JPH0260200A - Manufacture of electromagnetic wave shielding heat shrinkable resin - Google Patents

Abstract

PURPOSE:To obtain an electromagnetic wave shielding heat-shrinkable resin which is lightweight and flexible by a method wherein conductive fiber is used as a conductive material, and thermoplastic resin, whose softening temperature is lower than that of base resin of a conductive shielding resin layer, is employed as a coupling agent. CONSTITUTION:Conductive fibers 1 are collected through a coupling agent 2 formed of thermoplastic resin, whose softening temperature is lower than that of the base resin used as a base of a conductive shielding resin layer by 10-70 deg.C, to be tows, which are dried up by a dryer A and cooled down for the formation of conductive fiber tows 3. Then, thermoplastic resin, whose softening temperature is higher than that of the coupling agent 2 but lower than that of the base resin, is extruded through an extrusion molder B to coat the conductive fibers tows 3 with a resin coating 4, which is rolled through a press roll C and cut into pellets specified in length through a cutter C for the formation of conductive resin pellets 5. Next, the conductive resin pellets 5 are mixed with the base resin, which is heated and kneaded through an extrusion molder to be formed into the conductive resin, and the conductive resin is extruded into film.

Description

Detailed Description of the Invention (Industrial Field of 411) The present invention relates to a heat-shrinkable resin material for electromagnetic wave shielding, which covers electric wires such as cables and protects internal conductors from external harmful effects, mainly electromagnetic waves. Relating to a manufacturing method.

(Prior Art) Conventionally, as a method for manufacturing a heat-shrinkable resin material for electromagnetic shielding, a 5J method for making heat-shrinkable tubes for electromagnetic shielding, as described in Japanese Patent Laid-Open No. 63-2399, has been known. There is. This conventional manufacturing method uses an extrusion molding machine in which a conductive resin extrusion port and an insulating resin extrusion port are formed concentrically from the inside. This was a method of molding an electromagnetic shielding tube having a conductive shield resin layer and an insulating sheath resin layer concentrically by simultaneously extruding an insulating resin made only of thermoplastic resin.

(Problem to be Solved by the Invention) However, in such conventional methods, since a conductive phase is used as the conductive material, it is necessary to ensure the shielding effect of the conductive shield open layer. The conductive phase must be blended in a high proportion of approximately 20 Wt.% of the total conductive resin. That is, the heat shrinkable tube manufactured by this conventional method has the following problems.

■Atonement due to its large specific gravity.

■Since it is rigid and hard, it requires a long time to coat cables etc. with heat shrinkage.

■Due to the lack of flexibility, handling after covering cables, etc. is also difficult.

■High cost.

The present invention focuses on the above-mentioned problems and aims to develop a manufacturing method for manufacturing a heat-shrinkable resin material for electromagnetic shielding that has an excellent sealing effect with a small amount of conductive material.

The purpose of this problem is to solve this problem by the following means using conductive fibers as a conductive material, and to provide a manufacturing method that can manufacture a heat-shrinkable resin material for electromagnetic shielding that is lightweight, flexible, and inexpensive. do.

(Means for Solving the Problems) In order to solve the above problems and achieve the above objects, the method for manufacturing a heat-shrinkable resin material for electromagnetic shielding of the present invention includes:
A heat-shrinkable resin material for electromagnetic shielding consisting of a conductive shielding resin layer made of a conductive resin in which conductive fibers are mixed with thermoplastic resin, and an insulating sheath resin layer made of an insulating resin made only of thermoplastic resin. In the manufacturing method, long conductive fibers are bundled using a sizing agent using a thermoplastic resin whose softening temperature is 10 to 70 degrees Celsius lower than that of the base resin that forms the base of the conductive shielding resin layer to form a conductive fiber bundle. After applying a resin coating to the conductive fiber bundle with a thermoplastic resin whose softening temperature is higher than the softening temperature of the sizing agent and lower than the softening temperature of the base resin, the conductive fiber bundle is coated with a resin. a resin pellet forming step in which conductive fiber bundles are cut into predetermined lengths to form conductive resin pellets, and the conductive resin pellets and base resin are mixed, heated and kneaded with an extrusion molding machine. This method is characterized by comprising a heat-shrinkable resin material molding step of forming a molten conductive resin and extruding the conductive resin to mold a heat-shrinkable resin material.

