TECHNOLOGY FOCUS - POLYMERS - Preferred Process: The biomass-starting material for the preparation of the composition undergoes a reaction, preferably decomposition to obtain aryl composition, where the aryl compound in the composition comprises at least one hydroxy group and/or at least one alkoxy group per molecule and the oxyaryl composition is subjected to amination. The oxyaryl composition comprises at least 75, preferably at least 95 wt.% of mononuclear aryl compounds. The preparation of polyisocyanate comprises either providing the biomass starting material, decomposing the biomass starting material to obtain the aryl composition, aminating the oxyaryl composition, optionally condensing the obtained aminated product with a formaldehyde source and phosgenation of the aminated product or the condensation product; or providing the biomass starting material, decomposing the biomass starting material, optionally separating the disrupted material into at least one fraction (C1) enriched in aryl components and at least one fraction (C2) with no aryl components, optionally feeding the disrupted product or the aryl enriched fraction (C1) into a dealkylation zone, in the presence of hydrogen and/or steam, where the dealkylation zone contains a discharge, where optionally the discharge undergoing separation in the dealkylation zone to obtain at least one stream (D1) enriched with dealkylated oxyaryl components and at least one stream (D2) enriched in light volatile components, amination of the decomposition product, the fraction (C1) or the discharge of the dealkylation zone or the stream (D1) in an amination zone using ammonia, optionally condensing the amination product with a formaldehyde source and phosgenation of the aminated product or the condensation product. The biomass starting material for pulping is subjected to pyrolysis in liquid phase, where the pyrolysis takes place without the addition of hydrogen compounds or with the addition of hydrogen (hydrocracking). For the pyrolysis, the black liquor material is used, which under normal conditions (20 degrees C, 1013 mbar) exhibits a liquid content of at most 70 wt.%, preferably 50 wt.%. The biomass starting material is decomposed in the presence of an aqueous-alkaline, aqueous-acidic or organic medium. The decomposition takes place using at least one cellulose depleted fraction from cellulose process, preferably the black liquor from the kraft-process. The separation of (C1) and (C2) takes place via distillation, extraction, absorption (all preferred) and/or membrane separation. The separation of (C1) and (C2) comprises extraction of the decomposition product to obtain an aryl enriched extract and an aryl depleted residue; optionally separating the extract into a fraction comprising enriched extractant and depleted aryl components and a fraction comprising aryl enriched and extractant depleted components; and feeding the aryl enriched extractants or the aryl enriched fractions. The dealkylation step comprises a hydrodealkylation and/or a vapor dealkylation steps. The temperature and the pressure in the dealkylation zone is 400-900 degrees C, preferably 500-800 degrees C and 1-100, preferably 1-10 bar, respectively. The discharge from the dealkylation zone is separated to obtain (D1a) a stream containing enriched mononuclear, low or non-alkylated oxyaryl components, (D1b) a stream enriched in low or non-dealkylated aryl components and (D1c) a stream enriched in volatile by-products, where (D1c) is lighter than (D1a) and (D1b). The discharge from the amination zone is subjected to separation to obtain at least one stream (E1) enriched in aryl amine and at least one stream (E2) enriched in oxyaryl component, where the separation step comprises distillative separation of the discharge from the amination zone to obtain ammonia-enriched fraction and an ammonia depleted fraction, optionally distillative removal of water from the ammonia depleted fraction and distillative separation of (E1) and (E2). (E1) is at least partially: subjected to condensation with the formaldehyde source; or subjected to phosgenation without condensation with the formaldehyde source. (E1) is subjected to further separation to obtain a stream (E1m) enriched in aryl monoamine and a stream (E1p) enriched in aryl polyamine. (E1m) is condensed with the formaldehyde source, before phosgenation step. (E1p) is condensed with the formaldehyde source before phosgenation or directly subjected to the phosgenation step. (E2) is fed back into the amination zone. In the method, an amine, which is not from the biomass, is added to the aminated product, before the condensation and phosgenation steps. Preferred Components: The biomass starting material is a lignin containing material, preferably lignocellulosic material or its decomposition product. The biomass starting material is a lignin-containing stream from the decomposition of the lignocellulosic material for the manufacture of cellulose (pulp), preferably a black liquor from the kraft pulping (sulfate-decomposition). The polyisocyanate composition exhibits an isocyanate content of at least 30. EXAMPLE - None given.