US 3491802 A
Description (OCR text may contain errors)
Jan. 27, 1970 1 A, MORTENSEN ET AL 3,491,802
OPEN MESH WOVEN FIBRoUs ABSORBENT MEDIA 3 Sheets-Sheet l Filed Jan. l0, 196'? Jan. 27, 1970 J. A. MoRTr-:Nsl-:N `ETAI- .OPEN MESH WOVEN FIBROUS ABSORBENT MDI.
Filed Jan. l0, 1967 r'llzi- :10o/corded l Qbaze 5 Sheets-Sheet 2 Q0 QQ OO g 8o Q OO o ATTORNEY Jan. 27., 1970 J. A. MoRTENsEN ETAI- 3,491,802
OPEN MESH WOVEN FIBROUS ABSORBENT MEDIA 3 Sheets-Sheet 5 Filed Jan. l0, 196'? United States Patent O U.S. Cl. 139-420 1 Claim ABSTRACT OF THE DISCLOSURE Multi-ply open mesh Woven absorbent fibrous pads are prepared by (1) weaving an open mesh fabric of yarns consisting mostly of absorbent7 preferably nonshrinkable, fibers but also containing highly shrinkable fibers, (2) subsequently causing the shrinkable fibers to shrink to popcorn the yarns while controlling the shrinking to provide webs having a finished thread count of between and 45 threads per square inch, and (3) folding the webs thus produced to form the pad. The pads provided have a higher absorbent capacity and a lower tendency to abrade the surface which they are used to Wipe than do prior art multi-ply pads.
BACKGROUND OF THE INVENTION Open mesh woven absorbent fibrous webs such as gauze and the like have long been folded to form multiply pads and used as wipes for many purposes from the washing of vehicles and the like on one hand to surgical uses such as the wiping of blood and other substances from the skin of a patient on the other. As indicated above, these pads most often consist of a multiplicity of plies of cotton gauze woven at a thread count of about by 12 threads per inch.
While these gauze wipes have been more than adequate for most purposes to which they have been applied, all concerned have naturally been continually searching for materials to form such pads which are improved in one or more properties. If one were to choose one or two properties of gauze wipes which could possibly be improved upon, one would probably choose to increase the absorbent capacity of the wipe and to lower its tendency to abrade surfaces which it is used to wipe.
SUMMARY OF THE INVENTION According to this invention, an absorbent wipe is provided which is dramatically improved from the standpoint of possessing a higher total capacity to absorb fluids and a lower tendency to abrade the surface which it is used to wipe. Specifically the open mesh, woven, fibrous absorbent wipes of this invention comprise a multiplicity of plies of a woven, open mesh absorbent fabric superimposed one on top of the other, said fabric having a yarn count of from about 15 to about 45 yarns per square inch, most of said yarns consisting mostly of absorbent fibers and a majority of said yarns having a relatively thin and hard core of generally axially extending fiber portions surrounded by a relatively thick highly absorbent fluffy and hairy yarn sheath consisting of portions projecting outward from the core a substantial distance, said projecting fibers in said yarn sheaths in each ply projecting into adjacent plies of the fabric and cooperating to form a series of three dimensional absorbent and cushioning cells within said pad and said sheaths of said yarns adjacent the outer surface of the pad acting to cushion forces applied to the pad during use.
In the preferred practice of the invention, the fabric should have a thread count of between about 18 and about threads per square inch, it having been found that the 3,491,802 Patented Jan. 27, 1970 ice absorbent capacity of the web is highest when the thread count is within this range.
