Process for producing building elements, preferably sand brick from granular mineral raw material

Abstract

The subject of the invention is a process for producing building elements, preferably a brick, and particularly preferably a sand brick, from granular mineral raw materials, wherein the mineral raw material is preferably sand, and particularly preferably desert sand. The essence of the process according to the invention is that the granular mineral raw material is mixed with dry-state urea-formaldehyde cross-linking catalyst base material, then the solution of the cross-linking catalyst initiating polymerization is prepared separately, the solution is added to the dry mixture prepared in the previous step, the wet mixture is poured into the press mold, then pressed in a hot press, removed from the press, and finally the product is left to stand until polymerization is fully completed.

Description

[0001] PROCESS FOR PRODUCING BUILDING ELEMENTS, PREFERABLY SAND

[0002] BRICK FROM GRANULAR MINERAL RAW MATERIAL

[0003] SUBJECT OF THE INVENTION

[0004] The subject of the invention is a process for producing building elements, preferably a brick, and particularly preferably a sand brick, from granular mineral raw materials, wherein the mineral raw material is preferably sand, and particularly preferably desert sand.

[0005] STATE OF THE ART

[0006] It is known that the construction industry uses reinforced concrete and fired ceramic brick in large quantities as basic building materials. It is also well known that the production of construction raw materials such as cement, steel and fired ceramic brick involves very high energy consumption and the emission of a significant amount of pollutant carbon dioxide gas.

[0007] The presently customary, conventional methods of brick manufacture are generally as follows.

[0008] Production begins with the extraction and preparation of clay, during which the clay is cleaned, made plastic and homogeneous; it is allowed to rest, then thinned by mixing in sand. Thereafter the wetted clay containing about 30 w / w% of water is formed mechanically, for example using a screw press. As a result of mechanized production, the prepared clay exits from the orifice of the screw press in the form of an endless strip. The green brick is cut to size from this using an appropriate cutting device.

[0009] Before firing, the green brick is dried. Modem drying is carried out in a closed room with artificial heat treatment and ventilation; the duration is 4-5 days. The alternative natural drying, which exploits the heat of the sun and the natural movement of air, can only be effective in dry, frost-free weather. With this method, drying takes two-three weeks, so its productivity is low.

[0010] After drying, the green brick is (kiln-)fired. This operation is the most important part of production. As a result of firing, the clay becomes a rock-like material that no longer softens in water and has mechanical characteristics suitable for use. The brick is generally fired in a ring kiln consisting of several chambers. The green ware is stacked with gaps in one empty chamber, and then the temperature is gradually increased and the firing is carried out at 950-1000 °C. After the product cools, the finished brick is carried out of the kiln. The above general basic operations can, however, be carried out in several ways.

[0011] The raw material of brick production is typically clay consisting of small fractions, which is mined in open pits using bucket or bucket excavators. Ensuring suitable product quality is only possible by using raw materials with a homogeneous mineral composition. Another aspect is that brick factories are built in locations chosen with a view to reducing transport costs and ensuring a reliable supply of mineral raw material.

[0012] Due to the high energy requirement and the unavoidable environmental pollution of brick production, technological changes are necessary, since energy consumption and environmental protection aspects are becoming increasingly important worldwide.

[0013] Attempts have long been underway to replace the raw materials of clay and concrete bricks.

[0014] Panels made of autoclaved aerated concrete produced with lightweight additives (e.g. expanded clay, tuff chippings) are known.

[0015] For those — usually large-size — paving slabs whose base layer is made of lightweight concrete and whose facing layer is made of pebbled or crushed stone concrete, or artificial stone, there is a risk that the slab will deform due to the differing degree of shrinkage of the two layers. The setting of the slabs can be accelerated by steaming, and the density can be increased by pressing. Concrete paving slabs are also made completely from gravel concrete, often with special additives (e.g. crushed stone), as well as with a facing part colored with cement paint.

