Polyethylene self-sealing film
DATE：2022/9/30 8:29:46 / READ： / SOURCE：This station
Polyethylene self-sealing film
Polyethylene self - sealing film is a kind of film with special structure in extrusion blow - molding film. The special structure of this film is that there is a convex edge and groove in the finished film with an anchor section, and the performance of the film is exactly the same as that of ordinary polyethylene film. The film packaging bag made of polyethylene self-sealing film, corresponding to the concave and convex grooves like zippers at the opening, a little force can open and close the bag, and can be used repeatedly, but by the swelling force or external pressure of the bag is not easy to open the bag.The ZIPLOCKING PLASTIC FILM BAG MADE OF THIS KIND OF ZIPLOCKING FILM IS NOVEL AND UNIQUE IN appearance, RELIABLE IN CLOSED packaging, NON-toxic, tasteless, ANTI-pollution, and light and convenient, which is very popular among users. This kind of packaging bag can be used to package all kinds of products, such as books, clothing, industrial parts, toys, etc., especially for often open and closed candy, cooked food and all kinds of small food packaging, very convenient, clean and convenient storage.
(1) Raw material selection extrusion polyethylene self-sealing film production molding should be selected packaging grade blow molding PE resin. Generally, high density polyethylene and low density polyethylene resin can be used, and the melt flow rate MFR of the resin is 2~7g/10min. At present, low density polyethylene resin is widely used, such as ZF7B resin produced by Beijing Yanshan Petrochemical Co., LTD., SINOPEC Group, which can produce self-sealing film.
(2) Production mode of plastic self-sealing film extrusion blow molding production mode of polyethylene self-sealing film can be produced by extrusion flat blowing method and extrusion upper blowing method. The production process sequence is exactly the same as that of ordinary polyethylene extrusion blow film.
(3)PE universal single screw extruder, screw diameter according to extrusion blow molding self-sealing film folding size selection, generally used 45mm and $65mm; L/D>20:1, compression ratio of 3: porous plate three layer filter screen mesh number and installation position of 801
100/80. The mandrel of the molding die is a spiral structure. In addition to a buffer groove, the straight section of the discharge port is also provided with a convex edge and groove type material limiting structure that can form a self-sealing film anchor section. Figure 6-30 shows their positions and enlarged shapes.
(a) Position of convex and groove on mandrel (b) Enlarged schematic diagram of convex and groove
Figure 6-30 Convex edges and grooves of the movable plate for the inner mandrel in the mold
Compared with ordinary blown film extrusion molding with the mould structure, as shown in figure 6 to 30 structure shape to determine accurate or not, the self-styled film application of opening and closing the work effect has a great influence, on the part of the brain that structure design and processing should be paid attention to the asymmetry of the rib and groove cross-section shape, so as to adapt to the external force after the self-styled bags closed to open, Internal expansion force or pressure is not easy to open the requirements; Pay attention to the coordination between the gap of the convex edge and groove structure and the gap of the die and the mandrel. It should be able to achieve the same flow rate and flow rate of the molten metal when the molten metal flows through here and the molten metal flow rate at each point on the circumference of the die, so as to produce smoothly and shape the ideal convex edge and groove. Note that this theoretical assumption has high requirements on the mold structure. Due to the influence of raw material properties and extrusion factors, it is difficult to design and process a more suitable mold structure at one time. It should be modified by repeated trials in actual production to achieve the ideal effect.
The selection condition of auxiliary machine is more difficult than that used for extruding ordinary polyethylene film. In particular, the working mode of the cooling air ring has an effect on the forming quality of the convex edges and grooves in the self-sealing film
Generally, 2~3 air rings are needed to cool the membrane bubble; The first traction roller through the herringbone plate before traction is just a guide roller; Convex edges and grooves shall be provided on the clamping traction roller of traction cooling shaping film operation to prevent the clamping force of the clamping roller from making convex edges on the film
And groove deformation.
Extrusion blow molding self-sealing film with auxiliary machines, domestic Dalian East rubber plastic machinery
(4) Molding process Development Co., LTD. And Jiangsu Kunshan Xinzhong Machinery Co., LTD.
