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With China Plastic Machinery
With China Plastic Machinery
During the plastic processing and molding process, the required various additives, fillers and a small amount of carrier resin are mixed to obtain granules, which are composed of three parts: carrier resin, fillers and various additives. The performance and cost mainly depend on the carrier resin.
Filling masterbatch refers to the granules and powders obtained by mixing and kneading the required various additives, fillers and a small amount of carrier resin in the process of plastic processing and molding for the convenience of operation.
Masterbatch is composed of carrier resin, fillers and various additives. The limit of additives or the content of fillers in the masterbatch is several to ten times higher than the required amount in the actual plastic product. During the molding process, the ratio of masterbatch to base resin must be adjusted according to the content of relevant components in the masterbatch and the amount required to be added in the actual product. Masterbatch can usually be divided into ordinary filling masterbatch (referred to as filling masterbatch) and functional masterbatch, such as color masterbatch, anti-drip masterbatch, etc. The main component of the filling masterbatch is filler, which is mainly used for the processing and molding of polyolefins (polyethylene and polypropylene), also known as polyolefin filling masterbatch.
Polyolefin filling masterbatch is composed of three parts: carrier resin, filler and various additives, among which filler accounts for the main component, up to 90%. Polyolefin filling masterbatch is mainly used in the production of polyolefin plastics such as polyethylene and polypropylene. Such as: polyethylene hollow blow molding products, polyethylene injection molding products and polyethylene films, polypropylene woven bags, woven cloth and packing tapes, etc. Generally, when selecting the raw and auxiliary materials of olefin filling masterbatch, it is necessary to consider its good performance and low cost.
The filler used in polyolefin filling masterbatch is mainly heavy calcium carbonate, followed by inorganic fillers such as talcum powder, kaolin, and calcium powder. For any inorganic filler, particle size and particle size distribution are important technical indicators. Generally, the smaller the particle size and the narrower the distribution, the better the filling effect. In addition, the filling effect is also related to the dispersibility. The smaller the particle size, the more difficult it is to disperse and the higher the price. Purity is another important technical indicator of inorganic fillers. The less impurities and the higher the purity, the better. When heavy calcium carbonate is generally selected, its content and whiteness should be as high as possible, generally required to be above 94%. After ensuring that other indicators meet the requirements, the price should be low to help reduce the cost of the masterbatch.
The performance and cost of polyolefin filler masterbatch mainly depend on the carrier resin. Usually, depending on the purpose of the masterbatch, the carrier resin generally contains 10%~20%. The carrier resin used in polyolefin filler masterbatch should have good compatibility with the plastic matrix resin filled. From this aspect, it is generally best to use the matrix resin as the carrier resin. In addition, when selecting the filler masterbatch carrier, its melting point and melt fluidity must also be considered. The melting point of the carrier resin must not be higher than that of the matrix resin. At present, some companies still use LDPE (1F7B) as a carrier resin, mainly because this grade of resin has a low melting point and a high melt flow rate (7g/10min). However, due to the high melting temperature of polypropylene (20~40¡æ higher than general polyethylene), it is limited to its use in polyethylene plastics, while the melting point of random polypropylene or powdered polypropylene synthesized by liquid phase bulk method does not exceed 100¡æ, so it is widely used as a carrier of polyolefin filling masterbatch.
The biggest advantage of using LDPE (1F7B) as a polyolefin filling matrix carrier resin is its low melting point, high melt flow rate, and high melt strength, but the prominent disadvantage is its high price. If low-cost low-density polyethylene resin with low melt flow rate, such as 1I2A-1 or 2F2B, is selected, due to their low melt flow rate, generally about 2g/10min, more paraffin and other additives need to be added during processing to facilitate better dispersion of the masterbatch in the matrix resin. Filling masterbatch usually made with polyethylene as a carrier is more suitable for polyethylene plastic products, mainly because the carrier resin has the same performance as the matrix resin and has good compatibility. Filling masterbatch used for polyethylene film has higher and stricter requirements on the carrier resin.
For the filler masterbatch used in polypropylene products, its carrier resin is preferably polypropylene. Theoretically, random polypropylene is the best because it has a low melting point, good melt fluidity and good dispersibility. But specifically in China's national conditions, it is more appropriate to choose powdered polypropylene synthesized by the liquid phase bulk method, because it is cheap, it is in powder form, and it is very easy to mix evenly with inorganic fillers, and it will not stratify even in the hopper. When using polypropylene as a carrier, antioxidants and lubricants must be added at the same time due to the poor thermal stability of polypropylene. In order to make the additives that only account for a few thousandths of the total resin evenly distributed in the resin, it is best to first mix the resin with various additives, and then mix them with fillers in a certain proportion to granulate.
For wide use, polypropylene and polyethylene with similar melt indexes can be selected and mixed in a certain proportion as carrier resins. In this way, the masterbatch can be used in combination with polyethylene to improve some properties, and the elongation can be improved when combined with polypropylene.
Recycled polystyrene is widely used in the manufacturing process of synthetic leather. Even if the compatibility between the carrier resin and the matrix resin is not good enough, the influence of the carrier resin on the performance of plastic products is far less than that of the filler, which can bring considerable economic benefits. When using other resins as carriers to make filling masterbatch, in order to improve the processing fluidity of the filling masterbatch and the dispersibility in the matrix resin, a small amount of recycled polystyrene is often added.
