Method for manufacturing a shower or bathtub made of sanitary acrylic with slip-resistant properties, shower or bathtub made of sanitary acrylic with slip-resistant properties, and method for regenerating the slip-resistant properties of a shower or bathtub made of sanitary acrylic

Abstract

Method for manufacturing a shower or bathtub made of sanitary acrylic with a surface having anti-slip properties, wherein i. a flat blank made of sanitary acrylic is provided, ii.The blank is formed into a tub of a desired shape by heating and deep drawing, wherein the surface of the blank or the tub is roughened to produce the anti-slip property, characterized in that: - the roughening of the surface takes place in a further step after the tub has been formed, and - the material of the blank contains a fine-grained additive by weight of between 0.01 and 0.5%, preferably between 0.02 and 0.2%, - wherein the fine-grained additive is calcium carbonate, in particular chalk powder, and / or magnesium carbonate and / or pyrogenic silica and / or titanium dioxide, and has a particle size distribution in which at least about 80% of the particles have a mean diameter of less than 5 µm and at least about 40% of the particles have a mean diameter of less than 1 µm.

Description

The present invention relates to a method for manufacturing a shower or bathtub made of sanitary acrylic with a non-slip property according to the preamble of claim 1, a shower or bathtub made of sanitary acrylic with a non-slip property according to the preamble of claim 7, and a method for regenerating the non-slip property of a shower or bathtub made of sanitary acrylic. For bathtubs and shower trays in both private and public areas, anti-slip coatings are increasingly being used as the sole or additional safety measure against falls, which particularly endanger children and the elderly. These coatings can be added retroactively by attaching rubber stoppers. However, bathtubs with a pre-applied anti-slip surface are more popular because they are more hygienic, durable, and aesthetically pleasing. This inherent anti-slip property of the surface is achieved by providing a certain degree of roughness; that is, the surface exhibits "peaks" and "valleys" on a more or less fine scale. The characteristic length and shape of these structures have a decisive influence on the quality of the slip resistance, the appearance of the surface, and its cleanability—that is, how well or poorly the surface can be freed from the dirt that inevitably accumulates after some use. Almost all bathtubs and shower trays are now made from materials belonging to three classes: enamelled steel, cast mineral, and acrylic glass, more precisely polymethyl methacrylate (PMMA). The latter, in particular, is becoming increasingly popular due to its light weight, freedom in shaping and coloring, resistance to impact and shock, lower thermal conductivity, and consequently warmer feel against the skin. The properties that acrylic glass must possess for use in domestic sanitary applications, such as softening point, thickness, heavy metal content, colorfastness, and thermal and chemical resistance, are defined in the standard DIN EN 263. Acrylic glass that meets this standard is referred to as sanitary acrylic. A relatively new material, similar to cast mineral in its properties and composition, is mineral acrylic, such as LG's HI-MACS product. It combines the malleability and colorability of acrylic with the hardness and durability of traditional ceramic or enameled steel bathtubs. Similar to cast mineral, a high proportion of mineral particles is embedded in a matrix of softer material. However, unlike cast mineral, acrylic glass is used as the matrix instead of epoxy resin. This has the advantage that the desired shape does not need to be cast; subsequent shaping, for example by deep drawing, is possible. However, the production of both the mineral acrylic sheets used as blanks and the forming process are more complex than with sanitary acrylic, which is why bathtubs made from this material are significantly more expensive—two to three times more expensive—than simple sanitary acrylic bathtubs. With mineral acrylic, good slip resistance can be achieved by slightly roughening the surface, for example by sanding. However, this method has not yet been successfully applied to conventional acrylic sanitary bathtubs. While roughening the surface does create a certain degree of slip resistance, which increases with greater roughness, this comes at the expense of easy cleaning and appearance. Experience has shown that with conventional acrylic, roughening the surface does not satisfactorily combine these two properties. Furthermore, the slip resistance achieved through roughening deteriorates significantly after only a short period of use. In conventional shower trays and bathtubs, slip resistance is achieved by applying and bonding a granulate to the surface after the tray has been molded. While this method achieves good to very good slip resistance, it