US3017304A - Absorbent fibrous structure and method of production - Google Patents

Description

Jan. 16, 1962 A. A. BURGENI ABSORBENT FIBROUS STRUCTURE AND METHOD OF PRODUCTION Filed May 24, 1956 5 Sheets-Sheet 1 402450 A. 50.4 am

ATTORNEY Jan. 16, 1962 A. A. BURGENI 3,017,304

ABSORBENT FIBROUS STRUCTURE AND METHOD OF PRODUCTION 3 Sheets-Sheet 2 Filed May 24, 1956 TIE-.17-g4 INVENTOR 14;?50 ,4 flufqs/w dZ'mTM,

ATTORNEYS Jan. 16, 1962 A. A. BURGENI 3,017,304

ABSORBENT FIBROUS STRUCTURE AND METHOD OF PRODUCTION Filed May 24, 1956 3 Sheets-Sheet 5 ATTORNEY 3,017,304 ABSORBENT FitBROU'i STRUCTURE AND METHOD OF PRODIETHON Alfred A. Burgeni, Short Hills, N.J., assignor to Persona! Products Corporation, a corporation of New Jersey Fitted May 24, 1956, Ser. No. 587,015 16 Claims. (Cl. 154-54) This invention relates to absorbent fibrous bodies and to methods of making them and, more particularly, is concerned with absorbent fibrous bodies which are especially suited for use as absorbent components in sanitary napkins, surgical dressings, compresses, disposable diapers, hospital underpads and other products designed to absorb body fluids.

Products designed to absorb body fluids generally contain as a principal component thereof an absorbent pad or core to absorb the fluids. These pads or cores are normally made of layers of loosely compacted, absorbent fibers, such as carded cotton webs, air-laid cellulosic fibrous Webs, comminuted wood pulp bats, or like materials which are highly absorbent, fluffy and porous. Unfortunately, these loosely compacted, fibrous absorbent bodies possess numerous disadvantages, notably low cohesive strength, poor shape and volume stability, W forces of capillary attraction, low fluid retentivity and low absorptive capacities under conditions of use.

For eXample, comrninuted wood pulp bats which are particularly suitable as absorbent components because of their highly absorbent properties, low cost and commercial availability, are very Weak structurally and possess low cohesive stability, whereby they tend to fall apart too readily under stress. With such a component, therefore, it has been common practice to provide strengthening or reinforcing layers of gauze, paper or similar materials. This, of course, increases the cost of the product and greatly reduces the economic desirability of using wood pulp bats as the basic absorbent component.

Additionally, these comminuted wood pulp bats, as well as cotton fibrous webs, do not possess shape and volume stability to any marked degree and have quickly become deformed and distorted upon the application of slight forces or stresses. As a result, plies of creped tissue paper, absorbent paper and like supporting materials have had to be incorporated therein to give body and firmness to the article. Such additional plies of materials had increased the cost of the final product and are naturally not desirable economically.

Furthermore, the fluid retentivity of such highly porous, fibrous absorbent bodies is not sufi iciently great and, consequently, fluids which should be retained therein have been squeezed out relatively easily by the application of pressure arising from normal usage of the article. To avoid this undesirable occurrence, multiple plies of highly absorbent paper have been used in laminar combination with the highly porous, fibrous absorbent bodies to increase the fluid retentivity of the article.

Moreover, these fluffy, porous, absorbent fibrous components possess low capillary forces because of their loosely compacted structure and, when a fluid is deposited on its surface, saturation conditions are reached very quickly at the site of immediate application. At the same time, however, the adjacent portions remain relatively unsaturated and in some instances dry due to the loW capillary forces of the fibrous body and consequently a highly localized fluid condition is obtained. Efforts to avoid such local over-concentrations have led to the use of special fluid-directing and spreading elements such as multiple layers of paper or combinations of paper with fiber Webs formed With longitudinally extending embossed lines or grooves along which the fluids are directed and spread in that particular layer. Such devices are effec- 3,0173% Patented Jan. 16, 19%2 tive only to a minor degree. This is due to the fact that the spread of fluid obtained in the spreading device is not effectively transferred to adjacent layers in which the major portion of the absorbed fluid is to be stored. This is particularly true When such adjacent layers consist of loosely organized fiber Webs such as bats of disintegrated wood pulp or carded cotton. In such instances, the spreading of fluids from layer to layer is deterred by the weak capillary forces in the Webs adjacent to the spreading device, and this situation is still further aggravated by gaps, voids and air spaces between layers which prevent the diffusion of the fluid and, as a consequence, local oversaturation has occurred in the main storage elements in spite of the presence of such spreading devices.

