The inorganic fillers (such as calcium carbonate, talc powder, wollastonite, titanium dioxide, etc.) in synthetic paper account for about 60% to 80% of the total mass of synthetic paper. According to the different uses of synthetic paper, PP, PE and other resins and various chemical additives are added, and through blending, modification, and extrusion processes, a specialized masterbatch is produced.
At present, synthetic paper at home and abroad is mainly divided into rolling method, casting method, blowing film method, biaxial stretching method, and non-woven paper method. According to the structure and usage requirements, it is divided into single-layer synthetic paper, three-layer synthetic paper, five-layer synthetic paper, and multi-layer synthetic paper.
1. Synthetic paper rolling production method
The process flow of rolling method: ingredients, blending, internal mixing, and extrusion are used to produce specialized masterbatch, which is then extruded, rolled, stretched, cooled, surface treated, cut, and coated to form synthetic paper. Some of this process flow adopts specialized masterbatch and rolling segmented production, while some advanced production equipment abroad also adopts continuous one-time forming process.
The rolling method has high production efficiency, good product quality, and smooth paper surface, making it suitable for printing high-end picture albums and book covers. Its drawbacks are complex processes, a large proportion of products, and expensive equipment prices.
2. Synthetic paper casting production method
The production process of casting method is basically similar to that of rolling method. The characteristic of the casting method is that there is a certain speed difference between the extrusion speed of the die head and the rotation of the casting roller, forming a stretch between the meniscus of the die head extrusion and the cooling roller. The thickness of the synthetic paper can be adjusted according to different product requirements. There are many products based on PP resin, which have advantages such as good rigidity, high toughness, and good tensile strength. Due to the production process, the molecular structure distribution of the product is unidirectional, and the longitudinal and transverse physical properties of synthetic paper have certain differences.
Using polypropylene resin, we produce shopping bags, packaging boxes, food packaging boxes for airplanes and shopping malls, with a delicate appearance and natural degradation.
3. Synthetic paper blown film production method
The base material used in the production of synthetic paper by blown film method is mostly PE, mainly formed by three layer co extrusion blow molding. Some also use single layer, five layer, and multi-layer production processes. Depending on the product purpose, the resin content of the inner and outer layers of synthetic paper can be appropriately increased. The inorganic powder content of the inner layer is high, and the materials used in each layer are different. The longitudinal and transverse stretching of the product can be adjusted within a certain range to ensure uniform thickness and stable physical properties of the synthetic paper product.
The characteristics of this process are high yield, simple process, uniform product thickness, and low equipment investment. However, due to the high resin content and certain limitations in the width of the paper.
The film blowing method is divided into upper blowing method and lower blowing method:
4. Synthetic paper - unidirectional stretching production method
The unidirectional stretching method adopts an extrusion process similar to rolling and casting, and is equipped with a unidirectional stretching system. After longitudinal stretching, the distribution of resin molecular chains is uniform and consistent, and the physical properties of synthetic paper in the longitudinal direction are also basically similar. During the unidirectional stretching process, small gaps that are difficult to observe may occur between synthetic resins and inorganic powders due to differences in material properties and interfacial compatibility, commonly known as the "island phenomenon". These phenomena can reduce the specific gravity and production cost of synthetic paper, and also significantly improve the physical properties, appearance, coloring, and moisture absorption of synthetic paper. Especially after stretching, it will form a certain pearlescent effect, giving paper printing a magnificent and exquisite effect, suitable for advertising spray painting, exquisite art albums, and other aspects. The unidirectional stretching process has complex equipment, high investment, and exquisite production technology, which will be limited by various factors in the early stages of popularizing synthetic paper. However, the product has excellent performance, low production costs, and a wide range of uses. This process will be the development direction of synthetic paper and also an advanced processing technology currently applied internationally.
5. Synthetic paper non-woven paper production method
DuPont Company in the United States applied its non-woven fabric production process to the production of synthetic paper, using polypropylene as the main substrate to produce "non-woven synthetic paper". After the raw and auxiliary materials are melted, extremely fine filamentous fibers are extruded and rolled to form non-woven synthetic paper.
The product has the characteristics of paper, with a light weight, strong permeability, good physical and mechanical properties, high coloring strength, and low product deformation. This product can be widely used for furniture decoration, product packaging, interior decoration wallpaper, etc. However, this process has high production costs and complex processing equipment.
At present, many domestic manufacturers are trial-producing synthetic paper, and many enterprises have conducted various innovative research in raw materials, equipment, processes, etc., such as heavy/light calcium blending, PP/PE composite, one-step blending/extrusion production process, and so on.
To learn more about the production process and equipment of the "synthetic paper/stone paper" project, Nanjing Juli Chemical Machinery Co., Ltd. welcomes you to call, write or visit our company to discuss and exchange technical and equipment matters related to the production of "synthetic paper/stone paper"!