JPS5842016B2 - Method for manufacturing thermoplastic tubular film - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION This invention relates to a method for manufacturing thermoplastic tubular films.

A thermoplastic tubular film is sandwiched between two pairs of nip rollers located above and below, and the film is heated between these rollers to a temperature that allows it to be oriented. It is already known to produce a two-wheel oriented film by simultaneously stretching a tubular film in the longitudinal and lateral directions by adjusting the circumferential speed of the rollers.

It is also known to use a mandrel within the bulge of the tubular film as one method of the above biaxial stretching technique.

It is also known to produce a product as a tubular film without carrying out the above-mentioned stretching operation.

However, in either case, it is unavoidable that unevenness in thickness occurs in the film.

Since this thickness unevenness generally occurs at the same location in the flow direction, the biaxially stretched tubular film is folded and wound on a winder, or the biaxially stretched tubular film is cut in the longitudinal direction and made into strips. In the case of winding it in a winder, or in the case of winding it as a tubular film without biaxial stretching, or in the case of cutting the tubular film without biaxial stretching in the longitudinal direction and winding it into a band shape in a winder, Due to the above-mentioned uneven thickness, annular irregularities (knots) occur on the roll after being rolled up, which deteriorates the appearance of the roll, which also increases walnuts and cracks, significantly detracting from the commercial value.

Therefore, the annular unevenness on the surface of the wound roll, etc.
Technological means have been proposed to reduce film barrels and cracks.

As an example of the proposal, a technique described in Japanese Patent Publication No. 47-47984 was cited.

The method disclosed in the above-mentioned publication is that ``a thermoplastic resin cylindrical thin film kept at a temperature above the softening temperature and below the flow temperature,
After being transferred while being compressed by a delivery pinch roller fixed at a fixed position, a film is placed at a certain distance from the delivery pinch roller and is centered around the center line of the flat folded or cylindrical thin film. The gas is passed between a pair of rotating rollers that are performing reciprocating circular motion over an arbitrary angle in a vertical plane, and then gas is forced into the cylindrical thin film, or the outer diameter of the cylindrical thin film is larger than the diameter of the cylindrical thin film. The cylindrical thin film of thermoplastic resin is expanded in the radial direction by passing it through a core body having a diameter, and is then wound up at a fixed position while being taken up by a pinch roller fixed at a fixed position. Stretching method.

'', which is a technique that is attracting attention as a method for alleviating sagging caused by annular irregularities or thin film unevenness on the surface of a rolled-up roll of stretched film.

In this method, a tubular film that has been folded in two and is heated to a temperature higher than its softening temperature is nipped and moved back and forth, so that blocking occurs on the inner surface of the tubular film. There is a high possibility that problems will occur, and since the tubular film is heated above the softening temperature in a flat state, the stiffness (elasticity) of the tubular film becomes weak.
If the rotation angle is large (for example, 360 degrees), the film will remain twisted by the pair of rotating rollers and will not return to its original position, resulting in double folds (wrinkles), thereby making it impossible to impart a twisting effect to the tubular film. In addition, temperature unevenness is much more likely to occur than heating in a cylindrical expanded state, and placing an oscillator above the stretching zone is particularly important in tubular biaxial stretching equipment where the preheating zone is long. The vertical length will be longer,
Mechanical problems related to heat, such as problems with economic efficiency and operability, the tendency of heated resin to stick to the reciprocating nip roller when the stretched tube is punctured, and the reciprocating mechanism of the roller in a high-temperature atmosphere. There are some technical and commercial issues that need to be resolved.

This invention eliminates the various drawbacks of the conventionally known methods as described above, and provides a film manufacturing method that does not have annular irregularities, film holes, or cracks in rolled-up roll products that are also suitable for manufacturing tubular films that are not biaxially stretched. It is about providing.

In order to facilitate the first solution of this invention, explanation will be given according to FIG.

FIG. 1 shows a typical example and is not limited to the illustrated method.

Figure 1 shows a tubular film formed by reciprocating in the circumferential direction in a plane at 90 degrees to the axis A-A between predetermined positions of the tubular film from the tubular film forming device to the upper nip roller of the biaxial stretching device. After twisting the film, the film is sent to a stretching device. The film is extruded into a tubular shape from an extruder 1, passed through a tubular film forming device 2 consisting of a group of rollers, and then sent out to the outer periphery of a guide roller 2a. A tubular film 4 is held between a pair of driven nip rollers 3 provided on the vertical axis A-A of the contact surface.

The intermediate tubular film held on the axis includes a guide plate 5 and a pair of nip rollers 6 (which may also be guide rollers) arranged in parallel in the lateral direction.