Preferably, the conductive fibers are stainless steel fibers having a diameter of 8 to 15 μm, and the conductive fiber bundle is formed by bundling 500 to 5000 of the stainless steel fibers.

In addition, the cutting length of the conductive resin pellet is 4 to 10 mm.
The mixing ratio of the conductive resin pellets and the base resin is preferably set so that the conductive fibers account for 4 to 5% of the total amount.

(Example) The embodiments of the present invention will be described above based on the drawings.

In addition, in explaining the examples, as a heat-shrinkable resin material,
Taking the heat-shrinkable film F as an example, a method for manufacturing the heat-shrinkable film F will be described.

First, the structure of the heat-shrinkable film F will be explained with reference to FIG.

This heat-shrinkable film F is made of conductive shield resin 1 [10
It has a two-layer structure in which 0 and an insulating sheath resin layer 200 are bonded together. Note that the insulating sheath resin layer 200 is
It is formed wide so that both ends in the width direction protrude by 1 to 5 mm from both ends of the conductive shield resin layer 10O.

One conductive shield resin layer 100 is made of a conductive resin in which conductive fibers are mixed into a thermoplastic resin, and the other insulating sheath resin layer 200 is made of an insulating resin made of only a thermoplastic resin. It is something.

The conductive resin of the conductive shield resin layer 10O and the insulating resin of the insulating sheath resin layer 200 are, for example, ethylene-
Thermoplastic resins such as vinyl acetate copolymer, ethylene-ethyl acrylate copolymer, polyethylene, polyvinyl chloride, crosslinked polyethylene, ethylene propylene rubber, butyl rubber are used, and flame retardants, pigments, lubricants, etc. are added as necessary. The thermoplastic resins used for the conductive resin and the insulating resin are preferably a mutually compatible combination, but they do not have to be the same resin.

The conductive fiber 1 is preferably 5US304 stainless steel fiber (wire diameter 8 μm to 15 μm), but nickel plated glass fiber (wire diameter 10 μm to 2:3 μm), nickel plated carbon fiber (wire diameter 8 μm to 15 μm), etc. You can also use it conveniently.

Next, a method for manufacturing this heat-shrinkable film 17 will be explained.

This manufacturing method is broadly divided into an Ia fiber bundling step, a conductive resin pellet formation step, and a film forming step.

First, in the fiber bundling process, as shown in Figure 1, long continuous conductive fibers are soaked in a sizing agent 2 made of thermoplastic resin, dried and cooled in a dryer, and bundled into long lengths. This is a process of "JJ-making" the conductive fiber bundle 3.

To explain specifically, the conductive fiber l has a wire diameter of 8 g.
m stainless steel 111 fibers were used, and the sizing agent 2 was
A solution obtained by dissolving 100 parts by weight of an ethylene-vinyl acetate copolymer having a softening temperature of 85 DEG C. and a fluidity of 400 g/lomin in a solvent of 900 ml of trichlorethylene is used.

Then, a sizing agent 2 was prepared by heating this conductive fiber 1 to 50°C.
2,850 conductive fiber bundles 3 are formed.

Here, when converging the conductive 111 fibers with the sizing agent 2, the resin group impregnated into the conductive fiber bundle 3 is adjusted to be 15% by weight of the conductive fiber bundle 3.

In the next process of forming conductive resin pellets, as shown in Figure 1, a thermoplastic resin (ethylene-vinyl acetate copolymer with a softening temperature of 85°C), which is the same as the thermoplastic resin used for sizing agent 2, is placed in an extrusion molding machine. After applying a pressure roll C to the conductive fiber bundle 3 to coat the conductive fiber bundle 3, the conductive resin pellets 5 as shown in FIG. This is the process of fA construction.

The amount of the resin layer PA4 is such that 9 of the conductive fibers 1 including the sizing agent 2 is 10w% to the entire conductive resin pellet 5.
40wt% (most preferably 20w% to 30w%)
Adjust so that By the way, conductive fiber l is low
If it is less than L%, the resin layer) υ4 will increase compared to the conductive fiber, so the outer diameter of the conductive resin pellet 5 will become thick (which makes molding work difficult. Since the amount of coating 4 is small, dispersion is poor when the film is heated and melted in the subsequent film formation step, resulting in variations in conductivity as a whole.

