| abstract |
Expanded cellular structures are formed from dense nonporous cellulose paper with an air permeance of less than 30 ml/min which cellular structure is provided with a shape retention of at least 90%. The shape stability is obtained by forming the cellular structure, spraying with an aqueous liquid and heating, the amount of liquid, time and temperature of heating being selected and sufficient to provide the desired shape retention. The minimum amount of water is at least 30 weight % of dry paper more usually at least 75% with minimum heating of 1 minute at 100° C. |