JPS6343213B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a transverse stretching apparatus for plastic films.

In addition to film in the narrow sense, the term "film" as used herein includes various film-like or web-like materials such as a film with horizontal slits, a mesh web, and a horizontally parallel body of thread-like materials.

Stretching is a technology that improves properties such as strength, transparency, and gas barrier properties of plastic films to create high added value and enhance performance, but the conventional stretching method generally involves horizontal uniaxial stretching. For processing, the tenter method (clip tenter method in which both edges of the film are held with clips and the film is stretched in the width direction while running in the longitudinal direction) is used. It was based on the tubular inflation method, which applied an expansion force to the tubular film from within. However, in the former method, the heating furnace, clip running mechanism, and other equipment are large-scale and expensive, and in addition, many unstretched portions remain on both sides of the film, which are later removed, which is uneconomical. There were other drawbacks. In addition, in the latter method, the equipment cost is relatively low, but it is difficult to control the stretching, and the stretching ratio and film thickness tend to vary, making it difficult to obtain a stretched product of high quality, high magnification, and high precision. There was a problem.

In view of these circumstances, the present invention is a method for laterally stretching a film using a new method different from any of the conventional methods described above. By means of a stretching mechanism using left and right stretching belts that engage pulleys within a range of less than half a circumference, both sides of the film to be stretched are gripped between each pulley and each belt. The film is stretched by rotating the pulleys in opposite directions and guiding the pulleys along the rotation loci that diverge from each other. This allows for high-quality, high-magnification, and high-precision stretching with a simple structure. To provide a film stretching device capable of obtaining a product and, in this method, particularly eliminating unevenness in the stretching ratio, wall thickness, orientation, etc. of the film after stretching, and improving uniformity of quality. It is something.

Hereinafter, the present invention will be explained with reference to illustrative embodiments.

Figures 1 and 2 show one part of the overall structure of the device of the present invention.
An example will be shown. In this example, the structure is applied to the transverse stretching of a film that is formed into a tubular shape before the stretching process, such as a tubular membrane formed by inflation or a tubular network of a fiber material made by centrifugal spinning. shows.
In these figures, 1 and 1' are a pair of left and right stretching pulleys, 2 and 2' are stretching belts individually engaged with each pulley 1 and 1', and 3, 4, 5,
6, 3', 4', 5', and 6' are auxiliary pulleys for each belt 2, 2', and 7 is a main heating chamber (heating section for stretching treatment) that accommodates these pulleys. By appropriately supplying heating steam or the like from a steam supply source (not shown) into the main heating chamber 7, the film can be heated to a temperature suitable for stretching.

The stretching pulleys 1 and 1' are mounted on drive shafts 1a and 1a', respectively, in a state in which they are arranged at a predetermined interval on the left and right in the same plane in the heating chamber 7, and are interlocked with a drive device (not shown). The pulleys 1 and 1' are connected to each other and are configured to rotate synchronously in opposite directions in the direction in which the original film A fed from above is advanced between the two pulleys 1 and 1'. Then, the stretching belts 2, 2' are symmetrically engaged with the stretching pulleys 1, 1' within a range of half a circumference or less on the lower half side of the pulleys 1, 1'. It is stretched and guided by auxiliary pulleys 3 to 6 and 3' to 6'. In particular, as a structure adapted to tubular film A, the belts 2, 2' are reversed at auxiliary pulleys 3, 4 and 3', 4' located on the left and right upper sides of the stretching pulleys 1, 1'. A loop is formed in such a manner that the stretching pulleys 1 and 1' are engaged with the outside of the circumferential loop. Further, a nip roll 8 for feeding the film is provided above the heating chamber 7.
The tubular film A is flattened and fed between both stretching pulleys 1 and 1', and at this time, auxiliary pulleys 3 and 3' and belts 2 and 2 are placed inside the tubular film A.
By guiding the film A to a state where the film 2' is inserted, the bent edges of both sides of the film A are sandwiched between the belts 2, 2' and the pulleys 1, 1' from the inside and outside. be. Reference numeral 9 denotes a support column for the upper inner pulleys 3, 3', and 10, 10 longitudinally traverse the stretched tubular film at the point where the pulleys 1, 1' and the belts 2, 2' are separated from each other on both the left and right outer sides into front and back divided films. It's a cutter.