) and - sets of clover rollers 7 (preferably driven).

) and is held by an oscillator 8.

The 1-drive nip roller 3 and this nip roller 6
The nip roller 6 and the clobber roller 7 are simultaneously reciprocated about the axis A-A of the tubular film so that the exit surface of the clobber roller facing the center of the tubular film coincides with the axis A-A.

FIG. 2 shows a side view of the oscillator 8, and FIG. 3 is a detailed view of the guide plate 5, with two opposing guide plates 5.
]-shaped tubular film meandering prevention plate 5a is installed so as to maintain a predetermined gap.

When the nip roller 6 starts reciprocating, the guide plate 5 receives a twisting action between the delivery guide roller 2a of the tubular film forming apparatus and the nip roller 6, and tends to meander over the nip roller. 5 and the meandering prevention plate 5a serve to forcibly guide the surrounding tubular film so that it does not meander.

If the tubular film is forcibly guided, there is a risk that the tubular film will be scratched on the inner surface of the guide plate and the meandering prevention plate. To avoid this, the inner surfaces of these plates should be coated or pasted with a flexible material with a low coefficient of friction. It is preferable to use a group of small diameter rollers.

The tubular film is inflated by gas (air) sealed within the tubular film within the range of travel between the crowbar roller 7 and the driving nip roller 3 of the oscillator.

The tubular film 4' expanded at this portion is rolled up by the oscillation of the oscillator by an amount corresponding to the angle at which it is rolled up.

Since the tubular film below the driving nip roller 3 is expanded, the frictional resistance with the inner surface of the stabilizer plate 9 is large, and if it is not driven, troubles such as meandering of the tubular film are likely to occur, so the nip roller 3 is driven.

Also, in this stabilizer plate, the longer the moving distance of the tubular film between the nip roller 6 of the one-roller type oscillator and the delivery guide roller 2a of the tubular film forming apparatus, the easier the oscillation angle will be.

During this time, the tubular film is twisted by the oscillation of the nip roller without gas being sealed inside the tubular film, so if this moving distance is short, the tubular film tends to enter the nip roller 6 while being twisted.

This tends to cause double folds and wrinkles, making it impossible to impart a twisting effect to the tubular film.

The minimum appropriate length of the moving distance is the thickness of the tubular film,
It depends on the fold diameter, stiffness and elasticity) and the tensile strength of the tubular film.

That is, the greater the thickness, fold diameter, and stiffness, the longer the appropriate minimum distance becomes.

Also, the tension of the tubular film must be low enough to prevent it from sagging.

The tubular film twisted along a predetermined locus curve is pinched by a driving roller 3, passes through a guide roller 10, and reaches a pair of upper nip rollers 12 provided at the upper part of a biaxial stretching device 11.

Although it is preferable that no gas be present in the tubular film during this time, there may be no problem even if a small amount of gas is present.

The tubular film that comes out of the driving nip roller is twisted by an oscillator at the folds made in the tubular film forming device.
Folds are added using a driven nip roller.

This crease does not pose any problem in biaxial stretching. The tubular film that has passed through the upper nip roller 12 is heated to a temperature at which it can be oriented by a heating cylinder 14 between it and a lower nip roller 13 provided at the bottom of the biaxial stretching device.
It is stretched in both vertical and horizontal directions by blowing gas.

In the figure, 15 indicates a roller set stabilizing plate.

In this biaxial stretching process, the twisted tubular film is expanded, so that the uneven thickness of the biaxially stretched film is dispersed in the width direction.

Therefore, the biaxially stretched and folded film is heat-treated in a heat-treating device 16 consisting of a group of rollers, cut in the longitudinal direction with a knife 17, and wound into each winder 18, so that unevenness in thickness and thinness is dispersed. The rolled roll has no annular irregularities (knots) and the appearance of the roll is beautiful, and there are no walnuts or cracks in the film, resulting in a very good product.

FIG. 4 shows a displacement diagram of the change over time in the displacement of the tubular film oscillator caused by the above-mentioned tubular film oscillator.

In the figure, OPS (0operation 5ide)
Fold is an abbreviation for the first fold on the operating side created by the tubular film forming device, and is also an abbreviation for the first fold created on the operating side by the tubular film forming device, and also the E, 0. The signs W and D indicate the expanded film 4'
The arrow O indicates the turning angle of the tubular film.

The arrow → indicates the position of e on the locus curve, and OFF and ON indicate opening and closing of the circuit of the oscillator operating switch.

