JP2000025092A - Plural-layer extrusion die and manufacture of plural- layer film - Google Patents

Abstract

PROBLEM TO BE SOLVED: To independently stably control thickness of each layer of a plural- layer film by providing a space between a wall surface of a channel and a channel adjacent to the channel, and incorporating a channel gap regulating means in the space. SOLUTION: A beam-like block 4 for giving a deformation so that second and third thin parts 2, 3 are turned at a first thin part 1 as a center at a cavity side is provided the part 2. The block 4 is formed of a plate-like driver separated at each regulating bolt of a channel gap regulating means 5 like keying of a piano in a die width direction. Thus, since a fine deformation of a channel wall surface is executed in a width direction, a fine thickness control can be resultantly conducted in the width direction. The means 5 adopts a differential bolt type having a main regulating bolt 5a and a sub-regulating bolt 5b having different pitches of their threads. The means 5 is coupled to an end of the driver in parallel with the part 2, and contained in a cavity 9.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention comprises a plurality of flow paths for laminating a molten resin, which are merged to form a plurality of layers of a film (in this specification, abbreviated as "film" including "sheet"). ) And a method for manufacturing a multilayer film using the same, and more particularly, the method includes a thickness adjusting means for adjusting the thickness and the thickness unevenness in the width direction of the multilayer film. The present invention relates to a multilayer extrusion die for continuously extruding a multilayer film having excellent thickness uniformity, and a method for producing a multilayer film using the same.

[0002]

2. Description of the Related Art When a molten resin is continuously extruded from an extrusion die into a film, the thickness of the film is usually controlled. In this control, the gap of the lip land, that is, the gap in the thickness direction of the flow path is changed. In general, the thickness is adjusted by partially changing the flow rate by partially changing the flow resistance of the fluid.

As the method, a method using a choker bar is most often used. Also, a flexible lip system in which a relatively flexible portion is provided on the lip as compared with the entire die has been used quite frequently. In addition, a method of deforming the die lip itself as disclosed in Japanese Patent Application Laid-Open No. 8-52782, and a method of providing an extremely thin thick portion inside as disclosed in Japanese Utility Model Application Laid-Open No. 7-15321 have been proposed. Further, a method of changing the thickness by changing the temperature of the channel wall surface utilizing the temperature-viscosity dependence of the fluid is also common.

On the other hand, to form a multilayer film in which a plurality of layers are laminated, a feed block method of laminating before the die and widening the inside of the die, and a multi-layer film having a plurality of manifolds in the die, widening each layer and then laminating the layers. A manifold method and a combination thereof are used. In particular, a multi-manifold method is used when a flow characteristic difference such as a viscosity difference of a laminated resin is large. In this formation, the improvement in the total thickness unevenness after lamination is performed by the above-described method using the lip after merging and lamination. In order to improve the thickness unevenness of each layer, the above-described control method is provided to each layer by a multi-manifold method.

[0005]

However, when the above-mentioned thickness adjusting method is applied to the formation of a multilayer film, there are the following problems. The choker bar method has a problem in that the fluid penetrates into the slide portion or stays on the flow path, thereby increasing the number of portions where deterioration is likely to occur. In addition, there is also a problem that the seal is weakened by repeated use because of having the slide portion, and leakage to the outside is easily caused.

On the other hand, the flexible lip method is based on the premise that the lip can move freely at the discharge portion at the tip.
A multi-layer die having a junction inside cannot seal with other layers and cannot be used as it is. In addition, the method of deforming the die lip itself has a problem in that the power for deforming the die increases, and there is a problem in the practicality of sealing the end face of the die, a portion generally called an end plate or a side plate because the entire die is deformed.

The method of providing an extremely thin portion inside can be applied to a multi-layer die having a junction therein. However, according to the description in Japanese Utility Model Application Laid-Open No. 7-15321, the distance to the junction is too long. In addition, a relaxation phenomenon occurs in which the thickness changed in the width direction is diffused to the surroundings and becomes dull. Therefore, this distance should be as short as possible, but if the cavity is too close to the tip of the lip, the lip tip of the confluence will also deform when changing the flow path, so that the operation to the target layer is adjacent A problem arises in that the layer affects the layer and the time required to improve the thickness unevenness to a required level becomes long.

