MXPA01005737A - Method and apparatus for making a throughdried tissue product without a throughdrying fabric - Google Patents

Abstract

A method for making throughdried tissue products includes a throughdryer which functions without a throughdrying fabric. The tissue web is formed in a conventional manner and dewatered to a high consistency prior to being transferred to the surface of the throughdryer. The inside of the throughdryer is operated with a vacuum while a hot air hood serves to blow hot air through the web into the dryer. In one embodiment, the surface of the throughdrying drum is provided with circumferential ridges to impart bulk and cross-machine directional stretch to the resulting tissue. A doctor blade having ridges which intermesh with the circumferential ridges on the throughdryer surface can be used to skim the dried sheet from the dryer surface.

Description

METHOD AND APPARATUS FOR MANUFACTURING A DRY TISSUE PRODUCT CONTINUOUSLY WITHOUT A CONTINUOUS DRYING FABRIC Background of the Invention In the manufacture of tissue products, such as facial tissue, tissue for bathroom, similar paper towels, the use of a continuous drying process is well known. In general, the continuous drying process involves passing the hot air through a tissue of drained tissue while the fabric is supported by a continuous drying cloth. More specifically, the fabric supported by the tel is dried while it is kept in contact with a rotating continuous drying drum, which supplies the hot parched air. Depending on the particular process, the dried fabric may be subsequently creped or left uncovered However, current continuous drying methods depend on the continuous drying fabrics to provide the desired structure and texture to the resulting tis product. The designs of such fabrics are limited by the inherent nature of the weaving process and the properties of the filaments used to weave the fabrics. A particular problem associated with many filament materials is lack of ability to withstand high temperatures. Afterwards, as efforts continue to increase the productivity of the machines that make the tissue continuously dried, there is an incentive in the ability to increase the dryer temperatures and the efficiency of the drying energy and shorten the drying times. However, the continuous drying fabric is a limiting factor due to several reasons such as temperature degradation, loss of latent heat in each revolution of the dryer, etc.

Therefore, there is a need for a method to improve the drying efficiency of continuous drying tissue machines.

Synthesis of the Invention It has now been discovered that the continuous drying fabric can be removed from the tissue machine by properly designing the continuous dryer. This not only eliminates the costs of comparing continuous drying fabrics and the non-working time costs associated with fabric changes, but also the thermal efficiency of the drying process can be improved.

Therefore, in one aspect the invention resides in a method for making a continuous drying tissue sheet comprising: (a) forming a tissue of tissue; (b) draining tissue tissue; (c) transferring the dewatered fabric from a support fabric to the surface of a continuous drying drum having a plurality of holes through which the hot air passes to dry the fabric; (d) drying the fabric while on the surface of the continuous drying drum; and (e) removing the dried fabric from the surface of the continuous drying drum. The transfer of the fabric onto the continuous drying drum surface can be aided by a blow box which blows compressed air through the supporting fabric towards the surface of the continuous drying drum. Furthermore, the transfer can be further assisted by the presence of a vacuum box inside the continuous drying drum at the transfer point. The removal of the dried fabric from the surface of the continuous drying drum can be aided by the presence of a blow box inside a continuous drying drum which blows air out to the dried fabric at the point of removal. Alternatively or addition, a doctor's blade can be used to remove the dried tissue from the surface of the continuous drying drum. In some cases, if the fabric strength is adequate, dried fabric can simply be peeled.

In another aspect of the invention, this resides in a method for making a continuous drying tissue sheet comprising: (a) forming a tissue of tissue; (b) draining tissue tissue; (c) transferring the dewatered fabric to the surface of a continuous drying drum without being supported by a continuous drying fabric, said surface of the continuous drying drum having a plurality of circumferential ridges; (d) drying and weaving while on the surface of the continuous drying drum; and (e) removing the dried fabric from the continuous drying drum surface. In this embodiment, the presence of the circumferential ribs imparts a significant volume, a stretch in the transverse direction to the machine and a flexibility to the resulting dried fabric.

In another aspect, the invention resides in a continuous drying apparatus for drying a fabric, said apparatus comprising a perforated continuous drying drum having a plurality of circumferential ridges, a cover for hot air for supplying hot air to the drum surface. continuous drying, a vacuum zone within the continuous drying drum to pull the hot air from the hot air cover inwardly through the surface of the continuous drying drum to dry the fabric, and means for removing the dried fabric from the surface of the continuous drying drum. Means for removing the dried fabric from the surface of the continuous drying drum may include a doctor blade with ridges which is placed against the continuous drying drum surface which removes the tissue from the surface and / or a box of liquid. blown into the continuous drying drum which one uses the pressurized air to blow the fabric out of the surface of the continuous drying drum.

