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
1996-10-04
1998-02-17
Marquis, Melvyn
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...
524417, 524418, 524423, 524425, 524430, 524432, 524433, 524437, 524457, 524493, 524731, 524847, C08K 554
Patent
active
057192200
DESCRIPTION:
BRIEF SUMMARY
This invention relates to moulded composites formed from highly filled curable compositions.
Moulded composites formed from highly filled curable compositions are becoming increasingly used as materials of construction, particularly for kitchen sinks, kitchen surfaces and sanitary ware, because of their attractive appearance and hard wearing properties.
Fluid, curable compositions containing high volumes of finely divided fillers suitable for forming such composites have been described in British Patent No. 1 493 393. This specification describes fluid, curable compositions wherein high volumes of filler of specified particle size are dispersed in a curable material using polymeric dispersants. The use of polymeric dispersants enable compositions to be obtained containing high volumes of finely divided fillers, for example 50% by volume, which have a remarkably low viscosity enabling the compositions to be readily handled for example by pumping. This low viscosity, in turn, enables the compositions to be sold as fluid dispersions which can be readily transported to fabricators who can mould articles in inexpensive low pressure moulds. Although some sedimentation will inevitably occur on storage, the polymeric dispersant maintains the filler particles in a state of stable, deflocculation so that the sediment can be readily redispersed by mild agitation to give a dispersion in which the filler particles are substantially uniformly dispersed and will remain so whilst the composition is converted from a fluid dispersion to a fully cured composite. The presence of the polymeric dispersant, and its function of keeping the particles in a state of stable deflocculation, not only enables a low viscosity, redispersible dispersion to be obtained, but ensures that compatibility of the components is maintained as the composition is cured so that a cured product free from cracks and flaws is obtained.
It is also possible to fabricate moulded composites from other highly filled curable compositions which have a viscosity too high to be of practical value as transportable, low viscosity, redispersible compositions. Nevertheless, these compositions are useful where the fabrication operation is carried out at the same location as the composition is prepared and where storage and redispersion are not a problem. These compositions must also contain fillers which are properly dispersed within the curable composition to avoid problems of flocculation and cracking on polymerisation.
Although moulded composites are widely used in the applications described above they often suffer from minor scratching which renders them unduly susceptible to staining from liquids such as coffee and tea. Furthermore, a small proportion of moulded composites fail prematurely in service, when subjected to thermal cycling such as experienced by a kitchen sink subjected successively to very hot and cold water.
Certain polymeric materials have now been identified which when incorporated into a curable composition can imbue a moulded composite formed from the curable composition with an improved resistance to minor scratching and thermal resilience, i.e. an improved performance in respect of the damage tolerance thermal shock test and often in respect of the thermal shock test, both of which are hereinafter described.
The polymeric materials identified for use in the present invention are known as poly dimethylsiloxanes and have hitherto been used as coating agents in paints, enamels and varnishes. However, there is no disclosure of such polymeric materials being used as additives in curable compositions.
According to a first aspect of the present invention there is provided highly filled, curable composition comprising polymer: having a weight average particle size of less than 50 microns but not having a BET surface area of more than 30 m.sup.2 .multidot.cm.sup.-3 ;
In a second aspect the present invention provides a moulded composite article formed from a highly filled, curable composition comprising polymer; having a weight average particle size of
REFERENCES:
patent: 4468491 (1984-08-01), Steinberger et al.
patent: 5189102 (1993-02-01), Tsubuko et al.
patent: 5519081 (1996-05-01), Ashton et al.
Imperial Chemical Industries plc
Marquis Melvyn
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