is only effective if the granulate has a relatively large grain size. This makes cleaning the treated acrylic surface more difficult, as dirt deposits accumulate in the deep grooves and valleys, resulting in unsightly and, more importantly, unhygienic dirt accumulation. Furthermore, if the granulate coating wears down over time, perhaps due to increased cleaning efforts triggered by its higher susceptibility to soiling, it is not easily regenerated. Publication WO 01 / 57 117 A1 discloses self-reinforcing semi-finished products made from sanitary acrylic sheets and sanitary ware such as shower trays or bathtubs / basins manufactured therefrom, preferably by thermoforming. The sanitary acrylic used comprises a mineral filler, for which chalk is proposed, among other materials. The sanitary acrylic sheets are to be coated with fillers on the top surface and enriched on the underside, resulting in increased stability and a self-reinforcing property. The filler is to be added in a comparatively high weight proportion of between 0.25 and 4 parts filler per part binder, with the binder comprising all components of the sanitary acrylic except the filler. The filler content proposed in the publication is thus between 20 and 80%.The mean particle size of the filler should be between 0.01 µm and 80 µm, in particular between 0.05 µm and 30 µm, and most advantageously between 0.1 µm and 20 µm. A further disclosure of a sanitary article made of sanitary acrylic with a backing or reinforcement layer comprising fillers can be found in the published application of a European patent EP 0 694 503 A1. Published in application DE 43 09 019 A1, a bathtub or shower tray made of acrylic glass or polymer concrete with a gel-coat surface is disclosed, which has a surface roughened at least in some areas to provide slip resistance. Preferably, the roughening is carried out before deep drawing by blasting with electrocorundum or glass beads, but can also be done by etching, brushing, or grinding. The present invention therefore aims to overcome the problems described and to achieve good slip resistance for sanitary acrylic shower trays, while ensuring good cleanability and an attractive appearance, which is maintained for a long time during use and can also be restored with simple means when worn. As a solution, the present invention presents a manufacturing method for a shower or bathtub with a non-slip surface according to claim 1, a shower or bathtub with a non-slip surface according to claim 7, and a method for regenerating the non-slip properties of a shower or bathtub with a non-slip surface according to claim 10. The inventive method of manufacturing a shower or bathtub initially involves creating a (shower or bath) tray of the desired shape from a provided acrylic sheet blank using a deep-drawing process involving heating, deep drawing, and cooling, in a generally known manner. However, a key characteristic of the present invention is that the blank used differs from conventional sanitary acrylic in that it contains a fine-grained additive. After forming and possibly after carrying out further steps such as applying a reinforcing layer of fiberglass mats and epoxy resin to the back, cutting, etc.In addition to smoothing the edges of the tub and drilling holes, the present invention proposes as a second essential innovation to roughen the surface of the tub in a further step, thereby providing it with a roughness that achieves the best possible compromise between ease of cleaning on the one hand and slip resistance on the other. Although other techniques may also achieve the desired result, in the context of the present invention, this roughening is preferably accomplished by sanding the surface, for example with an orbital or random orbital sander using an abrasive with a specific grit size. To achieve optimal results with regard to the sanding pattern and the associated optical and slip-resistant properties, a relatively narrow grit size range must be maintained, lying between approximately 300 and 350 mesh. The best results were achieved with a grit size of 320 mesh. A mesh is the standard unit of measurement for grit sizes and denotes the number of openings per inch of a sieve required to obtain the particle size distribution used on sandpaper. Abrasives other than sandpaper can be assigned a mesh value by comparing their surface roughness. It should be noted that for higher mesh counts, the characteristic size of the sieve openings, which can be approximated using the simple formula, increasingly deviates from the characteristic particle size after sieving. For example, with a mesh count of 300, the formula above yields a sieve opening size of approximately 75 micrometers. However, the characteristic particle size of the sieved products is approximately a factor of 2 smaller, with the specifics determined by other parameters such as the diameter of the sieve wires and thus the degree of coverage they provide, and therefore depending on the specific sieve model. Besides the grit