[0016] A further alternative solution is sand-lime brick, which is a building material with a long tradition. It is inexpensive and excellent in its static properties; its compressive strength is higher than that of clay brick, however its thermal insulation capacity is significantly poorer than that of clay brick. Its raw materials are sand and lime, from which the masonry elements are produced by adding heat, pressure, water vapor or various chemicals. The main component of sand-lime brick is quartz sand, which is a natural raw material that is present in large quantities near the surface of the earth and thus its extraction results in moderate environmental impact. The further constituents of sand-lime brick are lime and water. During production, according to the formulas currently used, the measured materials are placed in a high-speed mixer. The purpose of mixing is to prepare a mixture with a homogeneous distribution, free of lumps, containing 5-7 % by weight of water. The fresh mixture goes into the reactor, where, during the aging time, the burnt lime grains are slaked and lime hydrate is formed. In addition to certain end-product properties that are less favorable for brick, the drawback of the solution is also that the proper quality raw material originating from quartz sand quarries may be exhausted within a foreseeable period given the current intensive mining, which may pose a significant challenge for the construction industry.

[0017] With regard to the sand required for the widespread production of sand bricks used in the construction industry, it should be noted that although there are vast expanses of sand deserts on the various continents, including, among others, in the Middle East and Southeast Asia, which in principle could provide locally available, usable construction raw material, nevertheless due to the quality characteristics of desert sand it is unsuitable for numerous construction purposes when applying most of the current technologies. For example, it is completely unsuitable for mixing concrete of adequate quality, because due to the constant wind and abrasion the surface of desert sand is extremely smooth, strongly abraded by the wind and practically has no adhering surface, as opposed to sand originating from rock debris, rich in sedimentary mineral material, which also has a much larger particle size.

[0018] In view of the above, it is apparent that the construction use of desert sand — even if the goal is not concrete production — necessitates the development of a special production technology.

[0019] To satisfy the above significant needs, numerous attempts have already been made to implement brick manufacturing techniques - based on various mined sands by using various synthetic resins - that essentially use bonding.

[0020] Thus, for example, patent application CN106348650A relates to a permeable brick, in which the problem of gaps between the eolian (wind-formed) desert sand grains is resolved by filling with an epoxy resin that also contains quartz powder, by controlling the drying time, thus the mechanical properties of the brick can be improved. The resin is cured at 20- 30 °C without applying pressure, essentially at room temperature, together with the drying itself.

[0021] Patent application CN105418139A relates to a sand-based permeable brick embedded in vinyl resin, which is made from the following raw materials: desert sand, potassium feldspar, quartz sand, sugar sludge, vinyl resin, ceramic fiber, coconut oil fatty acid diethanolamide, copper sulfate, black bamboo charcoal, sorghum straw and water.

[0022] Patent application CN106365512A relates to a polymer composite sand-based permeable brick that contains the following components: sand, shell powder, organic silicone- modified polyester resin or hydrogenated bisphenol A-type epoxy resin, cross-linking agent, oxidized pigment, lubricant, stones, cement, water-based epoxy resin, water and reducing agent.

[0023] Each of the above solutions is relatively complicated, since they necessitate the use of numerous additives in order to achieve the desired technical properties, and they do not relate specifically to masonry brick or bricks usable for multiple purposes, but typically to a product serving special purposes, such as a permeable brick.

[0024] In addition to the aforementioned types of synthetic resin, the use of acrylic resin is known from practice; however, together with the aforementioned polyvinyl resin, this is a very costly solution, so it is not advantageous for mass production purposes.

[0025] Furthermore, patent application EP2062863 Al relates to the production of sand brick using a plastic binder, where the binder used is polyol and / or isocyanate. A hot press is not used in the process, the product is cured by heat treatment in the mold, and the binders used are petroleum derivatives, which are not sufficiently environmentally friendly materials. There is no mention of the use of desert sand.

