In today's paper and tissue manufacturing processes, some helpful chemicals such as fillers, sizing additives, defoamers, thickeners, retention aids, and wetor dry strength resins are commonly used. Wet-strength resin chemicals are introduced to the stock for producing paper or tissue.
The wet strength of paper and paperboard is a measure of how well the web of fibers holding the paper together can resist a force of rupture when the paper is wet. Wet strength is routinely expressed as the ratio of wet to dry tensile force at break.
Wet strength chemicals improve the tensile properties of the paper both in wet and dry state by crosslinking the cellulose fibres with covalent bonds that do not break upon wetting.
Different wet strength chemicals are in use, like wet strength resins or neutral sizing agents. Normal wet strength resins are: urea-formaldehyde (UF), melamine-formaldehyde (MF) and polyamide-epichlorohydrin (PAE). Neutral sizing agents are alkylketene dimers (AKD) and alkenylsuccinic anhydride (ASA). In recent years, efforts have been devoted to develop environmentally friendly wet strength resins from renewable resources.
Widely using of wet strength in household tissue paper:
Toilet Tissue paper (yes or no, depend standard from different country)
Facial tissue (yes or no, depend standard from different country)
Kitchen paper (Yes)
Napkin (Yes)
Paper handtowel (Yes)
Environmental considerations:
Recycling of wet strengthened paper requires higher intensity reworking conditions in the re-pulping process to break the fibre web. Some wet strength papers are not considered recyclable.