In making the wipes of this invention, a gauze-like material is suitably woven from yarns consisting of from about 70 to 90% absorbent cellulosic fibers or filaments such as cotton or rayon, which shrinks at most slightly on heating, and of from.. about l0 to 30% of highly shrinkable filaments preferably thermoplastic filaments such as polypropylene and the like which shrink substantially on heating. By then shrinking the highly shrinkable filaments in the yarns, these filaments are caused to form a small hard yarn core and portions of the cellulosic fibers are caused to project outward from the core and to thus form the cushioning sheaths and the absorbent cells referred to above. The yarns are best described as having been popcorned The preferred process utilized in making the pads of this invention and the product itself should not be confused with so-called bulked fabrics of the type described in U.S. Patent 2,627,644 to Foster wherein a gauze-like structure is formed of nonthermoplastic yarns alternating with thermoplastic yarns and the latter thereafter shrunken. By thus shrinking the thermoplastic yarns, the nonthermoplastic yarns which do not shrink are caused to buckle and thus the fabric is said to be bulked. However, in webs of that type the individual nonthermoplastic yarns do not increase substantially in size and bulk. The fabric is bulky primarily due to certain yarns as a unit lying out of the general plane of the fabric. In the fabrics of this invention, differential shrinkage occurs within the interior of the yarns to give substantial bulk to the yarns themselves.
The preferred process utilized in making the pads of this invention and the products resulting therefrom should also not be confused with multi-ply pads formed of fabrics of the type described generally, for example, in U.S. Patent 3,190,289 to Patience and the process used to make the same. Fabrics of that type are usually Woven in the conventional manner from cellulosic yarns and immersed in a hot caustic bath which is strongly agitated to cause the yarns to assume sinuous or torturous formations to cause the fabric to shrink and thus become thick and bulky. There is little or no differential shrinkage within a given yarn and thus the yarns do not have thin hard cores surrounded by thick soft sheaths of fiber portions projecting outward from the core of the yarn, rather the fabric is bulky primarily because certain yarns project as a unit out of the general plane of the fabric.
Finally, the multi-ply pads of this invention should not be confused with single ply popcorned fabrics in general of the type described in Hercules Powder Co. Bulletin FD-3A of May 1, 1963 which describes woven fabrics made of yarns consisting of cotton, viscose rayon and/or wool and 20% polypropylene filaments, the yarns having been heat shrunken. The products of this invention and the novel and surprising properties of the same are dependent on the pad having a finished thread count of between about 15 and about 45 threads per square inch and on the same and being formed of a plurality of plies of the popcorned fabric.
The invention will be more clearly understood after reading the following description in reference to the appended drawings. In the drawings,
FIG. 1 is a view in perspective of a conventional prior art gauze wipe;
FIG. 2 is a cross section of the wipe of FIG. 1 taken taken along lines 2-2;
FIG. 3 is a plan view of a popcorned absorbent product of this invention;
FIG. 4 is a cross section of the product of FIG. 1 taken along lines 4-4;
FIG. 5 is a greatly enlarged view in perspective of one absorbent cell within the product of FIG. 3;
FIG. 6 is a typical graph of absorbent capacity vis. thread count for both the prior art wipes and the wipes of this invention;
FIG. 7 is a photomicrograph of a plexiglass surface which has been wiped with a prior art gauze wipe;
FIG. 8 is a photomicrograph of a plexiglass surface which has been wiped with a product made in accordance with the Patience Patent 3,190,289;
FIG. 9 is a photomicrograph of a plexiglass surface which has been wiped with the product of this invention.
Referring now to FIGS. 3-5, the absorbent wipe 11, illustrated therein consists of four plies of a 20 by 12 yarns to the inch woven gauze-like web 12 superimposed one on another. The individual yarns 13 and 14 consist of about 80% ll/zdenier cotton staple having an average length of 1% inches and about 20% polypropylene laments having a denier of about 3 and an average fiber length of about 1% inches.
The web 12 has been exposed to temperatures of about 325 F. which almost instantaneously causes the polypropylene filaments in the yarns 13 and 14 to shrink by about 50% in both the warp and the fill direction. This shrinkage of the polypropylene filaments causes these filaments to concentrate in the center of the yarn and form a thin hard core 15, as shown in FIG. 5 of the drawings, thus forcing the cotton fibers 16 to move outward and form a thick soft sheath around the yarn core consisting of cotton fiber portions 17 projecting outward from the core. As can be seen most clearly in FIG. 5, the projecting fiber portions 17 in adjacent layers 18 and 19 of the pad project from one fabric layer into adjacent layers and cooperate to form absorbent cells 20 within the pad.