[0026] Finally, patent application JP2021134490 A, as well as the publications by Lahalih et al. (Construction and Building Materials 12.6-7 (1998): 321-328.) and by Gopal et al. (Indian Soc Desert Tech, Univ Cen of Des Stud Trans, 1983, 8.2.) describe the production of sand brick using desert sand and wet urea-formaldehyde resin; however, in the case of the articles, the compressive strength of the bricks is extremely low, and the results of the special process according to the patent are not directly comparable with the process according to the present invention. It is also an industry commonplace that the center of gravity of global construction is concentrated in tropical-subtropical areas, since, among others, these include the absolute world leader China (partly), India, Vietnam, the USA (partly), Turkey, Iran, Brazil and the Gulf countries. These areas are characterized by extraordinary heat, which is becoming increasingly extreme with global climate change, and in certain areas it is also coupled with high humidity. These environmental conditions are not favorable for the shelf life of the wet resins used in the above processes.

[0027] In view of the current state of the art, therefore, there is a gap for a process for producing a building element, preferably a brick, particularly preferably a sand brick, which is suitable for masonry purposes as well, and which allows the manufacture of the desired product using raw materials available in large quantities, in an economical, energy-saving and environmentally friendly manner, while ensuring the appropriate technical properties.

[0028] TECHNICAL PROBLEM TO BE SOLVED BY THE INVENTION

[0029] The objective of the invention is therefore to satisfy the existing needs referred to above by eliminating the disadvantages deriving from the state of the art.

[0030] On the basis of the available knowledge, we have come to the conclusion that the use of desert sand is most suitable for our purposes; however, the known technologies fell short of our objectives in terms of cost-effectiveness and / or the usability of the brick, so the development of a new technology became necessary.

[0031] BASIS OF THE INVENTION

[0032] Surprisingly, we found that if, in accordance with the solution according to the invention, we mix the resin with the sand in powder form, the compressive strength of the sand brick according to the invention is 24-28 N / mm2, whereas, under an otherwise comparable experimental protocol, the compressive strength of the bricks made with wet resin according to the state of the art is significantly lower, only 6-8 N / mm2. This is presumably due to the well-controlled and timed polymerization provided by the use of resin in powder form.

[0033] It was a further finding that the resin in powder form can be stored longer at the production site compared with the wet resin, which may polymerize spontaneously.

[0034] A further advantageous finding compared with the use of wet resin in the furniture industry was that, according to the present technology, the time spent in the hot press is reduced from 1 hour to 4-5 minutes.

[0035] Furthermore, overcoming a professional prejudice that is not explicitly refuted in the state of the art, we found that although wood and paper industry products bonded with ureaformaldehyde resin do not become water-resistant after bonding, they swell under the effect of moisture and, under the effect of larger amounts of moisture, they crumble as well, the sand bricks and other mentioned building elements produced with urea-formaldehyde resin adhesive nevertheless possess extremely good water resistance, since the sand grains and the other mineral materials used do not absorb water.

[0036] Surprisingly, in terms of frost resistance we also obtain a product of improved quality compared to fired ceramic bricks.

[0037] DESCRIPTION OF THE INVENTION

[0038] In the present application, the term “building element” is understood to mean any element used in the construction industry that can be produced from granular mineral material, thus without limitation including bricks and other block-like elements, where the elements can functionally be, without limitation, masonry elements, cladding elements, edging elements and structural elements as well.

[0039] In the present application, the term “granular mineral raw material” is preferably understood to mean sand, particularly preferably desert sand; however, any other granulated raw material suitable for use in the construction industry can be used for the process, in particular, but not exclusively: crushed stone, gravel, dolomite powder, limestone flour, brick grinding, slag, ash, glass cullet, basalt flour, perlite, zeolite, or mixtures thereof. In the present application, the term “dry-state urea-formaldehyde” is understood, in accordance with industrial standards, to mean urea-formaldehyde in powder packaging with a moisture content of at most 1%.

