KR19980701951A - Process for making a through-dried crepe unprocessed tissue product without open draw - Google Patents

Abstract

The present invention describes a method for making a through dried crepe unprocessed tissue wherein the through dried tissue sheet 15 is fully supported by the fabric 18 to the reel 23. The method eliminates the open draw between the through dryer 13 and the reel 23, thereby eliminating sheet breaks typically associated with such open draw. In addition, it is possible to lower the machine direction strength of the sheet since the added strength is not required to traverse the open draw that is normally present in current methods. Lowering MD strength upon rotation can produce a more square, less stiff sheet, which improves the tactile properties of the product.

Description

Process for making a through-dried crepe unprocessed tissue product without open draw

In methods of making tissue products such as high quality tissues, bath tissues and paper towels, tissue base sheets typically coat an aqueous suspension of papermaking fibers on the forming fibers, dehydrate the suspension to form a web, dry the web and The dried web is made by winding up to rolls for continuous conversion into special product forms. During manufacture, most tissue webs are attached to a steam heated Yankee dryer and then removed from the Yankee's surface by contact with a doctor blade prior to conversion to improve sheet softness and elongation. Processing). More recently, throughdried uncreped soft tissue sheets have been described in which the softness and elongation are formed into sheets by other processing methods.

However, in all such methods, the final sheet traverses the open draw before being rolled up to a roll, which means that the dried sheet is not instantaneously supported before being rolled up. In the case of the creped sheet, the sheet is removed from the creping cylinder and passes through the unsupported material from the creping cylinder to the reel. For a through dried crepe unprocessed sheet, the sheet leaves the through dry fabric or subsequent transfer fabric and also passes through the unsupported material to the reel. As is known in the tissue manufacturing business, these unsupported advances, or open draws, are the cause of sheet breakage and manufacturing delay times. To replenish, the machine direction strength is designed to be high so that the tissue sheet remains complete during manufacture. However, such high strength is often unproductive in terms of softness and undesirable for end users of the product.

Thus, if the open draw could be removed during tissue manufacturing, the tissue could be produced more effectively in terms of waste and lag, and the machine direction strength of the final product could be lowered to the level indicated only by the product requirements rather than the manufacturing requirements. there was.

Summary of the Invention

In the present invention, it has now been found that in the manufacture of a through dried crepe unprocessed tissue sheet, the open draw between the through dryer and the reel can be removed by proper mixing of the dry end transfer fabric and / or other transfer devices. It turns out By doing so, tissue sheets with much lower machine direction strength can be produced, thereby providing a means for producing softer and more square tissue sheets in terms of machine direction and transverse machine direction tensile strength.

Thus, in one aspect, the invention covers an aqueous suspension of papermaking fibers on a forming fabric to form a wet web, transfer the wet web to a through dry fabric, dry dry the web to form a tissue sheet, and remove the tissue sheet. A method for making a through dried crepe unprocessed tissue, comprising transferring to a reel so that the sheet does not cross the open draw while being wound on a reel in a winding nip formed between the reel and reel drum. Exclusion of open draw can be achieved by transferring the tissue sheet directly from the through dry fabric to the reel drum or by intermediate transfer to one or more dry end transfer fabrics. This method is particularly advantageous at high machine speeds (about 2,000 or about 3,000 feet / minute or more) where relatively high MD tensile strength is required for the sheet to pass through the reel without being periodically destroyed.

Thus in another aspect, the present invention provides a tissue sheet comprising: (a) a vacuum roll is transferred from a through dry fabric to a first dry end transfer fabric; (b) a transfer between the first dry end transfer fabric and the surface of the second dry end transfer fabric having a relatively high degree of air permeability (at least about 200 cubic feet / minute / square foot), the bottom surface of which is around the reel drum Partially wrapped in; (c) is carried by the air pressure formed by an air foil carried on the surface of the second dry end transfer fabric and disposed thereon on the bottom surface of the second dry end transfer fabric; (d) to the method wound on a reel. More particularly, the air permeability of the second dry end transfer fabric may be about 200 to about 500 cubic feet / minute / square feet, still more particularly about 300 to about 400 cubic feet / minute / square feet. Air permeability, the airflow through the fabric, while maintaining a differential air pressure of 0.5 inches across the fabric is described in ASTM Test Method D737.

