JP2006056747A - Porous formed body and its production method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a porous formed body capable of hardening without needing heat, and having excellent heat or water resistance as well as high strength. <P>SOLUTION: This porous formed body is produced by forming and hardening a raw material containing amorphous silica, a reinforcing fiber and a filler in the presence of ammonia without heating. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a porous molded body having high strength and excellent heat resistance and useful as a building material and a heat insulating material.

As a porous molded body excellent in heat insulation, a fine porous body based on a highly dispersed oxide of silicon and / or aluminum element (Patent Document 1), _{2 to} 4.5 (SiO ₂ ; M ₂ O) ) Molded body based on alkali metal silicate foam particles composed of silicon dioxide (SiO ₂ ) and alkali metal oxide (M ₂ O) in molar ratio (Patent Document 2) and expanded vermiculite in an amount of 30 to 70% by weight, inorganic bond 15 to 40% by weight of the agent, 0 to 20% by weight of the infrared opaque agent, 15 to 50% by weight of the microporous material, up to 2% by weight of B ₂ O _{3 with} respect to the weight of the reinforcing fiber, and alkali metal oxide A heat insulating molded body containing 0.5 to 8% by weight of reinforcing fiber containing 2% by weight at maximum (Patent Document 3) is known. However, these molded articles have low thermal conductivity and excellent heat insulation properties, but must be fired at a high temperature and require energy costs in production. Moreover, since the obtained material is brittle, there is a problem that the processability is not sufficient and it is powdery, so that dust is easily generated. Furthermore, since this material does not have water resistance, it will crack when absorbed. Therefore, when used as a heat insulating material, there is a problem that the condensed moisture is absorbed and cracks are generated, and the heat insulating property is greatly reduced.

  In addition, examples of the porous molded body in which ammonia is interposed in amorphous silicic acid include a high-purity silica glassy foam (Patent Document 4) and a heat-resistant siliceous foam (Patent Document 5), both of which are silica. It is a (glass) foam and needs to be foamed at a high temperature.

On the Internet (Non-Patent Document 1), an amorphous silica-based material powder such as pearlite is mixed with an aqueous solution of an alkali such as sodium hydroxide, and pressure-molded with a hot press at hundreds of degrees Celsius. Although the technology is disclosed, although the heating temperature is lower than those of Patent Documents 1 and 2, heating is required, and when the porous molded body obtained using sodium hydroxide is heated at a high temperature There are also problems with heat resistance such as heat shrinkage.
Japanese Patent Laid-Open No. 7-10651 Japanese Patent Laid-Open No. 7-69752 JP 2000-513693 A JP-A-5-345636 Japanese Patent Laid-Open No. 7-144934 Hokkaido Industrial Experiment Station Technical Information Vol. 24, no. 2, p. 6

  An object of the present invention is to provide a porous molded body that can be cured without requiring heating, and has high strength and excellent heat resistance.

  Therefore, as a result of various studies, the present inventor has surprisingly achieved high strength and heat resistance simply by using a raw material containing amorphous silicic acid, reinforcing fibers, and a filler, and curing without heating in the presence of ammonia. The present invention has been completed by finding that a porous molded body having excellent properties and water resistance can be obtained.

  That is, the present invention is a porous molded body obtained by molding and curing a raw material containing amorphous silicic acid, reinforcing fibers and a filler, and is cured without heating in the presence of ammonia. And a method for producing the same.

  Since the porous molded body of the present invention can be cured without the need for heating, the energy cost in production can be kept low, and since it has high strength and excellent heat resistance and water resistance, it can be used as a heat insulating material or a building material. Is suitable.

  The raw material of the porous molded body of the present invention includes amorphous silicic acid, reinforcing fibers, and a filler. Here, amorphous silicic acid is a raw material for forming a matrix as a porous molded body, and is not particularly limited as long as it has a form of amorphous silicic acid. For example, hydrous silicic acid and white carbon obtained by a precipitation method, silica gel and gel silica obtained by a gel method, and dry silica obtained by a combustion method are suitable. Fly ash and silica fume can also be used.

