JPH04305046A - Calcium silicate sintered body and production thereof - Google Patents

Abstract

PURPOSE:To enhance resistance to thermal shock properties by incorporating lithium-aluminosilicate and wollastonite and sintering the molded body of this blended material so that it is regulated to the prescribed thermal expansion coefficient. CONSTITUTION:Li2O, Al2O3 and SiO2 are blended to obtain lithium- aluminosilicate (LAS) which has -120X10<-7>-+20X10<-7> (/ deg.C) thermal expansion coefficient and 1-100mum particle diameter and consists of at least one kind of aucryptite, spodumene and petalite. Then calcium silicate crystal is obtained by blending at least one kind of tobermorite, xonotlite and wollastonite. Furthermore 80-5wt.% LAS is blended and mixed with 20-95wt.% calcium silicate crystal. A molded body is obtained by molding this mixture. Then this molded body is burned at 900-1300 deg.C to produce calcium silicate sintered body having -65X10<-7>-+65X10<-7> thermal expansion coefficient.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a calcium silicate sintered body and a method for producing the same. In particular, the present invention relates to a calcium silicate sintered body that has excellent thermal shock resistance, low thermal expansion, and high strength without impairing mechanical properties such as bending strength or machinability, and a method for producing the same.

0002

[Prior Art] Calcium silicate materials have excellent nonflammability, fire resistance, heat retention, processability, etc., and are relatively inexpensive, and are already widely used in building materials and many other industrial materials. There is. However, the current situation is that calcium silicate-based materials have not yet reached the stage where they are put to advanced use in fields other than building materials.

That is, the main uses of conventional calcium silicate materials are calcium silicate boards, piles, fireproof coatings,
It is a heat insulating material, etc., and its various properties have not been improved until it can be used for advanced applications with higher added value.

Under these circumstances, the inventor of the present application has created a high-strength sintered body by giving bulk specific gravity to a calcium silicate-based material and firing it at a high temperature, and has created a high-strength sintered body while maintaining its workability. As a result, this sintered body can be applied to molds for hot forming, allowing for advanced utilization of calcium silicate sintered bodies that was previously unimaginable. We developed this technology and have already proposed it as Japanese Patent Application Laid-Open No. 1-164767.

[0005] Calcium silicate sintered bodies certainly have excellent heat insulating properties, but they have poor thermal shock resistance, and if this is improved, it is a material that is expected to have even more applications. JP-A No. 62-143855 has already proposed an attempt to improve the thermal shock resistance of calcium silicate-based materials, but this proposal is only intended for molded building materials, and moreover, There is no evidence that the thermal shock resistance of a calcium silicate sintered body having high strength is improved.

[0006]

The present invention provides a calcium silicate sintered body that has significantly improved thermal shock resistance, low thermal expansion, and low thermal expansion properties without impairing mechanical properties such as strength or workability. The purpose is to obtain a high-strength sintered body.

[0007]

[Means for Solving the Problems] This invention provides lithium-
It consists of aluminosilicate and wollastonite, and the content of lithium-aluminosilicate is 5 to 80% by weight,
and its thermal expansion coefficient is -120 x 10-7 to +20 x 1
0-7 (/℃), and the particle size is 1 to 100 μm, and the coefficient of thermal expansion of the sintered body is -65×10-7 to +65×
10-7 (claim 1), 20 to 95% by weight of calcium silicate crystals consisting of at least one of tobermorite, xonotrite, and wollastonite, and eucryptite. ,
Calcium silicate, characterized in that a molded body is formed from a mixture of 80 to 5% by weight of lylithium-aluminosilicate consisting of at least one of spodiumen and petalite, and this is calcined at 900 to 1300°C. A method for manufacturing a sintered body (claim 2). These inventions will be explained below.

The calcium silicate sintered body of the invention of claim 1 has a composition of lithium-aluminosilicate (hereinafter referred to as "
It's called LAS. ) and wollastonite, and does not contain any other components.

That is, the aim is to improve the disadvantages of wollastonite by simply blending a limited amount of LAS, while retaining the advantages of the properties of wollastonite.

[0010] The wollastonite here may be either α-wollastonite or β-wollastonite. This wollastonite may be one obtained by rearranging tobermorite or xonotrite into wollastonite during firing. Furthermore, α-wollastonite may be rearranged from β-wollastonite. Alternatively, it may be α-wollastonite or β-wollastonite from the beginning.