In a further aspect, the present invention provides a tissue sheet comprising: (a) transferring from a through dry fabric to a first dry end transfer fabric using a vacuum roll; (b) between the first dry end transfer fabric and the surface of the second dry end transfer fabric having an air permeability of about 100 cubic feet / minute / square foot or less, the bottom surface of which is partially wrapped around the reel drum; (c) conveyed to the surface of the second dry end conveying fabric; (d) to the method wound on a reel. More particularly, the air permeability of the second dry end transfer fabric is from 0 to about 100 cubic feet / minute / square foot, more particularly from about 25 to about 100 cubic feet / minute / square foot, still more particularly from about 50 to about 100 cubic feet. It can be / minutes / square feet.

In another aspect, the invention provides a kit comprising: (a) a headbox for coating an aqueous suspension of papermaking fibers on a forming wire; (b) a continuous forming fabric for receiving an aqueous suspension of papermaking fibers for the formation of a wet web; (c) a continuous conveying fabric disposed adjacent to the forming fabric to enable transfer of the wet web from the forming fabric to the conveying fabric; (d) means for transferring the wet web from the forming fabric to the conveying fabric; (e) a rotatable through drying cylinder for drying the wet web; (f) a continuous through dry fabric at least partially wrapped around the through dryer and disposed adjacent the transfer fabric to enable transfer of the wet web from the transfer fabric to the through dryer fabric; (g) means for transferring the wet web from the transfer fabric to the through dry fabric; (h) a rotatable reel for winding the dried web; (i) a reel drum adjacent to the reel to assist in winding the dried web; And (j) means for transferring the dried web from the through dry fabric to the reel without open draw. 2. A paper machine for continuously producing a through dried crepe unprocessed paper web.

In a further aspect, however, the present invention provides a continuous first disposed means adjacent to the through dryer fabric such that the means for transferring the web from the through dry fabric to the reel can (a) transfer the dried web to the first dry end transfer fabric. Dry end transfer fabric; (b) a continuous loop of a second dry end transfer fabric disposed adjacent to the first dry end transfer fabric such that the dried web is interposed between the first and second dry end transfer fabrics, wherein the second dry end transfer The fabric loop is around the reel drum and its air permeability is at least about 200 cubic feet / minute / square foot); And (c) an air foil disposed in a loop of the second dry end transfer fabric and adjacent to the second dry end transfer fabric forming an air pressure for maintaining the dried web in contact with the second dry end transfer fabric. It's about papermaking.

In still a further aspect, the invention provides a continuous first disposed means adjacent to a through dryer fabric such that the means for transferring the web from the through dry fabric to the reel can (a) transfer the dried web to the first dry end transfer fabric. Dry end transfer fabric; And (b) a continuous loop of second dry end transfer fabric disposed adjacent to the first dry end transfer fabric such that the dried web is interposed between the first and second dry end transfer fabrics, wherein the second dry end transfer The conveying fabric loop is around the reel drum, and its air permeability is about 100 cubic feet / minute / square feet or less.

In another aspect, the invention relates to a paper machine comprising a reel drum disposed close enough adjacent to the through dryer fabric such that the means for transferring the web from the through dryer fabric to the reel can transfer the dried web to the reel drum. It is about.

In another aspect, however, the present invention includes a vacuum drum disposed close enough adjacent to a through dry fabric such that the means for transferring the web from the through dryer fabric to the reel can transfer the dried web to a vacuum drum. The drum relates to the above paper machine which is disposed adjacent to the reel drum so as to transfer the dried web from the vacuum drum to the reel drum.

These and other aspects of the invention will be described in more detail with reference to the accompanying drawings.

