EP2074073A2

EP2074073A2 - Process for producing thermoformed goods

Info

Publication number: EP2074073A2
Application number: EP07827748A
Authority: EP
Inventors: Rossano Ragazzini
Original assignee: Ragazzini Rossano
Current assignee: Grinn Srl
Priority date: 2006-10-18
Filing date: 2007-10-04
Publication date: 2009-07-01
Also published as: WO2008047395A3; WO2008047395A2; ITFI20060251A1

Abstract

Process for producing thermoformed goods comprising the preparation of a mixture which is subsequently submitted to baking. The mixture comprises glass and/or glass slags, micro-crystalline or amorphous silica and metallic oxides, wherein at least 50% of the micro-crystalline or amorphous silica has a granulometry inferior to 100 μ.

Description

Process for producing thermoformed goods.

DESCRIPTION

The present invention relates to a process for producing thermoformed goods, especially by using recycled or recovery materials.

More particularly, a process according to the present invention comprises the step of mixing clay with not dangerous wastes for the production of goods particularly suitable for being used in the building industry.

Thanks to the present invention, it is possible to make mixtures having optimal plasticity and formability, providing, at the same time, a remarkable contribute to the environmental defence by reusing recycled materials. The features of the goods produced according to the present invention are programmable by adjusting the components percentage and by intervening on the process parameters, as further disclosed in the following. Moreover, a process according to the present invention can be carried out without using any special equipment or machinery and can be controlled even by not particularly qualified personnel. The ^" simplicity of the present process offers further advantages even in economical terms, as it implies a remarkable reduction of the costs of the thermoformed goods. Further economical benefits are connected with a more a reduced energy consumption with respect to the production of conventional ceramic materials.

These and other advantages and characteristics of the invention will be best understood by anyone skilled in the art thanks to the following description in conjunction which refers to possible ways to carry out the present process.

Seen in its essential structure, a process according to the present invention implies the preparation of a mixture containing glass or/and glass slags, micro-crystalline or amorphous silica and metallic oxides. The granulometry of at least 50% of the microcrystalline or amorphous silica is less than lOOμ.

In practice, it is advantageous to mix clay with non-dangerous special wastes.

The clay percentage can be comprised between 30% and

50% of the mixture weight.

The clay is advantageously raw cave clay, that is to say not submitted to a refining process, or waste clay derived from the purification or from the refining of cave clay.

For example, the following wastes can be mixed to the clay: glass slags derived from the recovery of precious metals submitted to flotation. From a physical point of view, this waste usually features a dust-like consistency and from a chemical point of view, since it consists of calcium silica-aluminates, it features a SiO₂ content comprised between 30 and 45%, a AI₂O3 content comprised between 10 and 40%, a B₂O₃ content comprised between 5 and 10%, a Fe₂θ₃ content comprised between 5 and 10%, a TiO₂ content comprised between 1 and 5%, a CaO content comprised between 15% and 30%, a ZrO2 content comprised between 4% and 8%, Pbo<0,2%,

Zn< 1%, sodium silicate equal to about 10%, and copper silicates and oxides comprised between