These stretching pulleys 1, 1' and belt 2,
2', etc., constitute a stretching mechanism, and furthermore, as shown in FIGS.
A taking-off nip roll 12 as a film taking device is provided at a predetermined position outside the main heating chamber 7 at a certain distance from the turn roll 11 in the film leading-out direction; A heating device for heating the stretched film A' is provided between the turn roll 11 and the taking-off nip roll 12, and the stretched film is passed through these taking-up mechanisms and then taken by a winding device (not shown). It is configured to be rolled up. The above take-out turn roll 11
are arranged horizontally on both front and rear sides of the range spanning both the stretching pulleys 1, 1' in the vicinity of the film take-out position where the stretching pulleys 1, 1' and the belts 2, 2' are separated from each other. It is freely supported and guides the film A' after being stretched and longitudinally cut forward and backward while being in contact with it from the lower surface side over its entire width. Further, the take-off nip roll 12 is located outside with an appropriate distance between it and the take-out turn roll 11 for the film homogenization function described later, and is a pair of upper and lower rolls driven by a drive device (not shown). It is configured to hold the stretched film A' over its entire width and take it off in the longitudinal direction. As a heating device for the stretched film A', for example, as shown in the figure, auxiliary heating chambers 13 are provided on both front and rear sides of the main heating chamber 7 to cover the area from the take-out turn roll 11 to the vicinity of the take-up nip roll 12. 13 is communicated with the main heating chamber 7 to introduce heating steam and the like. In this way, the stretched film is placed between the take-out turn roll 11 and the take-up nip roll 12.
A constant section 14 is formed in which A' is heated and moved while keeping it substantially constant. Reference numeral 15 denotes a sealing member provided at the outlet of the stretched film of the auxiliary heating chamber 13.

FIGS. 4 and 5 show another embodiment of the overall structure, which is applied to the transverse stretching of a flat film. In this embodiment as well, a pair of left and right stretching pulleys 21, 21' are arranged at a predetermined interval in the same plane, and endless belts 22, 22' are provided individually for each pulley 21, 21'.
are arranged so as to engage within a range of half a circumference or less on the lower half side of the pulleys 21, 21', and both pulleys 21, 21' are driven to rotate in opposite directions by a drive device (not shown). That's what I do. however,
In this embodiment, the method of hanging the belts 22, 22' is simplified, and the belts 22, 22 are stretched over the left and right stretching pulleys 21, 21', and the auxiliary pulleys 23, 23' and 24, 24' located above them, respectively. ' is crossed. Also, the belts 22, 2 between the stretching pulleys 21, 21' and the auxiliary pulleys 23, 23'
A film guide frame 25 is placed in the middle of the path where the belts 2' face each other in the plane, and the guide frame 25 allows the flat raw film B to be folded onto both belts 2 and 2' while bending both sides thereof. It is configured to guide the user to a state in which they are aligned. Reference numeral 26 denotes a heating bath for heating the film being stretched, and this heating bath 26 constitutes a heating section for stretching treatment. The lower half is immersed in warm water in the bathtub 26. Also in this structure, as a mechanism for taking out the stretched film, there is a take-out turn roll 31 that guides the stretched film in the lead-out direction over the entire width at a position close to the film take-out point, and a take-out turn roll 31 that guides the stretched film in the lead-out direction from the take-out turn roll 31 at a constant distance a take-off nip roll 32 serving as a take-off device for holding the stretched film across its entire width at a distance of , and taking it off in the longitudinal direction;
A heating device for heating the stretched film B' is provided between them, and the stretched film B' is wound up by a winding device (not shown) through these mechanisms. However, in the case of a flat film, it is not necessary to divide the film after stretching, and the film can be taken out from one side (backward), so the above-mentioned taking-off mechanism may be provided on one side of the stretching mechanism. Further, as a heating device for the stretched film B', an auxiliary heating bath 33 filled with hot water or the first
As in the embodiment, an auxiliary heating chamber or the like into which heating steam or the like is introduced may be provided. Note that as a means for heating the film during stretching, a heating chamber may be formed and heated steam or the like may be used as in the first embodiment.

