US-12624227-B2 - Manufacturing method for thermal insulating material

Abstract

A manufacturing method for a thermal insulating material, including: an applying step of applying a coating liquid obtained by mixing aerogel particles, a water-soluble polymer having a hydrophobic group, and a liquid medium such that the aerogel particles are aggregated, with a coating means applying a pressure of 1.5 MPa or less to the coating liquid to obtain a coated film; and a removing step of removing at least a part of the liquid medium from the coated film to obtain a thermal insulating material.

Inventors

• Hiroyuki Izumi
• Kei TOGASAKI
• Hiroshi Yokota

Assignees

• RESONAC CORPORATION

Dates

Publication Date

20260512

Application Date

20210129

Priority Date

20200131

Claims (13)

1. 1 . A method for manufacturing a thermal insulating material, the method comprising: applying a coating liquid onto a substrate under a pressure of 1.5 MPa or less with a coater configured to exert the pressure on the coating liquid, to obtain a coated film, wherein the coating liquid is obtained by mixing aerogel particles, a water-soluble polymer having a hydrophobic group, and a liquid medium under conditions that cause aggregation of the aerogel particles and that result in the coating liquid having, when a diluted solution of the coating liquid is subjected to observation with an optical microscope, an area occupied by the aggregates having a diameter of 20 μm or more relative to an area occupied by the aerogel particles and the aggregates of the aerogel particles within an observation visual field of 50% or more; and removing at least a part of the liquid medium from the coated film to obtain the thermal insulating material.
2. 2 . The method according to claim 1 , wherein the coating liquid comprises aggregates of the aerogel particles, and an average diameter of the aggregates is 2 to 40 times an average diameter of the aerogel particles.
3. 3 . The method according to claim 1 , wherein a total content of the aerogel particles and aggregates of the aerogel particles in the coating liquid is 70 volume % or more on the basis of a total volume of solid contents.
4. 4 . The method according to claim 1 , wherein the water-soluble polymer comprises a cellulosic resin.
5. 5 . The method according to claim 1 , wherein a pore volume of the thermal insulating material is 0.15 cm 3 /g or more.
6. 6 . The method according to claim 1 , wherein the water-soluble polymer comprises a cellulosic resin having a long-chain alkyl group having 6 to 26 carbon atoms.
7. 7 . The method according to claim 1 , further comprising: mixing the aerogel particles, the water-soluble polymer, and the liquid medium at a stirring rate to form aggregates of the aerogel particles, wherein the stirring rate limits an average diameter of the aggregates to be 2 to 40 times an average diameter of the aerogel particles; and prior to applying the coating liquid onto the substrate, forming the coating liquid having the area occupied by the aggregates having the diameter of 20 μm or more relative to the area occupied by the aerogel particles and the aggregates of the aerogel particles within the observation visual field of 50% or more.
8. 8 . The method according to claim 7 , wherein the stirring rate is adjusted in accordance with a viscosity of the coating liquid to limit the average diameter of the aggregates.
9. 9 . The method according to claim 7 , wherein an additive is mixed with the aerogel particles, the water-soluble polymer, and the liquid medium to further limit the average diameter of the aggregates.
10. 10 . The method according to claim 9 , wherein the additive comprises at least one selected from the group consisting of a conditioner, a surfactant, a dispersant and an emulsion resin.
11. 11 . The method according to claim 9 , wherein the additive comprises one or both of a surface conditioner and a surfactant that decreases a surface energy between the aerogel particles and a solution comprising the water-soluble polymer and the liquid medium.
12. 12 . The method according to claim 9 , wherein the additive comprises a dispersant that attaches to a surface of the aerogel particles and forms an electrostatic repulsive force or a steric barrier repulsive force that prevents the aerogel particles from approaching each other.
13. 13 . The method according to claim 12 , wherein the additive comprises an emulsion resin that is dispersed in the liquid medium by the dispersant and is adsorbed on the surface of the aerogel particles.

