DE2524981B2 - Process for the production of vitreous, porous moldings with the addition of binders - Google Patents

Description

60

The invention relates to a method for the production of glass-like, porous molded bodies made of glass, basalt and other silicate material, in which the starting materials are pulverized, mixed with a binder and finally heated ^{to 800 to 1000 ° C. for foaming.}

y = 100

20000

2F =

MF
100

when M is the molecular weight of the binder.

In the formula given above, 20,000 is the area Fm in m ² that the binder covers in a molecular layer (see, for example, BR B rdicka: "Fundamentals of physical chemistry", VEB-Verlag der Wissenschaften, Berlin 1969, pages 563/564 ). When calculating the area Fm covered by the binding agent in the molecular layer, it is assumed that the lower limit of the surface of a molecule is about 20 10 ^-16 cm ² . The surface of a mole is then 20 ■ 10- ^{| 6} / V if Λ / is Loschmidt's

Number 6.0244 · ΙΟ ²³ is ideal, gas-like surface films then have a surface area of around

20th

_{6th 10} 23 ₌ 120. to ⁷ cm ² .

Assuming that condensed surface films consist of cube-shaped crystals, which are packed close together, so that only one of its six faces contribute to the surface of the film, such a condensed surface film has a surface

F _M = 120 x 10 ^7/6 cm ² = 20,000 m ² .

In contrast to the prior art, the refractory binders used in the method according to the invention are used primarily not as a binder, but as a foaming agent. It has surprisingly been found that the surface activity of the refractory binders, if they are used in the specified amount, the Formation of uniform, closed cells of the glass foam promotes to a large extent and thereby the The creation of a foam glass causes the desired properties. has, without the Achieving this goal special, complicated or lengthy, energy-consuming process steps would be required.

In the production of foam glass, the refractory binders used in the method according to the invention are has not yet been used. Applications have apparently not been discovered because of this, because even in the temperature range of foam glass production, glass is generally used as a binder and flux and there appeared to be no use for an additional binder.

In the process according to the invention, surface compounds arise between the pulverized starting materials and the refractory binders adsorbed on their surface. Surface compounds have energetic peculiarities that are covered by the concept of surface energy σ (see, for example, H ed ν a 11: "Introduction to Solid Chemistry", Verlag Vieweg 1952, page 53). The surface energy σ is understood as the mechanical energy stored in the surface, which is greater in the finely divided state of the substance than in the compact state and is therefore able to create more new surfaces when foaming. The only thing that matters is the summary recording of the energetic peculiarities of the surface of the finely divided glass, measured in m ² / g, ie not the size of the individual particle, but the total surface. This results, for example, in the possibility of glass powder with a BET surface area of 0.5 m ² / g by adding a small amount in a particularly finely divided state, e.g. B. to produce a mixture with a high average surface energy with a BET surface area of 10 m ² / g and, by covering the entire surface with a monomolecular layer of the binder and after increasing the temperature until melting and foaming, a number of new areas corresponding to the larger surface energy create, ie to foam higher. A larger amount of the binder than is required for monomolecular coverage of the surface leads to an additional increase in the surface area of the films, ie to undesired larger bubbles or cells of the foam glass.

The relationship given above therefore specifies the maximum amount of binder in g per 100 g of starting material with the BET surface area F , which is required above all if a thin and hard base layer is to be produced on the surface of the molded body at the same time. This evidently arises from an accumulation of the binder on the surface of the molded body made of moistened masses during drying. The production of a hard layer on the surface of the shaped body is an essential part of the invention and is of considerable application-related importance in flat roof construction.

Instead of adding a small amount of glass powder in a particularly finely divided state, i. H. at Instead of the mechanical process to produce starting products with a high BET surface area, cheaper ones can be used chemical processes occur. These are described in application examples 6 and 7. In the Cover is condensed surface films with considerable cohesion. According to known Relationship, the surface pressure of condensed films is equal to the lowering of the surface tension.

The moist masses set with refractory binders are easy to shape and after shaping hardenable by heating to approx. 200 ° C. The hardener is of particular importance in that A solid layer which hinders the passage of gas is formed on the surface of the molded body later, during foaming, it favors vertical expansion. The special advantage of the Curing, however, lies in the easy handling of the cured panels due to their high green strength in saving molding boxes.