The operation of the film stretching apparatus constructed as described above will now be described.

When the tubular film A is stretched by the apparatus shown in FIGS. 1 to 3, the flat tubular raw film is fed between the stretching pulleys 1 and 1' through the feeding nip roll 8. The bent edges of both sides of A are connected to each pulley 1, 1' and belt 2,
It is sandwiched in between at the starting point of the contract with 2'.
In this way, both sides of the film A are held between the belts 2, 2' and the pulleys 1, 1' from the inside and outside, while the pulleys 1, 1' rotate and the belts 2, 2' rotate accordingly. Therefore, over the engagement range of belts 2, 2' and pulleys 1, 1', both pulleys 1,
1', the film A is guided and gradually stretched in accordance with the rotational loci that diverge toward each other. Then, as the stretched film is moved near the point where the pulleys 1, 1' and the belts 2, 2' are separated from each other, the cutter 10 cuts both sides of the stretched film in the longitudinal direction, dividing it into front and back films A' and A'. , the divided stretched films A' and A are led out to the outside on both the front and rear sides.

Also, when the flat film B is stretched by the apparatus shown in FIGS.
By inserting the bent portions of both sides of the original film B sent between 1' and 1' between the pulleys 21, 21' and the belts 22, 22', the film is folded as the pulleys 21, 21' rotate. Stretch the pulleys 21, 2
Stretched film B is taken out from the point where 1' and belts 22, 22' are separated.

Such a stretching method has the advantage that the structure of the apparatus is simple and compact, and a stretched product with a high magnification can be obtained at will.

By the way, in this method, both stretching pulleys 1, 1' (or 21, 21') and the belt 2,
2' (or 22, 22') is stretched according to the rotation locus, and from the lowest point of pulleys 1, 1', the film is turned over and continues to be stretched. However, if this is expressed in terms of development, the movement paths of both sides of the film during the stretching process are shown by curves P ₁ and P ₂ in Figure 6, and the average path is shown by the two-dot chain line in the same figure. As shown. In this case, the stretching ratio in the horizontal uniaxial direction is 2.5
If it becomes larger than double, shrinkage force will be generated in the longitudinal direction of the film. Here, there is a difference in the deformation caused by the contraction force between the peripheral edge of the film gripped by the stretching pulley and the central part which is not gripped, and since there is room for deformation near the central part, it contracts and the longitudinal orientation effect is reduced. As a result, the wall thickness also becomes larger than that on the peripheral edge side. Looking at this phenomenon from the film running speed, the film take-out point D-
At point D, as shown by the dotted line DED, the central portion runs later than the both side portions. Therefore, if the film is simply turned and wound from the film take-out point, the above-mentioned unevenness in stretching ratio, wall thickness, orientation, etc. will remain.

However, in the present invention, the above-mentioned problems are solved by homogenizing the film in the above-mentioned take-up mechanism. In other words, the film take-out point D
After -D, in the section 14 having an appropriate length between the turn roll 11 and the take-up nip roll 12, the take-up action and width direction regular action by the take-up nip roll 12 and the heating action by the heating device are performed. In response to this, the stretched film A' (or B') moves while maintaining a substantially constant width.
As a result, the low-stretched parts (thick-walled parts) of the film are additionally stretched and become thinner, and the highly stretched parts are difficult to be additionally stretched, so that uniformity as a whole is promoted. The partial speed delay at the take-out point shown by the DED line is gradually corrected in the section 14, as shown by the dotted lines in FIG. In this way, the stretching ratio, wall thickness, orientation, etc. of the film A' after stretching are corrected. After passing through this section 14, the film is cooled or, if necessary, heat-treated and cooled, and then the film is taken up by a winding device (not shown).
Wind up A′.

