JP2011173263A - Flat die for extrusion molding - Google Patents

Abstract

The present invention provides a flat die for extrusion molding capable of suppressing mouth opening without deteriorating the distribution of flow rate in the width direction.
A flat die for extrusion has a slit through which the molten resin passes when the molten resin is extruded into a sheet shape. The slit 11 has a first slit portion 11a located on the inlet side of the molten resin to the slit 11 and a cross section perpendicular to the direction of the molten resin passing through the first slit portion 11a located on the outlet side of the molten resin of the slit 11 And a second slit portion 11b having a smaller rectangular cross section. The first slit portion 11 a has gaps having different sizes in the longitudinal direction of the slit 11, and the gap increases as it goes from the central portion to the end portion in the longitudinal direction of the slit 11.
[Selection] Figure 9

Description

  The present invention relates to a flat die for extrusion forming that is formed into a sheet by extruding a fluid such as a molten resin.

  When a molten resin or the like is formed into a sheet by an extruder, a die called a flat die is provided at the discharge port of the extruder. By extruding a fluid such as a molten resin sent from a melt plasticizer with an extrusion molding machine provided with a flat die at a discharge port, the fluid such as a molten resin is formed into a sheet shape in accordance with the shape of the flat die. Formed. Further, the flat die may be used for laminating a plurality of different types of resins in the thickness direction of the sheet.

  FIG. 1 is a perspective view showing an appearance of a flat die 1 for extrusion molding. As shown in FIG. 1, the flat die 1 for extrusion molding is configured by connecting a first die body 2 and a second die body 3 with a body coupling bolt 4. A flow path 5 is formed inside. Furthermore, the extrusion flat die 1 includes a die inlet 6 for taking a fluid into the flow path 5 from the outside of the extrusion flat die 1, and a flat die for extrusion with the fluid formed in a thin and wide width. 1 and a die outlet 7 for discharging to the outside.

  In the description of this document, the longitudinal direction of the die outlet 7 is the width direction. Moreover, let the transversal direction of the die exit 7 be a thickness direction, and let the direction perpendicular | vertical to the width direction and the thickness direction be a flow direction.

  In the flat die 1 for extrusion molding, various shapes have been proposed as the flow channel 5 because the shape of the flow channel 5 affects the shape of the extruded product. For example, Non-Patent Document 1 discloses a flat die 1 for extrusion molding called a T-die.

  FIG. 2 is a schematic view of the flow path 5a in the T-die disclosed in Non-Patent Document 1. As shown in FIG. 2, the flow path 5a in the T-shaped die has a manifold 8 for ensuring fluid flow from the die inlet 6 to the die outlet 7 to the end in the width direction, and a desired thickness of the fluid. The slits 9 are formed in this order. Therefore, the fluid is extruded into a sheet shape by passing a fluid such as a molten resin through the slit 9.

  In the flow channel 5a of the T-shaped die shown in FIG. 2, the manifold 8 has a cylindrical shape, and the central axis of the manifold 8 is arranged in parallel with the width direction. For example, the flow F1 from the die inlet 6 to the die outlet 7 through the center in the width direction of the manifold 8 and the slit 9 is the shortest, and the die outlet 7 passes from the die inlet to the end of the manifold 8 and the slit 9 in the width direction. The flow F2 toward is the longest. In the flows F1 and F2, the length of the path in the slit 9 is the same, and the resistance received from the slit 9 is the same. However, the resistance generated in the path of the flow F2 is increased in the flow F2 by the length of the path in the manifold 8 compared to the flow F1. Therefore, the flow rate of the flow F2 is smaller than the flow rate of the flow F1, and the extruded product tends to be thick at the center in the width direction and thin at the ends.

  In order to solve the above problem, Non-Patent Document 1 discloses a coat hanger type die, and Patent Document 1 discloses an inclined land type die. FIG. 3 is a schematic view of the flow path 5b in the coat hanger type die disclosed in Non-Patent Document 1, and FIG. 4 is a schematic view of the flow path 5c in the inclined land type die disclosed in Patent Document 1. It is.

