JP5466801B2 - Inorganic hollow fine particles - Google Patents

Description

The present invention relates to an inorganic hollow fine particle having partition walls in internal voids made of closed cells, and more specifically, the voids made of closed cells inside the particles are separated by the partition walls, and is lightweight and remains floating under hydrostatic pressure. It relates to inorganic hollow fine particles having a high rate.

Perlite has been conventionally known as a hollow lightweight body produced from natural glassy rock. Perlite is a hollow body made by heating particles such as pearlite and obsidian at a high temperature of 900 to 1300 ° C and foaming moisture, and is widely used for lightweight aggregates, building materials, heat insulating materials, soil improvement materials, etc. It is used.

Conventional pearlite has a problem that if a raw material containing a large amount of water of crystallization is used, the surface becomes porous, resulting in high water absorption, making it unsuitable for lightweight aggregates. In view of this, a low water-absorbing pearlite having a large number of bubbles formed inside and an outer shell that closes the opening of the bubbles has been developed (Patent Document 1: Japanese Patent Application Laid-Open No. 2008-19149).

Also, when heating and foaming raw rocks such as pearlite and obsidian, preheating is performed at a temperature lower than the softening point of the raw rock to avoid the formation of many open bubbles due to sudden foaming of moisture. After that, spherical pearlite is known in which the water absorption rate is lowered by foaming and firing at a high temperature to form closed pores (Patent Document 2: Japanese Patent No. 3528390).

The hollow particles (low water-absorbing pearlite) of Patent Document 1 are described as having a low water absorption and a floating rate of 80% because they have an outer shell that closes the opening of bubbles. Since these hollow particles have a large number of internal bubbles, the floating rate under normal pressure is high. However, since the internal bubbles are continuous bubbles and not independent bubbles (although there are partition walls in the internal space, the bubbles communicate with each other). If the outer shell is cracked, water penetrates the entire interior of the particle through the communicating bubbles. For this reason, there is a problem that the levitation rate in pressurized water is significantly reduced.

The hollow particles (spherical pearlite) of Patent Document 2 have low water absorption because the internal bubbles are not open on the particle surface, but in many cases, the internal space of the particles is formed by large single bubbles, and the internal space Is not divided, the crushing strength is low, and cracks are likely to occur on the particle surface. Further, when cracks occur on the surface, the particles are easily filled with water. For this reason, the levitation rate under pressurized water is significantly reduced.

Conventional hollow fine particles are shown in FIGS. The example shown in the figure is a hollow fine particle commercially available under the trade name of Esfires, the inside of the particle is formed by large single bubbles, and there are no partition walls in the internal space.

JP 2008-19149 A Japanese Patent No. 3528390

The present invention solves the above-mentioned problems in conventional hollow particles (such as pearlite), and provides inorganic hollow fine particles that are lightweight but have a high crushing strength and a remarkably high buoyancy remaining under pressure.

The present invention relates to inorganic hollow fine particles that have solved the above-described problems by the following constitution.
[1] Silica fine particles formed by heating and foaming having an average particle diameter of 5 to 200 μm, wherein the internal space of the particles is divided by partition walls, and the internal space is formed by a plurality of closed cells, and the weight is 0 An inorganic hollow fine particle characterized by .16 to 0.35 g / cm ³ and an 8 MPa hydrostatic pressure levitation residual ratio of 50% or more .

[2] The inorganic hollow fine particles as described in [1] above, having an average particle size of 20 to 100 μm, a compressive strength of 15 MPa or more, and a water absorption of 3% or less.
[3] The inorganic hollow fine particles according to the above [1] or [2], comprising 60 or more particles out of 100 particles having an internal space formed by a plurality of closed cells separated by partition walls.

The inorganic hollow fine particles of the present invention have an appropriate average particle size and porosity, so that they are lightweight and have a high floating rate in water. Further, since the internal space of the particles is partitioned by the partition walls, the compressive strength is high, and cracks are not easily generated even under pressure. Furthermore, since the internal space is formed by a plurality of closed cells separated by partition walls, the range in which water penetrates is limited even if a partial crack occurs. Therefore, the buoyancy remaining rate in water after pressurization is remarkably high.

