RU2255059C1 - Glass foam fabrication method - Google Patents

Abstract

FIELD: manufacture of building materials.

SUBSTANCE: invention relates to building materials with low values of heat conductivity and density. Fabrication of glass foam comprises heating powderlike blend with carbon-containing gasifier to foaming temperature, pausing at this temperature to complete foaming process, and subsequent cooling. Blend utilized is a cooled raw mix ground to powdered state, which is prepared via heat treatment of mixture of sodium and/or potassium silicate alkali aqueous solution and silicate-reactive additive, in particular fine broken glass powder and carbon-containing gasifier, at 450-550°C until removal of water, including chemically bound one, is completed. According to invention, content of sodium and/or potassium silicate alkali aqueous solution amounts to 30-70%, mixing is carried out at temperature not superior to 70°C, and foaming temperature of blend lies within a range of 750 to 830°C.

EFFECT: improved heat-engineering characteristics at low power consumption.

2 cl, 1 tbl

Description

The invention relates to the production of building materials with low values of thermal conductivity and density, in particular, to the production of block foam glass used as an effective heat-insulating material in various building structures.

The area in which foam glass is widely used is the production of heat and sound insulating materials. Thermal insulation made of foam glass in comparison with other building materials is more efficient and economical, has a longer service life.

The subject of most research in this technical field is to obtain a material with stable performance, low density, which provides good heat and sound insulation properties, water resistance and acid resistance.

Solid foams, the typical representative of which is foam glass, are formed as a result of the dispersion of the gaseous phase in a viscous liquid (dispersion medium) during the cooling of the dispersion system. As the temperature decreases, the viscous liquid hardens and the foam thus formed stabilizes. The foaming process is determined, first of all, by the temperature and nature of the ingredients that make up the raw mix to produce foam glass.

Foam glass can be obtained in many ways using compositions based on various glass. Two most effective methods can be cited as examples: the first is the production of foam glass from specially welded glass of the required composition; and the second - compositions based on a glass powder and a blowing agent of different composition, followed by foaming during the gradual heating of the entire sintered mass of glass. Glass powder is obtained either from specially welded glass masses (US 4192664, class C 03 В 19/08, 1980, US 3403990, class 65-22, 1968), or from the battle of window, container, optical and other glasses ( US 4198224, class C 03 B 19/08, 1980, RU 2132307, class C 03 C 11/00, 1999). Glass is usually used in powder form. For foaming the glass melt, gassing agents are introduced into the glass mixture in an amount of 1-5 wt.%. For foaming, a powdery mixture of glass and a blowing agent is poured into molds, which are placed in a furnace where, at a foaming temperature, the charge is heated and foamed. Then the foamglass molds are cooled and stabilized at a temperature below the foaming temperature. After completion of the heat treatment, the obtained foam glass blocks are removed. The disadvantages of the known technology are its high energy intensity associated with high temperatures of heat treatment, the duration of the operations to obtain glass of the desired composition, and a large foaming time.

Thus, a known method of producing foam glass by cooking glass in a controlled atmosphere at a temperature of 1350-1510 ° C, its preliminary heat treatment in the softening temperature range of 700-800 ° C and subsequent heat treatment at a foaming temperature. There are also known methods for producing foam glass based on the use of another technological operation - granulation of the finished glass melt and its subsequent grinding together with a blowing agent before secondary heat treatment (US 4192664, CL 65-22, 1980). Known methods require significant energy costs for the preparation of the mixture in the form of fine powders of glass and a blowing agent, their subsequent joint grinding and mixing for a long time to achieve the required uniformity of the distribution of components in the volume of the mixture, as well as technological operations for producing glass of the required composition.

Various attempts have been made in this field to produce high-quality foam glass with high thermal performance and low energy consumption.

So, from patent RU 1719333, cl. From 03 to 11/00, 1992, a method for producing foam glass is known, comprising preparing a powdery mixture of glass and a blowing agent, which is used as silicon carbide, which is treated with a saturated aqueous solution of alkali metal sulfate before mixing. The foaming of the mixture occurs during its heat treatment at a temperature of 850 ° C.

The analysis of literature data shows that foam glass production using specially welded and granular foam glass is widespread, and scarce and expensive ingredients are used to improve its properties (WO 00/61512, class C 03 С 11/00, С 03 В 19/08, 2000 g.). For a long time using the technology of producing foam glass from a powder mixture of finely ground glass and a blowing agent (US 3151966, CL 65-22, US 3403990, CL 65-22, 1968), which contains a reducing agent in the form of a carbon ingredient and an oxidizing agent from sulfates, oxides, etc. The use of known technology allows to obtain foam glass of a sufficiently high quality with a homogeneous structure, ensuring its operational stability, but the foam glass has a high cost due to the complexity of the operation of obtaining glass buoy structure.

