DE1796014A1 - Process for the production of molded parts from thermally foamed silicates - Google Patents

Description

Patent attorney Dr. H. Welssenfeld; P 507 D.

67 Ludwigshafen am Rhein August 9, 1968

AP b / gs

Applicant : GrUnzweig & Hartmann Aktiengesellschaft 67 Ludwigshafen am Rhein

Process for the production of molded parts from thermally foamed silicates

Molded parts made of foamed silicates such as glass, clay, slag, basalt and the like are made by various known methods manufactured. For example, the raw material can be finely ground powder with the addition of propellants in metallic or ceramic forms or between all-round enclosures lietal strips are heated to the softening point. Propellant gases are generated by the propellant, so that the mass foams and fills the surrounding mold. In this process, it is necessary to provide the mold with a release agent, to prevent the foamed masses from sticking to the mold. The release agent must already be at a low temperature can be applied in the form of a liquid sizing agent. This measure and the demolding of the required after foaming foamed goods, which often break the foamed When molded parts come, an economical production of foamed molded parts is not possible with the help of this process. Further is L in view of the dimensional stability of the shaping agents, especially when shaping by dander, the expansion temperature is limited upwards, so that the method is only suitable for processing of materials that foam up at relatively low temperatures, but the shapes made from expensive, refractory] material must be made by clLu thermal stresses subject to a high VerachLolKH, which affects their lifespan Very limited and therefore frequent repairs or replacements

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The costly forms required, eventually arise Considerable costs in this process due to the high heat loss that arises from the fact that the Forms required thermal energy, which is up to the 2O-facben for the actual foaming required thermal energy is, with the molds carried out of the foaming oven and unused to the Environment.

In another known method, a layer is first applied the powdered raw material with a propellant Applied in a vertical shaft on a movable base and there foamed, "oh the foaming becomes the base removed and further raw material is added in layers to the foam that has already formed. As a result of gravity the foam moves downward in hatred, as in the end face new foam is created. The desired molded parts are then cut to size from the molding compounds foamed in this way. at This process is often associated with sticking together the foamed-out Molding compounds with the fixed shaft walls, often the foam structure is also created by the friction on the wall of the

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Shaft destroyed. But also the molded parts obtained in this way can not satisfactory, because the raw material is applied in layers into the shaft instead of a desired one homogeneous foam structure result in a large number of display layers, with the connection between the individual layers often quite different 1st.

In a further process, foamed granules are removed in a hot, plastic state by applying pressure, if necessary. pressed into molded parts with the addition of a thermally softened binder. The molded parts produced in this way often have Significant deficiencies. So often remain in the structure of the format parts compacted crusts of the individual granules are obtained, either by superficial burnout when the granules are expanded or arise from the fact that beL the manufacture of the distended

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Granules in Bitthofen a release agent is used to make a Avoid sticking of the granules. The format parts also have a high density or thermal conductivity that their Very severely restrict possible applications. These high densities are a consequence of the crust already mentioned The granules "are partly due to the deformation process required compression that must be maintained until it cools down.

The disadvantages of known methods can be solved according to the invention thereby avoid that the starting material is pressed into a blank, then expanded in a foaming oven and after the Blowing is brought into the desired shape by pressing. Even when the blank is pressed, it may become trapped Air, in particular oxygen, is removed so that voids or internal burn-out arise in the foamed molded parts is largely avoided. The blank already has the final shape of the desired molded part in smaller dimensions, so that expensive shaping means can be dispensed with. By eliminating the molds, the energy costs are significantly reduced, since only the energy required for the actual expansion of the molded parts has to be supplied. The pressed blank becomes the Swelling set on a simple firing pad, which is made of a temperature-resistant bed such as sand, cement, aluminum oxide, Kaolin powder or the like. Is. Due to the temperature resistance of the bed, the individual grains are sintered with one another prevented, so that the fill always remains slippery. This reduces the friction between the molded part and the Base reduced very much, so that the pressed blank essentially retains its original shape when it is foamed. The rubble base proposed according to the invention can the use of a wet, i.e. applied at a low temperature, sizing can be dispensed with, which means that the underlay

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always stays at the same temperature. The pouring pad can also be used several times during a Sizing has to be renewed with each oven pass and is therefore lost.

In another embodiment of the method, the blank placed on a melt and foamed there. The material of the melt has a melting temperature below the Foaming temperature is and can depending on the starting material foamed molded parts consist of a glass or a metal. α Through a suitable combination of the foaming and the melting material from the foaming oven can be kept low. This is achieved by using a melt as a support for the molded part to be foamed Heat transfer from the base to the molded part is very good and the necessary to move the molded part in the Schäutaofen The thrust force is low so that the pyroplastic foam structure is not destroyed when it is moved. In a continuation this embodiment of the method according to the invention can by wetting the foamed molded part with the melt one that improves the surface quality of the molded part Production skin arise.