Scanning electron micrograph of the hollow fine particles of the present invention Schematic sectional view of the hollow fine particles of the present invention Micrograph showing the appearance of commercially available hollow fine particles Photomicrograph of a part of commercially available hollow fine particles cut out A graph showing the change in the floating rate according to the change in hydrostatic pressure

Hereinafter, the present invention will be specifically described based on embodiments.
The hollow fine particles of the present invention are siliceous fine particles obtained by heating and foaming with an average particle diameter of 5 to 200 μm, and the internal spaces of the particles are divided by partition walls, and the internal spaces are formed by a plurality of closed cells. An inorganic hollow fine particle characterized by a weight of 0.16 to 0.35 g / cm ³ and an 8 MPa hydrostatic pressure levitation residual rate of 50% or more .
It is.

A photomicrograph of the inorganic hollow fine particles according to the present invention is shown in FIG. 1, and a schematic cross section is shown in FIG. As shown in the figure, in the hollow fine particle 10 of the present invention, the internal space 11 of the particle is divided into a plurality of spaces 11 by partition walls 12, and each internal space 11 is separated by the partition walls 12 and does not communicate with each other (closed cells). It is formed by. The closed cells are preferably bubbles having no opening on the particle surface (referred to as closed cells).

Since the hollow fine particles of the present invention are formed by closed cells that are separated from each other by the partition walls and do not communicate with each other, the range in which water penetrates is limited even if partial cracks occur. Is a closed cell that does not open on the particle surface, and therefore has a high hydrostatic pressure levitation residual rate under pressure. The hydrostatic levitation survival rate is the ratio of the underwater buoyancy rate W2 under normal pressure after pressurization of particles pressurized under hydrostatic pressure to the underwater levitation rate (floating rate) W1 under normal pressure without pressure [the buoyancy remaining rate = W2 / W1 × 100 (%)].

Specifically, the hollow fine particles of the present invention have, for example, a residual levitation rate of 8 MPa under hydrostatic pressure of 50% or more, preferably 60% or more, more preferably 70% or more. Those having a buoyancy remaining rate of less than 50% have a low particle strength and a small proportion of the internal space of the particles formed by closed cells.

In addition, the hollow fine particles of the present invention are preferably closed bubbles in which the closed cells do not open on the particle surface, and thus have a significantly low water absorption rate. Specifically, for example, the water absorption under normal pressure is 3% or less, preferably 1.5% or less.

In the hollow fine particles of the present invention, the fact that the internal space of the particles is formed by closed closed cells means, for example, that the residual rate of levitation under 8 MPa hydrostatic pressure is 50% or more, preferably further water absorption The rate is 3% or less.

In the inorganic hollow fine particles of the present invention, it is preferable that there are two or more partition walls in the internal space. By having a plurality of partition walls, the strength of the particles is further improved. Specifically, for example, the compressive strength is 15 MPa or more. Therefore, when manufacturing a lightweight mortar, since the hollow microparticles of the present invention have a high strength, the mortar can be reduced in weight without breaking even when mixed with the mortar, and the strength of the mortar is not lowered. In the case of manufacturing lightweight mortar, those in which hollow fine particles are fragile must use a large amount of hollow fine particles, and workability and the like may deteriorate due to broken particles and fragments thereof.

The hollow fine particles of the present invention are lightweight because they have a large space inside the particles. Specifically, for example, the weight is 0.16 to 0.35 g / cm ³ . If the weight is less than 0.16 g / cm ³ , the thickness of the shell and partition walls will be reduced, and the strength will be weakened. If it exceeds 0.35 g / cm ³ , there will be many unfoamed particles, which is not preferable.

The hollow fine particles of the present invention preferably have an average particle size in the range of 5 to 200 μm, more preferably 20 to 100 μm. If the average particle diameter of the particles is less than 5 μm, the particles tend to aggregate, which is not preferable. On the other hand, if the average particle size is smaller than 5 μm, it is difficult to produce particles having partition walls in the internal space. On the other hand, when the average particle size of the particles exceeds 200 μm, for example, when used in a paint, the smoothness of the paint surface is reduced, and when the space volume ratio and the number of partition walls are approximately the same, the surface area becomes weak as the specific surface area decreases. It is not preferable because it tends to become.