From patent RU 2187473, cl. On 03/19/08, 2000, a method for producing block foam glass was known, including dispersing a recycled cullet and adding a foaming mixture containing silica, a carbon-containing component, metal sulfate and liquid sodium glass in an amount of 0.5-5.0 wt.%, sintering, foaming at a temperature of 790-860 ° C, hardening and annealing. The glass to be recycled is dispersed in a mill in the presence of an aqueous additive, resulting in the hydroxylation of the glass. A foaming agent is prepared by mixing silica, water glass, carbon black, sulfate and boric acid. Then the hydroxylated fine-ground glass powder is mixed with a foaming mixture in compliance with the required concentrations, achieving the greatest possible uniformity. The resulting mixture is subjected to granulation in the presence of water glass to improve the collection of material into granules. Metal forms are filled with granular material and sent to the furnace for sintering, foaming, annealing. To improve the granulation of the material, the mixture is moistened if liquid glass is introduced with dry powder. The known method allows to obtain foam glass with a structure of mainly or completely closed pores, having high thermal insulation properties, with a volumetric absorption of not more than 10%. Obtained by a known technology foam glass is characterized by high cost associated with the complexity of the mixture, the need for a long and fairly complex mechanical mixing of the components to a very uniform distribution of the foaming particles in the glass powder. Exceptional attention should be paid to the degree of dispersion of the grinding of glass, which is allowed to be performed only in mills of a certain type, for example, with ceramic or silicon linings and grinding bodies. Grinding in metal mills leads to contamination of the mixture with metal balls and lining, which further violates the conditions of pore formation in the sintered mixture. This in turn affects the stability, uniformity and reproducibility of the structure of the closed pores of the foam glass.

The closest in technical essence and the achieved result to this method is a method for producing foam glass, which includes heating the powder mixture to a foaming temperature, holding at this temperature until the foaming process is completed and subsequent cooling (US 4198224, class C 03 V 19/08, 1980 .). Foam glass manufactured by Pittsburgh Coming Corporation is made from fine glass powder and a blowing agent. The raw material mixture for the production of foam glass is prepared from glass to be recycled (the so-called cullet) and a blowing agent. The glass and blowing agent in the solid phase are carefully ground and mixed in a ball mill to an average grain size of 3-10 microns. In this case, the components are ground separately and in several stages: first, the glass is ground for 4-6 hours, then the blowing agent is ground for 6-8 hours, then the joint is ground for 4-5 hours. The mixing of the finely divided components of the raw material mixture is carried out in the solid phase. The resulting powdery mixture is then sintered in two stages at a temperature below the foaming temperature, and then cooled. The known method allows to obtain foam glass with a density of 0.17-0.25 g / cm ³ . Unfortunately, the known method is complicated by the fact that it is also associated with the energy-intensive and labor-intensive operation of glass melting of a special composition and grinding, while the mixing of the starting components is carried out in the solid state state, which does not ensure their high level of uniformity of distribution in the volume of the mixture. In addition, grinding in metal mills leads to contamination of the mixture with metal balls and lining, which, as mentioned above, further violates the conditions of pore formation at the stage of foam glass production. In addition, in the context of a sharp rise in energy prices, the use of the well-known powder mixture and the method for its production leads to a rise in the cost of foam glass. This requirement imposes restrictions on the choice of the composition to be foamed.

Within the framework of this application, the task of developing such a technology for producing foam glass is solved, which would make it possible to produce foam glass with high technological characteristics, but with low energy intensity of production. In addition, the problem of increasing the reproducibility of the structure of foam glass with a homogeneous finely porous structure containing closed pores is being solved. There is also a need to achieve a uniform distribution throughout the foam glass of small pores of a closed nature.

The problem is achieved in that in a method for producing foam glass, comprising heating a powdery mixture with a carbon-containing blowing agent to a foaming temperature, holding at this temperature until the foaming process is completed and subsequent cooling, the cooled raw material mixture obtained by heat treatment to heat is used as a mixture until a dehydrated state at a temperature of 450-550 ° C of a mixture of an aqueous alkaline solution of sodium silicate and / or potassium and powder chemically active additives in relation to silicate, the content of an aqueous solution of alkali metal silicate upon receipt of the raw material mixture is 30-70 wt.%, and the charge is heated to a foaming temperature from the range of 770-830 ° C. In addition, an aqueous alkaline solution of sodium silicate and / or potassium is mixed with additives at a temperature not exceeding 70 ° C.

It is advisable to use an aqueous solution of sodium silicate and / or potassium with a density of 1.3-1.5 g / cm ³ with a silicate modulus of 2-3.5.

The essence of the invention is to establish a causal relationship between the physicochemical properties of the foam glass and the initial composition of the raw material mixture, its sequential heat treatment with the initial stage of mixing the starting ingredients at a temperature not exceeding 70 ° C, cooling and grinding to obtain a powdery mixture and the foaming temperature of the mixture. In the absence of well-known regularities of the state of a substance after its processing at a foaming temperature and the initial composition of the charge, the authors experimentally found those optimal values of the content of an aqueous solution of alkali metal silicate at a processing temperature of 450-550 ° C, at which the required parameters of foam glass, which has a low cost of production, are provided . The most acceptable silicate module of an aqueous solution of alkali metal silicate is 2-3.5 with a solution density of 1.3-1.5 g / cm ³ .

