JPH0336776B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a method for manufacturing a molded product using specified calcium silicate as a base material, and more specifically, it contains a large amount of fine pores, has a desired strength despite its low density, and is useful as a heat insulating board. The present invention relates to a method for producing a porous composite. The calcium silicate used in the present invention has a diairolite crystal structure, that is, 2CaO・3SiO ₂・mH ₂ O (in the formula, m is a positive number), but it has a form in which amorphous silicon dioxide is incorporated into the crystal. Therefore, the general formula is 2CaO・3SiO ₂・nSiO ₂・mH ₂ O (in the formula,
m and n are positive numbers), and the SiO ₂ /CaO molar ratio is generally about 1.6 to 4.2, preferably about 1.8 to 3.2. In addition, such calcium silicate has a concentration of 3000 to 10,
According to an electron micrograph at 000x magnification, the flakes with two symmetrical sides, circular or oval, with an average longitudinal diameter of 0.1 to 30 μm and a thickness of 0.005 to 0.1 μm, are aggregates of petals, especially rose petals. (hereinafter also simply referred to as petal-shaped calcium silicate),
Generally, it is an inorganic powder having a very large bulk specific volume of 7 to 25 c.c./g and a large number of pores with a pore volume of 4 to 10 c.c./g. The above-mentioned petal-shaped calcium silicate has the great feature that a molded product with considerable strength can be obtained simply by dry compression molding, and it can be used as a molded product of petal-shaped calcium silicate alone or as a powder without any shape. A method has been put into practical use in which a small amount of petal-shaped calcium silicate is mixed with the body to form a molded body. However, the applied molding pressure is 50~200Kg/
A high pressure of cm ² is required, and the pores of the petal-shaped calcium silicate are reduced, making it difficult to obtain molded products with low density and high porosity. In contrast, the present invention relates to a method for wet compression molding petal-shaped calcium silicate, and although it requires wet compression molding and drying operations, it has low density, large porosity, and sufficient strength. The purpose is to obtain a molded body. However, when petal-shaped calcium silicate is subjected to wet compression molding, it is generally not easy to stably obtain a molded product having the desired low density, high porosity, and sufficient strength. This is because petal-shaped calcium silicate exhibits a unique molding behavior due to its unique structure as described above. In other words, in the wet process, the fine pores of the petal-shaped calcium silicate filled with water resist compression as if it were a solid, resulting in uneven compression and, depending on the conditions, the strength of the molded product may drop significantly. . To explain more specifically, when the pores of petal-shaped calcium silicate, for example, with a pore radius of 0.01 to 0.1 μm, are filled with water, it generally takes 300 to 30 μm to extrude and deform the water.
A phenomenon unique to petal-shaped or porous powders in which a molding pressure that opposes the osmotic pressure of water up to Kg/cm ² is required, and the micropores are hardly deformed and the deformation is concentrated in the larger pores. It was found that the resulting molded product becomes brittle and its strength decreases due to cracks occurring within the particles. As a result of extensive research based on this knowledge, the present invention has found that in order to prevent the pores of the petal-shaped calcium silicate from being sufficiently filled with water, water is generally blended in an amount equal to or less than 55% of the oil absorption amount of the petal-shaped calcium silicate. The present invention was completed based on the discovery that a molded article having the desired low density, high porosity, and sufficient strength can be obtained with low compressive force. That is, in the present invention, after blending water in an amount corresponding to 55% by weight or less of the oil absorption of calcium silicate having a gyrolite crystal structure and a SiO ₂ /CaO molar ratio of 1.6 to 4.2, compression molding is performed, This is a method for producing a molded article, which is characterized in that it is then dried. In addition,
The oil absorption amount referred to herein is measured by the method specified in JIS K 6220 Section 6.21, and represents the pore volume in the powder. The oil absorption (VO) of the petal-shaped calcium silicate used by the present inventors is determined by its bulk volume (BV)
Since there is a correlation as shown in the following equation, the following explanations and examples are all described in terms of bulk volume. VO=0.219BV+2.34 The water blended in the present invention plays a role as a binder and a lubricant in the molding process of petal-shaped calcium silicate, reduces frictional resistance during compression molding, improves the strength of the molded product, and further Since it functions to improve the release of the molded product from the mold, it is generally necessary to have an oil absorption amount of at least 10% by weight of the petal-shaped calcium silicate, and it is particularly preferable to incorporate it in an amount of 30 to 50% by weight. . As mentioned above, the key point of the present invention is the oil absorption amount, that is, the ratio of liquid to the pore volume of the petal-shaped calcium silicate. Therefore, in the case of an aqueous solution or emulsion of an adhesive, strictly speaking, the volume of the liquid including the adhesive is a problem. However, since the specific gravity of a diluted aqueous solution or emulsion is close to 1, there is not much difference on a weight basis. Therefore, their blending ratio is petal-shaped calcium silicate.
The liquid volume was defined as parts by weight per 100 parts, and was expressed in units of PHR. Similarly, the water content is defined as water volume (PHR). Furthermore, the amount of water or liquid divided by the amount of oil absorbed is defined as the water distribution rate, which means the extent to which the pores of the petal-shaped calcium silicate are filled with the liquid compound. The optimum molding pressure in the present invention varies depending on the amount of water and liquid added to the petal-shaped calcium silicate, and generally 3 kg/cm ² or more is sufficient, but if the molding pressure is too high, the resulting molded product may be brittle. Therefore, in particular 5 to 35 Kg/cm ² , preferably 10 to 30 Kg/cm 2
^cm2 . In other words, if the amount of water or liquid added to the petal-shaped calcium silicate is small, there is a molding pressure that achieves the maximum strength of the molded product at a higher pressure.
When the amount of water or liquid increases, the optimum molding pressure exists on the lower pressure side. In addition, the drying temperature in the present invention may be any temperature higher than the temperature at which the moisture contained in the molded article can volatilize, and generally
