JPH0957818A - Screen mesh for extrusion of resin composition and method for producing extruded product using the same - Google Patents

Abstract

(57) Abstract: A screen mesh for resin composition extrusion capable of exhibiting excellent corrosion resistance and abrasion resistance and capable of removing fine foreign matter, and a method for producing an extrusion molded product capable of continuous extrusion molding for a long time. The purpose is to provide. SOLUTION: The screen mesh is installed in an extruder and removes foreign matter in an extruded material during extrusion, wherein the screen mesh is 49.0 to 51.
It is characterized in that it is composed of a Ni—Ti based alloy wire rod containing 5 atomic% of nickel and has a film containing titanium oxide and having a thickness of 0.1 to 2.0 μm on its surface.
Further, the resin composition is extruded by using an extruder having this screen mesh in front of the extrusion screw in the extrusion direction.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a resin composition capable of stably removing fine foreign matters in an extrusion coating material (hereinafter, abbreviated as extrusion material) such as rubber and plastic used for power cables and the like. The present invention relates to a screen mesh for extrusion and a method for manufacturing an extruded product using the screen mesh.

[0002]

2. Description of the Related Art In recent years, in an insulated power cable (hereinafter abbreviated as power cable) formed by extruding a resin composition such as rubber or plastic on a conductor, an insulating layer is used when used under a higher voltage. The concentration of the electric field is caused by the protrusions generated at the interface between the insulating layer and the semi-conductive layer with the foreign substances present in the semiconductor layer and the foreign substances in the semi-conductive layer as nuclei, which causes the generation of electrical trees. Or breakdown may occur. Therefore, in order to increase the voltage and improve the reliability of the power cable, it is necessary to appropriately remove the foreign matter when the layers are extruded. Removal of foreign matters during extrusion molding is usually performed by attaching a screen mesh made by weaving a wire rod made of stainless steel such as SUS304 and SUS316 having excellent corrosion resistance to the tip of an extruder.

[0003]

In recent years, in order to increase the reliability of a power cable, especially in high-voltage power transmission, a long power cable has been used in which the number of connection portions causing insulation breakdown is reduced. When manufacturing such a long power cable, it is necessary to continuously extrude the semiconductive layer and the insulating layer formed on the conductor for a long time.

However, various additives such as fillers such as carbon black are compounded in the extruded materials to be extruded or extruded, such as rubber and plastic. Therefore, when the extruded material in which such an additive is blended at a high ratio passes through the screen mesh, the wire constituting the screen mesh becomes worn due to the additive, particularly carbon black, and the wire becomes thin, and in some cases, The wire will be broken. As a result, it becomes impossible to remove fine foreign matters in the extruded material during extrusion. If a material containing a trace amount of acid such as ethylene-vinyl acetate copolymer (EVA) is used as the extruding material, the wire forming the screen mesh may be corroded by the acid.

As described above, since the conventional screen mesh has insufficient corrosion resistance and abrasion resistance, it takes a short time to break and there is a limit to continuous extrusion molding. For this reason, there arises a problem such as a decrease in productivity when manufacturing a long power cable.

The present invention has been made in view of the above points, and a screen mesh for resin composition extrusion capable of exhibiting excellent corrosion resistance and abrasion resistance and capable of removing fine foreign matter, and continuous extrusion molding for a long time are provided. The aim is to provide a process for the production of extrudates which is possible.

[0007]

In order to solve the above-mentioned problems, the present invention is a screw mesh which is installed in an extruder and removes foreign matters in an extruded material during extrusion, wherein the screen mesh is used. , 49.0-51.
A resin composition comprising a Ni-Ti alloy wire rod containing 5 atomic% of nickel and having a film having a thickness of 0.1 to 2.0 μm containing titanium oxide on its surface. A screen mesh for extrusion is provided.

Ni used as a material for the wire rod of the present invention
In the -Ti alloy, if the nickel content is less than 49.0 atomic%, a screen mesh having sufficient mechanical properties cannot be obtained, and the elongation is particularly insufficient. On the other hand, if the nickel content exceeds 51.5 atomic%, the workability of the Ni—Ti alloy is deteriorated.
It becomes difficult to obtain a thin wire rod. The nickel content in the Ni-Ti alloy is preferably 50.6-5.
It is 1.5 atom%.

Further, in this Ni--Ti alloy, F
One or more elements selected from the group of alloy elements of e, Co, Cr, V and Nb may be contained, and in this case, the content of elements other than nickel and titanium is The total content is preferably 0.01 to 5.0 atom%. In addition, the alloy element containing Cu (F
One, two or more elements selected from e, Co, Cr, V and Nb) may be contained in a proportion of 1 to 10 atomic% in total. By adding these elements in a predetermined ratio, it is possible to improve the mechanical properties of the screen mesh made of the obtained Ni-Ti alloy, and further improve the corrosion resistance depending on the type of the added element. It will be possible. However, if the content of the additive element exceeds the above range, the workability of the Ni—Ti alloy becomes poor, and it becomes difficult to obtain a thin wire, which is not practical.

