Puffed cellulosic product and method of manufacture

March 13, 1962 κ. j. harwood 3,025,199

PUFFED CELLULOSIC PRODUCT AND METHOD OF MANUFACTURE

Original Filed June 13, 1956 2 Sheets-Sheet 1

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March 13, 1962 κ. j. harwood 3,025,199

PUFFED CELLULOSIC PRODUCT AND METHOD OF MANUFACTURE

Original Filed June 13, 1956 2 Sheets-Sheet 2

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United States Patent Office

3,025,199

Patented Mar. 13, 1962 the opposite sides of the reinforcing web 1 by the adhesive coating or adhesive fibers such as themoplastic carried by either or both of said sets of threads. Intimate engagement of the reinforcing means and the fiber layers may be 5 effected by calendering the web, and if thermoplastic adhesive or fiber is employed, the calender may be heated sufficiently to reactivate the thermoplastic material.

For certain purposes which will presently appear, it is generally preferred that both sets of threads 2 and 3 have 10 adhesive material thereon or therein to effect interbonding of said thread sets and to effect very secure bonding of said non-woven layers of fiber to the opposite faces of the reinforcing material. However, for many purposes adhesive along the lengths of one of said sets of threads IS is sufficient and coatings of adhesives, whether on one or on both sets of threads,' may be continuous or discontinuous. If it is to be discontinuous it is preferable that the interruptions in the adhesive coatings be of relatively short length and irregularly or regularly so spaced as to 20 maintain to a minimum, the number of thread intersections which fail to become bonded because of the absence of adhesive at said interruptions. The use of such discontinuous adhesive coatings is advantageous in that the spaced adhesive-free short portions of the lengths of the 25 threads will exhibit the full normal softness and flexibility of the threads unaffected by an adhesive coating. Permanently flexible adhesives which tend to remain surfaced on the threads rather than to penetrate the same are generally preferred for the purpose of this invention, but 30 other kinds of adhesive may be used if suitable to the end purpose of the fabric.

In the material represented in FIGS. 1 and 3, the non-woven layers 4 and 5 of fiber each comprise two plies of crepe tissue paper having a weight within the 35 range of about 20 grams to 40 grams per square yard and having a crepe ratio of about 1.25 to 1. These layers of crepe tissue paper were adhesively bonded to the opposite sides of the carrier or base web 1 by means of polyvinyl acetate adhesive applied only to the machine direc40 tion threads at the rate of about one pound per 20,000 feet of thread. The base web consisted of low twist multifilament cross laid threads, the longitudinal threads 2 comprising 30 filaments of 75 denier and the cross threads 3 comprising 40 filaments of 100 denier. The fabric 45 was calendered to insure good adhesive bonding of the non-woven layers of fiber to the carrier web, and its thickness after calendering was about .052 inch.

The web represented in FIGS. 1 and 3 is subjected to a treatment whereby the fibers appear to be more or 50 less extended intermediate points of attachment thereof to spaced portions of pairs of said reinforcing threads and the extended fibers caused to buckle out of the plane of the reinforcing threads which causes the surfaces of the web to have a pronounced puffed effect as indicated ⁵³ at 6 in FIGS. 2 and 4 whereby the thickness or bulk of the web is substantially increased. This puffed effect is accompanied by some separation of the fibers in said layers 4 and 5 from each other, whereby the porosity of the web is also substantially increased. In the material repre³³ sented in FIGS. 2 and 4 the thickness was increased about twofold or somewhat more as compared with the thickness of the untreated starting sheet as represented in FIGS. 1 and 3.

Working of the material to cause the fibers to buckle ³³ and impart to the fabric the puffed surface and increased porosity indicated was effected by the action of a swing tenter as represented in FIG. 15. A swing tenter is a well known mechanism used in the textile industry for ₇θ stretching fabrics to restore them to a predetermined normal width and to eliminate wrinkles after the fabric has been bleached or dyed or subjected to other wet treat3,025,199

PUFFED CELLULOSIC PRODUCT AND METHOD OF MANUFACTURE

Kenneth J. Harwood, Neenah, Wis., assignor to Kimberly-Clark Corporation, a corporation of Delaware Continuation of application Ser. No. 591,165, June 13, 1956. This application July 31, 1959, Ser. No. 830,783

Claims. (Cl. 154—46)

This invention relates to a cellulosic product and more particularly to an improvement in puffed webs which may comprise mainly cellulose fibers, although other materials may be used.

The puffed web herein contemplated may be made to exhibit a number of characteristics in varying degrees to adapt the web to a wide variety of uses for which textile fabric is commonly used, and others. For example, the web may be made suitable for use as toweling and other wiping material, expendable garment material, packing material for packaging and similar purposes, acoustical sheeting, decorative sheeting comprising drapes, curtains and other forms, and for filtering and other purposes which will appear from time to time.