ABSORBENT CAPACITY The parameters used to evaluate and compare the absorbent capacity of multi-ply wipes is (1) the maximum fluid capacity for a given area of unfolded fabric and (2) fluid capacity of wipes of equal fabric weight` The absorbent capacity of the pad 11 illustrated in FIGS. 3-5 is substantially `greater than the absorbent capacity of a pad of equal unfolded surface area made of multiple plies of gauze or multiple plies of material made in accordance with U.S. Patent 3,190,289. This is true at all thread counts within the earlier described limits.
In Table I, data is provided comparing the absorbent capacity of the wipes of this invention and conventional gauze wipes made of equal unfolded surface areas (192 square inches) of material. Sample A is the 4 inch by 4 inch pad 1, made of 12 plies of 20 by 12 thread to the inch cotton gauze 2, the individual threads 3 and 4 having a cotton count of 30s singles in the warp and 40s single in the fill and the fibers in the yarns having a fiber length of about 1%@ inches.
Samples B, C and D are prepared in accordance with this invention. The fabric is woven from yarns having a cotton count of 30s singles and consisting of 80% 11/2 denier cotton fibers and 20% 3 denier polypropylene filaments. The yarns are woven into a fabric at a thread count of 12 by 7 threads to the inch and the fabric is then passed through an oven at 325 F. at low tension in both directions to shrink the polypropylene filaments by about 35% and to thus cause the polypropylene filaments to core and the cotton fibers to project outward from the core. The finished thread count of the fabric is about 20 by 12 threads to the inch. Sample B is a six ply 4 inch by 8 inch pad made from this fabric while Sample C is a four ply 4 inch by 12 inch pad and Sample D is a two ply 4 inch by 24 inch pad. Thus, both the ganze sample and the popcorned pads have an unfolded surface area of 192 square inches.
These pads are then subjected to a test for maximum absorbency which is carried out according to the U.S.P. test for absorbency for cotton and gauze.
TABLE I Sample: Absorbent capacity (gms.)
A 14.65 B 33.40 C 37.80 D 35.60
As can be seen from Table I, the wipes of this invention have an absorbent capacity of up to 2.5 times that of conventional gauze wipes.
These tests are repeated to compare the performance of wipes of this invention with wipes made in accordance with U.S. Patent 3,190,289. Sample E is a l2 ply, 4 inch by 4 inch pad made of a fabric treated as described in U.S. Patent 3,190,289 at a finished thread count of 14 by l0 threads to the inch. Sample F is made in accordance with this invention and is a six ply 4 inch by 8 inch pad made of material having an approximate thread count of 14 by 10 threadsv to the inch. The results of these tests are noted in Table II and it can be seen that the wipes of this invention have an absorbent capacity of over two times that of wipes of the type described in U.S. Patent 3,190,289.
TABLE II Sample: Absorbent capacity (gms.)
Similar results are obtained when the absorbent capacity of equal weights of each of the pads are compared. These results are tabulated in Tables III and IV. Tables III and IV are prepared in the following manner:
The 12 ply, 4 by 4 pad of 20 by l2 threads to the inch (Sample A) gauze has an original weight of 2.35 gms. The other pads formed have a weight somewhat less than this. Thus, the absorbent capacity data previously reported for these other pads is converted to a base weight of 2.35 gms. in order to arrive at the figures in Tables III and IV.
TABLE III Sample: Weight of water absorbed (gms.)
TABLE IV Sample: Weight of water absorbed (gms.)
