JPS62238709A - Method and apparatus for manufacturing conductive molding material - Google Patents

Abstract

PURPOSE:To accelerate soak of molten resin into a metallic fiber bundle, by displacing the metallic fiber bundle in the direction meeting at a right angle with an axial direction to molten resin with which the metallic fiber bundle is covered at the inside of a die or an outlet part of the same. CONSTITUTION:Thermoplastic resin is charged into an extruding machine 1 through a hopper 2 of the same, melted and extruded by a screw 3 and supplied to a resin covering equipment 4. A metallic fiber bundle 5 is supplied to the resin covering equipment 4 after the same has been preheated by a heating equipment 6. The resin covering equipment 4 is constituted of a mandrel 7, a molten thermoplastic resin tank 8 and a die 9. The metallic fiber bundle 5 is impregnated and covered with the thermoplastic resin, a resin-covered material 10 of the metallic fiber bundle is extruded in a stranded state through the die 9, which is cut off by a pelletizer 11 after cooling and made into pellets. With this construction, a molding material which is small in quantity of the resin, sticks the resin to the metallic fiber bundle through impregnation and is superior in electromagnetic shielding properties, dispersion properties and external appearance properties can be obtained.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Applications] The present invention relates to a method and apparatus for producing a conductive molding material containing metal fibers.

[Conventional technology]

As a method of manufacturing a conductive molding material used as an electromagnetic wave shielding material (hereinafter referred to as shielding material) by blending metal fibers with thermoplastic resin, a continuous metal fiber bundle is coated with molten resin, and after cooling, A method of cutting into pellets is known (Japanese Unexamined Patent Publication No. 51-59944).

However, when making a molded article from the pellets obtained by this method or from the pellets and a thermoplastic resin, it is difficult to uniformly disperse the metal fibers in the resin.
The shielding effect and appearance were unsatisfactory.

[Problem that the invention seeks to solve]

An object of the present invention is to provide a method and apparatus for producing a conductive molding material that has improved dispersion of metal fibers into a thermoplastic resin when molded.

[Means for solving problems]

In the present invention, four continuous metal fiber bundles are attached to a thermoplastic resin in a molten state.
In a method for manufacturing a conductive molding material in which metal fibers are coated with resin, the metal fiber bundle is displaced at least once in a direction perpendicular to the axial direction with respect to the molten resin to be coated within a die or at the exit of the die. This is a method of manufacturing an electrically conductive molding material.

Moreover, the second invention is a die in which at least one bent portion is provided in the die flow path.

The thermoplastic resin used in the present invention is not particularly limited, and various resins such as styrene resins such as polystyrene, As resin, and ABS resin, olefin resins such as polypropylene, polycarbonate, polyamide, and polyester can be used.

The metal fiber is not particularly limited as long as it has conductivity; for example, stainless steel fiber, copper fiber, etc. can be used. The metal fiber preferably has a circular or elliptical cross-sectional shape and a diameter of 8 to 25 μm. If the diameter is less than 8 μm, it will be difficult to impregnate the metal fiber with the molten thermoplastic resin, resulting in poor dispersion. Moreover, if the diameter exceeds 25 μm, the surface area per unit weight decreases, and the shielding effect decreases. For example, a bundle of about 500 to 5000 metal fibers is used as a raw material. The amount of metal fiber used is 5% of the total amount of thermoplastic resin and metal fiber.
0 to 85% by weight is desirable.

The metal fiber bundle is coated with molten thermoplastic resin.

The device for melting the thermoplastic resin may be any device that can plasticize and melt the resin, and an extruder used for extrusion molding of resins is suitable. be. Further, as a device for coating the metal fiber bundle with molten thermoplastic resin, conventionally known devices can be used. For example, a vL arrangement used for covering electric wires, etc. can be used. Such devices include a mandrel for introducing the metal fiber bundle, a means for continuously flowing molten thermoplastic resin from around the periphery of the metal fiber bundle exiting the mandrel, and a means for coating the metal fiber bundle with molten thermoplastic resin. There are some types of dies that are used to form metal fiber bundles into strands. Here, when the metal fiber bundle is coated with molten resin, a heating device is installed to preheat it in advance so that the molten resin does not cool down on the surface of the metal fiber bundle and can easily penetrate inside. This is desirable. Also,
It is preferable that the inlet of the mandrel has a flat shape that is slightly larger than the cross section of the gold r%ta fiber bundle, and the outlet tip is such that the metal fiber bundle, which has been made flat at the entrance, is rounded by the viscosity of the molten thermoplastic resin. In order to prevent this, it is preferable that the shape is provided with long side walls to allow the molten thermoplastic resin to flow only from above and below the flat surface of the flat metal fiber bundle.

