Five elements of defoaming masterbatch that need to be paid attention to during the film blowing process

When the defoaming masterbatch is used in the film blowing process, it is necessary to pay attention to its matching with the process conditions to ensure the effective elimination of bubbles and guarantee the quality of the film. 

The following are five key elements to pay attention to: 

1.Processing temperature control the decomposition temperature of the defoaming masterbatch: The defoaming agent (such as silicone or mineral oil) in the defoaming masterbatch needs to release the active ingredient within a specific temperature range. If the temperature of the film blowing machine is too high, the defoamer may decompose in advance and fail. The temperature is too low to fully activate the defoaming effect.

Suggestion: Adjust the temperature of each section of the film blowing machine (such as extruder and die head temperature) according to the recommended temperature of the defoaming masterbatch (usually marked in the product manual). For example, the applicable temperature of silicone defoamer masterbatch is generally 180-240 ° C.

2. The consequences of poor dispersion of masterbatch dispersion uniformity: If the defoaming masterbatch is mixed unevenly with the resin matrix, it will lead to poor local defoaming effect or produce "fish eyes" (undispersed particles), affecting the surface finish of the film. Solution: Ensure that the masterbatch is fully premixed with the resin, and use a high-speed mixer or twin-screw extruder to enhance the mixing effect; Adjust screw speed and back pressure to optimize melt shear force to promote dispersion. 

3. The effect of excessive or insufficient addition ratio is precisely controlled: too little addition can not effectively eliminate bubbles, and too much may cause the film surface to become sticky and mechanical properties to decline (such as weakening tear resistance). Recommended ratio: Generally 0.1-1% of the base resin (specific needs to be determined according to the masterbatch concentration and bubble severity test). It is recommended to determine the best ratio by small experiment when using for the first time. 

4. Raw material pre-drying treatment of water interference: If the resin or masterbatch contains water, it will vaporize and produce additional bubbles during high temperature extrusion, counteracting the effect of the defoaming masterbatch. Key operation: The resin and defoaming masterbatch should be dried at 80-100℃ for 2-4 hours (depending on the hygroscopiness of the material), ensuring that the water content is less than 0.05%; Use closed drying equipment to avoid secondary moisture absorption. 

5. Film blowing process parameters optimization screw speed and pressure: high speed may lead to insufficient melt residence time, defoamer can not be fully released; Low speed may be due to insufficient shear force dispersion. Adjustment suggestions: Balance the screw speed and traction speed of the extruder to ensure that the melt stays in the barrel for a moderate time; The control die head pressure is stable to avoid pressure fluctuations resulting in bubble residue.

 Blowing ratio and cooling rate: too high blowing ratio or too fast cooling may cause bubbles to be "frozen" in the film. It is necessary to properly reduce the blowing ratio (such as 1:2~1:3) with the action of defoaming masterbatch and optimize the cooling conditions of the wind ring. Compatibility with resins: Different resins (such as LDPE, LLDPE, PP) have different adsorbability to defoamer masterbatch, so specific formulation should be selected. For example, polar resins such as PA may require specially modified defoamer.

 Equipment cleaning: regularly clean the screw and die head to prevent residual masterbatch or impurities from affecting subsequent production. 

Through the systematic control of the above elements, the efficiency of the defoaming masterbatch in the film blowing process can be significantly improved, and the film can be frost-free, the surface is uniform and the physical properties are up to standard. It is recommended to verify parameters through small batch trial production before large-scale production.