JPH01108174A - Inorganic material - Google Patents

Abstract

PURPOSE:To obtain a light-weight, high-strength inorganic material having excellent water resistance and heat resistance, by impregnating particles of xonotlite and/or beta-wollastonite bonded by a specific metallic oxide (hydrate) with an organic substance and polymerizing. CONSTITUTION:Slurry of xonotlite is cast into a frame having dehydrating function and dehydrated under pressure to give a molded article of xonotlite, which is dried to give a molded article having 0.04-2.3g/cm<3> bulk density. Then the molded article is impregnated with a metallic alkoxide (e.g. trimer-tetramer of methyl silicate), immersed in cold water, heated to 120-200 deg.C to give a molded article of xonotlite and/or beta-wollastonite which is bonded by a metal oxide (hydrate) by the impregnation with the metallic alkoxide and has 2.5-4.5X10<-6>/ deg.C coefficient of thermal expansion. Then the molded article is impregnated with 5-10wt.% organic substance (e.g. methyl methacrylate) having 50-1,000 molecular weight and heated to polymerize the organic substance.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to an inorganic material, particularly a xonotlite and/or β-wollastonite-based material that is lightweight, has high strength, and has improved water resistance and heat resistance. .

[Prior art] Zonotlite mainly has plate-shaped crystals and needle-shaped crystals with a size of several microns. In particular, needle-shaped xonotlite has the structure and form of a whisker. Strength against specific gravity (specific strength) can be achieved by simply adding materials such as clay, cement, clay, etc., and drying after dehydration pressing.
A molded article with a high

This molded product is lightweight, porous, and has high heat resistance, so it has attracted attention as a fire-resistant heat insulating material and fire-resistant coating material, and some of it is also used.

In addition, β wollastonite is 650 to 11
It is obtained by firing at a temperature of 25° C. or higher, and is also used for the same purposes as xonotlite through almost the same treatment.

[Problems to be solved by the invention] However, although these materials are quite satisfactory in terms of lightness, heat insulation, and fire resistance, they are not necessarily sufficient in strength and water resistance, which limits the range of their use. It had some drawbacks. On the other hand, in ceramic materials with high strength, strength is generally achieved by firing or sintering, but in reality, considerable care is required in selecting auxiliary agents and conditions. However, the resulting product had the disadvantage of being almost impossible to process.

[Means for Solving the Problems] The present inventor eliminates these conventional drawbacks and develops a calcium silicate-based material that has excellent properties, particularly in terms of light weight, heat insulation, and fire resistance. As a result of various studies and examinations aimed at finding a means to improve strength and water resistance without substantial loss, we found that xonotlite and β
It has been found that the above object can be achieved by bonding wollastonites together with a specific material.

Thus, in the present invention, xonotlite and/or β-wollastonite particles are bonded to each other by a metal oxide or a hydrate thereof obtained by hydrolysis of a metal alkoxide, and an organic substance having a molecular weight of 50 to 1000 is impregnated and polymerized. To provide an inorganic material consisting of

The xonotlite used in the present invention is generally synthesized by mixing siliceous raw materials such as quartz silica sand or humid silica and quicklime raw materials in approximately equimolar water, with a solid content concentration of 4 to 4.
8% aqueous slurry in an autoclave with a stirrer
It can be obtained by hydrothermal treatment at 0° C. or higher for 4 to 8 hours. In addition, β-wollastonite is obtained by heat-treating the above-mentioned xonotlite at 850 to 1125°C, and it has substantially the same properties as the above-mentioned xonotlite, with no changes in morphology or physical properties. It won't change much.

Therefore, in the present invention, there is no problem even if the final molded body starts from xonotrite in terms of composition and changes to β-wollastonite, or the starting material is β-wollastonite. However, α - Wollastonite is unsuitable for the present invention because it shrinks and cracks, and therefore when xonotlite is heated, it transforms into α-wollastonite.
It is inappropriate to employ temperatures above 5°C.

Incidentally, as mentioned above, since there is almost no distinction between xonotlite and β-wollastonite in terms of their properties, xonotlite will be explained below as a representative.

As mentioned above, xonotrite crystals have a plate-like crystal and a needle-like crystal in terms of morphology, and are divided into polycrystals, single crystals, and twin crystals in terms of crystal structure.The term "particles" in the present invention refers to the generalization of these crystals. be.

However, as the form most suitable for the purpose of the present invention, it is desirable that the form has excellent acicularity from the viewpoints of good moldability, high specific strength, etc.

Examples of such xonotlites having excellent acicular properties are disclosed in Japanese Patent Application Laid-open No. 77619/1982 and Japanese Patent Application Laid-open No. 210561/1989, and such xonotlites give particularly favorable results. Since the thus obtained xonotrite slurry is in the form of needles or fine fibers, it can be easily dehydrated and molded by means of pouring it into a mold having a dehydrating function (such as a filter press machine).

