JPH04275126A - Extrusion mold - Google Patents

Abstract

PURPOSE:To mold a sheet having uniform thickness and surface roughness by a single mold. CONSTITUTION:A first manifold part 4 distributing the molten resin flowing in a mold main body 1 in a lateral direction, a land part 5 capable of adjusting the flow rate of the resin in the extrusion direction in the lateral direction through a choke bar 2, a second manifold 6 uniformizing the pressure of the resin in the lateral direction and a lip part 7 controlling the shearing force through a cap 3 are successively formed.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an extrusion mold.

0002

BACKGROUND OF THE INVENTION Extrusion molding is generally known as a method for manufacturing long objects such as endless sheets. In principle, extrusion molding is a method in which plastic is melted in a heated cylinder (barrel), extruded with a screw, given a shape with a die (mold) at the tip, and then cooled and solidified with water or air. For example, to manufacture a sheet, a uniformly plasticized resin is extruded by an extruder S through a slit in a mold D, cooled on a roll R, trimmed at both ends, and cut into a predetermined size. (See Figure 5).

[0003] The long product formed in this manner is required to have a uniform wall thickness and a uniform surface roughness or appearance. In order to satisfy such requirements, there are known methods for adjusting the wall thickness, such as a method in which a choke bar is disposed inside the mold flow path, and a lip method in which vertical differential adjustment or bending adjustment is performed at the lip portion. On the other hand, to adjust the appearance and surface roughness, a roll having a surface shape suitable for the shape to be formed, such as a mirror finish roll, a matte roll, or a roll with a certain roughness, is used.

0004

[Problem to be Solved by the Invention] In this way, in order to give a uniform thickness and shape to a sheet, etc., a mold and a post-processing roll are required, and these must be adjusted or maintained and inspected separately. This made the work complicated.

[0005] The present invention was made in view of these problems, and is an extrusion molding method that makes it possible to mold sheets having the required uniform thickness and surface roughness using only a single mold. The purpose is to provide molds for use.

[0006]

[Means for Solving the Problems] The present invention provides a first manifold portion that distributes the resin that has flowed into the interior of the mold body in a direction perpendicular to the extrusion direction, and a first manifold portion that chokes the flow rate in the width direction in the extrusion direction. A land part that uniformly adjusts the resin pressure in the width direction through a bar, a second manifold part that equalizes the resin pressure in the width direction, and a lip part that uniformly adjusts the shear force in the width direction in the extrusion direction through the die. It is characterized by the presence of

[0007]

[Operation] The molten resin supplied from the molding machine to the mold body is
After being distributed in the width direction perpendicular to the inflow direction at the first manifold section, the flow rate in the width direction is adjusted almost uniformly by a choke bar at the land section. Next, the resin pressure of the molten resin is made uniform in the second manifold part, and further, when the molten resin reaches the lip part, it is adjusted to a desired thickness and uniform shearing force by the mouthpiece.

[0008] As a result, it is possible to mold sheets with a uniform thickness by adjusting the flow rate in the width direction and a uniform surface roughness by adjusting the shear force in the width direction using a single mold. .

[0009]

Embodiments Hereinafter, embodiments of the present invention will be described with reference to the drawings.

In FIG. 1, a mold D includes a mold body 1,
It consists of a choke bar 2 and a flexible lip 3 arranged on this mold body. A first manifold part 4, a land part 5, a second manifold part 6, and a lip part 7 extending in the width direction are formed in this mold body 1 in this order. A slit-shaped opening is formed at the tip. A choke bar 2 is disposed so as to be movable up and down by a bolt (not shown) facing the aforementioned land portion 5, and a base 3 is disposed so as to be movable up and down by a bolt (not shown) facing the lip portion 7. Note that 8 is an introduction passage formed to communicate between the first manifold section 4 and the molding machine S described above.

Therefore, the molten resin flowing into the mold body 1 from the molding machine S through the introduction passage 8 is directed by the first manifold part 4 in a direction perpendicular to the introduction passage 8, that is, in the width direction of the mold body 1. distributed to. Then, when the molten resin distributed in the width direction is pushed out to the land portion 5,
By adjusting the choke bar gap formed between the choke bar 2 and the land portion 5 by raising and lowering the choke bar 2, the flow rate in the width direction, that is, the thickness is adjusted.

