JP5280144B2 - Disc filter device and plastic film manufacturing method using the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a disk filter device capable of forming a plastics film which is free from an optical defect by film melt extrusion using a T-die and optically outstanding as well as a method of manufacturing a plastics film using the disk filter device. <P>SOLUTION: The external flow-type disk filter device has a flange 7 which is provided on the molten polymer guide-out port side of a center post 6, and fitted to a casing. Further, the device has a centralized liquid gathering path divided in two parts by the center post 6, and the knife edge-like apex part, of the molten polymer guide-out port side, of the center post 6. <P>COPYRIGHT: (C)2010,JPO&amp;INPIT

Description

  The present invention relates to a disk filter device that filters and removes foreign matters contained in a molten polymer, and a plastic film manufacturing method using the same.

  Conventionally, the disk filter device is widely used for the filtration in the microfiltration of the molten polymer in the final step of the polymerization of the thermoplastic polymer or the melt melting extrusion molding of the thermoplastic polymer into a yarn, film or sheet. It has been.

  This disk filter device has a disk filter element (hereinafter referred to as a filter element) comprising a hub having an outlet for filtrate (filtered liquid) on the inner peripheral surface and a disk-shaped filter medium attached integrally to the periphery of the hub. Is inserted into a columnar center post provided inside the casing and stacked, and the stacked filter elements are integrally tightened and attached to the center post, and the liquid introduced into the casing is filtered by the filter element, and the filtrate ( The filtered liquid) is led out of the casing from a central liquid collection path formed along the center post.

  The disk filter device has such a configuration, and is superior in pressure resistance as compared with the cylindrical filter device, and thus is suitable for filtration of high-viscosity molten polymer and microfiltration. And since it has a large filtration area compared with the volume, it has the advantage that a molten polymer can be filtered efficiently.

  However, depending on the structure of each part of the disk filter device, there is a problem that a part of the molten polymer stays and is thermally deteriorated to generate a gel and mix into the molded product. In order to solve such a problem, for example, Patent Documents 1 and 2 use a filter element having a specific shape in order to prevent the molten polymer from staying at the boundary between the laminated filter element and the casing. In combination with filter elements having different properties, Patent Document 3 discloses that a new flow path is provided in the upper part of the center post to prevent the molten polymer from staying in the disk filter. In order to prevent a die line from being generated due to a difference in the flow rate of the resin in the filter core (center post) and the retention caused by the filter element in which the flow becomes parallel. The resin channel hole of the filter core is evenly divided into two parts. The leaf disk with a filtration accuracy of 15 μm or less is disclosed in Patent Document 9 in which the hole is provided at a specific angle to uniformize the flow of the molten polymer flowing in the core and eliminate the partial retention of the molten polymer. It is a polymer filter (disc filter device) using a filter (filter element), and it is described that the polymer filter (disc filter device) includes a seal ring in the clearance between the center post and the pressing disc.

  Under such circumstances, Patent Documents 6 and 7 describe that a central liquid collection path is formed between the hub and the center post of the filter element. This method (usually referred to as the external flow type) has the advantage that dead space is much less likely to occur than the conventional hollow center post (referred to as the internal flow type). doing.

  However, even with such a disk filter device, it is difficult to provide a plastic film having uniform optical characteristics that can be suitably used for flat displays such as liquid crystal display devices, plasma displays, and organic EL display devices in recent years. there were. In particular, it has been difficult to prevent the occurrence of streaky optical abnormalities in the plastic film.

