Impingement air dry process for making absorbent sheet

Abstract

A process for making absorbent sheet includes: (a) depositing an aqueous furnish of cellulosic fiber on a forming fabric; (b) dewatering the wet web to a consistency of from about 15 to about 40 percent; (c) transferring the dewatered web from the forming fabric to another fabric traveling at a speed of from about 10 to about 80 percent slower than the forming fabric; (d) wet-shaping the web on an impression fabric whereby the web is macroscopically rearranged to conform to the surface of the impression fabric; and (e) impingement air drying the web. The process is particularly suitable for making high bulk products form difficult to process furnishes such as recycle furnishes and for making high basis weight products without compressive dewatering with a papermaking felt.

Description

CLAIM FOR PRIORITY[0001] This non-provisional application claims the benefit of the filing date of U.S. Provisional Patent Application Ser. No. 60 / 199,301, of the same title, filed Apr. 24, 2000.TECHNICAL FIELD[0002] The present invention relates to methods of making absorbent cellulosic sheet in general, and more specifically to a process for making a non-compressively dewatered, impingement air dried absorbent sheet.BACKGROUND[0003] Methods of making paper tissue, towel, and the like are well known. Typically, such processes include conventional wet pressing and throughdry processes. Conventional wet pressing processes have certain advantages over conventional through air drying processes including: (1) lower energy costs associated with the mechanical removal of water rather than transpiration drying with hot air; (2) higher production speeds are more readily achieved with processes which utilize wet pressing to form a web; and (3) the process is relatively robust in that it does...

AI Technical Summary

Benefits of technology

0014] Most typically, the step of impingement air drying is carried out over a plurality of impingement air dryers including rotating cylinders and drying hoods sequentially arranged in a row opposing a row of reversing vacuum cylinders over which the web travels. In this arrangement, impingement exhaust air from a downline dryer can be cascaded backward to an upline dryer operating at higher humidity.

0015] A product of any typical basis weight may be made by way of the present invention, suitably having a weight of at least 10 lbs / 3000 ft.sup.2. Higher basis weight products, having basis weights of at least 15 lbs / 3000 ft.sup.2 or at least 20 lbs / 3000 ft.sup.2 may also be produced as will readily be appreciated from the discussion which follows.

Problems solved by technology

As noted in the above, throughdried products tend to exhibit enhanced bulk and superior tactile properties; however, conventional thermal dewatering with hot air tends to be energy intensive and requires a relatively permeable substrate.

However, wet press operations tend to utilize more fiber and thus are more costly on a square foot basis.

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