In the process of plastic processing and molding, the required various additives, fillers and a small amount of carrier resin are mixed to obtain pellets, which are composed of carrier resin, fillers and various additives. The performance and cost mainly depend on the carrier resin.

Masterbatch Overview

Filler masterbatch refers to the plastic processing and molding process, in order to facilitate the operation, the required various additives, fillers and a small amount of carrier resin first mixed and kneaded, the resulting granules, powder called masterbatch.

Filler masterbatch masterbatch is composed of carrier resin, filler and various additives. The limit of additives in the masterbatch or the content of fillers is several times to ten times higher than the required amount in the actual plastic products. During the molding process, the ratio of the masterbatch to the matrix resin must be adjusted according to the content of the relevant components in the masterbatch and the amount that needs to be added in the actual product. Masterbatches can usually be divided into ordinary filling masterbatch (referred to as filling masterbatch) and functional masterbatch, such as color masterbatch, anti-fog masterbatch, etc. The main component of the filling masterbatch is the filler, which is mainly used for the processing and molding of polyolefins (polyethylene and polypropylene), also known as polyolefin filling masterbatch.

raw and auxiliary materials

Polyolefin filler masterbatch is composed of three parts: carrier resin, filler and various additives, of which filler accounts for the main component, up to 90%. Polyolefin filler masterbatch is mainly used in the production of polyethylene, polypropylene and other polyolefin plastics. Such as: polyethylene hollow blow molding products, polyethylene injection molding products and polyethylene film, polypropylene woven bags, woven cloth and packing belt. Generally, when selecting the raw and auxiliary materials of olefin filler masterbatch, it is necessary to consider its good performance and low cost.

Packing

The filler used in polyolefin filling masterbatch is mainly heavy calcium carbonate, followed by talc, kaolin, calcium powder and other inorganic fillers. 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 dispersion, the smaller the particle size, the more difficult to disperse, the higher the price. Purity is another important technical index of inorganic filler. The lower the impurity content, the higher the purity, the better. Generally, when heavy calcium carbonate is selected, its content and whiteness should be as high as possible, and the general requirement is more than 94%. Ensure that other indicators meet the requirements, the price should be low, in order to help reduce the cost of masterbatch.

carrier resin

The performance and cost of the polyolefin filling masterbatch mainly depend on the carrier resin. Generally, depending on the use of the masterbatch, the carrier resin generally contains 10% to 20%. The carrier resin used in the polyolefin filler masterbatch should have good compatibility with the plastic matrix resin to be filled. From this point of view, the general carrier resin is preferably selected matrix resin. In addition, the choice of filled masterbatch carrier, but also consider its melting point and melt flow, the melting point of the carrier resin should not be higher than the matrix resin. There are still some enterprises still use LDPE(1F7B) as the carrier resin, which is mainly due to the low melting point of this brand of resin, high melt flow rate (7g/10min). However, due to the high melting temperature of polypropylene (20~40 ℃ higher than that of general polyethylene), its use in polyethylene plastics is limited, and the melting point of random polypropylene or powdery polypropylene synthesized by liquid bulk method does not exceed 100 ℃, so it is widely used as the carrier of polyolefin filling masterbatch.

The biggest advantage of using LDPE(1F7B) as a polyolefin-filled parent carrier resin is low melting point, high melt flow rate and high melt strength, but the outstanding disadvantage is high price. If the low-density polyethylene resin with low cost and low melt flow rate is selected, such as 1I2A-1 or 2F2B, due to their low melt flow rate, generally about 2g/10min, it is necessary to add more additives such as paraffin wax during processing to facilitate better dispersion of the masterbatch in the matrix resin. The filler masterbatch usually made with polyethylene as the carrier is more suitable for polyethylene plastic products, mainly because the carrier resin and the matrix resin have the same performance and good compatibility. The filler masterbatch used for polyethylene film has higher and stricter requirements on the carrier resin.

For polypropylene products filling masterbatch, the carrier resin is preferably selected from polypropylene. Theoretically, atactic polypropylene is preferred because of its low melting point, good melt fluidity and good dispersibility. However, specific to China's national conditions, the choice of liquid phase bulk synthesis of powdered polypropylene is more appropriate, because of its low price, itself is powdered, easily mixed with inorganic filler evenly, even in the hopper will not be stratified. Using polypropylene as a carrier, due to the poor thermal stability of polypropylene, it is necessary to add antioxidants and lubricants at the same time. In order to make only a few thousandths of the total amount of resin additives can be evenly distributed in the resin, it is best to first resin and various additives mixed evenly, and then according to a certain proportion of filler mixing granulation.

In order to use a wide range, you can choose a similar melt index of polypropylene and polyethylene according to a certain proportion of the carrier resin, so that the masterbatch and polyethylene can also improve some performance, and polypropylene can improve the elongation.

