METHOD FOR MANUFACTURING A SANITARY ITEM

Description

[0001] The invention relates to a method for producing a sanitary article, according to the preamble of patent claim 1.

[0002] Articles of daily use, such as sanitary ware or household items, which can be in the form of shower trays, bathtubs, washbasins, toilet lids, a seat ring or bathroom furniture, a floor or wall panel, a bathtub apron, but also in the form of a chair, table, sofa or other piece of furniture, have been known for a long time.

[0003] Such everyday objects can be made of many different materials, such as wood or metal, but also of plastic.

[0004] For such plastic consumer goods, a manufacturing process is often used in which a polymerizable plastic monomer is polymerized using a polymerization initiator, with the finished polymerized plastic product then taking the shape of the desired consumer goods. Such production of a consumer goods by polymerization is usually carried out in a hollow mold, which represents a precise negative contour of the consumer goods to be manufactured and into which the polymerizable plastic monomer and polymerization initiator are poured.

[0005] One problem that arises, however, is that the polymerizing plastic shrinks during polymerization. This consequently leads to a loss of surface quality on both sides of the manufactured article.

[0006] In the past, attempts were made to solve this shrinkage problem by heating the mold halves in which the desired consumer article was to be polymerized to different temperatures, distinguishing between a visible side and a reverse side. According to the prior art, the mold half of the mold facing the visible side was heated more intensely and more quickly than the mold half assigned to the reverse side. This resulted in shrinkage of the polymer mass occurring primarily on the reverse side of the desired consumer article. In this way, according to the prior art, a reasonably smooth and attractive visible side of a consumer article could be produced, but in contrast, the reverse side of the manufactured consumer article showed significant signs of shrinkage of the polymer mass.

[0007] Another method used in the past to improve the external appearance of consumer goods made from polymerizable materials was to fill the empty volume in the hollow mold caused by the shrinkage process during polymerization with additional plastic monomer in order to compensate for the shrinkage volume and thus obtain a reasonably smooth surface of the manufactured consumer goods on both the visible side and the back.

[0008] Furthermore, shrinkage, which primarily occurs on the back of the product and causes a poor surface finish, also leads to a weakening of the product's strength, which ultimately must be compensated for by increasing the product's thickness in order to meet the relevant EN standards for the product, such as EN 15334. However, this in turn means that more material must be used to manufacture the product, or rather, the consumer item, which in turn leads to higher manufacturing costs for the consumer item.

[0009] However, the disadvantages associated with this process are not only the complicated process management, especially when refilling the additional plastic monomer, but also the increased material requirement of plastic monomer due to the refilling, which in turn leads to increased costs in the production of the desired consumer article.

[0010] DE 1 813 900 A1 and DE 34 36 458 C1 disclose a toilet seat or thin-walled foam molded parts, such as a tub liner for bathtubs or shower trays. These are manufactured using blowing or propellant agents, such as hydrocarbons, chlorofluorocarbons, or nitrogen and azo compounds, in a size-variable mold that expands under the expansion pressure of the blowing or propellant. These processes not only have the disadvantage of requiring the use of blowing or propellant agents that are environmentally problematic, but they also result in products that require post-processing at the seam boundaries where the mold used opens and thus expands.

[0011] From DE 689 11 148 T2, a process for producing foamed plastics is also known, but this is not suitable for the production of sanitary articles, since it is not possible to produce a pore-free surface with the process therein.

[0012] The invention is based on the object of avoiding these disadvantages known from the prior art in the production of a consumer article from a polymerizable plastic in a simple and cost-effective manner and of providing a method and a consumer article produced thereby with an optimized smooth, optionally structured and dimensionally accurate surface contour.

[0013] This object is achieved by a method according to patent claim 1 for producing such a consumer article.

[0014] In particular, the method leads to a consumer article, namely a sanitary article, such as a shower tray, bathtub, washbasin, toilet lid, seat ring or bathroom furniture, a floor or wall panel, an apron for a bathtub or a household article, such as a chair, table, furniture, for example a sofa, made of an at least partially polymerized plastic material, wherein the consumer article comprises a sandwich-like structure with a core region having bubbles arranged inside the consumer article, which core region is surrounded by a shell region made of fully polymerized plastic material.

[0015] The article of daily use has a sandwich-like structure consisting of a polymerized plastic shell with a smooth and dimensionally accurate surface contour, which has a core area with bubbles in its interior, by means of which shrinkage of the polymerized plastic material on the surface of the article of daily use to be manufactured is compensated or avoided.