The reasons for this dramatic increase in the absorbent capacity provided by this invention can again best be seen by reference to FIG. 5. As the polypropylene filaments 15 in the yarns shrink and core thus causing the cotton yarns 16 to bulk substantially and project generally outward from the core. Thus, when several layers of the fabric are plied together, the projecting fiber portions 17 in the adjacent layers 18 and 19 tend to cooperate to form the three dimensional absorbent cells 20 referred to earlier. In addition, each individual yarn itself is more absorbent due to its more open fluffy outer portion or sheath thus forming highly absorbent areas 21 around the absorbent cells 20. Of course, the web interstices in adjacent layers will not usually be in registry as shown in FIG. 5 and the absorbent cells may be torturous in shape, however, FIG. 5 is meant to illustrate the principle involved.
As can be seen from the typical graph of FIG. 6, comparing the absorbent capacity of multi-ply gauze pads and multi-ply pads of this invention on an equal weight basis,
the pads of this invention have a substantially greater absorbent capacity than do the prior art pads for any web having a thread count between 15 and 45 threads per square inch. This includes finished web constructions having a thread count as low as by 8 as well as thread count as high as 24 by 20. However, it is expected that in the practice of the invention, webs having a thread count of between about and about 35 threads per inch will be utilized since it has been found that the curve of absorbent capacity vs. thread count reaches a maximum at a thread count of about threads per square inch.
WET RESILIENCE The absorbent -pads also have a substantially higher Wet resilience than do prior art gauze pads or any of the other prior art pads heretofore referred to. Wet resilience is determined by placing a 300 gm. weight on top of a pad which is saturated with fluid. The weight is removed and after one hour the thickness of the pad is compared to the thickness of the pad prior to the placing of the weight on the same. Typical 12 iply, 20 by 12, gauze pads have a wet resilience of about ll/2%. However, 6 ply, 20 by 12, pads of this invention have a wet resilience of over 38%. This property is important to the pad retaining its bulk when wet and thus retaining its high absorbency. The high wet resilience is thought to be due to the cushioning effect caused by the cooperation of the soft hairy outer yarn portions of yarns in adjacent layers of the pad.
TENDENCY TO ABRADE As previously mentioned, it has also been surprisingly found that the pads of this invention have a substantially lower tendency to abrade the surface which they are used to wipe than do conventional gauze wipes or wipes prepared in accordance with U.S. Patent 3,190,289 to Patience. Despite this low tendency to abrade, it is found that the wipes of this invention in fact tend to have a better degree of scrubability than the prior art wipes because of the improved wet resilience referred to above. In a controlled test, a Plexiglass airplane windshield was wiped with three different absorbent wipes. The pane of plexiglass was wiped with a conventional gauze wipe of the type previously described. It was found that grooves of considerable depth were formed in the same, which illustrates that prior art gauze wipes may tend to seriously and permanently abrade certain surfaces which they are used to Wipe. In gauze wipes, a hard and rigid yarn contacts the surface being wiped. As one presses very hard on the wipe, yarns in outward lying gauze layers also contact the surface through the windows or openings in the surface layer.
In a second wipe of a pane of Plexiglass the wipe prepared in accordance with U.S. Patent 3,190,289 to Patience was employed. While the grooves formed on this pane of plexiglass are not quite as deep as those on the pane of Plexiglass wiped with the conventional gauze wipe, they are much greater in number. The yarn portions contacting the Plexiglass are still hard and rigid and since the threads follow a torturous path, many more contact the Plexiglass surface when pressure is applied to the pad.
In a third wipe of a pane of Plexiglass the wipes prepared in accordance with this invention were employed. After wiping has been completed, essentially no permanent or deep grooves are found in the Plexiglass. The cushioning effect of the cooperating soft hairy outer yarn portions in adjacent layers within the absorbent pad tend to absorb somewhat the forces exerted downward on the pad by the user and to distribute these forces more evenly along the surface of the pad touching the surface which is to be wiped. In addition, instead of harsh hard yarn portions touching the surface which is wiped, the surface is contacted by the soft outer yarn portions of both the yarns at the surface of the pad and the yarns in inner layers of the pad which contact the surface being wiped through the interstices in the outer layers of the pad.
