US-12627000-B2 - Manufacturing method of porous medium of olefin-based resin, manufacturing method of separator for battery, and manufacturing apparatus

US12627000B2US 12627000 B2US12627000 B2US 12627000B2US-12627000-B2

Abstract

A polymer solution is created by mixing an olefin-based resin and a solvent in a pressure vessel. A high-pressure fluid of carbon dioxide is created. Temperature of the high-pressure fluid is adjusted. A mixed fluid is created by mixing the high-pressure fluid of which the temperature is adjusted and the polymer solution in the pressure vessel. Cooling of the mixed fluid causes phase separation of the mixed fluid to occur. After phase separation, pressure in the pressure vessel is released, and the solvent and the carbon dioxide vaporize. The vaporizing of the solvent and the carbon dioxide creates a porous medium of olefin-based resin.

Inventors

Kohei MATSUNOBU
Kiyoshi Matsuyama

Assignees

TOYOTA JIDOSHA KABUSHIKI KAISHA
FUKUOKA INSTITUTE OF TECHNOLOGY

Dates

Publication Date: 20260512
Application Date: 20221026
Priority Date: 20211203

Claims (11)

1 . A manufacturing method of a porous medium of an olefin-based resin, the manufacturing method comprising steps of: (a) preparing a polymer solution by mixing the olefin-based resin and a solvent in a pressure vessel; (b) creating a high-pressure fluid of carbon dioxide; (c) adjusting a temperature of the high-pressure fluid; (d) preparing a mixed fluid by mixing the high-pressure fluid of which the temperature is adjusted, and the polymer solution, in the pressure vessel; (e) cooling the mixed fluid to cause phase separation of the mixed fluid; and (f) vaporizing the solvent and the carbon dioxide following the phase separation, by releasing pressure in the pressure vessel, wherein the vaporizing of the solvent and the carbon dioxide in the step (f) produces the porous medium of the olefin-based resin.
2 . The manufacturing method according to claim 1 , wherein: the porous medium of the olefin-based resin contains at least one type selected from a group consisting of a first pore structure, a second pore structure, and a third pore structure; the first pore structure is made by particles being linked, the second pore structure is a three-dimensional network, and in the second pore structure, multiple foamy pores communicate with each other, and the third pore structure is a three-dimensional network, and in the third pore structure, the multiple foamy pores are independent from each other.
3 . The manufacturing method according to claim 1 , wherein the step (c) includes adjusting the temperature of the high-pressure fluid such that the phase separation results in spinodal decomposition.
4 . The manufacturing method according to claim 3 , wherein the step (c) includes adjusting the temperature of the high-pressure fluid such that a spinodal region is created in a liquid phase in a phase diagram of the polymer solution and the high-pressure fluid.
5 . The manufacturing method according to claim 4 , wherein in the spinodal region, a mixture ratio of the polymer solution and the high-pressure fluid is adjusted.
6 . The manufacturing method according to claim 1 , wherein the step (c) includes adjusting the temperature of the high-pressure fluid such that a difference between a first solubility parameter of the olefin-based resin and a second solubility parameter of the high-pressure fluid is 5.3 or more.
7 . The manufacturing method according to claim 1 , wherein: the olefin-based resin contains polyethylene; and in the step (c), the temperature of the high-pressure fluid is adjusted to 50° C. to 100° C.
8 . The manufacturing method according to claim 1 , wherein: the olefin-based resin contains polypropylene; and in the step (c), the temperature of the high-pressure fluid is adjusted to 120° C. to 150° C.
9 . The manufacturing method according to claim 1 , wherein the high-pressure fluid is a supercritical fluid.
10 . The manufacturing method according to claim 1 , wherein in the step (f), the pressure vessel is heated to 40° C. to 60° C. before the pressure is released.
11 . A manufacturing method of a separator for a battery, the manufacturing method comprising: (A) manufacturing a porous medium of an olefin-based resin by the manufacturing method according to claim 1 ; and (B) manufacturing a separator for a battery, the separator including the porous medium of the olefin-based resin.