1 is a schematic flow diagram illustrating a method for making a non-creped unwrapped tissue sheet in a typical manner of the prior art using open draw in front of the reel.

2 is a schematic flowchart of a method for producing a through dried crepe unprocessed tissue sheet according to the present invention using a highly permeable stretched fabric.

3 is a schematic flow diagram of a method for producing a through dried crepe unprocessed tissue sheet according to the present invention using an elongated permeable fabric.

4 is a schematic flow diagram of a method for producing a through dried crepe unprocessed tissue sheet according to the present invention using a single drum for winding the sheet directly from the through dry fabric.

5 is a schematic flow diagram of a method for producing a through dried crepe unprocessed tissue sheet according to the present invention using two drums for winding the sheet directly from the through dry fabric.

FIG. 6 is a plot showing geometric mean tensile strength (GMT) / layer versus MD tensile strength / layer for various commercial high grade tissues, bath tissues and towels, as well as several examples made by the method of the present invention.

In describing the various figures herein, the same apparatus will be described using the same reference numerals. To avoid the hassle, the detailed description of many of the devices shown in FIG. 1 is not repeated in the description of the subsequent figures, but such devices are denoted by the same reference numerals.

First, referring to FIG. 1, there is shown a schematic flow chart of a typical through drying method for making a through dried crepe unprocessed tissue. A headbox 1 is shown which covers an aqueous suspension of papermaking fibers on the forming fabric 3 as the inner forming fabric 3 traverses the forming roll 4. The outer forming fabric 5 acts to contain the web while it is passing over a forming roll and splashing some water. The wet web 6 is then conveyed from the inner forming fabric to the wet end conveying fabric 8 with the aid of a vacuum conveying shoe 9. This transfer is preferably carried with the transfer fabric traversing at a slower rate than the forming fabric (rush transfer) to impart elongation to become the final tissue sheet. The wet web is then transferred to the through dry fabric 11 with the aid of a vacuum transfer roll 12. The through dry fabric carries the web onto the through dryer 13 and blows the heat through the web to dry it while preserving its volume. Depending on the speed and dryer capacity, one or more of a series of through dryers (not shown) may be present. The dried tissue sheet 15 is then conveyed to the first dry end transfer fabric 16 with the aid of a vacuum transfer roll 17. The tissue sheet immediately after the transfer is interposed between the first dry end transfer fabric and the second dry end transfer fabric 18 to reliably control the sheet passage. The tissue sheet leaves the transfer fabric and traverses the open draw, designated 20, at which point the sheet is not supported. The sheet then passes through the winding nip between the reel drum 22 and the reels 23 and is wound up to be a roll 25 of tissue for subsequent switching such as longitudinal slitting, cutting, folding and wrapping. do.

2 is a schematic flowchart of a method according to the invention, in which the open draw leading the reel is eliminated. The front end of the method is the same as shown in FIG. When the tissue sheet leaves the through dryer fabric, it is transferred to the first dry end transfer fabric 16 with the aid of a vacuum transfer roll 17. Fabrics suitable for use as the first dry end transfer fabric 16 include, but are not limited to, a wide variety of fabrics such as Asten 934, Asten 939, Albany 59M, Albany Duotex DD207, Lindsay 543, and the like. The tissue sheet is then compressed between the first dry end transfer fabric and the second dry end transfer fabric 18, the air permeability of which is greater than the air permeability of the first dry end transfer fabric, which is around the reel drum 22. Wind up at. Suitable second dry end transfer fabrics include, but are not limited to, Asten 960 (air permeability about 300 to 400 cubic feet / minute / square foot), Appleton Mills style Q53F (air permeability about 400 cubic feet / minute / square foot) , Appleton Mills style Q53KY (about 200 cubic feet / minute / square foot of air permeability), Albany Duotex A81 and Appleton Mills style HC200 (about 200 cubic feet / minute / square foot of air permeability). Because of the airflow through the lower fabric caused by the roll 31, the sheet is conveyed to the second dry end conveying fabric 18. It is retained on the surface of the second dry end transfer fabric by the air pressure generated by the presence of the air foil 30 on the bottom of the fabric. The tissue sheet is then conveyed to a winding nip formed between the reel drum and the reels 23 and wound up to become a roll 25.