size of the abrasive, the stroke of the sanding tool, such as an orbital or random orbital sander, is also of great importance. The present invention recommends setting a stroke between 1 and 4 mm. For best results, a range of 2 to 3 mm has proven effective, starting with the larger value and then applying a fine finish to the surface in a second pass using the smaller value. The roughening, in particular grinding, of the tub surface according to the invention creates structures that promote slip resistance. Specifically, a landscape of ideally quite rugged peaks and valleys is created, possessing both a certain characteristic height and diameter. Furthermore, for slip resistance under wet conditions, it is advantageous if these structures are not too small and are as rugged and, on a microscopic level, as possible, sharp-edged. Rounded, wavy structures, on the other hand, lead to a deterioration of slip resistance. A good range for the characteristic surface roughness has been identified as 3 to 10 µm. The best results regarding the desired optimal compromise between the conflicting requirements of slip resistance and cleanability are achieved between 4 and 6 µm. Essential for creating such a surface structure and maintaining its anti-slip properties almost constantly, even during use, is the use of an acrylic sheet blank containing a certain proportion of a fine-grained aggregate. Ideally, this aggregate is of mineral origin, so its particles have a higher hardness than the polymer matrix in which they are embedded. This allows for the creation of relatively rugged surface structures, i.e., peaks and valleys, during the roughening process. The hardness of the aggregate particles also prevents these structures from being prematurely worn down or flattened during normal use. Chalk, or rather chalk powder, has proven to be a very good choice. It can be assumed that the composition of chalk from microfossils, more precisely the calcite shells of dead marine microorganisms (coccoliths or calcispheres) or their fragments, ensures a comparatively homogeneous particle size distribution with a small mean diameter on the order of the microfossils or larger fragments thereof, which lies between 1 and 5 µm. Particles protruding from the surrounding acrylic matrix, after roughening according to the invention, create a roughness that is slightly above the size scale of the mean particle size, at approximately 4 to 6 µm. Other additives are also possible. These include calcium carbonate from sources other than chalk, for example ground calcite crystals, magnesium carbonate, silicon dioxide, especially in the form of pyrogenic silica, or titanium dioxide. The latter, in particular, is also ideally suited as an additive according to the invention. Ground to particle sizes below 1 µm, even small amounts can positively modify the surface properties of the sanitary acrylic blank processed in the inventive method. It is already known to add titanium dioxide to white sanitary acrylic as a pigment, with its weight fraction typically being approximately 2%. The present invention has now made the surprising discovery that only a comparatively small increase in the titanium dioxide content beyond the usual amount has a disproportionate influence on the surface properties and, in particular, the slip-resistant properties of a roughened surface.This can probably be explained by the fact that the addition of titanium dioxide increases the surface strength, which means that rougher surface structures can be created by roughening, which do not wear out as quickly during use as would be the case without the additional titanium dioxide. The bathtub or shower tray according to the invention is characterized by being made of sanitary acrylic containing a fine-grained, preferably hard, mineral aggregate. To achieve noticeable improvements in surface properties, the aggregate's weight percentage should not be too low, but also not too high for reasons of material strength. The precise optimal weight percentage depends on the specific aggregate used; however, the merit of the present invention lies in its recognition that even very small absolute proportions of the aggregate, significantly less than one percent by weight, are sufficient to achieve a very advantageous improvement in the slip resistance achievable by roughening. Particularly good results are obtained with a weight percentage of approximately 0.1 to 0.5% chalk powder and / or 0.02 to 0.1% titanium dioxide.These specifications are to be understood as additive to the components already commonly found in sanitary acrylic. Furthermore, the surface of the tub, made of this sanitary acrylic containing a single additive, is provided with a certain roughness, which has a characteristic length of about 3 to 10 µm, preferably 4 to 6 µm. Due to the high strength of the mineral particles, roughened surface structures can form and last longer under use than sanitary acrylic without or with insufficient amounts of the additive. With a bathtub or