JPS6091503A - Composition for shielding electromagnetic wave - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION Technical Field The present invention relates to an electromagnetic shielding composition that has excellent injection moldability and can be suitably used for electronic devices, electronic parts, and the like.

BACKGROUND TECHNOLOGY In order to industrially and inexpensively manufacture interface bus cables with low leakage radio waves used to connect peripheral devices of personal computers, for example, it is necessary to improve the connection between the core wires of the cables and the terminals. It is necessary to insulate the material and then cover it with an electromagnetic shielding material by injection molding.However, the conventionally proposed /-old materials have insufficient fluidity above the melting point or softening point of the base polymer, so they cannot fit into the mold. There were problems such as it being difficult to injection mold into the shape of the molded product, or the surface of the molded product not being smooth.

DISCLOSURE OF THE INVENTION In view of the above, the present invention proposes a novel composition for electromagnetic shielding that is excellent in both electromagnetic wave/hardness and injection moldability, and has an average degree of polymerization (P )400~80
0. A mixture of an ethylene-vinyl chloride copolymer with an ethylene component content of 05 to 5% by weight, a plasticizer, and 7/3 brass fibers with a thickness of 1 to 100 μm and a length of 0.5 to 10%. , the amount of said fibers in said mixture is greater than 45% by weight V7
The body has excellent injection moldability even when a large amount of 773 brass fiber is blended in a state plasticized with a plasticizer.

As the plasticizer, those known as those for vinyl chloride resin and No. 17 may be used. For example, phthalate esters such as di-2-ethylhexyl phthalate, di-n-octyl phthalate, diisodenyl phthalate, cytunonyl phthalate, phthalic acid mixed esters having 7 to 11 carbon atoms, tricresyl phosphate, and triphenyl phosphate. , phosphoric acid esters such as trioctyl phosphate and cresyl diphenyl phosphate, aromatic carboxylic acid esters such as trimellitic acid ester, trimesic acid ester, and pyromellitic acid ester, diethyl adipate, diisodenyl adipate, and sepa-7 These include aliphatic dibasic acid esters such as dioctyl acid, polyesters of adipic acid and sepacic acid, and chlorinated halaffins.

The amount of plasticizer is 10 to 80 parts by weight per 100 parts by weight of ethylene-vinyl chloride copolymer.

The above-mentioned ethylene-vinyl chloride copolymers used in the present invention may be used alone or in a mixture of two or more. Furthermore, if necessary, one or more of the usual compounding agents such as stabilizers, lubricants, pigments, and flame retardants that are usually compounded in vinyl chloride resins may be added. However, the amount of these components to be blended is of course limited so that the viscosity of the ethylene-vinyl chloride copolymer-based composition obtained by blending these components is within the above range.

As the stabilizer, those commonly used in the molding process of vinyl chloride resin may be used. For example, lead-based stabilizers such as dibasic lead sulfate, dibasic lead phosphite, dibasic lead stearate, tin-based stabilizers such as dibutyltin laurate, dibutyltin maleate, dibutyltin fumarate, Ba-Zn
These include composite stabilizers, composite stabilizers such as Ba-Ca composite stabilizers, and the like.

As flame retardants, those known for use in vinyl chloride resin,
For example, antimony trioxide, water-containing alumina, etc. are used.

715 brass, that is, an alloy of 70% by weight copper and 50% by weight zinc, with a thickness of 1 to 100 μm and a length of 0.5 to 10 μm, has excellent flexibility compared to other metal fibers, and has the above-mentioned properties. Since it has excellent cross-mixability with respect to the ethylene-vinyl chloride copolymer, it is essential and excellent in producing the composition of the present invention which is excellent in both injection moldability and conductivity.

The composition of the present invention consists of an ethylene-vinyl chloride copolymer, a plasticizer of 7/3 brass fiber, and other agents blended as necessary.
The amount of brass fibers is greater than 45% by weight and less than 70% by weight.

If the length of the 7/3 brass fiber is shorter than 0.5 m or the amount used is less than 45% by weight, the conductivity imparting effect will not be high;
If it is thicker than 0.007m, the nozzle of the injection molding machine will become clogged, and if the amount used is more than 70% by weight, the viscosity of the composition will increase, and in either case, injection moldability tends to decrease. show. Furthermore, if the fibers used are thinner than 1 μm, the fibers will be cut and shortened during mixing with the plasticized ethylene-vinyl chloride copolymer, resulting in poor conductivity imparting effect.

