Multi-ply Paper Towel

Abstract

A multi-ply absorbent creped cellulose wadding paper tissue material in which an elastically extensible inner web of creped tissue paper has on its major faces at least one embossed paper tissue material of greater dryer basis weight and lesser extensibility. The outer webs are bonded to the inner web (or webs) in spaced regions to provide unbonded zones between bonds. The adhesive is sufficiently water resistant to permit retention of the webs when wetted so that the inner creped web may expand and fill the unbonded zones providing good bulk in the wet product. Methods of effecting the web combinations are described.

Description

BACKGROUND OF THE INVENTION

Field of the Invention

This invention relates to absorbent creped cellulosic wadding or paper wiping products, particularly multi-ply paper towels, and to methods of producing such products.

A general object of the invention is to provide an improved paper toweling medium which, with respect to currently commercially available products, has materially greater liquid absorbency and towel bulk as well as better wet and dry dimensional stability and softness, tensile strength, stretch and quantity of fluid absorbency.

Another object of the invention resides in the provision of novel methods for the production of paper toweling.

The approved toweling material in accordance with the invention employs a multi-ply structure of creped cellulosic wadding sheet material. An inner web of absorbent creped tissue paper is characterized by having considerable extensibility in at least one planar direction of the towel. Water resistant bonds secure at least one outer web of creped tissue to the inner web in spaced regions and on each major face of the inner web. The outer webs of creped tissue are extensible but much less so than the inner web.

The provision of adhesive bonds in spaced regions provides unbonded zones of the towel structure between bonds. The less extensible outer webs of tissue paper confine the expansion or the extensibility of the inner web largely to the unbonded zones and, upon wetting in towel use, the normal release of the crepe of the inner web tends to cause the unbonded zones to be filled with an expanded inner creped web. This tends to bulk the towel in the wet state which is the converse of that which commonly occurs when towel structures are wetted. Accordingly, the bulking action gives a stability to the toweling material and assists in attaining a product of improved hand.

It is to be noted that in the toweling material the outer webs or plies of the multi-ply structure are provided with embossments to further aid bulk and to impart softness and conformability to the material. Embossing decreases the stretch of a web to some degree but is not generally detrimental. Also, the embossments of the outer webs may lie in directly opposed relation but such is not necessary to the invention. The inner more extensible web may also be embossed if desired. This inner web is a ply of much lighter basis weight than the outer plies, a factor which further is important in the attainment of towel drape and flexibility.

Adhesive employed to bond the outer webs to the inner and more extensible web should be sufficiently water resistant that the bonds will be retained for a length of time to permit the expansion of the inner web relative to the outer webs and for toweling material of the inner web to fill out in the unbonded zones against the outer webs. The pattern of adhesive application will affect the extent of bulking but is not a critical factor, it simply being desirable to have a sufficient number of bonded zones to hold the multi-ply structure together in manufacture and use. Many adhesives will serve the purposes, and polyvinyl alcohol is a typical commercial and useful material. Other suitable adhesives are polyvinyl acetate, dextrin, acrylic latexes and the like.

The inner creped tissue web should not only be extensible but, for many methods of production, should be resiliently so in order to permit its passage through conventional manufacturing equipment without significant loss of stretch. Additionally, if desired, the inner ply may be attached to the outer plies while the resilient inner ply is in a stretched condition relative to the outer plies. Upon release, the outer webs will then be bulked further in the unbonded zones by the retraction of the material, and such unbonded zones will be further receptive to the expanding material of the inner web when the towel is wetted.

In practice, I have found that it is desirable that, in the finished product, the inner ply should be stretchable to at least about two times that of the stretch of the outer plies, all elongations being measured at break.

The invention will be more fully understood by reference to the following detailed description and accompanying drawings wherein:

FIG. 1 is a schematic representation of apparatus on which multi-ply toweling of the present invention may be formed;

FIG. 2 is a fragmentary view in plane of toweling in accordance with the invention and with portions of the upper ply removed and portions of the inner ply turned back;

FIG. 2A is an exploded view illustrating the creped unembossed wadding plies useful for formation of the structure of FIG. 2;

FIG. 3 is an enlarged and edge view taken along line 3--3 of FIG. 2;

FIG. 4 is an enlarged view taken along line 4--4 of FIG. 2;

FIG. 5 is a view similar to that of FIG. 3 but illustrating the product after it has been wetted;

FIG. 6 is a view similar to that of FIG. 4 but illustrating the product after it has been wetted;

FIG. 7 is an enlarged view in section illustrating another method of combining the plies of the multi-ply toweling but generally similar to that of FIG. 1;

FIG. 8 is a view like that of FIG. 7 but involving a combining nip in which the lower of the combining rolls is a soft foam rubber;

FIG. 8A is a cross section of toweling material produced using the combining nip illustrated in FIG. 8 and showing a random adherence of the plies of the toweling material;

FIG. 9 is a view of another embodiment of toweling material produced with a combining nip as illustrated in FIG. 8 but showing a somewhat different adherence relation of the plies;

FIG. 10 is a sectional view, enlarged, of toweling material produced with another adhesive arrangement for securing the webs together; and

FIG. 11 is an apparatus arrangement illustrating another method of forming toweling material in accordance with the invention.

