Application of the hottest anti sticking agent in

2022-10-17
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The application of anti adhesion agent in BOPP film

I. Introduction

the auxiliary products of biaxial tensile film packaging materials mainly include antistatic agent, smooth and anti adhesion agent, stiffening agent, heat stabilizer, antioxidant and barrier agent. In the production of BOPP film, additives with different functions, such as antistatic agent, smoothing agent, adhesion agent, stiffening agent, whitening agent, etc., are usually added according to the different uses of the film, but anti adhesion agent must be added no matter what kind of BOPP film is produced. Otherwise, there will be many problems in the winding, slitting and other processes in the production process of film products, as well as in the later packaging and use, and even can not be used. In particular, modern plastic processing is developing in the direction of automation, high speed and high quality. The faster the processing speed is, the easier it is to generate static electricity due to friction, and the easier it is to adhere between films, which seriously hinders the production of high-speed lines. Moreover, the more transparent the film is, the higher the processing temperature is, and the easier it is to adhere. Therefore, the anti adhesion agent plays an extremely important role in the manufacturing process of the film product itself and the automatic packaging process used in the future. In this sense, anti adhesion agent is the most important additive in BOPP film production, which is the main content of this article

second, the action mechanism of anti adhesion agent

the usual way to solve the problem of film adhesion is to add a certain proportion of anti adhesion agent on the surface of BOPP film. The mechanism is that the anti adhesion agent is incompatible with polypropylene raw materials and has a higher melting point than polypropylene, which can ensure that it will not be melted during melt extrusion in the process of film production. The particle size of anti adhesion agent is generally 3-5 μ m. The thickness of the surface layer of the film is about 1 μ m. After the film is formed in this way, these anti adhesion agents form many protrusions on the surface of the film, or there are different loose bumps, which makes the surface of the film rough, and a certain amount of air can be left between layers, thus preventing the adhesion between layers. The concave convex condition of the anti adhesion agent on the film surface is shown in Figure 1:

Figure 1 convex concave shape of the film surface III, selection of anti adhesion agent

as the anti adhesion agent used in BOPP film, there are currently two categories, inorganic and organic, which should meet the following requirements:

(1) it has a similar refractive index with polypropylene resin

(2) the particle size of anti adhesion agent should be suitable for the thickness of film surface

(3) it can be evenly dispersed in polypropylene to avoid scratching the film surface:

(4) it should meet the hygienic requirements of food packaging

1. Inorganic anti adhesion agents

inorganic anti adhesion agents that have been applied in film products mainly include diatomite, talc powder, calcium carbonate, synthetic silicon dioxide and glass beads. Different materials have different properties, and not all inorganic anti adhesion agents can be used for BOPP films. Compared with the requirements of packaging performance, talc powder and calcium carbonate have a great impact on the optical properties of the film, which will affect the haze. It is not suitable for BOPP film. Diatomite has high hardness and is easy to scratch the film surface. Its application is also limited, and the anti adhesion effect of different materials is also different. Figure 2 shows the relationship between the adhesion force and the amount of adhesive added:

Figure 2 the relationship between the adhesion force and the amount of adhesive added. Among these inorganic anti adhesion agents, synthetic silica is a very effective anti adhesion agent, with the advantages of

(1) the refractive index is very close to that of polypropylene, which has little impact on the optical properties

(2) amorphous structure, which will not lead to silicosis

(3) extremely high chemical purity, suitable for plastic packaging in the food industry

based on these advantages of synthetic silica, it is currently the most widely used in BOPP film products

2. Organic anti adhesion agents

in recent years, another kind of anti adhesion agent applied to BOPP film is organic anti adhesion agent, which is generally silicone polymer or methacrylate polymer. This cross-linked polymer particle with a specific structure, after mixing with polypropylene resin, forms a protrusion with an average height of 60~600nm on the surface of the film after directional stretching, thus playing the role of film adhesion prevention. The advantages of organic anti adhesion agent are:

