I. Introduction
Due to the special requirements of the chemical, cement, fertilizer, sugar and other industries for packaging, a considerable number of plastic woven bags must have a waterproof sealing function. At present, there are two types of waterproof sealed woven bags that are widely produced and applied in China: one is an ordinary separate lining film woven bag with an outer woven bag and an inner liner film bag, and the other is a plastic woven cloth. A laminated plastic film laminating bag.
The production equipment and technology of the separation liner film woven bag are relatively simple, the equipment investment is low, and the application is very extensive. The inner and outer bags are separated, the inner bag is a blown film bag, the outer bag is a plastic woven bag, and the inner bag is slightly larger than the length and width of the outer bag. When the material is contained, the bag inside and outside the bag are not easy to handle and are easily damaged. The liner film bag and the outer bag need to be manually packaged together. The inner and outer bags of the bag mouth should be aligned and stitched. The production efficiency is low and the manpower is wasted. The continuous high-efficiency production cannot be carried out. A skilled operator manually sets the bag every day. About 1,000 lines are completed, and about 300 stitches per person per day can be achieved using a hinged sewing machine.
Laminated plastic woven bag production must go through the laminating process, using a laminating machine outside the braided cylinder cloth coated with a layer of plastic film about 0.02~0.04mm thick. When the film is extruded, the film temperature is 300°C. The combination of the film just extruded and the woven fabric is relatively firm by a pair of cooling press rolls, but such a high temperature causes the fabric surface strength to decrease, the elasticity to become small, and the bag surface brittleness. Increased, the bag is easily broken when dropped. Most laminating bags require the coating to be inside the bag and the woven fabric on the outside, which is beneficial to the bag printing and stacking. However, due to the need to go through a manual bag-turning process, the outer coating layer of the bag can be turned inside, so the inversion bag production efficiency is very low. In view of the insufficiency of the above two types of bags, recently a new type of lining film adhesive woven bag with an inner lining film bag and an outer woven bag is integrated.
Second, the structure and performance of lining film adhesive woven bag
Inner liner film adhesive woven bag bottom liner film bag and outer braided tube bag are integrated into one. Its inner liner is a two-layer co-extruded blown film with a thickness of 0.03-0.04mm. The inner layer of the film is a high-pressure low-density polyethylene (LDPE) film outer layer (bonded to the outer braided tube cloth) of ethylene-vinyl acetate. EVA, the main material of the outer woven bag is polypropylene plastic (PP). The heat-melting temperature of EVA plastic is obviously lower than that of LDPE and PP, and there is a certain adhesiveness between the EVA film in the molten state and the unmelted PP woven fabric. It is through the use of this feature of double-layer coextruded film materials that the inner liner film and the outer plastic tube cloth are subjected to a semi-molten state at a suitable temperature through a series of processes (film outer layer melts, film inner layer and outer braided tube cloth Does not melt), press-bonding and bonding as one. The inner film of the bag is a blow-draw stretch film, and the bonding temperature is low (70-90° C.). The physical properties of the inner film and the outer bag are maintained well, elastic, the bag has high strength, and the comprehensive performance is excellent. The bag breakage rate is high. very low. The inner and outer bag heating and bonding process itself plays a better ironing effect on the bag, so that the bag surface is smooth and beautiful, and the appearance quality is good. The liner-bonded woven bag combines the advantages of the performance of the conventional separate liner lining film woven bag and laminating bag, thereby overcoming the disadvantages of both, and is a widely used replacement packaging product. The cost and price of this kind of bag is slightly higher than that of ordinary separate liner bags of the same specification and total amount, but the performance and grade are greatly improved. The bag can be continuously, rapidly, and efficiently produced on the assembly line of the machine, avoiding intermittent and inefficient production methods such as hand-lined liner bags and manual bag turnover, and is suitable for mass production, and has certain promotional value.
Third, production process and equipment
The inner lining film adhesive woven bag production process shown in Figure 1.
Fig.1 Flowchart of Production Process of Lining Film Bonded Woven Bags
As the lining film adhesive woven bag and the common plastic woven bag production process and equipment of the same place (such as plastic flat film drawing machine, cutting machine, printing machine, sewing machine, etc.), for the domestic plastic industry widely used mature technology No explanation is given here; this article focuses on the differences.