[0040] The process according to the invention for producing building elements, preferably bricks, particularly preferably sand bricks, from granular mineral raw material or mixtures thereof, comprises the following: the granular mineral raw material or mixtures thereof and, based on the mass of the granular mineral raw material or mixture, 5-20 w / w% of dry-state urea- formaldehyde are mixed together in a dry form; then an aqueous solution of a cross-linking catalyst initiating the polymerization, in a concentration of 3-40 w / w% (preferably 5-25 w / w%), is dosed into the mixture in such a way that the solution constitutes 1-10 w / w% (preferably 2-6 w / w%) of the mass of the intermediate to be produced, i.e. the remaining 90-99 w / w% is the mixture obtained in the previous step; the wet mixture is filled into a — preferably preheated — press mold, then pressed in a hot press at 60-150 °C (preferably at 60-120 °C) under a pressure of 0.5 MPa-20 MPa (preferably under a pressure of 2.5-5 MPa); and the product is removed from the press and left to stand until polymerization is fully completed.

[0041] According to a preferred embodiment of the invention, prior to the above process steps, the granular mineral raw material or mixtures thereof is homogenized before the actual use, where homogenization is preferably carried out by sieving to remove foreign materials present therein, such as wood, waste, etc., and elements larger than the desired size from the sand.

[0042] According to a further preferred embodiment, the product is actively cooled and / or actively dried following pressing.

[0043] According to a further preferred embodiment, further additives, for example colorants, are added to the mixture in the preparation-measuring steps.

[0044] According to a further preferred embodiment, sand, preferably desert sand, is used as the granular mineral raw material. According to a further preferred embodiment, phosphoric acid or ammonium hydroxide is used as the cross-linking catalyst for the urea-formaldehyde resin.

[0045] According to a further preferred embodiment, if the granular mineral raw material has a moisture content greater than 10%, then it is dried prior to use, preferably dried in the sun.

[0046] According to a further preferred embodiment, we cast bricks having geometric forms used in the construction industry, and / or we cast bricks having recesses, so that the individual elements can be joined together as a positive-negative pairs.

[0047] For the preparation of the cross-linking catalyst solution in the process according to the invention, (unpurified) fresh water or sea water can also be used. The use of sea water is particularly advantageous when brick production is carried out in countries where sea water is available in a natural form anyway, whereby logistic costs can be saved, and the saving of fresh water is also a non-negligible aspect.

[0048] The above is merely an exemplary listing of the possible solutions according to the invention; the declared scope of preferred embodiments also includes the intervals formed by combinations of the parameters according to the following specific embodiments.

[0049] Below, the findings and processes according to the invention are illustrated in the form of a few embodiments, without, however, limiting the scope to the examples.

[0050] EXAMPLES

[0051] Example 1

[0052] We mix 2300 g of desert sand prepared by sieving with 230 g of powder-state ureaformaldehyde resin. The mixing is carried out in any mixing machine used in the construction industry, but it can also be done by hand.

[0053] During mixing, we add 1 dl of a 25% strength ammonium hydroxide solution to the above mixture. The mixing is carried out until complete homogeneity is achieved, which is determined by visual inspection.

[0054] The mixed wet sand is filled into a preheated press mold (60 mm x 120 mm x 220 mm).

[0055] The temperature of the mold is 80 °C.

[0056] The sand in the mold is pressed with a likewise preheated cover plate.

[0057] The pressure is applied using a hydraulic press at a pressure of 5 MPa.

[0058] The brick is kept hot under pressure for 3 minutes.

[0059] The pressure is released and the brick is removed from the press mold.

[0060] At this point the brick is already dimensionally stable.

[0061] The hot bricks are unpacked onto the ground, where they cool in about half an hour.

[0062] After cooling, the brick can be installed immediately.

[0063] The compressive strength of the brick thus obtained is 24 N / mm2according to standard MSZ EN 772-1 :2011+Al:2015 (we used the same standard for the other compressive strength measurements described in the application).