[0016] In an astonishingly simple and extremely efficient way, the inventors of the process developed for the production of the consumer article have succeeded in avoiding shrinkage of the monomer material used to produce the consumer article during polymerization and in producing a consumer article that has an optimized smooth and / or structured and dimensionally accurate surface shape not only on one visible side, as in the prior art, but on its entire outer surface, which corresponds exactly to the inner surface and structure of the hollow mold used.

[0017] In contrast to the shell region of the consumer article surrounding the core region, which consists of fully polymerized polymer, i.e. the finished polymer plastic from which the consumer article is made, the core region of the consumer article having bubbles does not yet have and / or not yet fully polymerized monomer material of the plastic material.

[0018] Due to the fact that the core region of the article of daily use comprises bubbles, the core region has a lower density than the shell region surrounding the core region, which advantageously contributes to a lower weight of the article of daily use compared to comparable articles of daily use manufactured according to the prior art.

[0019] The core area extends, following the geometry of the everyday object, in a sandwich-like manner within the entire everyday object. The shell area surrounds the core area over the entire shape, or rather geometry, of the everyday object. The blistered core area extends into all extremities as well as protrusions and recesses of the everyday object, or rather follows the respective contour of the everyday object. However, the blistered core area never extends to the surface of the everyday object, so that this surface of the everyday object always has a perfect surface, free from any defects and / or imperfections, neither in terms of material nor in terms of appearance.

[0020] In this case, the core area of ​​the article of daily use is preferably completely surrounded by polymerized plastic material of the casing area of ​​the article of daily use, so that the article of daily use has the desired smooth and / or structured, dimensionally accurate surface on its entire outer surface and the article of daily use has a homogeneous weight distribution.

[0021] The article of daily use preferably consists of only a single material, namely the monomer used to manufacture the article of daily use and the resulting polymer material through polymerization. Additional solid, liquid, and / or gaseous expandable and / or expandable substances are not necessary to manufacture the base body of the article of daily use.

[0022] According to a preferred embodiment of the invention, the thickness of the core region is essentially in the range of one-third of the total thickness of the article of daily use ±30%, preferably ±20%, and particularly preferably ±10%. With respect to a cross-section of the article of daily use, the core region is preferably arranged essentially centrally between approximately equally thick shell regions of a respective section of the article of daily use, whereby the article of daily use achieves a substantially constant weight distribution and stability across its entire body.

[0023] Furthermore, the core region and the shell region of the article of daily use are each formed from an identical polymerizable plastic material. Thus, according to one embodiment of the invention, as mentioned above, the article of daily use advantageously consists of a homogeneous plastic material, which has an extremely positive impact not only on its production but also on its recyclability. With regard to the production of the article of daily use, only a single polymerizable plastic material is required. In this respect, the article of daily use can be manufactured simply and cost-effectively, since no additional plastics and / or auxiliary materials are required, and any additions of other, possibly also polymerizable, plastics need not be taken into account.With regard to the recyclability of the consumer item, this means that no complex separation of different plastics or other materials is necessary, which would often not even be possible, but the consumer item can be recycled "as is."

[0024] Due to the homogeneous structure of the article of daily use, the article of daily use can advantageously be constructed monolithically, which in turn contributes to improved stability of the article of daily use and the possibility of manufacturing the article of daily use in one step, i.e. without any assembly measures or post-processing steps.

[0025] With regard to the materials that can be used to manufacture the article, it should be noted that, although the use of a single polymerisable plastic is preferred, the use of mixtures of plastics is also possible if desired.

[0026] According to a preferred embodiment of the invention, the plastic material used is in particular at least one thermally curable resin, which is based in particular on one or more of the following substances: acrylate, polyester, urethane, epoxy, polymer concrete, mineral casting or mixtures of the aforementioned substances.

[0027] In this regard, it should be mentioned in particular that these can also be filled thermally curable resins, such as a quartz-filled methacrylate.

[0028] The object of the invention is achieved by a method for producing a consumer article, namely a sanitary article, according to claim 1, wherein the method comprises the following steps: a) Producing a reaction mixture by mixing a polymerizable plastic material with at least one low-temperature initiator and with at least one high-temperature initiator; b) Filling the reaction mixture into a cavity of a mold for producing the consumer article, wherein the mold is formed from at least two interconnectable, heatable mold parts; c) Heating the mold parts to a first temperature to activate the at least one low-temperature initiator to initiate polymerization of the reaction mixture; d) Further heating the mold parts to a second, higher temperature to activate the at least one high-temperature initiator; e) Maintaining the second temperature for a predefined period of time; f) Cooling the mold parts; and g) Demolding the consumer article produced from the reaction mixture.