5% and 10%. For example, the percentage of this waste can vary between 30% and 80% of the mixture weight. wastes produced from fume treatment in the iron and steel industry which do not contain dangerous substances. From a physical point of view, this waste features an impalpable dust consistency and, from the chemical point of view, it features a significant iron (Fe) and iron oxide (Fe₂O₃) content. For example, the percentage of this waste can vary between 2 and 20% of the mixture weight. wastes consisting of abrasive materials produced during the sandblasting of metal products. From the physical point of view, this product features a micro-sandy consistency and, from the chemical point of view, it mainly consists of silica (SiO₂) with iron (Fe) and iron oxide (Fe₂O₃) traces or other alloy constituents removed during the sandblasting process. For example, the percentage of this waste can vary between 5 and 30% of the mixture weight. wastes consisting of sand and clay coming from physical treatments of non-metalliferous minerals (for example derived from gravel washing operations) . From the physical point of view, this waste features a muddy consistency and, from the chemical point of view, it mainly consists of clay. For example, the percentage of this waste can vary between 5 and 50% of the mixture weight. wastes consisting of milled grass or glass fibres derived from a differentiated waste collection. From the physical point of view, this waste features a dust or sand consistency and, from the chemical point of view, it mainly consists of 70-76% of silica (SiO₂), 1-4 % of alumina (AI₂O₃) , 1-4% of iron oxide (Fe₂O₃) , 10-18% of lime (CaO) , and 10-13% of sodium oxide (Na₂O). For example, the percentage of this waste can vary between 2 and 30% of the mixture weight. wastes consisting of calcium sulphate and silica derived from silver, gold and copper thermal metallurgy and other metals or alloys used for jewelling micro-fusions and for the production of mechanical micro-components. From the physical point of view, this waste features a dust or sand consistency and, from the chemical point of view, it mainly consists of 70-80% silica (SiO₂) and of 20-30 % calcium sulphate (CaSO₄) . For example, the percentage of this waste can vary between 2 and 20% of the mixture weight, scraps or residues derived from the production of pig iron or from cast iron refining in O. M. B converters used to produce steel. In this case, the waste features glass slags characteristics which, depending on their size, can be dividend into (1) foundry slags with a granular or sandy consistency, (2) blast furnace impalpable powder, (3) blast furnace impalpable mud, (4) steelworks slags, (5) steelworks muds. The wastes listed above have the following average composition: CaO between 35 and 45%, SiO₂ between 25 and 35%, Al₂O₃ between 10 and 15 %, MgO between 5 and 15 %; other oxides are present in much inferior quantities. This kind of waste is very similar to that of glass slags derived from the refining process of precious metals, but it is available in a much higher quantity. The use of blast furnace powder (1), of blast furnace mud

(3) and of steelworks muds (5) is particularly advantageous. For example, the percentage of this waste can vary between 50 and 60% of the mixture weight.

Moreover, it is possible to use the following additives : fusing additives, for example wastes consisting of powders and particulate of ferrous material derived from physical/mechanical surface treatments of metallic goods such as grinding, polishing and blasting. From the physical point of view, said waste features a dust or sand consistency and, from the chemical point of view, it mainly consists of iron (Fe) and of iron oxide (Fe₂O₃) . For example, the percentage of this waste can vary between 10% and 30 % of the mixture weight. - plasticizing additives: for example wastes consisting of fiber wastes and muds containing fibers, fillers and coating products originating from mechanical separation processes in the paper and cardboard production and processing. From the physical point of view, this waste features a palpable mud consistency and, from the chemical point of view, it mainly consists of cellulosic fibres (about 30%) and aluminium sulphate (about 10%). For example, the percentage of this waste can vary between 2 and 10% of the mixture weight. The mixture is particularly plastic, so it can be used for loading moulds in which it is possible to form products of various shapes and sizes. The humid good formed in the mould is then dried and baked, for example in natural gas-fed muffle furnaces or in tunnel furnaces like for common pottery. With respect to common pottery, however, depending on the mixture composition, the finished product may have a variable colour from a typical sandstone yellow colour to a grey colour and finally to a red colour, it is more resistant to atmospheric agents and, more generally speaking, to the action of external chemical agents, and it is also more resistant to mechanical stress even if it features an inferior density.

It is possible to use an extrusion or pour forming method, like in the production of conventional ceramic materials. The wastes are mixed with clay in predetermined doses in a conventional mixer according to the desired chemical-physical features of the finished product. Water is used in a variable quantity to make the mixture according to the desired plasticity degree. The thus obtained mixture is pressed or poured into the moulds or extruded. The formed product, not yet finished, is then submitted to a drying process or to a rapid drying up and subsequently furnace-baked. The thus produced goods can be armoured, that is to say provided with an armour, for example a reticular metallic armour, before being furnace-baked. It is also possible to provide a pigmentation step by diffusion using known oxides before carrying out the furnace-baking step.

