Curable Composition Based on Polyurethane-Urea and on Block Copolymers, and Transparent Material Obtained From Said Composition

Method of preparing a curable composition, comprising the following steps:

• 1. the preparation of a first component (A) by blending:
• a prepolymer of the polyurethane type, obtained by the polycondensation:
• of one or more polyisocyanates chosen from xylylene diisocyanate (XDI), meta-tetramethylxylene diisocyanate (TMXDI), cycloaliphatic diisocyanates, the trimer of isophorone diisocyanate, and the trimer of hexamethylene diisocyanate;
• and
• of one or more polyols chosen from the family of polypropoxylated bisphenol A compounds, containing on average 1 to 10 propylene oxide units on each side of the central bisphenol A group, the family of polyethoxylated bisphenol A compounds, containing on average 1 to 15 ethylene oxide units on each side of the central bisphenol group A, and the family of difunctional, trifunctional and tetrafunctional polycaprolactone-alcohols,
• the isocyanate functional groups being present in excess relative to the alcohol functional groups;
• with a polystyrene-block-polybutadiene-block-poly(methyl methacrylate) block copolymer, the weight ratio of the prepolymer to the block copolymer being between 95/5 and 20/80;
• 2. the preparation of a second compound (B) by blending:
• a diamine chosen from diethyltoluene diamine (DETDA) or a diamine of formula (I):
• in which R1 and R3, which are identical or different, each represent, independently of one another, a group chosen from methyl, ethyl, n-propyl and isopropyl and R2 represents a hydrogen atom or a chlorine atom,
• with a polystyrene-block-polybutadiene-block-poly(methyl methacrylate) block copolymer, the weight ratio of the amine to the block copolymer being between 95/5 and 20/80;
• and then
• 3. the blending of the first component (A) with the second component (B) in respective amounts such that the ratio of the number of amine functional groups of the diamine to the number of isocyanate functional groups of the prepolymer is between 0.92 and 0.98.