Referring now the drawings, the numeral 1 in FIG. 1 indicates schematically a web of creped tissue being moved in the direction of the arrow around a resilient rubber roll 2 through a nip 3 formed by the resilient roll 2 and a metal, suitably steel, male embossing roll 4. In the drawings the various webs and rolls move in the directions indicated by the associated arrows. The web 1 as it proceeds to a combining nip 5 is embossed in the nip 3 by indentation of the soft rubber roll 2 (Shore durometer A about 40) to provide upstanding embossments 11 (FIG. 2) which are supplied with adhesive by the flexographic type adhesive applicator indicated generally at 6. The applicator 6 includes applicator roll 7, intermediate roll 8 and pond roll 9 for the application of adhesive 10 to the embossments of the traveling web 1. The rolls 7, 8 and 9 are respectively rubber covered, steel and rubber covered; they are plain surfaced rolls but rolls 7, 8 could be patterned if desired. Adhesive is applied only to the web embossments 11 as the web proceeds to the nip 5. The adhesive itself is applied in very thin film form and is not visible to the unaided eye on the web. A second and similar web 12 is provided to the nip 5 over similar equipment. The numeral 13 designates a soft rubber roll (Shore durometer A about 40) which forms the nip 14 with the male embosser roll 15, adhesive 17 being supplied to the embossments 16 (FIG. 2) by the action of rolls 18, 19 and 20. The roll 21, like the roll 4, is a male embosser roll which receives thereover in the nip 5 the traveling adhesive carrying embossed web 12. Male embosser rolls 21, 4, and 15 are identically patterned and rotate in unison at the same speeds.

A third web 22 of relatively light dryer basis weight and of high stretch characteristics (as schematically illustrated generally by the relatively high crepe frequency in FIG. 1) is fed to the nip 5 between the webs 1 and 12. As illustrated in the drawings, the coaction of the rolls 4 and 21 serves to bond together the outer webs 1 and 12 with the inner web 22. It is to be noted that, while rolls 4 and 21 are suitably rotated in unison, the webs 1 and 12 will not exactly provide their embossments in opposed relation in the nip 5, and no attempt is made to control sheet 12 to so provide the embossments in opposition.

Following the combining step in nip 5, the three ply web may be subjected to a drying operation to set the adhesive and then to winding into roll form. With many adhesives the drying operation is not necessary as sufficient bonding of the webs occurs in nip 5.

As shown in FIGS. 2, 3 and 4, well bonded areas of the toweling material occur at 23, for example. These bonded areas are in well spaced regions of the material and provide unbonded zones 24 between the bonds 23 (FIGS. 3 and 4). In one specific example the toweling plies 1 and 12 having respectively the embossments 11 and 16 were of a dryer basis weight of about 11.0 pounds and had a crepe ratio of about 1:3 or an actual basis weight of 14.3 (11.times.1.3). The stretch of the individual outer webs was about 30 percent. The inner web 22 had a dryer basis weight of about 7.5 at a crepe ratio of about 2.2. Thus, this latter web had a stretch of about 120 percent. The finished product exhibited a finished basis weight of about 38 pounds per 2,880 sq. ft. and rupture of the outer plies occurred at a stretch of about 10 percent. The inner ply in the product has a much greater percent stretch of about 80 (dryer basis weight is the weight of the sheet per 2,880 sq. ft. on the Yankee dryer before creping).

The product illustrated in FIGS. 3 and 4, when wetted, had a structure such as is illustrated in FIGS. 5 and 6. As may be clearly noted from FIG. 5, the highly creped inner ply 22 expanded very considerably in the zones 24 abutting against both plies 1 and 12 and tended to retain these plies in bulked or distended condition. This is clearly shown in FIG. 5 at 25, and somewhat less so in FIG. 6 wherein the view is transverse to that of the toweling material and the crepe structure of the webs including web 22.

In FIG. 7 the arrangement is very similar to that of FIG. 1 except that adhesive has been applied only to some embossments; this is readily accomplished by providing roll 7 or 8 or 18 or 19 as patterned rolls (peg rolls). Thus, there is a greater degree of random ply attachment in this mode of processing.

Another embodiment of the toweling structure is illustrated in FIG. 8A. In this instance the product results from the use of a patterned adhesive application and a combining nip formed by the male metal embossing roll 4 and a soft foam rubber covered roll indicated by the numeral 28. The webs 1, 12 and 22 are fed to this nip as described in connection with FIGS. 1 and 7 but in this instance the foam rubber roll 28 yields and there is an increased attachment of the plies 1 and 12 to the intermediate ply 22 over that shown in connection with the FIG. 7 modification. Accordingly, to some extent the unbonded zones indicated at 29 (FIG. 8A) are somewhat nonuniform and frequently larger than the unbonded zones of the structure of FIG. 2. Thus, it will be noted that, in FIG. 8A plies 22 and 12 are attached at 30 but are not attached to web 1 in this area. More specifically, the bonding in connection with the structure of FIG. 8A is less uniform, that is, more random, than in the previously described toweling material of FIG. 2.

