At the same time as the rapid development of human civilization, the use of environmental resources has been exhausted, resulting in environmental changes and destruction that have affected human life. The appearance and promotion of synthetic paper, although it can not change this situation, but it is after all a material that can ease the environmental damage. At the end of the 20th century, synthetic paper with polyolefin as the main material emerged. Because it possesses two properties of paper and plastic, it has the advantages of light weight, good rigidity, etc. It can replace natural paper in many special fields.
Synthetic paper has a history of more than 30 years in foreign countries, and it has developed earlier and faster in developed countries such as the United States and Japan. Raw materials and production processes of natural fiber papers have caused great changes and damages to the environment. With the strengthening of global environmental protection awareness, new synthetic papers are constantly emerging, and their application scope is also continuously expanding. Global synthetic paper sales volume Every year, it is growing at a rate of 10%. The pace of replacing synthetic fiber paper with fiber paper is increasing.
At present, the varieties of synthetic paper are mainly polypropylene and polyethylene. The companies that produce polypropylene-based synthetic paper include Japanese prince Oki, Nisshin Seisui Sekisui Chemical Co., Ltd., British BXL, DuPont, Apulia, France, and Formosa Plastics, Taiwan, and manufacture HDPE as a base material. The company's synthetic paper companies include Japan Mitsui, Japan's Nakagawa, Switzerland's Shulman, and Germany's ALPINE.
China's synthetic paper started late and the market was not developed enough. The technology still needs to be further improved. At present, the amount mainly depends on imports, basically polypropylene synthetic paper, used as garment bags, handbags, woven bags, offset printing, screen printing, advertising inkjet, books, printed trademarks, etc., of which advertising inkjet printing accounted for 40%, printing Trademarks accounted for 15%, woven bags, offset printing, and screen printing usage each accounted for 10%, handbags, garment bags accounted for 10%, and book consumption accounted for 5%. According to the thickness specification, 40 to 50 micrometers accounted for 30%, 90 to 150 micrometers accounted for 40%, and other thicknesses accounted for 30%.
Here are some of the main technical features of synthetic paper:
First, the characteristics of synthetic paper
1. Environmental protection: The raw material and production process of polypropylene synthetic paper will not cause environmental damage. The product can be recycled and reused. Even if it is burned, it will not produce poisonous gas, causing secondary pollution and meeting the requirements of modern environmental protection. 2, superior performance than plain paper: Synthetic paper has the characteristics of high strength, tear resistance, anti-perforation, abrasion resistance, folding resistance, moisture resistance, and insect resistance. 3, has a wider range of uses than ordinary paper: synthetic paper excellent water resistance, making it particularly suitable for open air outdoor advertising and non-paper trademark labels. Because the synthetic paper is free from dust and lint, it can be used in clean rooms. Can be in direct contact with food. 4, superior processing performance, can use cutting, die cutting, embossing, bronzing, drilling, hot folding, bonding and other processing methods.
Second, the production method of synthetic paper
Synthetic paper has developed so far, the main production methods are rolling, casting, blown film, biaxial stretching. The main manufacturers are: Japanese prince Yuba (YVPO), China Taiwan Formosa South Asia (NANYA), Puglia, France. There are only a few companies in China that can produce, the quality is relatively poor, and it is not very stable. The following are the introduction of several production methods:
1. Calendering method
Its equipment is mainly made in Italy and produces synthetic paper with PP as its base material. That is, through batching, mixing, on-line smelting, extrusion molding, rolling to rolling. Cut into synthetic paper products, the key equipment is an extruder made in Italy, once completed, continuous, high efficiency and good quality. The disadvantage of the calendering process is the complexity of the process. It is generally used to produce synthetic paper products with a thickness of 0.1 mm or more. The product has a large proportion and the equipment is expensive. However, the product has a smooth surface and is suitable for printing high-grade samples and book cover products.
2. Casting method
The process of compounding, mixing and mixing of cast synthetic paper is similar to rolling, except that the casting machine is used in place of the calender. The characteristics of the casting method are that the extrusion speed of the die and the rotation of the casting roll are large. The difference in speed and speed is not the same. The thickness of synthetic paper produced is also different. A uniaxial stretching is formed between the meniscus and the chill roll where the die is extruded. The casting method can produce various thicknesses of the composite. paper. However, the distribution of the molecular chains in the synthetic paper is unidirectional. Therefore, the longitudinal, transverse, and physical properties of the synthetic paper products are greatly different. This is a major disadvantage of cast synthetic paper. The casting method has a specific gravity of about 1 g/cm3 and is mainly used for printing. As with calendering, the base material for cast synthetic paper is also PP. Its product is slightly deformable, but its rigidity and toughness are better.