In the present invention, a force is applied to the molten thermoplastic resin coated with the metal fiber bundle within the die or at the exit of the die so as to displace the metal fiber bundle at least once in a direction perpendicular to the axial direction. Therefore, although the die may be a normal die with a straight channel, it is preferable to have a structure in which the channel has at least one bend. That is, since the metal fiber bundle resin coating in the form of a strand extruded from the die is continuously pulled off by a tension roller or the like, its tensile force also extends into the die. Therefore, if there is a bent part in the die, the metal fiber bundle tends to become straight and is displaced in a direction perpendicular to the axial direction with respect to the molten thermoplastic resin. The larger the size of the bent portion, the stronger the force of displacement, which increases the resistance within the die. However, if the bend is smooth, even if the bend is increased, there will not be much resistance, so it can be made thicker.The size of the bend, that is, the maximum displacement width of the bend , preferably at least twice the diameter.Furthermore, if two or more bent portions are provided, the displacement of the metal fiber bundle will occur two or more times, and if two or more bent portions are provided by changing the direction of bending, The adhesion and impregnation effect of the molten thermoplastic resin into the metal fiber bundle due to displacement is further improved.

In addition, in order to promote impregnation and mixing of the molten thermoplastic resin into the metal fiber bundle, it is preferable that the flow path shape of the die inlet and/or outlet is flat or elliptical. It is preferable that the flow path is gradually narrowed.

Further, the length of the die channel is preferably 10 mm or more in order to ensure a constant residence time.

In order to displace the metal fiber bundle, in addition to providing a bend in the die flow path, while the metal fiber bundle resin coating extruded from the die outlet has plasticity, it must be moved in a straight line from the die outlet. If you use rollers etc. to take it to a position where it should not be, displacement will occur at the exit corner, so
This produces the same effect as when a bent portion is provided.

The metal fiber bundle resin coated body extruded from the die is sufficiently impregnated and adhered to the molten thermoplastic resin inside the die or at the exit of the die, and then taken off with a roller or the like, and then pelletized with a pelletizer as necessary. be converted into If the resistance is large due to the provision of bent portions, it is desirable to install upper and lower rolls in front of the pelletizer to serve as a tensioning auxiliary device. The pellets are molded into molded articles, either alone or preferably mixed with the same or other molten thermoplastic resins.

The present invention will be explained below with reference to the drawings.

The thermoplastic resin is charged from the hopper 2 of the extruder 1, melted and extruded by the screw 3, and supplied to the resin coating device 4. After the metal fiber bundle 5 is preheated by a heating device 6, it is supplied to a resin coating device 4.

The resin coating system rIL4 consists of a mandrel 7 for introducing the metal fiber bundle 5, a molten thermoplastic resin bath 8, and a die 9.

In the resin coating device 4, the metal fiber bundle 5 is impregnated and coated with thermoplastic resin, and from the die 9, the metal fiber bundle resin coated body 1
0 is extruded into a strand shape, and after cooling, the pelletizer 11
It is cut into pellets.

2 and 3 show examples of the shape of the die 9 used in the present invention. FIG. 2 shows a die 9 having a smoothly and largely bent portion 12 in the die flow path 13. The die channel 13 becomes narrower toward the outlet. FIG. 3 shows a die 9 having three relatively sharp and small bends 12 in the die channel 13. When using the die shown in FIG. 2 or 3, if the strand extruded from the die outlet section 14 is taken in the horizontal direction, the metal fiber bundle is
At point 2, a force is applied to move in a direction perpendicular to the axial direction, resulting in displacement.

FIG. 4 shows an example of another embodiment of the present invention, in which the molten thermoplastic resin is supplied from the die inlet 16, the metal fiber bundle 5 is supplied from the inlet 15, and is impregnated and coated with the thermoplastic resin. The resulting strand is extruded from the die outlet 18. In this case as well, the metal fiber bundle 5 coated with the molten thermoplastic resin near the center of the die 9 is placed at the outlet 1 of the inlet 15.
9 is given a force to displace it so that it is pressed against it.

FIG. 5 is a diagram showing another example of the present invention, in which a strand 10 extruded from a die 9 having no bent portion is moved by a roller 17 disposed at a position not parallel to the exit of the die 9. It has a structure that can be bent and removed. In this case, since the thermoplastic resin of the strand 10 has plasticity, a force is applied to the metal fiber bundle in the strand at the die exit in a direction perpendicular to the axial direction.

In the case of FIG. 5, it is of course possible to use a die 9 having a bent portion.

[Effect]

When the metal fiber bundle is displaced, the metal fiber bundle moves in the molten thermoplastic resin in a direction perpendicular to the axis.
Penetration of the molten thermoplastic resin into the metal fiber bundle is promoted,
Furthermore, when the metal fiber bundle is pressed into the channel, it expands and releases the air bubbles contained inside, which facilitates the adhesion and penetration of the molten thermoplastic resin. When a molded article is molded using the thus obtained metal fiber bundle resin coating or metal fiber bundle resin coating and thermoplastic resin, each metal fiber in the metal fiber bundle has thermoplastic properties. Since the resin adheres well, the metal fibers are well dispersed.

