Rigid foam and process for producing the same

摘要

A rigid foam, especially a largely closed-cell polyurethane or polyisocyanurate rigid foam, includes a cell structure being formed by the expansion of rigid foam raw materials with carbon dioxide as an inflating agent. The cell structure is substantially homogeneous and has a cell content of substantially CO2 inflating agent and proportions of a physical inflating agent being at least substantially insoluble in at least one of the rigid foam raw materials. A process for producing a rigid foam having a cell structure formed by the expansion of rigid foam raw materials with carbon dioxide includes forming a fine-celled rigid foam material by preparing an inflating agent being at least substantially insoluble in at least one of the rigid foam raw materials. The inflating agent is homogeneously emulsified in at least one of the rigid foam raw materials prior to the beginning of a chemical reaction, in the form of the disperse phase of an emulsion having a liquid droplet size being at most equal to 10 mu m in diameter and a proportion by weight of less than 3.5% of the rigid foam material. The rigid foam raw materials include components for producing an essential required amount of inflating agent in the form of carbon dioxide. The rigid foam raw materials in particular are polyols and isocyanates. Activators and/or stabilizers are optionally additionally used to form the cell structure. The cell structure preferably has a cell size of less than 100 mu m in diameter.