From the technical point of view, the analysis of the reasons and the solutions to the problems mainly include:

• Because carbon black is difficult to disperse, it is very difficult tomake the content of carbon black reaches more than 30% if produce color masterbatch with ordinary twin-screw extruder. The method of granulating twice can be adopted, and carbon black can be added in batches;
• The dry method of making carbon black masterbatch does have pollution problems. If conditions permit, it can be made with an internal mixer, which is environmentally friendly, and the carbon black content can reach 50%;
• Eager cutting methodcan be considered , there will be no problem of broken strips.

Ways to solve the problems from a formula point of view are:

• Use base materials with high fluidity ;
• Compounding of polymer dispersant and common dispersant;
• Use black pulp for production, and the dust will be much less.

The reasons are as follows:

• It may be a blending problem, such as uneven mixing, poor dispersion, or compatibility.
• The following solutions are provided for this problem:

1. Dry the material thoroughly;
2. Adjust the appropriate co-extrusion temperature;
3. The extruded ASA layer should not be too thin;
4. The operation method of extrusion should be correct;
5. Avoid the influence of floating calcium.

• Some antioxidant system is generally added to make masterbatches, as well as some lubricants, but the amount is very small. Under the action of high shear, the color of the masterbatch without the protection of the antioxidant system will turn yellow, and the masterbatch will also degrade, and the performance of the material will decrease at the same time, and it will not be able to be granulated.
• One of the main uses of antioxidants is to prevent discoloration and oxidative decomposition. However, due to the high price of antioxidants, considering the cost and other factors, whether to add antioxidants to the masterbatch and the amount of addition mainly depends on the processing needs of downstream customers and which products the masterbatch is to be applied to. If the product is used outdoors, in addition to adding UV stabilizers, antioxidants should also be added; if customers have anti-aging requirements, the color masterbatch antioxidant system should also be made into a concentrated type.
• In short, under the premise of no special requirements and guaranteed performance, to increase the enterprise’s profit margin, the antioxidants in the color masterbatch will not be added in principle. However, antioxidants are still added to the color masterbatches used for engineering plastics such as PA and ABS, and there are many weather-resistant masterbatches for engineering plastics. In addition, some antioxidants are generally added to fiber-grade color masterbatches.

The precise test methods for masterbatch density are as follows:

• Using the density bottle method to measure, ithas high requirements for operation, no air bubbles, and the test temperature also has a certain influence on the density;
• Using density gradient meter measurement, accurate measurement, easy operation;
• Measure by an electronic hydrometer suitable for solids, also called an electronic specific gravity balance. The principle is Archimedes’ law, and it can be accurate to four digits.

There are general and specified base materials for masterbatch.

The material used as the base material generally has good processability and thermal stability. PE and EVA are mostly used in general-purpose base materials, PP and PVC are also used; ABS color masterbatch should use itself as the base; SAN is generally rarely used as the base material, as the cost is high; if it is a chemical fiber color masterbatch, there is no universal base material, and a specified base material is required, because other base materials will have a great impact on the strength of the silk.

The advantage of general-purpose color masterbatch is that it is easy to use, but its disadvantage is that the scope of “general purpose” is very narrow, and the technical indicators and economic benefits are also poor, as shown in:

• The predictability of the coloring effect is poor. The color masterbatch is used for coloring, and the pigment of the general color masterbatch will show different colors in different plastics, so the predictability of the coloring effect is poor;
• Affect other properties of plastic products. Especially affecting the strength, the product is easy to deform and twist, and the impact on engineering plastics is more obvious;
• The cost is relatively high. To be “universal”, general-purpose color masterbatches often use pigments with higher heat-resistant grades, resulting in waste.

Compatibility additives for color masterbatch and resin are:

• Coupling agent. The two ends react with the pigment and resin respectively, and connect the pigment and resin with chemical bonds;
• Compatibilizer. One end is compatible with the pigment, and the other end is compatible with the resin, and interacts with intermolecular forces, similar to the principle of lipophilic and hydrophilic detergents;
• Degussa silicone plastic additive Tegonler; it not only acts as a compatibilizer, but also adds a lubricating main chain for lubrication.

In addition, it can be considered to directly use a compatibilizer as the carrier resin of the color masterbatch, such as ethylene-acrylate copolymer, which has good compatibility with PE, PS, PP, PP, etc.

The causes and solutions of the problem are as follows:

• The color point may be caused by uneven dispersion. If the shear of the screw is too weak, a certain pigment in the masterbatch will not be well dispersed. You can use twin-screw equipment with stronger shear; use a dispersant with good dispersibility, and pay attention to the amount of dispersant, otherwise there will be leakage; Add some silicone additives in the process of color masterbatch production, which will improve the uniform dispersion of the toner.
• The fluidity of the carrier is not good. A resin with a high melt flow rate can be used as a carrier. 50% ABS plus 50% SAN (both powder) as the carrier, and then add some lubricants (such as EBS), or use SAN to add some PE as the carrier;
• The fluidity of titanium dioxide is not good. Titanium dioxide can be used rutile. It may also be that the amount of TiO2 in the formula is too high, which will bring out the impurities in the machine. Therefore, it is also necessary to ensure the cleanliness of the machine, and the filter screen can also be encrypted at the die head;
• It may also be caused by the fact that the raw materials are not dried well and produce air bubbles.

The reason for the yellowing of the film can be found by the following methods:

• Try blowing transparent and milky white films with the same formula, that is, transparent without color masterbatch. Place it in a high-temperature open environment for about a month. If only the milky white film turns yellow, it means that the color masterbatch uses anatase titanium dioxide. If all yellowing occurs, it is necessary to suspect whether the antioxidant of the resin has BHT or other unstable types, or other antioxidants are added; at the same time, the yellowing of the non-printed and printed films can be compared. Try to use 100-200 layers of overlapping, so that the color difference is more obvious.

The solution to the yellowing of the film is as follows:

• Pay attention to the matching and ratio of antioxidant and titanium dioxide. Some antioxidants are phenolic. Phenols are easily oxidized into quinones, causing the product to turn yellow. Some auxiliary antioxidants can be added, such as: 168. In addition to the quality of the antioxidant itself, it is also related to the amount and variety of the antioxidant used, and the effect of the antioxidant and titanium dioxide will have an impact. Anatase titanium dioxide is prone to yellowing, and it is best to use rutile titanium dioxide for outdoor use, but the color is not as good as anatase, so you can consider adding more titanium dioxide;
• Calcium carbonate may also cause problems, because the calcium carbonate in the masterbatch is generally coated with stearic acid. Calcium carbonate is generally added with whitening agent and will not change color, but it must be imported. Trace metals contained in calcium carbonate act as catalysts to accelerate oxidation reactions. The effect of ordinary antioxidants is not obvious, and the effect of metal deactivators is also very limited;

The reasons and solutions for the red film may be as follows:

• Hindered phenol antioxidants are easy to isomerize into quinones after giving hydrogen free radicals, and quinones turn yellow or red; it may also be that the antioxidants and raw materials contain water;
• It may be the problem of the proportion of antioxidants in PE used for blown film, which should be solved by changing the grade;
• Adding some stearate can solve the problem of turning red.

Source of content: From Qingzhou Xinming New Materials, Xintec Translation

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