JP3089937B2 - Manufacturing method of foam ceramics - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing foamed ceramics, and more particularly, to a method for producing foamed ceramics which has little variation in product dimensions and excellent dimensional stability.

[0002]

2. Description of the Related Art Foamed ceramics are widely used as various building materials and the like by utilizing their excellent properties such as light weight and heat insulation.

[0003] Conventionally, foamed ceramics are produced by molding and firing a foamable ceramic material containing a gas generating agent such as silicon carbide, and foaming the gas generating agent in the firing process.

[0004]

By the way, ceramics shrink and become denser by firing. However, firing of foamed ceramics involves a process of densification due to firing shrinkage and expansion due to foaming of a gas generating agent. To become
Dimensional change due to shrinkage and dimensional change due to expansion
There is a disadvantage that the size of the obtained product varies greatly due to the two opposing dimensional changes.

[0005] It is an object of the present invention to solve the above-mentioned conventional problems and to provide a method for producing a foamed ceramic which has a small dimensional change during firing and is excellent in dimensional stability of a product obtained.

[0006]

According to the method for producing foamed ceramics of the present invention, a plurality of foamable raw material powders having different fire resistances are respectively granulated, and the granulated particles are dry-mixed and then molded. How to make foam ceramics for firing the body
A plurality of foamable raw material powders having different fire resistances.
Highest refractory high refractory foaming material and most refractory
Low low fire resistance The difference in fire resistance from the foaming raw material is 50 to 200.
° C.

Hereinafter, the present invention will be described in detail.

In the method of the present invention, first, a plurality of foaming materials having different fire resistances, for example, a high fire resistance foaming material having a relatively high fire resistance and a low fire resistance foaming material powder having a relatively low fire resistance are used. And granulating each.

In the present invention, as the high refractory foaming raw material, for example, those having the following composition can be used, and as the low refractory foaming raw material powder, such a high refractory foaming raw material can be used. On the other hand, it is possible to use the following composition in which a material that lowers the fire resistance, such as glass frit or natural glass, is further added in such a ratio as to obtain a predetermined fire resistance. In the following composition, as a gas generating agent, silicon carbide, silicon nitride, or the like can be used.

High refractory foaming raw material blending (parts by weight) Feldspar: 40 to 90 Clay: 10 to 60 Gas generating agent: 0.01 to 2 Low refractory foaming raw material powder blending (parts by weight) Glass frit: 0-50 Natural glass: 0-50 Feldspar: 40-90 Clay: 10-60 Gas generating agent: 0.01-2 Such high refractory foaming raw material and low refractory foaming raw material powder are respectively Granulate (hereinafter, granulated particles obtained from high refractory foamable raw material are referred to as “high refractory granulated material”, and granulated particles obtained from low refractory foamable raw material powder are referred to as “low refractory granulated material. ").)

[0011] Here, the high refractory granules and the low refractory granules cannot sufficiently reduce the dimensional change during firing according to the present invention, even if they are too small or too large. The particle size of the high refractory granules and the low refractory granules is 5 mm or less, especially 0.1 mm.
It is preferable to set it to 2 mm.

The obtained high refractory granules and low refractory granules are dry-mixed, press-formed, and then fired. Here, the mixing ratio of the high refractory granules and the low refractory granules is
At least one of the granulated particles is 10% by weight or more, that is, high refractory granules: low refractory granules = 10 to 9
0:90 to 10 (% by weight), preferably 30 to 70: 7
It is preferable to set it to 0 to 30 (% by weight).

The firing temperature varies depending on the fire resistance of the high refractory foaming raw material and the low refractory foaming raw material powder used, the mixing ratio thereof, the porosity of the target foamed ceramic, and the like. It is appropriately determined within the range of 1300 ° C.

In the above description, the case of using two types of foaming raw material powders of a high refractory foaming raw material and a low refractory foaming raw material has been described. It goes without saying that the above foamable raw material powder may be used. Also in this case, it is desirable to mix at least 10% by weight of each expandable raw material powder.

