One pervasive feature of daily life in modern, industrialized societies is the use of disposable products, particularly disposable products made of paper. Paper towels, facial tissues, sanitary tissues, and the like, are in almost constant use. Naturally, the manufacture of items in such great demand has become one of the largest industries in the industrially developed countries. The general demand for disposable paper products has, also naturally, created demand for improved versions of the products and of the methods for their manufacture. Despite great strides in papermaking, research and development efforts continue to be aimed at improving both the products and their processes for manufacture.
Disposable products such as paper towels, facial tissues, sanitary tissues, and the like, are made from one or more webs of tissue paper. If the products are to perform their intended tasks and to find wide acceptance, they, and the tissue paper webs from which they were made, must exhibit certain physical characteristics. Among the more important of these characteristics are strength, softness, and absorbency. Strength is the ability of a paper web to retain its physical integrity during use. Softness is a pleasing tactile sensation the user perceives as the paper is crumpled in their hand and is contacted to various portions of the anatomy. Absorbency is the characteristic of the paper web that facilitates the take up and retention of fluids, particularly water, aqueous solutions, and suspensions. Two important characteristics of a paper web include the absolute quantity of a fluid the given amount of paper will hold, but also the rate at which the paper web will absorb the fluid. When the paper web is formed into a device such as a towel or wipe, the ability of the paper web to cause a fluid to preferentially be taken up into the paper web and thereby leave a wiped surface dry is also important.
Traditionally, tissue products have been made using a wet-pressing process in which a significant amount of water is removed from a wet-laid web by pressing or squeezing water from the web prior to final drying. In particular, while supported by an absorbent papermaking felt, the web is squeezed between the felt and the surface of a rotating heated cylinder (Yankee Dryer) using a pressure roll as the web is transferred to the surface of the Yankee Dryer for final drying. The dried web is thereafter dislodged from the Yankee Dryer with a doctor blade (creping), which serves to partially de-bond the dried web by breaking many of the bonds previously formed during the wet-pressing stages of the process. Creping generally improves the softness of the web.
More recently, through-air drying has become a more prevalent means of drying tissue webs. Through-air drying provides a relatively non-compressive method of removing water from the web by passing hot air through the web until it is dry. More specifically, a wet-laid web is transferred from the forming fabric to a coarse, highly permeable through-air drying fabric and retained on the through-air drying fabric until it is dry. The resulting dry web is softer and bulkier than a wet-pressed un-creped dried sheet because fewer papermaking bonds are formed and because the web is less dense. Squeezing water from the wet web is eliminated, although subsequent transfer of the web to a Yankee Dryer for creping is still used to final dry and/or soften the resulting tissue.
Thus, it would be useful to provide for a tissue having properties particularly suitable for use as a bath tissue. The resulting tissues of the present invention are characterized by a unique combination of bulk and caliper stability as compared to currently available creped and uncreped paper towel and bath tissue products. Such attributes are needed to manufacture paper products that provide superior thickness and absorbency characteristics while maintaining low basis weight and yet still provide for the softness required such as for bath tissue, premium household towels, and facial tissue in the consumer market.