The next film forming step is a step of forming the conductive shield resin layer 100 and the insulating sheath resin layer 200 into film shapes using an extrusion molding machine (not shown).

First, when molding the conductive shield resin layer 100, an ethylene-vinyl acetate copolymer with a softening temperature of 135°C and a fluidity of 15 g/10 m1n is used as a base resin, and a material obtained by mixing conductive resin pellets 5 with this base resin is used. shall be.

Here, the conductive resin pellets 5 and the base resin are mixed at a ratio of 1 ootif part of the conductive resin pellets 5 to 500 parts by weight of the base resin, and the conductive fibers l are 500 parts by weight of the whole.
wt,%.

Further, the conductive resin pellets 5 are evenly mixed into the base resin.

Then, the material obtained by mixing the conductive resin pellets 5 and the base resin is supplied to an extrusion molding machine whose cylinder temperature is set to 200°C. These materials are heated and melted within the extruder, and at the same time, the conductive fiber bundle 3 is unbundled by the shearing force of the screw.

Then, the conductive fiber bundle 3 becomes a single conductive fiber L, which is uniformly dispersed in the molten thermoplastic resin, and is extruded from a nozzle in the form of a film.

The sizing agent 2 and resin 4 of the conductive resin pellet 5 are made of a resin with a softening temperature of 85°C, and the base resin is a resin with a softening temperature of 135°C, so that the sizing agent 2 and resin liquid 4 of the conductive resin pellet 5 are used.
The softening temperature of υ4 is 50° C. lower, that is, when heated in an extruder, the sizing agent 2 and the resin coating 4 begin to melt earlier than the base resin. Therefore, the conductive fiber bundle 3 is easily unbundled by the shearing force of the screw, becomes a single conductive fiber 1, and quickly and uniformly disperses in the molten resin.

The photograph in FIG. 4 shows the state of dispersion of the conductive fibers 1 of the conductive shield resin layer 100, which was prototyped to satisfy all the requirements of the above embodiment. As is clear from this photograph, according to the method of Example E, it is possible to manufacture a conductive shield resin layer 100 in which conductive fibers 1 are uniformly dispersed.

In addition, when molding the insulating sheath fat-breakable layer 200, the softening temperature is 135° C., and the fluidity is 15 g/10 m1n.
The material used is only ethylene vinyl acetate copolymer, and this material is fed into an extrusion molding machine whose cylinder temperature is set at 200°C and molded into a film.

Then, the conductive shield resin layer 10O formed as described above and the insulating sheath resin layer 200 are bonded together by heat compression bonding or adhesive bonding.

Note that the pressure bonding conditions and bonding conditions are described below.

[Crimping conditions] 200°C, 1 kg/cm” x 2 minutes [Adhesive conditions] Rubber or acrylic adhesive at room temperature 50 kg/am2 x 1 minute Meda electrical shielding resin layer 10O and insulating sheath resin j1
The heat-shrinkable film F for electromagnetic shielding is completed by irradiating the film with the glue 200 together with an electric r-ray accelerator, then heating it, stretching it in the longitudinal direction, and cooling and hardening it. Note that the electron beam irradiation conditions, stretching conditions, and cooling conditions are described below.

[Electron beam irradiation conditions] 0 Mrad [Stretching conditions] 2 times at I50 [Cooling conditions] Cooling with constant tension while maintaining strain Also, regarding how to use the heat-shrinkable film F, see Japanese Patent Application No. 62 -25
Since this is the same as No. 7983, the explanation will be omitted here.

[Volume resistivity] Initially lXl0'Ωcm After heat cycle 7 x 10°Ωcm (Heat cycle: -1 hour at 40°C, 5 minutes at room temperature, 1 hour at 90°C
Perform 6 cycles of 5 minutes at room temperature. ) [Film shrinkage time 1 1 to 2 minutes (1 m) at 200°C In other words, in the method of this example, the conductive fibers, which are the conductive material, can be uniformly dispersed, so the film can be manufactured by this method. The heat-shrinkable film F can obtain a sufficient shielding effect even though the amount of conductive fibers is edible, and has historically been used to prevent damage to cables, etc. due to heat shrinkage.
It takes less time. In addition, since the conductive fiber content is small, the conductive shielding resin layer can be formed into a thin wall, and the bottle is lightweight and highly flexible.
Handling is also improved. Moreover, it is also possible to reduce costs.

