JP2010235691A - Coated porous inorganic particle and molded article using the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a molded article exhibiting both excellent insulating property and strength. <P>SOLUTION: The particle is made by coating the surface of a porous aggregate of silicic acid calcium hydrate crystal with a thermosetting resin, and the molded article is obtained by using the same. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to coated porous inorganic particles useful as a raw material for a heat insulating material and the like, and a molded body using the same.

  Calcium silicate compacts are widely used as building materials because they are excellent in fire resistance, heat insulation and strength. An important characteristic of a calcium silicate molded body is excellent heat insulation, and it is widely used not only for building materials but also for equipment and piping of each device in an industrial plant.

  Conventionally, in thermal insulation applications, it has been common to increase the porosity of a material by adding porous inorganic particles having a low bulk density to the matrix, and to lower the thermal conductivity by reducing the specific gravity. It was. However, if the porosity is increased in order to increase the heat insulation, the material becomes brittle and the strength is lowered, so there is a limit.

  As a technique for improving heat insulation, a highly heat-insulated molded body in which organic foam beads foamed with a gas having low thermal conductivity are contained in a calcium silicate hydrate crystal is already known (patent document). 1). However, since this molded body is a mixed molding of calcium silicate hydrate crystals and organic foam beads, non-uniform dispersion and dropping of the organic foam beads occur, resulting in partial performance degradation and silicic acid. Since the ratio of the calcium hydrate crystal is high, there is also a problem in the strength brittleness of the molded body.

On the other hand, as means for reducing the thermal conductivity of the constituent material, there are vacuum microcapsules and a heat insulating material using the same (Patent Document 2). However, since this heat insulating material has a limit in capsule strength and has a problem in strength when used alone, it is necessary to protect the capsule with a wall having a gas sealing property for reinforcement.
In addition, a zonotlite-reinforced polypropylene composition (Patent Document 3) in which a resin is reinforced with zonotlite, which is a porous inorganic particle, has been reported. In the present invention, the effect of enhancing the strength can be obtained by mixing the zonotlite with the resin. However, since most of the composition occupies the resin, there is a drawback that low thermal conductivity cannot be obtained.

JP-A-8-109079 JP 2002-128906 A JP 10-36598 A

  The subject of this invention is providing the molded object which made the outstanding heat insulation and intensity | strength compatible.

  Therefore, the present inventor has made various studies to improve the heat insulating property and strength of the calcium silicate molded body, but not the density of the molded body and the size of the calcium silicate hydrate crystals, but the calcium silicate hydrate crystals. Attention was paid to the porosity of the aggregate. Rather than using the aggregate of calcium silicate hydrate crystals as it is, if the surface is coated with a thermosetting resin in the form of particles, porous particles with independent pores inside can be obtained. As a result, it has been found that if the porous particles are molded, a molded body having both excellent heat insulating properties and strength can be obtained, and the present invention has been completed.

That is, the present invention provides particles in which the surface of a porous aggregate of calcium silicate hydrate crystals is coated with a thermosetting resin.
Moreover, this invention provides the molded object obtained by shape | molding the composition containing the said coating particle.

  Since the coated particles of the present invention have fine independent pores inside and have high strength, the thermal conductivity of a molded product obtained by molding the coated particles decreases. Accordingly, a molded body formed using the coated particles of the present invention has excellent heat insulation properties and high strength, and is useful as a heat insulating material in the building material field, plant field, and the like.

It is a figure which shows the carbon analysis result of the scanning electron micrograph (upper stage) of the cross section of a zonotlite particle, and the cross section. It is a figure which shows the scanning electron micrograph (upper stage) of the cross section of the covering xonotlite particle | grains of this invention, and the carbon analysis result of the cross section. It is a figure which shows the pore distribution of a zonotlite particle. It is a figure which shows the pore distribution of the covering xonotlite particle | grains of this invention.

