the surface of products, and ensure the surface brightness of masterbatch and filling products. During formula design, internal and external lubrication shall be used together to maintain the balance between internal and external lubrication. External lubrication mainly uses paraffin, stearic acid and EBS, while internal lubrication generally uses zinc stearate and calcium stearate. The dispersant polyethylene wax also plays the role of external lubricant, so the formulated lubricant with dispersant can be reduced. Compared with light calcium carbonate, the lubricant of heavy calcium carbonate can be added less. Because light calcium carbonate has a large oil absorption value and poor fluidity, it is necessary to add more internal and external lubricants. If considering the apparent brightness of the masterbatch, 1 part white oil or 1-2 parts paraffin can be added to improve the brightness of the product.
The amount of external lubricant added should include two parts: one is the amount of external lubricant required in the processing of masterbatch, and the other is the amount of external lubricant required in the subsequent processing of products such as films. However, if too much external lubricant is added, the printability and heat-sealing performance of film products will be affected.
It is better to add calcium/zinc composite stabilizer, but zinc stearate is generally added as a heat stabilizer due to price reasons, and it also acts as an internal lubricant. If the selling price of the product is acceptable, a small amount of calcium zinc stabilizer can also be added. Antioxidants can generally not be added unless the strength of filling products is required to be very high, or the products are required to be very white.
It can eliminate the static electricity of high speed mixed materials in time, and can also provide an anti-static effect for subsequent products.
Process of PE+calcium carbonate high-filling granulator
- Internal mixer mixing can achieve the best effect of uniform dispersion. The pressurized sealed mixing tank can not only ensure the unique quality of mixing, but also prevent the environmental pollution of carbon black dust.
- The dense material from the refiner is conveyed through the elevator and pour them into the Conical twin screw force feeder.
- The parallel co-rotating twin screw extruder is used as a mixing device. In the processing of polymer materials, various modification processes of polyolefin materials and engineering plastics, master batch preparation, etc. all need a strong mixing process. This mixing process is different according to the material system. Excellent equipment performance, reasonable mixing process, advanced combination process and rich processing experience are the keys to determining whether the mixing process is successful and effective. The low speed of the single screw extruder avoids the phenomenon of over-shearing, and the internal cooling system of the screw can avoid overheating and strong heat exchange capacity.
- The quick screen change of the hydraulic plate type automatic screen changer will not affect the normal operation of the machine.
- The Air cooling hot face system is suitable for the granulation of materials with low viscosity. The particles are smooth and beautiful.
Nanjing Cowin Extrusion Machinery Co., Ld is a high-tech enterprise specializing in the technology development and production of polymer blending modification equipment with co-rotating twin screw extruders as the core, as well as related process and engineering fields. Keeping pace with the international in technical development and innovation. Nanjing Cowin is promoting the development of China’s national brand of plastic machinery with CHT series high-speed high torque co-rotating twin screw extruder. Cowin’s characteristic fields are formed by the micro blending of polymers, long fiber reinforced LFRT underwater pelleting, etc, which have always been in the leading position in China. In addition to twin screw extruders, we also have various types of triple screw extruders, which have better dispersion effects and can replace internal mixers. In addition, such processes as calcium carbonate filler masterbatch have wide applicability. Customers can use the original processing equipment and production process to produce.
Recommended Caco3 Filler Masterbatch Extruders
The machine model is mainly determined according to the customer’s output. The L/D of the twin screw extruder is the higher the better. It is usually required to be more than 40 with a high cost-performance ratio. Generally, the 52mm, 65mm, and 75mm twin screw extruders are more popular with customers. The triple screw extruders of 52mm, 65mm and 75mm have a higher output and better mixing effect than the twin screw extruders of the same model.
If the polyethylene resin is used as the carrier resin, the Air cooling hot face-cutting process is suitable. When the diameter of the extruder is large (such as a diameter above 72mm) and the output is higher than 300kg/h, the head of Air cooling hot face cutting is difficult to do well, and the temperature is not easy to control, the particles are not cooled down and are easy to stick together. At this time, it is appropriate to use the way of conveyor cooling, and this way is adapted to the production of various filler masterbatches or modified special materials.