Analyze and solve common problems in blowing film
A, raw material
A, different PE resin, the transparency of the film is different, m-PE transparency is higher than LDPE,LDPE transparency is higher than LLDPE.
B. The transparency of PE with low molecular weight is better than that of PE with high molecular weight
C. Various additives in raw materials, such as lubricants, openers and antioxidants, all affect transparency.
D, resin particles contain a lot of water, should be fully dried particles
Two, processing technology
A. Melt temperature is low, plasticization is incomplete and transparency is poor.
B, extrusion speed, traction speed and temperature are not properly matched, so that the surface of the film is slightly uneven, resulting in light scattering.
C. Too small blowing ratio and insufficient cooling affect transparency.
D. The cooling speed is not fast enough, the crystal ball is large, the crystallization area is large, and the transparency is poor.
1. The crystal points
The crystallinity is caused by the unplasticized polymer particles in the blown film, and the molecular weight of the crystallinity is much higher than that of the surrounding PE.
The raw material resin is not strictly controlled in the production process, resulting in part of the resin molecular weight is too high, which can not be plasticized in the production.
② There are more catalysts left in the raw material resin. At the high temperature of the screw of the film blowing machine, the catalyst continues to act to form molecules with high degree of polymerization. Therefore, the selection of raw materials is very important.
③ After a certain time, increase the screw speed, increase the melt extrusion pressure, take away the precipitates.
(4) Clean the die mouth regularly
2. Poor opening
① The raw material opening agent is insufficient. The opening agent is generally inorganic, forming convex points on the surface of the plastic film, avoiding two layers of film adhesion.
② The raw material is insufficient. Such as oleic acid amide, after heat precipitation to the film surface, play a smooth role.
The processing temperature is too high and the cooling is insufficient, so the processing temperature should be reduced and the air volume should be increased.
The traction speed is too fast. Should slow down.
3. Film relaxation
The uneven thickness of the film causes local tightness of the winding.
(2) Improper cooling of the bubble cooling air ring and uneven cooling.
(3) The membrane bubble is partially cooled before entering the clamp.
④ The die mouth is inconsistent with the center of the traction roll.
⑤ When the cutter cuts the edge, the edge of the cutter is inconsistent and the Angle is inconsistent.
⑥ When winding, the pressure of the roller is inconsistent.
⑦ The stability plate crack is not uniform.
4. Uneven transverse thickness
① The gap between the die mouth is not uniform, and should be carefully adjusted as required.
(2) The heating around the nose is not uniform, check whether the wind ring is blocked, whether the opening is reasonable.
The heater should be checked if the heating is not uniform around the head.
(4) If the blowing ratio is too large, replace the die head or change the specification.
⑤ If the filter is damaged, replace it on time.
⑥ The air inlet hose of the air ring is damaged or twisted, there is a temperature difference or the length is too wide, and it should be adjusted and replaced.
The position of the bubble stabilizer is biased to the center or the opening Angle is not uniform, which should be adjusted.
⑧ The pressure of the clamp is not uniform, the level is not even, should be checked.
⑨ There are sundries in the mold cavity, which cause logistics disorder and uneven discharge. The mouth mold should be cleaned regularly.
⑩ The melt pressure or temperature is too high or too high fluctuation, so as to cause the extrusion flow instability, affect the uneven thickness, can adjust the temperature, improve the extrusion speed.
5. Uneven longitudinal thickness
① The fluctuation of the main motor speed of the extruder, such as slack belt, should be maintained.
(2) The traction roller rotates unevenly. Maintain the traction device.
Resin temperature is not stable, check the heater.
④ If the height of the freezing line is improper or changed, the position of the freezing line should be fixed after adjustment.
6. The film has folds
The form of wrinkle is diverse, have stretch not open wrinkle, also have can stretch open wrinkle, vertical wrinkle, horizontal wrinkle and so on.
① Equipment factors.
A, the nose installation is uneven, to be corrected.