shower tray made of sanitary acrylic containing a fine-grained aggregate, it is very easy to regenerate the surface, i.e., reactivate the slip-resistant properties, if these may have diminished after some time of use. This can be done simply by re-sanding the surface of the tray with an abrasive of suitable grit, thus restoring the optimal roughness described above. Since a certain degree of basic roughness is still present in this case, machine sanding is not necessary. Unlike the initial sanding process, which starts from an absolutely smooth and ideally flawlessly glossy surface, this can be achieved using a manual abrasive, such as a simple sanding sponge.This allows users of the bathtub to perform this simple task themselves, saving them the cost of an overhaul by a professional or even a new purchase. Using the inventive method with a sanitary acrylic containing only 0.03% titanium dioxide by weight as an additive, the TÜV-certified slip resistance rating of 'R 10' in the category "Floors in workrooms and work areas with a risk of slipping" and rating group 'C' in the category "Wet barefoot areas" could be achieved by sanding the surface with an orbital sander with a stroke between 2 and 3 mm and with an abrasive of 320 grit. For comparison, the best results achieved with a conventional sanitary acrylic without additional titanium dioxide as an additive were only rating groups 'R 8' and 'A', respectively. The advantages of the present invention are obvious. Firstly, it achieves an optimal compromise between slip resistance and cleanability, which was unattainable with conventional methods. It is particularly noteworthy that the slip resistance of the bathtub or shower tray according to the invention is especially noticeable when wet, precisely when it is needed. When dry, the surface remains very smooth and pleasant to the touch despite the roughening. This contrasts sharply with conventional sanitary acrylic bathtubs made slip-resistant by coating, whose roughness is clearly perceptible even when dry and can be perceived as unpleasant. All of the proposed additives are readily available in large quantities and pose no health risks, especially since they remain firmly bound within the acrylic matrix after the roughening surface treatment step.If roughening is achieved by grinding, this is a simple and very quick process step. Overall, the manufacturing costs of a bathtub or shower tray according to the invention are therefore only marginally higher than those of a conventional one, but offer a much better combination of slip resistance and ease of cleaning. A significant advantage in practice is that the bathtub or shower tray according to the invention, or the tray produced by the inventive method, looks considerably more sophisticated and appealing from an aesthetic point of view than a conventional tray or one produced using conventional methods without slip resistance or with granule-based slip resistance. Its high-quality matte finish is aesthetically on par with the much more expensive mineral acrylic trays. According to the invention, the weight fraction of the additive is between 0.01 and 0.5%, preferably between 0.02 and 0.2%. This allows the desired surface-stabilizing effect to be achieved without excessively thinning the polymer matrix of the sanitary acrylic and thus impairing its strength. Various substances are suitable as fine-grained additives for the acrylic blank used in the process according to the invention. According to the invention, these are magnesium carbonate, fumed silica, titanium dioxide, or calcium carbonate. A mixture of several of these substances is also suitable as an additive. In the latter case, the advantages of a slip-resistant surface according to the invention, with a comparatively low surface roughness and the associated good cleanability, are particularly well achieved when the fine-grained calcium carbonate is in the form of chalk powder, i.e., ground chalk. Chalk is known to be a soft, white sedimentary rock made of limestone. More precisely, it is an agglomerate of ancient microfossils, for example, coccospheres or calcispheres, which were deposited and compressed into a soft rock by geological forces, with the microfossils remaining more or less intact. Since the cohesion of the microfossil fragments among themselves is less than the strength of the microfossils, the chalk, when ground, preferentially disintegrates along the interfaces between adjacent microfossils.Chalk powder is characterized not only by its fine grain size, but also by a very high homogeneity of particle sizes, i.e. a grain size distribution with a comparatively small deviation from the mean. Besides chalk, titanium dioxide is also suitable as an additive according to the invention, as it can also be easily ground into a very fine-grained powder, which is why it is very frequently used as a white pigment in paints. Particles with sizes between 200 and 300 nanometers are typically used, which is very well suited for the application proposed