Method for producing hydrotalcite-based compound, hydrotalcite-based compound surface-treated with anionic surfactant, infrared absorber, and agricultural film

摘要

An infrared absorber having a high infrared absorptivity is provided which is suitable for use in an agricultural film. The infrared absorber comprises as an active ingredient a hydrotalcite compound represented by the formula: (Mg and/or Zn)aAl2(condensed silicate ion and/or condensed phosphate ion)m-2/m.bH2O wherein a satisfies the relationship 2 /= a /= 8, m is an integer of 1 or greater, b satisfies the relationship b /= 4 and the condensed silicate ion and/or condensed phosphate ion contains at least 2 mol of Si and/or P, said hydrotalcite compound having a crystal surface coated with 0.1 to 10% by weight of an anionic surfactant, and said hydrotalcite compound having intercalated anions composed mainly of condensed silicate ions and/or condensed phosphate ions. Infrared rays whose wavelengths are in the range of 5 to 30 mu m are very effectively absorbed by virtue of the structure having silicate and/or phosphate components intercalated in high proportion.