In the present invention, pressurization, along with dehydration molding, can be an important means for developing high strength. The xonotlite molded body thus dehydrated forms an aggregate of needle-like crystals, and undehydrated water exists in the voids between the needle-like crystals. (In this case, the bulk density of the molded product after drying will be 0.08 or more.) However, the hydrous molded product has sufficient strength, and its dimensions after removal from the mold almost match those of the final molded product. You get what you get. Therefore, it is a meaningful means to mold the material into the shape of the final molded product during press dehydration molding.

Further, it is also possible to put an appropriate pattern on the molded product after pressing, or to perform cutting or grinding processing on the molded product. In addition, depending on the performance required of the final molded product, the bulk density of the molded product and the filling rate of xonotlite, etc. in the final molded product can be adjusted by adjusting the amount of slurry introduced into the mold, the thickness of the molded product, etc. It is possible. Further, if desired, other components such as fiber reinforcing materials and fillers may be appropriately mixed into the slurry as long as they do not depart from the purpose of the present invention.

Further, in the present invention, an ultra-light molded article having a bulk density of 0.04 without using a dehydrating press as described in JP-A No. 60-210561 can also be effectively utilized in the present invention. It is also possible to use a molded powder prepared from an aqueous xonotlite slurry.

The bulk density of the dried molded product of xonotlite that can be used in the present invention can range from 0.04 g/cm3 to close to 2.7 g/cm3, which is the true specific gravity of xonotlite, as described above. The practical range is 0.08 to 2.3 g/cm
It is appropriate to adopt 3. The xonotrite molded body thus obtained is then impregnated with a metal alkoxide. However, as described above, this molded product still contains water between the particles, so the metal alkoxide will not be impregnated as it is, and therefore it is dried until all or part of this water remains. In this case, complete drying can increase the impregnation rate of metal alkoxide, but
On the other hand, leaving some water has the effect of accelerating the hydrolysis in the step of hydrolyzing the metal alkoxide, which will be described later. Therefore, good results can be obtained by arbitrarily selecting the degree of drying of the molded body depending on the purpose. As a drying method,
Natural drying, drying in a heating oven at 300-1000℃, etc.
Various drying means such as high frequency drying are employed, and the shrinkage rate is about 0.01% by any drying means. In addition, the thermal expansion coefficient is 2.5 to 4°5 Therefore, it becomes possible to obtain a final molded body with high dimensional accuracy.

In fact, metal alkoxides are contained in these molded bodies, but the general properties of the metal alkoxides used are as follows:
It is preferable to use one having low viscosity and excellent ability to penetrate into the inside of the molded article. Specifically, monomers and oligomers of methyl alkoxide, ethyl alkoxide, and propyl alkoxide are preferable, and these may be used alone or in combination. In addition, the metal of the metal alkoxide includes silicon, aluminum,
Examples include zirconium and magnesium, which can be used alone or in combination. In particular, a trimer to tetramer of methyl silicate (silica content: 51%) (M Silicate, manufactured by Tama Chemical Co., Ltd. 51) is suitable because it has excellent penetration power.

As the impregnation method, various methods such as vacuum degassing and pressure impregnation can be adopted, but in the case of the dry molded bodies of xonotrite and β-wollastonite suitable for the present invention described above, simply soaking in a metal alkoxide liquid is possible. By simply dipping, it is possible to easily impregnate 100% of the theoretical porosity calculated from the true specific gravity of the molded body. However, even in a molded article suitable for the present invention, a sol liquid in which colloidal fine particles obtained by pre-hydrolyzing a metal alkoxide are dispersed, a commercially available colloidal silica sol, etc. are hardly impregnated.

The time required for impregnation varies depending on the bulk density and thickness of the molded body used, but generally 100% of the theoretical porosity is impregnated in several minutes to several hours. The impregnation rate can be adjusted as necessary by shortening the dipping time, removing a predetermined amount from the impregnated material, or impregnating only the surface layer.

The molded body impregnated with the metal alkoxide thus obtained undergoes hydrolysis due to water contained inside the molded body or moisture in the air, in conjunction with the catalytic action of the basicity of the molded body itself. However, this reaction progresses at a slow rate, and therefore some of the metal alkoxide evaporates, making it less effective or requiring a considerable amount of time for hydrolysis. For this reason, in the present invention, it is desirable to force the hydrolysis to proceed.There are various means for doing so, but for example, it is preferable to immerse the molded product containing the metal alkoxide in cold water and then heat it to around 100°C. If the molded product is directly immersed in hot water, the metal alkoxide impregnated inside the molded product will expand before hydrolysis occurs and come out of the molded product, making it ineffective.

It is also possible to decompose with high-pressure steam in an autoclave, but this is not preferable because the metal alkoxide evaporates and does not work effectively.The most suitable method in the present invention is to immerse the metal in cold water and then heat it. However, the higher the temperature, the faster the hydrolysis proceeds. Therefore, when such an operation is carried out in an autoclave, the temperature required for zero decomposition is preferably 120 to 200 DEG C., and the time is preferably from several minutes to several hours.