The tubular film is periodically oscillated following a trajectory curve as shown in the illustrated displacement diagram.

FIG. 5 shows another example of an embodiment in which the tubular film is twisted, and the tubular film sent out from the driving nip roller 3 and the tubular film forming device 2 is placed below the axis A-A of the driving nip roller. It is moved between the provided nip rollers 6 in a swollen state due to the enclosed gas.

In the middle of this moving tubular film, there are
As shown in the figure, the angle roller 7a, which is provided by intersecting two rollers
When twisting the tubular film to the left in the figure, the angle roller at the Y position is placed upward to the right when viewed from the roller side, and when twisted to the right, it is placed upward to the left.

Next, the same effect as the above method can be obtained by continuously and smoothly reciprocating the torsion angle θ from a + (plus) value to a − (minus) value, and then from a single value to a ten value.

When installing the angle roller, the angle θ is determined depending on the twist angle of the tubular film.

In this case, the tubular film can be twisted without oscillating the angle roller mount.

In the above explanation (L), an example was shown in which the tubular film is twisted between the upper nip roller of the tubular film forming device and the biaxial stretching device, but it is not necessarily necessary to twist the tubular film between the above, and the tubular film is twisted in a separate process in advance. It is also possible to use a method in which the tubular film is twisted by applying the above method of twisting the tubular film.

Furthermore, it can be applied to a method for improving the winding appearance and eliminating walnuts and cracks when producing a tubular film that is not biaxially stretched.

In this case, rotary dice are generally used, but
Due to the flow characteristics of the viscoelastic resin, even if the die is rotated, the thickness unevenness is not necessarily dispersed, and furthermore, mechanical and electrical troubles are likely to occur, but these problems can be solved by using this method.

According to the method of this invention, it is possible to twist the tubular film without applying heat, so the twist angle of the tubular film can be increased, and furthermore, when biaxially stretching the tubular film, there is no temperature unevenness. Does not occur.

Additionally, unlike conventional methods, there is no risk of the resin sticking to the nip rollers that make up the oscillator.

In addition, since oscillation occurs at room temperature, there is no mechanical damage caused by the heat of the oscillator.

Furthermore, as mentioned above, the longer the length of the tubular film in the flat state before the nip roller of the oscillator, the larger the twist angle of the tubular film can be.
When biaxial stretching is performed, it can be carried out in advance in a space other than the biaxial stretching apparatus, so that a sufficient length of the tubular film can be obtained.

Therefore, unlike the conventional method of twisting a tubular film within a biaxial stretching device, no restrictions are placed on the stretching device.

Example The resins used were polypropylene M, F, and I.

0.5 (Showa Yuka Co., Ltd. product Show Aroma-8G51
0), with a thickness of approximately 480 microns and a folded diameter of 154 rI
A tubular film of rIft (tube diameter 100 mm) was passed through a tubular biaxial stretching device at a tubular film feed rate of 2.64 rrv'm according to the method shown in FIG.
．． It was stretched 5 times x 5.7 times vertically.

Tubular film torsional angular displacement by oscillator (op
The displacement of the s-fold is 1.57π283 as shown in Figure 4.
°.

When an oscillator was not used, annular irregularities (knots) were generated on the surface of the rolled product when the stretched film had thickness unevenness of 10% or more.

If stretching is carried out under the same conditions and an oscillator is used, even if the stretched film has unevenness of 10 parts or more, there will be no annular irregularities on the surface of the rolled product, there will be no holes or cracks in the film, and there will be no hard rolling. In this case, the hardness was 90° to 100° (rubber hardness tester) across the entire width, with little variation.

[Brief explanation of drawings]

Figure 1 is a recommended manufacturing process diagram for carrying out biaxial stretching according to the present invention, Figure 2 is a side view of the oscillator shown in Figure 1, and Figure 3 is an outline of the guide plate provided on the oscillator. FIG. 4 is a displacement diagram showing the twist angle displacement of the tubular film; FIG. 5 is a diagram showing how the tubular film is twisted by an angle roller; FIG. 6 is an explanatory diagram showing the structure of the angle roller; FIG. 7 is a perspective view taken in the A direction of FIG. 6.

Claims (1)

[Claims] 1 When performing biaxial orientation, heat treatment, and winding in succession following the production of a thermoplastic tubular film, before performing biaxial orientation, the film formed into a tubular shape is expanded in the direction of film travel by gas. A thermoplastic tubular film characterized in that the tubular film is reciprocated in a plane perpendicular to the axis at an arbitrary displacement angle in the circumferential direction to give twist to the film to be transferred, and then biaxially oriented. Manufacturing method.