Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – Processes of preparing a desired or intentional composition...
Reexamination Certificate
1999-08-27
2002-07-02
Hoke, Veronica P. (Department: 1714)
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
Processes of preparing a desired or intentional composition...
C523S212000, C524S405000, C524S436000, C524S437000
Reexamination Certificate
active
06414059
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to a fire-retardant resin composition having excellent mechanical characteristics, flexibility and heat resistance, as well as heat retardancy, and to a wiring material and an optical fiber cord in which said composition is used as a covering material, and other molded parts, in which no crosslinking equipment is necessary when worked.
More specifically, the present invention relates to a fire-retardant resin composition preferably suitable as a covering material for insulated wires, electric cables, and electric cords, which are used for inner and outer wiring of electric/electronic equipment, optical fiber core wires, optical fiber cords, etc., or as a molding material for power source cords, etc., or as a tube or sheet; and to a wiring material and other molded parts in which use is made of the same. More particularly, the present invention relates to a fire-retardant resin composition that is excellent in heat resistance, flexibility and resistance to scarring, which does not need a special equipment, such as a crosslinking equipment, after working, that, in particular, neither exudes heavy metal compounds nor produces a large amount of smoke or harmful gases when discarded, for example, to be buried or burned, and that can be recycled after its use, so that environmental problems may be cleared, and to a wiring material and other molded parts in which use is made of the same.
BACKGROUND OF THE INVENTION
Insulated wires, cables, and cords, which are used for inner and outer wiring of electric/electronic equipment, optical fiber cores, optical fiber cords, and the like, are required to have various characteristics, including fire retardancy, heat resistance, and mechanical characteristics (e.g. tensile properties and abrasion resistance).
For this reason, as the covering material used for these wiring materials, a polyvinyl chloride (PVC) compound and a polyolefin compound, wherein a halogen-series fire-retardant additive containing bromine atoms or chlorine atoms in the molecule is mixed, have been mainly used.
In some cases, however, when they are discarded or buried without being treated properly, the plasticizer or the heavy metal stabilizer mixed in the covering material is oozed out, or when they are burned, a harmful gas is produced from the halogen compound contained in the covering material. In some cases and in recent years, this problem has become controversial.
Therefore, wiring materials covered with a halogen-free fire-retardant material free from any risk of oozing out of toxic plasticizers or heavy metals, or generation of a halogen-series gas or the like, which involves concern about affecting the environment, are investigated.
Halogen-free fire-retardant materials secure their fire-retardancy by mixing a halogen-free fire-retardant additive in a resin. For example, a material obtained by mixing a large amount of a metal hydrate, such as aluminum hydroxide and magnesium hydroxide, as a fire-retardant additive, in an ethylene-series copolymer, such as an ethylene/1-butene copolymer, an ethylene/propylene copolymer, an ethylene/vinyl acetate copolymer, an ethylene/ethyl acrylate copolymer, and an ethylene/propylene/diene terpolymer, is used as a wiring material.
The standards, for example, of the fire retardancy, the heat resistance, and the mechanical characteristics (e.g. tensile properties and abrasion resistance) required for wiring materials of electric/electronic equipment are stipulated in UL, JIS, etc. In particular, with respect to the fire retardancy, its test method varies depending on the required level (its use to be applied) and the like. Therefore, practically, it is enough for the material to have at least the fire retardancy according to the required level. For example, mention can be made the respective fire-retardancy to pass the vertical flame test (VW-1) stipulated in UL 1581 (Reference Standard for Electrical wires, Cables, and Flexible Cords), or the horizontal test and the inclined test stipulated in JIS C 3005 (rubber/plastic insulated wire test method).
Among these, hitherto, when a halogen-free fire-retardant material is made to have a fire retardancy high enough to pass VW-1 and the inclined test, it is necessary to mix 150 to 200 parts by weight of a metal hydrate, as a fire-retardant additive, in 100 parts by weight of a resin component of an ethylene-series copolymer, such as an ethylene/1-butene copolymer, an ethylene/propylene copolymer, an ethylene/vinyl acetate copolymer, an ethylene/ethyl acrylate copolymer, and an ethylene/propylene/diene terpolymer. As a result, there is a problem that the mechanical characteristics, such as the tensile properties and the abrasion resistance, of the covering material are markedly lowered. To solve this problem, a measure is taken to lower the proportion of the metal hydrate (e.g. about 120 parts by weight of a metal hydrate, as a fire-retardant additive, to 100 parts by weight of a resin), and red phosphorus is added.
Meanwhile, wiring materials that are currently used in electric/electronic equipment, and whose covering material is a polyvinyl chloride compound or a polyolefin compound, wherein a halogen-series fire-retardant additive is mixed, are used by coloring them to be several respective colors, for example, by printing the surface of electric wires, electric cables, and electric cords, for the purpose of distinguishing the types of wiring materials and junctions.
However, halogen-free covering materials having a metal hydrate and red phosphorus mixed therein, to secure both a higher fire retardancy and mechanical characteristics, cannot be printed thereon, or they cannot be arbitrarily colored because of the color of the red phosphorus, so that they have the problem that they cannot give wiring materials that allow the types and junctions to be distinguished easily. Further, phosphorus, which will be released after discarding of the fire-retardant material containing phosphorus, poses also a problem that affects the environment; for example, pollution of water by eutrophication.
Further, wiring materials used in electric/electronic equipment are sometimes required to have a heat resistance of 80 to 105° C., or even 125° C., while in continuous use.
In that case, such a method is used where the covering material is crosslinked by an electron beam crosslinking method or a chemical crosslinking method, in order to render the wiring material highly heat resistant.
However, while the crosslinked wiring material has improved the heat resistance of the covering material, it is impossible to remelt it. Therefore it is difficult to use said material again, making the recylability thereof poor. For example, when a metal used as a conductor is recovered, the covering material has, for example, to be burned in many cases, which means that the above environmental problem involving the conventional halogen- or phosphorus-containing covering material cannot be avoided. Further, a special equipment, such as an electron beam crosslinking equipment or a chemical crosslinking equipment, has to be provided. This increases the installation cost and the cost of the resultant electrical wire, thereby degrading the general-purpose properties.
On the other hand, as a technique wherein a wiring material having a heat resistance, on the order of 80° C. to 105° C., is realized without carrying out such crosslinking, there is a technique wherein a resin having a high melting point, such as a polypropylene-series resin, is used. However, although such a resin has good heat resistance, the flexibility is poor, and when the wiring material covered with such a resin is bent, a phenomenon is observed that the surface is whitened.
This whitening phenomenon is not observed in wiring materials currently used in electric/electronic equipment and covered with a polyvinyl chloride compound. On the other hand, in the case of wiring materials covered with a halogen-free fire-retardant material wherein a large mount of a metal hydroxide is mixed, this whitening phenome
Hashimoto Dai
Kishimoto Shinnichi
Kobayashi Kazuhiko
Nishiguchi Masaki
Okubo Ken
Birch & Stewart Kolasch & Birch, LLP
Hoke Veronica P.
Riken Technos Corporation
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