In addition, it is preferable to use methyl alkoxide as the type of alkoxide because hydrolysis can be completed at low temperature and in a short time, and there is little flow of alkoxide out of the molded product.The molded product that has been hydrolyzed in this way is taken out of the water and dried. By doing so, a final molded product can be obtained.

The molded product obtained in this way has a porous state due to the extraction of by-product alcohol and residual components.
By impregnating it with alkoxide again and repeating the same treatment steps as described above, it becomes possible to obtain a product with even higher strength.

Further, if necessary, a metal component such as silica, which acts as a bonding agent between xonotrite and β-wollastonite in the molded body, can be fired to form a molded body with higher strength.

The weight ratio of xonotrite or β-wollastonite to the binder in the molded body varies depending on the bulk density of the molded body, the impregnation rate of alkoxide, and the number of repetitions of the impregnation-hydrolysis process, but preferably, it is based on the weight of the molded body, It is appropriate to adopt a weight ratio of xonotlite and/or β-wollastonite of 20 to 80%. The higher the weight ratio, the higher the specific strength of the molded product obtained.

In the present invention, the obtained molded product is further impregnated with an organic substance having a molecular weight of 50 to 1000 and polymerized. If the molecular weight of the organic substance used is lower than the above range, the water resistance and strength will be insufficient, whereas if it is higher, it may not be able to be sufficiently impregnated into the molded article, so neither is preferable.

Examples of such organic substances include acrylic monomers, vinyl acetate monomers, styrene monomers, diallyl phthalate monomers, diethylene glycol bisallyl carbonate, and the like.

Examples of acrylic monomers include methyl methacrylate and hydroxyethyl methacrylate; examples of vinyl acetate monomers include vinyl acetate and vinyl propionate; examples of styrene monomers include styrene; examples of diallylphthalate monomers include diallyl phthalate. .

As a means for impregnating the molded body with such an organic substance, for example, impregnation by capillary action, impregnation by reduced pressure or pressurization, etc. can be appropriately employed.

In addition, the amount of organic substance impregnated is 5 to 1O based on the total components of the molded product.
It is appropriate to adopt approximately % by weight. If the amount of impregnation is less than the above range, it will be difficult to effectively improve the strength, water resistance and heat resistance.On the other hand, if it exceeds the above range, shrinkage during polymerization of the organic substance will cause the molded product to become stiffer. These organic substances are not preferred since they may cause partial cracks or a decrease in heat resistance. However, these organic substances can be impregnated as they are or by dissolving them in a suitable organic solvent such as toluene.

The organic substance impregnated into the shaped body is then polymerized. As such polymerization means, for example, heating polymerization or the like can be appropriately employed.

The thus obtained product exhibits superior workability compared to conventional engineering ceramics and easily machinable ceramics, and is more densified than the xonotrite and β-wollastonite molded bodies used as precursors. It has the advantages of high specific strength, excellent workability in polishing, etc., and the possibility of mirror finishing and thin film formation.

In addition, specific examples of the use of this material include artificial marble,
It is useful for the outer shells of home appliances that receive heat such as ovens and irons, the inner plates of microwave ovens, and building materials.

[Example] 10 parts by weight of quicklime, 10 parts by weight of fumed silica, 3 parts by weight of water
An aqueous slurry containing 80 parts by weight was charged into an autoclave equipped with a stirrer and reacted at 200° C. for 6 hours to obtain a xonotlite needle crystal slurry having a solid content concentration of 5%. Pour the slurry into a mold having a dewatering mechanism, and
Pressurized and dehydrated at 0 kg/cm2, dried, bulk density 0.7 g
Three molded bodies of 400 X 100

These molded bodies were immersed for 1 hour in an ethanol solution of 20% by weight methyl silicate, taken out, the methyl silicate on the surface was wiped off, and immersed in cold water for about 30 minutes.
The temperature was raised to 180° C. over a period of several minutes, maintained at this temperature for 1 hour, and then taken out and dried.

The bulk density of each was 0.82 g/cc.
, 30%, and 60% toluene solutions for 1 hour, respectively, and then heated to BO°C and polymerized for 1 hour and 30 minutes. The bulk density and bending test results of each molded body are shown in the table below.

Claims (1)

[Claims] 1. Zonotlite and/or β-wollastonite particles are bonded to each other by a metal oxide or a hydrate thereof obtained by hydrolysis of a metal alkoxide, and have a molecular weight of 50 to
An inorganic material made by impregnating and polymerizing 1000 organic substances. 2. Claim (1) in which the metal of the metal alkoxide is silicon, aluminum, zirconium, or magnesium.
inorganic materials. 3. The inorganic material according to claim (1), wherein the alkoxide of the metal alkoxide is a monomer or oligomer of methyl alkoxide, ethyl alkoxide, or propyl alkoxide. 4. Organic substances with a molecular weight of 50 to 1000 include acrylic monomers, vinyl acetate monomers, styrene monomers,
The inorganic material according to claim (1), which is a diallyl phthalate monomer and diethylene glycol bisallyl carbonate.