Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – From silicon reactant having at least one...
Reexamination Certificate
2001-06-15
2004-04-06
Sanders, Kriellion A. (Department: 1714)
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
From silicon reactant having at least one...
C525S101000, C525S389000
Reexamination Certificate
active
06716952
ABSTRACT:
TECHNICAL FIELD
The present invention relates to a novel flame retardant which is substantially free of such atoms as halogen, phosphorus and nitrogen and yet exhibits high level flame retardant properties and to a highly flame-retardant resin composition formulated using the above flame retardant without employing bromine-, chlorine-, phosphorus- or like containing compounds.
BACKGROUND ART
Resins to be utilized industrially, for example in the electric and electronic fields, are often required to have high-level flame retardant properties qualifying them under UL-94 V-0 (U.S. Underwriters Laboratories standard) so that the safety from fire can be secured. Therefore, various flame retardants have been developed. In recent years, many investigations have been made on the use of halogen-free flame retardants, such as silicone-based flame retardants, reflecting the mounting interest in environmental problems, especially in Europe.
As for the resin compositions containing a silicone-based flame retardant, Japanese Kokoku Publication Sho-62-60421 discloses a resin composition comprising a thermoplastic non-silicone polymer and a polysiloxane resin containing not less than 80% by weight of T units represented by the formula SiO
3/2
(according to the description, it being preferred for rendering the polymer composition flame-retardant that the polysiloxane resin have a molecular weight of not less than 2,000 but not more than 6,000 and the phenyl group content be not more than 80%, with the methyl group content accounting for the balance). Further, Japanese Kokai Publication Hei-10-139964 discloses a flame-retardant resin composition comprising an aromatic ring-containing non-silicone resin and a silicone resin having units represented by the formula SiO
2/2
and units represented by the formula SiO
3/2
(with a weight average molecular weight of not less than 10,000 to not more than 270,000) incorporated therein. On the other hand, Japanese Kokai Publication Hei-10-316868 discloses a flame-retardant additive for aromatic-base polymers which comprises an aryl-containing silicone compound and a diorganopolysiloxane compound.
However, the prior art silicone-based flame retardants are low in flame retardant effect. Thus, when added to specific resins such as aromatic polycarbonate resins, they bring about a certain degree of flame retardance but, when added to resins other than aromatic polycarbonate resins, they produce little fire retardant effect, hence they are not suited for general use in resins. Additionally, they are relatively expensive, hence cannot be used in resins for general use for economical reasons.
In view of the current state of art as mentioned above, it is an object of the invention to provide a flame retardant which is inexpensive, has a high level flame retardant effect and is substantially free of such atoms as halogen, phosphorus and nitrogen, as well as a flame-retardant resin composition rendered flame-retardant using the same.
DISCLOSURE OF THE INVENTION
The present invention is concerned with a flame retardant which comprises a polymer comprising silicon, boron and oxygen, having a skeleton substantially formed by a silicon-oxygen bond and a boron-oxygen bond and having an aromatic ring within the molecule.
In another aspect, the invention is concerned with a flame-retardant resin composition comprising 100 parts by weight of a resin and 0.1 to 50 parts by-weight of the above flame retardant.
In the following, the invention is described in detail.
The flame retardant of the invention comprises a polymer comprising silicon, boron and oxygen and having a skeleton substantially formed by a silicon-oxygen bond and a boron-oxygen bond. Thus, a silicon-oxygen bond and a boron-oxygen bond account for not less than 80%, preferably not less than 90%, of the bonds forming the skeleton of the above polymer, and the polymer may additionally contain a silicon-silicon bond, a boron-boron bond, an oxygen-oxygen bond, a silicon-bivalent organic group bond, a boron-bivalent organic group bond and the like. In referring to the term “skeleton” as used in the present specification, the silicon- or boron-univalent organic group bonds are not taken into consideration, namely they are regarded as bonds other than the skeleton-constituting bonds.
Preferably, the above polymer has a skeleton resulting from connection of a silicon atom or a boron atom with another silicon atom and/or boron atom via an oxygen atom. In that case, the skeleton of the polymer substantially comprises Si—O—Si, Si—O—B, and B—O—B bonds. Thus, the skeleton of the above polymer may comprise Si—O—B bonds alone or may substantially comprise Si—O—B bonds and contain a slight proportion of Si—O—Si bonds and/or B—O—B bonds. The skeleton may also contain Si—O—Si, Si—O—B and B—O—B bonds at random. Further, the skeleton may substantially comprise Si—O—Si and B—O—B bonds and contain a slight proportion of Si—O—B bonds. In this case, the above polymer has a skeleton such that the molecule may be divided into a portion practically comprising silicon alone and a portion practically comprising boron alone. The skeleton of the polymer mentioned above may be a linear one or a three-dimensionally crosslinking one. From the flame retardancy viewpoint, however, the three-dimensionally crosslinking structure is preferred.
The polymer in the flame retardant of the invention (hereinafter also referred to as “flame retardant polymer”) has an organic group(s) within the molecule. The term “organic group” as used herein means a uni- or polyvalent substituent composed of a carbon atom(s) together with any of a hydrogen atom, an oxygen atom, a nitrogen atom, a sulfur atom, a phosphorus atom, a halogen atom and like atoms. Typically, it is a hydrocarbon group, preferably containing 1 to 20 carbon atoms.
The flame retardant polymer of the invention more preferably has an aromatic ring among organic groups. This aromatic ring may be uni-, bi- or trivalent, for instance, but is preferably a univalent one in view of the ease of synthesis. The mode of bonding of the aromatic group within the molecule is arbitrary and, thus, the group may be bonded to a silicon atom and/or boron atom directly or bonded to a silicon atom and/or boron atom via a bivalent organic group such as a methylene or ethylene group (namely, the aromatic ring may be contained in the form of an aralkyl group such as benzyl group or phenylethyl group), for instance. For more improved flame retardancy, the aromatic ring within the molecule is preferably one directly bonded to a silicon atom. There is no particular restriction as to the method of introducing the aromatic ring into the molecule.
The term “aromatic ring” is used herein as a generic term for rings belonging to aromatics, without any particular restriction. As preferred aromatic rings, there may be mentioned phenyl, cresyl, xylenyl, naphthyl and anthracenyl. More preferred are univalent benzene- or condensed benzene-derived aromatic groups containing 6 to 20 carbon atoms, more preferably 6 to 10 carbon atoms. Further, the aromatic ring may be substituted by one or more of halogen, oxygen, nitrogen and other elements.
The flame retardant polymer of the invention may further have an organic group not containing the above-mentioned aromatic ring. The aromatic ring-free organic group may be uni-, bi- or trivalent, for instance. For reasons of ease of synthesis, a univalent one is preferred. As the aromatic ring-free organic group, there may be mentioned univalent straight or cyclic alkyl groups and, among them, ones containing 1 to 12 carbon atoms are suitable. For attaining better flame retardancy, alkyl groups containing a smaller number of carbon atoms, specifically 1 to 4 carbon atoms. A particularly preferred alkyl group is methyl group.
The proportion of the aromatic ring-containing organic group(s) in the total of the organic groups is not particularly restricted but, for obtaining better flame retardancy, it is preferred that the aromatic ring-containing organic group(s) account for not less than 10 mol %,
Matsumoto Kazuaki
Ono Yoshitaka
Tsuneishi Hiroshi
Kaneka Corporation
Sanders Kriellion A.
Westerman Hattori Daniels & Adrian LLP
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