As used herein, a "tissue" fabric dried in a low density fiber sheet to make paper suitable for use as a facial tissue, a tissue for bathroom paper towels, as distinguished from other denser kinds of paper. paper such as writing papers.

Description of the Drawings Figure 1 is a schematic view of a method of this invention illustrating the operation of a continuous drying drum without fabric.

Figure 2 is a perspective view of a representative part of the surface of a continuous drying drum according to the invention, the circumferential rims on the surface of the continuous dryer illustrating a doctor blade with interengaged flanges.

Figure 3 is a plan view of a representative part of the surface of the continuous dryer illustrating the arrangement of vacuum holes and circumferential flanges.

Figure 4 is a cross-sectional view of the drum surface of the continuous dryer, further illustrating the spatial relationship of the circumferential ridges of the holes.

Detailed Description of the Drawings Referring to Figure 1, the invention will be described in more detail. A paper head box 10 is shown which deposits an aqueous fibr suspension to make paper between an internal forming fabric 11 and an external forming fabric 12 as the fabrics traverse an arcuate trajectory defined by the surface of the forming roller 13. E Recently formed fabric 14 is retained by the interior forming fabric and passes over an optional capillary drain roll for the purpose of non-compressively removing the free water from the fabric. A suitable capillary drain roll is described in U.S. Patent No. 5,701.68 entitled "Method and Capillary Drainage Apparatus" issued December 3, 197 to Chuang et al. Which is incorporated herein by reference. The fabric is then transferred to the surface of the continuous drying drum 15 with the aid of an optional blow box 16 in combination with an internal vacuum box 17. Optional press rolls 18 and 19 selectively densify and reinforce parts of the fabric to In order to decouple the tissue resistance resulting from the overall high volume and the low density. The interior of the continuous drying drum contains a vacuum zone 20 in order to pull the hot air d the hot air cover 21 through the fabric and into the interior of the continuous drying drum. When the dried fabric reaches the end of its arc, the fabric is removed from the surface of the drying drum, preferably either by skimming the fabric off the surface using a doctor blade with ridges 22 and / or by blowing it out. of the surface using an optional blow box 23 and then wrapping it in a parent roll 25 for further processing (turning it into facial tissue, bathroom tissue, paper towel, etc.) in a normal manner. To the extent that there are any residual fibers remaining on the surface of the continuous drying drum after the continuous drying drum rotates beyond the doctor's blade, those fibers may be burned off the surface of the continuous drying drum. using a suitable burner in which the flame is directed to the surface. If a burner is used, the continuous dryer drum requires making a metal that can withstand the high temperatures resulting from direct fire. Those skilled in the art of continuous dryers will be able to select the appropriate metal compositions for such service. Advantageously, the residual heat on the surface of the continuous drying drum resulting from the burning is not wasted and can be used for the subsequent conductive drying of the wet paper.

Those skilled in the art will appreciate what many variations to this process can be made without departing from the scope of the invention. For exampleOther forming configurations can be substituted for the illustrated twin wire former, including the formers of a recent one, the Fourdrinier formers, the suction chest roll formers, etc. Also, the newly formed fabric can be transferred to an intermediate transfer fabric, with or without a rapid transfer, before being transferred to the continuous dryer. However, it can be particularly advantageous to expedite the transfer of the fabric from the forming fabric to the transfer fabric, where the transfer fabric is moving at a speed of from about 5 to about 75 percent slower than the forming fabric. . An example of such a rapid transfer step is described in U.S. Patent No. 5,667,636 issued September 16, 1997 to Engel et al., Entitled "Method for Making Smooth, Non-creped Continuous Drying Sheets", which it was incorporated here by reference.

Fig. 2 is a perspective view of a representative part of the surface of the continuous drying drum, shown interacting with a matching doctor edge trimmings and optionally designed to skim and continuously dry fabric from the surface of the dryer keep going. More particularly, the surface of the continuous drying drum 15 is provided with a series of circumferential flanges 31 which provide a three dimensional contour and a high volume to the dried fabric. The flanges can be continuous or discontinuous in the circumferential direction (machine direction). Between the circumferential flanges is a plurality of holes 32 through which the drier and hot air flows to dry and tissue. The doctor blade with ridges 22 also has its own series of ridges 33 which mesh with the ridges of the surface of the continuous dryer to allow the doctor blade with ridges to scrape or skim the fabric off the surface of the continuous dryer. . The front edge of the doctor's blade is tapered enough to minimize any "creping" action in which the tissue would be curled and the interfiber bond will be substantially reduced.