  As shown in FIG. 3, in the flow path 5b in the coat hanger type die, the distance between the center portion in the width direction of the manifold 8 and the die outlet 7 is larger than the distance between the end portion in the width direction of the manifold 8 and the die outlet. A manifold 8 is formed to be large.

  In the coat hanger type die shown in FIG. 3, the length of the path in the slit 9 of the flow F1 is larger than the path of the slit 9 in the flow F2, and the resistance that the slit 9 gives to the fluid is greater in the flow F1 than in the flow F2. growing. In particular, since the gap of the slit 9 is smaller than the diameter of the manifold 8, the resistance per unit length that the slit 9 gives to the fluid is larger than the resistance per unit length that the manifold 8 gives to the fluid. Therefore, even if there is a difference in the lengths of the paths of the flows F1 and F2, the resistance received by the fluid having the paths of the flows F1 and F2 can be made the same, and the flow rate distribution in the width direction of the die outlet 7 can be changed. It can be made uniform.

  As shown in FIG. 4, in the channel 5c in the inclined land type die, the central axis of the manifold 8 is arranged in parallel with the width direction like the T type die. The slit 9 includes a first slit portion 9a and a second slit portion 9b having a gap that is smaller than the gap between the first slit portions 9a. From the manifold 8 to the die outlet 7, a first slit portion 9a and a second slit portion 9b are provided in this order. In the inclined land die, the length of the first slit portion 9a in the flow direction is the shortest at the center in the width direction and the longest at the end. Conversely, the length of the second slit portion 9b in the flow direction is the longest at the center in the width direction and the shortest at the end.

  In the inclined land die shown in FIG. 4, the first slit portion 9a in the flow F1 is shorter than the first slit portion 9a in the flow F2, and conversely, the second slit portion 9b in the flow F1 is the second slit in the flow F2. It is longer than the part 9b. Since the gap between the second slits 9b is smaller than the gap between the first slits 9a, the resistance per unit length given to the fluid by the second slits 9b is the length per unit given to the fluid from the first slits 9b. Greater than the resistance. Therefore, even if there is a difference in the lengths of the paths of the flows F1 and F2, the resistance received by the fluid having the paths of the flows F1 and F2 can be made the same, and the flow rate distribution in the width direction of the die outlet 7 can be changed. It can be made uniform.

  Further, in recent years, in order to manufacture a sheet such as a plastic film that is very thin with respect to the width, higher uniformity in the thickness in the width direction is required. Therefore, in both the coat hanger type die and the inclined land type die, as shown in FIGS. 5 and 6, a lip land 10 having a smaller gap may be provided at the end of the flow path. FIG. 5 is a schematic view of the flow path 5b when the lip land 10 is provided on the coat hanger type die, and FIG. 6 is a flow path 5c when the lip land 10 is provided on the inclined land type die. FIG. By providing the lip land 10 at the tip of the flow path, it becomes possible to obtain an extrudate that is thinner and more uniform in the width direction.

JP-A-56-136328

Published by Ito Makoto, “Extrusion Die Design”, Industrial Research Committee

  However, when manufacturing using a fluid with a high viscosity, the pressure loss in the lip land 10 is increased, and a deformation called a mouth opening in which the gap between the lip lands 10 extends in the thickness direction is likely to occur. As the amount of opening is larger, an extruded product having a thickness different from the desired thickness is formed, and the thickness in the width direction of the sheet becomes non-uniform, resulting in a quality problem.

  The opening of the mouth occurs with the main body connecting bolt 4 as a fulcrum and the lip land 10 as the main action point. Therefore, the main body coupling bolt 4 is disposed on the die inlet 6 side from the manifold 8 along the edge of the manifold 8 so that the distance to the lip land 10 is reduced.

  In the coat hanger type die, as shown in FIG. 7, the distance between the main body coupling bolt 4 and the lip land 10 at the center in the width direction is larger than the distance between the main body coupling bolt 4 and the lip land 10 at the end in the width direction. Also grows. Therefore, the opening amount at the center in the width direction tends to be large, and the thickness in the width direction of the extruded product tends to be non-uniform.