In the present invention, the suitable value of the difference in the fire resistance between the high-fired foamable raw material and the low-fired foamable raw material also depends on the mixing ratio and the number of types of the foamable raw material powder used. That is, the effect of reducing the dimensional change during firing according to the present invention, as described below, in the firing step, after the phase due to the low refractory granules first shrink, the phase due to the low refractory granules expands by foaming. At the beginning, the phase due to the high refractory granules starts to shrink, and the expansion of the phase due to the low refractory granules is offset by the contraction of the phase due to the high refractory granules, thereby reducing the overall dimensional change. It is in. Therefore, a high refractoriness foamable ingredient and low refractoriness of foaming material, so that such cancellation effect can be sufficiently obtained, it is important to adjust the difference or the mixing ratio of the refractoriness and thus in the present invention, the highest refractoriness high refractoriness foamable ingredient, and 50 to 200 ° C. the difference between the refractoriness of the lowest refractoriness low refractoriness foaming material powder
I do .

[0016]

[Function] A plurality of foamable raw materials having different fire resistances are granulated by dry mixing, and the resulting molded article is in a state where a plurality of phases having different fire resistances are dispersed and mixed. Become.

A phase formed of a high refractory granule obtained from a high refractory foaming raw material (hereinafter referred to as "high refractory phase").
And a phase formed of a low refractory granule obtained from a low refractory foaming raw material (hereinafter referred to as a “low refractory phase”) in a dispersed and mixed state. First, the low refractory phase starts to contract with the rise. Further, when the firing temperature is increased, the low refractory phase starts to expand due to foaming. At this time, the high refractory phase starts to contract and then expands due to foaming.

As described above, since the expansion of the low refractory phase is accompanied by the contraction of the high refractory phase, the overall dimensional change is reduced and the dimensional stability of the product is improved.

Since the dimensional change near the maximum temperature during the firing process is small, a product having a desired bulk specific gravity can be easily obtained by appropriately setting the firing temperature.

That is, at around the maximum temperature in the firing process, the contraction of the low refractory phase has already ended, and the expansion of the low refractory phase is small. On the other hand, the high refractory phase
The contraction is completed, and the expansion process is in progress. In this expansion process, the expansion in the low refractory phase is reduced, and the expansion is mainly performed only in the high refractory phase. Therefore, the overall expansion rate is small. Therefore, the change in the bulk specific gravity with respect to the temperature change becomes small, and the firing temperature can be easily set so that a product having a desired bulk specific gravity is obtained.

[0021]

The present invention will be described more specifically below with reference to examples and comparative examples.

Example 1 A high refractory foaming raw material powder I and a low refractory foaming raw material powder I having the following composition were granulated to a particle size of 0.5 to 1.5 mm. The difference in the fire resistance between the high-fired foamable raw material powder I and the low-fired foamable raw material powder I is 110 ° C.

High refractory foaming raw material powder blend I (% by weight) Feldspar: 75 Clay: 25 SiC: 0.08 Low refractory foaming raw material powder blend I (% by weight) Glass frit: 20 Natural glass: 30 Feldspar: 10 Clay: 40 SiC: 0.12 High refractory granules I and low refractory granules I obtained by granulation were mixed in a rocking mixer at a ratio of 1: 1 (weight ratio). After dry mixing, the mixture was press-molded.

The relationship between the firing temperature and the bulk specific gravity of the sintered body and the relationship between the firing temperature and the shrinkage ratio of the sintered body when the obtained molded body was fired were examined. It was shown to.

COMPARATIVE EXAMPLES 1 AND 2 In the same manner as in Example 1, except that only the high refractory foaming raw material powder I (Comparative Example 1) or the low refractory foaming raw material powder I alone (Comparative Example 2) was used. Go, the relationship between the firing temperature and the bulk specific gravity of the sintered body when firing the obtained molded body,
The relationship between the firing temperature and the shrinkage of the sintered body was examined, and the results are shown in FIGS.

The following is clear from FIGS.

That is, in Comparative Example 1 in which only the low refractory foaming raw material powder I was used, large shrinkage occurred at an early stage, the bulk specific gravity (or shrinkage) increased rapidly, and then the bulk specific gravity (or shrinkage) was increased by expansion. ) Decreases rapidly. Comparative Example 2 using only the high refractory foaming raw material powder I shows a large change in bulk specific gravity (or shrinkage) as in Comparative Example 1 only at a high firing temperature at which the shrinkage and expansion occur.

On the other hand, in Example 1 in which the high refractory granules and the low refractory granules were dry-mixed, the change in the bulk specific gravity (or shrinkage) during the shrinkage process was the same as in Comparative Example 1. , 2 are very small. Also, in the expansion process after contraction,
The change in bulk specific gravity (or shrinkage) is small (that is, the slope of the graph is small).

