Fire resistant wooden body and method for producing thereof

A method for sulphation and phosphorylation of a wooden body to impart anti-flame properties to the wooden body comprising the following operations:

• i) providing a wooden body, preferably a dried wooden body;
• ii) preparing a sulphation and phosphorylation solution, preferably under heated conditions, the sulphation and phosphorylation solution comprising water, ammonium sulphamate, urea and at least one compound of the formula (I):
• PO(OH)2—R—PO(OH)2 (I)
• wherein
• R represents a linear or branched, substituted or unsubstituted C1-10, preferably C1-5, alkyl group;
• an N(R1) group;
• a R2N(R3)R4 group;
• R1 represents H, a linear or branched, substituted or unsubstituted C1-5, preferably C1-3, alkyl group;
• R2 and R4 independently represent a linear or branched, substituted or unsubstituted C1-5, preferably C1-3, alkyl group;
• R3 represents a linear or branched, substituted or unsubstituted C1-5, preferably C1-3, alkyl group;
• a R5N(R6)R7 group;
• R5 and R7 independently represent a linear or branched, substituted or unsubstituted C1-5, preferably C1-3, alkyl group;
• R6 represents a linear or branched, substituted or unsubstituted C1-5, preferably C1-3, alkyl group;
• a R8N(R9)R10 group;
• R8, R9 and R10 independently represent a linear or branched, substituted or unsubstituted C1-5, preferably C1-3, alkyl group;
• with the proviso that the number of —PO(OH)2 groups in the general formula (I) is not greater than 5;
• iii) immersing the wooden body into the sulphation and phosphorylation solution, preferably at a pressure higher than atmospheric pressure;
• iv) extracting the wooden body from the sulphation and phosphorylation solution;
• v) maintaining the wooden body at a temperature between 110° and 175° C. for a period of time between 1 minute and 5 hours, obtaining at the end a sulphated and phosphorylated wooden body with anti-flame properties.