Japanese Patent Laid-Open No. 9-38423 Japanese Patent Laid-Open No. 9-150018 JP 2008-18598 A JP 2004-237173 A JP 9-174664 A JP 2003-26721 A JP 2001-9214 A JP 2003-170484 A JP 2008-133462 A

  The present inventors paid attention to the fact that the streak-like optical anomaly is a reflection (hereinafter referred to as a weld line) of the molten polymer merging portion (joint surface) in the disk filter device. Accordingly, the present invention provides a disc filter device that not only has a low retention of molten polymer in the disc filter device, but also does not affect the optical properties of the resulting plastic film due to the weld line associated with the fusion of the molten polymer. In addition, the present invention provides a method for producing an optically uniform plastic film free from streak-like optical anomalies due to the appearance of weld lines in a method for producing a plastic film using a T-die using the same.

  As a result of intensive studies in view of the present situation, the inventors of the present invention have made the center post in the external flow type bisect the central liquid collection path, and the tip of the center post on the molten polymer outlet side has a knife edge shape. Thus, it has been found that the above-mentioned problems can be solved by allowing the molten polymer to join together in one straight line, and the present invention has been completed.

That is, the present invention
(1) A plurality of disc-shaped filter elements having hubs are fitted to a center post provided through a flange in the center of the outlet of a cylindrical casing having an inlet and outlet for molten polymer. The inserted and stacked filter elements are integrally clamped together, and the molten polymer introduced into the casing from the inlet is filtered by the filter element, and between the center post and the hub. In the disk filter device that is led to the central liquid collection path to be formed and led out of the casing from the outlet.
A disc filter device characterized in that the central liquid collecting channel is divided into two by the center post, and the tip of the center post on the molten polymer outlet side is formed in a knife edge shape;
(2) The disk filter device according to (1), wherein the cross-sectional area of the center post is gradually reduced toward the molten polymer outlet.
(3) When polymer chips are melted and extruded by an extruder, filtered by a disk filter device, and then extruded from a T-die to produce a plastic film, the disk filter device according to (1) or (2) is used as a center post. The plastic film manufacturing method is characterized in that it is installed such that the direction of the front end portion on the lead-out port side is in the slit direction of the T die. ;
Is a summary.

  In the disk filter device of the present invention, the central liquid collection path formed between the center post and the hub is divided into two by the center post, and the tip portion on the molten polymer outlet side of the center post has a knife edge shape. Since the area where the hub inner periphery and the center post outer periphery come into contact with each other is reduced and the dead space generated on the contact surface can be eliminated, the generation of gel can be prevented. In addition, by forming the center post in the above-mentioned shape, the merged portion of the molten polymer becomes one place and becomes linear, so that the disk filter device of the present invention is used particularly for the production of an optical film by a T-die, and linear When one weld line is mounted so as to be perpendicular to the thickness direction of the film, an optically uniform film can be manufactured which is substantially free from optical abnormality due to the weld line. Have.

Hereinafter, the present invention will be described in detail with reference to the drawings. FIG. 1 is a schematic longitudinal sectional view showing one embodiment of the disk filter device of the present invention. In the following description, the direction in FIG. 1 is referred to as the thickness direction, and the direction perpendicular to the thickness direction is referred to as the width direction. 2 is a front view seen from the width direction of the center post 6 shown in FIG. 1, FIG. 3 is a front view seen from the thickness direction of the center post 6 shown in FIG. 1, and FIG. 4 is seen from d1-d1 in FIG. 5 is a top cross-sectional view as seen from d2-d2, and FIG. 6 is a top cross-sectional view as seen from d3-d3. FIG. 7 is a view showing a cross-sectional shape of a center post of a conventional disk filter device. The present invention is not limited to that shown in FIG.
The disk filter device according to the present invention is connected to the tip of an extruder via a conduit, and is used for the purpose of filtering and removing foreign substances contained in the polymer melted in the extruder cylinder. For example, as shown in FIG. 1, the disk filter device has a plurality of disc-shaped filter elements 3 having hubs 4 fitted into a center post 6 provided in the center of a cylindrical casing 1. The plurality of filter elements 3 are integrally fastened by a fastening tool 2, and the center post 6 is attached to the casing 1 via a flange 7 provided on the molten polymer outlet B side of the center post 6. . The center post 6 and the flange 7 are not particularly limited, but it is preferable to use an integrally molded one.
The fastening tool 2 has an upper surface inclined in a conical shape, and serves as a guide for smoothly introducing the introduced molten polymer.