As already mentioned, the blank retains essentially φ during foaming lent its original and then final shape, it takes place only a linear increase in dimensions and thus an increase in volume. Irregularities of the foamed forint egg will be immediately after puffing as soon as the surface temperature of the molded part is below the bonding temperature, but still while the foamed molded part is in the hot plastic State is through briefly acting shaping tools, the temperature of which is below the foaming temperature, in the brought its final shape.

The for the press front number; exploring? before cooling the surface of the Molding must; are and can be below the bonding temperature

can be the discharge

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can be brought about, for example, that the molded part from the SchäunucoB * is brought into an area of lower temperature will. Due to the intense heat radiation of the molded part at the foaming temperature, the surface temperature drops very quickly under the adhesive limiters, - ;. This process can gßf. by a Convective cooling supports «ground. Likewise, by the cooling effect of the kept at low temperature the dissipating Tools during the time of contact with the molded part the required cooling can be achieved. By appropriate heating or cooling of the forngebenden factory eye, it is possible to use a Surface layer of sufficient thickness of the molded part under the To cool down the temperature limit of the plasticity. This makes this layer dimensionally stable and prevents the after discharge Molded parts another change in shape due to the internal pressure of the propellant gases. It is essential that the deformation together With the formation of a dimensionally stable crust inside the molded part, an overpressure is created which causes the visible structure to open up prevents subsequent cooling of the interior, whereby the stabilization time can be shortened considerably.

The erfindungsgeeäes proposed method is particularly suitable for the processing of clays and leichttonen and raw materials whose 8chäu "temperature is above 900 ^0C. Cohesive raw materials such as sB clay are intimately mixed with water and / or liquid or solid blowing agents and either molded in presses, screw presses or extruders or the like. Particularly suitable propellants are oil, sulphite waste liquor, molasses, glycol, starch, ruse, coal, coke meal and the like. .

Non-cohesive powdery raw material, such as finely ground GJas, slag, rock flour odor dorcl. can by adding binding propellants such as melasae, bitumen and the like. or by adding binding additives such as vra ^ scrglai ;, AluuLruuiphonphalon or alkaline earth phosphates Ln a cohesive state brought and then grouted.

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Non-cohesive raw materials mixed with propellants can be tabletted by using very high pressures. They preferably get one at lower than that Schäujateniperatur emollient supplement, reducing the occurrence of temperature breaks when waking up can be avoided because the aggregate, which softens at a low temperature, takes over the binding. As such a supplement are low-emollient, inorganic ones Salts such as boric acid, soda and the like. Or preferably to use finely powdered plastics that in turn act partially as a propellant.

As mentioned above, already has the pressed blank substantially the final shape of the desired molded parts "to prevent Vm, the blank during the foaming that arbitrarily on the firing base propagating, it is required that at the selected Schäuaittunperatur the viscosity of the heated material remains high enough to avoid falling apart. The expansion pressure of the propellant gases must be large enough to expand the material to a high degree of expansion with this restrictive requirement. It is known that in this case, ie if the viscosity is not too low, the pore structure of the foam becomes uniform and fine-pored. With appropriate additions to the raw material, its viscosity can be adjusted in such a way that the stated requirements can be met. To increase the viscosity, for example, compounds with a high content of Al ₃ O ₃ or SiO ₂ can be added. The reduction in viscosity can be achieved, for example, by adding so-called fluxes with a high content of alkalis, Fe ₂ O ₃ , CaO or MgO. i

The proposed method according to the invention enables a economical production of molded parts from foamed silicates, which also differ in terms of quality from the molded parts produced by known processes can therefore also be used for a wide variety of purposes, for example as a lightweight furnace stone, as a schaH and Warna · " insulating building board or as an insulating panel. 209110/0626

Claims (5)

Claims P 507 D 1. Process for the production of molded parts from thermal Expanded silicates, such as clay, glass, slag, basalt and the like., characterized in that the starting material pressed into a blank, then expanded in the Schäura furnace and after expansion by pressing is brought into the desired shape. 2. The method according to claim 1, characterized in that the blank is already in one of the final molded part corresponding shape is pressed. 3. The method according to claim 1 and 2, characterized in that the pressing of the foamed molded part in the final Form takes place by short-acting molding tools, with the molded part in the hot, plastic state is located. 4. The method according to claim 1 to 3, characterized in that the edge layer of the molded part upon contact with the asking who! 'cug by its cooling effect the temperature limit of plasticity is cooled and stabilized will. 5. The method according to claims 1 to 4, characterized in that as a firing base for foaming the pressed Blank is a bed of refractory, free-flowing material such as sand, cement, aluminum oxide, Kaolin powder or the like. Serves. 6 "Process according to Claims 1 to 4, characterized in that that as a firing base for foaming the pressed blank, a melt that is indifferent to this like a Suitable glass, metal or the like. Serves. Ludwigshafen, 8/9/68
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