Stock material or miscellaneous articles – Composite – Of addition polymer from unsaturated monomers
Reexamination Certificate
2000-01-14
2003-09-02
Thibodeau, Paul (Department: 1773)
Stock material or miscellaneous articles
Composite
Of addition polymer from unsaturated monomers
C428S034100, C428S215000, C428S327000, C428S334000, C428S515000, C428S520000
Reexamination Certificate
active
06613444
ABSTRACT:
The invention relates to backing-lined sanitary articles according to the precharacterizing clause of claim
1
and to a process for the production of such sanitary articles.
In particular, the invention relates to bathtubs or shower trays or sinks, which have a preferably thermoformed acrylic glass moulding reinforced on its reverse with 1.5 to 10 mm thick polymer material, which is glass fibre- and asbestos-free and is bonded firmly to the acrylic glass moulding without additional adhesion promoters, this reinforcement being obtainable by polymerization of a (meth)acrylate system.
The following publications are mentioned for the closer prior art:
D1=Patent Abstracts of Japan, unexamined applications, section M, volume 17, no.694, Dec. 17, 1993, The Patent Office Japanese Government page 45 M 1531; & JP-A-05 237 854;
D2=DE 36 44 111 A1;
D3=FR 2 640 909;
D4=EP-A-0 693 503;
D5=EP-A-0 285 046;
D6=EP-A-0 345 581;
Reinforced acrylic glass mouldings as baths or basins in the sanitary sector are known in principle. Thus, Japanese Laid-Open Specification JP-A 05-237854 of Mitsubishi Rayon (=D1) describes a production process in which a filler-containing containing resin mixture is introduced into a gap between the mould and thermoformed acrylic glass moulding and then cured integrally in contact with the moulding. A mixture of 90 parts by wt. of a prepolymer of a methacrylic ester and 10 parts by wt. of a methacrylate monomer with 60 wt. % aluminium hydroxide, for example, is used as the filler-containing resin mixture. This mixture is poured, together with-initiator and crosslinking agent, into a gap 8 mm thick between the preformed acrylic glass component and the mould. The mixture in the gap can then be cured for 4 h, the surface of the gap between the mould and the moulding being covered with a polyester film.
Fillers which are proposed for the resin mixture to be poured in are, in addition to aluminium hydroxide, furthermore calcium carbonate, glass fibres or carbon fibres.
Although laminated composite bodies, in particular bathtubs or shower trays or also sinks, which have entirely satisfactory properties in respect of the adhesion of the reinforcing layer to the thermoformed acrylic glass moulding of the base and in respect of the strength of the entire composite body are obtainable by the casting process proposed in the Japanese Laid-Open Specification D1 referred to, both the moulding and the process for its production have particular disadvantages in at least two respects.
On the one hand, for production of the backing-lined moulding, a second mould in which the volume required for casting the reinforcing composition must also be taken into account is always necessary.
On the other hand, only a relatively thick backing lining of the thermoformed moulding (8 mm in the abovementioned example) is possible, since relatively large differences in thickness can easily occur in a casting process, and these can no longer be tolerated at backing lining thicknesses which are too low, such as would be entirely desirable on the basis of consumption of material and saving weight.
D2 (=DE 36 44 111 A1) discloses a process for the production of a bathtub reinforced with plastic, in which a tub which has been produced from acrylic glass by the thermoforming process is reinforced with a glass fibre-reinforced polyester resin layer sprayed onto the outside. However, both the fibre reinforcement and the backing lining with polyester material are unsuitable for simple and substantially complete recyclability of used mouldings, and indeed render this almost impossible.
FR 2 640 909 (=D3 ) relates to a sandwich structural component for the sanitary sector of thermoplastic resin (e.g. PMMA), and a glass fibre mat preformed on the structural component mould of the thermoplastic resin component. These components are bonded in a mould by injecting in a syrupy polyester formulation between the preformed acrylic and fibre components. The possibility of using an acrylic resin is also mentioned. As in D2, the use of glass fibres, whether in the form of mat or of a chopped roving, is to be regarded as prohibitive for reprocessing of used mouldings. Furthermore, the process suggested by D3 is under no circumstances a spray process, but rather an injection (squirting) process, which requires just as much outlay and is just as disadvantageous as the casting process of D1. Several working steps, several people, several moulds and reworking steps are required to arrive at a product.
Reinforced sanitary articles which have a thermoformed acrylic glass moulding reinforced on its reverse with a layer of a fibre-containing polymer material which is bonded firmly to the acrylic glass moulding without additional adhesion promoters are also known from EP-A-0 693 503 (=D4).
These backing-lined sanitary articles are characterized in that the reinforcing layer is 1 to 5 mm thick and is obtainable by curing a polymerizable, cold-curing, reactive (meth)acrylate system sprayed on to the reverse of the acrylic glass moulding. The (meth)acrylate system here comprises, as essential constituents, in addition to the polymerizable constituents, a redox system, fine fillers and, for reinforcement, 10-50 per cent by weight of chopped glass fibres.
One advantage of the known backing-lined sanitary article is said to be that its reprocessing by depolymerization—provided that the fine fillers are accordingly suitably chosen—is said to be possible without problems. Although this applies without limitation in respect of the fine fillers which can be seen from D4, the chopped glass fibres required in large quantities for the reinforcement are not unproblematic in the depolymerization, which unfortunately has been confirmed by extensive results from practice. Although it can be assumed in theory that the chopped fibres from used components collect on the surface of the metal bath required for the depolymerization and can be skimmed off with a slide bar or doctor blade, it has been found that the chopped fibres remain in the metal bath to a degree which cannot be ignored, and cannot be readily separated off. Furthermore, the chopped glass fibres in principle are to be evaluated in the same way as asbestos fibres in respect of work safety. A health hazard to the operating personnel due to the chopped glass fibres, which are partly obtained in the form of dust during the depolymerization, cannot readily be excluded. It would accordingly a priori be highly desirable to dispense with such fibre fillers.
In addition, the (meth)acrylate systems on which the reinforcing layers from the prior art are based tend at least in some cases towards disturbances in curing, for example air inclusions etc. The chopped glass fibres essential for the reinforcement protrude, which means that after spraying on, the fibres of some centimetres length do not lie flat on the reverse of the moulding, but during development of the tangle within the reinforcing material the fibres can project from the plane of the moulding to a greater or lesser degree. Rolling for compensating the disturbances in curing and pressing on the fibre reinforcements are therefore unavoidable. This manual reworking—that is to say reworking by hand—requires outlay and makes the product more expensive.
Although the impression could be gained that the production variant disclosed in D4 could also manage without glass fibre-reinforcement, D4 documents the need for glass fibre reinforcements through all the examples. In addition, component G) according to D4 is designated an essential constituent of the reinforcing layer. However, an essential constituent cannot be simply omitted without raising doubts as to the success of the technical doctrine. This is a clear indication that the technical doctrine of D4 includes no reinforcing layers which are free from glass fibres and therefore discloses and renders accessible no corresponding solution to the expert. There is therefore still the unsolved problem of backing-lined sanitar
Debes Ralf
Jaeckel Rudiger
Ritzert Hans Josef
Schroder Axel
Seelmann Peter
Oblon & Spivak, McClelland, Maier & Neustadt P.C.
Paulraj Christopher
Roehm GmbH & Co. KG
Thibodeau Paul
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