Next, the shape of the center post 6 of the disc filter device according to the present invention will be described with reference to FIGS. Here, FIG. 2 is a cross-sectional view of the center post 6 shown in FIG. 1 in the width direction, and the center post 6 and the hub 4 are in contact with each other without a gap. 3 is a cross-sectional view in the thickness direction of the center post 6 shown in FIG. 1. The outer diameter of the center post 6 is smaller than the inner diameter of the hub 4, and the space formed therebetween is the central collection. It becomes the liquid path C. Therefore, the central liquid collection path C formed between the hub 4 and the center post 6 has a structure that is divided into two by the center post 6.
Furthermore, in the present invention, as shown in FIG. 3 or FIGS. 4, 5, 6, the cross-sectional area of the center post 6 is gradually reduced toward the molten polymer outlet, so that the flow of the molten polymer that has passed through the filter element 3 is reduced. This is preferable because it can be made smooth and pressure loss is reduced. The shape of the center post 6 is preferably a circular or elliptical fin as shown in FIGS. 4 and 5, etc., but there is no problem even if it is a polygonal shape or a linear shape. There is no particular limitation as long as the central collecting channel C is divided into two. Further, the degree of gradual reduction in the cross-sectional area of the center post 6 can be adjusted as appropriate in consideration of pressure loss.
This eliminates the problem of developing weld lines and gels that are derived from the structure of the center post having a polygonal (triangular, quadrilateral, pentagonal) cross-sectional shape used in the conventional disk filter device.

  As a filter medium constituting the disc-shaped filter element 3, a wire mesh (a metal mesh woven with metal wires), a sintered product thereof, a non-woven fabric made of metal wires, a sintered product thereof, a sintered metal plate, a porous ceramic plate, Examples thereof include a nonwoven fabric made of resin fibers and a woven fabric woven with resin fibers. Among these, a wire mesh and a sintered product thereof are preferable. Examples of the method of weaving the wire mesh include plain weave, twill weave, tatami mat, twill mat weave, and the like. The diameter of the metal wire which comprises a wire mesh is 5-200 micrometers, and the magnitude | size of a mesh is 5-100 micrometers, Especially the thing of 10-100 micrometers is suitable. Examples of the material of the metal wire include stainless steel, copper, a copper-based alloy, titanium, and a titanium-based alloy.

Next, a method for producing a plastic film using the disc filter device of the present invention will be described.
First, the polymer chip is melted and extruded by an extruder. The extruded molten polymer is introduced between the center post 6 and the hub 4 after being introduced into the casing 1 of the disc filter device from the inlet A of the disc filter device of the present invention, filtered through the filter element 3. To the central liquid collection path C. In the disc filter device of the present invention, since the central liquid collection path C is divided as described above, the molten polymer passes through the divided central liquid collection path C, and then at the tip of the center post 6 at the knife edge shape. It merges and is led out of the casing 1 from the outlet B.
At that time, when the direction of the leading end of the center post 6 of the disk filter device is aligned with the slit direction of the T die (the width direction of the film to be described later), the weld line developed by merging is Since it appears linearly in the width direction, the plane weld line is parallel to the obtained plastic film surface (the linear weld line is perpendicular to the thickness direction of the plastic film), and uniform when measuring optical characteristics It is possible to produce a plastic film having excellent optical properties. Also, if there is a slight error in the direction of the tip of the outlet side of the center post of the disk filter device and the direction of the slit direction of the T-die, the weld line is inclined with respect to the film surface. Gels and optical anomalies due to stagnation of the molten polymer at the joint surface with the post knife edge may occur near the film edge, but even in that case, they occur outside the effective width and are removed by trimming. No problem.