Description

CROSS-REFERENCE TO RELATED APPLICATION This application claims priority to Japanese Patent Application No. 2021-197100 filed on Dec. 3, 2021, incorporated herein by reference in its entirety. BACKGROUND 1. Technical Field The present disclosure relates to a manufacturing method of a porous medium of an olefin-based resin, a manufacturing method of a separator for a battery, and a manufacturing apparatus. 2. Description of Related Art Japanese Unexamined Patent Application Publication No. 2016-176061 (JP 2016-176061 A) discloses a porous sintered compact of polyethylene. SUMMARY Various types of porous media of olefin-based resin (hereinafter, may be abbreviated to “porous media”) are being manufactured. There is demand for controlling pore structures in accordance with the use of the porous medium. The present disclosure discloses a manufacturing method of a porous medium of olefin-based resin, regarding which the pore structure can be controlled. Technical configurations, and functions and effects of the present disclosure will be described below. Note however, that an acting mechanism according to the present specification includes estimation. The acting mechanism does not limit the technical scope of the present disclosure. 1. A manufacturing method of a porous medium of an olefin-based resin includes the following steps of (a) to (f): (a) preparing a polymer solution by mixing the olefin-based resin and a solvent in a pressure vessel; (b) creating a high-pressure fluid of carbon dioxide; (c) adjusting a temperature of the high-pressure fluid; (d) preparing a mixed fluid by mixing the high-pressure fluid of which the temperature is adjusted, and the polymer solution, in the pressure vessel; (e) cooling the mixed fluid to cause phase separation of the mixed fluid; and (f) vaporizing the solvent and the carbon dioxide following the phase separation, by releasing pressure in the pressure vessel. The vaporizing of the solvent and the carbon dioxide in the step (f) produces the porous medium of the olefin-based resin. A polymer solution can be formed by mixing the olefin-based resin and the solvent. A high-pressure fluid of carbon dioxide (CO2) is mixed with the polymer solution. This forms a mixed fluid. CO2 is a poor solvent in the mixed fluid. Cooling of the mixed fluid causes phase separation of the mixed fluid to occur. Vaporization of the CO2 and the solvent following phase separation produces a porous medium. The pore structure can change depending on the mode of phase separation. According to new findings of the present disclosure, the mode of phase separation can be controlled by the temperature of the high-pressure fluid (CO2). This is thought to be due to affinity between the high-pressure fluid (CO2) and the polymer solution changing depending on the temperature of the high-pressure fluid (CO2). 2. The porous medium of the olefin-based resin may contain at least one type selected from a group consisting of a first pore structure, a second pore structure, and a third pore structure. The first pore structure is formed by particles being linked. The second pore structure is a three-dimensional network. In the second pore structure, multiple foamy pores communicate with each other. The third pore structure is a three-dimensional network. In the third pore structure, the multiple foamy pores are independent from each other. In the manufacturing method of “1” above, for example, the first to third pore structures can be separately produced at will. For example, the second pore structure is useful as a separator for a battery. Note that a porous medium having both the first pore structure and the second pore structure, for example, may be formed. Also, a porous medium having both the second pore structure and the third pore structure, for example, may be formed. 3. The above step (c) may include adjusting the temperature of the high-pressure fluid such that the phase separation results in spinodal decomposition. The mode of phase separation can be controlled to spinodal decomposition by the temperature of the high-pressure fluid. The second pore structure is thought to be able to be formed by spinodal decomposition. 4. The above step (c) may include adjusting the temperature of the high-pressure fluid such that a spinodal region is created in a liquid phase in a phase diagram of the polymer solution and the high-pressure fluid. The phase diagram of the polymer solution and the high-pressure fluid can change depending on the temperature of the high-pressure fluid. The affinity between the polymer solution and the high-pressure fluid is thought to change depending on the temperature of the high-pressure fluid. 5. In the spinodal region, a mixture ratio of the polymer solution and the high-pressure fluid may be adjusted. The mode of phase separation can also change depending on the mixture ratio of the polymer solution and the high-pressure fluid. 6. The above step (c) may include adjusting the temperature