FIG. 3 shows another embodiment of the method of the invention similar to that shown in FIG. 2, although the permeability of the second dry end transfer fabric is much lower than the corresponding fabric used for the method of FIG. 2. By lowering the permeability of the second dry end conveying fabric, the lower permeability of the second fabric tends to naturally adhere to the fabric, thereby eliminating the need for air foil. At the point of separation, the sheet follows the fabric of lower permeability due to the vacuum action. There is no air pumped through the fabric by the various rolls and no foil is needed. Low air permeability fabrics suitable for this embodiment include, but are not limited to, Asten 960 dryer fabrics (air permeability about 50 to 100 cubic feet / minute / square feet), COFPA Mononap NP 50 dryer felt (air permeability about 50 cu) Feet / minute / square feet) and Appleton Mills Dryer Felt Style H53FH (air permeability about 75 cubic feet / minute / square feet).

4 is a schematic flow diagram of another method according to the invention in which the tissue sheet 15 is transferred from the through dry fabric 11 directly to the reel drum 22. This is done by vacuum suction from the reel drum and / or pressurized air therefrom. Next, the tissue sheet is wound onto the reels 23 so as to be a roll 25. An advantage of the method over the advantages of FIGS. 2 and 3 is the removal of the dry end transfer fabric.

FIG. 5 shows a vacuum drum 26 for conveying the tissue sheet 15 from the through-drying fabric 11 and passing it over the reel drum 22 to wind it up onto the reel 23 to be a roll 25. A schematic flowchart of an alternative method in accordance with the present invention similar to that shown in FIG. 4. The nip between the rolls 22 and 26 may be configured for calendaring.

6 is expressed as geometric mean tensile strength / layer versus MD tensile strength / layer (g-force / 3 inch sample width) for several commercial high-quality tissues, bath tissues, and towels, as well as several examples made with the present invention. ) Is a plot. Numbers 1, 2 and 3 represent commercially available high quality, bathroom and towel products in one, two and three layer constructions. Letters A through E mean the tissue product prepared in Example 1. Data points A and B show the ability of the present invention to consistently manufacture and reel up low strength tissue webs in particular. While other low intensity tissues are present, it is well known that their manufacture typically entails reduced machine speeds and effects. The present invention allows such tissues to be produced at high speeds (more than 3,000 feet / minute) with little or no effect loss due to dry end sheet failure.

Example 1

To further illustrate the invention, several rolls of low strength through dried crepe unprocessed tissue were prepared on a commercial tissue machine using substantially the same method as shown in FIG. 1. More specifically, a three-layered single-layer bath tissue was prepared in which the outer layer was composed of dispersed and debonded Aracruz eucalyptus fibers, and the central layer was composed of refined coniferous kraft fiber (NB-50) in the northern region.

Prior to formation, eucalyptus fibers were pulped at 10% hardness for 15 minutes and dehydrated to 30-40% hardness. The pulp was then fed to a Maule shaft disperser operated at 194 ° F. (90 ° C.) with a power input of 3.2 horsepower-day / ton (2.6 kPa-day / ton). Subsequent to dispersion, a softener (Berocell 596) was added to the pulp in an amount of 15 pounds of Verocell / tonne of dry fiber (0.75 wt.%).

The coniferous fibers were pulped to 7% hardness for 30 minutes, diluting the dispersed and debonded eucalyptus fibers to 3.5% hardness, and diluted to 3.5% hardness after pulping. The total weight of the layered sheet was separated by 30% / 40% / 30% in the dispersed eucalyptus / refined softwood / dispersed eucalyptus layer. While the outer layer provided surface softness and volume, the central layer was refined to the level necessary to achieve the target strength value. Parez 631NC was added to the core layer at 11 pounds (5.0 kg) / pulp tone based on the center layer.