  On the other hand, in the inclined land type die, as shown in FIG. 8, the main body coupling bolt 4 is arranged in parallel with the lip land 10, so that the opening at the center in the width direction is suppressed. However, in the inclined land type die, since it is necessary to form the first slit portion 9a and the second slit portion 9c, the length of the slit 9 in the flow direction tends to increase. Therefore, the distance from the main body coupling bolt 4 to the lip land 10 is increased, and the opening amount in the entire width direction is likely to be increased. When the length in the flow direction of the first slit portion 9a and the second slit portion 9b is shortened in order to shorten the length in the flow direction of the slit 9, for example, the resistance received by the flows F1 and F2 shown in FIG. The flow distribution in the width direction gets worse.

  Then, an object of this invention is to provide the flat die for extrusion molding which can suppress opening of a mouth, without deteriorating the distribution of the flow rate of the width direction.

  In order to achieve the above object, the flat die for extrusion molding of the present invention has a slit through which the molten resin passes when the molten resin is extruded into a sheet. The slit is a rectangular section smaller than a first slit portion positioned on the inlet side of the molten resin into the slit and a section perpendicular to the direction of the molten resin passing through the first slit portion on the outlet side of the molten resin. A second slit portion having The first slit portion has a gap having a different size in the longitudinal direction of the slit, and the gap increases from the central portion to the end portion in the longitudinal direction of the slit.

  ADVANTAGE OF THE INVENTION According to this invention, the flat die for extrusion molding which can suppress opening of a mouth is provided, without worsening distribution of the flow rate of the width direction.

It is a perspective view of the flat die for extrusion molding. It is the schematic of the flow path of the T type die which is one of the conventional flat dies for extrusion molding. It is the schematic of the flow path of the coat hanger type die which is one of the conventional flat dies for extrusion molding. It is the schematic of the flow path of the inclination land type | mold die which is one of the conventional flat dies for extrusion molding. It is the schematic of the flow path at the time of providing a lip land in a coat hanger type | mold die. It is the schematic of the flow path at the time of providing a lip land in an inclination land type | mold die. It is a figure explaining arrangement | positioning of the main body coupling bolt in a coat hanger type | mold die. It is a figure explaining arrangement | positioning of the main body coupling bolt in an inclination land type | mold die. It is the schematic of the flow path of the flat die for extrusion molding in this invention. It is sectional drawing of the AA surface of the 1st slit part shown in FIG. It is BB sectional drawing of the flow path shown in FIG. It is a figure explaining arrangement | positioning of the main body coupling | bonding bolt in the flat die for extrusion molding in this invention. It is a perspective view of the 1st die main part of the flat die for extrusion molding machines in the example of the present invention. It is a perspective view of the 2nd die body which constitutes the flat die for extrusion molding by making a pair with the 1st die body. It is the figure which plotted the flow volume distribution of the width direction of the die exit 7 at the time of extrusion molding. It is the figure which plotted opening amount distribution of the width direction of the die exit 7 at the time of extrusion molding. 10 is a perspective view of a first die body used in Comparative Example 2. FIG.

  Hereinafter, an embodiment of the present invention will be described in detail with reference to the drawings. FIG. 9 is a schematic view of the flow path 5d of the flat die for extrusion molding according to the embodiment of the present invention. As shown in FIG. 9, the flow path 5d includes a die inlet 6 for introducing a fluid such as a molten resin into the flow path 5d, and a die outlet 7 substantially equal to the width and thickness of the extruded product.

  Further, the flow path 5d includes a manifold 8 for ensuring fluid flow from the die inlet 6 to the die outlet 7 to the end in the width direction, and a slit 11 that passes through the fluid and is formed into a sheet shape. In this order. The fluid outlet of the slit 11 coincides with the die outlet 7. By extruding the fluid from the manifold 8 to the slit 11, the fluid is formed in a sheet shape.