(1) good optical property, which has little effect on the transparency of the film

(2) it has the function of increasing sliding, so that the film has a low friction coefficient

(3) the film surface will not be scratched, and the film gloss is high

the material price of organic anti adhesion agents is much higher than that of inorganic anti adhesion agents, which is generally about times, so organic anti adhesion agents are currently only used in high-end BOPP film products

fourth, the addition form of anti adhesion agent

in order to make the anti adhesion agent work in the film, it must be evenly dispersed. In order to obtain better dispersion effect, anti adhesion agents are generally added in the form of masterbatch. The concentration of anti adhesion agent in masterbatch is usually%, and the conventional concentration is 5%. Twin screw extrusion granulation is adopted

in the manufacturing process of anti adhesion masterbatch, the lower the concentration of anti adhesion agent, the easier the masterbatch processing and the better the dispersion. However, for film manufacturers, using low concentration masterbatch means increasing the amount of masterbatch in the production of film products, which increases the processing cost. Therefore, in the manufacturing process of anti adhesion masterbatch, we should not only control the necessary concentration of anti adhesion agent, but also grasp the dispersion uniformity of anti adhesion agent in the masterbatch

v. impact of anti adhesion agent on film performance and equipment

1. Impact on film performance

as the anti adhesion agent is added to the film surface, it increases the roughness of the film surface, thus improving the export amount of the extruder, and gradually picks up the anti adhesion performance of the film, but it will also have a negative impact on the optical performance of the film and have varying degrees of impact on other properties. The influence of anti adhesion agent on gloss and haze is shown in the following figures 3 and 4:

Figure 3 the influence of anti adhesion agent on gloss

Figure 4 the influence of anti viscosity on haze

the influence of anti adhesion agent on film performance is shown in the following table:

Figure 5: the influence of anti adhesion agent on film performance

2, the influence on equipment

inorganic anti adhesion agent has different degrees of influence on film optical performance, and it is worth noting that, After adding inorganic anti adhesion agent, for mechanical equipment, it is equivalent to adding grinding impurities that cause wear, which will directly wear the equipment and packaging machinery on the high-speed production line. For example, the screw, cylinder barrel and film lip clearance of the extruder will affect the accuracy and stability of the equipment to a certain extent over time

the organic anti adhesion agent has relatively low softening temperature or melting point, and has smooth performance, which has little impact on the optical properties of the film, but it is easy to degrade on the high-temperature die head and accumulate in the die head, which will affect the quality of the thin film over time. Both types of additives have their own advantages and disadvantages. From an economic point of view, inorganic anti adhesion agents have low cost, are widely used, and organic anti adhesion agents have high cost, so their application is limited

VI. application of anti adhesion agent in BOPP film

1. Application in ordinary flat film

ordinary flat film is used for printing, paper lamination, adhesive tape base film, etc. the thickness of these films is generally within the range of 15 A-28 T-shirts, and synthetic fiber replaces 20000 tons of imported products, and all of them must undergo corona treatment. The thinner the film, the easier it is to adhere, and corona treatment will also make the film surface sticky

therefore, synthetic silicon with high anti adhesion efficiency should be selected as anti adhesion agent, which is the most widely used variety in BOPP film at present. If producing shallow printing film with thin surface or low haze products, silicon dioxide with small particle size or glass beads with smooth surface can be used as anti adhesion agent, which has better printing effect than ordinary synthetic silicon

2. Application in aluminized film and smoke film

aluminized film requires good surface performance, firm adhesion of aluminum layer, and 4) the analytical value of finite element method is in good agreement with the measured value, with a low friction coefficient. The smoke film requires high gloss, smooth surface and easy packaging. In view of this situation, organic anti adhesion agents with uniform particles or glass beads are better. Because ordinary synthetic silicon particles are irregular, easy to scratch the film surface, and the friction coefficient will not be very low, it is not suitable for the application of these two kinds of films

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