  Examples of the thermoplastic resin suitably used in the disk filter device of the present invention include polystyrene resins such as polystyrene, AS resin, and ABS resin, polyolefin resins such as polyethylene, polypropylene, and cyclic olefin, polyethylene terephthalate, polybutylene terephthalate, and the like. Polyester resins such as nylon 6, nylon 66, nylon 12, and MXD nylon, acrylic resins, polycarbonate resins, polyacetal resins, polyphenylene ether resins, polysulfones, and polyimides. The thermoplastic resin is not limited to those exemplified.

  The effects of manufacturing a plastic film using the disk filter device of the present invention will be described below with reference to the following experimental examples.

Each characteristic was evaluated as follows.
<Evaluation method of optical characteristics>
Evaluation was performed using a point light source. Specifically, using a xenon lamp as a light source, a white screen is placed at a distance of 1.2 m from the light source. A plastic film having a width of 1600 mm and a length of 1500 mm is disposed at an intermediate point at an angle of 45 °, and evaluation is made by the shadow projected on the screen. When a streaky optical anomaly is present in the plastic film, a bright portion (appears white) or a dark portion (appears black) appears streaks on the screen compared to the surroundings. In this experimental example, the number of lines and the density of the stripe-shaped part were evaluated.
In addition, it can be said that the optical abnormality is large when the white stripe-shaped part and the black stripe-shaped part are dark, and the optical abnormality is small when the light is light.
<Gel evaluation method>
As a gel evaluation method, evaluation was performed based on the distribution of defects caused by the gel and the number of defects using a transmission type defect inspection apparatus.

[Experiment 1]
A polymer chip of norbornene resin, which is a kind of cyclic olefin, is supplied to a single screw extruder, and the disk filter device of the present invention shown in FIG. 1 is inserted between the tip of the extruder and a coat hanger type T die. Installed so that the direction of the tip of the center post of the filter device on the outlet side is the slit direction of the T die (width direction of the resulting film), melt extrusion molding, and immediately cooled with a cooling roll to a thickness of 100 μm A plastic film having a width of 1600 mm was obtained.
The optical properties of the obtained plastic film were evaluated by the above method. As a result, no optical anomaly was observed except that one dark black streak continuous in parallel with the longitudinal direction was observed at positions of 760 mm on the left and right sides from the center in the width direction. Further, the gel was concentrated around the streaky optical anomaly of the obtained plastic film.
Therefore, both streak-like optical anomalies and gels appear outside the effective width of the product, and can be used without any trouble as optical materials for flat panel displays and the like.

[Experiment 2]
The thickness of the disk filter device of FIG. 1 was the same as in Experimental Example 1 except that the direction of the tip portion on the outlet side of the center post was set to be orthogonal to the slit direction of the T die (the width direction of the obtained film). A plastic film having a thickness of 100 μm and a width of 1600 mm was obtained.
The optical properties of the obtained plastic film were evaluated by the above method. As a result, a dark black streak-like portion continuous in parallel with the longitudinal direction was observed at the center in the width direction. Further, the gel was concentrated around the streaky optical anomaly of the obtained plastic film.
Therefore, in the present experimental example, there is a streak-like optical anomaly at the center in the width direction, so there was no portion that could only be used at half the width of the product.

[Experiment 3]
A disk filter device using a hollow center post having a hexagonal cross section shown in FIG. 7 (the molten polymer joins between the hub of the filter element and the center post and from the hollow portion). A plastic film having a thickness of 100 μm and a width of 1600 mm was obtained in the same manner as in Experimental Example 1 except that it was used.
The optical properties of the obtained plastic film were evaluated by the above method. As a result, a dark black streak-like portion continuous in parallel with the longitudinal direction was observed at the center in the width direction. Further, a large number of light white or black stripes continuous in parallel with the longitudinal direction were observed. Moreover, as a result of evaluating similarly about a gel, many gels were detected as a whole.
Therefore, this plastic film was not suitable for optical applications.