Three-layer headboxes were used to form a wet web with refined coniferous kraft stems in the northern provinces in the central layer of the headbox to produce a single central layer for the three-layered article described. A turbulent forming insert that was concave about 3 inches (75 mm) from the slope and a layer distributor that stretched about 6 inches (150 mm) beyond the slope were used. The pure sloped opening was about 1.22 inches (31 mm) with a water flow rate at the center layer about 2 times that of each outer layer. The hardness of the stems fed to the headbox was about 0.1% by weight.

The resulting three-layered sheet was formed on a twin-wire, a suction form roll, wherein the twin-wires (5 and 3 in FIG. 1) with the forming fabric were Asten 866 and Asten 856 fabrics, respectively. The speed of the forming fabric was 15.2 m / sec. The newly formed web was then dewatered from below the forming fabric to a hardness of about 20-27% using vacuum suction before transferring to the conveying fabric, which was transferred at 11.7 m / sec (30% rush feed). The transfer fabric was Albany Duotex R-12. The web was transferred to a transfer fabric using a vacuum shoe that attracted with a mercury vacuum of about 6 to 15 inches (150 to 380 mm).

The web was then transferred to a through dry fabric (Lindsay Wire T-216-3). The through dry fabric was transferred at a speed of about 11.7 m / sec (about 2,200 feet / minute). The web was conveyed on a Honeycomb through dryer operating at a temperature of about 350 ° F. (175 ° C.) and dried to a final dryness of about 98% hardness.

The web was then taken with a reel with no opportunity for open draw according to the high permeability fabric schematic shown in FIG. 2. The first dry end transfer fabric was Asten 960, while the second dry end transfer fabric was Albany Duotex A81. The second dry end conveying fabric was 410 cubic feet / minute / square foot with a water differential of 0.5 inches of air permeability. The foil was needed at the separation point of the first and second dry end transfer fabrics under the second dry end transfer fabric. This foil formed a low pressure area under the second dry end conveying fabric and allowed the sheet to follow the present fabric.

Several low strength webs that were through-dried crepe-free were made under these conditions. All were about 30 g / m 2 by weight. Intensity parameters were as shown in Table 1.

MD tensile force MD Elongation CD tensile force CD Elongation GMT 1-A 333 15 185 8.9 248 1-B 388 16 199 9.8 277 1-C 535 18 289 12.6 389 1-D 560 18.5 249 9.9 373 1-E 805 20 466 10.9 612

This data is shown as points A to E in FIG. 6. It demonstrates the ability of the present invention to commercially produce and wind low strength tissue webs.

It is to be understood that the above examples provided for purposes of explanation are not to be considered as limiting the scope of the invention as defined by the following claims and all equivalents thereof.

Claims (18)