It is therefore seen that, although absorbent fibrous bodies have been manufactured in the past and have met with some commercial success, there still remains considerable field for improvement toward a superior product.

It is an object of the present invention to provide an improved absorbent fibrous body Which possesses relatively high cohesive stability, good shape and volume stability, high forces of capillary attraction, good fluid retentivity and high absorptive capacity under conditions of use.

It is another object of this invention to provide improved absorbent fibrous bodies especially suited for use as absorbent components in sanitary napkins, surgical dressings, compresses, disposable diapers, hospital underpads and other products designed to absorb body fluids.

It is still another object of the present invention to provide absorbent fibrous bodies possessing a highly porous, fluffy surface through which the fluids will drain relatively quickly to be received and retained in a pad or core within the absorbent fibrous body whereby the surfaces thereof will remain relatively dry.

Further objects of the presen invention are to increase the fluid storage capacity of the absorbent fibrous body; to prevent the spreading of the fluids to the sides and edges thereof; to prevent the fluids from draining through to the side opposite that of deposition of the fluid (strikethrough); to minimize lateral spreading of the fluid on the deposition side of the absorbent fibrous body; and, in general, to control and direct the flow of fluids into and within the abs rbent fibrous body in the most desirable and eflicient manner.

These objecs and others which will become clear from the following description of the invention are obained by treating an absorbent fibrous body or a plurality of the same in such a Way as to form a relatively dense. compacted, more or less ccherent skin or layer integrally on or within the absorbent fibrous body, which skin or layer increases the cohesive s rength of the absorbent fibrous body, enhances its sh pe and volume stabi ity. increases its fluid retentivity and augments its capillary forces.

More specifically these objects are attained by applying controlled amounts of moisture to the surface or surfaces of a loosely compacted, fibrous absorbent body having relatively low cohesive strength, relatively poor shape and volume stability, relatively low fluid retentivity and relatively low capillary forces and applying pressure thereto within con rolled limits whereby there is formed, in situ, a paper-like, densified, highly compacted cellulosic fibrous layer integral with the loosely compacted, fibrous absorbent body and possessing relatively high cohesive strength, relatively good shape and volume stability, relatively high fluid retentivity and relatively high capillary forces.

In the accompan ing drawings and t e following specification, there are illustrated and described preferred designs of absorbent fibrous bodies but it is to be understood that the invention is not to be construed as limited thereto except as defined by the spirit of the invention and determined by the scope of the appended claims. Referring to the drawings:

PEG. 1 is an isometric view of a substantially homogeneous, loosely-compacted, absorbent fibrous body;

FIG. 2 is a cross-section of an improved absorbent fibrous structure of the present invention;

FIG. 3 is a cross-section of another improved absorbent fibrous structure of the present invention;

FIGS. 4 through are cross-sections of other im proved absorbent fibrous structures of the present invention;

FIG. 11 is a cross-section of an improved absorbent fibrous structure such as illustrated in FIG. 2 wherein the relatively dense surface skin has been formed in a series of lengthwise grooves;

FIG.- 12 is a bottom plan view of the absorbent improved fibrous structure of FIG. 11 to illustrate the spacing and positioning of the lengthwise grooves;

FIG. 13 is a plan view of another improved absorbent fibrous structure to illustrate the use of crosswise grooves;

FIG. 14 is a plan view of another improved absorbent fibrous structure to illustrate the use of crosswise and lengthwise grooves; I

P16. 15 is a cross-section of a sanitary napkin containing an improved absorbent fibrous structure of the present invention;

FIG. 16 is a side elevational view, partly schematic, of apparatus which may be employed in making the improved absorbent fibrous structures of the present invention;

FIG; 17 is an elevation of one form of an embossing roller employed in making the improved absorbent fibrous structures of FIGS. 11 and 12;

FIG. 18 is an elevation of another form of a compressing roller employed in making the improved absorbent fibrous structures of FIGS. 2 through 10;

FIG. 19 is an end view of a gear-like embossing roller employed in making the improved absorbent fibrous structure of FIG. 13;

FIG. 20 is a cross-section of another embodiment of the present invention; and

PEG. 21 is a cross-section of still another embodiment of the present invention.

