Flame-retardant timber materials

Flame-retardant timber materials comprising, as flame retardant, at least one tetraalkyl bisphosphate of the formula (I)

• in which
• R1, R2, R3, and R4 are mutually independently a C1-C8-alkyl or C1-C4alkoxyethyl moiety,
• A is a straight-chain, branched and/or cyclic C4-C20-alkylene moiety, a —CH2—CH═CH—CH2— group, a —CH2—C≡C—CH2— group, a —CHR5—CHR6—(O—CHR7—CHR8)a— group, in which a is a number from 1 to 5, a —CHR5—CHR6—S(O)b—CHR7—CHR8— group, in which b is a number from 0 to 2, or a —(CHR5—CHR6)c—O—R9—O—(CHR7—CHR8)d— group, in which c and d are mutually independently numbers from 1 to 5,
• R5, R6, R7, and R8 are mutually independently H or methyl,
• R9 is a —CH2—CH═CH—CH2— group, a —CH2—C≡C-CH2— group, a 1,2-phenylene moiety, a 1,3-phenylene moiety, a 1,4-phenylene moiety, a moiety of the general formula (II),
• a moiety of the general formula (III),
• a moiety of the general formula (IV),
• or a moiety of the formula —C(═O)—R12—C(═O)—,
• R10 and R11 are mutually independently H or C1-C4-alkyl, or R10 and R11 together are an optionally alkyl-substituted ring having from 4 to 8 carbon atoms, and
• R12 is a straight-chain, branched and/or cyclic C2-C8-alkylene moiety, a 1,2-phenylene moiety, a 1,3-phenylene moiety, or a 1,4-phenylene moiety.