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
1999-03-18
2003-02-25
Reddick, Judy M. (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...
C264S300000, C264S319000, C264S331180, C524S430000, C524S437000, C524S493000, C524S497000
Reexamination Certificate
active
06525122
ABSTRACT:
BACKGROUND OF THE INVENTION
The invention relates to a plastics moulding, in particular a moulded part such as a kitchen sink, a washbasin, or a work-top or similar, comprising a polymer phase formed from a curable reaction mass and a particulate filling material embedded therein, which contains a resin material filled with an inorganic filler. The invention relates in particular to mouldings with a so-called granite design.
Moulded parts and slabs with granite designs or else with plain-coloured surface are manufactured traditionally by conventional casting methods. For this all the components of a casting compound including the fillers are mixed, degassed and cast/pumped into moulds and polymerised. In the case of slabs the continuous belt casting method is also applied on a large scale. Casting compounds with a viscosity in the range from 2000 to 40000 mPas are pourable/pumpable.
In the case of acrylic (or polyester) composites with aluminium oxide trihydrate (ATH) as filler the granite effect can be obtained by curable resin-containing structures such as slabs, bars etc., being fine ground to a granule and the granule being used in turn as a decorative filling material in the polymer phase. The granule is used according to the desired design in a particle size range selected for this. Fine granite designs can be obtained with particle sizes of 50-900 &mgr;m, medium-coarse ones with 900-2500 &mgr;m and coarse ones with >2500 &mgr;m.
Since dark colour tones are frequently produced with granite designs, the reduction of the so-called water whitening is a central problem particularly with moulded parts. Due to the permanent influence of hot and cold water over long periods, a visibly unattractive brightening, the water whitening, comes about. It is already known that the water whitening can be reduced considerably by the use of fillers (for example ATH) which are coated with silanes. As a consequence, however, the mechanical and thermal properties of the moulded part material change, so that in the hot-cold cycle (cycle: 3 min hot water with 87° C.; 3 min cold water with 21° C.) the moulded parts already acquire small hair-line cracks after a few hundred cycles or even rupture completely, so that they have to be replaced.
A typical casting compound formulation consists in its main components of 40 to 55 wt % (silanized) ATH, 5 to 20 wt % granule and 30 to 40 wt % casting resin. If on the other hand unsilanized ATH is used, the crack behaviour in the hot-air cycle can certainly be rated as more positive, but on the other hand a serious brightening (water whitening) is observed on the areas of the moulded part washed by water.
SUMMARY OF THE INVENTION
The object of the invention is to propose a plastics moulding which in addition to the good resistance to water whitening possesses a high resistance to crack formation in hot-cold cycles.
This object is achieved according to the invention in the case of a plastics moulding of the kind described in the preamble by the fact that the polymer phase comprises up to 5 wt %, referred to the weight of the plastics moulding, of inorganic additive particles
that the particulate filling material is swellable in the curable reaction mass,
that the filled resin material comprises a content of inorganic filler in the range from 50 to 80 wt % with an average particle size of approx. 5 to approx. 100 &mgr;m, and
that the filling material has a particle size in the range from 60 to 8000 &mgr;m and is contained in the plastics moulding in a proportion of approx. 30 to approx. 75 wt %.
Due to the limitation of the inorganic additives in the polymer phase to not more than 5 wt % of the total weight of the moulding, the polymer phase remains substantially filler-free. The selection of the filling material according to its swellability in the reaction mass requires the abandonment of the manufacturing methods conventional to date in which the reaction mass has been pumped/poured into moulds together with the added filling material. The viscosity of the mixture of reaction mass and swollen filling material and optionally the inorganic additives attains a level such that the mixture is no longer pumpable or pourable.
Surprisingly it has been found, however, that precisely because of the swelling of the filling materials in the reaction mass a mixtures is obtainable [with which, when] it is charged into a mould half, on the closure of the mould and acting upon with a predetermined pressure, a void-free filling of the mould cavity is achievable without a destruction of the particulate structure of the filling material taking place, and the latter can exert unimpeded its decorative and/or contrasting effect on the exposed side, if this is desirable as with a granite design. A further aspect of the invention is to be seen in a plastics moulding of the kind described in the preamble in which a particulate filling material is used which is swellable in the reaction mass in such a way that a test formulation of 60 wt % of curable reaction mass and 40 wt % of the particulate filler exhibits a swelling factor ≧2.
There also forms part of the invention a process with which the plastics mouldings described above can be produced.
Such a process comprises the steps:
Production of a mixture of a curable reaction mass for the formation of a polymer phase with a particulate filling material and transfer of the mixture for curing into a mould, wherein
the curable reaction mass is used substantially free from inorganic fillers,
wherein there is used as filling material a filling material swellable in the reaction mass and containing a resin material filled with an inorganic filler,
wherein the content of the inorganic fillers in the filling material comes to 50 to 80 wt % and wherein the particles of the inorganic filler exhibit an average particle size of approx. 5 to 100 &mgr;m and the filling material; exhibits a particle size of approx. 60 to approx. 8000 &mgr;m and is so metered that it is contained in the plastics moulding in a content of approx. 30 to approx. 75 wt %,
wherein the filling material is allowed to swell in the curable reaction mass until such time as the mixture is no longer pourable,
wherein the mixture is placed for curing in one of the mould halves disposed in a press, the mould is closed and a predetermined compressive force is applied to the mould and the mixture is cured thermally in the closed mould.
The method of procedure according to the invention differs from the prior art both in the formulation and the technology.
In comparison with the conventional method of procedure the use of loose ATH in the polymer phase is abandoned substantially completely and instead of this a filling material is used which contains a resin material in the form of a polymer granule with a specified swelling behaviour and an adjusted content of an inorganic filler. There are considered as resin component all radically polymerisable casting resins, preferably however acrylic resins and polyester resins. There are suitable as fillers all mineral granular and fibrous materials, but also all synthetic granules, preferably however ATH. The filler content of the finished plastics moulding is markedly lower compared with the conventional technology at preferably approx. 40 to 50 wt %.
Due to the swelling of the filling material/polymer granules in the reaction mass for forming the polymer phase, mixtures which are no longer pumpable and which can be processed only with a special technology are obtained. The mixture consisting of reaction mass and filling material and optionally further additives is charged into the one half of the open mould and is by closing of the mould brought into the desired three-dimensional form in the mould press under corresponding pressure according to the displacement method.
Critical for the operation of the whole process according to the invention is a quite particular swelling behaviour of the filling material/polymer granules together with a particular final viscosity of the mixture.
The swelling behaviour of the polymer gr
Hieber Gunter
Knospe Daniel
Schlier Horst
Schock Friedrich
Schock Karl
Reddick Judy M.
Schock & Co. GmbH
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