JPH0674155B2 - Manufacturing method of crystalline foam glass - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial field of application] The present invention relates to a foam glass used for a wall material, a ceiling material, a floor material, etc. of a building, particularly a crystalline material excellent in thermal shock resistance, mechanical strength and the like. It relates to a method for producing foam glass.

[Conventional technology and its problems]

Foam glass is extremely excellent in terms of non-combustibility, light weight, and heat insulation property, and is being used as a building material by utilizing its characteristics.On the other hand, it is insufficient in thermal shock resistance, mechanical strength, etc. Attempts have been made to crystallize in order to improve.

For example, in Japanese Examined Patent Publication No. Sho 38-26470, glass powder containing SiO ₂ , Li ₂ O, and P ₂ O ₅ as essential components is mixed with a foaming agent to heat-foam, and after cooling, reheat to crystallize. That
In JP-A-54-152011, a borosilicate glass powder is mixed with a foaming agent and foamed and crystallized by heat treatment. In JP-A-59-92944, soda-lime glass powder is added. It is disclosed that a compound such as Zr or Ti, an alkaline earth metal compound, and a foaming agent are mixed with, and the temperature is controlled to foam and crystallize.

In these publicly known examples, the former is one that precipitates Li ₂ O-SiO ₂ based crystals, and because of its low coefficient of thermal expansion, it shows excellent thermal shock resistance, but the raw material cost is high, and the crystals are precise and long-lasting. It requires a chemical treatment process, is inferior in production efficiency, and has a problem in productivity and economical efficiency when it is widely used as a building material.

The latter two are methods for precipitating cristobalite crystals on the most common and inexpensive soda-lime glass or borosilicate glass that is commonly used as heat-resistant glass, but cristobalite itself causes a significant volume change at a low temperature near 200 ° C. There is a dent transition, and it is easy to impair thermal shock resistance and mechanical strength.

Further, all of these known examples use glass powder as a starting material, but it is difficult to prepare a large amount of glass cullet having a uniform composition in mass-producing general-purpose building materials, or glass melted at a high temperature at once. It is not economically and efficiently advantageous to subject the above-mentioned material to heat treatment again for foam crystallization.

One of the objects of the present invention is different from these known examples, and the silica-lime-soda-based starting material and the foaming agent whose main material is an inexpensive natural material which is a raw material of soda-lime-based glass are directly vitrified by heat treatment. Another object of the present invention is to provide a method for producing crystalline glass in which needle-like crystals are precipitated and foamed.

On the other hand, in the production of conventional soda-lime plate glass and container glass, there is precipitation of crystals particularly called devitrification, which has been evaded as a defect that distorts the perspective image or causes local distortion, but in bubble glass, it is originally air. Since it has a light-scattering non-transparency due to bubbles, it does not cause an optical problem. In addition, if a large number of fine needle-shaped crystals are deposited and they are made to intersect with each other, the mechanical strength will increase, and it will not soften at a relatively low temperature like glass, and will also have heat resistance. Can be improved.

That is, another object of the present invention is to provide a method for producing a crystalline foam glass in which a large number of needle-like crystals are precipitated to increase mechanical strength and heat resistance.

[Means for solving problems]

The present invention is a method for producing a soda-lime-based crystalline foam glass containing needle-like crystals in an amount of 20 vol% or more of the total solid phase, with a ratio of 50 / SiO ₂
Forming a powder mixture or mixed sludge consisting of a silica-based raw material whose wt% is crystalline silica, a lime-based raw material, a soda-based raw material and a foaming agent, and heating the molded body above the melting temperature of the soda-based raw material. Step, heating and maintaining at an appropriate temperature in the temperature range of the temperature above or below the liquidus temperature, foaming, and consisting of a step of precipitating acicular crystals, the acicular crystals Na ₂ CaSi ₃ O ₈ , devitrite or It consists of one or more types of wollastonite.

In the present invention, as the silica-based raw material, use is made of one containing at least 50 wt% of crystalline silica such as quartz and tridymite (hereinafter, simply referred to as% when the weight% is represented), and as the lime-based raw material, slaked lime, limestone and other calcium compounds are included. What is used, or used together with those containing an alkaline earth metal compound, and further used as a soda-based raw material containing sodium compounds such as sodium carbonate, caustic soda, or together with those containing potassium or lithium compounds Good.

