JPH05253997A - Die for extruding machine - Google Patents

Abstract

PURPOSE:To control remarkably generation of the discharge from the eye at the time of extrusion molding, and curing is made remarkable by high-viscous grade of polycarbonate having especially high shearing rate, by forming a tapered part having a half vertical angle of 4-20 deg. on an outlet part of a die. CONSTITUTION:A tapered part 1 having a half vertical angle of 4-20 deg. is formed on an outlet part of a flow path of a die. Since the tapered part 1 is provided on the outlet of a die hole like this, expansion of resin by a Barus effect is completed on this side than an edge part and the resin neither stick nor stay on an edge 4, the title die is free from dwell, oxidation and heat deterioration of a polymer and generation of the discharge from the eye is controlled remarkably. Then it is not preferable since when the half vertical angle theta of the tapered part 1 is less than 4 deg., a control effect in generation of the discharge from the eye is insufficient and when the same exceeds 20 deg., resin is accumulated and becomes apt to burn at the time of cleaning of the edge 4.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an extruder die used for molding a resin. More specifically, the present invention relates to an extruder die capable of remarkably suppressing the occurrence of eye crevices during molding of a thermoplastic resin such as polycarbonate.

[0002]

2. Description of the Related Art Extrusion molding is the most general molding method, and the shape of a molding die has been widely studied. For example, the cross-sectional shape of the flow path of the die has various shapes according to the purpose, and the flow characteristics such as pressure drop and shear rate have been investigated for various shapes, and the flow at the die inlet has been investigated to prevent the occurrence of melt fracture. It is also known to devise ways such as tapering the road (SPE Journal, 4
23 (1960)). However, regarding the edge shape of the flow path outlet of the die, it has been known only to round the right angle and round the angle at most.

[0003]

By the way, when a thermoplastic resin such as polycarbonate is extruded and pelletized, a deteriorated material commonly referred to as an eye crocodile is generated and adhered at the flow path outlet of the die, and this deteriorates the product. There is a problem that it is mixed and becomes a defective product. Frequent cleaning is required to prevent deterioration products from being carried along with the product, which has been a factor in lowering production capacity and increasing production loss.

[0004]

Means for Solving the Problems As a result of diligent studies on the suppression of the occurrence of eye dents at the exit of the die flow path, the present inventors have accumulated at the exit edge of the flow path of the die (hereinafter referred to as "die hole"). The present invention has been accomplished by finding that the resin is oxidatively deteriorated and thermally deteriorated to cause eye blemishes. Therefore, the present invention has been found to be able to remarkably suppress the eye rosiness generation by providing a taper at the die hole outlet portion.

That is, the gist of the present invention resides in an extruder die characterized in that a taper having a half-vertical angle of 4 to 20 ° is formed at the outlet of the flow path of the die. Hereinafter, the present invention will be described in detail with reference to the drawings. FIG. 1 is a diagram schematically showing a vertical cross section of a die hole outlet portion of the present invention. The die of the present invention is characterized in that a taper portion (1) is formed at the exit portion of the die hole.

The angle of the taper portion (1) has a half-vertical angle θ of 4 to
It is 20 °. If it is less than 4 °, the effect of suppressing the occurrence of eye blemishes is insufficient. If it exceeds 20 °, the resin is likely to be burnt because the resin is accumulated during cleaning of the edge (4), which is not preferable. Further, the size (depth) (5) of the tapered portion is usually set such that the die hole edge diameter (2) is 1.05 to 1.3 times the die hole inner diameter (3). If it is less than the lower limit, the effect of suppressing the occurrence of eye blemishes is insufficient. Exceeding the upper limit and exceeding the maximum strand diameter at the time of the ballast effect will cause a gap between the die and the resin, and the resin is likely to be burnt because of the accumulation during edge cleaning, which is not preferable.

The present invention can be applied to straight slits for forming films and sheets and circular slits for forming pipes, but is particularly suitable for a nozzle having a circular cross section for forming pellets. The case of a pellet nozzle will be described below. In the case of pellet molding, a plate having a single or plural circular holes having a diameter of 1 mm to 10 mm (hereinafter referred to as a die plate) is usually used as a die. The diameter and the number of die holes can be determined according to the size of pellets and the shear rate in the die holes. The shear rate can be determined by a known method from the viscosity, extrusion rate, die hole cross-sectional area and the like.

The shape of the inlet of the die hole may be a known shape and may or may not have a taper. The shape of the die hole inlet is determined in consideration of the prevention of melt fracture. The material of the die plate is usually stainless steel rope (SUS304 etc.) or tool rope (Cr 11-13).
%, An iron alloy containing 0.8 to 1.2% Mo) and the like.