In addition, the above-mentioned section 14 for taking over the stretched film
, the take-out turn roll 11 (or 31) and the take-off nip roll 12 located before and after the take-out turn roll 11 (or 31)
(or 32) to maintain the film in a stretched state at an appropriate temperature near the stretching temperature and take it off, thereby making the stretching of the film uniform. A more uniform and wider stretched film can be obtained by providing a more reliable regulating means for keeping the film constant and preventing shrinkage in the width direction of the film.
Several examples of such regulating means are shown in FIGS. 7 to 11.

In the embodiment shown in FIG.
1 (or 31) and the take-up nip roll 12 (or 32), a group of adjacent rolls 41 that can freely rotate and are heated to an appropriate temperature are arranged in a staggered manner, and these rolls 41... ... is configured to guide the stretched film A' (or B') in a bent shape. Thus, each melee roll 41
Because of this, frictional resistance acts on the film A' in the width direction, increasing the effect of keeping the film A' at a constant width.

In the embodiment shown in FIGS. 8 and 9, belt-type take-up guide mechanisms 42 are provided on both left and right sides of the section 14 between the take-out turn roll 11 (or 31) and the take-off nip roll 12 (or 32). There is. This mechanism 42 includes a pair of upper and lower film holding belts 45 and 45', which are stretched over front and rear pulleys 43, 44 and 43', 44', respectively.
The upper belt 45 is fixed to the lower belt 45 by means of a retaining screw 48 or the like installed across a fixed block 46 that pivotally supports the pulleys 43' and 44' for the lower belt and a movable block 47 that pivotally supports the pulleys 43 and 44 for the upper belt. ' is facing under pressure. One pulley 44' is driven in conjunction with the take-up nip roll 2, and the other pulleys 43, 44, 43' are configured to rotate in reverse. In addition, the upper and lower belts 4
The outer surfaces of 5 and 45' are provided with corresponding chevron-shaped unevenness along the longitudinal direction so that they mesh with each other,
During this time, the sides of the stretched film A' (or B') are held. 49... is a back-up pulley that maintains the pressed state of the upper and lower belts 45, 45'. According to this structure, the stretched film A' is reliably kept at a constant width by gripping both sides of the stretched film A' and moving it in the longitudinal direction.

The embodiment shown in FIGS. 10 and 11 uses a caterpillar type take-up guide mechanism 51 instead of the belt-type take-up guide mechanism described above, and has a pair of upper and lower rollers stretched over chain wheels 52 and 52', respectively. Chains 53 and 53', and a number of caterpillar treads 54 and 54' that are separately attached to each roller chain 53 and 53'.
It is equipped with... Then, over a certain range, the upper and lower caterpillar torsos 54... and 54'...
The upper and lower roller chains 53, 53' are rotated in a state in which the roller chains 53, 53' face each other under pressure so that the side edges of the film can be held between them.
55, 55' are guide shoes for the roller chains 53, 53'. In this case as well, the caterpillar type take-up guide mechanism 51 is connected to the take-out turn roll 11 (or 31) and the take-up nip roll 12 (or 3).
2), and the nip rolls are arranged on both the left and right sides in the section between The action of sending the paper to the holder 12 is the same as when a belt-type take-up guide mechanism is used.

As described above, the film stretching device of the present invention has left and right stretching pulleys arranged at a predetermined interval in the same plane, and a stretching pulley for each of the pulleys individually within a range of half a circumference or less of each pulley. With a stretching mechanism using left and right stretching belts that engage, both sides of the raw film fed between the pulleys are held between the belts and the pulleys, with both pulleys rotating in opposite directions. Since the film is stretched by being gripped and guided along the rotation locus of both pulleys that diverge from each other, the structure of the device can be made much simpler and more compact, and equipment costs can be reduced. It can be made inexpensive, and
High quality, high magnification, and high precision drawn products can be obtained.
Moreover, in particular, as a mechanism for taking up the stretched film after the film is stretched by the stretching mechanism housed in the heating section for stretching processing, the stretched film is drawn out over the entire width at a position close to the film take-out point. A take-out turn roll that guides the taken-out turn roll, and a take-off device that grips the stretched film over its entire width at a predetermined position outside the heating section for stretching treatment and takes it in the longitudinal direction at a predetermined position outside the heating section for stretching processing, which is located a certain distance from the take-out turn roll. During this period, the stretched film is heated to an appropriate temperature near the stretching temperature by a heating device disposed outside the stretching heating section in the direction in which the film is taken out, and the film is stretched and taken off. Since a section of a constant length is formed in which the film is moved while maintaining a constant width, unevenness in the stretching ratio, thickness, orientation, etc. of the film at the film take-out point of the stretching mechanism is corrected in the above section, and the stretched product is The uniformity of quality can be further improved significantly.

