BIAXIALLY ORIENTED TUBULAR BLOWN FILM STRETCHING MACHINE BY ISOSTATIC PRESSURIZED WATER

Abstract

Biaxially oriented tubular blown film stretching machine by isostatic pressurized water is a simultaneous biaxial stretching process, invented to stretch a high crystalline tubular blown film substrate with heterophasic structure to form a microporous film substrate, especially for microporous polypropylene film. The system comprises sequential sets of variable speed nip rolls, a temperature control water tank, and a water pump unit. The sequential sets of variable speed nip rolls used to stretch the tubular blown film substrate in machine direction, while hot water is pumped and confined inside the tubular blown film substrate creating an isostatic pressure in bubble, lead to an orientation stretching in transverse direction.

Claims

1. A biaxially oriented tubular blown film stretching machine by isostatic pressurized water is a simultaneous biaxial stretching process, wherein the substrate to be stretched is a continuous tubular blown film substrate, the system comprising: a plurality of sequential set of variable speed nip rolls; a temperature control water tank (5); and a water pump unit (7).

2. The biaxially oriented tubular blown film stretching machine by isostatic pressurized water according to claim 1, wherein the sequential sets of variable speed nip rolls comprising at least 4 sets of nip rolls (1), (2), (3), (4).

3. The biaxially oriented tubular blown film stretching machine by isostatic pressurized water according to claim 1, wherein the first set of nip rolls (1) is installed at the outside of the water tank (5), preferably on the top beside the water tank (5).

4. The biaxially oriented tubular blown film stretching machine by isostatic pressurized water according to claim 1, wherein the second set of nip rolls (2) is installed in the bottom of the water tank (5).

5. The biaxially oriented tubular blown film stretching machine by isostatic pressurized water according to claim 1, wherein the third set of nip rolls (3) is installed on the top of the water tank (5) in the same center alignment with the second set of the below nip rolls (2).

6. The biaxially oriented tubular blown film stretching machine by isostatic pressurized water according to claim 1, wherein the fourth set of nip rolls (4) is installed above of the third set of nip rolls (3), preferably in the same center alignment with the second set of nip rolls (2) and the third set of nip rolls (3).

7. The biaxially oriented tubular blown film stretching machine by isostatic pressurized water according to claim 1, wherein the outside of the temperature control water tank (5) coupling with at least one set of heater bands (6).

8. The biaxially oriented tubular blown film stretching machine by isostatic pressurized water according to claim 1, wherein the temperature control water tank (5) is contained heated water with temperature in the range of 50 to 100 degree Celsius.

9. The biaxially oriented tubular blown film stretching machine by isostatic pressurized water according to claim 1, wherein the hot water temperature at the uppermost level in the temperature control water tank (5) is higher than the water temperature at the lowermost level in the said tank (5) at least 5 degrees Celsius.

Description

BRIEF DESCRIPTION OF THE INVENTION

[0022] Embodiments of the invention are illustrated by way of example and not by way of limitation in the figures of the accompanying drawings, which are included to provide a further understanding of the invention together with the description served to elaborate the principle of the invention so that it may be more fully understood. In the drawings:

[0023] FIG. 1 schematically illustrates an example of the system of biaxially oriented tubular blown film stretching by isostatic pressurized water.

DETAILED DESCRIPTION OF THE INVENTION

[0024] Accordingly, the present invention is directed to a biaxially oriented tubular blown film stretching machine by isostatic pressurized water is a simultaneous biaxial stretching process invented for stretching a continuous tubular blown film substrate made from a highly crystalline polymer with a heterophasic structure that can be stretched to form a microporous film, especially for a microporous film of polypropylene.

[0025] The biaxially oriented tubular blown film stretching machine according to invention comprises a plurality of sequential set of variable speed nip rolls (1), (2), (3), (4), a temperature control water tank (5), and a water pump unit (7). The sequential set of nip rolls are used for hauling off and stretching the substrate film or bubble, which a fore nip rolls always moving forward with a higher speed than a rear nip rolls behind leading to rearrangement of the polymer chains called crystallization or orientation, which the proportion of final length per origin length is defined as draw ratio in machine direction, which the ratio depends on the rollers speed of the adjacent pair of nip rolls.

[0026] The said machine consists of at least 4 sets of sequential nip rolls. The first set of nip rolls (1) is installed at the outside of the water tank, preferably on the top beside the water tank (5) to feed-in the tubular blown film. The second set of nip rolls (2) is installed in the bottom of the water tank (5), inside the water tank that is used to haul down the tubular blown film substrate and submerged into the water. The third set of nip rolls (3) is installed on the top of the water tank (5) in the same center alignment with the second set of nip rolls (2). The said third set (3) is used to haul up the film or bubble upward. The fourth set of nip rolls (4) is installed above the third set of nip rolls (3), preferably in the same center alignment with the second set of nip rolls (2) and the third set of nip rolls (3) that is used to haul up the stretched tubular blown film during a step of pumping the hot water into the bubble.

[0027] Between each pair of nip rolls, the first one (1) to the second one (2) and the second one (2) to the third one (3), the tubular blown film substrate or bubble is drawn in machine direction. While, the transverse direction drawing occurred only in the interval of the second set of nip rolls (2) and the third set of nip rolls (3). The hot water is heated by at least one set of heater bands (6) that coupled to the outside of water tank (5), is pumped and confined inside the tubular blown film substrate to create an isostatic pressure bubble leading to a simultaneous biaxial orientation stretching in both direction, machine direction and transverse direction. The temperature control water tank (5) is contained heated water with temperature in the range of 50 to 100 degree Celsius, wherein the hot water temperature at the uppermost level in the temperature control water tank is higher than the water temperature at the lowermost level in the said tank (5) at least 5 degrees Celsius. The proportion of final diameter of inflated bubble per origin diameter of tubular blown film is defined as draw ratio in transverse direction. The drawing conditions like draw speed, draw temperature, and draw ratio both in machine direction and transverse direction, are relied on the polymer substrate structure and the final film applications.