The coated particles of the present invention are particles in which the surface of a porous aggregate of calcium silicate hydrate crystals is coated with a thermosetting resin. Calcium silicate hydrate crystals can be produced by a conventional method, for example, by hydrothermal reaction of a silicate raw material and a calcareous raw material dispersed in water. A typical siliceous raw material is quartzite powder, and a typical calcareous raw material is slaked lime or quicklime. Typical calcium hydrate crystals are zonotlite and tobermorite. When producing zonotrite, the molar ratio (C / S) of the CaO component to the SiO ₂ component of the raw material is 0.9 to 1. 3 and mixed and stirred at a water / solid content ratio (mass ratio) of 10 to 35, and subjected to a hydrothermal reaction in an autoclave at 170 to 210 ° C. and a saturated steam pressure of 0.8 to 2.0 MPa for 4 to 20 hours. Can be manufactured. Moreover, when manufacturing a tobermorite, C / S shall be 0.3-1.2, and it stirs and mixes by water / solid content ratio (mass ratio) 8-25, and is 140-210 degreeC, 0.4 in an autoclave. It can be produced by a hydrothermal reaction for 1 to 12 hours under a saturated water vapor pressure of ˜2.0 MPa.

  The type of calcium silicate hydrate crystals is not particularly limited, but representative examples include the above-mentioned zonotlite and tobermorite. In the present invention, zonotrite is more preferable from the viewpoint of heat resistance. The porous aggregate of acicular xonotlite crystals can be obtained by stirring during the hydrothermal reaction.

From the viewpoint of porosity, the porous aggregate of calcium silicate hydrate crystals preferably has a BET specific surface area of 40 m ² / g or more by nitrogen adsorption. In addition, the porous aggregate of calcium silicate hydrate crystals has a pore size of 0.01 to 0.30 μm, particularly 0, from the viewpoint of lowering the thermal conductivity of the obtained molded product and ensuring good heat insulation. It is preferable to have pores of 0.01 to 0.06 μm. The presence or absence of pores and the pore diameter can be determined and measured by a pore distribution by nitrogen adsorption and a scanning electron microscope.

  The particle diameter of the aggregate of calcium silicate hydrate crystals is preferably 30 to 130 μm, particularly preferably 30 to 80 μm. This particle size can be measured by a laser diffraction type particle size distribution measuring machine.

  Examples of the thermosetting resin that is a coating material for the coated particles in the present invention include epoxy resins, melamine resins, phenol resins, urethane resins, and unsaturated polyester resins. Among these, epoxy resins are mechanical properties and heat resistance. From the viewpoint of water resistance, moisture resistance and water resistance.

  The content (coating amount) of the thermosetting resin in the coated particles of the present invention is preferably 15 to 50% by mass, particularly 30 to 50% by mass in the coated particles. If the content of the thermosetting resin is small, sufficient effect of reinforcing particles cannot be obtained. If the content is too large, the effect of solid heat transfer becomes large, and the effect of reducing thermal conductivity becomes insufficient.

  The means for coating the thermosetting resin is not particularly limited, and the thermosetting resin-containing liquid may be uniformly adhered to the surface of the porous aggregate particles and then cured. More specifically, the curing agent is uniformly attached to the surface of the porous aggregate particles (dispersion liquid), and on the other hand, a uniform solution of the thermosetting resin is prepared, and the porous aggregate is added to the uniform solution. It can be obtained by adding the aggregated particle dispersion and causing a curing reaction on the surface of the porous aggregate particles. In more detail, after the porous aggregate particles are immersed in a solution in which a curing agent is dissolved, particles that carry the solution inside the particles or particles in which only the solvent is removed by evaporation are prepared, and the obtained porosity After adding and mixing the aggregate particles in the oil phase in which the thermosetting resin and the surfactant are dissolved, the temperature is raised to a predetermined temperature while stirring, and a curing reaction is performed for a predetermined time. The obtained oil phase which is the coated particle dispersed phase is washed and replaced with a solvent, and the solvent is removed by drying to obtain a powder of coated particles.