here. Titanium dioxide is already added to sanitary acrylic at a weight proportion of approximately 2% pigment to achieve a rich white color. The present invention is based on the surprising finding that a comparatively small increase in the titanium dioxide content of between 0.02 and 0.1% by weight, corresponding to a relative increase of 1–5%, results in a significant improvement in the slip resistance achievable by roughening, in particular grinding.This is probably due to the fact that the additional titanium dioxide particles give the surface increased abrasion resistance. What all these substances have in common is that they are mineral powders with particle sizes predominantly in the range of a few micrometers. According to the invention, at least 80% of the particles / grains of the fine-grained aggregate have a mean diameter of no more than 5 micrometers, and at least 40% have a mean diameter of no more than 1 micrometer. Advantageous further developments of the present invention, which can be implemented individually or in combination, provided they are not obviously mutually exclusive, will be presented below. The surface roughness after roughening in the last step of the inventive process should have a characteristic length of between 3 and 10 micrometers, preferably between 4 and 6 micrometers. The characteristic length is defined by the mean width and mean height of the surface structures after roughening, which should be approximately equal in size, so that the "peaks" have an aspect ratio of approximately one. The mean height is the area-averaged difference between adjacent high and low points of the surface. Similarly, the mean width is understood as the area-averaged distance between adjacent high or low points. How the surface roughening is achieved is, in principle, arbitrary within the scope of the present invention. Preferably, however, this is done by grinding the surface with an abrasive, particularly preferably using a grinding tool. This is quick, simple, and results in reproducible grinding patterns, which is important for the appearance of the tubs. The abrasive can be, for example, sandpaper. However, a grinding wheel or a grinding stone can also be used, as long as it is sufficiently and accurately adapted to the rough shape of the tub surface, i.e., the curvature on the centimeter and decimeter scale. A random orbital sander is particularly preferred as the grinding tool. The stroke is also an important parameter for the grinding pattern and thus the achieved surface roughness. For the method according to the invention, this should be set between 1.5 and 4 mm, preferably between 2 and 3 mm. The grit of the abrasive, especially sandpaper, must be coarse enough to create a noticeable roughening effect and thus provide slip resistance, but on the other hand, it should remain fine enough to ensure good cleanability and a smooth, matte finish. Experience has shown that a grit size in the range of 300 to 350 mesh, preferably around 320 mesh, best meets these requirements. Preferably, the grinding is carried out in at least two passes, with a larger stroke of approximately 3 mm being used initially, and then reduced to 2 mm in subsequent passes. For the first pass, the abrasive may be coarser, in the range of 200-300 mesh, to accelerate the process. However, the grit size of 320 mesh recommended above is preferably used for the final grinding pass. A consistently clean grinding pattern and therefore homogeneous slip resistance can be achieved if the surface of the shower or bathtub is designed without kinks or edges, i.e., with a continuous, gently curved shape. Between the steps of deep drawing and roughening the surface of the inventive method, further work steps can also be carried out on the shower or bathtub. These can include, for example, applying an underside reinforcement made of glass fibers or synthetic resin, trimming or cutting the edges of the tub, or drilling holes, for example for the drain or for bubble and / or massage jets. The non-slip shower or bathtub according to the invention preferably has a surface roughness with a characteristic length of between 3 and 10 micrometers, preferably 4 to 6 micrometers. This can be achieved by grinding the surface with an abrasive having a grit size of between 300 and 350, particularly preferably about 320 mesh. The inventive method for regenerating the non-slip surface of a bathtub or shower tray made of sanitary acrylic containing a fine-grained aggregate is preferably carried out by grinding with an abrasive having a grit size of between 300 and 350 mesh, preferably about 320 mesh. This regeneration grinding can be performed mechanically, for example with an orbital or random orbital sander. However, it is preferably carried out manually, particularly preferably using a sanding sponge with the specified ideal grit size. This is simple and cost-effective and, due to the remaining roughness, no more time-consuming than the mechanical grinding process during the manufacturing of the tray.