Moreover, in the hollow fine particles of the present invention, the residual levitation rate (under 8 MPa hydrostatic pressure) tends to differ depending on the difference in average particle diameter. Specifically, as shown in Table 1 of the Examples, when the hollow fine particles A3 and A4 having a volume of 0.2 g / cm ³ are viewed, the buoyancy remaining rate of A3 (average particle size 98 μm) is 80%. A4 (average particle size 179 μm) levitation residual is 60%. Further, regarding the hollow fine particles A7 and A8 having a volume of 0.25 g / cm ³ , the levitation remaining rate of A7 (average particle size 101 μm) is 90%, but the levitation remaining rate of A8 (average particle size 199 μm) is 55%. %. From this, it can be seen that the hollow fine particles of the present invention preferably have an average particle diameter of 20 to 100 μm at a weight of 0.16 to 0.35 g / cm ³ .

The hollow fine particles of the present invention are siliceous natural vitreous rocks such as shirasu, pearlite, obsidian, and pine sebite, preferably natural vitreous rocks having a silica content of 70% by mass or more, and an average particle size of 150 μm or less, more preferably 100 μm. By crushing and heating the rock fine particles to 900 ° C. to 1500 ° C. to form hollow fine particles, and adjusting the heating and foaming conditions according to the type and components of the raw rock powder, the internal space becomes a partition wall. What is delimited by can be manufactured.

The hollow fine particles of the present invention are not limited to the natural glassy rocks, and can be produced by mixing a foaming raw material with rock powder, granulating and heating and foaming.

Since the hollow fine particles of the present invention are silica glassy particles having a large space inside, the internal space can be observed with an optical microscope, and it can be confirmed that the internal space has a partition wall. Note that the particle shape having such an inner wall is preferably spherical or nearly spherical. In addition, the hollow fine particles of the present invention may have 60 or more, more preferably 70 or more in 100 particles, each having a partition in the internal space.

As described above, the hollow fine particles of the present invention have a low water absorption rate because the internal space of the particles is formed by sealed bubbles having no openings on the surface. In addition, since it has a large internal space, it is lightweight, and since there are partition walls in the internal space, the strength of the particles is large, and cracking does not easily occur even under pressure. Furthermore, since this internal space is formed by a plurality of closed cells separated by a partition wall, the range of water penetration is limited even if partial cracking occurs, and the buoyancy remaining rate under pressurized water is remarkably high .

Therefore, the hollow fine particles of the present invention are suitable for pumping when, for example, they are mixed in a mortar or a solvent and used in a relatively large amount, and even if pumped, the hollow particles are not broken. In addition, since the hollow fine particles of the present invention have partition walls in the internal spaces of the particles, the strength of the particles is larger than particles consisting of a single space without the partition walls, so that they can be used for aggregates, heat insulating materials, building materials, etc. The strength of the member can be increased, and there is little particle breakage during movement and transportation, and handling is easy. Furthermore, a hollow state can be maintained when mixed with a slurry or the like.

On the other hand, even if there are partition walls in the internal space as in the conventional case, in the case where the internal bubbles communicate with each other, if the cracks partially occur, the water penetrates the entire interior of the particles, so Significantly lower and higher water absorption. Those with high water absorption cannot be reduced in weight when used in mortar aggregates. In addition, slump loss occurs when pumping and pumping becomes difficult.

  Hereinafter, the present invention will be specifically described by way of examples. The average particle diameter, the ratio of the partition wall particles, the volume, the uniaxial compressive strength, the hydrostatic levitation residual ratio, the buoyancy ratio, and the water absorption ratio were measured by the following methods.

[Average particle size]
Using a laser diffraction particle size distribution measuring device, measurement was performed with a measuring instrument (Microtrack) manufactured by Nikkiso Co., Ltd.
[Ratio of partition wall particles]
A small amount of sample particles are placed on the preparation, and ethanol is dropped therein to disperse the particles. This was observed with a light transmission type microscope, and the number of particles in which partition walls were visually observed with respect to 100 foamed particles was counted.