Further, the surface finish accuracy of the flow path surface of the die hole does not pose any particular problem, but it is needless to say that the edge is not damaged. If the edge is scratched, eye blemishes are likely to occur. The resin molded by the die of the present invention is not limited as long as it is a thermoplastic resin, but it is effective when it is a polyester resin such as polycarbonate, nylon, PET, PBT or a compound resin obtained by adding a filler, glass fiber or the like to these. It is large and is particularly useful for polycarbonate, and even in the case of polycarbonate, it is particularly effective when extruding at a shear rate of 280 sec ^-1 or more.

When polycarbonate pellets are molded using the extruder of the present invention, the polymer extruded from the die can be pelletized by cooling it in a conventional manner and then cutting it with a cutter.

[0011]

Next, the mechanism by which the die of the present invention exhibits the effect of preventing eye blemishes during extrusion molding will be described. It has been conventionally known that the eye die is an oxide of resin or the like. As a result of diligent studies, the present inventors have found that the molten resin adheres to and stays at the edge of the die hole and is oxidized by the outside air.

For this reason, for example, if the edge has scratches, the resin is more likely to stay, and the occurrence of eye blemishes remarkably increases. Further, even if the edge is not scratched, the resin expands due to the loosening effect during molding and comes into contact with the edge, so that the resin stays at the edge. In the present invention, by providing a taper at the die hole outlet, the expansion of the resin due to the ballast effect ends before the edge, and the resin does not adhere to or stay at the edge, so that there is no polymer retention, oxidation, or thermal deterioration, and there is no eye stain. Can be remarkably suppressed.

[0013]

EXAMPLES The present invention will be specifically described below with reference to examples, but the present invention is not limited to the examples as long as the gist thereof is not exceeded. Example 1 A polycarbonate resin (made by Mitsubishi Kasei Co., Ltd.,
Experiments were carried out using the trade name NOVAREX 7030A).
A die having a die hole as shown in FIG. 1 was used. The inner diameter of the die hole was 2.2 mmφ ((3) in FIG. 1) and the length was 11 mm. At the tip of the die hole,
A taper having an angle (θ) of 10 ° and a depth (5) of 1 mm was formed. Using a die as described above, the polycarbonate resin is heated at a temperature of 320 ° C. and a shear rate of 340 sec ⁻¹ for 180 times.
Extrusion molding was carried out for one minute and the presence or absence of eye blemishes was checked at intervals of 15 minutes, but no eye blemishes were found.

Comparative Example 1 The same procedure as in Example 1 was carried out except that the exit of the die hole was not tapered and the edge was right angled. Eye fogging occurred 15 minutes after the start of molding.

Comparative Example 2 The same as Comparative Example 1 except that a radius of 1 mm was formed on the edge. Eye blemishes occurred 30 minutes after the start.

Comparative Example 3 The same as Example 1 except that the taper was set at an angle (θ) of 3 ° and a depth (5) of 1 mm. Eye blemishes occurred 30 minutes after the start.

Comparative Example 4 The same as Example 1 except that the taper was 30 ° in angle (θ) and 1 mm in depth (5). There was no eye blemishes, but the resin remained on the taper during cleaning, and it burned during the next molding.

Example 2 A die hole having an inner diameter (3) of 5.5 mmφ and a length of 20 mm
, Taper angle (θ) 5.8 °, depth (5) 5.0 mm
The extrusion molding was performed in the same manner as in Example 1 except that There was no generation of tars for 180 minutes. In addition, the same device allowed continuous operation for 72 hours without the eye escort being entrained in the product.
The results are summarized in Table-1.

[0019]

[Table 1] (Note 1) Instead of the taper, the edge is a curved surface of 1 mmR. (Note 2) The resin remained on the taper and burned during cleaning.

[0020]

The die of the present invention has the effect of remarkably suppressing the occurrence of eye crevices during extrusion molding. In particular, the effect becomes remarkable in a high viscosity grade of polycarbonate having a high shear rate.

[Brief description of drawings]

FIG. 1 is a schematic view of a vertical cross section of an outlet of a die of the present invention.

[Explanation of symbols]

 1 Taper 2 Edge diameter 3 Hole inner diameter 4 Edge 5 Taper depth θ Taper half-vertical angle

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Kenichi Haga, No. 1 Shiroishi Kurosaki, Yawatanishi-ku, Kitakyushu City Mitsubishi Kasei Co., Ltd. Kurosaki Plant

Claims (2)

[Claims] 1. A semi-vertical angle of 4 to 20 ° at the outlet of the flow path of the die.
A die for an extruder, which is characterized by forming a taper. 2. Polycarbonate at a shear rate of 280 s
A die used for extrusion molding at ec ^-1 or more.
The die for an extruder described in.