When these elements are added to the Ni-Ti alloy, the content of nickel is 49.5-5.
It is preferably 1.5 atomic%. The lower limit of the nickel content is different because the additive element is replaced with Ni and / or Ti when added to the alloy.

The Ni--Ti alloy may contain inevitable impurities such as Si and S. In the present invention, the thickness of the film formed on the surface of the wire is 0.1
Limited to 2.0 μm. When the thickness of the coating is less than 0.1 μm, the coating is worn due to its thinness and Ni-Ti
Corrosion and wear develop even in base alloy base materials. Although the corrosion of the base material is extremely smaller than that of the stainless steel base material, the wear amount is larger than that of the Ti-based oxide film. On the other hand, when the film thickness exceeds 2.0 μm, cracks occur because the film is too thick, and the film peels off due to passage of the extruded material during extrusion molding, and the desired corrosion resistance and wear resistance are not obtained, and the screen The mesh breaks.

As a method of forming a film made of an oxide containing titanium oxide as a main component on the wire, for example, a method of subjecting the above NiTi alloy wire to heat treatment at a temperature of 250 to 800 ° C. in the atmosphere can be mentioned. To be Furthermore, the oxide film can be applied to the wire by using a vacuum evaporation method, a sputtering evaporation method, or the like. In the heat treatment method, when the heat treatment temperature is lower than 250 ° C., it takes a long time to obtain an effective film thickness (0.1 to 2.0 μm), which is not practical. If it exceeds 800 ° C., the screen mesh may be broken by the pressure of the resin during extrusion due to the decrease in mechanical strength.

The heating time can be appropriately selected depending on the heating temperature, but it is preferably not longer than 5 hours. For example, at 600 ° C., a heat treatment for 30 minutes to 2 hours can form a film having a film thickness within the range of the present invention.

In the present invention, this heat treatment is N
It is performed after weaving a wire rod made of an i-Ti alloy. This is because, even if heat treatment is performed in the state of the wire, when the wire is woven, the film formed on the surface may be peeled off, and sufficient corrosion resistance and wear resistance may not be exhibited.

The screen mesh of the present invention having such a coating preferably recovers its original shape when deformed by 2% or more at room temperature. The present invention also provides a method for producing an extruded product, which comprises extruding a resin composition using an extruder having the screen mesh in front of an extrusion screw in the extrusion direction.

As the extruded material (resin composition) used in the present invention, ethylene propylene rubber, ethylene-propylene-diene rubber, chloroprene rubber, silicone rubber, acrylic rubber, fluorine rubber, rubber such as natural rubber, polyethylene, polypropylene, etc. Olefins such as chlorinated polyethylene, ethylene-vinyl acetate copolymer, ethylene-acrylic acid copolymer, ethylene-methacrylic acid copolymer, ethylene-methyl acrylate copolymer, ethylene-ethyl acrylate copolymer Plastics such as polymers, polyamides, polyvinyl chloride, tetrafluoroethylene perfluoroalkyl vinyl ethers, tetrafluoroethylene-hexafluoropropylene copolymers, saturated polyesters, etc., and fillers and other additives Mention may be made of a pound.

The extruded product obtained by using the screen mesh for extruding the resin composition of the present invention includes an inner semiconductive layer, an outer semiconductive layer, an insulating layer and an extruded film in a rubber / plastic insulated power cable. be able to. Such an extruded product is suitable as an extrusion molding material used for a connection portion of a power cable or a material of an electric insulating portion in a prefabricated joint.

After extruding the resin composition using the screen mesh of the present invention, the oxide film is
Although it is slight, it wears and the film thickness decreases.
Even in such a case, after washing the screen mesh, heat treatment is performed again under predetermined conditions to give 0.1-2.
If an oxide film having a thickness of 0 μm is formed, it can be used repeatedly several times.

As described above, the resin composition extrusion screen mesh of the present invention contains titanium oxide and has a thickness of 0.1.
~ 2.0μm coating on the surface, the nickel content is 4
It is characterized by being composed of a wire made of NiTi-based alloy of 9.0 to 51.5 atomic%.

The film having this thickness exhibits corrosion resistance and wear resistance against additives such as acid and carbon black contained in the extruded material (resin composition). Therefore,
Even if extrusion molding is continuously carried out for a long time with a large extrusion amount, fine foreign matters in the extruded material can be sufficiently removed without breaking.