The obtained coated particles of the present invention preferably have substantially the same pores as the raw material particles inside the particles. That is, it is preferable that the coated particles have independent pores of 0.01 to 0.30 μm, and further 0.01 to 0.06 μm. Moreover, it is preferable that the BET specific surface area by nitrogen adsorption is 5-30 m < ² > / g, especially 5-15 m < ² > / g.

  Since the surface of the coated particle of the present invention is coated with a thermosetting resin, the strength is improved, and it is preferable to have a compressive fracture load of 3 to 7 mN, particularly 5 to 7 mN. Here, the compressive fracture load can be measured by a micro compression tester.

The total calorific value of the obtained coated particles of the present invention is preferably 8.0 MJ / m ² or less from the viewpoint of nonflammability. Here, the calorific value can be measured by a differential scanning calorimeter.

  Since the coated particles of the present invention have fine independent pores inside the particles and are coated with a thermosetting resin, the strength is remarkably improved. Accordingly, a molded product obtained by molding the composition containing the coated particles is useful as a heat insulating molded product because it has excellent heat insulating properties and excellent strength.

  As a raw material for the molded article of the present invention, for example, calcium silicate hydrate crystals, fibers, fillers and the like can be used in addition to the coated particles of the present invention. 20 to 70 parts by mass of calcium silicate hydrate crystals, 1 to 10 parts by mass of fibers, and 10 to 50 parts by mass of filler can be added to 100 parts by mass of the coated particles of the present invention.

  Examples of the fiber include glass fiber, carbon fiber, vinylon fiber, rock wool, and the like, and examples of the filler include calcium carbonate, silica sand, and clay. Furthermore, the surface can be modified by applying an inorganic or organic paint to the surface of the molded body.

Examples of the molding method include compression molding using a dry or wet press. The thermal conductivity of the obtained molded article of the present invention is 0.03 to 0.07 W / m · K when, for example, a molded article having a bulk density of 0.30 to 0.50 g / cm ³ is used.
Here, the thermal conductivity can be measured by an unsteady hot wire method, a laser flash method, or the like.

Furthermore, the bending strength of the present invention formed body, 0.1~0.5N / mm ^2, is preferably particularly 0.3 to 0.5 N / mm ^2.

  Next, an Example and a comparative example are given and this invention is demonstrated in detail.

The physical properties of the particles described in the following examples and comparative examples were evaluated according to the following methods.
(1) Particle cross-sectional composition analysis The cross-section of a particle is analyzed with a scanning electron microscope and an energy dispersive X-ray analyzer.
(2) Measurement of particulate organic content The organic mass contained in the particles is measured with a differential thermothermal gravimetric simultaneous measurement device.
(3) Measurement of particle calorific value A particle calorific value is obtained from a differential scanning calorimeter.
(4) Measurement of particle compressive fracture load The particle's compressive fracture load is measured with a micro compression tester.
(5) Measurement of particle thermal conductivity Particles are molded by a dry press, and the thermal conductivity is determined by a laser flash method thermal constant measuring device or a hot wire method thermal conductivity measuring device.
(6) Measurement of specific surface area of particles The specific surface area of particles is determined by a BET specific surface area measuring device by nitrogen adsorption.
(7) Measurement of particle pore size distribution The particle pore size distribution is determined with a BET specific surface area measuring device by nitrogen adsorption.

Example 1
(1) Production of Zonotolite Particles 322.0 g of quick lime (manufactured by Taiheiyo Cement Co., Ltd., CaO purity 96.2%) as a calcareous raw material, and silica 70 (manufactured by Tsuruga Cement Co., Ltd., SiO purity 96.3) as a siliceous raw material %) 344.6 g was added to 10 kg of water heated to 60 ° C. with stirring. After stirring for 5 minutes, transfer to a stirring autoclave with an internal volume of 17 L. While stirring at a rotation speed of 300 rpm of the stirrer, the temperature is constantly raised to a holding temperature of 204 ° C. over 2 hours and 30 minutes, and then the rotation speed is reduced to 230 rpm. The hydrothermal synthesis reaction was carried out by holding at a holding temperature of 204 ° C. for 6 hours and 30 minutes. Thereafter, it was allowed to cool naturally over 12 hours to obtain a zonotlite slurry.
Subsequently, the zonotlite slurry was subjected to suction dehydration filtration, and the cake-like filtrate was dried at 105 ° C. for 24 hours to obtain zonotrite particle crystals having an average particle diameter of 70 μm.