[Uniaxial compressive strength]
Uniaxial compressive strength is set in a stainless steel cylinder with an inner diameter of 15 mm and a height of 100 mm, and a cylindrical stainless steel jig with a height of 60 mm, which is slightly smaller than the inner diameter of the cylinder, is set at the bottom of the cylinder. The height is about 20 mm. From there, the same cylindrical stainless steel jig is placed and compressed by a uniaxial compression tester. The compression pressure at the time when the volume was reduced by 50% from the sample height before compression was measured at room temperature to obtain the uniaxial compression strength.

[Floating rate]
The floating rate is a volume ratio of the particles floating on the water surface to the total sample particles when the sample particles are immersed in water, and is a floating rate under normal pressure without pressurization. About 10 g of sample is placed in a 200 ml graduated cylinder, soaked in water, allowed to stand after sufficient agitation, allowed to stand until the water is no longer cloudy, and the volume Vb of the floated sample Va and the sinked sample is measured. The floating rate was calculated based on the formula of / (Va + Va) × 100.

[Weight]
A sample is filled into a container with a constant volume S (cm ³ ), the portion protruding from the opening is ground, the total weight G1 is measured, and the weight G2 of the container is subtracted from this to obtain the powder weight G3 (g). The powder weight G3 [G3 / S] g / cm ³ with respect to the volume S was defined as the volume.

[Water absorption rate]
About 200 g sample is put in a sufficient amount of water and left for 24 hours. This is naturally filtered through 5 types A filter paper. This is thinly and evenly spread on a watch glass, air-dried, a sample is taken, and the water absorption sample mass ma is measured. This is dried to a constant weight with a dryer at 105 ° C., and the dry sample mass mb is measured. The water absorption was calculated from the formula (ma−mb) / mb × 100.

[Remaining hydrostatic pressure levitation rate]
The sample is put into a pressurized container filled with water together with the sample container and pressurized at 1, 3, 4, 6, 8, 10 MPa for 1 minute. After pressurization, the entire amount of the pressurized sample is taken out under atmospheric pressure, placed in a graduated cylinder, and 200 ml of water is added and left to stand. When the turbidity of water disappears after standing, the volume of the floating sample particles is measured by a method according to the above method for measuring the floating rate, and is set as a pressurized floating rate (floating rate) W2 under a predetermined pressure. Sample particles of the same amount as the pressurized sample are measured by the same measurement method except that the sample particles are not pressurized and are at normal pressure, and are defined as a non-pressurized floating rate (floating rate) W1. The hydrostatic pressure levitation residual rate (%) was calculated based on the formula of pressurized sample buoyancy rate W2 / non-pressurized levitation rate W1 × 100.

[Examples A1 to A9]
Pearlite [chemical content (mass%) SiO ₂ 74%, Al ₂ O ₃ 13%, Fe ₂ O ₃ 1%, CaO 1%, MgO 0.1%, Na ₂ O 3.5%, K ₂ O 4.4%, ig .loss 2.2%] was pulverized, adjusted to an average particle size of 10 to 150 μm, fired at 1000 ° C. to 1100 ° C., and heated and foamed to produce hollow fine particles. These hollow fine particles are observed with an optical microscope, and those having partition walls in the internal space, having a capacity of 0.16 to 0.35 g / cm ³ and an average particle diameter of about 10 to 200 μm are selected, and the hydrostatic pressure levitation residual rate is determined. It was measured. In addition, the ratio of partition wall particles, water absorption, compressive strength, and floating rate were measured. These results are shown in Table 1 (Sample A1 to Sample A9). Moreover, the transition of the levitation remaining rate for A2, A3, and A7 is shown in FIG.

[Comparative Example 1]
Hollow fine particles having partition walls were produced in the same manner as in Examples, and particles (B1) having an average particle size of about 3 μm and particles (B2) having an average particle size of about 305 μm were selected, and the hydrostatic pressure levitation residual ratio was measured. . In addition, the ratio of partition wall particles, water absorption, compressive strength, and floating rate were measured. These results are shown in Table 2. Moreover, the transition of the levitation survival rate is shown in FIG.