Figure 3 is a plan view of a representative part of the surface surface of the continuous dryer, more clearly illustrating the plurality of holes 3 between the flanges 31. The open area of the holes may vary depending on the process conditions specific, but in general it can be from about 15 to about 40 percent, more specifically from about 20 about 35 percent.

Figure 4 is a cross-sectional view of the drum surface of the continuous dryer taken along line 4-4 of Figure 3, more specifically showing the relative sizes of the holes-and the circumferential ridges. The height of the circumferential flanges is designated as "h", which may be from about 0.7 to about 2 millimeters. The thickness width of the circumferential flanges is designated "t" which can be from about 0.7 to about 1. millimeters. The spacing between the circumferential flange bases is designated as "d" which can be from about 1.5 to about 3 millimeters. The depth of the holes through the surface wall of the continuous dryer is designated "b", which can be from about 2 to about 1 millimeter.

It will be appreciated that the foregoing description of the drawings, given for purposes of illustration, should not be construed as limiting the scope of the invention as defined by the following claims and all equivalents thereof.

Claims (9)

E I V I N D I C A C I O N E S

1. A method for making a tissue sheet comprising: (a) forming a tissue of tissue; (b) draining the tissue tissue; (c) transferring the dewatered fabric to the surface of a continuous dryer drum without being supported by a continuous drying fabric, said continuous drying drum surface having a plurality of circumferential beads; (d) drying the fabric while it is on the surface of the continuous drying drum; Y (e) removing the dried fabric from the continuous drying drum surface.

2. The method as claimed in clause 1, characterized in that the dewatered fabric of step (b) is supported by a first fabric and transferred in rapid form to a second fabric moving at a speed d from about 5 to about 75 percent slower than the first fabric.

3. The method as claimed in clause 1, characterized in that the dried fabric is removed from the surface of the continuous drying drum with a doctor blade having a plurality of ridges which mesh with the circumferential ridges on the surface of the Continuous dryer surface.

4. The method as claimed in clause 1, characterized in that the dewatered fabric is transferred to the surface of the continuous drying drum with the aid of a blow box which pushes the fabric against the surface of the continuous drying drum .

5. The method as claimed in clause 1, characterized in that the dried fabric is removed from the surface of the continuous drying drum with the help of a blow box inside the continuous dryer which blows air out through the dryer. the holes in the surface of the continuous drying drum.

6. The method as claimed in clause 1, characterized in that the dewatered fabric is transferred to the surface of the continuous drying drum, and fabric is pressed between the surface of the continuous drying drum and one or more pressure rollers.

7. The method as claimed in clause 1, characterized in that any fibers that adhere to the surface of the continuous drying drum after the fabric is removed are burned by direct fuero.

8. The method for making a continuous drying sheet of tissue comprising: (a) forming a tissue of tissue; (b) dewatering the tissue tissue; (c) transferring the dewatered tissue of a support fabric to the surface of a continuous drying drum having a plurality of holes through which hot air passes to dry the fabric; d) drying the fabric on the surface of the continuous drying drum, and (e) removing the dried fabric from the surface of the continuous drying drum.

9. A continuous drying apparatus for drying or weaving, said apparatus comprising a perforated continuous drying drum having a plurality of circumferential ridges a hot air knife for supplying hot air to the surface of the continuous drying drum, a vacuum zone inside the drum Continuous drying to pull the heated air from the hot air cover inward through the surface of the continuous drying drum to dry the fabric, means to remove the dried fabric from the surface of the continuous drying drum. R E S U E N A method for making continuous drying tissue products includes a continuous dryer which operates without a continuous drying fabric. The tissue of tissue is formed in a conventional manner and is drained to a high consistency before being transferred to the surface of the continuous dryer. And the interior of the continuous dryer is operated with a vacuum while the hot air cover serves to blow the hot air through the fabric to the dryer. In one embodiment, the surface of the continuous drying drum is provided with the circumferential ridges for imparting volume and stretching in the transverse direction to the machine to the resulting fabric. A doctor blade that has ridges that mesh with the circumferential flanges of the surface of the continuous dryer can be used to remove the dried sheet from the surface of the dryer.