Further, the fact that the bolt for pushing and pulling the thin portion extends perpendicularly to the flow path complicates the arrangement of the components in the die, and generally increases the size of the die. This is a major problem in the case of retrofitting existing equipment. Further, in order to obtain a practical thickness change amount, it is often necessary to deform the lip to a point just before plastic deformation occurs, and in the case of regular use, some protection mechanism is required.

The method of changing the channel wall surface temperature is based on the temperature dependence of the fluid viscosity, and cannot be used when the target fluid has a weak dependence. Also, in a multi-manifold type die having three or more layers, there is a problem that it takes time to obtain a desired thickness change because of heat exchange inside.

[0010] An object of the present invention is to improve the problem of using a conventional flexible lip system for adjusting the thickness of a multilayer extrusion die for forming a multilayer film. It is an object of the present invention to provide a multilayer extrusion die capable of independently and stably controlling the thickness of a multilayer film and a method for producing a multilayer film.

[0011]

The above object is achieved by the present invention described below. That is, the present invention includes a plurality of manifolds and a flow path having wall surfaces of a predetermined width facing each other with a predetermined gap formed in a layer of molten resin connected to the manifold, and laminating each layer from the flow path to form a multilayer. In a multilayer die that continuously extrudes into a film shape, at least one wall surface of at least one flow path becomes a center of rotation when the wall surface is deformed.
(1) a thin portion, a second thin portion connected to flow path gap adjusting means for setting an amount of deformation of a wall provided continuously downstream of the first thin portion, and a downstream portion of the second thin portion And a third thin-walled portion for setting the thickness of the layer to be formed, and a space is provided between the wall surface of the flow path and the flow path adjacent thereto, and the space is provided in the space. A first embodiment of the present invention is a multilayer extrusion die containing the flow path gap adjusting means, and a second invention is a multilayer film manufacturing method for manufacturing a multilayer film using the multilayer die. Things.

In the above-described present invention, a space, specifically, a hollow portion is provided between adjacent flow channels, and the space between the wall surface of the flow channel and the wall surface of the hollow portion is made thin to form the first thin-walled portion. Thickness A (m
m), the thickness B (mm) of the second thin portion, the thickness C (mm) of the third thin portion, and the minimum thickness D between the cavity and the adjacent flow path
(Mm) is preferable from the viewpoint of long-term stability adjustment.

[0013]

C ≦ A <4C 2C ≦ B <10C D> 5A As described above, the multilayer extrusion die of the present invention has a stepped surface on the lip land (flow path) surface so as not to cause deterioration of the molten resin. This is a die having a flexible structure similar to the flexible lip method without any gaps.

Hereinafter, the present invention will be described in detail with reference to the drawings.

[0015]

FIG. 1 is a cross-sectional view of a multilayer die showing one embodiment of the present invention, and shows only details of a core portion of a main part.
FIG. 2 is a partial view illustrating the arrangement of the beam-shaped blocks of the driving body in the XX section of FIG.

In FIG. 1, reference numeral 1 denotes a first thin wall portion of a wall surface;
Is the second thin-walled portion, 3 is the third thin-walled portion, 4 is a beam-shaped block, 5 is a flow path gap adjusting means, 6, 6a are fluid flow paths,
7, 7a are manifolds for receiving the molten resin, 8 is a flow path gap, L is the length of the third thin portion, H is the flow path from the downstream end of the second thin portion 2 to the junction or discharge section. Length, A is the thickness of the first thin-walled portion 1, B is the thickness of the second thin-walled portion, C is the thickness of the third thin-walled portion, D is the wall between the cavity 9 and the adjacent flow path 6a. This is the minimum thickness.

As shown in FIG. 1, the die of the present invention is a multi-manifold type multilayer die, and a cavity is formed in one wall surface of the flow path between each flow path from each manifold to the resin merging portion. In addition to the provision of a portion 9, the wall thickness of a part of the wall surface is made sufficiently thin to have a thin-walled flexible structure, and the thin-walled portion is not a uniform thickness as a whole, but has the following three different thicknesses. The feature is that it consists of parts.