[0011] The LAS blended here has a coefficient of thermal expansion of -120 x 10-7 to +20 x 10-7 (/°C). The LAS used here has a coefficient of thermal expansion of -12
It is difficult to obtain a LAS of 0x10-7 or less, whether synthetic or natural. In addition, the upper limit of the thermal expansion coefficient was set to +20 x 10-7 (/℃) because adding LAS with a higher thermal expansion coefficient not only does not significantly improve the thermal shock resistance of calcium silicate, but also increases the thermal shock resistance of calcium silicate. This is because if a large amount of calcium silicate is added, the processing properties of the obtained sintered body will be poor and it will not be possible to obtain a good calcium silicate sintered body material. A more preferable range of the thermal expansion coefficient of LAS is -120 x 10-7 to +5 x 10-7 (/°C
).

[0012] The particle size of LAS is in the range of 1 to 100 μm. Setting this to less than 1 μm is not a good idea because fine pulverization is difficult. Moreover, if the particle size of LAS exceeds 100 μm, the strength of the sintered body decreases, which is not preferable. A more preferable range of particle size is 1 to 50 μm.

[0013] The above-mentioned LAS is blended in an amount in the range of 5 to 80% by weight. Moreover, the coefficient of thermal expansion of the sintered body is set to -65 x 10-7 to +65 x 10-7 (/°C). If the amount of LAS added is less than 5%, even if LAS with the minimum coefficient of thermal expansion is blended, the coefficient of thermal expansion of the resulting sintered body cannot be lowered to +65 x 10-7 (/℃). Therefore, the effect of improving the thermal shock properties of the sintered body is not sufficient. Since such a sintered body has a relatively large coefficient of thermal expansion, dimensional changes are large, and accuracy deteriorates, making it impossible to be a good material.

[0014] If the amount of LAS added exceeds 80%, the machinability and other machinability of the calcium silicate sintered body will be impaired, causing problems as an industrial material. A more preferred mixing ratio of LAS is 15-60%. The amount of LAS added is specifically determined within the above range in relation to the thermal expansion coefficient of the LAS used, the thermal expansion coefficient of the obtained calcium silicate sintered body, and the thermal shock resistance based thereon.

A second aspect of the invention is a method for producing the calcium silicate sintered body according to the first aspect. The raw materials used here are two components: calcium silicate crystals and LAS, and nothing else is used. The calcium silicate crystals used include one or a mixture of tobermorite, xonotlite, and wollastonite. The LAS mixed therein is composed of one or more of eucryptite, α or β type of spodiumen, and petalite.

[0016] As the calcium silicate crystals, natural ones may be used, or those produced by already known methods can also be used. To produce calcium silicate,
For example, water is added to a mixture of silicic acid raw materials and calcareous raw materials, and this is subjected to a hydrothermal synthesis reaction in an autoclave. Silicate raw materials used here include silica stone, silica sand, silica flower, diatomaceous earth, etc., and calcareous raw materials include:
Any known materials such as quicklime, slaked lime, and cement can be used. As the calcium silicate crystal, one or a mixture of tobermorite, xonotlite, and wollastonite can be used.

LAS as the other raw material can be either natural or synthesized. Synthetic ones are advantageous because their coefficient of thermal expansion can be varied over a wide range. The synthesis of LAS requires, for example, Li2O raw material, Al
A glass frit is obtained by melting and cooling a raw material batch of 2 O3 raw material and SiO2 raw material at a predetermined blending ratio, and then a predetermined crystallization treatment is performed on this glass frit to produce the glass frit.

The Li2O raw materials used here include lithium oxide and lithium carbonate, the Al2O3 raw materials include aluminum oxide, aluminum hydroxide, potassium feldspar, and kaolin, and the SiO2 raw materials include silica sand,
Potassium feldspar, soda feldspar, etc. are used. As LAS, one or a mixture of petalite, spodumene, and eucryptite can be used.

In addition to lithium feldspar with a ratio of lithia, alumina, and silica of 1:1:6, LAS has a ratio of 1:1:3, 1:1:10, 1:1:12, and 1:1:1. :1
:15 can also be used.

