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.
At the same time as the rapid development of human civilization, the use of environmental resources has been exhausted. This has caused changes and destruction of the environment that have affected human life. The appearance and promotion of synthetic paper, although it cannot change this situation, is after all a material that can mitigate environmental damage.
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. The raw material sources and production processes of natural fiber papers have caused great changes and damages to the environment. With the strengthening of global environmental awareness, new synthetic papers are constantly emerging, and their application scope is also continuously expanding. The global synthetic paper sales volume Each year is growing at a rate of 10%. The pace of synthetic paper replacing fiber paper is accelerating.
According to the prediction of China Paper Association, by 2010, China will consume 70 million tons of paper and board annually. The demand for paper in China is 2/3 for packaging materials and 1/3 for printing. Even if 5% of printing and packaging papers are replaced by synthetic paper, the demand is also considerable.
China's synthetic paper started late and the market was not developed enough. The technology still needs to be further improved. At present, the total amount of the whole country is 3 to 40 thousand tons, mainly imported. It is basically polypropylene synthetic paper. It is used as clothing bags, handbags, woven bags, Offset Printing, screen printing, advertising printing, books, printing trademarks, etc. Among them, 40% were for advertising inkjet printing, 15% for printed trademarks, 10% for woven bags, offset printing and screen printing, 10% for handbags and garment bags, and 5% for books. According to the thickness specification, the amount of 40-50 micron is 30%, the amount of 90-150 micron is 40%, and the other thickness is 30%.
The company has been committed to the development and application of synthetic paper. 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, no toxic gas will be generated, resulting in secondary pollution. It meets 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. 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, adhesive and other work 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 inferior, and it is not very stable. Here are the introductions of several production methods:
1. Calendering method
Its equipment is mainly made in Italy and produces PP-based synthetic paper. That is, through batching, mixing, on-line smelting, extrusion molding, rolling to rolling. The slitting is a synthetic paper product. The key equipment is an extruder made in Italy. It is completed at one time, continuously, with high efficiency and good quality. The disadvantage of the calendering process is that the process is complex. It is generally used for the production of 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 advanced samples and book cover products.
2. Casting method
The process of compounding, mixing and mixing of cast synthetic paper is similar to calendering except that the casting machine is used in place of the calender. The casting method is characterized in that the extrusion speed of the die and the rotation of the casting roll are large. The difference in speed and speed are different. The thickness of the synthetic paper produced is also different. A uniaxial tension is formed between the meniscus and the chill roll where the die is extruded. The casting method can produce a variety of different thicknesses. 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. Like calendering, the base material for cast synthetic paper is also PP. The product has slightly more deformability, but better rigidity and toughness.
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 calendared 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, foam film diameter, bubble film thickness on-line detection and closed-loop control system are used to ensure that the synthetic paper has the same thickness uniformity. The blown film process realizes longitudinal and partial transverse stretching, and the process equipment is relatively simple. German ALPINE Corporation first introduced a single layer blown film process to produce synthetic paper, using HDPE and masterbatches as raw materials.
4, biaxial stretching
In recent years, Taiwan Formosa Plastics Co., Ltd. has launched a â€œbiaxially-stretched pearl paperâ€ 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 distribution of the molecular chains of plastics is relatively uniform, so the longitudinal and transverse physical and mechanical properties of the synthetic paper are basically 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 good 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 formulation technology are also 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. At present, the domestic manufacturers Guangdong Huaye, Jiangsu Zhongda, and Guangdong Shunde Deguan produced synthetic paper using this method, which still belongs to the frontier packaging processing technology in the international packaging industry.
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 higher capillary effect, more paper characteristics, lighter specific gravity, strong permeability, good physical and mechanical properties, good color strength, and low deformability. The scope of application of general synthetic paper, but also can be 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 currently more than 4 meters, and the maximum width is more than 8 meters. The production line speed is high, and the speed of certain types of lines can be up to 300 meters or more. The entire line is highly automated. Control systems such as temperature, speed, pressure, tension, and thickness control in the production process are all centralized and digitally controlled.
Biaxially-stretched synthetic paper has a large investment in equipment, but the products produced by this method are widely used, and various products can be developed according to different uses to suit printing or packaging fields.
The equipment for the production of biaxially stretched synthetic paper is mostly based on BOPP equipment and modified to suit the production of synthetic paper. In order to fully embody the plastic characteristics of synthetic paper and the printing characteristics of paper, to produce better synthetic paper, the performance requirements for the equipment will be higher.
1, to send batching system, to be flexible, accurate measurement, uniform mixing, there can be no dead ends, exhaust emissions should be sufficient.
2. Extrusion system needs to add special exhaust device to improve the exhausting capacity. The plasticization needs to be sufficient. The extrusion pressure should be high and stable. The temperature rise of the material should be too low, and the temperature control of the barrel tube must be accurate and sensitive.
3, the die must be a multi-layer synthesis, to meet the close and uniform lamination, smooth.
4. The vertical and horizontal stretching machine needs precise speed control, and the tensile driving capacity needs full height requirements.
5, surface treatment devices to achieve a higher level.
6, the winding system tension, speed control accuracy is higher.
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