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...
Patent
1998-03-19
2000-11-21
Wu, David W.
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...
524401, 524435, 524436, 252609, 252610, 423 92, 423274, 427212, C09K 2102, C09C 306, B05D 500, C01G 1902
Patent
active
061504475
DESCRIPTION:
BRIEF SUMMARY
The present invention is concerned with the preparation of fire retardant materials, polymer compositions containing such fire retardant materials, and novel fire retardant materials which may be produced by the process of the invention.
It is known to use tin compounds as non-toxic flame retardants and smoke suppressants for organic polymers. For example, tin compounds such as zinc hydroxystannate (ZHS), zinc stannate (ZS) and tin (IV) oxide (SnO.sub.2) have been shown to have good flame-retardant/smoke-suppressant properties in halogen-containing polymer formulations such as PVC, neoprene and hypalon, and also in other plastics materials, such as polyester resins, epoxy resins and nylons, to which halogen compounds have been added-as flame-retardant additives. The non-toxic nature of the inorganic tin compounds, combined with their dual flame-retardant/smoke-suppressant activity, has generated interest in their use as alternatives to antimony trioxide in halogen-containing polymers.
Many relatively low cost inorganic compounds are added, at relatively high levels, into polymer compositions. In some cases these are added to extend the polymer (and to lower its overall volume cost) or to modify its physical properties. Examples of such inorganic compounds include calcium carbonate (CaCO.sub.3) and silica (SiO.sub.2). In addition, some other inorganic materials are added as active flame-retardant fillers so that their endothermic dehydration during combustion of the associated polymer withdraws heat from the system and the water vapour which is released serves to smother flame. Examples of these "active" fillers include aluminium hydroxide (usually employed in the form of alumina trihydrate (ATH)] and magnesium hydroxide [(Mg(OH).sub.2 ]. It has been proposed to incorporate tin compounds and such "active" fillers into polymeric systems (both halogen-containing and halogen-free) to serve as fire-retardant combinations.
It has been found that the use of filler powders comprising a particulate inorganic filler material, the particles of which are coated with a layer of a tin compound, gives improved fire-retardancy effects as compared with the use of comparable simple mixtures of the two components (filler and tin compound).
EP-A-0156196 discloses fire-retardant materials comprising particulate fillers coated with a layer of tin oxide. These fillers were prepared using aqueous acidic solutions of stannic chloride and these are not appropriate for treating many inorganic fillers, for example magnesium hydroxide or calcium carbonate, which are acid-soluble.
It has now been found, in accordance with the present invention, that it is possible to coat inorganic particulate substrates with tin compounds using, as starting materials, an alkaline coating solution comprising an alkali metal hydroxystannate, (e.g. sodium hydroxystannate or potassium hydroxystannate). Accordingly inorganic fillers such as ATH, Mg(OH).sub.2 or CaCO.sub.3 may be coated using such a process. This process is, of course, also appropriate for coating tin compounds onto acid-insoluble substrates such as TiO.sub.2 etc.
According to the present invention there is provided a process for the preparation of a fire-retardant material which comprises a particulate inorganic filler (other than a tin compound) coated with a layer of tin oxide or divalent metal hydroxystannate or a divalent metal stannate, which process comprises the steps of: solution of an alkali hydroxystannate, optionally also containing a divalent metal oxide dissolved therein; water-soluble source of a divalent metal, to form a layer of tin oxide or of a divalent metal hydroxystannate on the surface of the filler; and (ii) in order to convert it to the corresponding divalent metal stannate.
The invention also provides a polymer composition comprising a polymer and a fire retardant material produced by the process as defined above. Suitably, the particulate inorganic fire retardant material will be present in the polymer composition in an amount of from 5 to 400% by weight, based on
REFERENCES:
patent: 4146669 (1979-03-01), Dikler
patent: 5093199 (1992-03-01), Staendeke et al.
Flame Retardant Polymeric Materials, edited by M. Lewin, S.M. Atlas and E.M. Pearce, Plenum Press, New York 1975, pp. 82-84.
The Industrial Uses of Tin Chemicals, S.J. Blunden, P.A. Cusack and R. Hill, Royal Society of Chemistry, 1985 pp. 180 and 182.
Derwent Publications Ltd., London, GB; AN 88-094943; XP002013603 & JP,A,63 045 123 (Ishihara Sangyo Kaisha) Feb. 26, 1988.
Derwent Publications Ltd., London, GB; AN 87-104169; XP002013604 & JP,A,62 050 344 (Sumitomo Bakelite KK, Seiko Kasei KK) Mar. 5 1987.
Baggaley Rupert Guy
Cusack Paul Andrew
Heer Manider Singh
Patel Bhagwati
Egwim Kelechi C.
ITRI Limited
Wu David W.
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