Polypropylene bottle
DATE：2022/12/5 10:03:30 / READ： / SOURCE：This station
Polypropylene bottle
(1) PP resin with melt flow rate of 0.5~2g/10min is selected as raw material for extrusion blow molding of polypropylene bottle. For example, B4901, B4220, B205, B200 and EP-Q30R, Q30P, S30Q and other PP resins produced by Sinopec Beijing Yanshan Petrochemical Co., Ltd. and Fushun Petrochemical Company can be extruded into blow molded medical infusion bottles or plastic bottles for general purposes.(2) Equipment conditions
① The extruders are ordinary single screw extruders specially used for extruding PP materials. The screw diameter shall be selected according to the amount of material used for forming bottles. Generally, the diameter of the screw is 45mm or 65mm, the length diameter ratio is - 20:1, and the compression ratio is (3-4): 1.
② The blank tube mold for forming bottles is used for extrusion blow molding. The blank tube mold structure for forming bottles is mostly the right angle side feeding mold structure as shown in Figure 11-6; If the amount of material used for forming the hollow container at one time is large, the blank tube forming die structure with storage cylinder can be used, as shown in Figure 11-7.
(3) Forming process
① The process temperature shall be controlled within the range of 170~230 ℃ when the raw materials are plasticized and melted.
② The blow ratio of bottle products for blank tube blow molding shall be controlled within the range of (1.5~3): 1.
③ The pressure of compressed air used for forming bottle products with bulging blank tube is 0.3~0.6MPa.
④ The mold temperature for forming bottle is 20~50 ℃, and the cooling and setting time accounts for 50%~60% of the total time of the product forming production cycle.
(4) Quality requirements The quality requirements of bottle products are: the surface of the products is smooth and clean, and the products are inspected in the sun without color difference, discoloration, uneven color and other defects; After the bottle is filled with water, screw the lid tightly, and fall from a height of 1.2m for three times without damage or crack; Health indicators shall comply with GB9688-88 (see Table 5-26).
The production process sequence of extrusion, stretching and blow molding of polypropylene plastic bottle is different from that of extrusion and blow molding of polypropylene plastic bottle in that the blank tube extruded from the mold at the front of the extruder is first fused at the bottom, then heated to a temperature suitable for stretching and blow molding, moved to the mold of the molded product, and longitudinally stretched under the action of internal (stretching mandrel) or external (stretching clamp) mechanical force, At the same time or after stretching, blow compressed air to expand the blank tube (i.e., stretch radially) to form bottle products. As shown in Figure 11-8, the production process of extrusion, stretching and blow molding plastic bottles is shown.
The extrusion, stretching and blow molding of plastic bottles are divided into one-step molding and two-step molding. One step molding is a continuous process of extrusion, stretching and blow molding on one equipment. The products formed by two-step method are the products that are transferred to another equipment (or another place) for heating, stretching and blow molding after the raw materials are plasticized by the extruder to form the blank tubes.
In the production process of extrusion, stretching and blow molding of plastic bottles, after the molecules are rearranged and oriented after biaxial stretching, the impact toughness, low temperature strength, rigidity and barrier property of the products have been significantly improved, the transparency and surface gloss have also been improved, and the wall thickness of the products has also been reduced, which not only saves raw materials, but also reduces the production cost of the products.
Most polypropylene small plastic bottles are thin-walled. It is mainly used for packaging of food, beverage, cosmetics and daily chemical products.
Key points of process operation are as follows.
① The raw materials used are the same as those used for extrusion blow molding of polypropylene bottles.
② The extrusion molding equipment for the blank tube before forming the polypropylene bottle is the same as the extrusion blow molding equipment for the polypropylene bottle, but after forming the blank tube, there should be neck making and back sealing processes for the blank tube.
③ The plasticizing and melting temperature of raw materials should be controlled within 210~230 ℃; The melting material temperature should be rapidly cooled down to the crystallization temperature range of 90~105 ℃ to inhibit the formation of large volume spherulites when forming billet tubes.
④ The preform tube heating, forming bottleneck, back sealing and cutting are the preform processing procedures before the forming and stretching of bottle products; Then stretch and blow mold the product.
⑤ Before stretching, the preform is heated to between the glass transition temperature and the melting point temperature of the raw material, and the polypropylene resin is 145~155 ℃; The stretching work can be carried out only after the temperature of each part of the bottle body is consistent and the heating is uniform.
⑥ During stretching and blow molding, the stretching mandrel is inserted from the mouth end to the bottom of the bottle to stretch and blow compressed air into the bottle preform to complete the stretching and blow molding of the bottle preform.
⑦ The ratio of bottle preform for stretch blow molding is an important process condition to improve the properties of products. This ratio is the product of two ratios of the stretching ratio and the blowing ratio. Generally, the stretching ratio of PP products is controlled within the range of 6~10. The drawing ratio refers to the ratio of product length to preform length; Blowing ratio refers to the ratio of the maximum diameter of the product to the diameter of the preform. The tensile ratio of PP products is (1.5~2.5): 1; The inflation ratio is (3~5): 1.
⑧ The stretching clamp is used for clamping the two ends of the blank tube, and is an indispensable auxiliary tool before stretching and inflating products.
Author：admin