[0020] The raw material mixture of calcium silicate crystals and LAS is formed into a molded body by a conventionally known method. As a molding method, for example, a paper making method, a wet press method, a dry press method, etc. can be suitably used. This molded body has 9
It is fired at a firing temperature of 00 to 1300°C to form a sintered body.

[0021] If the firing temperature is less than 900°C, it takes a long time for grain growth of wollastonite, which is not preferable for industrial production. In addition, the firing temperature is 1300℃
Exceeding this temperature approaches the melting point of wollastonite, causing local vitrification, which is undesirable. After raising the temperature to this firing temperature, it is maintained for a predetermined period of time, for example, 5 to 6 hours, and then slowly cooled to obtain a product.

[0022] Examples of the present invention will be described below, and tests on the obtained products will also be explained.

[0023]

[Example] (Examples 1 to 5) Using slaked lime as the calcareous raw material and silica stone as the silicic acid raw material, CaO:SiO
2 were mixed in a molar ratio of 1:1. Add 400 parts by weight of water to 100 parts by weight of this raw material and autoclave at 220°C to obtain xonotlite.
It was dried at 20°C to obtain a dry powder of xonotlite crystals.

On the other hand, LAS was created as follows. By weight, SiO2, 71%, Al2O
Silica sand, alumina, lithium carbonate, and calcium carbonate were mixed to have a content of 3.21%, Li2O, 5%, and CaO, 3%. This raw material batch was melted at 1600° C. for 5 hours and then cooled to obtain a glass frit.

[0025] For this glass frit, the temperature increase rate was 5°C.
/min, 750℃ for 2 hours, 850℃ for 2 hours, 1250℃
Each was held for 2 hours. After slow cooling, this was subjected to X-ray diffraction, and the composition of this was confirmed to be β-spodumene. Also, its coefficient of thermal expansion is +5×10
-7 (/°C). This β-spodumene was wet-pulverized in an alumina vibrating mill in ethanol to give a particle size of 2 μm.

[0026] The above xonotlite and β-spodumene are blended so that the wollastonite and β-spodumene in the sintered body after firing are 90% by weight and 10% by weight, respectively. After wet mixing in ethanol in a ball mill for 24 hours, this was dried to obtain a sample powder.

After molding this sample powder, the temperature was increased at a rate of 5°C.
The temperature was raised to 1,100°C at a rate of 1,100°C per minute, held at 1,100°C for 5 hours, and then cooled in the furnace.

[0028] In Examples 2 to 4, the amount of LAS added was changed, and in Example 5,
Furthermore, the particle size of LAS was also changed. The following experiment was conducted on the sintered body obtained here, and the results are shown in Table 1.

The coefficient of thermal expansion shown in Table 1 is the value at 800°C, and the measurement was carried out at a diameter of 5 mm from the sintered body.
A sample with a length of 15 mm was taken out, and the test was conducted using a differential thermal dilatometer at a heating rate of 20° C./min. The critical thermal shock temperature difference is determined by taking a 4 x 4 x 35 mm sample and subjecting it to a thermal shock using the normal underwater quenching method, as determined by JIS R 1.
A three-point bending strength test was conducted as specified in 601, and the strength was determined based on the temperature difference at which the strength decreased. The thermal shock temperature difference in this case was given in steps of 50°C in the range from room temperature to 1000°C. Furthermore, machinability was determined by drilling with a drilling machine using a drill with a diameter of 10 mm.

[0030] The coefficient of thermal expansion is -40×10-7 to +40
×10-7 (/℃) is excellent ◎, -65 × 10-7 to +6
Those within the range of 5 x 10-7 (/°C) excluding the above-mentioned excellent range were rated as good and ○, and those outside the excellent and good ranges were rated poor and ×.

Regarding the critical thermal shock temperature difference, a value of 200°C or more was evaluated as excellent, ⊚, 100 to 200°C was evaluated as good, and a value of 0 to 100°C was evaluated as poor. In terms of bending strength, 500 kgf/cm2 or more is excellent and ◎, 300 to 500 kgf/cm2 or more is good and ○, and less than 300 kgf/cm2 is bad and ×.

Regarding machinability, those with good machining ease and finishing accuracy are ◎, good are those with slightly poor machining ease and finishing accuracy, and ○ are those with considerably poor machinability. Not possible, marked as ×.