First, a first thin-walled portion is provided directly below the manifold 7 as a rotation center of deformation of the flow path wall surface. 1st thin thick part 1
Is a portion serving as a center of rotation when the second and third thin portions described later are deformed, and it is better to form a sharp thin portion in a short range in the channel direction as long as the material strength allows. However, in consideration of the processing cost, it is practical to form a cylinder having a radius of about 5 to 10 mm in the die width direction. No.
The minimum thickness of one thin thick portion 1 is preferably 1 to 4 times the thickness of a third thin thick portion described later.

Subsequent to the first thin-walled portion, a second thin-walled portion subjected to wall deformation is provided downstream thereof. Therefore, the second
The thin portion 2 has a relatively larger thickness than the first thin portion. Its thickness is suitably from twice to ten times the thickness of the third thin thick part 3. This portion serves as a point of action for wall deformation and also plays a role in preventing the thin portion from being deformed to some extent by fluid pressure in the flow path.

Therefore, the second thin portion 2 is deformed on its cavity side so that the second and third thin portions 2 and 3 turn around the first thin portion 1. A beam-shaped block 4 for providing is provided. As shown in FIG. 2, the block 4 is composed of plate-like driving bodies 4a separated from each other by adjusting bolts of the flow path gap adjusting means 5 which will be described later. Reference numeral 4b denotes an engagement hole of the adjustment bolt of the passage gap adjusting means 5. Thereby, the flow path wall surface can be finely deformed in the width direction, and as a result, the thickness can be finely controlled in the width direction.

The passage gap adjusting means 5 includes a main adjusting bolt 5a and a sub adjusting bolt 5b having different screw pitches as shown in the figure.
And is provided in parallel with the second thin-walled portion 2 so as to be connected to the distal end portion of the driving body 4 a and housed in the hollow portion 9. This makes the whole very compact.

If the ratio of the length of the driving body 4a of the block 4 to the distance from the first thin thick portion 1 upstream to the installation point of the driving body 4a is devised, the thrust of the passage gap adjusting means 5 can be adjusted. It can be devised so that the amount of wall deformation can be precisely changed. On the other hand, in order to change the thickness of the film to be formed, the amount of deformation of the thin wall surface is unexpectedly large, and unlike a general flexible lip, the downstream side is restricted, so that the stress increases. For this reason, it is important to select a material and balance the strength of each part. For this purpose, a simulation calculation by the finite element method is useful. Further, for regular use, it is desirable to provide protection so that a thin portion that is difficult to repair or renew does not exceed the elastic limit. In this example, as shown in the figure, a limit portion 9a for determining the adjustment limit of the flow path gap adjusting means 5 is provided on the inner wall of the hollow section 9, and the tip of the flow path gap adjusting means 5 for driving the driving body 4a such as a key tap is provided. ,
Even in contact with this, the thin and thick portions 1-3 do not exceed the elastic limit to ensure protection.

As the flow path gap adjusting means 5 for pushing and pulling the block 4, besides the above-described differential bolt method, a known heat bolt utilizing thermal expansion of a bolt, a method of deforming a piezoelectric element, or the like is applied. it can.

Following the second thin portion 2, a third thin portion 3 having a length equal to or longer than a predetermined length for adjusting the final thickness of a layer formed downstream thereof is provided. The thickness C of the third thin thick portion 3 is preferably a thickness that is easily deformed, but needs to be strong enough not to be deformed by the pressure of the resin flowing through the flow path 6, and is designed according to the resin to be formed. Specifically, the thickness C is preferably about 0.5 to 3 mm in the case of a typical molten resin such as a typical synthetic resin such as polypropylene or polyester.

The length L of the third thin portion 3 is
It is preferable to make the length slightly longer than the first and second thin portions 1 and 2 because stress concentration can be avoided. From these points, it is better to secure the length L of the third thin-walled portion 3 at least about 10 times the thickness C thereof. However, if the length is too long, the deformation due to the internal pressure is apt to occur, and the distance H to the confluence increases. Therefore, it is desirable to select an appropriate thickness and length. When the distance H to the junction is 20 to 60 mm, 10% or more can be secured by changing the thickness.

