CA1243233A

CA1243233A - Embossing process and product

Info

Publication number: CA1243233A
Application number: CA000442579A
Authority: CA
Inventors: Robert N. Bauernfeind
Original assignee: Kimberly Clark Corp
Current assignee: Kimberly Clark Worldwide Inc
Priority date: 1982-12-20
Filing date: 1983-12-05
Publication date: 1988-10-18
Also published as: GB8333874D0; JPS59116500A; MX157490A; GB2132141B; FR2537920A1; AU2217483A; BR8306949A; PH25916A; GB2166690B; AU562754B2; DE3345886A1; KR920000755B1; ZA839109B; GB2132141A; KR840007043A; GB2166690A; GB8529068D0; FR2537920B1

Abstract

ABSTRACT
A matched-steel embossed multi-ply paper sheet, particularly suitable for use as a paper towel, comprises an embossing pattern having a background arrangement of alternately protruding and depressed deflected zones spaced apart by a substantially undeflected neutral plane.

Description

3~3 BACKGROUND OF THE INVENTION
-FIELD OF THE INVENTION
This invention relates to the manufacture of paper towels and the like. More particularly, it relates to methods of embossing multi-ply paper sheets.

BRIEF DESCRIPTION OF THE PRIOR ART
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.

2~ One is a nested process and the other is a pillowed process.
The nested process is illus~rated by U.S. 3,694,300 to Small and U.S. 3,867,225 to Nystrand 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 -2- ~

of one ~heet are attached withln the depre~slon~ of the other.

The pillowed procesa i8 similar and i8 illuRtrated by U.S.

3,961,119 to Thomas. ~n this process, however, the plias are lamlnated together such that the protrusions of one ply are not aligned wi~hin the depressions of ~he other. In both of the~e processes, it is necessary to have two rubber/steel nips and an adhesive applicator of the roller type. These ~ystems are unnecessarily cumbersome.
The u~e of embos~ed deQigns to improve the ae~thetlc appeal of the product ls al~o known in the art, as illustrated by U.S.
Des. 262,74~ to Erickson which show~ a shamrock design.

In one aspect the invention resides in a multi-ply paper sheet, particularly sultable for use as a paper towel, having first and second sides and an embossed pattern thereon, said embos~ed pattern compris~ng a background arrangement o~ alter-nate~ly protruding and depre~sed deflected zones spaced apart by a subE~tantially undeflected neutral plane. The deflected zone~ are generally elongated in Qhape having ma~or and minor axis dlmen-8ion~ wherein the ma~or axl~ is substantially aligned in the cro~s-machine direction. The depre~sed and protruding deflected zone~ of the first side correQpond ~o the protruding and depressQd deflectlve zones, re~pectively, of the ~econd ~lde.

A speci~lc embodlment of 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 zon~s ~eparated by a sub~tantially undeflected neutral plane. The matched steel rolls provide more control over bulk forma~ion, have reduced energy requirements, cause lesser ~tatic build-up, and last longer than rubber/steel rolls.

e ~3~33 This invention has a primary advantage over prior processes and products in that it produces a one-sided product (both sheet sides have similar appearance and feel). It also reduces nesting which is accomplished by incorporating a design into the back-ground pattern which has increased unembossed area (neutral plane) and/or arrangement Or elements within this design on a dissimilar grid relative to the background pattern. The elements within the design can also have a diferent size, shape, or orientation compared to the background pattern, thereby further reducing the opportunity to nest with the background pattern, According to another aspect of the invention there is provided an embossed paper sheet of the creped paper type for paper towels and tissue. the shee-t having embossments in a pattern with an evenly spaced background. The embossments have major axis and minor axis, the major axis of substantially all of the embossments being substantially aligned in the cross machine direction.

Suitable embossment shapes include ovals, diamonds, rec-tangles, 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 the purpose herein, "substantial" alignment in the C.D. direc-tion means within about 10 of the C.D. direction. A iesser 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 degrada-tion.

~3 ~ 4~33 BRIEF DESCRIPTION OF TH~ DRAWrNG

Figure 1 i8 a schemat~c view o a process in accordance with this invention.

Figure 2 i9 a cros~-sectional repr*sentation of the proPile of a two-ply web in accordance with this invention.

~ igure 3 1B a plan view illustratlng succe~sive curvilinear rows of background embos~ments.

Figure 4 i~ a plan view o~ a paper shaet in accordance with thi~3 inventlon, illustratlng alignm~nt of the ma~or axiQ of the background embossments in the cross-machine direction.

