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Injection Molding Machine Process - How To Deal With Problems After Adding Masterbatch
- Oct 22, 2018 -

1. In the sunlight, there are strips of pigment strips in the product.

 

Considering both physical and mechanical properties of plastics and plastic molding processes:

 

1. The temperature of the injection molding equipment is not well controlled, and the color master cannot be thoroughly mixed with the resin after entering the mixing chamber.

 

2. The injection molding machine does not add a certain back pressure, and the screw mixing effect is not good.

 

3. The dispersibility of the color masterbatch is not good or the resin is not plasticized.

 

The process can be debugged as follows:

 

1. Increase the temperature of the mixing chamber by the drop port portion slightly;

 

2. Apply a certain back pressure to the injection molding machine.

 

If it is still not good after the above debugging, it may be the dispersibility or matching problem of the color masterbatch and the resin, and should be solved by contacting the masterbatch manufacturer.

 

Second, after using a certain color masterbatch, the product appears to be more susceptible to cracking.

 

This may be due to poor diffusion and miscibility caused by the poor quality of the dispersant or auxiliary agent selected by the manufacturer, which affects the physical and mechanical properties of the product.

 

Third, the same color masterbatch, resin and formula, the color of the product injected by different injection molding machines has a shade

 

This is often caused by the injection molding machine. Different injection molding machines have different mechanical conditions due to different manufacturing, use time or maintenance conditions, especially the difference in the degree of adhesion between the heating element and the barrel, so that the dispersion state of the color master in the barrel is also different. A phenomenon will appear.

 

Injection molding machine process - how to deal with problems after adding masterbatch

4. After changing the resin of another brand, the same color masterbatch and formula, the color has changed.

 

Different grades of resin will have different density and melt index, so the properties of the resin will be different, and the compatibility with the color masterbatch will be different, resulting in color change. Generally speaking, as long as the density and melt index are not much different. , then the difference in color will not be too large, you can correct the color by adjusting the amount of color masterbatch.

 

5. If the color masterbatch undergoes pigment migration during storage, will it affect the quality of the product?

 

Some color masterbats have a high pigment content (or dye), and in this case, migration is normal. Especially the color masterbatch with dye added, serious migration will occur. However, this does not affect the quality of the product, because after the color master is injected into the product, the pigment is in a normal color development concentration in the product.

 

Six, some injection products are not shiny

 

There are several possibilities:

 

1. The nozzle temperature of the injection molding machine is too low

 

2. The mold finish of the injection molding machine is not good.

 

3, the product molding cycle is too long

 

4, too much titanium dioxide contained in the masterbatch

 

5, the color masterbatch is not well dispersed

 

Seven, ABS color masterbatch is particularly prone to chromatic aberration

 

Different brands of ABS produced by different countries have large color difference. Even if the same brand of ABS, there may be chromatic aberration in each batch of batch numbers. Of course, color difference will also occur after coloring. This is due to the characteristics of ABS, and there is no thorough solution in the world. However, this color difference is generally not serious. Users must pay attention to this feature of ABS when using ABS color masterbatch.

 

Injection molding machine process - how to deal with problems after adding masterbatch

8. After using the ratio on the color master specification, the color is too dark (too light)

 

Although this problem is simple, there are many possibilities, specifically:

 

1. The color master has not tried the color carefully, and the pigment is too little or too much.

 

2. Inaccurate measurement at the time of use, the phenomenon of random measurement by domestic enterprises, especially small and medium-sized enterprises

 

3. There is a problem with the matching of the color masterbatch and the resin. This may be due to improper selection of the carrier of the masterbatch, or it may be that the manufacturer randomly changes the resin variety.

 

4. If the machine temperature is not good, the color master stays in the machine for too long.

 

Processing procedure: First check whether the resin type matches the color masterbatch, whether the metering is accurate, and then adjust the machine temperature or speed. If there is still a problem, contact the masterbatch manufacturer.

 

Nine, plastic color matching products faded

 

Plastic colored products can be discolored by a variety of factors. The fading of the plastic colored product is related to the light resistance, oxygen resistance, heat resistance, acid and alkali resistance of the toner, and the properties of the resin used. The following is a detailed analysis of the factors that cause color fading in plastics:

 

1. Light fastness of colorants

 

The light fastness of the colorant directly affects the fading of the product. For outdoor products exposed to strong light, the light fastness (lightfastness) grade requirement of the colorant used is an important indicator, and the light resistance grade is poor, and the product will quickly fade in use. The light resistance grade of weathering products should be no less than six grades, preferably seven or eight grades, and four or five grades of indoor products.

 

The light resistance of the carrier resin also has a great influence on the change of color, and the molecular structure of the ultraviolet-induced resin is changed to fade after irradiation. By adding a light stabilizer such as a UV absorber to the master batch, the light resistance of the colorant and the colored plastic article can be improved.

 

2. Heat resistance

 

The thermal stability of a pigment refers to the degree of thermal weight loss, discoloration, and fading of the pigment at the processing temperature. The inorganic pigment is composed of metal oxides and salts, has good thermal stability and high heat resistance. However, the pigment of an organic compound undergoes a change in molecular structure and a small amount of decomposition at a certain temperature. Especially for PP, PA, PET products, the processing temperature is above 280 °C. On the one hand, when selecting the coloring agent, attention should be paid to the heat resistance of the pigment. On the one hand, the heat resistance time of the pigment should be considered, and the heat resistance time is usually required to be 4-10min. .

 

3. Antioxidant

 

Some organic pigments gradually degrade after macromolecular degradation or other changes after oxidation. The first process is high temperature oxidation in processing, and the second is oxidation of strong oxidants (such as chromate in chrome yellow). When the lake, azo pigment and chrome yellow are mixed, the red color will gradually decrease.

 

4. Acid and alkali resistance

 

The fading of colored plastic products is related to the chemical resistance (acid and alkali resistance, oxidation and reduction resistance) of colorants. For example, molybdenum chrome red is resistant to dilute acid, but sensitive to alkali, and cadmium yellow is not resistant to acid. These two pigments and phenolic resin have strong reduction effect on certain colorants, which seriously affect the heat resistance, weather resistance and fading of the colorant.

 

For the fading of plastic colored products, the above properties of the desired pigments, dyes, surfactants, dispersants, carrier resins and anti-aging additives should be comprehensively evaluated according to the processing conditions and application requirements of the plastic products.