Q.1038: Why not coffee filter paper or tea bag paper disintegrate like other paper when in contact with water for extended period of time?
Ans. Coffee filter paper, tea bag paper and several other papers are called wet strength paper. These are the paper which retain part or most of their strength even when saturated with water. Typically paper will disintegrate when wet, but a class of polymers known as wet strength additives, is added to paper to impart wet strength. This polymer create a protective layer around fibers.
These polymer comes in direct contact with hot beverages, so these are food grade polymers.