  The manifold 8 has a cylindrical shape, and is arranged so that the central axis of the manifold 8 is parallel to the width direction. In addition, the die inlet and the manifold 8 are communicated with each other at the center of the manifold 8 in the width direction. The manifold 8 is not limited to a cylindrical shape, and may be any shape that has a width that can spread the fluid in the width direction of the slit 11.

  The slit 11 includes a first slit portion 11 a located on the inlet side of a fluid such as molten resin into the slit 11, that is, the manifold 8 side, and a second slit portion located on the outlet side of the fluid such as molten resin in the slit 11. And including. The 2nd slit part 11b has a rectangular cross section smaller than the cross section perpendicular | vertical to the direction through which fluids, such as molten resin, of the 1st slit part 11a pass. That is, the 2nd slit part 11b has a clearance gap and a width | variety substantially equal to the thickness and width | variety of an extrusion, and bears the function of a lip land.

  FIG. 10 is a cross-sectional view of the first slit portion 11a shown in FIG. 9 taken along the AA plane perpendicular to the flow direction. As shown in FIG. 10, the first slit portion 11 a has gaps having different sizes in the width direction, that is, the longitudinal direction of the slit 11. In particular, the gap at the center in the longitudinal direction of the slit 11 is the smallest, and the gap becomes larger toward the end.

  FIG. 11 is a cross-sectional view of the flow path 5d shown in FIG. 9 taken along a BB plane perpendicular to the width direction at a certain position in the width direction. As shown in FIG. 11, the gap between the first slit portions 11a is larger than the gap between the second slit portions 11b. In addition, the gap of the 1st slit part 11a in the part with the smallest gap of the 1st slit part 11a, ie, the center part of the width direction, may be the same as the gap of the 2nd slit part 11b.

  Next, the flow path and the resistance that the fluid receives from the path in the present embodiment will be described. As shown in FIG. 9, the flow F1 from the die inlet 6 to the die outlet 7 through the center in the width direction of the manifold 8 and the slit 9 and the width from the die inlet 6 to the end of the manifold and the slit 9 in the width direction are performed. The flow F2 toward the die outlet 7 will be described.

  As shown in FIG. 9, since the flow F2 spreads from the center in the width direction to the end in the manifold 8, the flow F2 has a longer path in the manifold 8 than the flow F1. Therefore, the resistance that the fluid receives from the manifold 8 is greater in the flow F2 than in the flow F1.

  In the present embodiment, the gap between the first slit portions 11b in the flow F2 is larger than the gap between the first slit portions 11b in the flow F1. Therefore, the resistance that the fluid receives from the first slit portion 11b is smaller in the flow F2 than in the flow F1.

  Therefore, the resistance which the flow F1 and the flow F2 receive from the manifold 8 and the slit 11 can be made the same by making the clearance gap between the 1st slit parts 11a into an appropriate value in the width direction. Therefore, the flow distribution in the width direction of the die outlet 7 can be made uniform.

  Then, arrangement | positioning of the main body coupling | bonding bolt 4 in the flat die for extrusion molding in this invention is demonstrated. FIG. 12 is a view for explaining the arrangement of the main body coupling bolts in the flat die for extrusion molding according to the present embodiment.

  As shown in FIG. 12, a plurality of main body coupling bolts 4 are arranged on the die inlet 6 side with respect to the manifold 8 along the edge of the manifold 8. The main body coupling bolts 4 are arranged in parallel with the longitudinal direction of the slits 11, and the distance between each main body coupling bolt 4 and the second slit portion 11b can be made the same. Therefore, it is possible to suppress an increase in the amount of opening at the center in the width direction, which is likely to occur with a conventional coat hanger type die.

  In addition, in the flow path 5b using the flat die for extrusion molding according to the present invention, the resistance per unit length in the first slit portion 11a can be adjusted by the gap in the width direction. The length of the flow direction of 11a can be shortened. Specifically, in FIG. 9, in the flow F1 and the flow F2, when the length in the flow direction of the first slit portion 11a is reduced, the gap between the first slit portions 11a in the flow F1 and the first slit portion in the flow F2. What is necessary is just to enlarge the difference with the clearance gap of 11a.