The absorbent fibrous bodies of this invention contain fibers, such as comminuted wood pulp fibers, cotton linters, or the like, which, in the presence of moisture and pressure, are capable of forming a relatively dense, more or less coherent, relatively stable structure formed as a result of interfiber bonds between the moistened and compressed fibers similar to the bonds between fibers in paper. Cellulosic fibers, such as wood pulp fibers and cotton linters, are preferred in making the fibrous bodies of this invention because they readily form such interfiber bonds, when moistened and compressed. Such fibers are additionally commercially desirable as they are inexpensive, readily available and highly absorbent. Other fibers capable of developing interfiber bonds, similar to the bonds between fibers in paper in the presence of mois ture and pressure may also be used. In addition, blends of natural or synthetic fibers, such as silk, wool, linen, nylon and cellulose acetate fibers, may be used in combination with the fibers capable of forming interfiber bonds in the presence of moisture and pressure.

The fibrous structures of the present invention may be formed by applying controlled slight amounts of water as a fine spray or mist to the surface of a fibrous web or bat and then compressing the bat to form a surface skin on the moistened surface, or placing a second similar web against or on top of the moistened surface of the first web and compressing the superposed webs to form a compacted coherent integral layer of fibers at the adjacent surfaces of the superposed webs.

In FIG. 1, there is shown generally an absorbentfibrous body 10 comprising a substantially homogeneous, looselycompacted, absorbentfibrous body 11, as orginally obtained by disintegrating a wood pulp board and air-laying the resulting fibers as a bat. Such a body possesses numerous disadvantages notably relatively low cohesive strength, relatively poor shape and volume stability, relatively low fluid retcntivity and relatively low capillarity and is not ideal or completely satisfactory for use as an absorbent component in many absorbent products. The ability of such bodies to store and to retain fluids under conditions of use is low inasmuch as fluids deposited on one surface thereof tend to drain relatively quickly into its body and strike through to the opposite surface. The body can be torn apart very easily and can be distorted and deformed readily by the application of even low stresses. Due to its dispersed and loosely compacted nature, the capillary forces are low and local oversaturation and local dryness is obtained in the same fibrous body.

FIG. 2 is a cross-section of an improved absorbent fibrous structure 12 comprising a loosely compacted, absorbentfibrous body 13 and a relatively dense, compacted,coherent surface skin 14 integrally formed on the lower surface thereof. Such a structure is formed by spraying or otherwise depositing a controlled amount of moisture on the surface of absorbentfibrous body 10 and then passing the same through compression means to be described more fully hereinafter.

Such a fibrous structure resists tearing apart considerably more than the body of FIG. 1 and is distorted and deformed only by the application of greater stresses. The dense, relativelycompact skin 14 has high capillary forces which facilitate the dispersion and spreading of fluid to avoid local oversaturation and dry areas.

It is believed that the formation of the densified skin is due to the formation of bonds between contacting moistened fibers, which bonds are similar to the bonds between the fibers in paper. By the proper selection of the amount of moisture applied to the fibers and by the proper selection of the degree of compression imposed, the properties of the densified skin may be varied, as desired or required. The thickness, density, strength and other characteristics of the densified skin also depend upon the uniformity by which the moisture is applied,v the depth to which it penetrates and the degree to which the fibers are compressed. For example, by finely spraying about 0.0015 cc. of water per square centimeter of web surface and then exposing the web to a pressure of about 40 pounds per square inch, a densified, coherent, papery skin is obtained on the surface of the web which had been moistened. Such a structure is illustrated in FIG. 2.

The amount of moisture used may vary from about 00005 to about 0.03 cc. of Water per square centimeter of web surface depending upon the thickness of the web, the thickness of the paper-like, densified skin desired, with the lesser amounts of moisture being used for thinner webs and yielding extremely thin papery skin and the greater amounts of moisture being used for thicker webs and yielding skins of a greater thickness.

Within the more commercial aspects of the present invention, however, it has been found that a range of from about 0.001 to about 0.004 cc. of water per square centimeter of web surface has been found economically desirable. Such values have been found particularly suitable for bats having a thickness of from about /2 to about 1 centimeter.

The amounts of pressure to be applied to the moistened surfaces may be varied from about 5 to about or more pounds per square inch, with the commercially preferable range extending from about 10 to about 50 pounds per square inch.