[0029] An important aspect of the process according to the invention is that a polymerizable plastic monomer is used, which is polymerized using two polymerization initiators that can be activated at different temperatures. These two different polymerization initiators are a low-temperature initiator and a high-temperature initiator. These two polymerization initiators are mixed with the polymerizable plastic monomer and, according to one embodiment of the invention, are filled into a cavity of a hollow mold for producing the consumer article at the lowest possible temperature, at which evaporation of the reaction mixture and, in particular, of the monomer is avoided.

[0030] As a further important process step, respective mold parts of the mold forming the hollow mold, which according to the invention are assigned to a visible side and a back of the sanitary article to be produced, are heated to a first temperature at which the low-temperature initiator triggers a polymerization of the plastic monomer in order to produce the polymer resulting from the plastic monomer.

[0031] Due to the fact that the polymerization is started by heating the mold parts of the mold forming the hollow mold to the first temperature at which the low-temperature initiator is activated, the polymerization of the plastic begins adjacent to the mold parts of the mold forming the hollow mold, so that the polymer forming the later article of use forms adjacent to the inner surface of the hollow mold.

[0032] As the process progresses, the temperature of the mold parts forming the hollow mold is raised to the second, higher temperature, at which the high-temperature initiator is activated, increasing the polymerization rate and further increasing the temperature due to the exothermic reaction heat within the plastic. This leads to at least partial evaporation of the plastic monomers and the formation of bubbles, resulting in a concomitant increase in pressure within the plastic. This increase in pressure within the plastic, in turn, causes the shell of the future consumer article, formed from the already fully polymerized polymer, to be pressed firmly and intimately against the inner surface of the hollow mold.

[0033] At this point, it should be expressly noted that the temperature increase, first to the first temperature and then to the second temperature, occurs continuously and, according to the invention, does not require "holding" the temperature, for example, at the first temperature. Rather, according to the invention, the first temperature is "passed through" to the second temperature as the temperature is increased, starting with, as mentioned above, the lowest possible filling temperature for the monomer or reaction mixture, whereby the low-temperature initiator is activated without the temperature increase being stopped upon reaching or in the region of the first temperature or being held for some time. According to the invention, the temperature increase is stopped only upon reaching the second temperature, which is then maintained as explained below.In this way, the method according to the invention for producing the consumer article can be carried out very quickly and effectively.

[0034] Another important point of the process according to the invention is to maintain the second higher temperature for a sufficiently long time to prevent premature termination of the polymerization process and thus to maintain an internal pressure within the plastic.

[0035] Furthermore, it has been found according to the invention that another important point of the process according to the invention is to limit the temperature rise within the polymerizing plastic in such a way that the plastic monomer begins to boil and in this way exerts pressure against the inner quasi-surface of the already polymerized polymer and in this way presses the polymerized polymer against the inner wall of the hollow mold, but excessive boiling is avoided in order to keep the bubbles generated by the boiling of the plastic monomer within the core region of the consumer article to be produced, without the bubbles penetrating into the shell region of the consumer article to be produced.

[0036] According to the invention, this temperature limitation is achieved on the one hand by the mold parts of the mold forming the hollow shape being initially kept at the second, higher temperature. From a certain point in the polymerization process, at which the temperature of the polymerizing plastic has exceeded the second, higher temperature due to the exothermic reaction heat of the polymerization, the mold parts of the mold forming the hollow shape no longer serve as a heating means but as a cooling means, so that no heating beyond the second, higher temperature takes place on the mold parts. The second, higher temperature therefore represents the final heating temperature of the process according to the invention. In a further step, the mold parts forming the hollow shape are then cooled and the consumer article produced from the reaction mixture is demolded.

[0037] According to a preferred embodiment of the invention, the steps for heating the molded parts of the mold are carried out synchronously both on the visible side and on the back, in particular on all sides, of the article of daily use to be produced.

[0038] According to the invention, it is thus achieved in an extremely simple manner that a first quasi-low-temperature polymerization initiated by the low-temperature initiator, which leads to the formation of the fully polymerized shell region of the article to be produced, takes place simultaneously, and the shell region thus forms uniformly and simultaneously along the entire inner surface of the hollow mold. For this reason, heating steps c) and d) are carried out essentially, in particular precisely, synchronously.