The structure of FIG. 9 is based upon an adhesive application to the webs 1 and 12 which is more frequent with respect to both webs, the adhesive bonding areas 33 are more close together and the frequency of the uniting of all three plies is greater though commonly only the center ply and one outer ply are united at a particular area of the sheet.

The embodiment of the toweling material illustrated in FIG. 10 is suitably produced on an equipment arrangement illustrated in FIG. 11. The combining nip and the presentation of the webs 1 and 12 to the combining nip is similar to that illustrated in FIG. 1 except that no adhesive is applied directly to the webs 1 and 12. Rather, an intaglio roll 39 rotating in the direction indicated by the arrow in a pan of adhesive 36 and having a suitable doctor blade 37 applies adhesive to the under side of the traveling web 22. A similar applicator roll 39 applies adhesive from a pond 40 to the upper side of the traveling web 22. The adhesive is simply wiped on to the web 22 from the intaglio rolls, the control of the adhesive being through the medium of the doctor blades 37 and 41, the roll speed relative to the web and the intaglio pattern. The attachment of the web 22 to the webs 1 and 12, as illustrated in FIG. 10, is also somewhat random, the webs being securely attached together as indicated at 42 or occasionally only the web 12 attaching to the web 22 as indicated at 43. Also, in some instances there will be an attachment only to the web 1 by the web 22 as is indicated at 44.

In each of the embodiments described, the center ply of the toweling material has a distinctively greater elongation characteristic than does the outer plies. Conveniently, the inner ply may have a dryer basis weight of about one-half to three-quarters that of the outer web or between about 5.0 and 9.0 pounds; an extension at break of between about 50 and 150 percent with a preferred range of 80 to 120 percent. The outer plies may suitably have dryer basis weights of between about 9 and 15 pounds, an extension at break of between about 20 and 40 percent. It is not necessary that the outer plies have the same basis weight although this is generally preferable in toweling material for home use as both sides of the toweling material then tend to have the same characteristics.

The furnish for the webs in the above specifically described multi-ply toweling structures was of wood pulp as follows:

40 percent by weight of bleached softwood kraft

50 percent by weight of bleached softwood sulfite

10 percent by weight of bleached hardwood kraft

It is to be noted, however, that the furnish for the webs is not critical, the creped cellulosic wadding furnishes commonly employed in toweling and wipes generally being suitable, and wet strength agent to the extent of between about 0.25 to 0.50 percent by weight of the fiber being customarily incorporated.

Examination of the characteristics of the three ply towel illustrated in FIGS. 2 to 6 inclusive show that the toweling has:

1. a compressive modulus of about 899;

2. a Handle-O-Meter MD and CD respectively of about 52.3 and 75.4;

3. a water absorption capacity of about 5.7 grams per 4.times. 4 width, which is more than double (2.01 grams per 4.times.4) that of two ply towels of similar furnish;

4. Bulk approximately 30 percent greater than that of a two ply sheet of similar material, the bulk being largely determined by the nature of the embossing pattern and the receptivity of the sheet to embossing.

Note: Compressive Modulus is a measure of resistance to compression and a low compressive modulus is a very general indication of softness.

Handle-O-Meter is generally a measure of stiffness of a sheet, higher numerical HOM values indicating greater stiffness.

It is to be noted that the water absorbent capacity is greater than would be expected from a simple consideration of the additional amount of material in the three ply structure. Particularly also is the bulk greater in the wet state, a factor which apparently contributes to the greater absorbent capacity.

While the foregoing description has emphasized a three-ply toweling material, it is considered that the interior may be formed of two or more similar high stretch plies preferably united together for stretch as a unit. In general, however, an increased dryer basis weight of the interior ply structure will occasion greater stiffness and less desirable drape characteristics.

As many apparently widely different embodiments of this invention may be made without departing from the spirit and scope thereof, it is to be understood that I do not limit myself to the specific embodiments thereof except as defined in the appended claims.

Claims

I claim:

1. A multi-ply cellulosic wadding tissue paper wiping material having a capacity for the retention of liquids and exhibiting good bulk characteristics in the wet and dry state, said material comprising an inner web of absorbent creped tissue paper which is extensible in at least one planar direction of the product and at least one outer web of absorbent creped tissue paper on each major face of the said inner web, and each outer web having embossments, adhesive bonds securing the outer webs to the inner web at embossments in spaced regions to provide unbonded zones of the wiping material between bonds, said outer webs of creped tissue paper being somewhat inextensible relative to the inner web in the said one planar direction so that the outer webs are capable of restricting extension of the inner web to zones between bonds when the material is wetted.

2. A multi-ply material according to claim 1 in which the extensibility of the inner web is at least about two times that of an outer web.

3. A multi-ply material according to claim 1 in which the inner web has a dryer basis weight which is approximately one-half to three-quarters of the basis weight of an outer web.

4. A multi-ply material according to claim 1 in which the outer webs have a dryer basis weight of between about 9 and 15 pounds and the inner web has a dryer basis weight of between about 5 and 9 pounds per 2,880 sq. ft. and the elongation of said inner web at break is at least about two times that of an outer web.