The main object of the present invention is to provide an improved puffed web product, having th© utility indicated, and a method by which the puffed web may be produced by commercially practicable and economical means.

Other objects and advantages of the invention will be understood by reference to the following specification and accompanying drawings (2 sheets).

In the drawings:

FIG. 1 is an elevation of a piece of material which embodies constructional details which adapt the material to the production of a web according to the present invention;

FIG. 2 is an elevation of a piece of material according to the present invention.

FIGS. 3 and 4 are cross sections on the line 3—3 and 4—4 respectively of FIGS. 1 and 2 and illustrating the “before” and “after” treatment conditions of the material;

FIGS. 5 and 6 respectively represent modifications of the improved fabric;

FIGS. 7, 8, 9 and 10 are schematic representations of the action which occurs when the material shown in FIG. 1 is treated according to the treatment method of the present invention to convert the material into the fabric of FIGS. 2 and 4;

FIGS. 11, 12, 13 and 14 are schematic representations of another method of producing the improved fabric;

FIG. 15 is a schematic representation of apparatus for practicing the method which is illustrated in FIGS. 7 to 10 inclusive.

The material shown in FIG. 1 embodies a base or reinforcing web 1 which comprises a plurality of spaced longitudinal or machine direction textile threads 2 and a plurality of transversely extending longitudinally spaced textile threads 3. These threads 2 and 3 may be of conventional hard twist textile threads or they may be of low twist construction, and they may be of synthetic monofilament or multiple-filament construction. For many purposes these threads are advantageously of continuous multiple-filament low twist construction. As indicated in FIG. 1, the cross threads 3 are not interwoven with the machine direction threads 2 but are cross laid thereon and the threads 2 and 3 are adhesively bonded together at their intersections by means of adhesive coatings carried by either or both sets of threads, or by thermoplastic or other adhesive fibers embodied in either or both of said sets of threads.

Non-woven layers 4 and 5 of fibers are attached to

3,026,199 ments which cause them to wrinkle and shrink. A swing tenter comprises, among other things, opposite side rail mechanism 7 and 8 by which the side edges of the fabric are gripped. The gripping side rails 7 and 8 are suitably supported for longitudinal and transverse movement and they are interconnected by a plurality of links or arms one of which is indicated at 9. The arms 9 are pivotally mounted intermediate their ends as indicated at 10 and pivotally connected as indicated at 11 and 12 to the respective rails. By suitable mechanism the arms 9 are rocked about their pivots 10 so as to cause the rails 7 and 8 to reciprocate simultaneously in opposite directions while remaining constantly in parallel relationship. The links 9 may be rocked through arcs of various extent depending upon the kind and requirements of fabric being treated and the results desired.

For the purpose of this invention the non-woven fiber web or sheet such as represented in FIGS. 1 and 3 is subjected to the simultaneous opposed reciprocation of the tenter gripping rails 7 and 8. Such working of the web causes the aforesaid puffing of the web as represented in FIGS. 2 and 4. This effect is explained by the action represented in FIGS. 7 to 10 inclusive.

In FIG. 7, the reinforcement 1 is represented by the network forming lines 2 and 3 which correspond respectively to the machine and cross direction threads 2 and 3 in the reinforcement netting 1. In a crepe tissue paper web there is, of course, a normal machine direction fiber alignment of a portion of fibers in the webs but there is also a very substantial percentage of fibers which are haphazardly arranged in the web. A machine direction fiber is represented at 14 in FIG. 7 and a cross direction fiber at 15. Haphazardly arranged, angularly disposed fibers are represented at 16 and 17, these being fibers disposed in opposite angular positions and another angularly disposed fiber is indicated at 18. The fiber 18 represents a simple continuous fiber which is in its natural crinkled or curly state and it also represents a crimped synthetic fiber. The fibers represented at 16 and 17 are articulated and each comprise sections a and b which have overlapping portions indicated at c, these overlapping portions being joined to each other as an incident to the intertwining of such fiber sections or their cohesive interattachment, or by adhesive which may be applied to the nonwoven fiber web to bond the fibers into a self-sustaining web.

When the spaced machine direction threads 2 are moved longitudinally relative to each other by operation of the swing tentering mechanism to cause the cross threads 3 to assume the angles indicated in FIG. 8, the shifting of the threads 2 relative to each other serves to elongate the distance between the points 19 and 20 of attachment of the fiber 17 to the spaced pair of adhesive bearing threads 2 so that the two section fiber 17 is extended incident, at least in part, to slippage between the joined portions of the fiber sections a and b so as to reduce the extent of overlap as indicated in FIG. 8. The connection between the fiber sections intermediate their points of attachment to threads of the base web should be weaker than the bonds between the fibers and the base web so that the interconnected or overlapping portions of the fibers may be moved relative to each other incident to the working action without breaking the fiberto-base web bonds and without breaking the fibers.