Description

CROSS-REFERENCE TO RELATED APPLICATIONS This application is a 35 U.S.C. § 371 national phase application of PCT/JP2021/003314, filed on Jan. 29, 2021, which claims priority to PCT/JP2020/003803, filed on Jan. 31, 2020. TECHNICAL FIELD The present invention relates to a manufacturing method for a thermal insulating material. BACKGROUND ART Aerogel is known as a material excellent in thermal insulating properties. In addition, a method is proposed in which aerogel is processed into the shape of particles to be used as a constitutional material of a thermal insulating material (for example, Patent Literatures 1 and 2). In Patent Literature 1, it is proposed to use particulate aerogel as a filler between resin plates and the like configuring a thermal insulated window. In Patent Literature 2, a method is disclosed in which an intermediate product obtained by preparing a water dispersion containing aerogel particles and organic fibers, and then, by vaporizing water is further press-molded to manufacture a thermal insulating material (molded product). CITATION LIST Patent Literature Patent Literature 1: Japanese Unexamined Patent Publication No. 2012-91943Patent Literature 2: Japanese Unexamined Patent Publication No. 2014-35044 SUMMARY OF INVENTION Technical Problem It is expected that a composite material obtained by dispersing aerogel particles in a resin component has excellent heat resistance. However, when forming such a composite material into a coating liquid, there were problems that the resin component is impregnated into fine pores of the aerogel particles, a fine pore structure is lost, and thermal insulating properties decrease, and the strength of a coated film is not sufficiently obtained and cracks are likely to occur. Therefore, an object of the present invention is to provide a manufacturing method for a thermal insulating material in which the impregnation of a resin component into fine pores of aerogel particles is suppressed, and a thermal insulating material having high thermal insulating properties and high film formability can be obtained. Solution to Problem One aspect of the present invention relates to a manufacturing method for a thermal insulating material, including: an applying step of applying a coating liquid obtained by mixing aerogel particles, a water-soluble polymer having a hydrophobic group, and a liquid medium such that the aerogel particles are aggregated, with a coating means applying a pressure of 1.5 MPa or less to the coating liquid to obtain a coated film; and a removing step of removing at least a part of the liquid medium from the coated film to obtain the thermal insulating material. In the coating liquid of the manufacturing method described above, a contact interface between the aerogel particles and a resin component is reduced by the aggregation of the aerogel particles, and the impregnation of the resin component into fine pores of the aerogel particles is suppressed. In addition, in the coating liquid described above, since the aggregates of the aerogel particles prepared in advance are not compounded, but the aerogel particles are aggregated when mixed with other components, the aerogel particles and the aggregates thereof are evenly dispersed, and the unevenness, the cracks, and the like of the coated film due to uneven distribution of the aerogel particles can be suppressed. Further, in the manufacturing method described above, since the water-soluble polymer having a hydrophobic group is used as the resin component, the dispersibility of the aerogel particles is further improved, and even when increasing a filling rate of the aerogel particles, the aerogel particles and the aggregates thereof are evenly dispersed in the coating liquid. Then, in the manufacturing method described above, by using the coating means applying a pressure of 1.5 MPa or less to the coating liquid, the aggregates are prevented from being crushed by a load during the coating. Therefore, according to the manufacturing method described above, the thermal insulating material having high thermal insulating properties and high film formability is obtained. In one aspect, the coating liquid may contain aggregates of the aerogel particles, and an average diameter of the aggregates may be 2 to 40 times an average diameter of the aerogel particles. According to the coating liquid containing such aggregates, the effects described above are more remarkably exhibited. In one aspect, when observing a diluted solution obtained by diluting the coating liquid with an optical microscope, an area occupied by the aggregates having a diameter of 20 μm or more relative to an area occupied by the aerogel particles and the aggregates of the aerogel particles within an observation visual field may be 50% or more. Accordingly, the effects described above are more remarkably exhibited. In one aspect, a total content of the aerogel particles and the aggregates of the aerogel particles in the coating liquid m