JP7143135B2 - insulation - Google Patents

Description

TECHNICAL FIELD The present invention relates to a heat insulating material that can be filled in an airtight space.

Conventionally, silica airgel particles have been known (well-known) as the heat insulating material.

The silica airgel described above has a network-like fine structure, has pores of less than 10 nm between skeletons, and has a three-dimensional fine porous structure, so it exhibits excellent heat insulation, It has a melting point of 1200°C and has the advantage of being used for heat insulation in high temperature environments.
In addition, it is known that there is a material that is fragile in bending but has the strength to support 2000 times its own weight.
However, there is a demand for a material with even higher heat insulation performance.

SUMMARY OF THE INVENTION Accordingly, it is an object of the present invention to provide an insulating material having the properties of silica airgel but with lower thermal conductivity.

A first characteristic configuration of the present invention is a heat insulating material that can be filled in an airtight space, and is a mixture of silica airgel powder and titanium oxide powder having an average particle size smaller than that of the silica airgel powder. The silica airgel particles have an average particle size of 0.01 to 1.2 mm, and the titanium oxide particles have an average particle size of 7 nm.

According to the first characteristic configuration of the present invention, by mixing the silica airgel powder and the titanium oxide powder having an average particle diameter smaller than that of the silica airgel powder, the thermal conductivity of both is can also provide lower insulation.

By adding and mixing titanium oxide powder particles with an average particle size of 7 nm to silica airgel with an average particle size of 0.01 to 1.2 mm, the thermal conductivity is surely lower than when each is used alone. .
Therefore, it is possible to provide a heat insulating material with better heat insulating properties.

4 is a graph showing changes in thermal conductivity when silicon carbide is added to silica airgel. 4 is a graph comparing changes in thermal conductivity at low temperatures between silica airgel alone and silica airgel mixed with silicon carbide. 4 is a graph comparing changes in thermal conductivity at high temperatures between silica airgel alone and silica airgel mixed with silicon carbide.

An embodiment of the present invention will be described below with reference to the drawings.
For example, in order to form an airtight space within the wall thickness of an insulated container surrounding the space containing the object to be insulated, or a heat insulating material that can be filled in the airtight space of a vacuum heat insulator, an average particle size of 0.01 to 4.0 mm is required. and a silicon carbide powder having an average particle diameter of 2 μm.
Then, the heat insulating material has a mass ratio of the silicon carbide powder to the silica airgel powder 100 that is greater than 0 and less than 110, so that when only the silica airgel powder is used Also, the thermal conductivity is lower than in the case of only silicon carbide particles, which is shown by the following experimental results.

[Experiment 1]
Silica airgel has a network-like fine structure, has pores of less than 10 nm between skeletons, and has a three-dimensional fine porous structure, so it exhibits excellent heat insulation and has a melting point. At 1200° C., four types of samples were prepared as shown in Table 1 as particle sizes.

From Table 1, silica airgel particles with a particle size of 0.01 to 1.2 mm had the lowest thermal conductivity of 0.0198 W/mK.

[Experiment 2]
Using the silica airgel granules of Sample 2, changes in thermal conductivity were investigated when the addition ratio of the silicon carbide granules to 100 parts by mass of silica airgel was changed.

When Table 2 is graphed, it becomes as shown in FIG. 1, with respect to 100 parts by mass of silica airgel powder, 15 to 25 parts by mass of silicon carbide powder with an average particle size of about 2 μm (distribution is 1 to 5 μm). It is clear that the rate of decrease in thermal conductivity is higher in mixtures to which is added than other addition ratios.
Incidentally, the thermal conductivity of silicon carbide powder (SiC) alone is 0.0774 W/mK.

[Experiment 3]
Next, as silica airgel granules with different particle sizes, the average particle size of about 2 μm (distribution 1 to 5 μm) silicon carbide granules (SiC) are added at a rate of 20 parts by mass, respectively, and mixed, the measured bulk density (kg/m ³ ) and the thermal conductivity at an average temperature of 23 ° C. (W/mK) was measured and shown in Table 3.

From Table 3, it can be seen that in each of Samples 1 to 4, the thermal conductivity is lowered by adding and mixing silicon carbide particles (SiC) having an average particle size smaller than that of silica airgel particles.

[Experiment 4]
Next, the low-temperature characteristics (-40°C to 40°C) of each of the silica airgel powder alone and the heat insulating material in which silicon carbide powder (SiC) is mixed into the silica airgel powder were examined. Indicated.

It should be noted that Table 4 is represented as a temperature graph as shown in FIG.
That is, it can be seen that the thermal conductivity is lower when the silicon carbide particles are mixed than when the silica airgel particles are mixed alone, and the rate of reduction increases as the temperature rises.

[Experiment 5]
High-temperature characteristics (100° C. to 500° C.) were examined for each of the silica airgel powder alone similar to the above and the heat insulating material in which silicon carbide powder was mixed into the silica airgel powder, and the results are shown in Table 5. .

FIG. 3 shows Table 5 as a temperature graph.
In other words, it is clear that the higher the temperature, the greater the difference in thermal conductivity of the silica airgel particles mixed with silicon carbide than the silica airgel particles alone, and the higher the heat insulating properties.

[Another embodiment]
Other embodiments will be described below.
<1> Since silicon carbide powder is generally used as an infrared transmission inhibitor, titanium oxide powder having similar properties (average particle size is about 7 nm) is used as silica airgel powder. Table 6 shows whether or not the thermal conductivity is lowered even when the particles are added and mixed in a particle size of 0.01 to 1.2 mm.
For comparison, the experimental results when silicon carbide particles were added are also shown. In this experiment, it was found that, in addition to the silicon carbide powder, titanium oxide powder having an average particle size smaller than that of the silica airgel powder had a lower thermal conductivity than silica airgel alone. Entrained silica airgel granules can be used as thermal insulation.

Claims (1)

A heat insulating material that can be filled in an airtight space,
Silica airgel granules and titanium oxide granules having an average particle diameter smaller than that of the silica airgel granules are mixed, and the silica airgel granules have an average particle diameter of 0.01 to 1.2 mm, and the A heat insulating material comprising titanium oxide particles having an average particle size of 7 nm.

Images