During the furnace baking step, the sodium silicates present in the glass, that is to say in the glass slags mentioned above, react with the silica contained in the other wastes used for making the mixture and with the metal oxides so as to form complex silicates and to originate a vitrified compound which ensures the coherence of the final product, so that the latter has a great resistance to compression and bending. Other properties of the final product may depend on the granulometry of the silicates: for example, by using coarse grained silicates, it is possible to produce thermoformed goods exhibiting a good filtration capacity and a good thermal refractariety; by using fine grained silicates (with a granulometry inferior to lOOμ) it is possible to produce thermoformed goods exhibiting high mechanical properties.

The fibers, like for example the cellulose fibers present in the muds generated by the paper or glass fiber processing, act as plasticizers so as to enhance the formability of the mixture and to allow a remarkable reduction of the forming pressure. The same effect can be obtained using red muds which mainly consist of ferric and ferrous hydroxides. Moreover, the cellulose fibers and also the glass fibers, in relation to the presence of AI₂O₃ contained in it contribute to the porosity of the finished goods and to its thermal refractariety . The calcium sulphate increases the crude plasticity of the mixture. In the presence of silicates, above 1000 ° C, the calcium sulphate determines the formation of SO₃. This gas produces closed cavities and cells in the viscous material being baked, so that the finished product is lighter. To obtain the maximum formation of said cavities, the furnace baking step is carried out at a temperature between 1150⁰C and 1200° C.

Some examples of the mixture composition are listed below. Example 1 raw red clay or gravel washing slime: about 30%; glass slags : about 60%; paper fibers : about 5%; - micro-fusion calcium sulphate : about 5%.

The mixture is brought to 1000-1050° C in about 4 hours and kept at this temperature for about 1 hour and subsequently cooled. The cooling can be slow or rapid. A compact thermoformed good is obtained and it can be used for the fabrication of floor tiles, of roof tiles or wall structural elements. The finished product is externally similar to a sedimentary stone, it is practically waterproof and it features a compression resistance of about 1200 Kg/cm². Example 2 : raw red clay or gravel washing slime: about 15%; abrasive waste material derived from the sandblasting of metallic products: about 10%; abrasive waste material produced from the grinding, polishing or blasting of metallic products: about 10%; glass slags: about 55%. The mixture is brought to a temperature of 1000- 1050° C in about 6 hours and kept at this temperature for about 6 hours, then it is subsequently cooled. The cooling can be slow or rapid. A porous and thermally refractory product is obtained and it is externally similar to a sedimentary stone having a compression resistance of 800-1000 kg/cm². The compression resistance increases if using fine grained waste abrasive material. Example 3 raw red clay or gravel washing slime: about 30%; milled glass or glass fibers: about 10%; - micro-fusion calcium sulphate : about 20%; - glass slags derived from the recovery of precious metals : about 40%.

The mixture is brought to 1000⁰C in 1 hour, then to a temperature of 1100-1150° in 30 minutes, then the fused mass is submitted to air cooling. A product with a closed-cell alveolar structure is obtained. Example 4 glass slags derived from the recovery of precious metals: about 75%; - paper fibers: about 5%; micro-fusion calcium sulphate : about 20%. The mixture is brought to a temperature of 1000⁰C in 1 hour, then to a temperature of 1150-1200° C in 10- 20 minutes, then the fused mass is submitted to air cooling. A product with a closed-cell alveolar structure is so obtained. Example 5 blast furnace powder: about 50%; recovery glass powder: about 20; - quartz derived from the sandblasting of metallic materials: about 10%; gravel washing slime about 10%; paper fibers: about 10%.

The mixture is brought to a temperature of 900 ° C in 5-6 hours, then to a temperature of 1100 ° C in about 1 hour and then cooled by bringing it to 20 °C in 3 hours. The finished product features a yellow- brown colour, a mechanical compression resistance between 1000 and 1200 kg/cm², and it is resistant to chemical and atmospheric agents and thermally refractory.

