GB2074624A

GB2074624A - Making creped paper

Info

Publication number: GB2074624A
Application number: GB8113031A
Authority: GB
Original assignee: Kimberly Clark Corp
Current assignee: Kimberly Clark Corp
Priority date: 1980-04-28
Filing date: 1981-04-28
Publication date: 1981-11-04
Also published as: BR8102534A; FR2481328A1; AU6991681A; DE3116602A1; JPS5735099A; ZA812809B

Abstract

A web (46) comprised primarily of cellulose fibers is formed in a forming zone on a dewatering/transfer fabric (42) and is carried to a first drying means (64) thereon, whereupon the web is sandwiched between the dewatering/transfer fabric (42) and a carrier fabric (60). The web is carried around the first drying means between the dewatering/transfer fabric (42) and the carrier fabric (60), with air passing therethrough in order to partially predry the paper web. The web is then carried to a Yankee dryer (72) where it is dried and creped (86). The dewatering/transfer fabric is returned to the forming zone. <IMAGE>

Description

SPECIFICATION Improvements in and relating to papermaking machines This invention relates to papermaking machines.

One of the more significant commercial developments in the manufacture of tissue products in the past few years has been the development of throughdrying technology which permits the production of bulkier and softer tissue webs. Throughdried webs are not pressed between press rolls in order to remove water therefrom, but are rather exposed to a flow of heated air which dries the web by transpiration rather than pressure. Additionally, the webs usually are not calendered, resulting in a softer and bulkier product. Tissue webs of this sort are usually creped in order to add additional softness and reduce some of the papermaking bonds between cellulose fibers in order to further increase bulk and softness, however, it has been found necessary to adhere the predried tissue web to the Yankee drying cylinder with adhesives in order to properly crepe the tissue web.

In spraying adhesives onto the Yankee dryer, the transfer fabric invariably picks up a small amount of adhesive, either through direct contact with the Yankee dryer or from airborne adhesive contaminants. Over a period of hours or days, with the transfer fabric running at a speed up to five thousand feet per minute, an appreciable quantity of adhesives and other contaminants are absorbed by the transfer fabric. It has heretofore been difficult to clean the transfer fabric with traditional steam or water jets because the transfer fabric would be soon thereafter transporting the partially predried tissue web from the throughdrying cylinder, and a dirty transfer fabric would inhibit transfer of the tissue web from the transfer fabric to the Yankee dryer. A dirty transfer fabric also inhibits the attainment of the improved softness and bulk of a thrnughdried web.

It has been common industry practice to form a tissue web on a forming fabric, thereafter transferring it to a carrier fabric in order to carry the web around the throughdrying cylinder.

Transfer between the forming fabric and the carrier fabric is usually accomplished by either a throughdrying cylinder equipped with vacuum means or an air knife, both of which produce a considerable amount of noise and consume appreciable energy. The dried web is traditionally carried between the carrier fabric and a transfer fabric to the Yankee dryer, whereupon a vacuum roll assists transfer from between the fabrics to the transfer fabric, and the web is thereafter adhered to the Yankee. The web must be adhered to the Yankee with adhesives, which are applied in close proximity to the transfer fabric.

One type of prior art throughdrying apparatus, as seen in U.S. Patent No. 3,812,000 Salvucci, Jr., et al., carries the paper web around the throughdrying cylinder on a dryer fabric. The web is removed from a forming fabric by a vacuumassisted pickup roll or an air knife. The web is sandwiched between the drying fabric and a turning roll after leaving the throughdrying cylinder. U.S. Patent No. 4,102,737, Morton, shows a papermaking machine wherein the paper web is pressed between a Fourdrinier fabric and a drying fabric in a first drying area, whereupon the web is transferred to the drying fabric with an air knife assist to be transported through the throughdrying means. U.S. Patent No. 3,303,576, Sisson, shows a throughdrying means wherein the moist paper web is transported around a throughdrying cylinder between the cylinder surface and a dryer fabric.Air movement is from within the throughdrying cylinder outwardly to an enclosing hood, as opposed to the converse relationship in the above noted patents.