  The particle size and the like of the amorphous silicic acid are not particularly limited, but when a fine particle size is used, a high-strength porous molded body can be easily obtained. For example, fine particles of amorphous silicic acid having an average primary particle diameter of 2 to 50 nm, particularly 2 to 10 nm, and primary particles aggregated to form secondary particles are particularly preferable.

  The ratio of amorphous silicic acid to the whole raw material is preferably 30 to 80% as a mass ratio in a dry state from the viewpoint of thermal conductivity and strength development, and more preferably 35 to 75% when used as a heat insulating material, When used as a building material, 40 to 60% is preferable.

  The reinforcing fiber is a raw material mainly used for improving the strength of the porous molded body, and fibers conventionally used for building materials and heat insulating materials can be used. For example, wood fiber such as cellulose pulp, PAN (polyacrylonitrile) fiber, PVA (polyvinyl alcohol) fiber, synthetic organic fiber such as PP (polypropylene) fiber; glass fiber; carbon fiber or ceramic fiber is used as necessary be able to.

  The ratio of the reinforcing fibers to the whole raw material is preferably 1 to 20%, and more preferably 5 to 15% as a mass ratio in a dry state from the viewpoint of strength development and moldability during production.

A filler is a raw material used in order to improve the performance required by the use for the obtained porous molded body, and as a filler in the case of using a heat insulating material as a main use, a heat shielding agent (TiO ₂ FeTiO ₃ , ZrO ₂ , ZrSiO ₂ , Fe ₂ O ₃ , MnO _{2 and} other metal oxides and SiC) are preferred. On the other hand, as a filler when using general building materials as the main application, aggregates for reducing the heat shrinkage rate of wollastonite, mica, etc., aggregates for improving the fire resistance performance of calcium carbonate, dolomite, gypsum, etc. Is preferred.

  The ratio of the filler to the whole raw material is preferably 5 to 50% as a mass ratio in a dry state from the viewpoint of thermal conductivity and strength development, and more preferably 20 to 40% when used as a heat insulating material. When using, 10 to 20% is preferable.

  In addition to the essential raw materials, for example, waste materials of the porous molded body according to the present invention, residual cutting materials, and powders such as abrasive powders may be reused as raw materials. However, the amount of the whole raw material is preferably 50% or less in terms of mass ratio in a dry state. If it exceeds 50%, the strength of the resulting porous molded body may be insufficient.

  The porous molded body of the present invention is characterized in that it is obtained by molding the above raw material and curing it without heating in the presence of ammonia. If only the raw material is cured, it is possible to intervene sodium hydroxide or lithium hydroxide, but when these are used, sodium and lithium remain in the porous molded body and are heated. Shrinkage rate increases and heat resistance decreases. Such a phenomenon does not occur when ammonia is used.

Ammonia is preferably added to the raw material as a solution.
The addition amount of ammonia is a mass ratio with respect to amorphous silicic acid, and amorphous silicic acid / ammonia = 99.5 / 0.5 to 50/50, more preferably 99.5 / 0.5 to 70/30. If the ratio of ammonia is below the above, amorphous silicic acid cannot be sufficiently cured, and sufficient performance as a porous molded body cannot be obtained. An ammonia ratio exceeding the above is not preferable because unreacted ammonia remains in the porous molded body and generates malodor. However, there is no particular problem on the physical properties of the molded body.
The concentration of the ammonia solution is not particularly limited, but when the concentration is high, it corresponds to a deleterious substance. Therefore, it is preferably diluted to 5 to 30% with water or alcohol.

  The ammonia solution may be added to the raw material while mixing the raw materials, or the ammonia solution may be added and mixed again after first mixing the raw materials. In addition, when using the papermaking method as a forming method, the raw material slurry mixed with water added to the raw material is made into a thin film, wound up on a making (forming) roll until it reaches a predetermined thickness, and taken out from the making roll. It is better to spray the ammonia solution on the thin film before winding it on the making roll.

