GB2132141A

GB2132141A - Embossing

Info

Publication number: GB2132141A
Application number: GB08333874A
Authority: GB
Inventors: Robert N Bauernfeind
Original assignee: Kimberly Clark Corp
Current assignee: Kimberly Clark Corp
Priority date: 1982-12-20
Filing date: 1983-12-20
Publication date: 1984-07-04
Also published as: PH25916A; DE3345886A1; GB2166690B; BR8306949A; ZA839109B; MX157490A; KR920000755B1; GB8529068D0; AU2217483A; CA1243233A; GB8333874D0; FR2537920B1; JPS59116500A; FR2537920A1; GB2132141B; KR840007043A; GB2166690A; AU562754B2

Abstract

A matched-steel embossed multi- ply paper sheet (9), particularly suitable for use as a paper towel, comprises an embossing pattern having a background arrangement of alternately protruding and depressed deflected zones (10 and 11) spaced apart by a substantially undeflected neutral plane (12). The embossments on the paper sheet may have a major and a minor axis, the major axis of substantially all of the embossments being substantially aligned in the cross machine direction (e.g. Figure 4). <IMAGE>

Description

SPECIFICATION Embossing process and product This invention relates to the manufacture of paper towels and the like. More particularly, it relates to methods of embossing multi-ply paper sheets.

It is well known in the papermaking industry that embossing a paper sheet gives the sheet bulk, a property that is of particular importance in manufacturing paper towels because it is associated with softness and absorbency by the consumer. Bulk is not only important with regard to the feel of the individual sheets, but also in regard to the bulkiness of the packaged product. In the case of paper towels, where the product is packaged in rolls it is desirable to minimize nesting of the sheets within one another in order to maintain a larger roll diameter with a given number of sheets per roll.

In manufacturing multi-ply paper sheets, there are basically two processes which are well known in the art. One is a nested process and the other is a pillowed process. The nested process is illustrated by U.S. Patent No. 3,694,300 and U.S. Patent No.

3,867,225 and generally involves the separate embossing of two plies between a rubber roll and a steel embossing roll, applying an adhesive with a roller to the protruding embossments of one of the plies, and combining the two plies together such that the protrusions of one sheet are attached within the depressions of the other.

The pillowed process is similar and is illustrated by U.S. Patent No.3,961,119. In this process, however, the plies are laminated together such that protrusions of one ply are not aligned within the depressions of the other. In both of these processes, it is necessary to have two rubber/steel nips and an adhesive applicator of the roller type. These systems are unnecessarily cumbersome.

The use of embossed designs to improve the aesthetic appear of the product is also known in the art, as illustrated by U.S. Design No. 262,747 which shows a shamrock design.

It is an object of the invention to overcome or mitigate one or more of the above problems.

In one aspect the invention resides in a multi-ply paper sheet, particularly suitable for use as a paper towel, having first and second sides and an embossed pattern thereon, the embossed pattern comprising a background arrangement of alternately protruding and depressed deflected zones spaced apart by a substantially undeflected neutral plane, wherein the depressed and and protruding deflected zones of the first side correspond to the protruding and depressed deflected zones, respectively, of the second side.

In a further aspect, the invention resides in a method for producing paper towels comprising embossing a preattached multi-ply web with matched steel rolls and imparting to the web a pattern of alternately protruding and depressed deflected zones separated by a substantially undeflected neutral plane. The matched steel rolls provide more control over bulk formation, have reduced energy requirements, cause lesser static build-up, and last longer than rubber/steel rolls.

This invention has a primary advantage over prior processes and products in that it produces a onesided product (both sheet sides have similar appearance and feel). It also reduces nesting which is accomplished by incorporating a design into the background pattern which has increased unembossed area (neutral plane) and/or arrangement of elements within this design on a dissimilar grid relative to the background pattern. The elements within the design can also have a different size, shape or orientation compared to the background pattern, thereby further reducing the opportunity to nest with the background pattern.

In a further aspect, the invention resides in an embossed paper sheet wherein substantially all of the embossments (deflected areas corresponding to the embossing elements on the embossing rolls) have a major and minor axis and wherein the major axis is substantially aligned in the cross-machine direction (C.D.). Suitable embossment shapes include ovals, diamonds, rectangles, etc. as well as unsymmetrical or irregular shapes. Aligning the major axis in the C.D. direction has been found to reduce C.D. strength degradation caused by the embossing. For purposes herewith, "substantial" alignment in the C.D. direction means within about 10 of the C.D. direction. A lesser degree of alignment is believed to have relatively minimal benefits.