Next, when the molten resin whose flow rate has been adjusted reaches the second manifold part 6, the pressure in the width direction is equalized, so that the molten resin pushed out to the lip part 7 is
The flow rate and pressure are adjusted to be constant in the width direction. Further, when it is desired to reduce the wall thickness at both ends, such as when a stretching process is added, the distribution of shearing force hardly changes even if the interval is adjusted in the width direction. After this, the lip part 7
When the molten resin is extruded, the shearing force in the width direction can be adjusted by adjusting the lip gap formed between the mouthpiece 3 and the lip part 7 by moving up and down the base 3.

[0013] Using the mold D of this example configured as described above, a predetermined thickness and surface roughness (emboss roughness) were obtained using PVB (polyvinyl butyral) as a resin at a resin temperature of 200°C and an extrusion rate of 550 kg/H. Extrusion molding was carried out to obtain a sheet.

These results are shown in solid line graphs in FIGS. 3 and 4. In FIG. 3, the thickness of the formed sheet is larger at the center than at the edges, and the flow rate at the center is is getting bigger. Also, in FIG.
The surface roughness (emboss roughness) at the center is greater than at the edges. As explained in Figure 3, this means that
The large flow rate at the center causes the flow velocity to be greater than at the ends, indicating that the shearing force received from the lip portion 7 is greater than at the ends.

Based on these results, by adjusting the choke bar gap through the choke bar 2 while keeping the lip gap fixed, sheets shown in the broken line graphs in FIGS. 3 and 4 were formed. That is, in FIG. 3, the thickness of the sheet was substantially uniform in the width direction and fell within the error range. In addition, in Figure 4, as the flow rate increases at the ends, the flow velocity at the ends increases relative to that at the center, and the shear force at the ends increases by this increase, and the shear force at the center increases. As a result, the shearing force could be controlled uniformly in the width direction, and the surface roughness could be molded to be approximately constant.

These facts indicate that by adjusting the choke bar gap using the choke bar 2, it is possible to mold a molded product with a uniform thickness in the width direction, and that the flow velocity in the lip gap changes based on the flow rate. ing. That is, in the case of flow rate adjustment using the conventional lip method, the flow rate change and the flow velocity change occur simultaneously because the gap at the outlet is changed, and thickness adjustment and shear force cannot be adjusted separately. For example, by adjusting the lip gap with the mouthpiece 3 together with the choke bar gap,
It becomes possible to change the flow rate of the molten resin passing through the lip gap independently of the thickness adjustment, and as a result, it becomes possible to mold the desired surface roughness by changing the shear force acting on the molten resin. .

[0017]

As described above, according to the present invention, there is a first manifold part that distributes the inflowing resin inside the mold body, and a land part that uniformly adjusts the flow rate in the width direction of the first manifold part through the choke bar. By forming a second manifold part that equalizes the resin pressure and a lip part that uniformly adjusts the shear force in the width direction through the die, it is possible to achieve a uniform thickness and a predetermined surface roughness with a single mold. It is now possible to form sheets, etc. that have been formed, and it is possible to reduce the processes that have been used in the past, such as forming rolls and thickness adjustment rolls, and eliminate breakdowns and maintenance inspections caused by the roll process. Can be done.

[Brief explanation of the drawing]

FIG. 1 is a partially cutaway overall plan view of a mold body.

FIG. 2 is a sectional view taken along the line AA in FIG. 1;

FIG. 3 is a graph showing changes in thickness in the width direction before and after adjusting the choke bar gap.

FIG. 4 is a graph showing changes in embossing roughness in the width direction before and after adjusting the choke bar gap.

FIG. 5 is a schematic diagram showing the overall configuration of extrusion molding.

[Explanation of symbols]

1　Mold body 2. Chalk bar 3. Flexible lip 4 First manifold part 5 Land part 6 Second manifold part 7 Lip part

Claims (1)

[Claims] [Claim 1] A first manifold portion that distributes the resin flowing into the mold body in a direction perpendicular to the extrusion direction, and a choke bar that uniformly adjusts the flow rate in the width direction in the extrusion direction. Extrusion molding characterized by comprising a land part, a second manifold part that equalizes the resin pressure in the width direction, and a lip part that uniformly adjusts the shear force in the width direction in the extrusion direction through the die. Mold for use.