Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – Processes of preparing a desired or intentional composition...
Reexamination Certificate
2000-09-18
2003-12-16
Cain, Edward J. (Department: 1714)
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
Processes of preparing a desired or intentional composition...
C523S219000
Reexamination Certificate
active
06664314
ABSTRACT:
The invention relates to a moulding composition for the production of sanitary-ware components having more than one visible side, and to sanitary-ware components which are produced from these moulding compositions.
Typical moulding compositions for the production of sanitary-ware components, including kitchen sinks and the like, are moulding compositions which comprise a methyl-methacrylate-based syrup and an inorganic filler, as described for example in German Patent DE-24 49 656, European Patent Application EP 0 361 101 and also WO 95/23825.
These moulding compositions are very suitable for the production of shaped components on which there is only one so-called visible side, and on which the opposite side of the shaped component from the visible side can no longer be seen after the shaped component has been installed. The appearance of the opposite side of the shaped component from the visible side is therefore unimportant to the saleability of the product, and need not therefore, in particular, follow defined contours or have a smooth surface.
Shaped components, in particular, which have been produced from acrylate moulding compositions, shrink very significantly on reacting. The dispersions used to produce the shaped components often contain about 30 to 40 wt. % of methyl methacrylate monomer, which shrinks by about 24 vol. % on polymerization. Calculated in terms of the methyl-methacrylate-based dispersions, this leads to about 10 vol. % shrinkage of the dispersions or moulding compositions. Since this shrinkage needs to be compensated for at least to a large extent, in order to obtain marketable products, it is necessary to take the shrinkage effect into account using an elaborate tool design with “floating” tool halves, which are pressed together by pneumatic or hydraulic pressure (cf. e.g. EP 0 019 867 A1).
At the same time, elaborate temperature programmes are required during the polymerization process. For example, the visible or good side of the shaped component first needs to be heated, while the reverse side still needs to be kept cool initially, to ensure that the polymerization does not set in there until later. Only after about 10 min can the polymerization temperature of about 100° C. be applied there as well.
Although a visually attractive used side or visible side of the shaped component can be obtained by these elaborate measures, especially by the differential temperature application, it is nevertheless only possible to produce shaped components which have just one such visible or good side. In the case of kitchen sinks, for example, it has been possible to use these methods and shaped components only because the sink has hitherto been installed in the supporting kitchen cupboard in such a way that the reverse side is concealed by the furniture parts.
As for moulding composition formulations, as disclosed for example by EP 0 361 101 A1, which uses very coarse-grained fillers, the shrinkage compensated for by the moulding tool, despite special tool designs, leads to very rough surfaces, since, between the coarse filler grains which remain at the surface, the polymer matrix detaches to a considerable degree from the tool surface and forms microscopic indentations in the visible-side surface. This increased roughness leads to the accumulation of dirt particles during use. At the same time, it is more difficult to remove dirt particles again from the surface once they have adhered. Because of the roughness, which is naturally likewise relatively great, on the reverse sides, it is difficult to carry out cleaning here as well. Owing to the large number of indentations, dust particles are retained by the reverse side, opposite the visible side, and cause increased susceptibility to soiling.
The object of the present invention is to provide a moulding composition which makes it possible to form shaped components having not only one but two or more visible sides.
This object is achieved according to the invention in that the moulding composition, which comprises a methyl-methacrylate-based syrup and up to 85 wt. % of an inorganic filler, furthermore comprises compressible propellant-filled hollow microspheres having a plastic wall which is essentially insoluble in MMA, the proportion by volume of the hollow microspheres to the total volume of the moulding composition being in the 5 to 50 vol. % range
With the moulding composition according to the invention, it is possible to produce shaped components in which the surface roughness of the reverse side corresponds approximately to that of the visible side. The moulding compositions hence open up further possible applications in addition to the shaped components hitherto produced therefrom.
Shaped components (e.g. kitchen sinks) produced conventionally from moulding compositions can be used in a novel way, i.e. the kitchen sinks may for example be installed in a work surface in such a way that their reverse side may also remain visible.
A further advantage is that the visible side is easy to clean, even in cases in which relatively coarse-grained fillers have been used. This is true even in the case of shaped components made from materials whose coarse-grained filler is in the range of from about 100 &mgr;m to more than 1000 or even 3000 &mgr;m.
While, in the case of conventional formulations, the filler content brought about a reduction in the shrinkage effect in addition to improving the functional properties, the filler content was also important in terms of reducing the volume of monomer, since naturally the shrinkage effect was commensurately less when the proportion of syrup in the moulding composition was lower. It was possible to achieve a further reduction of the shrinkage effect by using MMA prepolymers (so-called polymethyl methacrylate, abbreviated to PMMA), which was likewise capable of bringing about a decrease of the shrinkage effect. PMMA can nevertheless only be used to a certain degree since it significantly increases the viscosity of the syrup.
According to the present invention, however, the proportion of filler can be tailored just to the desired obtaining of the functional properties of the shaped component, and need no longer take the shrinkage effect into account.
Consequently, moulding compositions having a filler content of less than 20 wt. % are also readily possible.
The preferred proportion by volume of the hollow microspheres is in the range of from 8 to 45 vol. % of the moulding composition.
The particle size of the hollow microspheres is not subject to any particular restrictions, although the particle size should be smaller that 500 &mgr;m, so as to ensure that, in cases in which the hollow microspheres come to lie at the surface, when there is stress on the surface these cannot be damaged and then lead to indentations in the surface of the shaped component.
It has already been mentioned that PMMA can be used as a modifying agent for the syrup, especially with a view to reducing the shrinkage effect, but also with a view to moderating moulding-composition viscosities.
For the latter reason, the addition of PMMA to the syrup may also be indicated according to the invention, in which case PMMA having a molecular weight (M
W
) of 50,000 to 250,000 is employed here, as in the prior art, and may be present in the syrup in an amount of up to 20 wt. %, expressed in terms of the mass of the syrup.
The hollow microspheres are preferably thermoplastic hollow spheres having elastic properties, which are produced by an expansion process.
For example, the hollow microspheres disclosed by EP 0 559 254 A1 have proved suitable, although these can only be used in the expanded state. Experiments with non-expanded hollow microspheres of this type show that the production of shaped components having more than one visible layer is not then possible.
Although non-expanded hollow spheres have already been described in connection with compensating for shrinkage effects, it has unexpectedly been found, as mentioned above, that only already expanded hollow microspheres show the desired effect in the MMA dispe
Hajek Andreas
Harke Stefan
Wilhelm Thomas
Blanco GmbH & Co KG
Cain Edward J.
LandOfFree
Moulding compositions for the production of sanitary-ware... does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Moulding compositions for the production of sanitary-ware..., we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Moulding compositions for the production of sanitary-ware... will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-3116932