The molding method is not particularly limited, and a known method such as a mold pressing method, a papermaking method (above), or an extrusion molding method may be used.
After molding, no particular heating or the like is required, and it can be cured by simply leaving it at room temperature. In the case of a molding method that does not require much water, such as a mold press method or an extrusion molding method, the minimum strength as a product can be obtained when the molding is completed. In the case of a molding method that requires a large amount of water, such as a papermaking method, the minimum strength as a product can be obtained by performing dehydration after molding. In addition, if a curing time is provided, the strength can be further increased, and the strength is also increased during the steps after the molding step without particularly providing the curing time. Here, heating or the like is not necessary, which means that no special heating is performed, and a raw material slurry (raw material is used for the purpose of improving the production efficiency when forming by a normal manufacturing method such as a papermaking method. Heating and water drying treatment for adjusting the moisture content at the time of shipment performed after curing. Therefore, the curing temperature in the present invention is preferably 5 to 40 ° C, particularly 10 to 30 ° C.

  The cured porous molded body is dried in order to keep the moisture content constant and to remove residual ammonia, moisture and organic solvent (alcohol). The drying method is not particularly limited, but usually heat drying at about 105 ° C. is used. In addition, when ammonia is removed by heat drying, the strength of the porous molded body does not increase any more.

The resulting porous molded body has excellent strength despite being porous and lightweight. When used as a heat insulating material, the preferred density is 250 to 400 kg / m ³ and the bending strength is 20 to 50 N / cm ² . Moreover, when using as a building material, a preferable density is 650-750 kg / m < ³ > and bending strength is 10-15 N / mm < ² >. Moreover, there is little heat shrinkage. It also has excellent heat insulation.

  EXAMPLES Next, although an Example is given and this invention is demonstrated further in detail, this invention is not limited to these Examples.

Examples 1-7 and Comparative Examples 1-4
The raw materials listed in Tables 1 and 2 were weighed and dry mixed with a Henschel mixer at 1500 rpm for 3 minutes. Next, 30% ammonia water was sprayed into the Henschel mixer and mixed for another 1 minute. The mixed raw material was put into a mold, pressure-molded with a press pressure of 1.5 to 2.5 MPa, and cured and cured under predetermined curing conditions to produce a porous molded body.

The density, bending strength, thermal conductivity, and linear shrinkage rate of the obtained porous molded body were measured.
(Density) Based on 6.6 of JIS A 9510.
(Bending strength) Based on 6.7 of JIS A 9510.
(Thermal conductivity) Based on the hot wire method of JIS R 2616 (equipment in section 3.5, test piece in section 4.2, operation in section 5.3).
(Linear shrinkage) Based on 6.9 of JIS A 9510.

  From Table 1 and Table 2, Examples 1-7 porous molded bodies have excellent hardness, excellent thermal conductivity, and small thermal shrinkage, despite being cured without heating. It is useful as a heat insulating material. On the other hand, Comparative Examples 1 to 3 using an alkali hydroxide exhibit strength but have large heat shrinkage and are difficult to apply as a heat insulating material.

Examples 8-14
Using the raw materials described in Table 3, porous molded bodies were produced in the same manner as in Examples 1 to 7 except for the conditions described in the table. The density and bending strength of the obtained molded body were measured in the same manner as in Examples 1-7. The dimensional change rate was measured according to 5.8 of JIS A 5430.

  From Table 3, the porous molded bodies of Examples 8 to 14 have excellent bending strength and a small dimensional change rate, and are useful as general building materials such as interior materials.

  Although the presence or absence of the generation | occurrence | production of the crack by dropping a water drop and making it absorb water was visually observed with respect to Examples 1-14, generation | occurrence | production of the crack was not recognized about any Example.

Claims (5)

  A porous molded body obtained by molding and curing a raw material containing amorphous silicic acid, a reinforcing fiber, and a filler, which is cured without heating in the presence of ammonia. .   The porous molded body according to claim 1, wherein the ammonia is aqueous ammonia.   The porous molded body according to claim 1 or 2, wherein the curing temperature is 5 to 40 ° C.   A method for producing a porous molded body comprising dehydrating and curing a slurry containing amorphous silicic acid, reinforcing fibers, a filler, and ammonia without heating.   The manufacturing method of the porous molded object of Claim 4 whose curing temperature is 5-40 degreeC.