3, blown film method
The material used in the blown film process for the production of synthetic paper is HDPE, which is different from the calendered and cast PP substrates. In foreign countries, most of the synthetic paper produced by the blown film method uses three-layer co-extrusion equipment, and the internal cooling device, bubble film thickness, bubble film thickness on-line detection and closed-loop control system are used to ensure that the thickness uniformity of the synthetic paper is the same. Blown film process to achieve vertical and horizontal stretch, process equipment is relatively simple, the German company ALPINE launched the first single-layer blown film production of synthetic paper, using HDPE and masterbatch as raw materials.
4, biaxial stretching
In recent years, Taiwan Formosa Plastics Co., Ltd. has launched a "biaxially-stretched pearl paper" whose base material is also PP. The raw material blending and rolling and casting methods of the biaxial stretching method are basically the same, but the equipment used is a biaxial stretching machine. In the process of biaxial stretching, the longitudinal and transverse distributions of the molecular chains of plastics are relatively uniform, so the physical and mechanical properties of the synthetic paper are almost the same. In the biaxial stretching process, some small gaps are formed between the base material plastic and the filler CaCO3, thereby reducing the specific weight and cost of the synthetic paper. Since these small gaps have a pearlescent effect on the refraction of light, the produced synthetic paper has a better appearance and has been widely used in the fields of packaging, printing, advertising, and the like. Although the biaxially-stretching synthetic paper equipment is expensive, the technology and the formulation technology are also relatively complex, and widespread application is still limited. However, its application range is the most extensive, and it will be the mainstream of the development of synthetic paper. In the international packaging industry is still a relatively frontier packaging process.
5, other production process of synthetic paper
DuPont Co., Ltd. successfully developed the "non-woven paper" production process. DuPont Co., Ltd. is one of the largest non-woven production companies. DuPont will promote its non-woven fabric production process to the production process of synthetic paper, even if the base material of synthetic paper is mainly polypropylene through melting, spinning, web formation, extrusion. Pressed and finally produced "non-woven synthetic paper". Because non-woven synthetic paper is woven with plastic fibers, it has a high capillary effect. It also has the characteristics of paper, light weight, strong permeability, good physical and mechanical properties, good coloring strength and low deformability. General synthetic paper outside the scope of application, but also widely used in furniture packaging, decoration and other industries. However, the price of non-synthetic synthetic paper is rather high. The production process and equipment are complicated and the cost is high, which limits its widespread application.
Three, biaxially stretched synthetic paper equipment features
The width of biaxially stretched synthetic paper is more than 4 meters at present, and the maximum width is more than 8 meters. The production line speed is high, certain types of line speeds can be as high as 300 meters or more, and the entire line is highly automated. The control systems for temperature, speed, pressure, tension, and thickness control in the production process are all centralized and digitally controlled.
The equipment for biaxially stretching synthetic paper has a large investment, but the products produced by this method are widely used, and various products can be developed according to different purposes to suit printing or packaging fields.
The equipment for producing biaxially-stretched synthetic paper is mostly based on BOPP equipment and modified to suit the production of synthetic paper. In order to fully reflect the plastic characteristics of synthetic paper and the printing characteristics of paper, to produce better synthetic paper, the performance requirements of the equipment will be higher.
Fourth, material characteristics
Biaxially-stretched synthetic papers are generally three-layered in structure, and different material properties can be selected to meet different needs and application areas. The surface layer material must meet people's sense requirements for traditional paper, and also need to meet various printing requirements and require high ink absorption performance.
The surface layer material can also be adjusted according to different customers' different use requirements, meet the special requirements of synthetic paper in different application fields, and fully embody the advantages of different fiber papers of synthetic paper. For example, heat sealable synthetic paper, in-mold labels, etc. have been developed.
The core material can be made by adding functional masterbatches to make its density lower, lower its cost, or significantly increase its strength to suit specific application fields. It can also add anti-aging agents, extend its service life, and reduce customers' operating costs.
Plastic substitute paper is the goal of the development of synthetic paper, improving quality is the key, and reducing costs is the foundation.