JPH04101308A - Non-halogen flame retardant cable - Google Patents

Abstract

PURPOSE:To enhance the heat resistance by preparing a fire retardant sheath free from halogen content using a specific fire retardant compound, and putting this sheath as the outermost layer in the form of thin film. CONSTITUTION:A sheath 5 is extruded to cover a cable and covered with another sheath 6 which is formed with small wall thickness. The sheath 6 is formed from a fire retardant compound consisting of a mixture of over 100 parts by wt. metal hydrate and 100 parts by wt. polyolefin in which the mixing proportion of ethylene/vinyl acetate copolymer and ethylene/ethyl acrylate copolymer is 1:3. This allows accomplishing a good fire retardant cable, which meets requirements of deformation with heating and oil withstand test specified in the IES, BS sheath standards, and there is no need to construct the sheath in a bridge structure which leads to provision of good fabricating easiness and suppression of the unit price of the resultant cable.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to a non-halogen flame-retardant cable that passes the IEC332-3 flammability test.

[Prior Art] In recent years, many non-halogen flame-retardant cables have been put into practical use from the standpoint of disaster prevention, and one of the criteria for determining flame retardancy is the IE C332-3 combustion test. This test applies to cables with conductors larger than 35 mm2.
Arrange the cables in a line with a width of 200 mm or more on a vertical tray inside a metal duct at intervals of 1/2 of the finished outer diameter of the cables, burn them with a ribbon burner for 40 minutes, and after the cables have stopped burning, burn them from the bottom end of the burner. 2.5m above
Passing the test is determined by the fact that the fire does not spread to a height exceeding

For cables that use a flammable polymer such as polyethylene for the insulator and a flame-retardant sheath material that does not contain halogen, the sheath must have an oxygen index of 40 or higher to pass the above flammability test. I found out that it doesn't.

In terms of -M, a composition having an oxygen index of 40 or more, which is obtained by filling 100 parts by weight of olefin of ethylene vinyl acetate copolymer with a large amount of metal hydrate, is used as the sheath material.

[Problems to be Solved by the Invention] By the way, problems with such prior art include the following.

■Ethylene-vinyl acetate copolymer has an I
It failed the heat deformation test (heating temperature 80°C) and oil resistance test (heating temperature 70°C) required by the EC and BS sheath standards.

■In order to improve heat resistance, a technology has been developed in which a large amount of metal hydrate is filled into 100 parts by weight of polyolefin made of ethylene vinyl acetate copolymer, and this is used as a base material to form a crosslinked structure. This reduces workability and increases the cable unit price.

The purpose of the present invention is to eliminate the drawbacks of the prior art, improve heat resistance, and provide an economical and IEC
The object of the present invention is to provide a non-halogen flame-retardant cable that passes the No. 332-3 combustion test.

[Means and effects for solving the problem] In this invention, the outermost layer is coated with a thin flame-retardant sheath that does not contain halogen, and this thin coat is made of ethylene vinyl acetate copolymer and ethylene acrylate copolymer. The use of a flame retardant composition comprising a polyolefin with a mixing ratio of 13 and a metal hydrate was used, which significantly improved heat resistance6. The present invention will be described in detail with reference to the drawings. 1st
The figure is a cross-sectional view showing the structure of the non-halogen flame-retardant cable of the present invention, in which a plurality of wire cores are formed by covering a conductor 1 with an insulator 2. Figure C shows an example of three wire cores. ) The cable is made by twisting together with the inclusions 3, applying a chie 74, and extruding a sheath 5 around the outer periphery of the cable.The sheath 5 is coated with a thin sheath 6 on the outside.

This sheath 6 contains 100 parts by weight of a polyolefin having a mixing ratio of ethylene vinyl acetate copolymer and ethylene ethyl acrylate copolymer of 1.3, and 100 parts by weight of a metal hydrate.
It is formed from a flame retardant composition containing at least part by weight.

Here, the mixing ratio was determined to be 1:3 because if the ethylene ethyl acrylate copolymer is more than this ratio, the flame retardance will be insufficient, and if the ratio is less than this, good heat resistance will be obtained. Even though I don't have it.

Samples 1 to 6 having the composition shown in each column of the following Table 1 were prepared, and the results of heating deformation, oiliness, and cable combustion tests are also shown in Table 1.

(margins below c) 100 parts by weight of metal hydrate per 100 parts by weight of polyolefin in Table
The reason why the amount is more than 1 part by weight is that in Table 1 above, Samples 1.3 and 5 containing 80 parts by weight of metal hydrate failed the cable combustion test.

The inner sheath 5 contains 1 part by weight of metal hydrate per 100 parts by weight of polyolefin of ethylene vinyl acetate copolymer.
It consists of a composition containing 00 to 300 parts by weight, and an oxygen index of about 40 is suitable.

FIG. 2 shows a cross-sectional view showing the structure of a conventional non-halogen flame-retardant cable as a comparative example. This cable has three wire cores each having a cable conductor 1 coated with an insulator 2.
They are twisted together, a tape is applied to the outer periphery, and a sheath 5 is extruded and coated on the outer periphery. sheath 5
is a composition in which 100 to 300 parts by weight of a metal hydrate is blended with 100 parts by weight of a polyolefin of ethylene vinyl acetate copolymer, as in the above example,
It has an oxygen index of 40.

Table 2 summarizes the combustion test results of the non-halogen flame-retardant cable of the embodiment of the present invention and the conventional non-halogen flame-retardant cable using IEC332-3, and the test results of the sheath material.

Table 2 [Effects of the Invention] As explained above, the non-halogen flame-retardant cable of the present invention passes the heat deformation and oil resistance tests required by the IES and BS sheath standards, and is a cable with good flame retardancy. . Furthermore, since there is no need to make the sheath a cross-linked structure, workability is good and the cable unit cost can be reduced.

[Brief explanation of the drawing]

FIG. 1 is a cross-sectional view showing the structure of a non-halogen flame-retardant cable according to an embodiment of the present invention, and FIG. 2 is a cross-sectional view showing the structure of a conventional non-halogen flame-retardant cable. Figure 2 Figure 1 Figure 1...Conductor 2...Insulator 3...Inclusion 4...Tape 5...Sheath 6...Sheath

Claims (1)

[Claims] Twisting multiple insulated core wires together and applying tape,
In a cable that has a halogen-free flame-retardant sheath on the outside and a thin halogen-free flame-retardant sheath on the outermost layer, this thin sheath is made of a combination of ethylene vinyl acetate copolymer and ethylene ethyl acrylate. A non-halogen flame-retardant cable characterized in that it is formed from a flame-retardant composition comprising 100 parts by weight or more of a metal hydrate mixed with 100 parts by weight of a polyolefin having a polymer mixing ratio of 1:3.