Stock material or miscellaneous articles – Hollow or container type article – Polymer or resin containing
Reexamination Certificate
2001-10-01
2004-04-27
Nolan, Sandra M. (Department: 1772)
Stock material or miscellaneous articles
Hollow or container type article
Polymer or resin containing
C428S520000
Reexamination Certificate
active
06726970
ABSTRACT:
The present invention relates to thermoplastically mouldable, self-reinforced sheets made from poly(meth)acrylate, processes for producing poly(meth)acrylate sheets of this type, and sanitary items, such as bathtubs, shower trays or washbasins, which may be produced from these semifinished sheets.
The present invention relates in particular to self-reinforced, thermoplastically mouldable sheets made from poly(meth)acrylate and having at least two layers which differ in their filler content, where the filler content is the percentage proportion by weight of the reinforcing fillers, based on the total weight of the respective layer.
These polyacrylate sheets serve in particular for the production of sanitary items, such as bathtubs, shower trays or sink basins.
In principle, sanitary items are manufactured by a multistage production process having at least four stages. Acrylic sheeting is first produced, and this is then thermoformed. Since the moulding has insufficient mechanical strength, a reinforcement layer has to be applied, by spraying a glass fibre/styrene mixture onto the reverse side of the moulding. A sheet of timber is often inserted to reinforce the base region here, and this, too, is secured by spray-application of resin material comprising glass fibre.
After reinforcement, protruding glass fibres are rolled into the backing. After these operations, the resultant sanitary item has to be annealed in order to polymerize the reinforcement layer.
Disadvantages of this process are the various manpower-intensive operations and the undesirable emissions of solvent during any type of backing-application process, and also the handling of glass fibre, which is a major risk per se. Finally, the processing of various plastic components and of the mixture of materials comprising reinforcing materials and plastics gives the sanitary items poor recyclability.
The process of WO 98/45375=PCT/EP98/01881 makes some progress in avoiding the disadvantages referred to. According to this publication, the reinforcement layer is composed of a cold-curing (meth)acrylate resin which has a content of from 1 to 75 percent by weight of fine fillers with particle size not above 100 &mgr;m. This permits a sanitary item which is completely recyclable and nevertheless complies with the mechanical properties required to be provided without use of any fibrous fillers, such as asbestos or chopped glass fibre. However, the application of the reinforcement layer by a spraying process is not entirely without problems, at least from the point of view of employee safety, particularly since there is a health risk to operators.
WO 97/46625=PCT/GB97/01523 (ICI) proposes reducing the risk to manpower and operators by using aqueous redox systems to cure the spray-applied (meth)acrylate system. Although this reduces the adverse effects of solvents (ethyl methyl ketone, other ketones and organic solvents and the like) during the spraying procedure this reduction is only slight, since the amount of curing agent to be used is vanishingly small in comparison with the binder component. Indeed, spraying itself is an operation not entirely free from risk. Mention should be made, for example, of the very fine dispersion, unavoidable during spraying, of comparatively volatile polymerizable constituents of the (meth)acrylate resin. The MAC values for MMA and other monomers are in fact relatively low and are much more rapidly achieved during spraying than, for example, during processing by other methods. It would be particularly desirable to be able to dispense with the subsequent spraying-on or application of a reinforcement layer.
In view of the prior art mentioned and discussed herein, an object of the invention was to provide sheets (semifinished products in the form of a sheet) made from poly(meth)acrylate, from which the sanitary items described in some detail above can be produced at the lowest possible production cost.
The provision of fully recyclable reinforced sheets made from poly(meth)acrylate (“acrylic sheeting”) was likewise an object of the invention.
Another object was that the process for producing the semifinished sheet product, and also for producing the sanitary items, was to be attended by the lowest possible level of emissions (solvents, volatile and hazardous substances, such as monomers and the like).
The semifinished product should, furthermore, be capable of being produced and processed by conventional current industrial production processes.
A still further object of the invention is the provision of completely recyclable mouldings, preferably shower trays or washbasins, which are fully recyclable, as far as possible without any risk to operators, in particular using the depolymerization method known for acrylic sheeting, by means of metal baths.
Another object of the invention is to provide a semifinished product in the form of a sheet, the sanitary items produced from which, preferably shower trays or washbasins, meet the general requirements placed on the stability of sanitary items of precisely this type, while giving the highest possible materials-related savings.
The formation of cracks in the sanitary item, a particular risk during high-performance shaping of poly(meth)acrylate sheets (semifinished products), should also be suppressed to the greatest possible extent.
A still further object is the provision of a semifinished product in the form of a poly(meth)acrylate sheet with the best possible impact strength.
In addition, both the novel semifinished product and the novel sanitary item (moulding) which can be produced from the same are to be as simple as possible to manufacture.
The extent of downstream manual operations is moreover to be reduced to a minimum.
Finally, automation of the process for producing the mouldings from (self)reinforced poly(meth)acrylate sheets to the highest possible degree, and in a simple manner plays a not insignificant part.
Another point of particular interest is the provision of a sanitary item made from reinforced poly(meth)acrylate sheets which have high and/or improved values for one or a number a number, or all, of such mechanical parameters as abrasion resistance, flexural strength (measured on the inner side (upper side) of the moulded acrylic sheeting), flexural strength (measured on the reverse side (lower side)), modulus of elasticity, impact strength (measured on the inner or upper side of the moulded acrylic sheeting), impact strength (measured on the reverse side (corresponding to “coated side” in the prior art)).
A self-reinforced, thermoplastically mouldable poly(meth)acrylate sheet with all of the features of claim 1 achieves these objects together with other objects which can readily be inferred from the discussion of the prior art in the introduction or else rendered self-evident by the same, although they have not been specified in detail.
Advantageous embodiments of the semifinished product of the invention are provided by the claims dependent on the independent product claim.
With regard to a process, the features of the independent process claim solve the process aspects of the problem on which the invention is based. Advantageous versions of the process are protected by the process claims dependent on the independent process claim.
With respect to the sanitary item, the appropriate claim supplies the solution for this aspect of the problem on which the application is based, and advantageous embodiments are the subject-matter of the claims dependent on this product claim.
A sheet made from poly(meth)acrylate and having at least two layers which differ in their filler content, where the ratio between the elongation at break of the layer with higher filler content and the elongation at break of the layer with lower filler content is less than 1.5, can provide a poly(meth)acrylate sheet from which, for example by heat-assisted moulding processes known per se, sanitary items can be produced which give excellent compliance with all of the requirements placed by standards institutes and industrial processors on the physical p
Molnar Gerald
Schoela Egbert
Schwenninger Robert
Nolan Sandra M.
Oblon & Spivak, McClelland, Maier & Neustadt P.C.
Roehm GmbH & Co. KG
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