As shown, the third thin portion 3 is inclined at a predetermined angle with respect to the first and second thin portions 2, 3 which are linearly provided, and is in contact with another flow path 6a. It is provided so as to reach the junction. As a result, the adjustment in the third thin-walled portion 3 becomes uniform over its entire length and becomes effective, and a space such as the cavity 9 for accommodating the passage gap adjusting means 5 can be secured between the passages.
The overall configuration is compact.

When the gap of the flow path 6 is adjusted in the above configuration, the influence of the deformation of the thin wall portions 1 to 3 on the wall surface on the adjacent resin flow path 6a cannot be ignored. When this deformation is large, the thickness of the adjacent layer (the flow path 6a in this example) other than the target layer (the flow path 6 in this example) whose thickness is to be controlled changes. In addition to the thicknesses A, B, and C of each of the thin-walled portions 1-3, the minimum rigidity D between the flow path 6a and the cavity 9 in the adjacent layer is at least five times A, thereby maintaining the overall rigidity balance. It has been found that the influence on the thickness fluctuation of the adjacent layer can be suppressed to a deformation amount that does not cause any practical problem.

According to the structure of the present invention described above, it is possible not only to finely adjust the thickness of the film in the width direction but also to control the thickness independently for each layer without fear of deterioration of the fluid remaining in the flow path. Also, since there is little interference between layers, the time for improving the uneven thickness to a required level hardly extends. Also, there is little leakage of fluid. In addition, it is possible to solve the weakness of the conventional method of providing a thin-walled portion in the inside, that is, a relaxation phenomenon in which a change in thickness becomes broad, and to realize equipment protection of the thin-walled portion.

Hereinafter, examples of the production of the multilayer film according to the present invention will be described.

[0030]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS In the multilayer die of FIG. 1, adjustment bolts are arranged in a staggered arrangement at a pitch of slightly over 40 mm in the width direction. Material is SU
Using S630, the flow path gap 8 is 1.5 mm, the initial gap (opening)
And The thickness C of the third thin-walled portion 3 was 2 mm, and the other thicknesses were such that A: B: C: D was 1: 2: 1: 7. In addition, the length of the first thin thick portion 1 is 10 mm, and the length of the second thin thick portion 1 is
The length of the third thin-walled portion 1 was 15 mm, and the length was 30 mm.

The fluid has a melt flow index of 4
And about 20 polypropylenes were melt extruded. As a result, since there is no step on the flow path, a film with no streaks is extruded, and the thickness adjustment bolt is turned 1.5 times, specifically, the tip of the beam-shaped block 4 is moved by about 400 μm, so that the gap between the flow paths is reduced. 8 changed by about 200 μm, and as a result, the thickness of the layer formed in the flow path 6 could be changed by about 13%. The effect on the adjacent layer formed by the adjacent flow path 6a could be controlled sufficiently independently by about 20% of the thickness adjustment of the flow path 6.

As for the protection of the thin thick portions 1 to 3, the plastic deformation is not applied to the thin thick portions 1 to 3 at all within the upper limit at which the torque is sharply increased by contacting the inner wall limit portion 9a with a thickness of 500 μm or more. Did not wake up.

In the conventional choker bar type die, in polyethylene terephthalate, deteriorating substances accumulate on steps and gaps in the flow path and generate streaks. In the present invention, streaks are generated because there are no steps or gaps. do not do.

Further, if only a thin thick portion is provided inside, for example, when the distance to the merging portion or the discharge portion becomes about 100 mm, even if the opening (channel gap) is 1.5 mm and the width is reduced by 500 μm, the thickness change of several% is obtained. Can not be used for control, but the present invention can be changed by 10% or more. At that time, the influence on the adjacent layer is also at a level at which there is no problem in control, and since each layer can be controlled independently, the time for improving the uneven thickness to a required level hardly extends.