A method in accordance with the invention for making a creped tissue product comprises forming a tissue web by deposition of primarily cellulose fiber furnish upon either a Fourdrinier-type forming wire or in a twin wire apparatus, the web thus formed being transported upon a dewatering/transfer fabric to the location of a first cylindrical drying means, whereupon it is sandwiched between the dewatering transfer fabric and a carrier fabric. The tissue web is carried around the first drying means between the fabrics, with hot air movement being directed through the fabrics and the tissue web from a hood partially enclosing the first drying means. The partially predried tissue web is transferred from the dewatering/transfer fabric to a second drying means, in the form of a Yankee dryer, and is thereafter creped from the Yankee dryer with a creping blade.Adhesives may be utilized to insure adhesion of the tissue web to the Yankee dryer.

The web may be carried from the forming zone to the first drying means on the dewatering/transfer fabric so that no transfer of the web from one fabric to another is necessary.

The web may be carried around the first drying means with either of the dewatering transfer fabric or the carrier fabric being adjacent the first cirying means.

The dewatering/transfer fabric may be continuously cleaned by any convenient method between the second drying means and the forming zone.

The invention will now be described by way of example with reference to the accompanying drawings in which: Figure 1 is a simplified diagrammatic illustration of a Prior Art style twin wire forming throughdrying machine; Figure 2 is a simplified diagrammatic illustration of an embodiment of a twin wire forming throughdrying machine in accordance with the invention; and Figure 3 is a partial simplified diagrammatic illustration of a Fourdrinier type papermaking machine employed with the present invention.

It is believed that the invention may best be appreciated by first discussing a typical apparatus found in the Prior Art. Referring to Figure 1 (labelled "Prior Art"), a papermaking machine of the throughdrying type is illustrated. Paper furnish is supplied from headbox 10 to a twin wire former comprising a forming wire or fabric 12, a dewatering fabric 14 and a forming roll 16. The furnish applied from headbox 10 is pressed between the fabrics 12 and 14 around roll 16 so that a substantial portion of the water in the fiber furnish is removed in this initial step.

Alternatively, the furnish may be laid upon the Fourdrinier wire and the water removed by vacuum boxes or table rolls.

The web 1 8 thus formed is carried on the fabric 14 to carrier fabric 20, which carries the web around a vacuum assisted throughdrying cylinder 22 to transfer fabric 23, whereupon the web is sandwiched between transfer fabric 23 and carrier fabric 20. Vacuum roll 25 assists transfer to transfer fabric 23. Because the web has been substantially predried before reaching the Yankee cylinder, creping adhesives supplied from spray means 28 may be necessary in order to adhere the web 18 to the Yankee dryer 24.

The arrangement shown suffers from a number of inherent problems, the most pressing being cleaning of the transfer fabric 23. Because the transfer fabric 23 picks up a small amount of adhesive from the Yankee or from airborne adhesive particles, and thereafter picks up airborne contaminants and fiber particles from web 18, it would be desirable to clean the fabric in order to remove the adhesive and any other contaminants as soon after the web is removed from fabric 23 as possible, the preferred method being with high pressure water or steam. However, since the fabric 23 will be picking up a relatively dry web from the carrier fabric 20, it should be kept as dry as possible, which has traditionally prevented the continuous cleaning of the fabric with water.

Additionally, the vacuum assisted throughdryer 22, which is necessary to insure effective transfer of the web from the dewatering fabric 14 to the carrier fabric 20, generates a significant amount of noise which is at the least, unpleasant, and potentially dangerous.