[0064] Example 2

[0065] We mix 2200 g of dry desert sand with 320 g of powder-state urea-formaldehyde resin. The mixing is carried out in any mixing machine used in the construction industry, but it can also be done by hand.

[0066] During mixing, we add 1 dl of a 25% strength ammonium hydroxide solution to the above mixture.

[0067] The mixing is carried out until complete homogeneity is achieved, which is determined by visual inspection.

[0068] The mixed wet sand is filled into a preheated press mold (60 mm x 120 mm x 220 mm). The temperature of the mold is 70 °C.

[0069] The sand in the mold is pressed with a likewise preheated cover plate.

[0070] The pressure is applied using a hydraulic press, with a pressing force of 4 MPa.

[0071] The brick is kept hot under pressure for 3 minutes.

[0072] The pressure is released and the brick is removed from the press mold.

[0073] At this point the brick is already dimensionally stable.

[0074] The hot bricks are unpacked onto the ground, where they cool in about half an hour.

[0075] After cooling, the brick can be installed immediately.

[0076] The compressive strength of the brick thus obtained is 25 N / mm2.

[0077] Example 3

[0078] We use 3500 g of dry dolomite powder with a fraction having a diameter of at most 5 mm, and mix this with 500 g of powder-state urea-formaldehyde resin. The mixing is carried out in any mixing machine used in the construction industry, but it can also be done by hand.

[0079] During mixing, we add 2 dl of a 5% strength phosphoric acid solution to the above mixture.

[0080] The mixing is carried out until complete homogeneity is achieved, which is determined by visual inspection.

[0081] The mixed wet material is filled into a preheated press mold.

[0082] The dolomite powder in the mold is pressed with a likewise preheated cover plate.

[0083] The pressure is applied using a hydraulic press at a pressing force of 1.5 MPa.

[0084] The brick is kept hot under pressure for 3 minutes. The pressure is released and the brick is removed from the press mold.

[0085] At this point the brick is already dimensionally stable.

[0086] The hot bricks are unpacked onto the ground, where they cool in about half an hour.

[0087] After cooling, the bricks can be installed immediately.

[0088] Control Example 4

[0089] The process according to the invention described was developed relying on the results of numerous less successful experiments. From among these, a control experiment performed with wet resin is presented below as a control.

[0090] The use of wet resin used in the furniture industry raised several problems in the production of sand bricks. In the hot press we had to bake the mixture for nearly an hour for it to set. Moreover, the compressive strength of the bricks thus produced (6-8 N / mm2) was indeed greater than that of Ytong bricks considered one of the competitors (2-6 N / mm2), but it lagged far behind the compressive strength of fired clay bricks and concretes (15- 60 N / mm2). This limits the possible uses. For example, multi-storey buildings cannot be built from Ytong-type bricks because they collapse under their own weight.

[0091] The procedure with wet resin was carried out on the basis of Example 1 :

[0092] We mix 2300 g of desert sand prepared by sieving with 3.5 dl of wet urea-formaldehyde resin. The mixing is carried out in any mixing machine used in the construction industry, but it can also be done by hand.

[0093] During mixing, we add 1 dl of a 25% strength ammonium hydroxide solution to the above mixture.

[0094] The mixing is carried out until complete homogeneity is achieved, which is determined by visual inspection.

[0095] The mixed wet sand is filled into a preheated press mold (60 mm x 120 mm x 220 mm).

[0096] The temperature of the mold is 80 °C. The sand in the mold is pressed with a likewise preheated cover plate.

[0097] The pressure is applied using a hydraulic press at a pressure of 5 MPa.

[0098] The brick is kept hot under pressure for 30 minutes.

[0099] The pressure is released and the brick is removed from the press mold.

[0100] At this point the brick is already dimensionally stable.

[0101] The hot bricks are unpacked onto the ground, where they cool in about half an hour.

[0102] After cooling, the brick can be installed immediately.