The main difference between the production process and the common woven bag production process is that: first, a double-layer co-extruded plastic film is to be produced; and secondly, a double-layer co-extruded lining is produced at the same time as the circular loom produces the plastic braided cylinder cloth. The film is inserted into the braided tube cloth; thirdly, the inner liner film and the braided tube cloth are pressed together in a semi-molten state to bind the inner and outer bags together. The double-layer co-agent blown film unit is a domestically existing technology and has a certain manufacturer, so long as it is selected and purchased. Intimal plastic circular loom and woven bag inner film adhesive machine were recently developed by Gansu Light Industry Machinery Factory. It is a new and innovative plastic machinery new product that has been introduced to the market.
The following products and parameters are available for the production of lining film bonded woven bags with a width of 550~600mm and a length of 900~950mm:
1. Double-layer co-extrusion blown film unit for the production of double-layer blown film. The extruders are SJ65*28 and SJ45*25, respectively. The maximum film width is 750mm. According to the bag width specification, select the appropriate film port diameter. Double co-extruded blow-moulding heads. Double-layer co-extruded film thickness is generally 0.03 ~ 0.04mm (according to user requirements can also be properly adjusted), the blown film capacity can reach 40 ~ 60kg / h or so.
2. In-film plastic circular looms for the production of plastic woven tube cloth with inner film, S-YZ-4-NM bag-inner four-shuttle circular looms are used. This is a new type of machine developed on the basis of the existing ordinary circular loom. While the plastic woven circular knitting machine continuously and efficiently weaves the tubular bag, the plastic lining film is put through the hollow spindle of the circular loom and placed inside the braided cylinder cloth by means of a film laying device, and the woven film with inner liner is produced by lifting and rolling. Cloth roll. The main machine of this machine is controlled by AC frequency converter, which is stable in operation and sensitive and reliable in electrical control. The inner film and outer bag of the woven cloth roll are not discounted. The machine can produce plastic braided tube cloth with inner film, and can also produce ordinary plastic braided tube cloth without inner film, which can be used as ordinary circular loom. The machine automatically inserts the inner membrane into the weaving cylinder cloth and replaces the manual work, which greatly improves the production efficiency. The weaving fabric has a width of 450~750mm, a weft density of 31.5~50 pieces/10cm, a main engine speed of 0~150r/min, a weaving speed of 61~116m/h, and a host power of 4KW. When the weaving cylinder cloth with a weft density of 40*40/10cm is normally produced, the output of a single eight-hour shift can reach 600m. Its production efficiency and speed are no different from those of the ordinary four-spool circular loom.
3, woven bag inner membrane bonding machine, used to heat the inner lining film and the outer braided tube cloth in the semi-fused state, and select the S-NZ-750 woven bag inner film bonding machine. The machine consists of four parts: unwinding, gluing, winding and electrical control. Adhesion part adopts vertical downward traction on the cloth surface, preheating with external heating radiation, process of internal-conduction internal heat-bonding mandrel for pressure and adhesion, and non-contact temperature control and intermediate frequency heating control system for electrical parts, to solve the problem of adhesion Core film heating and precise detection problems enable high-speed, high-efficiency production in the bonding process. The machine adhesive cloth width 450 ~ 750mm, adhesive speed up to 230m/min, intermediate frequency heating power 20kw, frequency 2500HZ, the whole power 40KW. The machine has a high degree of automation, convenient operation and maintenance, low energy consumption, suitable for continuous and efficient production. The bonded plastic braided tube cloth with inner liner film is even and firm, with high strength, flat and beautiful fabric surface, and reliable bonding quality. It is a new type, high-grade waterproof sealing packaging material.
The equipment and technology for lining film bonded woven bags involved in this article were approved by the provincial experts in October 2000. They were popularized by Hainan Dongfang Fuchun Woven Bag Factory and Gansu Province Plastic Woven Bag Factory. Equipment performance is stable, bag quality is guaranteed, and overall reflection is good. At present, the equipment is in the stage of mass production and sales, and has the promotion conditions.
(Author: Gansu Light Industry Machinery Plant)