This now results in the following continuous process sequence: Mixing and grinding of the batch to the fineness given by the amount of binder with moistening the mass, filling the mass in the recipient of a press, whose material exit is the shape and cross-section of the exiting, endless Belt, which without interruption one after the other through drying, foaming and relaxation ovens to be led. As is known, in the powder process, the powders sinter to form sintered plates before foaming together that easily burst into pieces. This is not the case with the method according to the invention. The cured tape remains intact at the sintering temperature. The same mixtures can also be dry Can be processed according to the powder method, by means of dry blending and dry grinding getting produced. Depending on the surface of the ground material, they contain the same amount of binder as with the mass process in dry form.

The invention is explained in more detail below with the aid of examples.

example 1

100 g glass powder with additions of 6.12 g sodium metaphosphate (NaPO ₃ each, 0.36 g carbon black and 0.135 g iron sulfate FeSO ₄ · 2 H ₂ O are ground in the ball mill to a fineness of 1 m ² / g and with as much water The amount of 6.12 g of sodium hexametaphosphate is calculated using the relationship in column 2.

The solid plate is heated without a mold to about 880 ° C for foaming and 15 to 30 minutes at temperature held. This is followed by cooling down to approx. 500 ° C

Air and further slow cooling for relaxation in the relaxation oven.

Example 2

A mixture of 80 g glass powder and 20 g basalt dust with additions of 8.26 g (NaPO ₃ each, 1.2 g SiC (particle size 3 μm) and 0.135 g FeSO ₄ · 2 H ₂ O is reduced to a fineness of Ground 1.35 m ² / g BET surface area and treated further as in Example 1.

Example 3

15th

A mixture of 80 g glass powder and 20 g basalt dust with additions of 0.80 g boron phosphate, 4.60 g (NaPO ₃ J ₆ , 0.36 g carbon black and 0.135 g FeSO ₄ · 2 H ₂ O is reduced to a fineness of 1 , 5 m ² / g ground and treated further as in Example 1.

Example 4

25th

Mixtures as in Examples 1-3 with the corresponding fineness of the powder are with so much water added that they are easily malleable. They are filled into the recipient of an extrusion press, Shaped into an endless band of the desired plate cross-section and slow to dry through a continuous furnace at 200 ° C and then through a continuous furnace whose annealing zone is set to 880 bis 900 ° C is set, conducted. The product leaving the oven is cut into the desired lengths.

Example 5

Dry mixes corresponding to the subtleties and the compositions in Examples 1-3 are heated in metal molds to 88O ⁰ C and cooled in the expansion oven for a holding time of 15-30 minutes.

Example 6
A mix of

50% basalt flour with a fineness of 0-0.1 mm,

20% sodium metasilicate 5 hydrate,

7.5% H ₃ BO ₃ ,

22.5% water

45

50

is made in the ball mill. The water-soluble constituents are first dissolved and precipitated by reaction with one another to form very finely divided products with a large surface area, so that a surface area of about 20 m ² / g can be measured on the dried mixed product. The undried mixture is mixed in a kneader with enough glass powder (normal glass) with a surface area of 0.5 m ² / g that a malleable mass is produced which is further processed as in Example 4. The glass content of the mixture can be increased as desired with further addition of water and foaming agents, e.g. B. SiC with particle sizes of 0-3 μιτι, are added.

Example 7

The mixed product from the ball mill according to Example 6 can be dried, finely ground, with foaming agents added and heated to 800 ° C in a metal mold. This creates a fine cellular structure Foam product. The dry product can be mixed beforehand with any amount of glass powder.

In the context of the present invention, glass powder is preferably the comminuted product Normal glass, in particular from waste glass, is to be understood in the form of waste bottles in large quantities is available

Refractory binders are phosphate-based binders for refractory masses (ramming masses, molding masses, stones and refractory paints) which, without exception, are used in accordance with the present invention to produce monomolecular surface films on the surfaces of powdery raw materials, such as glass, basalt and other silicate material can. This also includes the solutions of primary metal phosphates, such as. B. the commonly used monoaluminum phosphate solution. Examples 1-7 can therefore be continued as desired using these binders. Refractory binders also include the water-soluble alkali metaphosphates and alkali metasilicates or their condensation products, as well as metaborates. H ₃ BO ₃ is also one of these substances, as it converts to metaborates in the mixtures and under the conditions of the processes carried out.