[0103] The compressive strength of the brick thus obtained is 6-8 N / mm2

[0104] EVALUATION OF EXPERIMENTS AND APPLICABILITY OF THE INVENTION

[0105] If we wish to produce bricks of sizes differing from the above, we can change the dimensions of the press, the temperature and the pressing time accordingly to the size.

[0106] By using other starting granular grist and applying values selected from the previously given temperature and pressure intervals, we similarly obtain end-products having the desired properties, just as in the cases of the specific examples presented.

[0107] Regarding the shape of the bricks produced, we note that the technology provides an opportunity to produce almost arbitrary shapes as already referred to above. However, it is always preferred to remain within the bounds of reason and to produce bricks only as large as can still be easily handled by masons.

[0108] In the following, a tabular comparison is presented with respect to sand-lime brick, conventional (non-bonded) clay brick, and conventional (non-bonded) concrete brick products. Table 1: Manufacturing needs / prerequisites

[0109] Table 2: Applied raw materials Table 3: Product properties

[0110] Table 4: Manufacturing operations Table 5 below illustrates the application areas of sand brick, clay brick and concrete brick.

[0111] Table 5: Application areas

[0112] From a static point of view, a building with up to four storeys can be built from sand brick if it is built on itself without any auxiliary structure.

[0113] Sand brick is suitable for every function solved with clay brick, and for almost everything solved with concrete brick. An exception is the creation of walking surfaces, since, by virtue of its construction, sand brick wears and crumbles.

[0114] It is also important to note that when building a wall, the sand bricks can be joined / bonded with traditional mortar, but also with their own diluted adhesive.

[0115] The completed wall surface can be painted and can be treated almost identically as if it were made of fired brick and plaster. In addition, its workability is easy compared to the workability of a wall made of fired or concrete brick. According to our investigations, the energy demand of the hot press used in the brick production process according to the invention, referred to one brick, is about 10% of the energy used for firing in the firing process.

[0116] In terms of emissions, significant advantages of sand brick compared to traditional brick production are also apparent.

[0117] In the case of clay brick, the GHG (greenhouse gases — CO2 and other gases) emissions from the gas used in the firing kiln are very significant.

[0118] In the case of concrete brick, the GHG emissions from cement production are extremely polluting; the production of 1 ton of cement is associated with the emission of 927 kg of CO2, and, for example, in the Middle East on average 103 kWh of energy is used to produce 1 ton of cement.

[0119] Cement production contributes to greenhouse gases directly during combustion, when the thermal decomposition of calcium carbonate takes place, producing lime and carbon dioxide; furthermore, by burning fossil fuels. In 2016, the world cement production resulted in approximately 2.2 billion tons of CO2 emissions, which corresponds to 8% of the global total production.

[0120] Remaining with the example of the Middle East, in 2019 cement production resulted in a total of 24.4 million tons of CO2 emissions; in addition, the production of each ton of concrete produced was accompanied by a further 72.2 kg of CO2 GHG emissions.

[0121] The solution according to the invention entails numerous advantages that cover various aspects. First, the production of the brick can be carried out directly at the place of the given use where there is a need for it and where the appropriate raw material, namely sand, is available. A significant logistics cost advantage can also be achieved, since the transport costs are significantly lower, which makes the whole process more economical. Furthermore, it also offers advantages from an environmental point of view, since it is associated with lower greenhouse gas emissions, given that the solution does not require the establishment of a cement plant or a clay mine. Overall, the solution offers economic, environmental and practical advantages at the same time, so it can be widely applied.

[0122] Regarding the raw material, taking the most preferred embodiment of the invention, namely brick production from desert sand, the following advantages are apparent. The cost of extracting desert sand is a fraction of that required for clay mining and for the extraction of gravel / sand, since after collecting the sand with a loader and sieving, it is in a state ready for use. In contrast, in the case of clay brick production, the clay must be removed from the pit and transported.

[0123] Desert sand is not suitable for making concrete bricks.