Recycled polystyrene is widely used in synthetic leather manufacturing process, even if the carrier resin and matrix resin compatibility is not good enough, but the carrier resin on the performance of plastic products is far less than the impact of filler, can bring considerable economic benefits. When other resins are used as carriers to make a filler masterbatch, a small amount of recycled polystyrene is often added in order to improve the processing fluidity of the filler masterbatch and the dispersibility in the matrix resin.

Because 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 less, it has little effect on the performance of the general filling modified plastic products. In order to reduce the cost of the masterbatch, the scrap of polyethylene, polypropylene plastic or polyethylene-polypropylene composite film is often used as the carrier.

Auxiliaries

The additives used in polyolefin filler masterbatch are mainly dispersants and surface treatment agents. The function of the dispersant is to improve the processing fluidity of the masterbatch, which is beneficial to the more uniform dispersion of the masterbatch in the matrix resin. Commonly used dispersants are: 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 agent can change the surface activity of inorganic fillers, so that it is converted from hydrophilic to lipophilic, so as to facilitate mixing with carrier resin, mainly including coupling agent and stearic acid. EBS, flow modifier, etc. can be added for better product dispersion and brighter.

Processing technology

Polyolefin filling masterbatch processing technology and related equipment with the carrier resin changes.

The carrier resin used in the first generation of polyolefin filling masterbatch (APP masterbatch) is domestic random polypropylene (actually a by-product of the production of polypropylene), the processing process is: mixing-open refining pull-water-cooled pelletizing, for intermittent production, the use of equipment with internal mixer, open mill and flat pelletizer.

The second generation polyolefin filler masterbatch is LDPE(1F7B) as the carrier resin, and the masterbatch produced is called PEP masterbatch. In order to obtain better effect, a specially designed single screw extruder with large aspect ratio and high mixing performance must be used in the process.

The filler masterbatch with polypropylene powder as the carrier, that is, PPM masterbatch, is called the third generation of filler masterbatch in China. The general use of polypropylene and polyethylene blends as a carrier resin approach, the effect will be very good. The product not only maintains the characteristics and scope of use of PPM masterbatch, but also adopts the hot air cooling process of the mold surface, which improves the production efficiency and reduces the cost of raw materials.

The best processing equipment for making the filled 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 and good operating environment.

The concentration of filler and additives in the filler masterbatch is large, and a certain amount of matrix resin must be added during use. After mixing, the filler mainly plays a filling role. Fillers and additives can give plastic products special functions, such as: light, electricity, flame retardant, degradation, etc., called functional filling masterbatch. Functional masterbatch usually includes color masterbatch, light conversion masterbatch, high-efficiency insulation film masterbatch, anti-fog masterbatch and degradation masterbatch.

Color masterbatch is a special pellet for coloring plastic products. It can be divided into polyolefin, ABS, PS and AS according to the colored plastic varieties. The production process of the color masterbatch is usually divided into two steps: the first step is to prepare the pigment pre-dispersion, that is, the surface treatment of the pigment with a dispersant or other additives; the second step is to mix the pigment pre-dispersion with the carrier resin to obtain the color masterbatch. Color masterbatch is composed of pigment, dispersant, carrier resin and appropriate amount of additives. The main function of the dispersant is to fully disperse the pigment and uniformly disperse it in the carrier resin and the matrix resin, and finally obtain a plastic product with uniform color. The carrier resin used for the color masterbatch should first have good compatibility with the colored resin, 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 color masterbatch, the selection and amount of the pigment depend on the nature of the colored plastic, and the content of the pigment in the color masterbatch usually used for the coloring of polyolefin plastics is 20% to 40% (mass fraction).

Application areas

Filling masterbatch can be used for processing plastic film, garbage bags, shopping bags, vest bags, packaging bags, etc., good dispersion, blown film without white and black spots, high fineness, guarantee product gloss and toughness. It is mainly suitable for filling modification of woven bags, packing belts, hollow products, pipes, sheets, injection molded products and plastic snack boxes, which can improve the performance of plastic products and reduce product costs.

Method of use

The masterbatch and damp plastic raw materials are directly mixed evenly, and the products can be processed and produced.

For blow drawing production, adding ratio of 1.0~3.0%

For sheet and injection molding production, adding ratio of 2.~ 5%

The specific addition ratio, the user can be based on the plastic moisture situation discretion.

Precautions

1. Avoid moisture absorption before use, that is, the ingredients are used, the best effect

2, shall not be heated and dried together with damp plastic, so as not to cause product quality defects

3. Before opening the package, check whether the package is in good condition, and heat seal the unused masterbatch as soon as possible

4, do not allow the masterbatch packaging damage and open storage, to avoid sun exposure, rain.

5. Before purchasing in large quantities, we must make a small test to determine the compatibility and other indicators to meet the production requirements.