Since the production cost of the filling masterbatch mainly depends on the carrier resin, and because the content of the carrier resin in the masterbatch is relatively small, it has little effect on the performance of general filled and modified plastic products. In order to reduce the cost of the masterbatch, scraps of waste polyethylene, polypropylene plastics or polyethylene-polypropylene composite films are often used as carriers.
The additives used in polyolefin filling masterbatch are mainly dispersants and surface treatment agents. The role of the dispersant is to improve the processing fluidity of the masterbatch, which is conducive to a more uniform dispersion of the masterbatch in the matrix resin. Commonly used dispersants include: white oil (liquid paraffin), paraffin, dioctyl phthalate (BOP), low molecular weight polyethylene (polyethylene wax) and stearic acid. The main properties of commonly used dispersants can be selected according to the performance characteristics of fillers and carrier resins. Surface treatment agents can change the surface activity of inorganic fillers, converting them from hydrophilic to lipophilic, so as to facilitate mixing with carrier resins. There are mainly two types of coupling agents and stearic acid. In order to make the product more dispersible and brighter, EBS and flow modifiers can be added.
The processing technology and related equipment of polyolefin filler masterbatch have also changed with the continuous change of carrier resin.
The carrier resin used in the first generation of polyolefin filler masterbatch (APP masterbatch) is domestic random polypropylene (actually a by-product of polypropylene production). The processing technology is: mixing-open refining and drawing-water cooling pelletizing. It is intermittent production. The equipment used includes internal mixer, open mixer and flat pelletizer.
The second generation of polyolefin filler masterbatch uses LDPE (1F7B) as the carrier resin, and the masterbatch produced is called PEP masterbatch. This process must use a specially designed single-screw extruder with a large aspect ratio and high mixing performance to achieve better results.
The filler masterbatch with polypropylene powder as the carrier, that is, PPM masterbatch, is called China's third generation filler masterbatch. Generally, the method of using polypropylene and polyethylene blends as carrier resins will have a good effect. The product not only maintains the characteristics and scope of use of PPM masterbatch, but also can use the die surface hot cutting air cooling process, which improves production efficiency and reduces raw material costs.
The best processing equipment for making filler masterbatch is a co-rotating twin-screw extruder. The advantages of this machine are continuous production, stable quality, high production efficiency, low energy consumption, low labor intensity of workers, and good operating environment.
The concentration of fillers and additives in the filler masterbatch is high. When used, a certain amount of base resin must be added and mixed before processing and molding. The filler mainly plays a filling role. Fillers and additives can give plastic products special functions, such as light, electricity, flame retardancy, degradation, etc., which are called functional filler masterbatches. Functional masterbatches usually include color masterbatches, photoconversion masterbatches, high-efficiency thermal insulation film masterbatches, anti-drip masterbatches and degradation masterbatches.
Color masterbatch is a special granular material for coloring plastic products. It can be divided into polyolefins, ABS, PS and AS according to the type of plastic to be colored. The production process of color masterbatch is usually divided into two steps: the first step is to prepare the pigment pre-dispersion, that is, to treat the pigment surface with a dispersant or other additives; the second step is to mix the pigment pre-dispersion with the carrier resin and granulate to obtain the color masterbatch. The color masterbatch is composed of pigment, dispersant, carrier resin and appropriate additives. The main function of the dispersant is to fully disperse the pigment and evenly disperse it in the carrier resin and the matrix resin, so as to finally obtain a plastic product with uniform color. The carrier resin used for masterbatch should first have good compatibility with the resin to be colored, and secondly, the fluidity of the carrier resin should be greater than that of the colored resin so that the pigment can be better dispersed. The composition of the masterbatch, the selection of pigments and the dosage depend on the properties of the plastic to be colored. The content of pigments in the masterbatch used for coloring polyolefin plastics is usually 20%~40% (mass fraction).
Filling masterbatch can be used to process plastic films, garbage bags, shopping bags, vest bags, packaging bags, etc. It has good dispersibility, no white spots and black spots in the blown film, high fineness, and ensures the gloss and toughness of the products. It is mainly suitable for filling and modification of woven bags, strapping tapes, hollow products, pipes, sheets, injection molded products and plastic fast food boxes, which can improve the performance of plastic products and reduce product costs.
Directly mix this masterbatch with the damp plastic raw material and evenly, and then the product processing and production can be carried out.
For blow molding and wire drawing production, the addition ratio is 1.0~3.0%
For sheet and injection molding production, the addition ratio is 2.~5%
The specific addition ratio can be determined by the user according to the moisture condition of the plastic.
1. Avoid moisture absorption before use. Use immediately after mixing for the best effect
2. Do not heat and dry together with damp plastics to avoid product quality defects
3. Before opening the package, check whether the package is intact, and heat-seal the unused masterbatch as soon as possible
4. The masterbatch package is not allowed to be damaged or stored openly to avoid exposure to sunlight and rain.
5. Before purchasing in large quantities, be sure to conduct a small test to determine whether the compatibility and other indicators meet the production requirements.
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