FIG. 3 illustrates an absorbentfibrous structure 15 having an absorbentfibrous body 16 and relatively dense, compacted, coherent skins 17, 18 integrally formed on each of the lower and upper surfaces thereof. Such a an absorbent fibrous body 56 (see FIG. 12) containing a relatively dense, compacted embossedskin 69. Awaterrepellent tissue 70 is provided in order to act as a barrier against the strike-through of fluid. Another absorbentfibrous body 62 having an embossed skin such as shown in FIG. 14 contacts the under surface of water-repellent tissue 70. Apaper envelope 71 is provided to enclose the absorbent components and the water-repellent tissue 70. Atextile cover 72 provides an external wrapping for the complete article and has the customary ends (not shown) extending beyond the absorbent bodies to provide attachment for use. It is to be appreciated that this particular embodiment is used for illustrative purposes and that either absorbent pad may be replaced by any one of the other embodiments set forth in other figures of the drawings. It is also to be observed that, although a sanitary napkin has been employed to illustrate the present invention, such has been the case merely for descriptive purposes and is not to be construed as limitative of the present invention, inasmuch as the fibrous structures herein set forth could be used in surgical dressings, compresses, disposable diapers, hospital underpads and the like.

FIG. 16 sets forth one method of preparing absorbent fibrous bodies of the present invention. Two superposedfibrous webs 73 and '74, such as low bulk density, coherent webs of loosely compacted, comminuted wood pulp fibers, so-called fluff, are delivered separately on conveyor belts from a disintegrating mill (not shown) which finely divides the wood pulp board or sheeting into individualized fibers. These webs may be compressed lightly in order to facilitate handling. The upper surface of the lowerfibrous web 74 is lightly moistened with water W in the form of a fine spray or mist from asuitable spray device 75 controlled by avalve 76. Theupper web 73 is then laid down upon thelower web 74 with the wetted surface of the lower web in direct con tact with the adjacent undersurface of the upper web. The two superposed webs are carried on a series ofconveyors 77, 78 to acompression device 79 consisting of alower idler roller 80 and an upper driven compression roller 81 whereby the web is compressed.

When the superposed webs reach the compression device, the fibers which have been moistened are in a relatively swollen condition whereas the remaining fibers are still substantially dry. The moistened fibers bond together under the compression exerted by the rollers to form the fibrous body having a densified inner layer similar to the structure set forth in FIG. 4 of the drawings. These is little or no tendency for the water to penetrate or permeate too deeply into the interior of the web unless an excess has been applied. The bonded webs are then conducted by theconveyor 78, 82 in the direction indicated by the arrow for cutting, shaping or other processing. The integral densified inner layer which is formed is a coherent structure possessing greater tensile strength, good form and shape stability, high fluid retentivity and high capillarity.

F116. 17 sets forth anembossing roller 84 which is used to form thelengthwise grooves 57 as illustrated in the absorbentfibrous body 56 shown in FIG. 12. These grooves may be made narrow or wide and the intervals between them may be varied depending upon the particular requirements of the situation involved. Theembossing roller 84 may be used with another similar embossing roller and the contacting relationship between the two may be so arranged that the projecting annular rings 85 of each of the embossing rollers may come into direct contact or they may be so staggered that the teeth of one fit within the intervals of the other, whereby varying designs may be obtained.

FIG. 18 discloses acompression roller 83 which can be used to compress the fibrous webs in a plane in accordance with the method disclosed in FIG. 16. These compression rollers are normally carried in vertical & stands and the pressure exerted thereby can be adjusted manually in the usual manner.

FIG. 19 sets forth adifferent embossing roller 86 having teeth 87 which may be used to form grooves in absorbent fibrous bodies extending crosswise thereof such as illustrated in FIG. 13 of the drawings. The axial length of the teeth 87 is equal to the crosswise length of the grooves and the spacing between the teeth 87 controls the intervals between the grooves in a longitudinal direction.

It is to be appreciated that other forms of compressing and embossing rollers could be used and that various planar, curved grooved or undulated surfaces may be obtained by the use of correspondingly shaped rollers.

Anembossing roller 86 may be used in combination with a pair of annular rings at each end thereof in order to obtain the grooved absorbent fibrous body illustrated in FIG. 14.

FIG. 20 illustrates an absorbentfibrous structure 88 comprising a centrally located, loosely-compactedfibrous body 89 and relatively densified, compactedgrooves 90 formed on the upper and lower surfaces thereof as by means ofembossing rollers 84. It is to be observed that thegrooves 90 on each surface are positioned directly opposite each other.

FIG. 21 illustrates an absorbent fibrous structure 91 comprising a centrally located, loosely-compacted fibrous body 2 and relatively densified, compactedgrooves 93 formed on the upper and lower surfaces thereof as by means ofembossing rollers 34. It is to be observed that thegrooves 93 on each surface are staggered widthwise with relation to each other.

It is to be appreciated that the spacing of the opposed gear-like embossing rollers must be carefully controlled in the manufacture of fibrous bodies as illustrated in FIGS. 20 and 21 and that the opposed gear-like surfaces must be close enough to provide the necessary pressure but not too close as to shear through the fibrous structure.