Example 6

Steelworks muds: about 50%; - glass slags derived from the refining process of precious metals: about 30%; clay: about 10%; micro-fusion calcium sulphate: about 5%; paper fibres: about 5 %. The mixture is brought to a temperature of 900 ° C in 4 hours, then to a temperature of 1100° C in about 1 hour, then it is cooled by bringing it to 20° C in 3 hours. The finished product features a grey-green colour, a mechanical compression resistance between 1000 and 1200 kg/cm², it is very- resistant to chemical and atmospheric agents and is thermally refractory. Example 7 abrasive material derived from sandblasting of metallic products (granulometry comprised between 50 and lOOμ) : about 10%; paper mill mud: about 10%; glass slags: about 70%; abrasive material derived from the blasting process of metallic products: about 10%.

The mixture is brought to a temperature of 1050 ° C in about 6 hours and remains at a temperature of 1050 °C for 1 hour. A slow cooling process follows this step. During experimental tests carried out by the inventor, a sample repeatedly submitted to direct flame at a temperature of 1000 ° C, which has been reached in 10 seconds ( with a gradient of 100°C/sec) , has resisted without showing cracks or other macro-lesions and, at the end of the tests, it has showed only a 10% reduction of the compression resistance.

Example 8 coal ash or pozzuolana: about 20%; - abrasive material derived from sandblasting of metallic products (granulometry comprised between 50 and lOOμ) : about 30%; micro-fusion calcium sulphate: about 20%; glass slags or blast furnace powder or mud: about 30%.

The mixture is brought to a temperature of 1000° C in about 6-8 hours and remains at this temperature for two hours. A slow cooling process follows this step (about 10 hours) . The thus obtained thermoformed good is particularly compact and has a density comprised between 1.5 and 2.5 kg/cm³" Alternatively, the mixture is brought to a temperature of 1100° C in about 6-8 hours and remains at this temperature for 30-60 minutes. A slow cooling process follows this step (about 10 hours) . The product thus obtained exhibits a regular closed cells alveolar structure.

With a same thermal cycle, the dimensions of the cells can be increased using a greater amount of coal ash or pozzuolana and vice versa. Example 9 glass slags or blast furnace powder: about 25%; paper mud: about 5%; coal ash or pozzuolana: about 20%; - abrasive material derived from sandblasting of metallic products (granulometry comprised between 50 and lOOμ) : about 30%; micro-fusion calcium sulphate: about 20%. The mixture is brought to a temperature of 1000° C in about 6-8 hours and remains at this temperature for two hours. A slow cooling process follows this step (about 10 hours) . Alternatively, the mixture is brought to a temperature of 1100° C in about 6-8 hours and remains at this temperature for 30-60 minutes. A slow cooling process follows this step

(about 10 hours) .

Obviously, the heating times indicated above can vary in relation to the the mass and to the shape given to the products. Practically, all the execution details may vary in any equivalent way as far as the shape, dimensions, elements disposition, nature of the used materials are concerned, without nevertheless departing from the scope of the adopted solution idea and, thereby, remaining within the limits of the protection granted to the present patent.

Claims

1. Process for producing thermoformed goods comprising the preparation of a mixture which is subsequently submitted to baking, characterised in that said mixture comprises glass and/or glass slags, micro- crystalline or amorphous silica and metallic oxides, wherein at least 50% of the micro-crystalline or amorphous silica has a granulometry inferior to 100 μ.

2. Process according to claim 1 characterised in that said mixture comprises clay in a quantity comprised between 30% and 50% of the mixture weight.

3. Process according to claims 1 and 2 characterised in that the clay is raw cave clay.

4. Process according to claims 1 and 2 characterised in that the clay is waste clay derived from the purification or refining of cave clay.

5. Process according to claim 1 characterised in that said mixture comprises fusion glass slags derived from the recovery of precious metals submitted to flotation.

6. Process according to claim 5 characterised in that said fusion glass slags feature a SiO₂ content comprised between 30 and 45%, a AI₂O₃ content comprised between 10 and 40%, a B₂O₃ content comprised between 5 and 10%, a Fe₂O₃ content comprised between 5 and 10%, a TiO₂ content comprised between 1 and 5%, a CaO content comprised between 15% and 30%, a ZrO2 content comprised between 4% and 8%, Pbo<0,2%, Zn< 1%, sodium silicate equal to about 10%, and copper silicates and oxides comprised between 5% and 10%.