The temperature is 100°C or higher, preferably 110°C to 140°C. Thus, according to the present invention, by blending a predetermined amount of water with petal-shaped calcium silicate, good molding with low density, large porosity, and crushing strength of 20 to 30 Kg/cm ² can be achieved at low molding pressure. You can get a body. Further, in the present invention, in order to obtain a petal-shaped calcium silicate molded article with greater strength, other adhesives may be blended with the above-mentioned water. Therefore, according to the present invention, there is also provided a method for producing a molded article, which involves blending petal-shaped calcium silicate with an aqueous solution or emulsion of an adhesive, compression molding the mixture, and then drying or heat-treating the mixture. However, when an aqueous solution or aqueous emulsion of an adhesive is added to the petal-shaped calcium silicate, the liquid amount is adjusted to 10 to 55% by weight of the oil absorption amount of the petal-shaped calcium silicate, preferably 30 to 55% by weight of the oil absorption amount of the petal-shaped calcium silicate. Blending in an amount equivalent to ~50% by weight is essential in order to obtain the desired molded product with high strength. That is, even when an aqueous solution or aqueous emulsion of an adhesive is blended with the petal-shaped calcium silicate of the present invention, if the amount of the blended liquid is out of the above range, uniform compression molding will not be achieved, so the molded product must be heated. Even after treatment, a molded article with the desired strength cannot be obtained. The adhesive used in the present invention is not particularly limited to known adhesives as long as it is water-soluble or can form an aqueous emulsion. For example, inorganic adhesives such as alkali metal silicate adhesives, phosphate adhesives, colloidal silica adhesives, water glass adhesives; vinyl acetate adhesives, acrylic adhesives,
Examples include thermoplastic adhesives such as ethylene-vinyl acetate copolymer adhesives; thermosetting resin adhesives such as urea resins, amino resins, phenol resins, and epoxy resins. In particular, an aqueous solution or emulsion of a thermosetting resin is preferably used. In addition, when a non-aqueous organic solvent is used, even if the amount of liquid added to the petal-shaped calcium silicate is specified in the same manner as in the present invention, it is not possible to obtain a molded product having the desired practical strength. I can't. Typical examples of water-soluble thermosetting resins include urea resins and modified urea resins. Epoxy resin emulsion was used as the emulsion type thermosetting resin, but phenol resin,
Resorcinol resin, urethane resin, dap resin, etc. can be used without any problems. The blending ratio of the thermosetting resin may be determined by taking into consideration the strength, density, etc. of the intended molded product, but generally 2 to 100 parts by weight per 100 parts by weight of petal-shaped calcium silicate is sufficient. Even when a predetermined amount of an aqueous solution or emulsion of the adhesive as described above is blended with petal-shaped calcium silicate, the molding pressure is generally 3 kg/
Compression molding may be performed at cm ² or more, particularly 10 to 40 kg/cm ² . Further, the molded body may be dried or heated at a temperature at least at which the contained moisture is volatilized and at a temperature at which the adhesive hardens and exhibits adhesive strength. In the present invention, there is no restriction at all that other fillers may be added depending on the intended use of the molded article. For example, in order to reduce costs, it is easy to incorporate lightweight fillers such as perlite, shirasu balloons, or expanded polystyrene beads while taking physical properties into consideration. Also, it is an effective method to add a fibrous filler to make the molded product more tough. As the fibrous filler, asbestos, glass fiber, vinylon fiber, nylon fiber, etc. can be used without any restrictions, but non-bundled fibers are suitable for bulky powders such as petal-shaped calcium silicate due to the volume ratio. . Uniformly mixing and dispersing unbound fibers into such bulky powder is difficult in dry conditions, but when an aqueous solution or emulsion is added to create a wet system, the two can be mixed extremely uniformly. It was discovered that The reason for this is probably that the bulky powder is so light that the shearing force produced by the stirring blades of the mixer does not act properly within the system. That is, when this system is made into a wet system, the weight of the individual particles of petal-shaped calcium silicate increases, and the agglomeration effect between the particles also works to shear and disperse the fiber bundles, which is why the so-called mixing effect works well. Conceivable. The amount of the fibrous filler to be blended varies depending on the specific gravity and length of the fibers, but 1 to 30 parts by weight per 100 parts by weight of petal-like calcium silicate is sufficient. Generally a few mm
Longer fibers tend to form yarn balls when mixed, so 1.
It is practical to mix up to 3 parts by weight, and in the case of shorter fibrous fillers, it is possible to uniformly mix a large amount. Practically speaking, the amount of the fibrous filler to be blended is determined by taking into account the degree of improvement in toughness, economic efficiency, processability, etc. The molded product thus obtained has a white, dense surface, and as shown in the examples, has sufficient strength while having a low density and a large porosity. Moreover, it almost completely retains the pores of petal-shaped calcium silicate. Therefore, the molded article of the present invention is useful as a heat insulating board, a carrier for holding liquids such as fragrances and agricultural chemicals, or a carrier for gas treatment agents. Examples are shown below, but the present invention is not limited to these examples in any way. Examples 1 to 6, Comparative Examples 1 and 2 Petal-shaped calcium silicate (manufactured by Tokuyama Soda KK, Fluorite R) having a bulk volume of 8.3 and 12.4 was mixed with water in the amount shown in Table 1. For mixing, water was slowly added to the petal-shaped calcium silicate flowing in a high-speed stirrer, and the mixture was further mixed for 3 minutes. The obtained mixture was placed in a cylindrical mold with a diameter of 20 mm, and the mixture was molded into Table 1 using a hydraulic press.
The molded product was compression molded at the pressure shown in 1 to obtain a molded product with a height of about 10 mm, and then dried overnight in a dryer at 130° C. to prepare a sample. Measured density and crushing strength (Tensilon, 23
℃, RH 60%, compression speed 1 mm/min) (number of measurements n=10) is also shown in Table 1. Note that the crushing strength is the value obtained by dividing the stress at which the sample breaks when compressive force is applied from the radial direction of the cylindrical sample by the product of the diameter and height of the sample. FIG. 1 shows the change in crushing strength depending on the water content, and the importance of the specified water content in wet compression molding of petal-shaped calcium silicate can be clearly understood.

