Flame retardant foam and manufacturing method of flame retardant foam

A flame retardant foam which is a molded form of a mixture containing at least a cellulose containing powder, a hydrophilic polymer, a foamable thermoplastic resin, a flame retardant, and water,

• the cellulose containing powder being one of:
• wood powder which contains cellulose and is obtained by pulverizing hardwoods and conifers;
• paper powder which is obtained by pulverizing used paper, or
• a combination of the wood powder and the paper powder,
• the mixture containing at least one of tricalcium phosphate or silica as a dispersant,
• an average particle size of the dispersant being within a range of 4 μm or more and 7 μm or less,
• a bulk density of the dispersant in terms of a loose bulk density being 0.6 g/cm3 or lower when measured using a powder characteristics tester, and
• a bulk density of the dispersant in terms of a packed bulk density being 1.0 g/cm3 or lower when measured using the powder characteristics tester mentioned above.