7. Process according to claim 5 characterised in that said fusion glass slags are in a quantity comprised between 30 and 80% in the mixture weight.

8. Process according to claim 1 characterised in that said mixture comprises wastes produced from fume treatment in steel and iron industry.

9. Process according to claim 8 characterised in that said wastes comprise iron (Fe) and ferric oxide (Fe₂O₃) .

10. Process according to claim 8 characterised in that said wastes are in a quantity comprised between 2 and 20 % of the mixture weight.

11. Process according to claim 1 characterised in that said mixture comprises wastes composed of waste abrasive material produced from the sandblasting of metallic products.

12. Process according to claim 11 characterised in that said wastes mainly consist of silica (SiO²) with iron (Fe) and ferric oxide (Fe₂Oa) traces or other alloy constituents removed during sandblasting.

13. Process according to claim 11 characterised in that said wastes are in a quantity comprised between 5 and 30% of the mixture weight.

14. Process according to claim 1 characterised in that said mixture comprises wastes composed of sand and clay wastes derived from the physical treatment of non-metalliferous metals and mainly consisting of clay.

15. Process according to claim 14 characterised in that said sand and clay wastes are in a quantity comprised between 5 and 50% of the mixture weight.

16. Process according to claim 1 characterised in that said mixture comprises milled glass or of glass fibers.

17. Process according to claim 16 characterised in that said wastes comprise 70-76% of silica (SiO₂) , 1-4 % of alumina (AI₂O₃) , 1-4% of iron oxide (Fe₂O₃), 10-18% of lime (CaO), and 10-13% of sodium oxide (Na₂O) .

18. Process according to claim 16 characterised in that said waste is in a quantity comprised between 2 and 30% of the mixture weight.

19. Process according to claim 1 characterised in that said mixture comprises wastes composed of gypsum and silica derived from silver, gold and copper thermal metallurgy and from other metals and alloys used for jewelry micro-fusions and for the production of mechanical micro-details.

20. Process according to claim 19 characterised in that said waste mainly comprises 70- 80% silica (SiO₂) and 20-30% gypsum (CaSO_41.

21. Process according to claim 19 characterised in that said waste is in a quantity comprised between 2 and 20% of the mixture weight.

22. Process according to claim 1 characterised in that said mixture comprises fusing additives.

23. Process according to claim 22 characterised in that said fusing additives ccomprises wastes composed of powders and particulate of ferrous material derived from physical / mechanical surface treatments of metallic products such as grinding, polishing and blasting.

24. Process according to claim 23 characterised in that said waste mainly consists of iron (Fe) and of ferric oxide (Fe₂O₃) .

25. Process according to claim 23 characterised in that said waste is in a quantity comprised between 10 and 30% of the mixture weight;

26. Process according to claim 1 characterised in that said mixture comprises plasticizing additives.

27. Process according to claim 26 characterised in that said plasticizing additives comprises fiber wastes and muds containing fibers, fillers and coating products generated by mechanical separation processes in the paper and cardboard production and processing.

28. process according to claim 27 characterised in that said wastes comprises of cellulosic fibers (about 30%) and aluminium sulphate (about 10%).

29. Process according to claim 27 characterised in that said wastes are in a quantity comprised between

2 and 10% in the mixture weight.

30. Process according to claim 1 characterised in that said mixture comprises wastes or residues derived from the production of blast furnace cast iron or from the cast iron refining in O.M.B process converters for the steel production.

31. Process according to claim 30 characterised in that said wastes or residues are foundry slags in granular or sandy format, impalpable blast furnace powder, impalpable blast furnace mud, steelworks slags, or steelworks muds.

32. Process according to claim 30 characterised in that said wastes or residues comprise CaO between 35 and 45%, SiO₂ between 25 and 35%, Al₂O₃ between 10 and 15%, MgO between 5 and 15%.

33. Process according to claim 30 characterised in that the percentage of said wastes or residues is comprised between 50 and 60 % in the mixture weight.