The summary recording of the energetic peculiarities of surfaces also includes Activation through grid disturbances in layer grids. This gives the opportunity to go through too Addition of activated substances with a layered grid. Powder mixtures with a higher average surface energy to produce a surface energy corresponding to the greater when the mixture is foamed Create number of new areas, d. H. to foam higher. The experiments have shown that the effects with Additions of mica and talcum flour are very large; additions of 1% are completely sufficient. By Heating these minerals to temperatures above 800 ° C creates a pile of two-dimensional crystals, because by expelling the crystal water the cohesion of the layers by von der Waalsche forces is no longer given. The minerals are only effective in this sense if their The crystal structure has not previously been destroyed by fine grinding. The mineral materials used with a layered grid had a particle size of 0.1 mm and more. The escaping crystal water also increases the Amount of inflating gases.

Example 8

A mixture of 85% glass flour and 15% basalt flour is mixed with 1 g each of boron phosphate, silicon carbide and talc. Silicon carbide has a particle size of 0-1 μm, talc had particle sizes which were 50% over 0.1 mm. The foam glass produced therefrom in the powder process had a density of 0.15 g / cm ³ .

The mixture was ground in a ball mill to a BET surface area of 1 m ² / g.

Claims (7)

Patent claims: 1. A process for the production of vitreous, porous moldings made of glass, basalt and other silicate material, in which the starting materials are pulverized, mixed with a binder and finally ^{heated to 800 to 1000 0} C for foaming, characterized in that refractory binders in The form of phosphates, silicates and / or borates are used and are used in an amount y in g per 100 g of starting material which is dependent on the BET surface area F of the starting materials given ^{in m 2 / g AndbisZU} M MF * = ¹⁰ ° 2Öörä ^2F = ΚΧΓ
when M is the molecular weight of the binder. 2. The method according to claim 1, characterized in that the mixture of silicate material and a refractory binder moistened with water, pressed into an endless strand and dried and cured in the strand first at temperatures of 20 to 600 "C and then at temperatures between 800 and 1000 ⁰ C is brought to foam. 3. The method according to claim 1, characterized in that the mixture of silicate Material and refractory binder dehydrated, finely ground and as a dry powder in molding boxes 800 to 1000 ° C is heated. 4. The method according to any one of the preceding claims, characterized in that in the Mixture of silicate material and refractory binder, the components dissolved in water before Dehydration to increase the surface area of the solid mixture by adding boric acid be precipitated. 5. The method according to claims 2 and 4, characterized in that the mixture according to the precipitation of the soluble constituents by adding glass powder to a malleable mass is processed. 6. The method according to claim 1, characterized in that a dry mixture of silicate material and refractory binder is produced and ground to the BET surface area dependent on the amount of refractory binder and is heated ^{to 800 to 1000 0 C as a dry powder in molding boxes.} 7. The method according to any one of the preceding claims, characterized in that the mixture to increase the BET surface area of the starting materials about 1% by weight layer minerals, ζ. B. mica, are added, which when heated in the temperature range of 600 to 800 ° C form a pile of two-dimensional crystals. Such methods are known in various forms. The binders used are Polyvinyl alcohol, water glass, quick lime and a "binder", among which are usually suitable for paints organic binders are understood. These binders have in the known processes exclusively the purpose of binding the powdery starting materials so far that a malleable mass arises This mass must either be pressed into molds for foaming, as is the case with a method known from "Glas-Email-Keramo-Technik", June 1964, page 221, is the case, or else is only used for the production of granules, as in "Glass-Enamel-Keramo-Technik", September 1968, page 313 and from the DT-OS 15 96 871 known method is the case with a using a Binder made, from DT-PS 9 13 579 known product is not foam glass in the current meaning of this term, namely to bodies with a volume weight in the order of magnitude from 0.1 to 0.2, but about a product of high density, that will serve as a grindstone. A method known from DT-OS 24 53 882 does not lead to production either from foam glass according to the current meaning of the term, but to a product, its density is in the range between 0.4 and 1.2. This high density is due to the use of dibasic Sodium or potassium phosphate are attributed because these secondary phosphates are a cell-destroying one and thus have a foaming-preventing effect. These substances are called in glass technology Opacifier and used as a nucleating agent for crystallization. The nucleation is but precisely about a process opposite to foaming. The invention is primarily not concerned with means that bind the powdery starting materials the production of foam glass, but rather with the problem of a foam glass produce low density, the closed cells in the entire volume as possible of the same size. Accordingly, the invention is based on the object of specifying a method of the type described above, which leads to a foam glass with uniform, closed cells and in a simple manner too is feasible on an industrial scale. The object is achieved according to the invention in that refractory binders in the form of phosphates, silicates and / or borates are used as binders and are used in an amount y in g per 100 g of starting material which depends on the BET surface area F of the starting materials given ^{in m 2} is dependent and up to