Ever wondered how plastic film, from everyday packaging to specialized applications like BOPP, BOPET, or BOPA, maintains its smooth, non-sticky allure? Well, meet the unsung hero – the anti-adhesion agent. Let’s unravel the journey of these secret additives. Steering clear of technical jargon, we just delve into the everyday magic of plastic film production.
I The Hitchhiker’s Guide to Plastic Film Production
1. Navigating the World of Additives
The field of plastic film production is very broad. A wide range of additives come into the field to tailor the film to a specific application. In the production process, it is often necessary to add some additives to the raw resin. According to the use areas and functional requirements of the plastic film, additives are different. Considering the needs of film making and processing, additives will be more complex. The usual choices are antistatic agents, slip agents, anti-adhesive agents, heat stabilizers, antioxidants, and flame retardants, etc.
In the production of BOPP, BOPET, or BOPA films, adding a specific amount of anti-adhesion agent, also known as a release agent, is crucial. Without it, issues like challenging winding, cutting, and potential film sticking may arise. It affects user usage difficulties.
So, the anti-blocking agent is one of the most commonly used and important additives.
2. Peeling Back the Curtain on Anti-Adhesion
Imagine two plastic film layers coming together, smoothly blending like pieces of glass. Now, in the winding process, with pressure rollers working their magic, these layers practically become inseparable. The external atmospheric pressure does its job – the films stick. The solution? Enter the anti-adhesion agent! Picture this: in BOPET films, a carefully calculated mix of these agents creates tiny bumps on the film surface. These bumps make the surface a tad rougher. Why? To trap a bit of air between layers, preventing the clingy film scenario.
II Choosing the Right Sidekick
1. A Handy Guide to Anti-Adhesion Agents
Choosing the right anti-adhesion agent is an art. Here’s your cheat sheet:
Refractive Harmony:
The chosen anti-adhesion agent should have a refractive index close to polyester resin. It can avoid impacting the optical performance of the film. The closer the refractive indices between the anti-block agent and polyester resin, the less impact there will be on the optical performance.
Size Matters:
Ensure the particle size and quantity align with the film’s thickness.
Even Distribution:
Say no to clumps! The agent must evenly disperse in polyester resin.
Hygiene First:
If it’s for food packaging, the chosen agent better meets hygiene standards.
2. Inorganic vs. Organic Showdown
Inorganic Side
Common players like kaolin, calcium carbonate, titanium dioxide, silica, and barium sulfate steal the spotlight. Each has its role, such as kaolin sparkling in an electrical film. Or the titanium dioxide-silica duo makes for a perfect matte film.
Organic Heroes: Picture organic anti-adhesion agents as the superheroes of recent times. They are usually silicon-based or methyl methacrylate-based polymers. It creates protrusions during stretching. So films can remain smooth, shiny, and free from scratches.
And there you have it, the lowdown on anti-adhesion agents. While inorganic agents rule the roost, organic play their magic in high-end film productions. So next time you unwrap perfectly smooth and non-sticky plastic. Remember – it’s not just a film; it’s a symphony of additives working their magic!
III. Preparation Methods of Anti-Adhesion Agents
In the realm of BOPET film production, specifically, the widespread use of inorganic anti-adhesion agents like silicon dioxide is notable. These agents are employed in the form of a masterbatch. There are two primary methods for preparing silicon dioxide-containing masterbatch:
1. Ethylene Glycol Dispersion
Silicon dioxide powder is dispersed in ethylene glycol through grinding and filtering.
The resulting mixture is injected into the esterification reactor. This reactor contains PTA+EG for the esterification reaction.
The product is then exported, cut underwater, and air-dried to produce masterbatch slices. Silicon dioxide content ranges from 3000 to 8000 ppm.
2. Twin-Screw Extrusion Granulation
Silicon dioxide powder is uniformly mixed with polyester resin.
The mixture is granulated using a twin-screw extruder.
Lower concentrations of the agent lead to easier processing and better dispersion in the process. But, for film manufacturers, using low-concentration masterbatch implies an increase in material usage. It results in higher processing costs. So, controlling the necessary concentration of the anti-adhesion agent is important. Ensuring its uniform dispersion in the masterbatch is crucial.
Impact and Considerations of Anti-Adhesion Agent Application:
IV Effect on Film Properties
Effects and precautions of anti-adhesion agent application:
1. Impact on film properties
The addition of anti-blocking agents increases the surface roughness of the film. It reduces the coefficient of friction and enhances anti-adhesion properties.
But, this may adversely affect optical performance. Examples include increased haze and decreased transparency.
On the positive side, the introduction of silica promotes the formation of crystal nuclei and increases the hardness of the film.
2. Impact on equipment
The addition of inorganic anti-adhesive agents will cause a certain degree of wear on mechanical equipment. Examples include the screw, barrel, and lip areas of the extruder.
Over time, this wear accumulates and affects the accuracy and stability of the equipment.
3. Precautions for using anti-sticking masterbatch
Recommended levels of anti-blocking agents in films typically range from 500 ppm to 1500 ppm ( can be tailored to 30000 ppm). Aluminized films have undergone strong corona treatment. So a slightly higher dose may be appropriate due to increased adhesion.
For the production of lightweight screen printing films or low haze products, it is recommended to select smaller particle-size silica. And control of the amount of masterbatch is also suggested.
If the film haze is too large and the gloss is low, it is recommended to reduce the amount of anti-sticking agent.
Wrinkles or edge running occurs while winding or slitting the film. It suggests that the friction coefficient is too low. There is a need to increase the amount of anti-sticking agents.
White spots or fish eyes on the film’s surface may result from inadequate dispersion of the anti-sticking agent or excessive filtration. In such instances, it is advisable to inspect the filter or substitute the masterbatch.