If crystalline silica is not used as the silica-based raw material and glass is used, for example, reheating of needle-shaped crystals of Na ₂ CaSi ₃ O ₈ , devitrite, wollastonite, etc. requires extremely long heat treatment, and thermal shock resistance It is easy to deposit cristobalite, which adversely affects the sex.

On the other hand, by using a large amount of crystal such as quartz as the silica-based raw material, a portion of the silica-based raw material first reacts with most of the alkali-based raw material and part of the lime-based raw material in the heating process to generate Na rich in alkali. ₂ O-CaO-SiO ₂ to form a melt, foamed by the reaction of the melt and a foaming agent, further the melt and unreacted silica-based raw material, lime-based raw material to react with the needle crystals To facilitate the generation of. It is necessary to contain 50% or more of crystalline silica.

Examples of these silica-based raw materials include silica sand, silica stone, silica rock, and volcanic ash and tuff containing a relatively large amount of silica particles such as quartz.

In order for the silica-based raw material, particularly crystalline silica, to react rapidly with lime and soda-based flux, it is preferable to make the particle size smaller, and preferably 270 mesh or less.

Known foaming agents are CaSO ₄ , Na ₂ SO ₄ , CaCO ₃ , MgCO ₃ , As ₂ O ₃ ,
Sb ₂ O ₃ etc. can be adopted. Although Na ₂ CO ₃ most CO ₂ during disassembly deviates out of the system, some of which contribute to the residual Taawa of.
The amount of the foaming agent is appropriately determined according to the desired bulk specific gravity.

In the present invention, the composition range of SiO ₂ 65-80%, CaO 7-20%,
By setting Na ₂ O 10 to 20%, heat treatment is easy,
It has many advantages such as exhibiting an appropriate viscosity in the foaming process, easily obtaining a uniform and stable foam, and smooth recrystallization of needle-shaped crystals. Na ₂ C in the component system
In the crystallized region of aSi ₃ O ₈ , devitrite, wollastonite and cristobalite (silica). Of these, cristobalite does not form acicular crystals, undergoes an abnormal volume change due to transition at a relatively low temperature, and is inferior in thermal shock resistance and mechanical strength, which is not preferable, but according to the present invention, crystallization thereof can be suppressed.

If the SiO ₂ content is less than 65%, the bubble diameter is not uniform and coarse bubbles are likely to be formed, and it is difficult to precipitate fine and uniform needle crystals, that is, Na ₂ CaSi ₃ O ₈ , devitrite, wollastonite, etc. Excessive amount will result in insufficient heat resistance and weather resistance. On the other hand, if it exceeds 80%, the amount of the SiO ₂ —Na ₂ O—CaO effective melt produced in the melting process is too small, so that the formation of the needle crystals becomes insufficient.

If the content of Na ₂ O is less than 10% or the content of CaO is less than 7%, the formation of the needle-shaped crystals becomes insufficient because the content of Na ₂ O or CaO is too small. On the other hand, if the content of Na ₂ O or CaO exceeds 20%, the fine particles become fine. In addition, it is difficult to uniformly deposit needle-like crystals, and the bubble diameter tends to be nonuniform and coarse.

Al ₂ O ₃ in the range of 4% or less relative to SiO ₂ and CaO
Even if one or more of MgO, SrO or BaO is replaced with 1/3 or less and 6% or less and one or more of K ₂ O or Li ₂ O is replaced with 4% or less of Na ₂ O by substitution. It doesn't matter. B ₂ O ₃ is 5%
Addition and introduction within the following range has no effect on the crystal precipitation system.

The inclusion of about 0.5 to 0.6% of Fe ₂ O ₃ , MnO ₂ , TiO _2, etc. as impurities is not affected at all.

As an example of a more preferable composition range in the present invention, SiO ₂
68-75%, Al ₂ O ₃ 0-3%, CaO 8-15%, MgO 0-5%, Na
₂ O 10 to 15% and K ₂ O 0 to 3%.

It should be noted that even if a known nucleating agent such as ZrO ₂ or TiO ₂ is introduced in the order of several%, cristobalite is likely to be generated, which is not preferable.

On the other hand, crystallization of wollastonite or devitrite tends to be promoted by dispersing and mixing wollastonite having a particle size of several μm to several tens μm in an amount of 0.2 to 0.3% to several% with respect to the raw material.

