Calcium carbonate, as the first inorganic powder material, can cause dust flying when directly used in plastics and seriously damage the production environment. At the same time, since it is a hydrophilic material, the dispersibility is not good when being added in lipophilic resin directly, so for the calcium carbonate powder, it is generally necessary to process it into a masterbatch in advance to provide it to the customer, which can solve the production environment and compatibility issues. The calcium carbonate masterbatch is generally composed of carrier resin, calcium carbonate powder, dispersant, coupling agent, lubricant, antistatic agent, antioxidant, etc. The specific selection of each component is as follow:
1, the choosing of calcium carbonate
Calcium carbonate is the core of the masterbatch and it determines the basic properties of the masterbatch. The content of calcium carbonate powder in the calcium carbonate masterbatch is generally about 80% when using a twin-screw extruder to produce, and about 88% when using a continuous mixer. There are many varieties of calcium carbonate, which can be divided into heavy calcium carbonate and light calcium carbonate. The heavy calcium carbonate can be divided into calcite calcium carbonate, marble calcium carbonate and dolomite calcium carbonate, and calcite calcium carbonate can be divided into large calcite calcium carbonate and small calcite calcium carbonate.
How to choose heavy calcium carbonate and light calcium carbonate in the specific design formula?
Consider from the oil absorption value: The light oil calcium carbonate's oil absorption value is far greater than the heavy calcium carbonate, if the formula contains the liquid additive, should use the heavy calcium carbonate. From the performance point of view: light calcium carbonate is beneficial to the modification of impact strength, while heavy calcium carbonate has a great contribution to tensile strength. From the price point of view: Heavy calcium carbonate is about 30% cheaper than light calcium carbonate with the same size. Considered from the filled resin, light calcium carbonate is preferred in PVC products, because light calcium carbonate has stronger alkalinity and can absorb the decomposed acid HCl in time to improve the thermal stability in PVC processing.
2, the choosing of carrier resin The basic principles for choosing calcium carbonate masterbatch resins are as follow:
(1) The carrier resin must have good compatibility with the matrix resin
Theoretically, in order to ensure the full compatibility of the carrier resin and the matrix resin, select the same resin as possible, for example,select PE for PE, and select PP for PP. However, sometimes can not choose the same resin, only have to choose other resins with good compatibility, for PE choose PP, POE, EVA and other compatible resins, PVC, PC, PET, PA often choose good compatibility EVA as carrier resin.
(2) The carrier resin has higher fluidity than the matrix resin
Theoretically, the flowability of the carrier resin is higher than that of the matrix resin, and the higher the number is, the better, and only in this way can ensure the masterbatch have a good dispersibility in the matrix resin. However, in practice, the choosing of the carrier must be selected in the balance between the dispersibility and the strength of the filled composite material. The greater the MI of the carrier resin, the better the dispersibility of the masterbatch, but the lower the strength of the composite product is. Therefore, under the condition of guaranteeing dispersion, the smaller the MI of the carrier, the better. For example, for the pipe filling masterbatch MI, select a resin close to the matrix resin; For the carrier of the non-woven masterbatch, the copolymer PP is selected, and is close to the technical index and MI of the non-woven fabric material, so that the strength can be ensured. Under normal conditions, the MI of the carrier resin is preferably greater than 10 g/10 min or more of the matrix resin.
(3) The melting temperature of the carrier resin is lower than that of the matrix resin
The melting temperature of the carrier resin is lower than that of the matrix resin, and at least cannot be higher than the matrix resin, so as to ensure that the carrier resin is melted before the matrix resin is melted, and this facilitates the dispersion of the inorganic powder in the masterbatch. Based on this principle, PP and HDPE can use LDPE, LLDPE, HDPE, PP or blends as carrier. LLDPE and LDPE can only use LLDPE, LDPE or blends as carrier. Remember that LDPE cannot use HDPE and PP as carrier. In other words, if HDPE is selected as the carrier, it cannot be used in LDPE and LLDPE matrix resins, and it can only be used in HDPE or PP matrix; if the copolymer PP is used as the carrier, it can only be used for HDPE or PP matrix resin.
(4) It is best to choose a variety of resin composition mixed carrier
Based on the above principles, the calcium carbonate filled masterbatch carrier is mainly composed of LDPE, HDPE, LLDPE and PP with high melting index. According to the performance requirements, these carriers are often used in combination to increase the functionality of the carrier, such as LDPE/HDPE, HDPE/LLDPE, LDPE/LLDPE, and PP/HDPE. According to performance needs, can also add mLLDPE, POE, EVA and so on. mLLDPE can significantly increase the film's tensile strength, heat seal strength and puncture resistance, POE, EVA can significantly improve the impact strength of the film, EVA, PCL can improve the heat seal strength. Finally, it is best to choose a powder resin, so that the powder resin and inorganic powder particles are close in size and easier to mix.
3, the choosing of additives
In addition to the carrier resin and inorganic powder, additives that must be added to the formulation include aluminate coupling agents, polymer wax dispersants, lubricants, and the like. In general, the finer the inorganic powder, the above-mentioned addition amount is relatively increased.
Calcium Carbonate plastic filler masterbatch
Ivy Lee Overseas Sales
Qingyun Xinyang New Materials Co., Ltd South 600 meters of Zhengjia Village, Changjia Town, Qingyun County, Dezhou, Shandong, P.R.China