For this reason, calcination is completed at a predetermined bulk specific gravity (or shrinkage ratio) in the expansion process, and a product having a desired bulk specific gravity can be easily obtained. In Examples 1 and 2, it is difficult to finish firing at a predetermined bulk specific gravity, and it is not easy to obtain a product having a desired bulk specific gravity.)

Further, in Example 1, since the total dimensional change from contraction to expansion is significantly smaller than that in Comparative Example 1, variation in product dimensions can be reduced.

That is, for example, when obtaining a product having a bulk specific gravity of 1.25, in Comparative Examples 1 and 2, D ₁ and D _{2 in} FIG.
Although there is a large dimensional change corresponding to the bulk specific gravity change of Example ₃ , only a small dimensional change corresponding to the bulk specific gravity change of D3 occurs in Example 1.

Comparative Example 3 The firing was performed in the same manner as in Example 1 except that the high refractory foaming raw material powder I and the low refractory foaming raw material powder I were dry-mixed as they were. As a result, the change in the bulk specific gravity (difference between the maximum bulk specific gravity and the minimum bulk specific gravity) when firing at 1200 ° C. to obtain a product having a bulk specific gravity of 1.25 is about 0.65 in Example 1 (see FIG. 1). whereas was equivalent) to D _3, only in this comparative example as large as about 1.10, and simply dry mixing the high refractoriness of foaming material powder I and low refractoriness of foaming material powder I is present It was confirmed that the effects of the invention could not be obtained.

Example 2 High refractory foaming raw material powder II and low refractory foaming raw material powder
Using the following formulation as II, each particle size 0.5 ~
The granules having a size of 1.5 mm were dry-mixed with a high refractory granule II: low refractory granule II = 1: 1 (weight ratio) and press-molded. The difference in the fire resistance between the high-fired foamable raw material II and the low-fired foamable raw material powder II is 160 ° C.

High refractory foaming raw material blend II (wt%) feldspar: 50 clay Clay: 49.85 SiC: 0.15 Low refractory foaming raw material powder blend II (wt%) Natural glass: 50 feldspar: 20 clay: 29.85 SiC: 0.15 The obtained molded body was fired at 1250 ° C. and the bulk specific gravity was 1.25.
The change in the bulk specific gravity (difference between the maximum bulk specific gravity and the minimum bulk specific gravity) in the firing step when the product was obtained was obtained. The results are shown in Table 1.

Examples 3 to 6, Comparative Examples 4 to 6 The high refractory foaming raw material powders and low refractory foaming raw material powders shown in Table 1 were used in the formulations shown in Table 1, and were used in Example 1 or Comparative Example 1.
The molding was performed in the same manner as in Examples 1 to 3 and
When the product having the bulk specific gravity shown in Table 1 was obtained by firing at the temperature shown in Table 1, the change in the bulk specific gravity during the firing process (the difference between the maximum bulk specific gravity and the minimum bulk specific gravity) was determined. The results are shown in Table 1.

Table 1 shows Examples 1 and Comparative Examples 1 to 3.
In Table 1, the results obtained in the case of firing at the temperature shown in Table 1 to obtain a product having a bulk specific gravity of 1.25 are also shown.

[0037]

[Table 1]

From Table 1, it is clear that the method of the present invention greatly improves the dimensional stability of the product.

[0039]

As described in detail above, according to the method for producing foamed ceramics of the present invention, dimensional change due to shrinkage and expansion during firing is reduced, dimensional variation is small, and dimensional stability of the product is large. And a product having a desired bulk specific gravity can be easily and reliably obtained.

[Brief description of the drawings]

FIG. 1 is a graph showing the relationship between firing temperature and bulk specific gravity in Example 1, Comparative Examples 1 and 2.

FIG. 2 is a graph showing a relationship between a firing temperature and a shrinkage ratio in Example 1, Comparative Examples 1 and 2.

────────────────────────────────────────────────── ─── Continuation of front page (56) References JP-A-48-60714 (JP, A) JP-A-2-192478 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) C04B 38/00-38/02

Claims (2)

(57) [Claims] 1. A method for producing a foamed ceramic, comprising: granulating a plurality of foamable raw material powders having different degrees of fire resistance; dry-mixing the granulated particles; forming the mixture; and firing the formed body; The difference in fire resistance between the most refractory high refractory foamable raw material and the lowest refractory low refractory foamable raw material among a plurality of foamable raw material powders having different degrees is 50 to 200 ° C. Method for producing foamed ceramics. 2. The method according to claim 1, wherein the particle size of the granulated particles is 5 mm or less.