When the base web 1 is restored to normal square condition as represented in FIG. 9, the distance between the points 19 and 20 is considerably shortened as compared with the distance between the said points in the distorted condition represented in FIG. 8 so that the fiber 17 will be caused to buckle or gather on itself in fairly large wave forms.

During the working steps represented in FIGS. 7, 8 and 9, the machine direction and cross direction fibers 14 and 15 are subjected to movement but they are not subjected to tensioning so that upon return of the material to nor4 mal square condition these fibers 14 and 15 are not significantly changed.

During the working steps represented in FIGS. 7, 8 and 9, the fibers 16 and 18 will have been shortened as represented in FIG. 8 and not tensioned so that when the material is restored to the square condition of FIG. 9 said fibers 16 and 18 will also be restored substantially to their initial condition between points of attachment to the spaced base web strands as indicated at 2. However, on the next and oppositely directed reciprocation of the swing tenter rails 7 and 8, as shown in FIG. 10, the two section fiber 16 attached at 21 and 22 to the reinforcing material, will be stretched in the same manner as above explained in respect of the two-section fiber 17 so that, upon the following return of the base web to its normal square condition, said fiber 16 will also be caused to buckle like the fiber 17 to thereby impart the puffed surface characteristic to the web or sheet.

The fiber 18 attached at 23 and 24 to spaced portions of a pair of the base web strands 2 will be tensioned as indicated in FIG. 10 so as to remove some of its curliness or crinkle so that such fiber will be somewhat elongated and accordingly caused to buckle upon restoration of the base web to square condition, even though said fiber embodies no connected portions which may slide relative to each other to elongate the fiber. Such elongation, i.e., by removal of some of the normal curl of crinkle, also is probably effected in the two-section fibers together with the elongation effected by shortening the length of the inter-connected overlapping portions of the fiber sections.

In FIGS. 7 to 10 inclusive the explanation is based on a square fabric, that is to say a fabric in which the base web network has machine and cross section threads parallel and normal respectively to the length of the fabric. This is not a necessity as will appear from a consideration of FIGS. 11 to 14 inclusive wherein there is schematically represented the effect of working a fabric embodying a reinforcing web which has its strands arranged to form a diamond pattern in the fabric. Assuming that the machine direction and cross direction are identified by the arrowed lines respectively identified MD (machine direction) and CD (cross direction) in FIGS. 11 to 14 inclusive, the reinforcing network may be in the form of a diamond pattern embodying one set of parallel diagonally extending strands 26 and another set of diagonally extending parallel strands 27, the latter extending crosswise of the strands 26.

If a non-woven web of fibers reinforced by a diamond patterned network as above described is temporarily stretched crosswise, cross direction fibers such as indicated at 28 and 29 will be elongated as is evident from an inspection of FIG. 12 and will buckle on themselves when the fabric restored to its normal cross direction width as represented in FIG. 13. Similarly, if the fabric is stretched in its lengthwise direction as represented in FIG. 14, more or less longitudinal fibers, such as one indicated at 30, will be elongated and caused to buckle on themselves when the length of the fabric is restored to normal length. This diamond pattern reinforcing network may be stretched crosswise by suitable roll means or by appropriately guided conveyor chains equipped with means for gripping the side margins of the web. Lengthwise stretching may be effected by cooperative low and high speed roll pairs. The final stretch should be such that the web will be restored to its initial dimensions incident to the inherent capacity of the diamond pattern network, when stretched in one direction, to neck down in the transverse direction. This diamond pattern is especially useful when the sheet includes resilient threads in the reinforcing network or otherwise, or is otherwise made resilient, so that it tends to restore itself to a predetermined normal condition from which it is stretched either or both crosswise and lengthwise to produce the described fiber buckling.

3,025,199

The fiber extending or elongating action of the described tentering and stretching operations may often be facilitated by moistening the fabric before the fabric is worked. Moistening of the fabric tends to soften the fibers to permit removal of the curl or crinkle therein, and to weaken the bond between the overlapping fiber portions in the areas represented at c so that the fiber extending action is more easily accomplished. Water is generally a satisfactory agent for this purpose. In cases where adhesive is employed to bond the fibers together into a self-sustaining web, the sheet may be moistened with any solvent or other agent which softens the adhesive so as to weaken the bond between the fibers without adversely affecting the bonds between the fibers and the strands of the base webs. The adhesive applied to the threads of the carrier web should therefore be one which will resist dissolution or softening by whatever moistening agent is employed for the aforesaid purpose.

