Main technical indicators of white masterbatch
The production of protective film is inseparable from the plastic masterbatch. Today we will talk about the most commonly used plastic masterbatch in the production of protective film: white masterbatch has bright color, bright and eye-catching, high color strength, good dispersion, high concentration, It is widely used in injection molding, blow molding, wire drawing, casting, extrusion, blown film, foaming, sheet, pipe, pumping, etc., with good whiteness, strong hiding power, good migration resistance and heat resistance. Hollow, EVA, blown bottles, sheets, household appliances, toys, packaging materials, wires and cables, plastic bags, automobiles, building materials, sports and leisure products, packaging bags, packaging bottles and other plastic products industry.
Main technical indicators of white masterbatch
1, resistance to migration (grade) [≥ 4]
2, the moisture content (%) [≤ 0.30] 8, the total color difference [≤ 1.50]
3, melting temperature (oC) [125 ~ 200]
4, white masterbatch dispersibility: [colorless dots, stripes]
5, lightfastness (level) [5-8]
6, white masterbatch appearance granular, uniform particles, uniform color
7, heat resistance (grade) [≥4]
In theory, the white masterbatch that meets the above technical specifications is of good quality.
10 aspects to consider when choosing a white masterbatch
1, whiteness
The whiteness of the white masterbatch is mainly represented by the titanium dioxide in the masterbatch. There are many factors that affect the whiteness of titanium dioxide, including the size, shape and size distribution of titanium dioxide particles, the type and content of impurities, and the lattice of titanium dioxide particles. Defects. In general, since the chlorination method has high purity of titanium dioxide as a raw material and less impurities in the preparation process, the whiteness of the chlorination titanium dioxide is better than that of the sulfuric acid method. In the actual white mother market, many white masterbatch manufacturers impersonate titanium dioxide by adding equal amounts of calcium carbonate, barium sulfate, and zinc sulfide. In fact, the whiteness of these inorganic powders is incomparable with titanium dioxide. .
2, hiding power
Hiding power is also a very important indicator of white masterbatch. Good hiding power means that the pigment has strong coloring ability, and the desired effect can be obtained with a small amount of additive. The hiding power of the white masterbatch depends on the choice of titanium dioxide. Compared with the processing technology, rutile titanium dioxide has a smaller and tighter unit lattice and a larger refractive index than rutile titanium dioxide, so the hiding power and anti-ultraviolet light performance are obviously better than anatase. For the same type of rutile titanium dioxide white masterbatch, titanium dioxide particle size is small, narrow particle size distribution, good hiding power in the masterbatch is significantly larger than the titanium dioxide particle size distribution, poor performance in the masterbatch it is good. Similarly, the common hiding power of calcium carbonate, barium sulfate, and zinc sulfide is not comparable to titanium dioxide.
Table 1 Refractive index of different substances
From the above comparison of the refractive index, it can be known that the refractive index difference between the rutile titanium dioxide and the carrier PE resin is the largest, and the dispersion effect is the best, and the hiding power is the strongest.
3, dispersion
Dispersibility has an important influence on the application of titanium dioxide in plastics. In general, the finer the titanium dioxide particles, the better the dispersion, the higher the strength of the tinctorial force, and the fine dispersion of the white masterbatch when the film needs to be finely printed. Grain pattern clarity, layering, and vividness are better because the microscopic smoothness of the base film is one of the determinants of the quality of the printed pattern.
4, moisture content
The moisture content of the white masterbatch also plays an important role in the performance of the masterbatch. In general, the moisture content should be controlled below 1500ppm, and the strict requirements should be below 600ppm. In the injection molding process, the raw materials are generally dried before production. In the production of thin films, customers buy directly after being premixed with the carrier. If the moisture content of the masterbatch is high, it will directly lead to film rupture, and there will be small bubbles formed on the film, “crystal point”. Defects, and cause the high moisture content of white masterbatch from the raw material used in the masterbatch to the process have an impact.
5, smell
Some film manufacturers will smell a strange odor after using white masterbatch, which is absolutely not allowed in the milk film and film that comes into contact with food. This is mainly due to the fact that the titanium dioxide in the masterbatch is organic. During the treatment process, the coating auxiliaries selected are not suitable or the amount added is too large, or there is a problem with the dispersant used in the production process of the masterbatch, and the white masterbatch grade can be replaced.
6, Hue selection
Due to the low reflectivity of the rutile titanium dioxide in the violet region, the rutile titanium dioxide has a “yellowish” color tone, and the “yellowish” color tone will give the colored product a “stale” feeling and will make the fine print image vivid. Decrease in the degree and layering, which is unwelcome among many white masterbatch users, but after adding a trace of fluorescent whitening agent to titanium dioxide, it can absorb ultraviolet light with a wavelength of 300-400nm and convert it to a wavelength of 400 – 500nm blue fluorescence, so that white masterbatch was “blue phase”, white masterbatch users according to their needs.
7, liquidity
The fluidity of the white masterbatch can be expressed as the melt index (MI), low numerical flow, high numerical fluidity, good fluidity means good processing performance, low machine torque, low power consumption, and the user selects white masterbatch In addition to requiring the masterbatch to have good fluidity, it is also important to note that the masterbatch should be compatible with the carrier resin in its own factory product. The general principle is that the MI of the masterbatch should be higher than that of the carrier resin.
8, printing heat sealing performance
White film products require printing and heat sealing in most cases. Addition of calcium carbonate in the white masterbatch can affect the sharpness and vividness of the printed pattern. Incorrect or excessive amount of dispersant added to the masterbatch can also affect the heat seal and Printing performance.
9, lightfastness and weatherability
White masterbatch generally requires lightfastness of 7-8 grades, weather resistance of 4-5, and temperature resistance of 280 degrees. These requirements mainly depend on the quality of titanium dioxide. To achieve the above conditions, it must be rutile titanium dioxide. .
10, RoHS & FDA
Heavy metal detection and food contact permitting are also important indicators for white masterbatch, because many white films are used in food packaging. Passing FDA food certification is a test that must be passed.
Precautions when using white masterbatch
1, in order to reduce the color after the fiber color difference, the white masterbatch should be diluted to control the mixing ratio, filaments not less than 3% to 10%, staple fiber not less than 1% to 3%, monochrome monofilament continuous filament Spinning with three-color equipment, the white masterbatch must be fed into the extruder after mixing. At the same time, to increase the mixing capacity of the melt itself, a mixing device can be added to the extruder section.
2. White masterbatch mixing method After the color silk color formula is determined, the white masterbatch is evenly dispersed in the polypropylene slice before spinning, which is the key to ensure the product quality. There are two specific mixing methods. One is the heavy method and volume method. After the white masterbatch is melted in the extruder or at the back, it is injected into the polypropylene melt with a small extruder, and the uniformity is very good.
3. When choosing the white masterbatch, choose according to the selection range. The polypropylene masterbatch has the fine denier grade and the coarse denier grade. The coarse masterbatch white masterbatch color can not be used for fine denier grades, and the color should be considered when spinning For the denier of the monofilament of the fiber, the same level of white masterbatch was selected.
4, the choice of white masterbatch is preferably the same manufacturer’s products, in order to reduce costs should be selected high concentration white masterbatch. Pigments for white masterbatch have high, middle and low grades. When matching colors, white masterbatch of different grades should be properly selected according to the quality requirements of the fiber. In order to avoid the quality variation of the finished fiber caused by the different light and thermal stability of the pigment, the color of the white masterbatch that meets the fiber quality requirements and has the same level of light and heat stability should also be selected.