The present inventive concept was applied to two fibrous comminuted wood-pulp air-laid webs, each about 1 centimeter thick and having a bulk density of about 0.03 gram per cubic centimeter. By finely spraying about 0.00 15 cc. of water per square centimeter of web surface on each web, then superposing the webs and applying a pressure of about 15 pounds per square inch, an integral, absorbent fibrous body having a thickness of about 1.5-1.6 centimeters was obtained having a densified, coherent inner layer about 0.04-0.05 centimeter thick.

The use of different pressures of about 10 pounds and about 60 pounds per square inch in the presence of 0.0015 cc. water per square centimeter resulted in the conversion of lesser and greater proportions of the original web into the dense paper-like layers.

The use of moistures of 0.001 and 0.003 cc. per square centimeter was evaluated with a pressure of 40 pounds per square inch. The lesser amount of moisture (0.001) yielded an extremely thin, papery layer whereas the greater amount of moisture (0.003) yielded a heavier bonded layer usable where such density and strength was desirable.

These tests were repeated with two similar webs using 10, 15, and 60 pounds per square inch pressure but without the application of any moisture to determine the effect thereof on the dense inner layer. When the pressure was removed, there was no paper-like inner layer and there was no adhesion between the two layers beyond the amount normally obtained by interfiber frictional engagement. Likewise, when embossing rollers were used, the embossed effects were deficient in stability and were lost upon subsequent wetting.

Another trial was made under similar conditions but increasing the moisture to 0.004 cc. of water vapor per square centimeter of web surface. This time the dense inner layer was considerably thicker than that obtained structure is obtained by moistening both the lower and upper surface of an absorbent pad such as body and applying pressure to the surfaces.

FIG. 4 shows an absorbent fibrous structure 19 comprising an upper, loosely compactedfibrous body 26, a lower, loosely compacted fibrous body 21 and an intermediate relatively densified, compacted,coherent layer 22 formed integrally with the upper and lowerfibrous bodies 20, 21. Such a structure is obtained by moistening the face of one loosely compacted fibrous body, laying a second loosely compacted fibrous body atop the first and applying pressure thereto. If desired, the faces of both loosely compacted fibrous bodies may be moistened prior to being placed together for the application of pressure.

FIG. 5 sets forth an absorbentfibrous structure 23 comprising an upper, loosely compactedfibrous body 24, a lower, loosely compactedfibrous body 25, an intermediate relatively densified, compacted, coherentpaperlike layer 26 formed integrally with the upper and lowerfibrous bodies 24, 25 and a lower, relatively densified, compacted,papery skin 27 formed on the lower surface offibrous body 25. Such a structure is obtained, for example, by wetting both sides of a fibrous structure as body it} and laying it on a dry fibrous structure, the upper surface of which may be moistened, and then applying the required pressure.

FIG. 6 sets forth an absorbentfibrous structure 28 comprising an upper, loosely compacted absorbentfibrous body 29, a lower, loosely compacted absorbentfibrous body 30, an intermediate relatively densified, compacted, coherent paper-like layer 31 and relatively densified, compactedpapery skins 32, 33 on the upper and lower sur faces of the absorbentfibrous structure 28. Such a structure is obtained such as by wetting both sides of two fibrous structures, placing them together and then applying the required pressure,

FIG. 7 illustrates an absorbentfibrous structure 34 comprising an upper, loosely compactedfibrous body 35, a lower, loosely compactedfibrous body 36, an intermediate, relatively densified, compacted, narrower, coherent paper-like layer 37 formed integrally with the upper and lowerfibrous bodies 35, 36 and relatively densified, compacted, coherent, paper-like skins 38, 39 of different widths formed on the upper and lower surfaces respectively of thefibrous structure 34. Such a structure is obtained, for example, by wetting both sides of two fibrous bodies only in the area in which it is desired to form the relatively densified, compacted structures and then applying the required pressure.

FIG. 8 sets forth an absorbent fibrous structure 4-0 comprising an upper, loosely compacted fibrousabsorbent body 41, a lower, loosely compacted, absorbentfibrous body 42 having a width narrower thanbody 41, an intermediate, relatively densified, compacted, coherent, narrower, paper-like layer 43 formed integrally with the upper and lowerfibrous bodies 41, 42, and relatively densified, compacted,papery skins 44, 45 formed integrally on the upper and lower surfaces of the absorbentfibrous bodies 41, 42. Such a structure is obtained by using fibrous bodies of different widths and wetting them only in the areas wherein it is desired to effect the formation of paper-like members and then applying the required pressure.