[Table] Examples 9 to 11 100 parts of Fluorite R having a bulk volume of 10.3 was mixed with water in the proportions shown in Table 2, and molded bodies were obtained in the same manner as in Example 1 under the pressures shown in Table 2. Table 2 also shows the density, average value of crushing strength, and variation (standard deviation) of crushing strength of the obtained samples. (n=10) A large standard deviation indicates that extremely weak samples are mixed and the molding is non-uniform.

[Table] Figure 2 shows the dependence of crushing strength on molding pressure.
It is clear that excessive pressure makes the compacts brittle. Examples 10 to 14, Comparative Example 3 Fluorite with a bulk volume of 10.3 - 100 parts of R and urea resin (manufactured by Sumitomo Bakelite KK) in the proportion shown in Table 3
A sample was prepared in the same manner as in Example 1 by blending an aqueous solution of UA104) and dimethyl oxalic acid (curing catalyst, 10% of urea resin). Also, epoxy resin (manufactured by Sumitomo Bakelite KK)
The main hardening agent of EA206A) was first emulsified using a homogenizer, and then diluted with water to form a water emulsion in the proportions shown in Table 3.The mixture was blended with 100 parts of Fluorite-R having a bulk volume of 10.3, and then mixed in the same manner as in Example 1. A sample was prepared. Table 3 shows the average values of density and crushing strength of each sample. (n=10) In addition, for some examples, the porosity measured by mercury intrusion method is shown. From Table 3, it is clear that the strength is improved at a slight sacrifice in density and porosity.