[Comparative Example 2]
Percentage of partition wall particles for commercially available pearlite (pearlite-based heated foam particles) with a weight of 0.21 g / cm ³ , sample C1 with an average particle size of 210 μm, sample C2 with a weight of 0.21 g / cm ³ and an average particle size of 179 μm The residual levitation rate, the water absorption rate, the compressive strength, and the buoyancy rate were measured. The results are shown in Table 3. In addition, the same measurement was performed for commercially available soda-lime-based glass beads (having a single cell with no opening on the surface and no partition inside, and a void ratio of 85% by volume), and the results are shown in Table 3. Indicated.

Further, a commercially available pearlite hollow fine particle is reheated to 1000 ° C. in a rotary electric furnace, and the surface is melted to produce a hollow fine particle (internal bubbles communicated) described in Patent Document 1. (C4). Table 3 shows the volume, the average particle diameter, the ratio of the partition wall particles, the floating rate, the floating rate, the water absorption rate, and the compressive strength of the surface melt sample C4. FIG. 5 shows the transition of the levitation survival rate for samples C1 and C4.

As shown in Table 1, the hollow particles of the product of the present invention having an average particle size of 10 to 199 μm and a weight of 0.16 to 0.35 g / cm ³ , which are formed by closed cells in which the internal space is partitioned by partition walls, Except for sample A8, the buoyancy remaining rate under hydrostatic pressure of 8 MPa is 60% or more, the levitation remaining rate under hydrostatic pressure of 1 MPa to 6 MPa is small, and the buoyancy rate is high even under high pressure of hydrostatic pressure of 6 MPa to 8 MPa. Indicates.

On the other hand, as shown in Table 2, sample B1 having an average particle size exceeding 200 μm has a high buoyancy remaining rate under a hydrostatic pressure of 1 MPa to 2 MPa, but the buoyancy remaining rate at a hydrostatic pressure of 4 MPa or more rapidly decreases. The hydrostatic levitation survival rate under 8 MPa is significantly low at 25%. Sample B2 having an average particle diameter of 3 μm has a significantly low floating rate, indicating that there are many unfoamed particles. Furthermore, since the ratio of the number of partition wall particles in Sample B2 is small, when the shell is partially broken, water infiltrates the entire interior, so that the buoyancy remaining rate is drastically lowered even under a hydrostatic pressure of 1 MPa to 4 MPa.

As shown in Table 3, all of the conventional pearlite commercial products C1 to C2 have a sudden drop in the residual buoyancy at a hydrostatic pressure of 2 MPa or more. This indicates that water can easily penetrate into the entire particle even with a slight crack. In particular, the floating rate of the sample C3 having no partition particles at a hydrostatic pressure of 8 MPa is 1%, and most of the particles do not float.

In addition, the residual levitation rate at a hydrostatic pressure of 4 MPa or more also decreases sharply in Sample C4 in which the particle surface is remelted to close the surface opening. This is because the internal bubbles are connected, so if the particle surface is partially damaged, water will enter the entire inside of the particles through the connected bubbles, and at a hydrostatic pressure of 6 MPa or higher, the levitation rate is as low as that of sample C1. It is.

10-hollow particulates, 11-inner space, 12-partition, 13-outer shell

Claims (3)

Silica fine particles formed by heating and foaming having an average particle size of 5 to 200 μm, wherein the internal space of the particles is divided by partition walls, and the internal space is formed by a plurality of closed cells, and the weight is 0.16 to An inorganic hollow fine particle characterized by 0.35 g / cm ³ and an 8 MPa hydrostatic pressure levitation residual ratio of 50% or more . The inorganic hollow fine particles according to claim 1, wherein the average particle size is 20 to 100 µm, the compressive strength is 15 MPa or more, and the water absorption is 3% or less. The inorganic hollow fine particle according to claim 1 or 2, comprising 60 or more particles out of 100 having an internal space formed by a plurality of closed cells separated by partition walls.