FIG. 9 sets forth an absorbent,fibrous structure 46 comprising an upper, loosely compacted, absorbentfibrous body 47, a lower, loosely compacted, absorbent, narrowerfibrous body 48, an intermediate, relatively densified, compacted, coherent, narrower paper-like layer 49 formed integrally with the upper and lower absorbentfibrous bodies 47, 48 and a lower, relatively densified, compacted, papery,narrower skin 50 formed integrally on the lower surface of the lower, absorbentfibrous body 48. Such a structure is obtained by initially using two absorbent fibrous structures of different widths and moistening only the areas in which it is desired to create the paper-like members and then applying suflicient force not only to form the densified members but to force the narrower absorbent body partially into the upperabsorbent body 47.

FIG. 10 discloses an absorbent fibrous structure 51 comprising an upper, loosely compacted absorbent fibrous body 52, a lower, loosely compactedfibrous body 53, an intermediate, relatively densified, compacted, coherent, narrower paper-like layer 54 formed integrally with the upper and lower absorbentfibrous bodies 52, 53 and a lower, relatively densified, compacted, paper-like,narrower surface skin 55 formed integrally 011 the lower surface of lower absorbentfibrous body 53. Such a structure is obtained in very much the same fashion as the structure set forth in PEG. 9 with the exception that the applied moisture and pressure is sufficient to force the lower absorbent fibrous body substantially wholly within the upper absorbent fibrous body so as to create a smooth, flush lower surface.

It is to be appreciated that the distance the lower absorbent fibrous body penetrates the upper absorbent fibrous body depends upon the amount of moisture and pressure applied and, if desired or required, the narrower absorbent fibrous body could be forced wholly within the upper fibrous body so that its skin is within the wider absorbent fibrous body.

FIG. 11 is a cross-sectional view of an absorbent fibrous body and showsparallel grooves 57 andhigh regions 58 which extend between thegrooves 57.

FIG. 12 discloses an absorbentfibrous structure 56 formed with a plurality of longitudinally extending,compressed grooves 57 whereby any fluid deposited on the absorbent fibrous body and encountering the grooves tends to spread lengthwise along the fibrous body so that its absorbent effectiveness will be utilized more fully. In this form of absorbent fibrous structure there are regions of high and low capillarity within the densified layer itself. These differences in capillarity are due to the compressed grooves formed by an embossing roller to be described more fully hereinafter.

In FIG. 13, there is disclosed an absorbentfibrous body 59 whereingrooves 60 are positioned crosswise to the length of the body. These particular grooves provide strength and springiness to the body and add to its structural rigidity and form and shape stability. These grooves are impressed upon the absorbent fibrous bodies by means of embossing rollers to be described more fully hereinafter. It is to be noted that the crosswise grooves are separated by interveninghigh regions 61 and that they end before they reach the edges of the absorbent fibrous body. In this way fluids deposited upon the absorbent fibrous body tend to follow the grooves 6% but will not go beyond the ends thereof thereby confining the fluid to within the absorbent fibrous body itself.

FIG. 14 sets forth an absorbent fibrous body as possessing spaced, longitudinally extendinggrooves 63 and spaced, laterally extendinggrooves 64 having interveninghigh regions 55 which have not been compressed to the extent that thegrooves 64 have been. It is to be appreciated that any fluid deposited on the absorbent fibrous body will initially tend to follow thegrooves 64 laterally until thelengthwise grooves 63 are encountered, at which time the fluid will then tend to move longitudinally and contact othercrosswise grooves 64. This type of absorbent fibrous body possesses increased strength and springiness due to thetransverse grooves 64, superior fluid control by means ofgrooves 63 and 64 whereby a very complete and eifective utilization of the absorbent properties of the fibrous body is realized. The grooves in the absorbentfibrous body 62 may be obtained by a combination of embossing rollers to be described hereinafter.

FIG. 15 is a cross-section of asanitary napkin 66 embodying an absorbent fibrous structure of the present invention. An absorbentfibrous structure 67 comprising a relatively loosely compacted, porous,fluify body 68 and previously and the thickness of the completed integral Web was reduced correspondingly.

From the above, it is seen that loosely compacted absorbent fibrous bodies, which possess relatively loW cohesive strength, relatively poor shape and volume stability, relatively low fluid retentivity, and relatively lows capillarity, are converted to bodies possessing a relatively dense, compacted, coherent skin or interlayer which creates suflicient strength, shape and volume stability, fluid retentivity, and capillarity as to render the resulting structure especially suited and highly desirable for use as absorbent components in surgical dressings, sanitary napkins, compresses, disposable diapers, hospital underpads, and other products designed to absorb body fluids.