[Table] Examples 15 to 17 Fluorite with a bulk volume of 11.0 - 100 parts of R and vinylon fiber in the proportion shown in Table 4 (manufactured by KK Kuraray)
RB203 (a 6.6 mm long staple) was stirred for 3 minutes using a high speed stirrer, but the vinylon fibers were hardly dispersed. Water or epoxy resin emulsion in the proportion shown in Table 4 was slowly added to this while stirring, and
After stirring for a minute, a mixture in which fibers were uniformly dispersed was obtained. These were placed in a cylindrical mold with a diameter of 144 mm, and Table 4
It was compression molded to a thickness of approximately 10 mm using a hydraulic press under the pressure shown in . Then, the extracted molded plate was dried overnight in a dryer at 120°C. Table 4 shows the average values of the density of the molded plate (n=4), the bending strength of the sample cut to 30 x 120 mm (n=6), and the Izo impact strength (without notches) (n=10).

[Table] The thermal conductivity of Examples 20 and 22 is 0.054, respectively.
It was 0.069 Kcal/mH°C (JISA1412 flat plate comparison method). When 3 cm nails were driven into these molded bodies, the nails could be driven in without any problems. It is clear that by blending suitable fibers, molded bodies of extremely high tenacity can be obtained. Examples 18-22 After mixing 100 parts of fluorite-R with a bulk volume of 11.0 and various fillers in the proportions shown in Table 5, water, an aqueous urea resin solution (containing 10% dimethyl oxalic acid), or an epoxy resin emulsion were mixed. A molded article with a diameter of 20 mm was prepared in the same manner as in Example 1. Table 5 shows the physical properties of the obtained molded product (n=10).

【table】 [Brief explanation of drawings]

FIG. 1 shows the relationship between the water distribution rate and the compressive strength of the molded bodies according to Examples 1 to 6 and Comparative Examples 7 and 8. Second
The figure shows the relationship between molding pressure and compressive strength of molded bodies according to Examples 9 to 11 and Comparative Example 12.

Claims (1)

[Scope of Claims] 1. Having a gyrolite crystal structure, and
Molding characterized by mixing calcium silicate with a SiO ₂ /CaO molar ratio of 1.6 to 4.2 with water in an amount corresponding to 10 to 55% of the oil absorption of the calcium silicate, compression molding, and then drying. How the body is manufactured. 2 Calcium silicate has an average longitudinal diameter of 0.1~
The manufacturing method according to claim 1, which is an aggregate of circular or elliptical flakes with a thickness of 30 μm and a thickness of 0.005 to 0.1 μm. 3 Calcium silicate has the general formula 2CaO・3SiO ₂・
The manufacturing method according to claim 1, which is represented by nSiO ₂ ·mH ₂ O (in the formula, n and m are positive numbers) and has a bulk volume of 7 to 15 c.c./g. 4. The manufacturing method according to claim 1, which comprises compression molding at a molding pressure of 3 to 40 kg/cm ² . 5 Has a gyrolite crystal structure and
After blending an aqueous solution or emulsion of an adhesive with calcium silicate having a SiO ₂ /CaO molar ratio of 1.6 to 4.2 in a liquid amount corresponding to 10 to 55% by weight of the oil absorption of the calcium silicate, A method for producing a molded article, which comprises compression molding and then heating and drying. 6. The manufacturing method according to claim 5, wherein the adhesive is a thermosetting resin. 7. The manufacturing method according to claim 6, wherein 2 to 100 parts by weight of the thermosetting resin is used with respect to 100 parts by weight of calcium silicate. 8 Claim 1 adding fibrous filler
5. The manufacturing method according to item 5.