(1) The process temperature of each section of the extruder cylinder during raw material extrusion: 110~130℃ in the feeding section, 140~160℃ in the plasticizing section, and 150~170℃ in the homogenizing section. Molding mold temperature :160℃ or so.
② The main process parameters of the extruded polyethylene self-sealing film are the working speed of the screw in the range of 50~100r/min. The draft ratio is controlled in the range of 2~4 times.
Die clearance adjustment should be determined by the thickness of the film and the size of the draft ratio, generally controlled in 1mm.
The blowing ratio of the membrane bubble is different from that of the ordinary polyethylene film. In order to keep the convex edge and groove of the extrusion mold from deformation, the diameter of the membrane bubble can be slightly larger than the diameter of the mouth mold or close to the same. The thickness of the film is mainly controlled by the draft ratio of the membrane bubble.
The choice of the diameter of the molding die is mainly determined according to the size of the folding diameter of the film products, and the general plastic spell out the molding technician's manual
B. The inner pulling force is significantly greater than the outer pulling force.
D. Heat seal strength ≥7N/15mm(according to ZBY28004 standard test)
E Seal pocket should fall not broken, seal does not leak, suspension test sealing is not open
Crack (according to GB10442 standard test).
6.2.14 Linear low density polyethylene film
(1) The application characteristics of linear low density polyethylene film
(1) Linear low density polyethylene film is mainly formed by extrusion blow molding method, but also can choose extrusion ducting method, extrusion coating method, calendering method and two-way drawing method.
Linear low density polyethylene film molding raw materials can be only linear low density polyethylene resin, LLDPE, LDPE or LLDPE, LDPE HDPE several raw materials mixed use, extrusion blow plastic polyethylene film.
③ The tensile strength, impact strength, tear strength, penetration strength and rigidity of linear low density polyethylene film are higher than those of low density polyethylene film. Linear low density polyethylene film has good heat sealing and wide temperature range, but its transparency is slightly lower than that of low density polyethylene film.
(4) LLDPE and LDPE film application selection: if the transparency of the film is high, LDPE film should be selected; if the strength of the film is good, LLDPE film should be selected. In application, the thickness of LLDPE film is 1/4 less than that of LDPE film if the strength of the two films is required to be close to the same.
⑤LLDPE and LDPE resin mixing ratio according to the use of different, there can be a variety of mixing ratio, commonly used mixing ratio M (LLDPE)/ M (LDPE)=70/30 or 50/50 extrusion blow molding film characteristics: blend molding film and LDPE film, because of the strength of the molten material, the membrane bubble operation is stable; The tensile strength and fracture strength of the formed film are enhanced. Under the same conditions, the thickness of the film can be thinner. Compared with LLDPE film, the transparency, surface gloss and fog of the product are improved. The viscosity of the molten material is reduced, and it is easy to form and process. At the same time, the adhesive property of the product film is also reduced.
(2) linear low density polyethylene film uses linear low density polyethylene film and low density polyethylene film uses the same. 404- Die diameter within 0.7~1 times the blown film folding diameter.
(4) The working position of the air ring and the choice of the diameter of the tuyere also have obvious effects on the cooling and shaping quality of the film. Generally, 2~3 air rings are needed for the air-cooled setting of self-sealing film. The diameter of the tuyere in the air ring is about 17~4 times of the diameter of the mouth mold (the small diameter of the mouth mold takes the large value, and the large diameter of the mouth mold takes the small value). The distance between the first air ring and the mouth die is 200~250mm; The distance between the second air ring and the first air ring is 150~200mm(the larger diameter of the mouth die is the larger value, and the smaller diameter of the mouth die is the smaller value).
⑤ At present, there is no standard for the quality requirements and performance indicators of self-sealing film. The mechanical properties of the film can be detected by referring to the physical indicators of ordinary polyethylene blow film, and the mechanical properties of sealing plastic bags can be detected by referring to the following conditions. A. The convex edge and groove are suitable for tightness.
Chapter 6 Extrusion Molding of Plastic Film
(3) film forming process
① Raw material selection choose melt flow rate (MFR) is 0.5~ 4G /10min resin, the application of more value is 1~ 2G /10min. When LLDPE and LDPE resins are blended and extruded for blow molding film, CaCO with a proportion of no more than 3% should be added (CaCO3 should be used after being screened by 300 mesh screen) to prevent film adhesion.