[0035]

As described above, according to the present invention, in the multilayer extrusion die, the first thin-walled portion serving as the center of rotation for adjusting the gap of the flow path of each layer, the second thin-walled portion serving as a driving source for adjustment, and the final gap Using a flexible structure consisting of a third thin thick part,
With a configuration in which a space is provided between the wall surface of the flow path and the flow path adjacent thereto and a flow path gap adjusting means for driving the second thin-walled portion is housed in the space, the overall configuration is compact, and The present invention has realized a multilayer extrusion die in which there is no stagnant portion, the range of adjusting the thickness of the layer to be formed is large, and each layer can be adjusted with good independence. The use of this multilayer extrusion die realizes a production method capable of producing a high-quality multilayer film in which the thickness of each layer is stable.

As described above, the present invention makes a great contribution to the stable production of high quality multilayer films.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view of a main part from a manifold to a flow path according to an embodiment of the present invention.

FIG. 2 is a cross-sectional view taken along the line XX of FIG. 1 and is an explanatory diagram of an arrangement of beam-shaped blocks in a second thin-walled portion (intermediate portion).

[Explanation of symbols]

 1 First thin-walled section 2 Second thin-walled section 3 Third thin-walled section 4 Beam-shaped block 5 Flow path gap adjusting means 6, 6a Fluid flow path 7, 7a Manifold 8 Flow path gap 9 Cavity

Claims (10)

[Claims] 1. A multi-layer film comprising a plurality of manifolds and a flow path having wall surfaces of a predetermined width facing each other with a predetermined gap therebetween for forming a layer of molten resin connected to the manifold, and laminating each layer from the flow path. In a multilayer die that is continuously extruded in a shape, at least one wall surface of at least one flow path is placed on the first thin-walled portion serving as a center of rotation when the wall surface is deformed, and on the downstream side of the first thin-walled portion. A second thin portion connected to the flow path gap adjusting means for setting the amount of deformation of the continuously provided wall surface, and a third portion for setting the thickness of a layer to be formed continuously provided downstream of the second thin portion. A flexible structure consisting of thin and thick parts,
A multilayer extrusion die, wherein a space is provided between a wall surface of the flow path and a flow path adjacent thereto and the flow path gap adjusting means is accommodated in the space. 2. A flexible structure having a thin portion between a wall surface of the flow passage and a wall surface of the space, and a thickness A of a first thin portion is provided.
(Mm), thickness B (mm) of the second thin portion, thickness C (mm) of the third thin portion, and minimum thickness D between the space and the adjacent flow path
2. Each part is provided so that (mm) satisfies the following expression.
A multi-layer extrusion die as described. [Equation 1] C ≦ A <4C 2C ≦ B <10C D> 5A 3. The first thin-walled portion and the second thin-walled portion are provided linearly, and the third thin-walled portion is provided to be inclined with respect to the second thin-walled portion. Multi-layer extrusion die. 4. A plate-shaped driving body having a predetermined length is provided in a direction perpendicular to the second thin-walled portion, and a flow path gap adjusting means is connected to a tip portion of the driving body so as to be parallel to the second thin-walled portion. Claims 1 provided
The multilayer extrusion die according to any one of claims 3 to 7. 5. The multilayer extrusion die according to claim 4, wherein the passage gap adjusting means is of a differential bolt type. 6. The multilayer extrusion die according to claim 5, wherein the adjustment limit of the flow passage gap adjusting means is limited by a wall surface of the space. 7. The multilayer extrusion die according to claim 1, wherein the space side of the first thin-walled portion has a semicircular cross-sectional structure. 8. The length L (mm) of the third thin thick portion is the thickness C
The multilayer extrusion die according to any one of claims 1 to 7, wherein the following expression is satisfied with respect to (mm). [Equation 2] L> 10C 9. The flow path length H from the downstream end of the second thin-walled portion to the junction with the flow path of another layer is 20 to 60 mm.
The multilayer extrusion die according to any one of claims 8 to 8. 10. A method for producing a multilayer film, comprising using the multilayer extrusion die according to claim 1 and controlling the thickness distribution of each layer of the molten resin.