[0033] In the final evaluation, each item was rated ◎(
Those with a rating of ``Excellent'' are ◎, those with ○ (Good) in any item are rated with ○, and those with × (Unsatisfactory) in any item are rated with ×.

[0034]

[Table 1] As shown in Table 1, all of the sintered bodies of Examples obtained good results. In particular, those rated ◎ were good in all tests and could be satisfactorily used as molding materials for hot pressing and the like.

(Examples 6 to 10) SiO2 is 45%, Al2O3 is 40%, and Li2O is 10% by weight.
, silica sand, alumina, so that TiO2 is 5%.
I prepared lithium carbonate and titania. This raw material batch was melted at 1600° C. for 5 hours and then cooled to obtain a glass frit. This glass frit was heated at a heating rate of 5℃/
The mixture was fired at 750° C. for 2 hours and at 850° C. for 2 hours to obtain crystallized glass. When this material was subjected to X-ray diffraction, it was confirmed that the composition was β-eucryptite, and when its thermal expansion coefficient was measured, it was found to be -100.
×10-7 (/°C).

[0036] This β-eucryptite was wet-pulverized in ethanol using an alumina vibrating mill to obtain a particle size of 2 μm.

After firing, the xonotlite of Example 1 was blended so that the weight ratio of wollastonite crystals was 95% and the β-eucryptite was 5%, and this was mixed in a bowl in ethanol. After wet mixing in Lumil for 24 hours, the mixture was dried to obtain a sample powder.

After molding this sample powder, the temperature was increased at a rate of 5°C.
The temperature was raised to 1,100°C at a rate of 1,100°C per minute, held at 1,100°C for 5 hours, and then cooled in the furnace.

[0039] In Examples 7 and 8, the added amount of LAS was changed from that in Example 6, and in Example 9, the added amount and firing temperature were changed. (900°C), and in Example 10, further L
The particle size of AS was also changed.

The sintered body thus obtained was subjected to the same experiment as in Example 1, and the results are shown in Table 2.

[0041]

[Table 2] The results are substantially the same as those of Examples 1 to 5, and good results were obtained in all cases.

(Example 11) Zonotlite 50 by weight ratio
%, a sintered body was produced in the same manner as in Example 7, except that 10% of naturally produced β-wollastonite, 10% of α-spodumene as naturally produced LAS, and 10% of petalite were used. I got it. The same experiment as in Example 1 was conducted on this sintered body, and the results are shown in Table 3.

[0043]

[Table 3] (Comparative Examples 1 to 5) Sintered bodies were obtained using the blending ratio of LAS as shown in Table 4. The same experiment as in Example 1 was conducted on this sintered body, and the results are shown in Table 4.

[0044]

[Table 4] Comparative Example 1 does not contain LAS, Comparative Example 2 contains LAS
This is an example of mixing a small amount of In both cases, the coefficient of thermal expansion and critical thermal shock temperature difference of the sintered bodies are not good.

Comparative Example 3 uses a large amount of LAS, but in this case, the machinability deteriorates, making it impossible to evaluate the entire product. Comparative Examples 4 and 5 are cases where the particle size of LAS is large, and the bending strength of this sintered body is reduced.

[0046]

[Effects of the Invention] As described above, according to the present invention, it is possible to produce a low thermal expansion, high strength calcium silicate sintered body that has significantly improved thermal shock resistance without impairing mechanical strength such as bending strength. Therefore, the sintered body can be used in a more advanced manner than ever before.

Claims (2)

[Claims] Claim 1: Comprising lithium-aluminosilicate and wollastonite, the content of lithium-aluminosilicate is 5 to 80% by weight, and the coefficient of thermal expansion is -1.
20 x 10-7 to +20 x 10-7 (/°C), and the particle size is 1 to 100 μm, and the coefficient of thermal expansion of the sintered body is -65 x 10-7 to +65 x 10-7. A calcium silicate sintered body characterized by: 2. Lithium-aluminosilicate comprising 20 to 95% by weight of calcium silicate crystals comprising at least one of tobermorite, xonotrite, and wollastonite, and at least one of eucryptite, spodumene, and petalite. A method for producing a calcium silicate sintered body, which comprises forming a molded body from a mixture with 80 to 5% by weight of a salt, and firing the molded body at 900 to 1300°C.