Next, a comparative example will be given to clarify the effect of the method of this embodiment.

[Comparative Example I] Ethylene-vinyl acetate copolymer with a softening temperature of 135° C. and a fluidity of 15 g/10 ml was bundled into conductive fibers using a sizing agent dissolved in a trichlorethylene solvent to form a conductive fiber bundle of 5 mm without resin coating. When a thermoplastic resin was mixed with the cut pieces so that the conductive fibers accounted for 5 wt% of the total and extruded under the same conditions as in the example to make a prototype heat-shrinkable film, the conductive fibers did not unbundle. Since it remains in the conductive shielding resin layer, the volume resistivity was 1.

[Comparative Example 21 A conductive fiber bundle bundled with the same binding agent as in Example was cut into 5 mm lengths without resin coating, and the thermoplastic resin was adjusted so that the conductive fibers accounted for 5 wt% of the total. When a heat-shrinkable film was produced by extruding the conductive fiber bundles under the same conditions as in Examples, the conductive fiber bundles were partially unbundled or had poor dispersibility as a whole, and the volume resistance was 106 Ωcm. Example 31 A heat-shrinkable film was experimentally produced by changing the example described in +iii only in the following points.

(2) Ethylene-ethyl acrylate, which has a softening temperature of 90°C and a fluidity of 116 g/10 m1n, is commonly used as the sizing agent, PA fat cover, and base resin.

■The amount of resin impregnated into the conductive fiber is 10% of the conductive fiber bundle.
Adjust so that it is wL%.

The photograph in Figure 5 shows the results of this trial production. As is clear from this photograph, although some of the conductive fiber bundles were unbundled, the overall dispersibility was poor.

Although the embodiments of the present invention have been described above in detail with reference to the drawings, the specific configuration is not limited to these embodiments, and the present invention may include design variations within the scope of the invention. included.

For example, in the embodiment, a method for manufacturing a heat-shrinkable film has been described using a heat-shrinkable film as an example of the heat-shrinkable resin material, but the present invention may also be applied to a method for manufacturing a heat-shrinkable tube.

In addition, the manufacturing method of the heat-shrinkable tube is as follows: Only the final molding step is the Jj method for manufacturing heat-shrinkable films, and the material is molded into a hollow cylindrical shape and extruded.

Further, in the examples, the conductive shield resin layer and the insulating sheath resin layer are separately molded, but they may also be formed by co-extrusion. By doing so, there is no need for heat-pressing or bonding, and manufacturing time can be shortened.

In addition, the type of thermoplastic resin used for the sizing agent and FA fat-coated base resin, the length of the conductive resin pellets, the mixing ratio of the conductive resin pellets and the base resin, the extrusion conditions in the molding process, etc. must be strictly controlled. It is not necessary to do exactly as shown in the examples. Therefore, examples of such changes and necessary conditions are listed below.

[Conductive fiber] First, when stainless steel fiber is used as the conductive #a fiber, the wire diameter is 8 μm w 15 μm, and the number of bundled fibers is 50.
The number is preferably 0 to 5000.

In addition to stainless steel fibers, nickel-plated glass fibers (wire diameter: 10 μm to 23 μm), nickel-plated carbon fibers (wire diameter: 8 μm to 15 μm), etc. can be used.

[Sticting agent] The sizing agent is a thermoplastic resin such as ethylene-vinyl acetate copolymer ethylene-ethyl acrylate copolymer, polyethylene, or polyvinyl chloride (softening temperature 60°C to 100°C).
) dissolved in a solvent such as toluene, xylene, trichloroethylene, dichloroethylene, etc. in an amount of 5 wL% to 20 wL% can be used.

In addition, the resin impregnated into the conductive fiber bundle 3! 1t is exactly 1
Although it does not have to be 5 wj%, the conductive fiber bundle 3 (7)
3WL% to 20W% (most preferably 7WL%)
~12wL%). By the way, :3
If it is more than 20W%, the tow of the conductive fiber bundle 3 will come apart or the fibers will break at 1"L of fluff, and if it is more than 20W% -L, the viscosity of the resin liquid will increase. This makes the work difficult.

