At present, some plastic manufacturers widely use “color masterbatches”, also known as masterbatch or masterbatch. Color masterbatches are fluorescent brighteners or pigments mixed with the required resin or plastic, directly melted and extruded to form coloring products containing a high concentration of fluorescent brighteners or pigments, which can be used directly and have become a major means of coloring and whitening plastics.
When using masterbatches, as long as the masterbatches and resin are mixed in proportion, they can be used directly for molding plastic products. A small amount of mixing is done by hand only, but in case of large quantity, mechanical mixing can be used to ensure the dispersion of the masterbatch. After mixing the masterbatches and resin, they can be sent to the injection molding machine with a pre-molding device to be colored while pre-molding.
Generally speaking, the mixing ratio between masterbatch and resin is wide, ranging from 1:10 to 1:100. It mainly depends on the content of the fluorescent whitening agent in the masterbatch and the flowability of the plastic.
For the same injection molding equipment, the operation and selection of the ratio can be used as a reference for the process. Good mixing of plastic, the ratio can be smaller, poor mixing of masterbatch ratio can be enlarged, and pay attention to the process.
The control of the injection molding machine screw is the key to make the masterbatch dispersion uniform. The screw is generally divided into three sections: feeding section, compression section, and metering section. In order to make the masterbatch enter the barrel as soon as possible after melting, so as to mix evenly with the plastic, when using the masterbatch, you need to increase the temperature of the feeding section, so that it is close to the temperature of the compression section or slightly higher. If the temperature of the feeding section is too low, the masterbatch will be melted only in the compression section and the pre-molding time will be relatively shortened, which will easily cause uneven coloring and streaking of the product.
When using masterbatch injection molding, it is necessary to apply a certain amount of backpressure to improve the mixing effect of the screw and make the masterbatch spread more evenly. The strength of the backpressure depends on the actual effect of different equipment.
As the amount of fluorescent whitening agent is very small, the masterbatch used only needs to be measured accurately, take a certain amount of its use before mixing into the plastic molding of the material that is to achieve the purpose of color whitening, quite convenient. It is very convenient and reduces dust, which greatly improves the working environment and is loved by many manufacturers. The plastics that can be colored by this method include PVC, polyethylene, polypropylene, and so on. It is suitable for injection molding, extruded tube, extruded film, wire wrapping, hollow molded products, or sheet materials that are generally mixed and assembled.