DETAILED DESCRIPTION OF T~E DRAWING

Directing attention to Figure 1, the invention will be described ln mora detail. Figure 1 i8 a schematic . .

3~33 view illustrating the manner in which the paper sheets of this invention are produced. Separate rolls 1 and 2 feed web~ 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-ply 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 necessarv 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 !L 2~3~33 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 .01~ 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 pre~erred 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 ~ones are generally elongate in shape~ If the deflected zones are generally circular in shape, the spacing is pre~erably 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 depressi~ns and protrusions on the other side of the sheet.

~12~3~3~

Figure 3 i~ a plan view lllustrating an intermittent shamrock embos~ing pattern~ The black ovals represent protruding deflected zones and the white oval~ repre~ent depres~ed deflected zones. The whi~e background area represents the sub~tantlally undeflected neutral plane. As shown, the oval-shaped de~lect~d zones are arranged to ~orm a background pattern comprising succes3ive curvilinear row~ of alternately protruding and depre3~ed deflected ~ones spaced apart by the neutral plane. The background pattern need not be curvilinear, but ~uch a patt2rn 1 advantageous in tha~ lt a~proximate~ a random pa~tern and reduce~
the tendency of the sheets to nest when wound up into rolls.

In addition, the intermittent shamrock pattern al80 reduces the nesting tendency. AB previou~ly mentloned, rcduced ne~in~
improves the bulky ~eel of the rolled product~ As sho~m the shamrock pattern i~ es~entlally a neutral plane pattern contain-ing oval-shaped protruding and depressed zones having their ma~or axi~ alignsd in a directlon different from that of the oval~ in the background pattern. This ~urther aids in retarding ne~ting.

Figure 4 ~llu~trate~ an embossing de~ign of the present invention and i8 different than that shown in Flgure 3 in that the ma~or axis o~ the background ovals has been rotat~d 90, parallel to the cross-machine directlon of the webs compri~ing the ~heet. This lZ~3~33 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 percen~. Typically, about 7-15 lbs. 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 2500-4500 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 ~2~3~33 adjusted for no steel-to-steel contactO 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 inch1;
minor axis of oval (0.035 inch); M.D. direction element-to-element spacing 10.065 inch); C.D. direction element-to-element spacing (0.048 inch); and element depth (0.050 inch)~ ~hese dimensions can vary about + lO 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.
It will be appreciated that the specific designs shown for purposes of illustration are not to be construed as limiting the scope of this invention as defined by the following claims.

Claims

THE EMBODIMENTS OF THE INVENTION IN WHICH AN EXCLUSIVE
PROPERTY OR PRIVILEGE IS CLAIMED ARE DEFINED AS FOLLOWS:

1. A multi-ply paper sheet having first and second sides and an embossed pattern thereon, said embossed pattern comprising a background arrangement of alternately protruding and depressed deflected zones spaced apart by a substantially undeflected neutral plane, said deflected zones being generally elongate in shape having major and minor axis dimensions wherein the major axis is substantially aligned in the cross-machine direction, wherein the depressed and protruding deflected zones of said first side correspond to the protruding and depressed deflected zones, respectively, of said second side.

2. The paper sheet of claim 1 wherein the background deflected zones are arranged in successive curvilinear rows.

3. The paper sheet of claim 1 wherein the spacing of the deflected areas is at least as great as the minor axis dimension.

4. The paper sheet of claim 1 wherein the deflected zones are oval in shape.

5. The paper sheet of claim 4 wherein the dimension of the major axis is about .075 inch, the dimension of the minor axis is about .035 inch, and the spacing between adjacent oval deflected areas is about .035 inch.

6. A two-ply paper towel having first and second sides and having an embossed background pattern thereon, said 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 said second side.

7. The paper towel of claim 6 wherein the embossed pattern further comprises an intermittent neutral plane pattern contain-ing 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.

8. The paper towel of claim 7 wherein the intermittent neutral plane pattern defines a shape suggestive of a shamrock.

9. An embossed paper sheet of the creped paper type for paper towels and tissue. said sheet having embossments in a pattern with an evenly spaced background. said embossments having a major axis and a minor axis. the major axis of substantially all of the embossments being substantially aligned in the cross-machine direction.

10. The paper sheet of claim 9 wherein the embossments are oval, rectangular or diamond-shaped.

11. The paper sheet of claim 9 wherein the major axis is parallel to the cross-machine direction.