〔Example〕

Example 1 An apparatus having the configuration shown in FIG. 1 was used. AS from hopper 2
Resin (Nippon Steel Chemical (manufactured by Iit, Esterene AS-30)
A continuous stainless steel fiber bundle 5 (filament diameter 15 μm,
1,500 units (manufactured by Nippon Seisen ■) were supplied.

The extruder had a cylinder temperature of 170 to 200°C, a die temperature of 260°C, and a screw rotation speed of 10 rpm. The resin discharged from the extruder and the heating device 6 are heated to 230℃~2
The stainless steel fiber bundles heated to 70°C are united and pressed against the convex part by tensile force as they pass through the die shown in Figure 2, and the resin is impregnated and adhered to the fiber bundles, forming a strand-shaped metal fiber bundle resin coating. Obtained. The entrance part of this die has an elliptical shape of 1 O 1 - x 6 dragons horizontally, and the exit part has a vertical 0. It has an elliptical shape of 71 x 6 dragons, and the maximum displacement width of the bent part is 8 cranes. After cooling, this strand was sheared to a length of 6fi using a pelletizer 11 to form pellets. The shearing condition in pelletizer 11 was good.

The content rate of stainless steel fiber in this bere 7) is approximately 7
It was 0%. The obtained pellet and ABS resin were triblended so that the stainless steel fiber content was 8wt%,
A test piece of 150 m x 150 mm x 3 thick was prepared using an injection molding machine, and the shielding effect was measured and the appearance was observed.

Shield effect electric field magnetic field example! (100 MHz) 50 dB 22 dB Reference 3 Dragon Steel Plate (100 MHz) 58 dB 49 dB In addition to exhibiting a good shielding effect as described above, no lumps of fibers were observed on the surface of the test piece, and the appearance was almost good.

Example 2 Instead of As resin, CP-PS resin (manufactured by Nippon Steel Chemical Co., Ltd., Estyrene G-32) was used, and instead of ABS resin, HI-PS resin (manufactured by Nippon Steel Chemical Co., Ltd., Estyrene H-32) was used.
The sample was manufactured and measured in the same manner as in Example 1, except that 65) was used. As a result, the shielding effect was good in both the electric field and the magnetic field, similar to the results of Example 1. However, the appearance was somewhat inferior to Example 1 as a whole, with many silver stripes.

Example 3 The same raw materials and equipment as in Example 1 were used, and the die shown in FIG. 3 was employed. This die has three bent parts, and the entrance shape is vertical 10 dragon x horizontal 6 orchid.
The exit shape is 0.7nn vertically x 6fi horizontally. As a result, the shielding properties and appearance were as good as in Example 1.

Example 4 Using the same raw materials as in Example 1, a fourth
The die shown in the figure was used.

As a result, the shielding effect is 51 dB electric field at 100 MHz.
, the magnetic field was 23 dB, which was as good as in Example 1, and the appearance was also good.

Comparative Example 1 The shielding effect was measured and the appearance was observed in the same manner as in Example 1 using the same raw materials and equipment as in Examples 1 and 2, except that the mandrel and die were circular in shape and the die did not have a bent part.

Shielding effect electric field Magnetic field As/AB3 33 dB 4 dB CP/H134 dB 5 dB As mentioned above, the shielding effect was poor, and the appearance was uneven and somewhat poor, with uneven distribution of fibers in the molded product.

〔Effect of the invention〕

The electromagnetic shielding material manufactured by the manufacturing method of the present invention has a small amount of resin and can be impregnated with resin into metal fiber bundles, and is molded with excellent electromagnetic shielding properties, dispersibility, and appearance effects with a small filling rate of metal fibers. Materials can be obtained.

[Brief explanation of drawings]

FIG. 1 is a schematic diagram of an apparatus for a manufacturing method showing one example for implementing the present invention, FIGS. 2, 3, and 4 are partial cross-sectional views of a die, and FIG. 5 is a diagram for implementing the present invention. It is a schematic diagram showing another example for. 5...Metal fiber bundle 9...Dice 12...Bending part 13...Dice channel 14...Dice outlet part

Claims (4)

[Claims] (1) In a method for producing a conductive molding material in which a continuous metal fiber bundle is introduced into a molten thermoplastic resin and the metal fibers are coated with resin, the metal fiber bundle is introduced into a die or at the exit of the die, and the molten resin is coated with a continuous metal fiber bundle. A method for producing a conductive molding material, which comprises displacing a resin at least once in a direction perpendicular to an axial direction. (2) The method for producing a conductive molding material according to claim 1, which uses a die having at least one bent portion in the die flow path. (3) The method for producing a conductive molding material according to claim 1, wherein the metal fiber bundle is preheated before being introduced. (4) A die characterized in that the die flow path is provided with at least one bent portion.