The above-mentioned raw materials are mixed and then molded by a known compression, extrusion or cast molding method. Generally, when using sodium carbonate as a soda-based raw material, dry compression molding is preferable, while, for example, when water-added sludge is cast-molded, cohesive sticking of sodium carbonate or separation non-uniformity with the siliceous raw material occurs. easy. Further, when using caustic soda, it is preferable to carry out sludge casting molding. On the other hand, in the case of dry molding, for example, the molded body tends to collapse in the heating process after molding.

In dry compression molding, it is basically necessary to press so that the sample does not collapse during handling after molding, but at 20 kg / cm ² or more in order to close the contact between the raw materials and improve the reactivity. It is good to pressurize.

The raw material after molding is subjected to heat treatment. Almost all of the soda-based raw materials and some of the lime-based raw materials undergo decomposition and melting at approximately 700 ° C to 850 ° C, reacting with some crystalline silica and are rich in alkali content Na ₂ O-CaO-SiO ₂ Form a melt. The decomposition and melt formation reactions are remarkable at 850 ° C.

Further, by maintaining the temperature above the decomposition melting temperature to below the liquidus temperature, foaming occurs, and needle-like crystals are generated by the reaction of the melt with the unreacted silica raw material and lime-based raw material. It should be noted that maintaining the temperature above the liquidus temperature is not preferable because even if crystals are temporarily deposited, they disappear and it becomes difficult to maintain the shape of the molded body. The liquidus temperature can be confirmed from the known phase diagram,
Alternatively, a liquid phase temperature may be measured by preparing a sample of the component system in advance and using a known measurement method.

In this component system, the temperature is about 1100 ° C or lower.

The crystal phase increases by maintaining the foaming and crystal precipitation temperature, but it is difficult to obtain sufficient thermal shock resistance and mechanical strength unless the crystal phase in the solid phase is 20 vol% or more.

In addition to the precipitated crystal phase, a glass phase and residual quartz are recognized. Residual quartz is preferable in that it does not have an abnormal volume change such as cristobalite, which is the same silica phase, and is stable to heat.

〔Example〕

Particle size containing about 90% quartz and about 10% feldspar as silica-based raw materials
Silica sand of 80-100 mesh, 200-270 mesh, 270 mesh or less and 325 mesh or less was used.

Powder of slaked lime [Ca (OH) ₂ ] (particle size 27
(0 mesh) was used as a soda-based raw material powder of commercially available sodium carbonate (Na ₂ CO ₃ ).

Commercially available calcium sulfate (CaSO ₄ , 2H ₂ O) and calcium carbonate (CaC) for foaming and as a lime source.
O ₃ ) was used in the range of 5% or less in total in terms of CaO.

Mixing these raw materials, the oxide composition was SiO ₂ 71.3%, Al ₂ O ₃ 1.4
%, CaO 12.7%, Na ₂ O 12.8%, K ₂ O 0.8%. As impurities from the raw materials, some Fe ₂ O ₃ , T
iO ₂ and SO ₃ are expected to remain.

These were filled in a square press die and pressed under a pressure of 50 kg / cm ³ for 1 minute to prepare a molded sample.

The sample is placed in a resistance heating electric furnace and heated relatively quickly to 600 ° C, held at that temperature for 10 minutes to evenly heat the surface of the sample, and then heated at a rate of 10 ° C / min to 800 ° C. ~ 1100
The temperature was maintained at a predetermined temperature between 0 ° C. for a predetermined time and gradually cooled.

The following measurements were performed on the obtained sample.

Specific gravity measurement: According to a known measurement method using a specific gravity bin.

Crystal identification; mainly by X-ray diffraction and observation under a mirror,
EPMA analysis was used together.

Measurement of the amount of crystals (volume ratio) in the solid phase: The crystal phase area ratio was measured under a mirror for a plurality of arbitrary cut surfaces of a plurality of samples and averaged to calculate the volume ratio.

Thermal shock test (quick heating and quenching test): A sample piece was placed in an electric furnace maintained at a predetermined temperature, and after 10 minutes, it was taken out and visually inspected for damage. Of these, the upper limit temperature at which no damage occurred was defined as the rapid heat endurance temperature.

Then, it was put into water at 10 ° C. and rapidly cooled, and it was not damaged by rapid heating, and the upper limit of the rapid heating temperature at which cracks did not occur even by rapid cooling from the rapid heating temperature was defined as the rapid heating and quenching durable temperature.