The successful popcorning of the fabric and therefore the successful creation of the three dimensional and cushioning cells previously referred to and described is dependent on `a number of parameters including, for example, the length of the staple fibers in the yarns, the denier of the fibers in the yarns, the yarn size itself, the twist and twist multiplier of the yarns, the percentage of thermoplastic fibers in the yarns, and the degree of shrinkage to which the thermoplastic fibers are subjected.
The thermoplastic fibers may be present in the yarns in amounts of between about 5 and about 35%. As the lower level of these limits is reached, the yarns usually lack sufficient pullback power to cause sufficient popcorning of the yarns in most fabric constructions. However, above about 35% the yarns seem to lack sufiicient bulk in the final product. This is probably due to the high proportion of thermoplastic fibers causing the yarns to be rather hard and stiff and due to the lack of a sufiicient number of fibers projecting outward from the core of the yarns.
The denier of the thermoplastic fibers may be varied between about 1.5 and about 6, however, when deniers much above 6 are utilized, there may be a high degree of fiber slippage during the heat shrinking process and thus adequate popcorning of the yarns may not be obtained. In selecting the staple length of the polypropylene fiber, lengths of above about 1 inch may be used. However, very long staples will tend to reduce the coring effect previously described while very short staples will tend to increase the possibility of fiber slippage during the heat treatment, thus substantially reducing the bulk. Preferably polypropylene fibers having a staple length of somewhere between about 1 and 11/2 inches should be utilized.
Two of the most important parameters in successfully providing products according to this invention are the twist multiplier of the yarns and the degree of shrinkage. If the twist multiplier of the yarns is much above about 4.75, popcorning will not occur and the same will remain hard as in the prior art fabrics. However, if the twist multiplier is much below about 3, it is difficult to handle the yarns and form the web. In order to provide the effects noted earlier, the yarns must be shrunken suiciently to cause coring and to cause the absorbent fibers to project well outward from the core. It has been found that this can be accomplished by shrinking the yarns anywhere from about 15% to about 65%. However, in the preferred practice of the invention, shrinkage of about 25% to 50% will be utilized.
It has been found that the improvements disclosed herein may be obtained while utilizing any of the cellulosic fibers as the nonthermoplastic component of the yarn, although cotton or rayon fibers are preferred. While it is desirable that each yarn have the popcorned construction illustrated and described, imperfections in the bulking process make this generally impossible and up to about half of the yarns or up to about half of the length of any given yarn may not be popcorned at all. It may be desirable in some cases to construct the fabrics only partially of yarns which can be popcorned In the samples used for the test results, tabulated in Tables I to V, a close examination shows that only about 1/2 of the yarns or yarn lengths were bulked.
While specific examples of products of this invention have been described, they are meant to be only illustrative of the broader inventive concept, which is limited only by the claims. For example, while differential heat shrinking has been disclosed as a specific method of providing popcorned yarns, other shrinking methods, such as, differential moisture shrinking may be used. In addition, shrinking need not be used at all, the finished yarn constructions described being provided by other methods.
What is claimed is:
1. A Woven open mesh absorbent pad comprising a multiplicity of plies of a woven open mesh absorbent fabric superimposed one on top of the other, said fabric having a yarn count of from about 15 to about 45 yarns per square inch, most of said yarns consisting mostly of absorbent bers and a majority of said yarns having a relatively thin and hard core of generally axially extending thermoplastic fiber portions surrounded by a relatively thick absorbent fluffy and hairy yarn sheath consisting of cellulosic ber portions projecting outward from the core a substantial distance, said projecting bers of said yarn sheaths in each ply projecting into adjacent plies of the fabric and cooperating to form a series of three dimensional absorbent and cushioning cells within said pad and said yarn sheaths adjacent the surface of the pad acting to cushion forces applied to the pad during use.
References Cited UNITED STATES PATENTS 2,656,585 10/1953 Jackson. 3,190,289 6/1965 Patience 12S- 296 3,367,333 2/1968 Scheier 12S-284 HENRY S. JAUDON, Primary Examiner.
U.S. Cl. X.R. 128-296