Figure 2 depicts the apparatus utilized in the method of the present invention. A papermaking furnish is deiivered from a headbox 40 positioned between a dewatering/transfer fabric 42 and a forming fabric 44. The forming fabric may be any of a number of Fourdrinier type wires or fabric common to the papermaking industry. A moist paper web is formed between the fabrics 42 and 44 and issues from the forming zone between fabrics 42 and 44 as web 46 adhered to fabric 42.

Dewatering/transfer fabric 42 and forming fabric 44 are directed about forming roll 48 in compressing relationship, so that a significant portion of the water contained in the furnish supplied from headbox 40 is removed. The fabric 44 is returned to the forming roll on return rolls 52, 54, 56, and 50. The fabric 44 may be cleaned by means well known in the art (not shown herein) prior to engaging the forming roll 48.

The moist web 46 is carried by the dewatering/transfer fabric 42 from the forming zone to a turning roll 58, the fabric 42 being positioned between the web 46 and the roll 58.

The web 46 is carried around the open celled throughdrying cylinder 64 beneath air supply hood 66 with carrier fabric 60 being adjacent the throughdrying cylinder 64 as shown in Fig. 2. Web 46 is dried by the passage of high velocity heated air 67 from head 66 through the web and into cylinder 64. It is within the scope of the present invention, although not shown herein, that the dewatering/transfer fabric 42, rather than the carrier fabric 60, may be placed adjacent the throughdrying cylinder 64. The web 46 is sandwiched between the dewatering/transfer fabric 42 and the carrier fabric 60 from turning roll 58, at 62, around the periphery of the throughdrying cylinder 64 untii the fabrics separate as at 68. The dewatering/transferfabric 42 may be smoother than carrier fabric 60 so that the web 46 adheres to fabric 42 and is directed around guide roll 74 on fabric 42.Alternatively, roll 74 may be provided with a vacuum to assist transfer.

Because the web 46 is carried from the forming zone and around the throughdrying cylinder 64 on the dewatering/transfer fabric 42, there is no web transfer between fabrics, and therefore no need for assistance from either vacuum or air knife mechanisms. The web 46 is transported between fabric 42 and 60 to a position just prior to the Yankee dryer 72 wherein the web adheres to the dewatering/transfer fabric and is directed about guide roll 74 to the Yankee cylinder 72. The carrier fabric 60 returns about rolls 76, 78, 80 and 82 to the throughdrying cylinder 64, and may be cleaned by any well-known method, such as high pressure water or steam. The web 46 is brought into contact with the Yankee dryer 72 by pressure roll 84, whereafter the web 46 passes about the circumference of the Yankee dryer 72, to be creped off the Yankee dryer by doctor blade 86.

The creped web 88 is thereafter directed into roll 90 by drive roll 91 for storage or conversion. If necessary, the surface of the Yankee dryer 72 may be sprayed with a small amount of adhesive, as at 92 to aid in adhering the web 46 to the Yankee 72. The dewatering/transfer fabric is returned to the forming zone by return rolls 94, 96, 98 and 100.

Because the dewatering/transfer fabric 42 will be returning to a wet forming zone, cleaning the fabric with a water or steam spray will not adversely affect the fabric's ability to pick up and transport a partially dried web, as in the Prior Art.

Therefore, a water or steam jet 102 may be positioned at any convenient point between the Yankee dryer 72 and roll 100, preferably as close as possible to the Yankee, at a point before the adhesives which may be picked up by the fabric 42 have had a chance to cure.

An alternative embodiment of the present invention would be utilized in a forming arrangement as shown in Fig. 3. In this embodiment, furnish is supplied from a headbox 104 onto a Fourdrinier wire 106 and is dewatered by means such as suction from vacuum means 109 in the forming roll 108 and turning roll 112, vacuum boxes 110, or table rolls 113. The web 1 14 is removed from the wire 106 at the nip between wire 106 and dewatering/transfer fabric 1 16 as the fabric 11 6 passes around pickup roll 118. Thereafter, the web is sandwiched between the dewatering/transfer fabric and a carrier fabric as in Figure 2. The forming fabric 106 returns to the forming roll 108 around return rolls 120 and 122 and may be cleaned by any conventional method after the web 114 is removed.

