Some main problems in surface treatment of the hot

Some main problems of surface treatment of plastic film

at present, the amount of synthetic organic polymer materials such as plastic, fiber, synthetic rubber and so on with petroleum as raw materials is increasing, and is still growing rapidly. However, in practical use, people gradually find that such materials have many surface problems, such as low surface hardness, poor barrier property, difficult printing, difficult bonding, electrostatic generation, poor biocompatibility, etc. these surface problems not only seriously affect the use performance of these products, but also greatly restrict the further expansion of their application market

plastic film is one of the most important uses of plastic, accounting for about 35% of plastic consumption. Due to the large relative surface area of plastic film, its surface problems are more prominent, which are mainly difficult to print, bond, compound, generate fog drops, generate static electricity, etc. At present, the surface treatment technology of plastic film used in industry in China is corona method, but this method has great limitations and is not suitable for many bulk applications. Plasma surface modification technology has been listed in the national "863" plan, but there has been no technical breakthrough so far. The main reason is that the high vacuum required by this technology makes it difficult to become a surface modification technology for bulk industrial products. It is of great significance to solve the problems existing in the existing film products and production, develop high-performance and functional film products, and expand the application market of plastic films

since 1996, the laboratory of surface engineering of organic materials, School of materials, Beijing University of chemical technology, has developed a new continuous production process for preparing hydrophilic/hydrophobic asymmetric plastic films with surface light grafting as the main technical feature through intermittent small-scale, model and pilot experiments. The plastic film products obtained by this new surface treatment technology still have the original hydrophobicity of the film on one side, while the surface polarity can be arbitrarily adjusted according to different needs on the other side until it is completely hydrophilic. Of course, both sides of the film can also be treated at the same time to obtain symmetrical modified products

this technology is applicable to almost all organic plastic films, such as PE, PP, PVC, pet, nylon, etc. The characteristics of graft polymerization make the modified layer and the original base membrane connected by chemical bonds, and the properties are very stable. Among them, the developed "new technology for the preparation of long-term fog free plastic greenhouses", combined with the application foundation and application tests, has passed the pilot test appraisal organized by the Ministry of education, completed the industrial pilot test of the transition from pilot test to industrialization, established a semi continuous production demonstration device and workshop with a treatment width of 2 meters, and completed the preparation for industrial production. The production device can be used as a separate processing production line to process the finished film offline, or the processing unit can be attached to the original film blowing or film drawing production line to directly obtain high-performance or functional film products, with lower investment cost. Using this complete set of technology, the surface of one or both sides of the produced plastic film can be adjusted freely until it is completely hydrophilic; Functional groups or reactive groups, such as acid, alkali, hydroxyl, amino, anhydride, epoxy, etc., can also be introduced into one or both sides of the plastic film according to the applicable scheme for tensile testing of bolt fasteners. This laid a foundation for the development of special plastic films with various novel properties. At present, there are two problems in the actual use of PE, PP, PVC, pet and other industrial packaging films, which are difficult to print and difficult to bond

generally, the film surface should be corona treated before printing, sometimes coated with special primer, and then use expensive special printing ink, so the cost is very high and the printing quality is not good. This technology can introduce hydrophilic groups with strong polarity into the surface of the film, and because the graft chain is connected with the substrate film by chemical bond, the new surface has durability, which can fundamentally change the existing plastic film printing technology. It can not only solve the problem of organic solvent pollution in plastic film printing, but also use traditional water-based inks to reduce costs. For food packaging, in addition to the problems of printing, bonding and heat sealing of the surface or inner layer, the barrier to oxygen, moisture and flavor is the most important index. PE and PP have good barrier to water, but the steel ore continues to hang upside down and aggravates and the downstream demand is poor, resulting in the steel plant's willingness to stop production for inspection and the poor barrier to oxygen; Pet and nylon have high isolation for oxygen, but poor for water; PVDC has good barrier to oxygen and water, but its film-forming property and film-forming strength alone are poor, and the cost is high; PVOH (polyvinyl alcohol) is the best oxygen barrier film, but it is difficult to cook and disinfect because it is dissolved in water. Now, using the single-sided hydrophilic PE, BOPP or BOPET modified film produced by this technology, it is easy to obtain PVDC coating composite film, high-grade food packaging film with both oxygen and water separation by sandwiching PVOH between the two PE films, adhesive free medium-grade food packaging film composed of treated PE or PP and treated pet, high-grade low-cost aluminum-plastic composite film, anti fogging and anti condensation fresh-keeping bag and other new composite packaging films

in addition, paper plastic composite packaging has become the main packaging body of cement, grain, chemical fertilizer and some industrial products and raw materials. However, this composite packaging bag is difficult to separate and reuse, which not only causes new environmental pollution, but also increases the cost. Therefore, there is an urgent need to develop a "green paper plastic composite packaging bag". In 199, Lanzhou Jin'an New Technology Co., Ltd. made a breakthrough in this technology and made a new composite packaging bag of vinylon water-soluble yarn. This technology uses water-soluble polyvinyl alcohol as the adhesive to stick the paper and vinylon yarn together. The inner layer is recycled paper bag, the outer layer is national standard paper bag paper, and the middle is bonded vinylon water-soluble yarn, which is put into water after use. 1. Purpose of battery acupuncture experimental machine: after acupuncture experiments, the safety function of the battery is checked, the polyvinyl alcohol and vinylon are dissolved, so that the paper can be regenerated. However, the product has the disadvantages of poor water resistance and difficult to recycle vinylon. However, the platform for building a good corporate culture has opened up another route in the adoption of new technology, that is, the polyolefin film is hydrophilic modified on one side, and then the film is bonded and compounded with paper with water-soluble adhesive to obtain paper plastic composite packaging materials with high strength, water solubility resistance and aging resistance. After soaking the paper side with water, the paper and polyolefin film will be naturally separated and recycled respectively

at present, there is no industrialized treatment technology at home and abroad, and there is no such series of products in the market. Therefore, this technology has complete independent intellectual property rights. Its popularization and application can not only bring huge economic benefits to enterprises, but also produce huge social benefits today with the increasing awareness of environmental protection