It is, of course, realized that various modifications and changes may be made within the spirit of the invention. For example, various materials such as highly absorbent wadding paper, gauze, non-woven fabrics, and the like, may be placed on the Wetted Web surface so that, after the pressure has been applied, the materials become integral with the thin paper-like skin which is formed. It is also contemplated that various materials such as bactericides, fungicides, dyestuffs, softening agents, sizing materials, adhesives, and the like, may be included in the Water used for moistening the surfaces of the webs. These processes reflect the well-known possibilities of mechanically modifying paper to obtain desired results or effects.

While I have shown and described What I believe to be preferred embodiments of my invention in the matter of simplicity and durability of construction, it will be appreciated that the details of such construction may be more or less modified within the scope of the claims without departure from the principles of construction or material sacrifice of the advantages of the preferred designs.

I claim:

1. A method of producing an absorbent fibrous body suitable for use as an absorbent component in absorbent products which comprises moistening a surface portion of a highly porous, loosely compacted, cellulosic fibrous bat having relatively low cohesive strength, relatively low capillary forces, relatively poor shape and volume stability, and relatively low fluid retentivity with from about 0.0005 to about 0.03 cubic centimeter of water per square centimeter of surface of said bat, applying a pressure of from about to about 100 pounds per square inch to said bat While the surface thereof is moistened with said water, said pressure being sufficient to form a paper-like, densified, compacted cellulosic fibrous layer it situ in said bat and integral therewith, said layer having relatively high cohesive strength, relatively good capillary forces, relatively good shape and volume stability, and relatively high fluid retentivity.

2. A method of producing an absorbent fibrous body suitable for use as an absorbent component in absorbent products which comprises moistening a surface portion of a highly porous, loosely compacted, cellulosic fibrous bat having relatively low cohesive strength, relatively low capillary forces, relatively poor shape and volume sta bility, and relatively low fluid retentivity with from about 0.0005 to about 0.03 cubic centimeter of Water per square centimeter of surface of said bat, applying pressure to said bat while the surface thereof is moistened with said water, said pressure being sufficient to form a paper-like, densified, compacted cellulosic fibrous layer in situ in said bat and integral therewith, said layer having relatively high cohesive strength, relatively good capillary forces, relatively good shape and volume stability, and relatively high fluid retentivity.

3. A method of producing an absorbent fibrous body suitable for use as an absorbent component in absorbent products which comprises applying water to a surface portion of a highly porous, loosely compacted, cellulosic fibrous bat having relatively low cohesive strength, relatively low capillary forces, relatively poor shape and volume stability, and relatively low fluid retentivity in an amount sufficient to moisten the surface portion thereof, placing a second highly porous, loosely compacted, cellulosic fibrous bat in contacting relationship with said moistened surface, applying pressure to said bats while the surface of said moistened bat is moistened with said water, said pressure being sufficient to form a paper-like, densified, compacted cellulosic fibrous layer intermediate said bats and integral therewith, said layer having relatively high cohesive strength, relatively good capillary forces, relatively good shape and volume stability, and relatively high fluid retentivity.

4. A method of producing an absorbent fibrous body suitable for use as an absorbent component in absorbent products which comprises applying water to a surface portion of a highly porous, loosely compacted, cellulosic fibrous bat having relatively low cohesive strength, relatively low capillary forces, relatively poor shape and volume stability, and relatively low fluid retentivity in an amount suflicient to moisten fibers in said bat adjacent said moistened surface portion but not to moisten all the fibers in said bat, applying pressure to said bat While the surface thereof is moistened with said water, said pressure being sufficient to form a paper-like densified, compacted cellulosic fibrous layer in situ in said bat and integral therewith, said layer having relatively high cohesive strength, relatively good capillary forces, relatively good shape and volume stability, and relatively high fluid retentivity.

5. A method of producing an absorbent fibrous body suitable for use as an absorbent component in absorbent products which comprises applying water to a surface portion of a highly porous, loosely compacted, cellulosic fibrous bat having relatively low cohesive strength, relatively low capillary forces, relatively poor shape and volume stability, and relatively low fluid retentivity in an amount suffioient to moisten the surface portion, applying pressure to said bat while the surface thereof is moistened with said water, said pressure being suflicient to form a paper-like, densified, compacted cellulosic wood pulp fibrous hydrate-bonded layer in situ in said bat and integral therewith, said layer having relatively high cohesive strength, relatively good capillary forces, relatively good shape and volume stability, and relatively high fluid retentivity.