[0039] Furthermore, according to a further embodiment of the invention, the step of maintaining the temperature according to step e) is also carried out essentially, in particular precisely, synchronously for all molded parts forming the hollow mold in order to bring about simultaneous activation of the high-temperature initiator over the entire hollow mold, so that the temperature necessary to increase the internal pressure within the plastic matrix to form bubbles of monomer material is also set simultaneously over the entire hollow mold, or the entire consumer article to be produced, and due to the associated pressure increase, the polymer material forming the shell region is pressed evenly and homogeneously against the inner surface of the hollow mold.

[0040] According to a further embodiment of the invention, the cooling of the molded parts in step f) can be carried out asynchronously, wherein the temperature of the molded parts on the visible side of the article to be manufactured is preferably kept at a higher temperature for somewhat longer than on the back of the article to be manufactured, but is then reduced more quickly than on the back of the article to be manufactured. Cooling of the back of the article to be manufactured, in contrast, occurs somewhat earlier and more slowly. This also facilitates demolding of the back of the article to be manufactured, wherein the perfectly manufactured surfaces of the article to be manufactured, in particular on both its visible side and its back, are retained during demolding of the article.

[0041] By means of such asynchronous cooling, the invention achieves that the bubbles formed inside the manufactured article of daily use, i.e. the bubbles formed in its core region, are virtually "frozen" within the formed polymerized shell region, whereby the bubble size and thus the pressure generated by the bubbles against the shell region are maintained.

[0042] As has been shown according to the invention, shrinkage of the plastic used to produce the consumer article can be practically completely avoided or compensated for by the above-mentioned process, since the shrinkage of the plastic during the polymerization reaction is practically, in particular completely, compensated for by the volume of the bubbles formed inside the plastic.

[0043] In an extremely advantageous manner, according to the invention it is therefore neither necessary to refill polymer material in order to compensate for any shrinkage, as was always necessary in the prior art, nor to carry out complex post-processing of the manufactured article of daily use in order to eliminate surface defects caused by the shrinkage process.

[0044] According to a further embodiment of the invention, the molded parts from which the hollow mold necessary for producing the desired article of daily use is composed are joined together to form a pressure-resistant, stable mold that withstands the internal pressure generated by the heated plastic material.

[0045] With regard to the polymerization initiators used for the process according to the invention, according to one embodiment of the invention, peroxide compounds are preferably used, wherein the respective low-temperature initiator has an activation temperature in the range of 40°C ± 15°C, preferably ± 12°C and particularly preferably ± 8°C and the high-temperature initiator has an activation temperature in the range of 110°C ± 20°C, preferably ± 15°C and particularly preferably ± 10°C.

[0046] The use of polymerization initiators with these temperature ranges offers the significant advantage according to the invention that with such polymerization initiators almost all common polymerizable plastic materials that can be initiated by means of peroxides can be used for the process according to the invention.

[0047] In summary, the subject matter of the present invention can be stated as follows.

[0048] By using a so-called sandwich protocol according to the invention and a recipe, namely a reaction mixture of a plastic monomer and two polymerization initiators that can be initiated at different temperatures, i.e. a low-temperature initiator and a high-temperature initiator, almost all shrinkages can be compensated and a good surface quality can be achieved on both sides of a consumer article.

[0049] Using the so-called sandwich protocol, shrinkage during a polymerization reaction can be avoided and smooth surfaces can be achieved on both sides of a consumer product. Furthermore, a more stable consumer product can be created, since it is known that a surface without defects is significantly stronger than one with defects.

[0050] According to the invention, a temperature program is first required to ensure that polymerization begins simultaneously on both sides of a consumer article to be manufactured, i.e., on the front and back of the product or consumer article. The simultaneous polymerization reaction on both sides of the consumer article to be manufactured leads to a high internal temperature in the polymerization matrix.

[0051] The so-called sandwich protocol ensures that the front and back of the product to be manufactured are "run" with the same temperature profile. This ensures a smooth surface on both sides of the product.

[0052] Due to the high heat effect on the material to be polymerized, which comes from both sides of the mold simultaneously, it is important that 1) in addition to a low-temperature initiator, a second initiator is used that is activated at a higher temperature to prevent premature termination of the polymerization reaction; and 2) a certain pressure is maintained and a fine temperature gradient is applied in the mold to prevent excessive boiling of the monomer.

[0053] Due to the exothermic polymerization reaction, the temperature inside the material will exceed the temperature of the mold. Therefore, the mold parts act as a cooling unit, so that the monomer only boils slightly in the center.

