Thermal insulation material and method for producing thermal insulation material

A thermal insulation material, comprising:

• a thermal insulation layer containing silicon dioxide particles and inorganic fibers,
• wherein a density ρ [g/cm3] of the thermal insulation layer, and a cumulative proportion R1 for a fiber length of longer than 0 mm and shorter than 4 mm regarding the inorganic fibers contained in the thermal insulation layer and a cumulative proportion R2 for a fiber length of 3 mm or longer and shorter than 30 mm regarding the inorganic fibers contained in the thermal insulation layer satisfy a relational expression (I) below, where the cumulative proportion R1 and the cumulative proportion R2 are calculated according to (d) Cumulative proportion calculation formulae below when the inorganic fibers contained in the thermal insulation layer are summed up based on (a) Class divisions defined below, (b) Class value condition defined below, and (c) Frequency condition defined below,
• Relational Expression (I):
• 0.23
• R
• 1
• +
• 0.24
• <
• ρ
• ≤
• -
• 0.11
• ⁢
• R
• 2
• +
• 0.53
• (a) Class divisions:
• Fiber length of longer than 0 mm and shorter than 1 mm, fiber length of 1 mm or longer and shorter than 2 mm, fiber length of 2 mm or longer and shorter than 3 mm, . . . , and fiber length of 29 mm or longer and shorter than 30 mm
• (b) Class value condition:
• Median of each class (fiber length of 0.5 mm, fiber length of 1.5 mm, fiber length of 2.5 mm, . . . , and fiber length of 29.5 mm)
• (c) Frequency condition:
• Number of inorganic fibers belonging to each class
• (d) Cumulative proportion calculation formulae:
• R1={(Product of class value and frequency of a fiber length class of longer than 0 mm and shorter than 1 mm)+(Product of class value and frequency of a fiber length class of 1 mm or longer and shorter than 2 mm)+(Product of class value and frequency of a fiber length class of 2 mm or longer and shorter than 3 mm)+(Product of class value and frequency of a fiber length class of 3 mm or longer and shorter than 4 mm)}/(Sum total of products of class value and frequency of all classes)
• R2={(Product of class value and frequency of a fiber length class of 3 mm or longer and shorter than 4 mm)+(Product of class value and frequency of a fiber length class of 4 mm or longer and shorter than 5 mm)+ . . . +(Product of class value and frequency of a fiber length class of 29 mm or longer and shorter than 30 mm)}/(Sum total of products of class value and frequency of all classes).