Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – At least one aryl ring which is part of a fused or bridged...
Reexamination Certificate
2001-01-16
2002-10-08
Sanders, Kriellion A. (Department: 1714)
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
At least one aryl ring which is part of a fused or bridged...
C524S436000
Reexamination Certificate
active
06462121
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to olefin-based resin compositions, and more preferably halogen-free olefin-based resin compositions. These compositions are used for coating electrical cables used in automobiles. The above compositions therefore preferably satisfy the requirements of the automobile industry, as regards, e.g., wear resistance, flame resistance, tensile strength and flexibility.
2. Description of Background Information
Poly(vinylchloride) has been the primary material for automobile electrical cables. The reason is that this polymer has good mechanical strength, formability at extrusion with electrical cables, flexibility and paintability. The polymer is also an inexpensive material.
Recently, however, global environmental concerns have compelled the automobile industry to reconsider the choice of product types used for automobile parts, including the coatings of electrical cables. As a result, halogen-free resin materials are currently replacing poly(vinylchloride).
Accordingly, research has been undertaken into the wear-resistant resin compositions that do not generate toxic gases, such as halogen gases, when they are burned. Such compositions include halogen-free compositions containing a polyolefin-based polymer and a metal hydroxide as a flame retardant, as disclosed in Japanese patent applications published under Nos. HEI 7-176219 and HEI 7-78518, the disclosures of which are herein incorporated by reference in their entireties. Further, Japanese patent application published under No. HEI 7-182930, the disclosure of which is herein incorporated by reference in its entirety, describes a composition containing a polymeric material consisting of a polypropylene-type resin, a polyethylene treated with an unsaturated carboxylic acid, and an ethylene-type copolymer, on the one hand, and a metal hydroxide, on the other.
However, when the compositions described above are used in order to retard combustion or perform auto-extinction of the flame, a large amount of metal hydroxides must be added to the compositions. The mechanical strength of the compositions, such as wear resistance and tensile strength, is then greatly diminished. In order to avoid such a deterioration, polypropylene or a high-density polyethylene, which is a relatively hard resin, has been added to the compositions. However, this tends to degrade the flexibility and formability of the coated electrical cables.
SUMMARY OF THE INVENTION
An aspect of the present invention is therefore to provide an olefin-based resin composition which is preferably free of halogen and has well-balanced properties required for the coatings of electrical cables used in automobiles. These properties include wear resistance, flame resistance, tensile strength, flexibility, heat resistance and low-temperature resistance.
To this end, there is provided an olefin-based resin composition comprising:
(i) a polymeric material in an amount of 100 parts by weight which includes:
(a) about 50 to 80 parts by weight of propylene polymer portion comprising at least one propylene polymer;
(b) about 1 to 20 parts by weight of polyolefin portion comprising at least one polyolefin, a proportion of about 0.1 to 10% by weight of which is structurally modified through maleic acid anhydride treatment; and
(c) about 10 to 40 parts by weight of olefin-based polymer portion comprising at least one thermoplastic resin having a melting point of at least about 130° C. and a Shore A hardness of up to about 90; and
(ii) about 20 to 300 parts by weight of at least one metal hydroxide.
Preferably, the polyolefin portion treated with maleic acid anhydride (b) accounts for about 2 to 10% by weight of the polymeric material (i), the olefin-based polymer portion (c) accounts for about 20 to 30% by weight of the polymeric material (i), and the metal hydroxide product (ii) comprises at least one metal hydroxide in an amount of about 50 to 150 parts by weight relative to 100 parts by weight of the polymeric material (i).
Preferably yet, the metal hydroxide product (ii) comprises at least one metal hydroxide in an amount of about 70 to 90 parts by weight relative to 100 parts by weight of the polymeric material (i).
Suitably, the propylene polymer portion (a) has a melt flow rate of about 0.1 to 5 g/10 minutes.
Further, the propylene polymer portion (a) may comprise at least one of propylene-ethylene block copolymer, propylene-ethylene random copolymer and propylene homopolymer.
Preferably, the polyolefin portion treated with maleic acid anhydride (b) may at least comprise polypropylene structurally modified through maleic acid anhydride treatment.
Preferably yet, the olefin-based polymer portion (c) comprises at least one of polopropylene and propylene-ethylene copolymer.
Suitably, the metal hydroxide product (ii) is treated with silane coupling agent.
Preferably, the silane coupling agent comprises aminosilane coupling agent.
As understood from the foregoing, the olefin-based resin composition according to the invention is preferably substantially free of halogen.
The invention further concerns an electrical cable coated with such an olefin-based resin composition.
DETAILED DESCRIPTION
The above and other aspects, features and advantages of the invention will be made apparent from the following illustrative description.
All percent measurements in this application, unless otherwise stated, are measured by weight based upon 100% of a given sample weight. Thus, for example, 30% represents 30 weight parts out of every 100 weight parts of the sample.
Unless otherwise stated, a reference to a compound or component, includes the compound or component by itself, as well as in combination with other compounds or components, such as mixtures of compounds.
The propylene polymer portion (a) includes, for example, propylene homopolymer, block or random copolymer of propylene and ethylene. Preferably, the propylene polymer portion (a) has a melt flow rate (MFR) of about 0.1 to 5 g/10 min. MFR is measured according to the method based on Standard JIS K 6921-2.
Examples of such propylene polymers include RB610A (block copolymer), RB410 (random copolymer) and RB110 (homopolymer), manufactured and commercialized by TOKUYAMA CORP.
When the proportion of such propylene polymer portion exceeds the above-mentioned upper limit of about 80% by weight of the polymeric material (i), the composition obtained becomes less flexible and less formable.
Conversely, when its proportion is less than the lower limit of about 50% by weight, the composition obtained becomes less resistant to wear.
Examples of maleic acid anhydride-treated polyolefin portion (b) include polyethylene, polypropylene, polybutene, ethylene-vinyl acetate copolymer (EVA), ethylene-ethyl acrylate copolymer (EEA), ethylene-methyl acrylate copolymer (EMA), ethylene-methyl methacrylate copolymer, ethylene-propylene rubber and ethylene-butene copolymer. A preferred example is polypropylene treated with maleic acid anhydride, since it gives an inventive composition having a sufficient level of hardness and wear resistance without performing cross-linking.
The proportion of maleic acid-anhydride-treated polyolefin portion (b) in the polymeric material (i) ranges from about 1 to 20, preferably from about 2 to 10% by weight.
When its proportion exceeds the upper limit of about 20% by weight, the polyolefin portion (b) reacts strongly with the metal hydroxide, so that the tensile elongation (elongation rate at breaking point) of the composition is reduced, and its flexibility is impaired.
Conversely, when its proportion is less than the lower limit of about 1% by weight, the composition is less wear resistant.
Preferred examples of thermoplastic resins as olefin-based polymer portion (c) include polypropylene and propylene-ethylene copolymer, and mixtures thereof. Such examples include “PER R410E” and “PER T310J”, manufactured and commercialized by TOKUYAMA CORP.
The thermoplastic resin preferably has a melting point of at least about 130° C. and a Shore A hardness of up
Fujimoto Hiroshi
Hase Tatsuya
Sato Masashi
Greenblum & Bernstein P.L.C.
Sanders Kriellion A.
Sumitomo Wiring Systems Ltd.
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