(2) Production of coated zonotlite particles 4.0 g of zonotrite particles are immersed in 20 g of ethanol in which 4.0 g of imidazole, which is a curing agent for epoxy resin, is dissolved, and a dispersion of particles carrying the ethanol solution inside the particles is prepared. .
Subsequently, 520 g of corn oil (manufactured by Wako Pure Chemical Industries, Ltd.) was charged into a 1 L flask, and then 8 g of epoxy resin JER815 (manufactured by Japan Epoxy Resin Co., Ltd.) and a surfactant Span 80 (Wako Pure Chemical Industries, Ltd.). )) 6.0 g was added and heated to 80 ° C. to dissolve. While the solution was stirred, the above dispersion was dropped and mixed, and a curing reaction was performed for 6 hours to obtain an oil phase in which the coated zonotolite particles were dispersed.
Subsequently, the oil phase was washed and replaced with hexane, and then dried at 80 ° C. for 24 hours to obtain coated zonotlite particles.

Examples 2-3
Coated xonotlite particles produced in the same manner as in Example 1 except that the amount of epoxy resin was changed in the production of coated zonotlite particles. The physical property test results of the particles are shown in Table 1. As for the thermal conductivity, a sample for measurement was obtained by press-molding particles to a bulk density of 0.3 g / cm ³ .

Comparative Example 1
The zonotrite particles obtained in Example 1 (1) were referred to as Comparative Example 1. The physical property test results of the particles are shown in Table 1. As for the thermal conductivity, a sample for measurement was obtained by press-molding particles to a bulk density of 0.3 g / cm ³ .

  From the examples and comparative examples described above, the coated zonotolite particles provided by the present invention are low exothermic, compatible in strength, and low thermal conductivity, which cannot be achieved by conventional zonotolite particles or polymers alone. It is possible to obtain

  Scanning electron micrographs of the cross sections of the particles of Comparative Example 1 and Example 3 are shown in FIGS. As is clear from the comparison between FIG. 1 and FIG. 2, the coated particles of the present invention have 0.01 to 0.30 μm of independent pores in the interior thereof, and carbon is detected on the surface, and the carbon is derived from the resin. From this, it can be seen that it is coated with a thermosetting resin.

  Moreover, the pore distribution of the particle | grains of the comparative example 1 and Example 3 is shown in FIG.3 and FIG.4. As apparent from FIG. 3 and FIG. 4, since the pores of 0.002 to 0.030 μm were greatly reduced on the surface of the coated particle of the present invention, the particle surface was coated with a thermosetting resin. It is presumed that independent holes remain inside.

Claims (8)

  Particles in which the surface of a porous aggregate of calcium silicate hydrate crystals is coated with a thermosetting resin.   2. The coated particle according to claim 1, wherein the crystal of calcium silicate hydrate is a needle-like zonotlite crystal.   The coated particle according to claim 1 or 2, wherein the content of the thermosetting resin is 15 to 50% by mass in the coated particle. The coated particle according to any one of claims 1 to 3, which has a BET specific surface area of 5 to 30 m ² / g by nitrogen adsorption and has 0.01 to 0.30 µm of independent pores inside the coated particle.   The coated particle according to any one of claims 1 to 4, which has a compressive fracture load of 3 to 7 mN. The coated particles according to claim 1, which have a thermal conductivity of 0.03 to 0.07 W / m · K when formed into a compact having a bulk density of 0.30 to 0.50 g / cm ³ .   The molded object obtained by shape | molding the composition containing the coating particle of any one of Claims 1-6.   The molded body according to claim 7, which is a heat insulating molded body.