(2) Equipment conditions linear low density polyethylene resin extrusion blow molding film, the use of the extruder and screw structure conditions and requirements of low density polyethylene resin extrusion blow
Selection of equipment conditions for plastic film. Plastic molding film with the same equipment conditions, can refer to the low density polyethylene resin extrusion
③ Process temperature machine cylinder process temperature (from the feeding section to the homogenization section):120~140℃, 150~180℃, 170~210℃. Molding mold temperature :200~215℃. (4) Examples of actual production of LLDPE film (film thickness 0.02mm, using upper blowing method).
A Raw material linear low density polyethylene resin, melt flow rate MFR is 1g/10min. DFDA-1820 of Tianjin Petrochemical Company or DFDA-7042 LLDPE resin of Sinopec Guangzhou branch can be used.
B. The screw structure of extruder should have a new structure form of barrier section and mixing section, the aspect ratio is 25:1, and the mouth clearance of the forming mold is taken as 2mm.
⑤ Process temperature cylinder 160~180℃, 180~195℃, 200~210℃; The connection neck temperature is about 210℃; The molding mold temperature is about 230℃.
⑥ With the air volume film bubble cooling air volume than low density polyethylene film bubble cooling air volume, should be used double tuyere cooling ring, the requirement of blowing to the film bubble to be stable.
(4) Key points of process operation
① The production process sequence of LLDPE resin extrusion blow molding film is exactly the same as that of LDPE resin extrusion blow molding film.
② The blowout ratio of LLDPE resin extrusion blow film should be controlled in the range of 15~2; Die lip gap should be adjusted between 1~2mm.
③ When LLDPE resin is used in extrusion blow plastic film or greenhouse film, the mixture of LLDPE and LDPE resin (mixing ratio is selected according to the application conditions) is more suitable. After mixing, the viscosity of the plasticized melt decreases, and the extrusion plasticizing temperature is 10~20℃ lower than that of LLDPE material. The film runs stably after blowing, and the apparent quality of the formed film is improved.
④ In order to prevent or reduce the rupture of LLDPE material membrane bubble, the resin should be mixed with a small amount of organic fluoride agent (the dosage is 250mg/kg).
⑤ When the thickness of extrusion blow film is less than 0.02mm, LLDPE resin with melt flow rate (MFR) of about 1g/10min should be selected; The melt flow rate (MFR) of the resin used for extruding and casting the film should be higher, in the range of 2~ 5G /10min.
(5) Linear low density polyethylene film quality requirements linear low density polyethylene and low density polyethylene resin mixture produced extrusion blow film (for agricultural use) size and thickness deviation, the standard GB4455-1994 provisions are shown in Table 6-14 and Table 6-15. The reference values of physical and mechanical properties of linear low density polyethylene film and GB/T4456-1996 are shown in Table 6-23. The size and thickness deviation (GB13735-1992 standard) of plastic film molded by LLDPE, LDPE and HDPE resins or two resins mixed are shown in Table 6-24 and Table 6-25. Table 6-23 Physical and mechanical properties of LLDPE polyethylene packaging film Item Standard GB/ T4556-1996 Film without additives (250mg/kg) Film with organic fluorine Tensile strength (longitudinal/mold)/MPa10 23.3/21.5 25.0/21.5 Elongation at break (longitudinal/mold)/%140 1020/1024 1040/1216 transmittance /% right Angle tear strength (longitudinal/mode)/(N/cm) 140 662.2/956.5 914.3/973.2 fog /% 87.7 88 no internal temperature Test film thickness /m0.02 degrees /mm±0.002±0.002±0.002±0,002 ±0.003 superior limit deviation /mm±0.003 ±0.003 superior limit deviation /mm±0.003 superior limit deviation /mm±0.003 superior limit deviation /mm±0.003 superior limit deviation /mm±0.003 superior limit deviation /% qualified product 10 superior average thickness deviation /% first grade product , qualified products ±15±15士15士15 combination density material
And 15
composite
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