The main process principle of stone paper
is to use professional milling equipment to grind limestone, calcite, marble, etc. into powder. Through special processes, the stone powder is mixed with polyethylene and cement. It is reported that stone papermaking technology has been successfully developed in China in the 1970s. At present, China has more mature stone papermaking technology with independent intellectual property rights, and its stone powder usage rate can reach 80%.
It is reported that there are mainly three kinds of production processes for environmental protection paper such as stone paper.
The first is calendering. That is, through the batching, mixing, modification, extrusion molding, rolling. The disadvantage of the calendering process is the complexity of the process. It is generally used to produce environmentally-friendly 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.
Followed by the casting method. Instead of a calendar, a casting machine can produce green papers of various thicknesses. However, there is a one-way distribution of the molecular chains in the environmental protection paper, so the vertical, horizontal, and physical properties of the environmental protection paper products are greatly different, which is a major drawback of the cast environmental paper.
The last is the biaxial stretching method. It is reported that in recent years, Taiwan has launched "biaxially-stretched pearl paper". In the process of biaxial stretching, some small gaps will be formed between the plastic and the filler of the substrate, thereby reducing the proportion and costs of environmental protection paper. Because these small gaps form a pearlescent effect on the refraction of light, the produced environmentally friendly paper has a good appearance and has been widely used in the fields of packaging, printing, advertising, and so on.
Industry sources said that compared to the use of trees as papermaking raw materials, stone materials have great advantages in terms of environmental protection and cost, but the initial investment in equipment is large, the initial investment is high, and the scope of stone paper
products is still limited; In the long-term, with the further improvement and maturity of stone paper technology and the decrease in the cost of supporting equipment, stone paper technology should play an important role in the paper industry.