[0124] Use of water: for preparing the base mass of clay brick and for making concrete brick, fresh water is needed, whereas for making sand brick sea water is also suitable. The amount of water required for production also differs; the amount of sea water required for sand brick is about 4-5 w / w%, whereas for clay brick 30 w / w%, and for concrete brick about 35 w / w% of drinking water is needed.

[0125] Production additives: in the production of the adhesive used for sand brick, the GHG emission is only -5% compared to cement.

[0126] Preparation of raw material: in the case of clay brick, many more operations are required, which mean more time and cost.

[0127] Drying: no drying operation is necessary in the case of sand brick — the producer saves time and cost, whereas in the case of clay brick this operation is 3-5 days.

[0128] Firing: sand brick does not need to be fired; it is produced by bonding.

[0129] Clay brick is fired at -1000 °C in a gas-fired kiln. This entails significant emissions and also represents a significant cost.

[0130] Resting: in the case of clay brick 1-2 days, in the case of concrete brick -5 days; in the case of sand brick it can be used after a technological waiting time of 1 hour.

[0131] Although sand brick is produced by hot pressing, which is part of the bonding and must be accomplished in the brick-form press, which is not necessary in the other two technologies; hot and pressing does indeed have an energy demand, but this is only a fraction of the energy demand required for firing clay brick.

Claims

AMENDED CLAIMS received by the International Bureau on 26 January 2026 (26.01.2026)1. Process for producing bricks, preferably sand bricks, from granular mineral raw material or mixtures thereof, characterized in that the process comprises the following steps:1) mixing together the granular mineral raw material or mixtures thereof and, based on the mass of the granular mineral raw material or mixture, 5-20 w / w% of dry-state urea-formaldehyde in a dry form;2) dosing to the mixture obtained in step 1) an aqueous solution of a crosslinking catalyst initiating polymerization with a concentration of 3-40 w / w%, such that the solution constitutes 1-10 w / w% of the mass of the intermediate to be produced (i.e. the remaining 90-99 w / w% is the mixture obtained in step 1));3) the wet mixture obtained in step 2) is filled into a — preferably preheated — press mold, then pressed in a hot press at a temperature of 60-150 °C under a pressure of 0.5 MPa-20 MPa; and4) the product is removed from the press and left to stand until the polymerization is fully completed.

2. The process according to claim 1 characterized in that at least one of the following is also applied: a) the granular mineral raw material or mixtures thereof is homogenized in a “0) step” before the actual use, where homogenization is preferably carried out by sieving; b) the product is actively cooled in step 4); c) the product is actively dried in step 4); d) the concentration of the cross-linking catalyst is 5-25 w / w% and / or constitutes 2-6 w / w% of the mass of the intermediate; and / or the pressing is carried out at 60-120 °C and / or under a pressure of 2.5-5 MPa; and / or e) further additives, for example colorants, are added to the mixture in step 1) and / or step 2).20AMENDED SHEET (ARTICLE 19)3. The process according to claim 2 characterized in that it mandatorily comprises all the steps defined in points a), b), c) and d).

4. The process according to any of the preceding claims characterized in that sand, preferably desert sand, is used as the granular mineral raw material.

5. The process according to any of the preceding claims characterized in that phosphoric acid is used as the cross-linking catalyst of the urea-formaldehyde resin.

6. The process according to any of the preceding claims characterized in that ammonium hydroxide is used as the cross-linking catalyst of the ureaformaldehyde resin.

7. The process according to any of the preceding claims characterized in that if the granular mineral raw material has a moisture content of more than 10%, then it is dried prior to use, preferably dried in the sun.

8. The process according to any of the preceding claims characterized in that the water used is unpurified fresh water or sea water.

9. The process according to any of the preceding claims characterized in that bricks with any geometric forms used in the construction industry are cast.

10. The process according to any of the preceding claims characterized in that bricks having interlocking projections and recesses are cast, so that the individual elements can be joined as a positive-negative pairs.21AMENDED SHEET (ARTICLE 19)

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