[Experiment 4]
A plastic film having a thickness of 100 μm and a width of 1600 mm was obtained in the same manner as in Experimental Example 1 except that an external flow type disk filter device using a center post having a square cross section was used.
The optical properties of the obtained plastic film were evaluated by the above method. As a result, one dark black streak-like portion continuous in parallel with the longitudinal direction at the central position in the width direction is further divided into two continuous lines parallel to the longitudinal direction at positions of 380 mm to the left and right of the center in the width direction A dark black streak was observed. Moreover, as a result of evaluating similarly about a gel, many gels were detected as a whole.
Therefore, this plastic film was completely optically non-uniform and unsuitable for optical applications.

The disc filter (internal / external flow type) whose cross section of the center post used in Experimental Example 3 used in the past is a hexagonal shape, and the disc filter device whose cross sectional shape of the center post used in Experimental Example 4 is quadrilateral ( When the outer flow type) is used, it can be seen that an optical abnormality due to the weld line is observed depending on the number and position of the merged portions of the molten polymer. Moreover, in such a structure, it turns out that a partial staying part arises and there is much generation | occurrence | production of a gel by the presence of the junction part of a center post and a hub, and the flow path opened in the center post.
On the other hand, when the disk filter device of the present invention is used, the weld line is a single straight line, the structure is simple and there are few staying parts, so there are no optical abnormalities. It is understood that it is suitable for the production of a plastic film for optical use. However, even when the disc filter device of the present invention is used, when it is installed as in Experimental Example 2, only one weld line appears, but it does not exhibit a sufficient effect because it appears in the center of the product. I understand.
In addition, when the disc filter device of the present invention is used, the gel is generated around the optical anomaly caused by the weld line, and the molten polymer tends to stay at the junction between the hub and the tip of the center post. This is probably because of this.

  The disc filter device of the present invention and the plastic film manufacturing method using the same can produce an optically uniform plastic film with substantially no weld line. A suitable disc filter device and optical film manufacturing method using plastic film extrusion with a T-die.

1 is a front sectional view showing a disk filter device according to an embodiment of the present invention. It is the front view seen from the width direction of the center post 6 shown in FIG. It is the front view seen from the thickness direction of the center post 6 shown in FIG. FIG. 2 is a top cross-sectional view seen from d1-d1 in FIG. 1. FIG. 2 is a top cross-sectional view as seen from d2-d2 in FIG. FIG. 3 is a top cross-sectional view seen from d3-d3 in FIG. 1. It is a figure showing the cross-sectional shape of the center post of the disc filter apparatus used in Experimental example 3.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Casing 2 Fastener 3 Filter element 4 Hub 5 Through-hole 6 Center post 7 Flange A Inlet B Outlet C Central liquid collection path

Claims (3)

A plurality of disc-shaped filter elements having a hub are fitted and inserted into a center post provided through a flange at the center of the outlet of the cylindrical casing having an inlet and outlet for molten polymer. The stacked filter elements are integrally clamped, and the molten polymer introduced into the casing from the inlet is filtered by the filter element and formed between the center post and the hub. In the disk filter device led to the central liquid collection path and led out of the casing from the outlet,
2. A disk filter device according to claim 1, wherein the central liquid collecting channel is divided into two by the center post, and a tip portion of the center post on the molten polymer outlet side is formed in a knife edge shape.   2. The disk filter device according to claim 1, wherein a cross-sectional area of the center post is gradually reduced toward the molten polymer outlet. When a polymer chip is melted and extruded by an extruder, filtered by a disk filter device, and then extruded from a T die to produce a plastic film, the disk filter device according to claim 1 or 2 is placed on the outlet side of the center post. The plastic film manufacturing method is characterized in that the plastic film is installed so that the tip portion is oriented in the slit direction of the T die.

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