  By shortening the length of the first slit portion 11a in the flow direction, the distance between the main body coupling bolt 4 and the second slit portion 11b can be reduced. Therefore, the amount of opening can be suppressed without deteriorating the flow rate distribution in the width direction at the die outlet 7.

  EXAMPLES Hereinafter, although an Example demonstrates this invention further in detail, this invention is not limited at all by these. In the following description, the same portions as those shown in the above-described embodiment will be described using the same reference numerals.

(Example)
FIG. 13 is a perspective view of the first die body 12 in the embodiment of the present invention, and FIG. 14 is a second die body that forms a flat die for extrusion molding in pairs with the first die body 12. 13 is a perspective view of FIG.

  As shown in FIG. 14, the second die body 13 is provided with a manifold forming wall 14b and a slit forming wall 15b for forming the manifold 8 and the slit 11 shown in FIG. The slit forming wall 15b is formed with a flat surface.

  As shown in FIG. 13, the first die body 12 is also provided with a manifold forming wall 14a and a slit forming wall 15a. The slit forming wall 15a includes a first slit portion forming wall 16a and a second slit portion forming wall 16b for forming the first slit portion 11a and the second slit portion 11b shown in FIG.

  In the present embodiment, the central portion in the width direction of the first slit portion 11a shown in FIG. 9, that is, the smallest gap of the first slit portion 11a is 4.0 mm, and the end portion in the width direction, that is, the first slit portion 11a. The largest gap was set to 8.4 mm. The surface of the first slit portion 11a connecting the central portion and the end portion in the longitudinal direction of the slit 11 was formed as a continuous flat surface having no step. Moreover, the length of the flow direction of the 1st slit part 11a was 50 mm, and the width | variety of the die exit 7 was 1000 mm.

  Extrusion molding of polyethylene having a melt index (MI) of 5.0 at a flow rate of 300 kg / h is performed on a flat die for extrusion formed by joining the first and second die bodies 12 and 13 together. went.

  FIG. 15 plots the horizontal axis as the distance from the center in the width direction at the die outlet 7 and the vertical axis as the flow rate of polyethylene at the die outlet 7. In addition, the flow rate of polyethylene represents the flow rate at each position in the width direction of the die outlet 7 as a ratio of the average flow rate of the entire die outlet 7 in the width direction. The plot by the solid line of the graph shown in FIG. 15 is the flow rate distribution in the width direction in the present embodiment. As shown in FIG. 15, the flow rate in each width direction in this example was within 3% of the average flow rate, and showed very good extrusion characteristics.

  FIG. 16 is a diagram in which the opening amount distribution in the width direction of the die outlet 7 at the time of extrusion molding is plotted. The plot by the solid line of the graph shown in FIG. 16 is the opening amount distribution in the width direction in the present embodiment. As shown in FIG. 16, the opening amount of the die outlet 7 was suppressed to about 180 μm.

  Next, the flat die for extrusion molding shown in the following comparative examples was used for comparison with the examples of the present invention.

(Comparative Example 1)
In Comparative Example 1, an extrusion flat die having substantially the same dimensions as the shape of the flat die for extrusion shown in the examples of the present invention and different dimensions was used. Specifically, the gap at the central portion in the width direction of the first slit portion 11a shown in FIG. 9 is set to 4.0 mm, and the gap at the end portion in the width direction of the first slit portion 11a is set to 5.3 mm. Moreover, the length of the flow direction of the 1st slit part 11a was 80 mm.

  Other dimensions, such as the width of the die outlet 7 and other dimensions, were the same as in the example. Therefore, the distance between the main body coupling bolt 4 and the die outlet 7 is 30 mm larger than the embodiment.

(Comparative Example 2)
In Comparative Example 2, extrusion molding was performed using a conventional inclined land die. Specifically, the first die main body 17 shown in FIG. 17 and the second die main body 13 shown in FIG. 14 are combined to form a flat die for extrusion molding. FIG. 17 is a perspective view of the first die body 17 used in Comparative Example 2. FIG. The first die body 17 used in Comparative Example 2 includes a first slit portion forming wall 18a and a second slit portion for forming the first slit portion 9a, the second slit portion 9b, and the lip land 10 shown in FIG. A forming wall 18b and a lip land forming wall 19 are provided.