[Brief explanation of the drawing]

Fig. 1 is a perspective view showing one example of the overall structure of the device of the present invention, Fig. 2 is a partial perspective view of the device in use, Fig. 3 is an enlarged longitudinal sectional view of the main parts of the device, and Fig. 4 5 is a perspective view showing another example of the overall structure of the device of the present invention, FIG. 5 is an enlarged side view of the same device, FIG.
8 is an enlarged longitudinal sectional view showing another embodiment of the film take-up mechanism, FIG. 9 is an enlarged longitudinal sectional view showing still another embodiment of the film take-up mechanism, and FIG. Enlarged sectional view of the part along the line, 1st
FIG. 0 is an enlarged view of a main part showing yet another embodiment of the guide portion of the film take-up mechanism, and FIG. 11 is a sectional view taken along the line XI--XI of FIG. 10. 1, 1', 21, 21'...Stretching pulley, 2,
2', 22, 22'...Stretching belt, 11, 31
... Take-out turn roll, 12, 22... Take-off nip roll, 13, 33... Stretched film heating device.

Claims (1)

[Scope of Claims] 1. Two stretching pulleys on the left and right that rotate in opposite directions and are arranged in the same plane with a predetermined interval, and each of the pulleys is individually engaged within a range of half a circumference or less of the pulley. The left and right stretching belts are arranged in such a manner that both sides of the film fed between the two pulleys are held between each pulley and each belt, and the two pulleys are spread out from each other. Consists of a stretching mechanism that horizontally stretches the film by guiding it along a rotation locus in an arc range,
This stretching mechanism is housed in a heating section for stretching processing consisting of a heating chamber or a heating bath, and the stretching mechanism is placed at a position close to the film take-out point where the pulleys and belts are separated from each other on both sides or one side of the stretching mechanism. A take-out turn roll that guides the finished film in the take-out direction over its entire width; and a take-out turn roll that guides the stretched film across its entire width at a predetermined position outside the heating section for stretching processing that is a certain distance away from the take-out turn roll in the take-out direction. A taking-off device for holding the film and taking it off in the longitudinal direction is provided, and the stretched film is heated by a heating device disposed between the take-out turn roll and the taking-off device outward in the direction in which the film is taken out of the heating section for stretching treatment. What is claimed is: 1. A film stretching device characterized in that a film stretching device is provided with a certain section in which the film is moved in the take-off direction. 2. Claim 1, wherein a group of a plurality of adjacent rolls is provided in the section between the take-out turn roll and the take-off device for contacting the stretched film and guiding the stretched film while suppressing shrinkage in the width direction. The film stretching device described in 2. 3. A belt-type take-off guide in which both ends of the stretched film are gripped by a pair of upper and lower endless circulation belts arranged along the film take-up direction on both left and right sides of the section between the take-out turn roll and the take-off device. A film stretching apparatus according to claim 1, wherein a mechanism is provided, and the corresponding surfaces of the upper and lower belts are formed to have uneven cross-sections in the width direction, and the upper and lower belts are caused to run in synchronization in a state where they are meshed with each other. . 4. A caterpillar-type take-up guide mechanism is provided in the section between the take-out turn roll and the take-off device, in which a pair of upper and lower caterpillars for gripping both side ends of the stretched film are arranged along the film take-up direction. A film stretching device according to scope 1.