Bulk material comprising solid diisocyanates and prepolymers containing urethane groups obtainable therefrom
The present invention relates to a bulk material comprising solid diisocyanate, especially naphthalene 1,5-diisocyanate or p-phenylene diisocyanate, to a process for production thereof, and to a process for preparing isocyanate prepolymers using the bulk material of the invention, to the isocyanate prepolymers themselves and to the use thereof for preparation of polyurethane elastomers, especially cast polyurethane elastomers.
1. A process for producing a bulk material, comprising a crystallization operation (i) and at least one step (ii) comprising classification, agglomeration, or comminution,
wherein the bulk material comprises a solid diisocyanate, wherein the solid diisocyanate is a solid at room temperature (25° C.), wherein the solid diisocyanate has a melting point of ≥80° C., and wherein, in a sieve analysis of the bulk material with a twin-sieve arrangement having mesh sizes 0.1 mm and 4 mm, at least 90% by weight of the bulk material is obtained in a fraction between 0.1 mm and 4 mm.
2. The process according to claim 1 , wherein the crystallization operation (i) comprises crystallizing a melt of the solid diisocyanate on a cold surface and scraping off the solid diisocyanate after solidification.
3. The process according to claim 1 , wherein step (ii) comprises comminution of the solid diisocyanate performed in a comminution apparatus.
4. The process according to claim 1 , wherein oversize bulk material and undersize bulk material are at least partly separated by classification in a step (iii) from the bulk material obtained in step (ii) and wherein a portion of the oversize bulk material and/or a portion of the undersize bulk material is at least partly recycled into the process.