  In Comparative Example 2, the gap between the first slit portions 9a and the gap between the second slit portions 9b shown in FIG. 6 were set to 5.2 mm and 4.0 mm, respectively. Moreover, the distance (T shown in FIG. 6) in the flow direction between the central portion and the end portion in the width direction of the first slit portion 9a was set to 80 mm.

  Other dimensions, for example, the width of the die outlet 7 and the dimension of the second slit portion 11b were the same as in the example. Therefore, the distance between the main body coupling bolt 4 and the die outlet 7 in Comparative Example 2 is the same as that in Comparative Example 1, and is 30 mm larger than that in Example 1.

  Using the flat dies for extrusion molding of Comparative Example 1 and Comparative Example 2, the same extrusion molding as in Example 1 was performed, and the flow rate distribution at the die outlet 7 and the opening amount of the die outlet 7 were measured. And plotted in FIG. 15 and FIG. 16, the plots indicated by broken lines show the results in Comparative Example 1, and the plots shown by alternate long and short dash lines show the results in Comparative Example 2.

  As shown in FIG. 15, it can be confirmed that the flow distribution is substantially equal in Example 1, Comparative Example 1, and Comparative Example 2. That is, even in the shape of the flow path of the flat die for extrusion molding of the present invention, the flow rate distribution in the width direction at the die outlet 7 can be maintained, which is equivalent to the shape of the flow path of the conventional inclined land die. .

  Moreover, as shown in FIG. 16, in Comparative Example 1 and Comparative Example 2, the maximum opening amount was 270 μm. In Example 1, the maximum opening amount was about 180 μm, and by using the flat die for extrusion of the example, the opening amount could be suppressed by about 35%.

  This is because, in comparison with Comparative Example 1 and Comparative Example 2, in the example, the body coupling bolt position was moved 30 mm closer to the die outlet 7 side, so that the resistance to bending received from the fluid increased.

  As described above, by using the form of the flat die for extrusion molding according to the present invention, the opening amount can be further suppressed without impairing the flow rate distribution in the width direction of the die outlet 7.

  Further, in this embodiment, the continuous surface from the center portion to the end portion in the longitudinal direction of the first slit portion 11a is linearly changed, but the surface is non-linear, for example, a secondary parabola. This makes it possible to make the flow rate distribution in the width direction at the die outlet 7 uniform with higher accuracy.

DESCRIPTION OF SYMBOLS 1 Extrusion flat die 2, 12, 17 1st die body 3, 13 2nd die body 4 Body coupling bolt 5 Flow path 6 Die inlet 7 Die outlet 8 Manifold 9 Slit 9a 1st slit part 9b 2nd slit Part 10 Ripland 11 Slit 11a First slit part 11b Second slit part

Claims (5)

In a flat die for extrusion having a slit through which the molten resin passes when the molten resin is extruded into a sheet shape,
The slit is
A first slit portion located on the inlet side of the molten resin to the slit;
A second slit portion that is located on the outlet side of the molten resin of the slit and has a rectangular cross section that is smaller than a cross section perpendicular to the direction in which the molten resin passes of the first slit portion,
The first slit portion has gaps having different sizes in the longitudinal direction of the slit, and the gap increases from a central portion to an end portion in the longitudinal direction of the slit. Flat die for extrusion molding.   2. The flat die for extrusion molding according to claim 1, wherein the first slit portion is formed by a surface continuous from a center portion in the longitudinal direction of the slit to an end portion.   The flat die for extrusion molding according to claim 2, wherein the continuous surface changes linearly.   The flat die for extrusion molding according to claim 2, wherein the continuous surface changes non-linearly.   A first die main body and a second die main body that form at least the slits in pairs, wherein the first die main body and the second die main body are coupled by a body coupling bolt; The flat die for extrusion molding according to any one of claims 1 to 4, wherein the main body coupling bolt is disposed in parallel with the longitudinal direction of the slit.

Images