In this method of producing foam glass, the mixing of the starting components is carried out not in the solid state, but in an aqueous solution of alkali metal silicate at a temperature not exceeding 70 ° C, which is a viscous fluid and is such a component that ensures both the uniformity of the distribution of powdered additives throughout the charge volume, and the occurrence of physico-chemical processes when heated to a temperature of 450-550 ° C, associated, including with dehydration of the mixture and the removal of chemically bound water. Stirring the initial components of the mixture in the liquid phase state without preheating the main component and additives allows us to obtain a structure of closed gas-filled pores uniform in volume of foam glass at a low energy intensity of production.

Example.

The invention is illustrated by the method of producing foam glass. As a glass-forming component, 120 kg of an aqueous alkaline solution of sodium silicate of potassium silicate (optimal ratio 1: 1) made from tripoli from the Tripoli autoclave or autoclaveless method of hydrothermal leaching of silica in an alkaline medium at a temperature of 90-100 ° C is used. An aqueous solution of alkali metal silicate is stirred at ambient temperature with additives in the form of fine ground cullet powder, taken in an amount of 60 kg for 10-15 minutes. While mixing the viscous flowing composition, 30 kg of a carbon-containing blowing agent are added to it. In the process of mixing the composition, free water and alkali are bound in liquid glass and adversely affect the water solubility of the final product, foam glass. An increase in the viscosity of the resulting composition indicates the occurrence of a physicochemical interaction of its components even at ambient temperature. The resulting mixture has a gray color. After mixing all the components of the raw material mixture, it is heat treated at a temperature of 480 ° C for 65 minutes. During heat treatment, further physicochemical processes occur, accompanied by the removal of free hydrated and chemically bound water and an increase in the viscosity of the mixture, after which it acquires a dark gray color. The weight of the raw material mixture cooled to ambient temperature is about 60% of the weight of the starting components. Then carry out grinding the mixture to a grain size of 15-20 microns. The crushed raw mixture is poured into metal molds treated with a special composition, and heat treated at a foaming temperature of 780 ° C for at least 90 minutes.

Table 1 shows the properties of the foam glass obtained using this technology, and table 2 shows the results in comparison with the FOAMGLASS foam glass manufactured by Pittsburgh Coming Eigore (Belgium).

Tab. 1

1. Density, kg / m ³ . from 100 up to 200 Maybe above 500 2. The compressive strength, MPa from 0,5 up to 5.0 3. The coefficient of thermal conductivity, W / m K 0, 048 ... 0.10 4. The volume fraction of closed pores,% 92-94 Gas-filled pores 5. Water absorption, when boiled for 90 minutes,% by volume 2-6 6. Hygroscopicity, wt.% (Holding for 24 hours in a desiccator at t ° C = 20 ° ^{(± 2)} at a relative humidity of 100%) 0.1 .... 0.2 7. Weight loss after boiling in water for 3 hours (water resistance),% (0.2 ... 0.4) 8. The coefficient of heat capacity, kJ / kgK 0.966-0.973 9. Operating temperature range for the use of products from this foam glass -60 - + 600 Scope standard for foam glass and potential opportunities 10. The coefficient of temperature linear expansion, and 10 ^-6 K ^-1 for the temperature range from 20 ° ... to 600 ° C 6.0-5.1

The invention can be used to obtain foam glass with a reproducible finely porous structure. The invention provides for the use of an aqueous solution of sodium silicate and / or potassium and chemically active additives to it, which make it possible to obtain, after mixing and heat treatment at a temperature of 450-550 ° C., a dehydrated composition suitable after grinding to produce foam glass with high thermal characteristics, but with low energy consumption production due to the exclusion of boiling glass with a special chemical composition at high temperatures.

Claims (2)

1. A method of producing foam glass, including heating the powder mixture with a carbon-containing blowing agent to a foaming temperature, holding it at this temperature until the foaming process is completed, and subsequent cooling, characterized in that the mixture is a powdered cooled powder mixture ground to a powder state obtained by heat treatment at a temperature 450-550 ° C until complete removal of water, including a chemically bound mixture of an aqueous alkaline solution of sodium silicate and / or potassium and chemical the active additive for the specified silicate — finely ground cullet powder and carbon-containing blowing agent, while the content of the aqueous alkaline solution of sodium silicate and / or potassium upon receipt of the mixture is 30-70 wt.%, mixing is carried out at a temperature not exceeding 70 ° C, and heating the charge is carried out to a foaming temperature from the range of 750-830 ° C. 2. The method according to claim 1, characterized in that an aqueous solution of sodium silicate and / or potassium with a density of 1.3-1.5 g / cm ³ with a silicate module of 2-3.5 is used.