Patent ID: 8337601

Claim:
An air filter sheet comprising: one or more particles of at least one functional agent selected from the group consisting of an ion-exchange resin, an activated carbon, a zeolite, and a silica gel, wherein the functional agent has an average particle diameter of from 0.1 μm to 30 μm; and one or more fibrils of a fibrillated polytetrafluoroethylene resin having a number average molecular weight of from 3,000,000 to 50,000,000, wherein a weight ratio of the functional agent to the fibrillated polytetrafluoroethylene resin is from 1 to 99, and wherein the air filter sheet does not comprise a lubricant, wherein the air filter sheet is produced by a process comprising: performing fibrillation in a dry state in the absence of a lubricant by applying a shearing stress to a mixture (A) to obtain a mixture (B), wherein the mixture (A) comprises the functional agent and a particulate polytetrafluoroethylene resin having a number average molecular weight of from 3,000,000 to 50,000,000, wherein the weight ratio of the functional agent to the particulate polytetrafluoroethylene resin is from 1 to 99, and wherein the mixture (B) comprises the functional agent and the fibrillated polytetrafluoroethylene resin; and rolling the mixture (B) while applying a shearing stress to obtain the air filter sheet.