Present situation of plastic woven bag production technology

plastic woven bag refers to polypropylene, polyethylene resin as the main raw materials, extruded, stretched into flat silk, and then woven, bag made of products.

In the 1930s, H.Jaeque invented a new technology for the production of cutting fiber (flat wire) and split film fibers through his research on the stretching of polyvinyl chloride films. In the 1950s, 0.B.Rasmussen developed woven fibers using thin film extrusion methods and stretching equipment. In 1965, Europe began to industrialize the production of unidirectional stretch flat yarn for the production of woven bags for industrial packaging. Since the development of flat silk woven bags in 1966, the rapid development of products has formed a variety of colors and varieties, complete specifications and sizes of the series of products, a large number of industrial and agricultural product packaging, construction packaging, food packaging and other aspects, the quality of varieties has reached the same level of foreign, class products, in the international market has a certain competitiveness.

Feedstock proportioning process

According to the quality requirements of customers, different raw materials can be selected. However, if it is for food, it is not allowed to use recycled materials, and it is appropriate to add no more than 8% of the filling masterbatch. Under normal circumstances, the maximum amount of recycled material should be added to 30-40%. The addition amount of filler masterbatch is 10-15%, and more than 20-25% will cause the relative breaking force of flat wire to be lower than the national standard GB/T8946 requirements. The tensile strength of the flat wire decreases gradually with the increase of the filling amount of the filler masterbatch. This is because the main component of the filler masterbatch is calcium carbonate. After a small amount of the filler masterbatch is added, it is dispersed in the gap of the polyolefin polymer chain, which has little effect on the tensile strength of the flat wire, and the stiffness of the flat wire is improved. When the addition amount exceeds 20-25%, the excess filler masterbatch occupies the position of the polymer chain, thus hinding the elastic deformation of the polymer chain, so that the polymer chain can not be fully stretched under the action of longitudinal external forces, affecting the tensile orientation of the polymer chain, resulting in the strength and stiffness of the flat wire significantly decreased, and the relative breaking force of the flat wire is lower than the provisions of the national standard GB/T8946.

Mixing process

When mixing old and new raw materials, special attention should be paid to the uniformity of mixing, and raw materials with similar melting index should be selected as far as possible. If the melting index of raw materials is too large, the melting temperature is too large, and the plasticization can not be uniform at the same time in the plasticization extrusion process, which will seriously affect the stretching, resulting in a decline in the quality of flat wire, while the breaking rate and scrap rate are high, and even cannot be produced. In the mixing process, also pay attention to the drying time and temperature of raw materials.

Drawing process

Drawing process is the most critical link in the production of plastic woven bags, which has a huge impact on the quality of woven bags. The wire drawing process is as follows: after the raw material enters the extruder, after the barrel heating and the mutual shear between the screw and the barrel, it becomes molten in the state of almost complete plasticization, extrusion into a film through the die molding, cooling, cutting into embryo wire with a blade, and stretching into a flat wire through the oven; The flat wire is thermally shaped, contracted at low traction speed, treated at low temperatures, and finally rewound by a winder system. There are two kinds of film forming methods: tubular film method and flat film method. At present, flat film method is the most used method. The cooling methods after film formation are air cooling, water cooling and intercooling, and water cooling is the most used method at present. Draft heating methods include hot plate, hot roll, hot air, hot plate is used more at present; There are concentrated cycloidal winding, single ingot torque motor winding, magnetic torque winding and CAM combined energy-saving winding machine, CAM combined energy-saving winding machine is used more at present.

Braiding process

Weaving process is the process of weaving the warp and weft yarn into cloth through the circular loom. The weaving process of plastic woven bag is: hanging yarn - threading yarn - boot - lifting - winding - unwinding. First, the warp is drawn from each row of spints on the warp frame, and the porcelain hole of the warp frame - control - long vertical plate - wire roller - warp guide roller - wire guide roller - the second long vertical plate, - wire guide roller - porcelain hole - tension rod - brown wire and a round steel buckle must be reserved through the ring. The weft yarn is loaded into the shuttle store, and after the machine is started, the shuttle moves in a circle under the push of the shuttle pushing device, and the warp supply system and the shuttle pushing device are closely matched to weave the cylindrical flat fabric. The braided fabric is pulled upward by the traction device at the top of the loom, and after passing through the guide roller, it is wound by the winding device behind the warp frame. When the diameter of the winding coil reaches about 1.2 meters, it is unrolled and sent to the next process (usually once every 24 hours).

Printing cut

The qualified woven fabric produced in the previous process is printed on the woven fabric by the printing press, and then the bag cutting machine (cutting machine) cuts to the size that meets the customer's needs. The cutting edge is not allowed to appear loose edges, and the national standard does not specify the requirements for printing. Enterprises should formulate corporate printing standards according to user requirements, and consider their own printing equipment types, classes, printing ink types and printing capabilities. Since most enterprises use letterpress printing, enterprise printing standards can be formulated with reference to the relevant standards and requirements of letterpress printing. In the production of plastic woven bags for food, special attention should be paid to the control of solvent residue of ink, priority should be given to water-based ink, followed by products of bisphenol components, to minimize solvent residue.

sewing

The cut woven cloth is made into a plastic woven bag with a sewing machine (sewing machine). In the national standard GB/T8946, the tensile load of seam side and seam bottom direction is defined. The main factors that affect the stitching strength are the variety and model of the suture, the size of the needle distance, the stitch, the size of the rolled or hemmed suture to the edge of the bag, and the way of cutting. The sewing thread used for stitching is executed according to the national standard GB/ T6836-2007.

inspect

The inspection of plastic woven bags is carried out in accordance with the national standard GB/T8946.