Process for forming film
View Patent ↗A method of making and using a stretchable film includes an extruding operation where molten plastics materials are extruded into a tube and a blowing operation in which the tube is blown to expand a diameter of the tube and form a blown-film tube. The blown-film tube is slit to form a film sheet that may be deformed elastically in a machine direction.
1. A method of making and using a stretchable film sheet, the method comprising the steps of
extruding a tube made of plastics materials including polyvinyl chloride,
blowing the tube to establish a blown-film tube having a first temperature and a first length,
flattening the blown-film tube with a nip roller,
heating the flattened blown-film tube to provide a heated-film tube,
elongating the flattened heated-film tube by applying force to the heated-film tube in only a first direction to provide a machine direction oriented-film tube having a relatively greater second length,
cooling the machine direction oriented-film tube,
slitting the machine direction oriented-film tube to provide a flattened machine direction oriented stretchable film sheet having twice the width of the machine direction oriented-film cooled-film tube, and
deforming elastically the stretchable film sheet in a second direction transverse to the first direction,
wherein during the heating and elongating steps:
the blown-film tube is flattened around a nip roller maintained at a first temperature and moves around the nip roller at a first feed rate,
the flattened heated-film tube is passed around a second roller at a second temperature and moves around the second roller at a second feed rate, and
the flattened heated-film tube is passed around a third roller at a third temperature and moves around the third roller at a third feed rate,
wherein the second feed rate is greater than the first feed rate and the third feed rate is greater than the second feed rate, and
wherein the third temperature is greater than the first temperature and the second temperature is greater than the third temperature.
2. The method of claim 1 , wherein the second roller heats the flattened blown-film tube to the second temperature and the second temperature is above a softening temperature of the plastics materials including polyvinyl chloride.
3. The method of claim 2 , wherein the second temperature is a temperature in a range of about 120 degrees Fahrenheit to about 125 degrees Fahrenheit.
4. The method of claim 1 , wherein the heated roller is heated to a temperature in a range of about 100 degrees Fahrenheit to about 220 degrees Fahrenheit.
5. The method of claim 1 , wherein the heated roller is heated to a temperature in a range of about 120 degrees Fahrenheit to about 200 degrees Fahrenheit.
6. The method of claim 1 , wherein the heated roller is heated to a temperature in a range of about 120 degrees Fahrenheit to about 160 degrees Fahrenheit.
7. The method of claim 1 , wherein the elongating step is performed while the heated-film tube is at the second temperature.
8. The method of claim 7 , wherein the elongating step occurs during the heating step.
9. The method of claim 7 , wherein the elongating step occurs after the heating step.
10. The method of claim 1 , wherein the first direction is a machine direction.
11. The method of claim 1 , wherein the second length is in a range of about 20 percent to 200 percent greater than a first length.
12. The method of claim 11 , wherein the second length is in a range of about 50 percent to about 150 percent.
13. The method of claim 11 , wherein the second length is about 50 percent greater.
14. The method of claim 1 , wherein the second length is in a range of about 50 percent to about 100 percent greater than the first length.
15. The method of claim 14 , wherein the first direction is a machine direction.
16. The method of claim 1 , wherein the second temperature is about 119 degrees Fahrenheit.
17. The method of claim 16 , wherein the the second feed rate is about 70 yards per minute.
18. The method of claim 17 , wherein the feed rate is about 88 yards per minute.
19. The method of claim 18 , wherein the third temperature of about 90.6 degrees Fahrenheit.
20. The method of claim 17 , wherein the flattened blown-film tube is passed around a fourth roller maintained at a temperature of about 75 degrees Fahrenheit during the cooling step after being passed around the second roller.
21. The method of claim 20 , wherein the flattened oriented-film tube moves around the fourth roller at a feed rate of about 118 yards per minute.