Claims

Method for manufacturing a shower or bathtub made of sanitary acrylic with a surface having anti-slip properties, wherein i. a flat blank made of sanitary acrylic is provided, ii.The blank is formed into a tub of a desired shape by heating and deep drawing, wherein the surface of the blank or the tub is roughened to produce the anti-slip property, characterized in that: - the roughening of the surface takes place in a further step after the tub has been formed, and - the material of the blank contains a fine-grained additive by weight of between 0.01 and 0.5%, preferably between 0.02 and 0.2%, - wherein the fine-grained additive is: ◯ calcium carbonate, in particular chalk powder, and / or magnesium carbonate and / or pyrogenic silica and / or titanium dioxide, and ◯ has a particle size distribution in which at least about 80% of the particles have a mean diameter of less than 5 µm and at least about 40% of the particles have a mean diameter of less than 1 µm. Method according to claim 1, characterized in that the roughness has a characteristic length of 3 - 10 µm, in particular of 4 - 6 µm. Method according to one of the preceding claims, characterized in that the roughening is carried out by grinding. Method according to claim 3, characterized in that the grinding is carried out using an orbital or random orbital sander with a stroke between 1.5 and 4 mm, preferably between 2 and 3 mm, and / or using an abrasive with a grit size between 300 and 350 mesh, preferably about 320 mesh. Method according to one of claims 1 - 4, characterized in that the surface of the tub is designed to be free of kinks. Method according to one of claims 1 - 5, characterized in that further processing steps are carried out between the forming of the tub and the roughening, in particular the application of an underside reinforcement made of glass fibers and / or synthetic resin, the trimming of the tub edges and / or the introduction of bores, for example for the drain. Shower or bathtub made of sanitary acrylic with a surface having a non-slip property, which is achieved by roughening the surface of the tub, characterized in that the sanitary acrylic contains a fine-grained aggregate to a weight fraction of between 0.01 and 0.5%, preferably between 0.02 and 0.2%, wherein the fine-grained aggregate is calcium carbonate, in particular chalk powder, and / or magnesium carbonate and / or pyrogenic silica and / or titanium dioxide, and has a particle size distribution in which at least about 80% of the particles have a mean diameter of less than 5 µm and at least about 40% of the particles have a mean diameter of less than 1 µm. Shower or bathtub according to claim 7, characterized by a surface roughness with a characteristic length of 3 - 10 µm, in particular 4 - 6 µm. Shower or bathtub according to claim 9 or 10, characterized in that the roughness is produced by grinding with an abrasive which preferably has a grain size of 300 - 350 mesh, in particular about 320 mesh. Method for regenerating the slip-resistant property of the surface of a sanitary acrylic bathtub, characterized in that the surface is roughened with an abrasive, wherein the sanitary acrylic contains a fine-grained aggregate to a weight fraction of between 0.01 and 0.5%, preferably between 0.02 and 0.2%, and wherein the fine-grained aggregate is calcium carbonate, in particular chalk powder, and / or magnesium carbonate and / or pyrogenic silica, and has a particle size distribution in which at least about 80% of the particles have a mean diameter of less than 5 µm and at least about 40% of the particles have a mean diameter of less than 1 µm. Method according to claim 10, characterized in that the surface is provided with a roughness having a characteristic length of 3 - 10 µm, in particular 4 - 6 µm. Method according to claim 10 or 11, characterized in that the roughening is carried out by grinding with an abrasive having a grain size of 300 to 350 mesh, in particular about 320 mesh. Method according to one of claims 10 - 12, characterized in that the grinding is carried out by hand, in particular with a grinding sponge.