The extrusion method of the present invention is characterized in that the resin composition is extruded using an extruder having the screen mesh in the extrusion direction in front of the extrusion screw. In the extrusion method of the present invention, since a screen mesh having excellent corrosion resistance and abrasion resistance is used, it is possible to lengthen the period until the screen mesh breaks, which is required for manufacturing a long power cable. A level of continuous extrusion can be realized. Therefore, the productivity in manufacturing the power cable is improved.

[0022]

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, the present invention will be described more specifically by showing Examples and Comparative Examples of the present invention. Example 1 A wire body having a wire diameter of 40 μm and made of a Ni—Ti alloy containing 51.0 atomic% of nickel and the balance being Ti was woven into a mesh body of 250 mesh (opening diameter of 62 μm). The mesh main body was heat-treated at 600 ° C. for 1 hour in the air, and then air-cooled to form a 0.8 μm-thick film on the mesh main body, to fabricate the screen mesh of Example 1. In addition,
The film thickness was measured by Auger spectroscopy.

[0023]

[Table 1]

Further, as shown in Table 1 above, screen meshes of Examples 2 to 4 and Comparative Examples 1 to 6 were produced. That is, a mesh main body was produced in the same manner as in Example 1 except that a wire made of a Ni—Ti alloy containing another element having a composition as shown in Table 1 was used and heated under the conditions shown in Table 1. Example 2-4 after processing
The screen mesh of was produced. The film thicknesses of the screen meshes of Examples 2 to 4 are 1.1 to 1.
It was 4 μm.

In addition, the mesh bodies prepared in Examples 1 to 4 were not subjected to the heat treatment, and the screen meshes of Comparative Examples 1 to 4 were prepared. Similar meshes were prepared using SUS316 and SUS304, and the comparisons were made. Examples 5 and 6 are given. The thickness of the screen mesh film of each of the comparative examples was 0.01 μm.

The screen meshes of Examples 1 to 4 and Comparative Examples 1 to 6 obtained as described above were attached to an extruder, and the resin mesh was extruded using the screen meshes. The amount of water was observed as follows. First, Examples 1 to 4 and Comparative Examples 1 to 1
6 screen meshes, each with a cylinder diameter of 65
It was attached to an extruder of mmφ. On the other hand, the resin composition was obtained by mixing 100 parts by weight of ethylene vinyl acetate (EVA) resin having a melt index of 10 with 65 parts by weight of conductive carbon black and 0.3 parts by weight of an antioxidant. An EVA resin composition which is a conductive mixture was used.

This resin composition was prepared by using the above extruder.
Continuous extrusion was performed at three types of extrusion amounts (500 kg, 1 t (ton) and 2 t (ton)), and the fracture state and the scraped amount of each screen mesh at that time were observed with a microscope. The results are shown in Table 2 below.

[0028]

[Table 2]

As is clear from Table 2, the screen mesh of the present invention (Examples 1 to 4) extruded an extruded material containing a trace amount of acid in the material and further containing an additive at a passing amount of 1 t. In this case, the maximum reduction in wire diameter is 0.5μ
m, and even when extruded with an extrusion amount of 2t, the wire material constituting the screen mesh is scarcely scraped.

On the other hand, screen meshes having no oxide film having the thickness specified in the present invention (Comparative Examples 1 to 4)
Is the decrease in wire diameter when extruding 1t material,
It is 2.1 μm, which is more than four times that of the present invention. Furthermore, when the extrusion rate is increased to 2 tons, the reduction rate is 18
Since the amount of wear is large, the level of foreign matter removal is significantly reduced. In particular, in Comparative Examples 5 and 6, when extruding for a long time of 500 kg or more, the constituent wires of the screen mesh were broken, and therefore did not play a role of removing foreign matters.

[0031]

As described above, the screen mesh for extruding the resin composition of the present invention is
Ni-containing 49.0-51.5 atomic% nickel-
Since it is composed of a Ti-based alloy wire and has a film containing titanium oxide and having a thickness of 0.1 to 2.0 μm, it exhibits excellent corrosion resistance and wear resistance and can remove fine foreign matter. is there.

Further, in the method for producing an extruded product of the present invention, since the resin composition is extruded using an extruder having the screen mesh in the extrusion direction in front of the extrusion screw, continuous extrusion molding for a long time is possible. Thus, it is possible to continuously obtain an extruded product of stable quality.

Claims (2)

[Claims] 1. A screw mesh which is installed in an extruder and removes foreign matter in an extruded material during extrusion, wherein the screen mesh is 49.0 to 51.
A resin composition comprising a Ni-Ti alloy wire rod containing 5 atomic% of nickel and having a film having a thickness of 0.1 to 2.0 μm containing titanium oxide on its surface. Screen mesh for extrusion. 2. A method for producing an extruded product, which comprises extruding a resin composition using an extruder having the screen mesh according to claim 1 in front of an extrusion screw in an extrusion direction.