In the art of tissue making and papermaking, many additives have been proposed for specific purposes, such as increasing wet strength, improving softness, or controlling wetting properties. For instance, in the past, wet strength agents have been added to paper products in order to increase the strength or otherwise control the properties of the product when contacted with water and/or when used in a wet environment. For example, wet strength agents are added to paper towels so that the paper towel can be used to wipe and scrub surfaces after being wetted without the towel disintegrating. Typical wet strength agents are also added to facial tissues to prevent the tissues from tearing when contacting fluids. In some applications, wet strength agents are also added to bath tissues to provide strength to the tissues during use. When added to bath tissues, however, the wet strength agents should not prevent the bath tissue from disintegrating when dropped in a commode and flushed into a sewer line. Typical wet strength agents added to bath tissues are sometimes referred to as temporary wet strength agents since they only maintain wet strength in the tissue for a specific length of time.
Although great advancements have been made in providing wet strength properties to paper products, various needs still exist to increase wet strength properties in certain applications, or to otherwise better control the wet strength properties of paper products.
For instance, a reoccurring need in the production of tissue products is to improve the softness of the product at a given geometric mean tensile strength. In other words, one objective in producing tissue products is to produce a product having high softness and high strength. In the past, softness was increased by adding debonders to the web which reduced hydrogen bonding of the fibers. Strength was then built back into the web by adding various strength agents, such as a polyaminoamide epichlorohydrin. Although epichlorohydrin resins are well suited for this purpose, the resins are generally not biodegradable. As such, there is a need not only to develop strength agents that improve the strength of paper webs without substantially impacting softness, but there is also a need to develop a biodegradable strength agent that can be used as a replacement to traditional epichlorohydrin resins.