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
2002-11-04
2004-08-24
Szekely, Peter (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...
C524S416000, C524S424000, C524S436000, C524S437000, C524S464000, C524S465000, C524S466000, C524S469000
Reexamination Certificate
active
06780914
ABSTRACT:
TECHNICAL FIELD
The present invention relates to a flame retardant resin composition, or more particularly, to a flame retardant polypropylene resin composition which comprises polypropylene having improved flow melt characteristics, flame retardants, a flame retardant aid, and a tetrafluoroethylene polymer. The resin composition of the present invention has high melt tension, without deterioration of the mechanical properties of flame retardant polypropylene, and drastically enhanced characteristics of shape maintenance and flaming drip during burning.
BACKGROUND ART
As for the conventional resins used in electrical products, non-combustible, flame-retardant, or self-extinguishing resins are used for the purposes of preventing ignition, combustion or fire, which may be caused by various electrical troubles therein. In this regard, since olefin-based resins made from hydrocarbons(i.e., polypropylene) have excellent impactability, rigidity, appearance and moldability, various proposals have been made relating to flame retardancy of these resins. In particular, according to the standards of flame retardancy of electrical products, the UL specifications (UL94) of the US require a high level of flame retardancy, depending on the products and the parts. The products to be exported to the US are required to be made from materials deemed to be appropriate according to the UL specifications. In response to these requirements, researchers have developed a material of thermoplastic polyolefin resins, mixed with organic and inorganic flame retardants, and a flame retardant aid. However, the material is problematic in that it suffers from the occurrence of a flaming drip. To solve this problem, a flame retardant resin composition was proposed, wherein said composition comprises 30~80 wt % of polypropylene; 5~25% of polyethylene having a melt flow rate of 0.01~2.0 g/10 minutes (190° C., 21.18N); 10~35 wt % of an inorganic fillers selected from the group consisting of powder talc, kaoline, mica, and silica; and 3~35 wt % of decabromodiphenylether and/or dodecachloro decahydrodimetabibenzocyclocutene (Japanese Patent Publication No. Sho 55-30739). In the above patent, it was reported that polyethylene acts in effect to facilitate the melt flow drip therein during burning. However, with respect to the composition as such, if the melt flow rate (MFR, 190° C.; 21.18N) of polyethylene is low, there is a problem of insufficiency in even dispersion of polypropylene-based flame retardant resins. For this reason, an increase in melt tension is not seen, with insubstantial effects on the improvement of the properties of shape maintenance and a flaming drip. Consequently, if the amount of polyethylene in the composition is 5 wt % or less, a proper melt-drip characteristic is not obtained. Conversely, if the amount in the composition increases, the temperature of thermal deformation, rigidity, etc. deteriorate. Moreover, the superior characteristics of polypropylene are lost.
Moreover, as for the method of increasing melt tension or the temperature of crystallization of a polypropylene composition, there are several methods as follows: a method of reacting organic peroxides and cross-linking agents to crystalline polypropylene in the molten state (Japanese Patent Laid-Open Nos. Sho 58-93711, Sho 61-152754, etc.); and a method of producing polypropylene having free monomer chain branches without gel by reacting semi-crystalline polypropylene with a peroxide of a low decomposition temperature in the absence of oxygen (Japanese Patent Laid-Open No. Pyung 2-298536). In addition, as for the other methods of enhancing melt visco-elasticity (e.g., melt tension), researcher have proposed a composition of a mixture of polyethylene or polypropylene of different specific viscosities or molecular weights, or a method of obtaining such a composition by means of multi-step polymerization. For example, the following methods have been proposed: a method of extrusion in the temperature range of the melting point to 210° C. after adding 2~30 weight parts of polypropylene of ultra-high molecular weight to 100 weight parts of commonly-used polypropylene (Japanese Patent Publication No. Sho 61-28694); a method of multi-step polymerization, yielding an extrusion sheet which comprises two components of polypropylenes of different molecular weights, having a limiting viscosity number ratio of 2 or higher (Japanese Patent Publication No. Pyung 1-12770); a method involving a polymer of 1~10 wt % of polyethylene of low viscosity; a method of melt-mixing three types of polyethylenes of different viscosities and molecular weights; a method of multi-step polymerization of polyethylene of ultra-high molecular weight having limiting viscosity number of 20 dl/g or higher, wherein less than 0.05~1 wt % of the polyethylene is obtained(Japanese Patent Publication No. Pyung 5-79683); and a method of multi-step polymerization of less than 0.05~1 wt % of polyethylene of ultra-high molecular weight having limiting viscosity number of 15 dl/g or higher by means of using 1-butene or 4-methyl by way of a polymerizer of a specific alignment, wherein (Japanese Patent Publication No. Pyung 7-8890).
With respect to the various compositions or the methods of preparation thereof as proposed in prior art, those methods enhance melt tension of polyolefin to a certain extent. However, there are problems of inadequacy of recycling usability with those cross-linked compositions in addition to the problems of low rigidity at high temperature. Furthermore, with respect to those using polyethylene of high viscosity, there are many factors which need improvements: e.g., an increase in electricity consumption due to an increase in current load at the motor of a molding machine, limitation in productivity, and low thermal stability. Moreover, with respect to the method of preparing polyolefin polymers of high molecular weights, according to said method of multi-step polymerization, it is difficult to control a low polymerization level in olefin (co)-polymerization for producing a small amount of polyolefin of high molecular weight In addition, it requires low polymerization temperature for producing polyolefin of sufficiently high molecular weight. The method also requires reconstruction of the process, which all leads to lowering of productivity of polyolefin.
In the end, with respect to the prior art as mentioned above, it brings about insufficient enhancement in terms of melt tension of polypropylene and its crystallization temperature. In particular, a composition having superior rigidity and moldability has not been developed as of yet, which simultaneously satisfies the characteristics of shape maintenance, and a flaming drip or melt drip at the time of burning of a flame retardant polypropylene resin composition comprising a halogen-based flame retardant.
DISCLOSURE OF INVENTION
In solving these problems as mentioned above, the objective of the present invention lies in providing a flame retardant polypropylene resin composition having improved characteristics of shape maintenance and a flaming drip.
The flame retardant polypropylene resin composition of the present invention comprises (A) a polypropylene resin having a melt flow rate (hereinafter MFR) of 1.5~40 g/10 minutes at 230° C. and a 2.16 kg load; (B) at least one of flame retardants and a flame retardant aid; and (C) 0.10~3 wt % of a tetrafluoroethylene polymer.
With respect to the flame retardant polypropylene resin composition of the present invention, the polypropylene resin refers to a propylene &agr;-olefin block copolymer having 50 wt % or more of propylene polymer units or a propylene homopolymer. In other words, the polypropylene resin used in the present invention refers to a crystalline polypropylene homopolymer, or a copolymer of propylene and one or more compounds selected from the group consisting of 1-butene, 1-pentene, 1-hexene, 4-methylpentene, 1-heptene, 1-octene, and 1-decene. The melt flow rate of the polypropylene resin should be 1.5~40 g/10 minutes, or preferably 2~40 g/10
Her Man-Seang
Hong Jong-Su
Jung In-Sik
Lee Sung-Man
Meyertons Eric B.
Meyertons Hood Kivlin Kowert & Goetzel P.C.
Samsung General Chemicals Co. Ltd.
Szekely Peter
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