B. If the herringbone or traction roll is not aligned with the center of the nose, it should be aligned and corrected.
C, the clamp is not level, deformation or tightness, to correct.
D, each roll is not parallel. Should be adjusted.
② Process factors
A, bubble deformation, bubble snake, bubble fluctuation, to stabilize the barrel.
B. The opening Angle of the herringbone frame is too large, and the opening Angle does not adapt to the diameter of the bubble tube. The included Angle should be adjusted.
C, improper cooling, should check the wind ring.
D, die mouth gap is not uniform, adjust the thickness uniformity.
E. If the tension of coiling is not constant, adjust it according to different coiling methods.
F, reduce melt temperature, can effectively reduce melt fluidity, when the die head extrusion is relatively strong, do not cause uneven cooling of the film due to the cooling wind fluctuation caused by the film bubble skew.
7. The film surface is rough
The surface of the film is not smooth, like ground glass, sometimes produce fine ripple shape, uneven.
The mold head design is unreasonable, and the shaping section is too long.
(2) The die head clearance is too small, the melt breaks during extrusion, and the die head suitable for the raw material should be selected.
③ The die temperature is too low, increase the temperature.
(4) Insufficient mixing of extruder. Check temperature, screen, etc.
(5) there are carbonized resin in the die mouth, so the die head should be cleaned.
8. The bubble tube is tilted
(1) The thickness difference between the two sides of the film is large, and the bubble tube is tilted to the thick side to adjust the thickness evenly.
(2) The pressure difference between the two ends of the clamping rod is large, and the membrane bubble is inclined to the side with high pressure. The pressure should be adjusted.
③ The cooling air volume difference is large, adjust the air ring into the air, the air out, clean up.
The left and right tolerances of the clamped rubber roller should be ground flat.
9. Membrane bubble snake shape
The position of the bubble stabilizer is improper, and the Angle of the herringbone frame is improper. Should be adjusted to the appropriate position.
(2) Uneven cooling air volume of the air ring, improper opening Angle of the herringbone. Should be adjusted to the appropriate position.
The blowing ratio is too large, and the corresponding traction ratio is too small. The specifications of the film produced shall match the equipment.
The improper position of the freezing line should be adjusted.
The lip gap of the mold is improperly adjusted and the discharge is not uniform. Local adjustment or total readjustment is needed.
10. Poor corona handling
① When the treatment effect is not good, check the power setting and check whether the electrode is polluted.
Part of the leakage treatment, check whether the electrode deformation.
③ When the treatment is not uniform, the parallelism between the treatment roller and electrode is poor.
11. Run while winding
(1) The tension of the winding roll is too small, and the film roll is too loose
(2) The winding tension is unstable.
(3) The axis of each guide roller is not parallel.
(4) the transverse thickness of the film is not uniform.
12. The film surface is glossy
(1) The fuselage or die opening temperature is too low
(2) The screw speed is too fast.
(3) The screw temperature is too high or too low
(4) Unreasonable formula (too much lead salt stabilizer or too much cold resistant plastic agent)
13. Poor longitudinal tensile strength of the film
(1) The temperature of the molten resin is too high, which will reduce the longitudinal tensile strength of the film;
(2) The traction speed is slow, and the longitudinal directional action of the film is not enough, so that the longitudinal tensile strength deteriorates;
(3) If the blowing ratio is too large and does not match the traction ratio, the transverse directional action and tensile strength of the film will be improved, while the longitudinal tensile strength will become worse;
(4) The film cooling rate is too fast.
14. Poor transverse tensile strength of the film
(1) Traction speed is too fast, and the difference between blowing ratio is too large, so that longitudinal fibrosis, transverse strength becomes poor;
(2) The cooling speed of the cooling air ring is too slow.
15. The film smells bad
(1) the resin raw material itself has peculiar smell;
(2) the extrusion temperature of molten resin is too high, resulting in resin decomposition, resulting in odor;
(3) The cooling of the membrane bubble is insufficient, and the hot air in the membrane bubble is not cleared.