"Substantially all of the embossments" means at least 80 percent of the background embossments of the embossing pattern. A lesser percentage of the embossments having proper alignment also would result in minimal benefit in terms of reducing strength degradation.

The invention will now be described, byway of example, with reference to the accompanying drawings in which: Figure 1 is a schematic view of a process in accordance with this invention.

Figure 2 is a cross-sectional representation of the profile of a two-ply web in accordance with this invention.

Figure 3 is a plan view of one embodiment of a paper sheet in accordance with this invention, illustrating successive curvilinear rows of background embossments.

Figure 4 is a plan view of a second embodiment of a paper sheet in accordance with this invention, illustrating alignment of the major axis of the background embossments in the cross-machine direction.

Directing attention to Figure 1, the invention will be described in more detail. Figure lisa schematic view illustrating the manner in which the paper sheets of this invention are produced. Separate rolls 1 and 2 feed webs to be attached between nip rolls 4 and 5. At least one of the webs is provided with an adhesive, preferably in the form of a spray 3, as shown. In the nip the two webs are bonded together to form a preattached sheet 6. Although not shown, the preattached sheet 6 can be wound up on a hardroll to be subsequently used as a feed roll for the embossing step to permit flexibility due to varying production speeds. The preattached sheet is then directed between matched steel embossing rolls 7 and 8 wherein the desired embossing pattern is imparted to the preattached sheet resulting in the embossed sheet 9.It will be appreciated that the manner in which the preattached sheet is formed is not to be considered as limiting the scope of the invention. For example, the multi-ply sheet can be formed by folding a single web and cutting off the fold to produce a two-piy sheet, rather than supplying each ply from a separate roll as shown in Figure 1. In addition a sheet containing more than two plies can also be embossed in accordance with this invention, as long as the plies are sufficiently bonded together, either mechanically or with adhesive, to maintain the integrity of the sheet through the embossing process.This is necessary because the embossing process does not provide sufficient ply attachment, it being an object of the process not to damage the sheet by punching through the sheet with the embossing rolls which, if it occurred, would provide some degree of ply attachment in and of itself.

Figure 2 illustrates a cross-section of a portion of the embossed sheet 9 of Figure 1. Shown are the protruding deflected zones 10, the depressed deflected zones 11, and the substantially undeflected neutral plane 12 of the 2-ply sheet. In a preferred embodiment, the height of the protrusions 10 and the depth of the depressions 11 is about .016 inch.

The deflected zones, when viewed from the top or bottom of the sheet, are oval in shape and have a length (major axis) of about 0.075 inch and a width (minor axis) of about 0.035 inch. The width of the neutral plane 12, i.e. the distance between deflected zones 10 and 11, is about 0.035 inch or greater. It is preferred that the spacing of the deflected zones be at least as great as the dimension of the minor axis in those instances when the deflected zones are generally elongate in shape. If the deflected zones are generally circular in shape, the spacing is preferably at least as great as the diameter. It will be appreciated that the precise spacing and shape of the deflected areas can vary depending upon the strength and aesthetic requirements of the sheet.

Also shown by Figure 2 is the corresponding relationship between the protrusions and depressions on one side of the sheet relative to the depressions and protrusions on the other side of the sheet.

Figure 3 is a plan view of an embossed sheet made in accordance with Figures 1 and 2 illustrating an intermittent shamrock embossing pattern. The black ovals represent protruding deflected zones and the white ovals represent depressed deflected zones.

The white background area represents the substantially undeflected neutral plane. As shown,the oval-shaped deflected zones are arranged to form a background pattern comprising successive curvilinear rows of alternately protruding and depressed deflected zones spaced apart by the neutral plane.

The background pattern need not be curvilinear, but such a pattern is advantageous in that it approximates a random pattern and reduces the tendency of the sheets to nest when wound up into rolls.

In addition, the intermittent shamrock pattern also reduces the nesting tendency. As previously mentioned, reduced nesting improves the bulky feel of the rolled product. As shown, the shamrock pattern is essentially a neutral plane pattern containing oval-shaped protruding and depressed zones having their major axis aligned in a direction different from that of the ovals in the background pattern. This further aids in retarding nesting.

Figure 4 illustrates a similar embossing design as shown in Figure 3, except the major axis of the background ovals has been rotated 90 , parallel to the cross-machine direction of the webs comprising the sheet. This orientation has been found to decrease the cross-machine direction strength degradation due to embossing.