The puffing of non-woven sheeting in the manner described is not limited in its application to webs in which the face sheets are made of crepe tissue paper although it is especially useful in that connection in which it appears to produce the best results. The described puffing method may be applied to a web of the construction represented in FIG. 5 wherein layers 35 and 36 of cotton or other fiber are attached to a suitable woven carrier or reinforcing webs 37. The fiber layers 35 and 36 may be carded, garnetted, air laid or otherwise formed and the fibers may extend predominantly in the machine direction (as in a carded web) while nevertheless having a sufficient quantity of fibers which extend angularly to cause fiber buckling and web puffing when the web is suitably worked or treated. The extent or degree of the puffing effect is of course dependent on the amount of fiber which is so anchored and so arranged that the fibers will be extended by the working operation employed.

The fibers in the webs 35 and 36 may be all cotton or any other kind of fiber or blends of two or more kinds. Natural and synthetic fibers to form non-woven webs such as the carded webs 35 and 36 in FIG. 5 are normally considerably longer than the fibers which are present in crepe tissue webs and this permits the strands of the carrying web to be spaced somewhat farther apart. To obtain the full benefit of fiber elongation by working action, the strands of the network 37 should be spaced apart a distance which is somewhat in excess of the average length of the fibers so as to insure the presence of many articulated fibers having connections which may yield for fiber elongation purposes as explained above in connection with the crepe tissue faced fabric of FIGS. 1 to 4 inclusive.

FIGURE 6 represents sheeting embodying non-woven facing plies 41 and 42 of any suitable character carried by a base web 43 which comprises threads or other strands extending diagonally of the length of the sheeting so as to provide a diamond form carrier web. This web may be worked in the manner explained above in connection with FIGS. 11 to 14 inclusive.

Although in the foregoing, reference has been made to non-woven facing layers of fiber on opposite sides of a carrying web, it should be understood that a non-woven facing layer embodying one or more plies may be applied to only one side of the base web or reinforcing means and the puffed effect obtained in such a single layer. The puffed effect in the case of a single fiber layer will be noticeable to some extent on the base web or grid side of the fabric but more predominantly on the faced side.

For some purposes, the sheeting may be made with a puffed non-woven facing of fibers on one side of the reinforcing element and a facing sheet of any other selected character on the other side. For example, a crepe tissue paper web may be carried by one side of a supporting grid or other reinforcing means and a highly carded web of rayon or other fibers or a moisture resistant or other facing may be carried by the other side of the reinforcement. A highly carded fiber web, having a negligible proportion of its fibers out of alignment with the machine direction of the web, will not be significantly affected by a swing tentering operation employed to effect puffing of the crepe tissue facing and will maintain its normal appearance for its side of the sheet.

In a product which is to be swing tentered, or similarly worked, the best fabric puffing results are obtained when the fibers in the non-woven facing are haphazardly arranged and crepe tissue wadding having a high crepe ratio such as 2.4 to 1 gives excellent results.

The spacing of the reinforcing strands does not appear to be very critical. However, for products having facing sheets of crepe paper which embodies a major portion of fibers of short length such as one-sixteenth of an inch and less, the reinforcing strands or elements ordinarily should be at a frequency of about 15 or less strands per inch in any direction. Products exhibiting excellent bulk and drape have been made with 6 machine direction threads per inch and 5.2 cross direction threads per inch with facings of crepe tissue paper. The base web is substantially inextensible both lengthwise and crosswise and this imparts dimensional stability to the finished sheeting; such stability is of considerable importance in most converting processes.

The puffed web or sheet tends to resist creasing and crumbling and exhibits substantial resistance to rupture either by impact or by tension forces. The material, either before or after being worked to impart puffiness to it, may be treated with materials to impart wet strength, fire resistance, wrinkle resistance and other characteristics which are normally attainable in fiber products. The treating fluid may be applied for the dual purpose of imparting a selected characteristic to the material and also for weakening the fiber-to-fiber bonds to enable a web working or other fiber elongating operation to effect elongation of the fibers.

In a sheet of the material in which all of the threads or strands of the carrying web are adhesively coated, the fiber buckling is confined in areas bounded by the threads and a pleasing pattern of square pillows is provided. In a web in which only the longitudinal base web strands are adhesively coated, the puffing effect may extend uninterruptedly across the cross threads from one longitudinal thread to the next. In such fabric, when made by swing tentering, the puffed pattern gives the general appearance of a diagonally extending pattern in which the presence of the cross threads is less noticeable while the machine direction threads reveal their appearance by the interruption of the diagonal waves of puffing.

In all of the described sheetings the non-woven web is adhesively bonded so as to permit movement of the fibers in the areas intermediate the bonds in the web so that, as tension is applied to the fibers, their condition is altered and they are repositioned as an incident to buckling thereof and a puffed surface, increased bulk, and increased porosity are imparted to the sheet.

Other methods of working the material to cause puffing of the non-woven facings of fiber may be employed and various modifications of the sheet structure may be made in accordance with the principles of the invention as described.

This application is a continuation of my co-pending application Serial No. 591,165, filed June 13, 1956, now abandoned.