In yet another raw material configuration example, a 50% silica sand of other 50% of SiO ₂ minutes as the silica source is supplied from the Pyrex glass powder _{(SiO 2 82%, B 2} O 3 11%), the other is the same lime , Soda raw material was used for mixing, press molding and heat treatment, and the same measurement was performed. In this case, B _{2 in the} foam glass
O ₃ is contained at about 4%, and SiO ₂ is mainly reduced by that amount.

On the other hand, as a comparative example, a volcanic glass refined product (Si containing 40% of silica in the silica content and a glass phase and some pyroxene) (Si
O ₂ 82%, Al ₂ O ₃ 12%, Fe ₂ O ₃ 0.7%, CaO 0.9%, MgO 0.4
%, Na ₂ O 1%, K ₂ O 2% (Ig loss 1%)) were similarly prepared as raw materials, molded, heat treated, and subjected to measurement. In the foam glass
Al ₂ O ₃ is contained in about 9%, and SiO ₂ mainly decreases by that amount.

Further, a plate glass cullet mixed with calcium carbonate (0.5% in terms of CaO) as a foaming agent and treated in the same manner was also subjected to the measurement.

As shown in Table 1, the results obtained using silica sand or silica sand with 50% quartz + Pyrex glass as the silica source were 850 ° C or higher (sodium carbonate dissolution, reaction temperature or higher), 110
By heat-treating and maintaining below 0 ° C (below liquidus temperature), it expands and expands to a bulk specific gravity of 1.6 or less, and needle-like crystals of Na ₂ CaSi ₃ O ₈ , devitrite or wollastonite precipitate at least 20 vol% in the solid phase. is doing. Example 10 is wollastonite (325 mesh or less) and 1% in the raw material in advance.
It can be seen that worstonite is precipitated in a larger amount as compared with Example 7, in the case of mixed and dispersed.

Comparative Example 1 is a temperature at which sodium carbonate cannot sufficiently dissolve and react, and Comparative Example 2 is a heat treatment at a liquidus temperature or higher.
The former indicates insufficient crystal formation, and the latter indicates vitrification and softening.

In the crystallized plate glass cullet system of Comparative Example 5 (heat treatment for 2 hours), devitrite and wollastonite were precipitated, but the amount thereof was a little less than% order and the thermal shock effect was obvious even in the rapid heat test. Not shown. Although not shown, the crystal content of devitrite, wollastonite, and cristobalite is less than 20% even after heat treatment for another day and night, and it is brittle against thermal shock due to the precipitation of cristobalite.

These examples show excellent rapid thermal quenching resistance (700 ° C. or higher) as is clear when compared with Comparative Examples 1, 3 and 4, but when the broken portion is observed, for example, the flat glass cullet system of Comparative Example 3 is observed. Has a shell-like fracture surface peculiar to glass, whereas the Example has a severely uneven fracture surface with needle-shaped crystals inset, and it is presumed that it has a function of connecting and locking glass. . Comparative Example 4 The one using a volcanic vitreous substance having a quartz content of 40% formed a viscous liquid containing a large amount of alumina during heat treatment, and it was difficult for crystals to precipitate.
Nepheline and wollastonite are found, but they do not show obvious thermal shock resistance.

Further, when the bending strength of the samples of Examples 5 and 7 and Comparative Example 3 was measured, the latter Comparative Example was 90 kg / cm ² , whereas the former two Examples were 170,200 kg / cm ^{2 respectively} . It has been clear that the crystal phase has also been effective in improving the mechanical strength.

[Effects of the Invention] According to the present invention, by heat treatment at a relatively low temperature for a short time,
Efficient and low cost, a crystalline foam glass containing a large amount of needle-like crystals can be produced from a non-glass-based raw material, and the crystalline foam glass is excellent in thermal shock resistance, mechanical strength and the like.

Claims (2)

[Claims] 1. A method for producing a soda-lime crystalline foam glass containing needle-shaped crystals in an amount of 20 vol% or more of the total solid phase, a silica-based raw material in which 50 wt% or more of SiO ₂ content is crystalline silica, a lime-based raw material, Forming a powder mixture or mixed sludge comprising a soda-based raw material and a foaming agent, heating the formed body to a temperature above the melting temperature of the soda-based raw material, to an appropriate temperature in the temperature range above or below the liquidus temperature. A process for producing crystalline foam glass, which comprises the steps of maintaining heating, foaming, and precipitating acicular crystals. 2. The method for producing a crystalline foam glass according to claim 1, wherein the acicular crystals are one or more of Na ₂ CaSi ₃ O ₈ , devitrite and wollastonite.