6. A method of producing an absorbent fibrous body suitable for use as an absorbent component in absorbent products which comprises applying water to a surface of a highly porous, loosely compacted, cellulosic fibrous bat having relatively low cohesive strength, relatively low capillary forces, relatively poor shape and volume stability, and relatively low fluid retentivity in an amount sufficient to moisten the surface thereof, applying pressure to said bat While the surface thereof is moistened with said water, said pressure being sufficient to form a paperlike, densified, compacted cellulosic fibrous layer in situ in said bat and integral therewith, said layer having relatively high cohesive strength, relatively good capillary forces, relatively good shape and volume stability, and relatively high fluid retentivity.

7. An absorbent fibrous structure suitable for use as an absorbent component in absorbent products comprising a highly porous, loosely compacted, cellulosic fibrous bat having relatively low cohesive strength, relatively low capillary forces, relatively poor shape and volume stability and relatively low fluid retentivity, and integrally united therewith by bonds comprising interfiber bonds, a paper-like, densified, compacted cellulosic fibrous layer having relatively high cohesive strength, relatively good capillary forces, relatively good shape and volume stability and relatively high fluid retentivity, said paper-like, densified, fibrous layer being formed in situ from said highly porous bat.

8. An absorbent fibrous structure as defined in claim 7 wherein the fibrous layer is narrower than the fibrous bat.

9. An absorbent fibrous structure as defined in claim 7 wherein the fibrous layer is intermediate the surfaces of the fibrous bat.

10. An absorbent fibrous structure as defined inclaim 9 wherein the fibrous-layer is narrower than the fibrous bat.

11. An absorbent fibrous structure as defined in claim 7 wherein the fibrous layer is provided with grooves.

12. An absorbent fibrous structure as defined inclaim 11 wherein the grooves run lengthwise of the structure.

13. An absorbent fibrous structure as defined inclaim 11 wherein the grooves run widthwise of the structure.

14. An absorbent fibrous structure as defined inclaim 11 wherein the fibrous layer is provided with grooves running lengthwise and widthwise of the structure.

15. An absorbent fibrous structure as defined in claim 7 wherein the cellulosic fibrous bat comprises wood pulp fibers.

16. An absorbent fibrous structure as defined in claim 7 wherein the fibrous bat comprises cotton linters.

References Cited in the file of this patent UNITED STATES PATENTS Parks Jan. 14, 1919 Brown Jan. 23, 1923 Brown et al June 19 ,1923 Mason Mar. 20, 1928 Robinson Mar. 22, 1932 Fourness Dec. 26, 1933 Grapp Jan. 9, 1934 Madge et al Aug. 13, 1935 Hamersley Apr. 20, 1937 Gates Aug. 18, 1942 Briggs June 15, 1943 Francis Jan. 25, 1949 Dreyfus Feb. 14, 1950 Porritt May 23, 1950 Lang Sept. 12, 1950 Kellett et a1 Oct. 2, 1951 Schramm Feb. 9, 1954 Fortess Nov. 2, 1954

Claims (1)

1. 2. A METHOD OF PRODUCING AN ABSORBENT FIBROUS BODY SUITABLE FOR USE AS AN ABSORBENT COMPONENT IN ABSORBENT PRODUCTS WHICH COMPRISES MOISTENINGA SURFACE PORTION OF A HIGHLY POROUS, LOOSELY COMPACTED, CELLULOSIC FIBROUS BAT HAVING RELATIVELY LOW COHESIVE STRENGTH, RELATIVELY LOW CAPILLARY FORCES, RELATIVELY POOR SHAPE AND VOLUME STABILITY, AND RELATIVELY LOW FLUID RETENTIVITY WITH FROM ABOUT 0.0005 TO ABOUT 0.03 CUBIC CENTIMETER OF WATER PER SQUARE CENTIMETER OFSURFCE OF SAID BAT, APPLYING PRESSURE TO SAID BAT WHILE THE SURFACE THEREOF IS MOISTURED WITH SAID WATER, SAID PRESSURE BEING SUFFICIENT TO FORM A PAPER-LIKE DENSIFIED, COMPACTED CELLULOSIC FIBROUS LAYER IN SITU IN SAID BAT AND INTEGRAL THEREWITH, SAID LAYER HAVING RELATIVELY HIGH COHESIVE STRENGTH, RELATIVELY GOOD CAPILLARY FORCES, RELATIVELY GOOOD SHAPE AND VOLUME STABILITY, AND RELATIVELY HIGH FLUID RETENTIVITY.

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