Claims

1. A method of making a creped tissue product comprising the steps of: a) forming a tissue web by deposition of cellulose fiber furnish between a forming fabric and a dewatering/transfer fabric, said fabrics travelling around a forming roll and creating a forming zone therebetween, b) removing water from said fiber furnish by compression of said furnish between said forming fabric and said dewatering/transferfabric, c) carrying said tissue web on said dewatering/transfer fabric to a first cylindrical drying means, d) sandwiching said tissue web between said dewatering/transfer fabric and a carrier fabric, and carrying said tissue web around said first cylindrical drying means between said fabrics, and e) transferring said tissue web from said dewatering/transfer fabric to a second cylindrical drying means, and creping said tissue web from said second drying means with a creping blade.

2. A method as claimed in Claim 1, wherein the tissue web is carried around the first drying means with the carrier fabric positioned between the tissue web and the drying means, and the dewatering/transfer fabric overlies the tissue web on an opposite side of the web from the carrier fabric.

3. A method as claimed in Claim 1, wherein the tissue web is carried around the first drying means with the dewatering/transfer fabric positioned between the tissue web and the first drying means, the carrier fabric overlying the tissue web on a surface of said web opposite the carrier fabric.

4. A method as claimed in any of the preceding claims wherein the tissue web is carried from the forming zone and around the first drying means on the dewatering/transfer fabric, such that said first drying means is not provided with vacuum inducing means.

5. A method as claimed in any of the preceding claims further comprising adhering the tissue web to the second drying means with adhesives, the adhesives being applied either to the second drying means or the tissue web.

6. A method as claimed in Claim 5, further comprising continuously cleaning the dewatering/transfer fabric with water or steam jets positioned between the second drying means and the forming roll.

7. A method as claimed in Claim 5, further comprising continuously cleaning the dewatering/transfer fabric with air jets positioned between the second drying means and said forming roll.

8. A method as claimed in any of the preceding claims wherein said tissue web has a dry basis weight of from about 6 to about 30 pounds/2880 feet2.

9. A method of making a creped tissue product comprising the steps of: a) forming a web of principally cellulose fibers by deposition of a fiber furnish onto a forming fabric, b) removing water from said web in a forming zone comprised of said forming fabric and a dewatering/transfer fabric, said web being dewatered by the application of a vacuum thereto or by compression thereof, c) sandwiching said partially dewatered web between said dewatering/transfer fabric and a carrier fabric and transporting said web between said fabrics through a first drying zone, d) drying said web in said first drying zone by forcing heated air through said dewatering/transfer fabric, said web, and said carrier fabric, and e) transferring said web from said dewatering/transfer fabric to a second drying zone in the form of a drying cylinder, and creping said web from said drying cylinder with a creping blade.

10. A method as claimed in Claim 9, further comprising forming said web between said dewatering/transfer fabric and a forming fabric as said fabrics are carried around a forming roll such that water is removed from said web by compression of said fabrics against said forming roll.

1 A method as claimed in any of the preceding claims further comprising transporting the web through the first drying zone between said fabrics without removing the web from said dewatering/transfer fabric by use of a vacuum or high pressure air jet.

12. A method as claimed in any of the preceding claims further comprising separating said dewatering/transfer fabric from said carrier fabric prior to said second drying zone, and transporting said web to said second drying zone on said dewatering/transfer fabric.

13. A method as claimed in Claim 12, further comprising adhering said web to a drying cylinder constituting the second drying zone, with creping adhesives, the adhesives being applied to the drying cylinder or to the web.

14. A method as claimed in Claim 12 or 13 further comprising continuously cleaning said dewatering/transfer fabric with water or steam jets positioned between said second drying means and said forming roll.