22. The method of claim 21 , wherein the first temperature is about 75 degrees Fahrenheit.
23. The method of claim 22 , wherein the first feed rate is about 66 yards per minute.
24. The method of claim 16 , wherein the stretchable film sheet is passed around a fifth roller maintained at a temperature of about 108 degrees Fahrenheit after being passed around the second, a third, and a fourth roller.
25. The method of claim 24 , further comprising the step of winding the stretchable film sheet around the fifth roller at a feed rate of about 126 yards per minute.
26. A method of forming a stretchable film sheet, the method comprising the steps of
providing a blown-film tube made of plastics materials having a first temperature and a first length,
flattening the blown-film tube with a nip roller,
heating the flattened blown-film tube to provide a heated-film tube having a,
elongating the flattened heated-film tube to provide an uniaxially machine oriented-film tube having a second length that is greater than the first length and a first width, and
slitting the uniaxially machine oriented flattened film tube in the machine direction to provide a machine direction oriented stretchable film sheet having twice the width of the machine direction oriented flattened film cooled-film tube,
wherein during heating and elongating, the flattened blown-film tube is fed from a nip roller having a first feed rate to a second roller having a second feed rate and to a third roller having a third feed rate during the elongating step,
wherein the second feed rate is greater than the first feed rate and the third feed rate is greater than the second feed rate,
wherein the nip roller is heated to a first temperature, the second roller is heated to a second temperature, and the third roller is heated to a third temperature, and
wherein the third temperature is greater than the first temperature and the second temperature is greater than the third temperature.
27. The method of claim 26 , wherein the second temperature is a temperature in a range of about 100 degrees Fahrenheit to about 220 degrees Fahrenheit.
28. The method of claim 26 , wherein the second temperature is a temperature in a range of about 120 degrees Fahrenheit to about 160 degrees Fahrenheit.
29. The method of claim 26 , wherein the second temperature is greater than a softening temperature of the plastics materials.
30. The method of claim 29 , further comprising the step of cooling the oriented-film tube to a fourth temperature to provide a flattened cooled-film tube and the fourth temperature is less than the softening temperature.
31. The method of claim 29 , wherein the plastics materials include polyvinyl chloride.
32. The method of claim 26 , wherein the second length is about 20 percent to about 200 percent greater than the first length.
33. The method of claim 26 , further including the step of deforming elastically the stretchable film sheet in a second direction transverse to a machine direction.
34. The method of claim 26 , wherein the elongating step occurs during the heating step.
35. The method of claim 26 , wherein the first, second and third rollers are heated to temperatures in a range of about 75 degrees Fahrenheit to about 130 degrees Fahrenheit.
36. The method of claim 26 , wherein the elongating step includes the steps of applying force to the heated-film tube to establish an elongated-film tube and cooling the flattened elongated-film tube to provide a flattened cooled-film tube.
37. The method of claim 36 , wherein the flattened elongated-film tube is passed around a number of non-heated rollers during the cooling step.
38. The method of claim 26 , further comprising the step of applying a first stress according to ASTM D882 standard_of about 745 pounds per square inch to about 1,210 pounds per square inch to the stretchable film sheet in a direction transverse to a machine direction to cause the stretchable film sheet to have a second width about 50 percent greater than the first width.
39. The method of claim 38 , further comprising the step of applying a second stress according to ASTM D882 standard of about 1,100 pounds per square inch to about 1,625 pounds per square inch to the stretchable film sheet in a direction transverse to a machine direction to cause the stretchable film sheet to have a third width about 100 percent greater than the first width.
40. The method of claim 26 , wherein the stretchable film sheet has an ultimate yield strength in a direction transverse to a machine direction of about 2,704 pounds per square inch to about 3,400 pounds per square inch.
41. The method of claim 40 , wherein the ultimate yield strength is about 2,800 pounds per square inch.
42. The method of claim 26 , wherein the stretchable film sheet has a yield strength in a direction transverse to a machine direction of about 280 to 340 pounds per square inch.