1. The amount of Carbon Black added
In order to effectively and economically produce plastic mixtures, the amount of carbon black used in the dispersion process should be as high as possible, but also considering the operability of grinding, as well as the type and quality requirements of the product.
Different plastics have different requirements for dispersion. In many cases, the poor performance of black plastic mixtures is directly related to the poor dispersion of carbon black. This further demonstrates the importance of maintaining good dispersion.
The plastic industry has very strict requirements for the performance of raw materials, such as cable sheaths and fiber products, which have high requirements for color dispersion. Due to the optimal dispersion of pigments, good control of plastic properties can be achieved, such as color, tone, viscosity, gloss, durability, and extrusion performance. On the other hand, daily necessities applications such as molded flower pots generally do not require excessive dispersion of carbon black.
The purpose of dispersions is to produce products that meet customer performance requirements, but often due to the poor quality of dispersions and the stability of the final product, they cannot provide the best carbon black performance. Dispersions with low quality and poor stability can also be seen from the appearance and performance of the obtained Color Masterbatch or final product. Below are some common questions.
① "Coarse", "sand" and "adhesion" are commonly used terms to describe small gel like adhesion due to instability of liquid color paste or plastic solution. The solution to this problem is to improve the dispersion situation by improving equipment, adding additives, or using other technologies.
② Poor dispersion of color paste can lead to a decrease in blackness, brown tone, and low gloss, which can also occur in the final product. The problems caused by poor dispersion can only be solved by increasing the mixing force. These can be achieved by selecting better carbon black, extending mixing time, and improving mixing conditions.
③ The amount of carbon black added can lead to an increase in viscosity, causing a temperature increase during mixing. This is particularly detrimental to thermosensitive resins. Too much heat will produce gel, thus reducing the dispersion quality and stability. Reducing the amount of carbon black added or controlling the appropriate temperature can help alleviate this problem.
2. Ratio of carbon black to polymer
The ratio of carbon black to polymer is higher in the color masterbatch, but each polymer has a limited capacity for pigments. This limited degree can only be determined through actual production formulas and testing on all production equipment.
If the plastic mixture needs to be further diluted, it is important to ensure that there is sufficient polymer to achieve a suitable viscosity that facilitates the entry of the color masterbatch into the diluted Resin. To achieve the best mixing performance, the selection of carbon black partially depends on the viscosity requirements of the mixture.
3. Problems and limitations caused by the addition of high carbon black content
When preparing dispersions, excessive addition of carbon black can cause many problems. Although high addition is an ideal idea, it is important to consider the actual usage limit. Below are some limiting factors.
① Color masterbatch viscosity. There are many types of grinding and dispersion equipment in the market, and their dispersion efficiency for carbon black varies. The primary factor causing this difference is the viscosity of the color masterbatch. For example, enclosed mixers or double roller mixing equipment are particularly suitable for high viscosity mixtures.
② The chemical properties of the carrier. The compatibility between the carrier and carbon black affects the need for dispersion energy. Good interaction energy between polymer and carbon black can promote wetting and accelerate dispersion process. In other words, the stronger the interaction between carbon black and carrier, the better the performance of the mixture.
When high pigment content is required, polymers that can adapt to this high pigment content should be used.
The correct selection of effective wetting and dispersing agents can improve the performance of plastics. In addition, plastic manufacturers should consider that post-treated carbon black can bring better dispersion and rheological properties when selecting carbon black.
4. Dilution and dispersion of carbon Black Masterbatch
It should be mentioned again that even if the best technology is used to prepare color masterbatches, improper dilution of color masterbatches into plastic formulas can result in complete failure. The microscopic photos in Figures 5-16 illustrate the results caused by improper dilution of a good dispersion. From the low magnification photos, it can be seen that dispersion A appears to have poor dispersion quality, while the high magnification photos show that good dispersion has been achieved. By combining the observation of two different magnification factors, it can be seen that although the dispersion effect of dispersion A is not good when manufacturing color masterbatches, the dilution method is appropriate; The dispersion effect of dispersion B is good, but the dilution method is not appropriate. Below are some methods to avoid this problem.
① If the viscosity of the color master batch is very high, the dilution process should be carried out slowly, and the diluted polymer should be added in small batches, otherwise the color master batch will form a material cluster with gel like spots, which is difficult to further disperse.
② Diluting high viscosity masterbatches into low viscosity polymer substrates is usually a challenging task. If the viscosity of the color masterbatch and the resin matrix match, a good dilution effect can be expected. This can be achieved by selecting the resin or controlling the temperature of each component. If possible, the color master batch should be melted first to soften it, and then the resin to be diluted should be added. When using this technology, the viscosity of the diluted resin can exceed or exactly match the viscosity of the color master batch, providing the most suitable dilution conditions.
③ The resin or base material used for dilution should be selected correctly, and the technical specifications of the final product should always be remembered. Suitable polymer systems should be used, which should be clean and free from any small particles and other impurities. Impurities often cause "spots", "spots", "stains", "fish eyes", etc., resulting in poor appearance of products.
5. Carbon black dispersion technology for plastics
The operation must be carried out as follows: adding carbon black to the carrier system; Replace the air adsorbed on the surface of carbon black with a carrier (allowing the pigment to be fully soaked); Reduce the large aggregates of carbon black into micropolymers or aggregates using dispersed energy.
If the above steps can be followed, carbon black can exhibit excellent blackness, color tone, coloring power, luster, stability, and rheological properties.
