China Paper Bags suppliers The multiwall paper valve bags are the most commonly used packaging bag at present. The material is fed from the top valve, which is convenient for filling materials, and the sealing is simple and easy to reduce the filling cost and improve the filling efficiency. After filling the material, the bag body is a cube. For companies with automatic filling machines, valve pockets are the most suitable packaging solution. Multiwall paper bags are mainly used for packaging edible powder, chemical powder, fertilizer, synthetic materials, explosives, grain, salt, minerals and other powdery or granular solid materials and flexible items. The multiwall paper valve bag is generally composed of three layers of kraft paper and optional with a a plastic film with a moisture-proof effect. The outer layer is almost entirely made of imported paper, yellow or white also called kraft and bleached white, and other colors of kraft paper such as carbon black black kraft paper bags are dyed on a dyeing machine. The inner layer of the kraft paper valve is often made of domestic yellow kraft paper. Of course, if some valve pockets have high requirements, imported yellow kraft paper is also used. The interlayer plastic film has a moisture-proof effect. In addition, a layer of film can be coated on the inner layer of kraft paper, that is, the film is covered on the kraft paper, which can also play a moisture-proof effect. In order to ventilate when filling, sometimes a row of micro-holes should be punched on the surface of the multiwall paper valve bags to increase the filling speed, otherwise the gas can not be quickly discharged with the material, which will affect the filling speed. There are two types of valves for kraft paper valve pockets: inward-facing and outward-facing. The material is imported kraft paper. Generally, more outward-facing valve ports are used, and the outward-facing valve ports have better sealing performance. The printing method of the multiwall paper valve bags is basically flexo printing, and if some layouts are simpler, the printing can be done on the bag making machine in 3-4 colors. multiwall paper valve bags are high-grade packaging and eco-friendly, which are more common abroad and are gradually popularized in China.China Paper Bags suppliers website:http://www.sino-topway.com/paper-bags/