[Coating resin] The coating resin does not have to be the same resin as the thermoplastic resin used for the sizing agent, and must be compatible with the sizing agent, have a softening temperature higher than the softening temperature of the sizing agent, and have a softening temperature higher than that of the base resin. Different resins may be used as long as they have a softening temperature or lower. However, the sizing agent and resin coating have a softening temperature of 1
It is necessary to lower the temperature by 0 to 70°C.

[Conductive resin pellet] The cutting length of the conductive resin pellet is 1mm"10mm
(Most preferably, the length is within the range of 4 mm to 6 mm).

[Mixing ratio of conductive resin pellets and base resin] The mixing ratio of conductive resin pellets and base resin may be adjusted so that conductive #a male accounts for 4 to lowL% of the entire conductive resin. Incidentally, when the conductive region tIct is 4wL% or less, the volume resistivity ρ (shielding effect dβ) varies, and when it is 10wL% or more, the volume resistivity ρ (shielding effect dβ) does not change much.

[Extrusion Conditions] The cylinder temperature of the extrusion molding machine in the molding process needs to be 30°C to 70°C higher than the softening temperature of the base resin.

(Effects of the Invention) As explained above, in the method for manufacturing a heat-shrinkable resin material for electromagnetic shielding of the present invention, a base serving as a base of a conductive shielding resin layer is added to a binding agent for binding conductive fibers. Since we used a thermoplastic resin that is 10 to 70 degrees Celsius lower than the softening temperature of the resin, during the resin material molding process, the sizing agent begins to melt earlier than the base resin due to heating, and the conductive fibers can be quickly and easily melted with fewer cuts. Uniformly dispersed within the molten resin. That is, it is possible to produce a heat-shrinkable film or tube for electromagnetic shielding with excellent shielding effect by reducing the amount of conductive fibers.

Furthermore, as mentioned above, by incorporating a small amount of conductive fiber, ■ it is light because of its low specific gravity, and ■ it is highly flexible, so it takes less time to coat cables etc. by utilizing their heat shrinkability. , 2) It is easy to handle after coating cables, etc., and 2) it is possible to produce a heat-shrinkable film or tube for electromagnetic shielding at low cost.

[Brief explanation of the drawing]

Figure 1 shows 5 of the heat shrinkable film for electromagnetic shielding of the present invention.
! FIG. 2 is a perspective view showing conductive resin pellets, and FIG. 3 is a heat shrinkable electromagnetic shield manufactured by the manufacturing method of the present invention. A cross-sectional view showing the film, FIG. 4 shows the conductivity f of the conductive shield resin layer manufactured by the method of the example.
Fl! FIG. 5 is a photograph showing the state of dispersion of conductive fibers in the conductive shield resin layer manufactured by the method of Comparative Example 3. F-... Heat shrink film 10O... Conductive shield resin layer 200... Insulating sheath resin layer l... Conductive fiber 2... Bundling agent 3... Conductive fiber bundle 4... Resin layer weight 5... conductive resin pellets

Claims (1)

[Claims] 1) Consisting of a conductive shield resin layer made of a conductive resin in which conductive fibers are mixed into a thermoplastic resin, and an insulating sheath resin layer made of an insulating resin made only of thermoplastic resin. In a method for manufacturing a heat-shrinkable resin material for electromagnetic shielding, long conductive fibers are formed using a sizing agent using a thermoplastic resin whose softening temperature is 10 to 70 degrees Celsius lower than that of the base resin that forms the base of the conductive shielding resin layer. a fiber bundling step of bundling to form a conductive fiber bundle; After applying the coating, a resin pellet forming step of cutting the resin-coated conductive fiber bundle into a predetermined length to form conductive resin pellets, and mixing the conductive resin pellets and base resin and extruding them. A heat shield for electromagnetic shielding, comprising: a resin material molding step of heating and kneading in a molding machine to form a molten four-conductive resin, and extruding this conductive resin to mold a resin material. A method for producing shrinkable resin material. 2) The conductive wire fibers are stainless steel fibers with a wire diameter of 8 to 15 μm, and the conductive fiber bundle is made of stainless steel fibers with a wire diameter of 50 μm.
The cutting length of the conductive resin pellets is set to 4 to 10 mm, and the mixing ratio of the conductive resin pellets to the base resin is adjusted such that the conductive fibers account for 4 to 1 of the total.
The method for producing a heat-shrinkable resin material for electromagnetic shielding according to claim 1, wherein the content is set to 0 wt%.