An aqueous suspension of papermaking fibers was coated on the forming fabric to form a wet web, Transfer the wet web to the through dry fabric, Through-drying the web to form a tissue sheet, The tissue sheet is transferred to the reel so that the sheet does not cross the open draw while the sheet is wound on the reel in the winding nip formed between the reel and reel drum. A method of making a through dried crepe unprocessed tissue, comprising the steps of: The tissue sheet of claim 1, wherein the tissue sheet is (a) transfer from the through dry fabric to the first dry end transfer fabric using a vacuum roll; (b) is carried between the surfaces of the first dry end transfer fabric and the second dry end transfer fabric, the bottom surface of which is partially wrapped around the reel drum; (c) is conveyed to the surface of the second dry end conveying fabric and maintained by air pressure formed by an air foil disposed thereon on the bottom surface of the second dry end conveying fabric; (d) wound on a reel Way. The method of claim 2, wherein the air permeability of the second dry end transfer fabric is at least about 200 cubic feet / minute / square foot. The method of claim 2, wherein the air permeability of the second dry end transfer fabric is from about 200 to about 500 cubic feet / minute / square foot. The method of claim 2 wherein the air permeability of the second dry end transfer fabric is from about 300 to about 400 cubic feet / minute / square foot. The tissue sheet of claim 1, wherein the tissue sheet is (a) transfer from the through dry fabric to the first dry end transfer fabric using a vacuum roll; (b) is carried between the surfaces of the first dry end transfer fabric and the second dry end transfer fabric, the bottom surface of which is partially wrapped around the reel drum; (c) conveyed to the surface of the second dry end conveying fabric; (d) wound on a reel Way. The method of claim 5, wherein the air permeability of the second dry end conveying fabric is about 100 cubic feet / minute / square foot or less. The method of claim 5 wherein the air permeability of the second dry end transfer fabric is from about 25 to about 100 cubic feet / minute / square foot. The method of claim 5, wherein the air permeability of the second dry end transfer fabric is from about 50 to about 100 cubic feet / minute / square foot. The method of claim 1 wherein the tissue sheet is transferred directly from the through dry fabric to the reel drum and wound on a reel. The method of claim 1 wherein the tissue sheet is transferred directly from the through dry fabric to the first reel drum and then immediately transferred to the second reel drum and wound up on the reel. The method of claim 1 wherein the tissue sheet has a speed of at least about 2,000 feet / minute. The method of claim 1 wherein the tissue sheet has a speed of at least about 3,000 feet / minute. (a) a headbox for coating an aqueous suspension of papermaking fibers on a forming wire; (b) a continuous forming fabric for receiving an aqueous suspension of papermaking fibers for the formation of a wet web; (c) a continuous conveying fabric disposed adjacent to the forming fabric to enable transfer of the wet web from the forming fabric to the conveying fabric; (d) means for transferring the wet web from the forming fabric to the conveying fabric; (e) a rotatable through drying cylinder for drying the wet web; (f) a continuous through drying fabric disposed at least partially around the through dryer and disposed adjacent the transfer fabric to transfer the wet web from the transfer fabric to the through dryer fabric; (g) means for transferring the wet web from the transfer fabric to the through dry fabric; (h) a rotatable reel for winding the dried web; (i) a reel drum adjacent to the reel to assist in winding the dried web; And (j) means for transferring the dried web from the through-dry fabric to the reel without open draw A paper machine for continuously producing a through-dried crepe unprocessed paper web comprising a. The method of claim 1 wherein the means for transferring the web from the through dry fabric to the reel is (a) a continuous first dry end transfer fabric disposed adjacent to the through dryer fabric to transfer the dried web to the first dry end transfer fabric; (b) a continuous loop of a second dry end transfer fabric disposed adjacent to the first dry end transfer fabric such that the dried web is interposed between the first and second dry end transfer fabrics, wherein the second dry end transfer Fabric loops are around the reel drum and have air permeability of at least about 200 cubic feet / minute / square foot); And (c) an air foil disposed in a loop of the second dry end conveying fabric and adjacent to the second dry end conveying fabric, which creates an air pressure to maintain the dried web in contact with the second dry end conveying fabric. Paper machine comprising a. The method of claim 1 wherein the means for transferring the web from the through dry fabric to the reel is (a) a continuous first dry end transfer fabric disposed adjacent to the through dryer fabric to transfer the dried web to the first dry end transfer fabric; And (b) a continuous loop of a second dry end transfer fabric disposed adjacent to the first dry end transfer fabric such that the dried web is interposed between the first and second dry end transfer fabrics, wherein the second dry end transfer The fabric loop is around the reel drum with air permeability less than about 100 cubic feet / minute / square foot) Papermaking comprising a. 2. The paper machine of claim 1, wherein the means for transferring the web from the through dryer fabric to the reel comprises a reel drum disposed close enough close to the through dryer fabric to transfer the dried web to the reel drum. The vacuum drum of claim 1, wherein the means for transferring the web from the through dryer fabric to the reel comprises a vacuum drum disposed close enough adjacent to the through drying fabric to enable transfer of the dried web to the vacuum drum. And a paper machine disposed adjacent to the reel drum so that the web can be transferred from the vacuum drum to the reel drum.