[0054] The bubbles formed in this process due to the heating of the monomer have sufficient volume to compensate for shrinkage due to the polymerization reaction of the plastic.

[0055] The internal pressure and expansion ensure that the product comes into contact with both halves of the mold during polymerization and that the product surfaces are perfect and free of defects.

[0056] By using the sandwich protocol and formulation, shrinkage, which would otherwise be compensated for by refilling the mold or compressing the space between the two mold halves, can be compensated for or even avoided. The shrinkage of a filled resin is approximately 9% of the total product weight.

[0057] Furthermore, the method according to the invention offers the advantage of eliminating additional process steps, such as those required in the prior art. For example, compensation by refilling requires the refilled material to be polymerized, which requires additional time. Furthermore, this additional refill material, i.e., plastic monomer, also incurs additional costs and increases the weight of a standard product, so that the latter weighs more and is therefore heavier and more expensive to transport.

[0058] In addition, to avoid unsightly surfaces, standard everyday objects are usually assembled from two mold halves, whereby a flexible rubber used between the mold halves is used to press them together, creating an edge in the space between them which has to be removed by cutting after curing, which in turn means additional work and costs given the current state of the art.

[0059] Further embodiments of the invention emerge from the subclaims.

[0060] The invention is described below using an exemplary embodiment, which is explained in more detail with reference to the figures. Herein: Fig. 1 shows a schematic representation of a consumer article according to the prior art in cross-sectional view; and Fig. 2 shows a schematic representation of a consumer article according to an embodiment of the invention in cross-sectional view.

[0061] In the following description, the same reference numbers are used for identical and equivalent parts.

[0062] Fig. 1 shows a cross-sectional view of a conventionally manufactured article. As can be seen, the article is completely polymerized. Compensating for shrinkage during a polymerization manufacturing process in such an article with a given hollow shape can only be achieved by adding additional monomer material.

[0063] Fig. 2 shows a schematic representation of a consumer article 10 according to an embodiment of the invention in cross-sectional view. As can be seen, the consumer article 10 has a core region 20 having bubbles 40 and also a shell region 30 that completely surrounds the core region 20. According to Fig. 2The core region 20 is indicated by a dashed line, with bubbles 40 made of plastic material, in particular monomer material, located within the core region 20. These bubbles have formed due to a temperature increase caused by the exothermic reaction heat during polymerization. These bubbles within the article of daily use 10, and in particular within the shell region 30, generate an internal pressure against the shell region 30, so that the shell region 30 conforms tightly to an inner surface of a hollow mold during the polymerization reaction. The article of daily use 10 has a smooth and contour-accurate surface on all external surfaces. List of reference symbols

[0064] 10Utility object 20Core area 30Sheath area 40Bladder

Claims

1. A method for manufacturing a sanitary item (10), wherein the sanitary item (10) comprises a sandwiched structure with a core area (20), which has bubbles (40), is arranged inside of the sanitary item (10), and is surrounded by a jacket area (30) comprised of fully polymerized plastic material, which forms a bubble-free plastic jacket with a smooth and true-to-form surface contour, characterized by the following steps: a) Manufacturing a reaction mixture by mixing a polymerizable plastic material with at least one low-temperature initiator and with at least one high-temperature initiator; b) Filling the reaction mixture into a cavity of a mold to manufacture the sanitary item (10), wherein the mold consists of at least two heatable mold parts that can be connected with each other; c) Heating the mold parts to a first temperature for activating the at least one low-temperature initiator so as to initiate a polymerization of the reaction mixture; d) Further heating the mold parts to a second, higher temperature for activating the at least one high-temperature initiator; e) Maintaining the second temperature for a predefined timespan; f) Cooling the mold parts; and g) Demolding the sanitary item (10) manufactured out of the reaction mixture.

2. The method according to claim 1, characterized in that the heating steps c) and d) and / or the maintaining step e) are essentially performed synchronously.

3. The method according to one of the preceding claims, characterized in that a cooling of mold parts in step f) is performed asynchronously.

4. The method according to one of the preceding claims, characterized in that the mold parts are joined together to form a pressure-resistant, stable mold.

5. The method according to one of the preceding claims, characterized in that peroxide compounds are used as polymerization initiators, wherein the low-temperature initiator has an activation temperature within a range of 40 °C ± 15 °C, preferably ± 12 °C, and especially preferably ± 8 °C, and the high-temperature initiator has an activation temperature within a range of 110 °C ± 20 °C, preferably ± 15 °C, and especially preferably ± 10 °C.