中文
English

Analyze and solve common problems in blowing film

2021-01-08

640.webp.jpg

一、

The raw material


A. Different PE resins have different film transparency. M-PE has higher transparency than LDPE, and LDPE has higher transparency than LLDPE.


B. The transparency of PE with low molecular weight is better than that with high molecular weight

C. Various additives in raw materials, such as lubricants, opening agents and antioxidants, all affect transparency.

D, resin particles contain a lot of water, should be fully dried particles


二、

The processing technology


A. Low melt temperature, incomplete plasticization and poor transparency.

B, extrusion speed, traction speed and temperature matching is not appropriate, so that the surface of the film is slightly uneven, resulting in light scattering.

C, the blowing ratio is too small, the cooling is not enough, all affect the transparency.

D. The cooling speed is not fast enough, the crystal sphere is large, the crystal area is large, and the transparency is poor.

1. The crystal points


The crystal point is caused by the unplasticized polymer particles in the blown film, and the molecular weight of the crystal point is much higher than that of the surrounding PE.


① The raw material resin in the production process is not strictly controlled, resulting in a part of the resin molecular weight is too high, the production can not be plasticized.


② There are many residual catalysts in the raw material resin. Under the high temperature of the cylinder screw of the film blowing machine, the catalyst continues to act and form molecules with high degree of polymerization. Therefore, the selection of raw materials is very important.


③ After a certain period of time, increase the screw speed, improve the melt extrusion pressure, take away the precipitate.


④ Clean the die mouth regularly

2. Poor opening


① raw material opening agent is insufficient. The opening agent is generally inorganic, forming convex points on the surface of the plastic film, to avoid two layers of film bonding.


(2) Lack of raw material smoothness agent. Such as oleic acid amide, etc., after being heated out to the membrane surface, play a smooth role.


③ 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.


④ Too fast traction speed. Should slow down.

3. Films are loose


The thickness of the film is uneven, causing local tightness of the winding.


(2) membrane bubble cooling air ring improper cooling, 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 roller.


(5) When cutting the edge of the cutter, the blade of the cutter is inconsistent and the Angle is inconsistent.


The pressure of the pressure roller is not consistent when rewinding.


The crack of the stability plate is not uniform.

4. Uneven transverse thickness


① die clearance is not uniform, should be carefully adjusted as required.


(2) uneven heating around the head, check whether the air ring is blocked and whether the opening is reasonable.


③ The heater should be checked if the heating around the machine head is not uniform.


(4) the blowing ratio is too large, replace the die head or change specifications.


⑤ The filter screen is damaged and should be replaced on time.


The air inlet hose of the air ring is damaged or twisted, there is a temperature difference or the length is too wide, it should be adjusted and replaced.


The position of the bubble stabilizer is biased toward the center or the opening Angle is uneven, which should be adjusted.


⑧ The clamp pressure is not uniform, the level is not even, should be checked.


9. If there are sundries in the die cavity, resulting in logistics disorder and uneven discharge, the die should be cleaned regularly.


Attending that the melt pressure or temperature is too high or fluctuates too much, resulting in unstable extrusion melt flow, affecting uneven thickness, can adjust the temperature, and improve the extrusion speed.

5. Uneven longitudinal thickness


① Extruder main motor speed fluctuation, such as belt relaxation, should be maintained.


(2) traction roller rotation is not uniform, maintenance of traction device.


The resin temperature is not stable, check the heater.


(4) The height of the freezing line is improper or changeable, and the position of the freezing line should be fixed after adjustment.

6. The membrane is wrinkled


The form of wrinkles is diverse, there are wrinkles that do not stretch, and there are wrinkles that can stretch, longitudinal wrinkles, horizontal wrinkles and so on.


① Equipment factors.

A, the head installation is uneven, to be corrected.

B. The herringbone or traction roller is not aligned with the center of the machine head, so it should be aligned and corrected.

C, the clamp is not horizontal, deformation or tightness is different, to correct.

D. The parallel of each roller is defective. Should be adjusted.


② Process factors

A, bubble deformation, bubble snake, bubble fluctuation, to stabilize the barrel.

B. The open Angle of the herringbone frame is too large, and the open Angle does not adapt to the diameter of the bubble tube, so 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, the winding tension is not constant, according to different winding mode to adjust.

F. Reduce the melt temperature, which can effectively reduce the melt fluidity. It is relatively firm when the die head is extruded, and the uneven film cooling is not caused by the film bubble skew due to the cooling wind fluctuation.

7. Rough film surface


The film surface is not smooth, like ground glass, something produced fine corrugated, uneven.


① The design of die head is unreasonable, and the shaping section is too long.


② the gap of die head is too small, and the melt is broken when extruded. The die head should be adapted to the raw material.


The die temperature is too low, increase the temperature.


④ Insufficient mixing of extruder. Check temperature, screen, etc.


⑤ there are carbonized resins in the die mouth, and the discharge is disorder, and the die head should be cleaned.

8. Blister tube tilt


① the thickness of the two sides of the film is different, and the bubble tube is inclined to the thick side to adjust the thickness evenly.


② The pressure difference between the two ends of the clamp is large, and the membrane bubble tilts to the side with high pressure, so the pressure should be adjusted.


(3) there is a large difference in the amount of cooling air, adjust the air inlet and outlet of the air ring, and clean it up.


The left and right tolerances of the clamping rubber roller should be ground down.

9. Serpentine of membrane bubble


① the position of the bubble stabilizer is improper, and the opening Angle of the herringbone is improper. It should be adjusted to the proper position.


(2) The air volume of the cooling air ring is uneven, and the opening Angle of the herringbone is improper. It should be adjusted to the proper position.


③ The blowing ratio is too large, and the corresponding traction ratio is too small. The film specifications produced shall match the equipment.


(4) the freezing line position is not appropriate, should be adjusted.


Improper adjustment of the die lip gap, uneven discharge, local adjustment or all readjustment is required.

10. Poor handling of corona


When the treatment effect is not good, check the power setting and check whether the electrode is polluted.


(2) part of the leakage treatment, check whether the discharge electrode deformation.


(3) when the treatment is not uniform, the parallelism between the treatment roller and the electrode is bad.

11. Run the wind when winding


(1) the tension of the winding roller is too small, and the film is too loose


(2) the winding tension is not stable.


(3) The axes of each guide roller are not parallel.


(4) the transverse thickness of the film is not uniform.

12. Flowery film surface


(1) The temperature of the fuselage or die mouth is too low


(2) the screw speed is too fast.


(3) the screw temperature is too high or too low


(4) The formula is unreasonable (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 melting resin is too high, which will reduce the longitudinal tensile strength of the film;


(2) the traction speed is slow, the longitudinal direction of the film is not enough, so that the longitudinal tensile strength becomes worse;


(3) the blowing ratio is too large, and the traction ratio does not match, so that the transverse directional action and tensile strength of the film are improved, and the longitudinal tensile strength will become worse;


(4) the cooling rate of the film is too fast.

14. The transverse tensile strength of the film is poor


(1) the traction speed is too fast, the difference with the blowing ratio is too big, so that the longitudinal fibrosis, the transverse strength is worse;


(2) The cooling speed of cooling air ring is too slow.

15. The film smells bad


(1) the resin raw material itself has a peculiar smell;


(2) the extrusion temperature of the molten resin is too high, resulting in the decomposition of the resin, resulting in peculiar smell;


(3) the membrane bubble cooling is insufficient, the hot air in the membrane bubble is not cleared.



share