Example In making a two-ply embossed towel, two softrolls containing suitable single-ply webs were produced on a paper machine using typical paper industry equipment and practices. The softrolls were unwound and the two single-ply base sheets were plied together by spraying a polyvinyl acetate adhesive between them and passing them between press rolls having a loading of about 20-40 pli. The polyvinyl acetate adhesives had a solids content of about 15-30 weight percent. Typically, about 7-15 Ibs. of adhesive solids per ton of base sheet are used for a base sheet having a finished basis weight of 10-14 lbs./2880 ft.2 per ply. The resulting two-ply sheet was rewound into a hardroll at speeds of about 25004500 feet per minute.

The two-ply hardrolls were converted into a finished product using standard paper towel converting equipment, excepting the embossing rolls.

The two-ply sheet was unwound and passed between matched-steel embossing rolls at speeds of about 1300-1800 feet per minute. The embossing rolls had a diameter of about 14-16 inches and a width of about 99 inches. The embossing rolls were mated in the same position in which they were matched-steel engraved and were of the design shown in Figure 4. The embossing rolls were set at about 0.007-0.020 inches off bottom clearance and adjusted for no steel-to-steel contact. Ply attachment of the final product therefore resulted from the adhesive rather than the embossing.

The dimensions of the oval embossing pattern elements were as follows: major axis of oval (0.070 inch); minor axis of oval (0.035 inch); M.D. direction element-to-element spacing (0.065 inch); C.D. direction element to element spacing (0.048 inch); and element depth (0.050 inch). These dimensions can vary about 10 percent across the pattern.

The embossed sheet was then passed through a printing operation, perforated, and wound into finished logs having the desired sheet count. The logs were then cut into segments of the desired width and wrapped.

Claims

1. A multi-ply paper sheet having first and second sides and an embossed pattern thereon, the embossed pattern comprising a background arrangement of alternately protruding and depress ed deflected zones spaced apart by a substantially undeflected neutral plane, wherein the depressed and protruding deflected zones of the first side correspond to the protruding and depressed deflected zones, respectively, of the second side.

2. A paper sheet as claimed in Claim 1 wherein the background deflected zones are arranged in successive curvilinear rows.

3. A paper sheet as claimed in either Claim 1 or Claim 2 wherein the deflected zones are generally elongate in shape having major and minor axis dimensions.

4. A paper sheet as claimed in Claim 3 wherein the spacing of the deflected areas is at least as great as the minor axis dimension.

5. A paper sheet as claimed in any preceding claim wherein the deflected zones are oval in shape.

6. A paper sheet as claimed in Claim 5 wherein the major axis of the oval deflected zones is aligned in the machine direction.

7. A paper sheet as claimed in either Claim 5 or Claim 6 wherein the dimension of the major axis is about 0.075 inch (0.19 cm), the dimension of the minor axis is about 0.035 inch (0.089 cm), and the spacing between adjacent oval deflected areas is about 0.035 inch (0.089 cm).

8. A paper sheet as claimed in Claim 5 wherein the major axis of the oval deflected zones is aligned in the cross-machine direction.

9. A two-ply paper towel having first and second sides and having an embossed background pattern thereon, the embossed pattern comprising successive curvilinear rows of alternately protruding and depressed oval-shaped deflected zones oriented with the major axis of the oval aligned in the cross-machine direction and spaced apart by a substantially undeflected neutral plane wherein the depressed and protruding deflected zones of the first side correspond to the protruding and depressed deflected zones, respectively, of the second side.

10. A paper towel as claimed in Claim 9 wherein the embossed pattern further comprises an intermittent neutral plane pattern containing oval-shaped protruding and depressed deflected zones having the major axis of the ovals aligned in a direction different than that of the ovals in the background pattern.

11. A paper towel as claimed in Claim 10 wherein the intermittent neutral plane pattern defines a shape suggestive of a shamrock.

12. A method for producing paper towels com- prising embossing a preattached multi-ply web with matched steel rolls each roll having a pattern of alternately protruding and depressed deflected zones separated by a substantially undeflected neutral plane.

13. An embossed paper sheet wherein the embossments have a major and minor axis and wherein the major axis of substantially all of the embossments is substantially aligned in the crossmachine direction.

14. A paper sheet as claimed in Claim 13 wherein the embossments are oval, rectangular, or diamondshaped.

15. A paper sheet as claimed in Claim 13 wherein the major axis is parallel to the cross-machine direction.

16. A paper sheet or towel substantially as herein described with reference to Figures 1 to 3 and 4 of the accompanying drawings.

17. A method for producing papertowelssubstantially as herein described with reference to Figure 1 of the accompanying drawings.