The composition of the present invention has a resistance of 0.005 to 05Ω
A sword having a volume resistivity of 5 to 0.1 Ω exhibits a particularly excellent electromagnetic shielding effect due to good surface conductivity. On the other hand, the composition of the present invention has a viscosity of 300 to 1000 at 180°C measured with a Prabender Plastograph.
When it has a viscosity of 1TL-1, particularly 400 to 1300 m-11, it exhibits particularly excellent injection moldability. The composition of the present invention having the above characteristics can be produced by adjusting the size and amount of the fibers used. Preferable 7/3 brass fibers have a thickness of 20 to 80 μm, particularly 40 to 70 μm.
It is a wind, and has a length of 1 to 6 meters, especially 2 to 4 tm. Further, the amount used thereof is preferably 50% by weight or more and 60% by weight or less in the composition of the present invention.

The composition of the present invention can be prepared by adding a plasticizer, 7/3 brass fiber, other chemicals together with the ethylene-vinyl chloride copolymer, or by adding the ethylene-vinyl chloride copolymer to the ethylene-vinyl chloride copolymer in advance. It can be mixed and manufactured using a conventional mixer such as a two-roll mixer or a Banbury mixer by various addition methods such as plasticizing with a plasticizer and then adding the remaining ingredients.

Because of its excellent electromagnetic shielding properties and injection moldability, the composition of the present invention is suitable for injection molding to cover leakage radio wave generating parts that cause radio interference in various electronic devices and electronic parts. In particular, when used as a shielding material for connectors of interface bus cables for personal computers, which are increasingly being used in households these days, radio waves, which were conventionally caused by leakage electromagnetic waves from the connectors, are removed. , television interference is greatly improved.

BEST MODE FOR CARRYING OUT THE INVENTION Next, the present invention will be explained in more detail with reference to Examples and Comparative Examples.

Table 1 shows the abbreviations of the components used in Examples and Comparative Example e and their contents. Further, in the following, all parts and q are parts by weight and weight %.

Examples 1 to 23, Comparative Examples 1 to 10 Table 2 shows the composition and properties of each example.

In addition, the compounding ratio shown for the base composition in the table is the number of parts by weight, and the ratio of 7/3 brass fiber is the weight % in the composition of the example and the comparative example.

The compositions of each example were prepared by thoroughly mixing the remaining components except for the 7/6 brass fibers on two rolls whose temperature was previously controlled at 180°C, and then pouring them into the thoroughly mixed composition on the two rolls. It was prepared by adding 7/3 brass fiber and continuing mixing.

Further, each characteristic of the Examples and Comparative Examples was measured and evaluated by the following method.

Injection moldability: A personal computer interface bus cable was prepared for injection moldability evaluation. This bus cable is a multi-core cable with an outer diameter of 1.4 m, which has a copper braided layer for shielding on top of a bundle of 24 core wires, and a protective layer made of vinyl chloride homopolymer containing a plasticizer. A connector with 25 contacts is attached to both ends of the wire, the conductor of each core wire is connected directly to the contact, and the copper braid layer is connected to the remaining one of the contacts via the drain wire. It is of structure.

Insulation is applied above the above connection, and the temperature is 50°C in that state.
A 25-ounce injection molding machine with a nozzle diameter of 25 mm was used to coat the surfaces of the connectors at both ends of the bus cable, which were housed in a temperature-controlled mold at ~70°C, as well as the surface of a portion of the cable that followed. ) temperature 180℃, extrusion pressure 5
Each Example and Comparative Example was injection molded under the condition of ob/cm.

The results were evaluated on the following five levels.

Excellent: There are no defects in the shape, and the surface is glossy.
Good smoothness.

Excellent: There are no defects in shape and the surface is smooth, but the gloss is slightly inferior.

Good: There are no defects in the shape, but there are some parts that are different on the surface.

Acceptable: There are parts near the end of the resin flow path in the mold and large t-shaped parts such as the bellows part at the base of the cable. Also, most of the surface is rough.

Not possible due to clogging of the nozzle of the injection molding machine or excessive viscosity, the intangible resistivity of injection molding is press molded under the conditions of 180℃, 100Q/cl, 5 minutes, thickness 1cm, vertical and horizontal each 10CI Measured on a sheet according to the method specified in ASTM D-991-68.

Electromagnetic shielding property: IEiCCI8PRPub, 1 for each path cable obtained from the above injection moldability evaluation.
The shielding effect was measured using the absorption clamp method according to 6. As a control, a scale was used before the injection molding of the 7-fold material.

Claims (1)

[Claims] An ethylene-vinyl chloride copolymer with an average degree of polymerization (P) of 400 to 800 and an ethylene component content of 05 to 5% by weight, a plasticizer, and a 7/6 brass fiber with a thickness of 1 to 100 μm and a length of 05 to 10 mm. A composition for electromagnetic waves 7, characterized in that the amount of the fibers in the mixture is more than 45% by weight and less than 70% by weight.