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
1999-09-02
2001-06-12
Wu, David W. (Department: 1713)
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...
C524S413000, C524S436000, C524S437000, C524S567000, C524S555000, C524S569000
Reexamination Certificate
active
06245846
ABSTRACT:
This invention relates to polymer formulations containing fire-resistant additives.
In a paper entitled “PVC Cable Sheathing with Improved Smoke Characteristics” presented at FR'96 London and published by Interscience (ISBN 095163286), Mandy J Herbert has described a PVC formulation containing 30 phr (parts by weight per hundred parts by weight of resin) of a phosphate plasticiser; 20 phr of a brominated aromatic ester; 30 phr of aluminum trihydroxide; 7 phr of a stabiliser; 1 phr of process aid; and 10 phr of a flame retardant additive consisting of equal proportions by weight of antimony trioxide and zinc stannate with or without ammonium octamolybdate. This was a heavily loaded formulation designed specifically for use as sheathing for optic fibers and electric wires and cables. Particularly in the presence of ammonium octamolybdate, the antimony trioxide and zinc stannate were shown to act synergistically.
Many different polymer formulations contain halogen, in the polymer itself as in the case of PVC and/or in a halogenated plasticiser or other additive. In these formulations it is well known that antimony compounds have valuable flame retardant properties. However there is a reluctance to use antimony compounds in polymer formulations for general use, because of the supposed toxicity either of the antimony or of possible impurities such as arsenic. Antimony compounds often have a deleterious effect on the smoke performance of polymer systems. There is a need for smoke suppressant additives, for use in a wide range of polymer formulations containing halogen, which contain only low levels of antimony compounds. This invention seeks to make use of the synergistic effect disclosed in a restricted context in the above-mentioned paper, to meet that need.
The invention provides a formulation comprising at least one polymer and at least one additive, halogen being present in the polymer and/or the additive, wherein there is present from 2 to 10 parts by weight, per hundred parts by weight of the polymer, of a mixture of 90-10 wt % of an antimony compound and 10-90 wt % of a divalent metal stannate or hydroxystannate, provided that the formulation contains not more than 1.5 wt % of the antimony compound.
The formulation may be solid or semi solid having plastic or to elastic properties, e.g. thermosetting or thermoplastic, before or after curing; or may be liquid as in a paint; or may be in comminuted form as in a powder paint; or may be a shaped or moulded product or cured coating film.
The polymer may be an organic polymer for example polyolefine, polystyrene, polyester, polyamide, acrylic, epoxy, phenolic, or preferably polyvinylchloride (PVC).
The formulation may contain known additives in known concentrations, for example pigments, plasticisers, flame-retardants, smoke-suppressants, fillers, stabilisers, process aids, antioxidants, etc. If the polymer itself does not contain halogen (generally chlorine or bromine) then at least one additive contains halogen. This may be for example a chlorinated or brominated plasticiser.
Among these additives may be mentioned flame-retardants and smoke-suppressants including phosphate plasticisers, chlorinated and brominated aromatic esters, aluminum trihydroxide, hydroxides and carbonates and intermediate compounds (basic carbonates or hydroxy-carbonates) of divalent metals such as magnesium and calcium, and molybdenum compounds such as ammonium octamolybdate. Preferably the formulation contains at least 20 phr e.g. 30-120 phr of aluminum trihydroxide. Preferably the formulation contains at least 5 phr, e.g. 10-40 phr of a halogenated plasticiser.
As noted, the formulation contains 2-10 phr of a mixture of an antimony compound and a divalent metal stannate or hydroxy stannate.
Preferably the antimony compound is antimony trioxide or antimony pentoxide, present in an amount of not more than 1.5 wt %, and preferably less than 1.0 wt % of the whole formulation. Preferably the divalent metal stannate or hydroxy stannate is calcium, strontium, barium, magnesium, or particularly zinc stannate or hydroxy stannate. The divalent metal stannate or hydroxy stannate may optionally contain halide (e.g. chloride or bromide) and/or amine (e.g. ammonia or alkylamine) values.
A preferred formulation consists essentially of PVC with 20-100 phr of at least one plasticiser including at least 10 phr of a chlorinated plasticiser, from 30-120 phr of aluminum trihydroxide, a stabiliser present in a functional concentration, and 2-10 phr of a mixture of 90-10 wt % of antimony trioxide and 10-90 wt % of zinc stannate or hydroxy stannate.
These formulations have use in very many areas, wherever polymer formulations need to have flame-retardant and particularly smoke suppressant properties. Preferred formulations based on PVC are suitable for use in electrical installations equipment and sheathing.
REFERENCES:
patent: 5358991 (1994-10-01), O'Brien
patent: 5681879 (1997-10-01), Yamamoto et al.
patent: 5736605 (1998-04-01), Oshima
patent: 8193136 (1996-07-01), None
World Patent Index, Accession No. 96-397275, XP 002060012, Abstract corresponding to Japanese Patent No. 8193136, published Jul. 30, 1996.
Daniels Clare
Herbert Mandy Jayne
Rai Michael
Alcan International Limited
Cooper & Dunham LLP
Egwim Kelechi
Wu David W.
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