US 3917448 A
Random fiber webs are made from fibers, having different coefficients of heat shrinkage. When the web is subjected to heat the shrinking of the heat-shrinkable fibers causes the lower shrinkage fibers to buckle and loop so that air spaces are created and the bulk and texture of the web is improved. Various types of fibers, natural, synthetic, mineral, etc., may be employed. Also composite synthetic filaments may be used in which the core and sheath have different coefficients of heat shrinkage.
Description (OCR text may contain errors)
"United States Patent 1191 p Wood 5] Nov. 4, 1975  RANDOM FIBER WEBS AND METHOD OF 3,494,821 2/1970 Evans 161/169 M G S 3,755,028 8/1973 Wood 156/622  Inventor: Dennis E. Wood, Rochester, NY.  Assignee: Rondo Machine Corporation, 'f Exami' ler Gerge Lesmes Mocedon Asszstant Exammer.l. Cannon I Attorney, Agent, or FirmSh1esinger, Fitzsimmons &
FlledZ Jan. 4, Shlesinger  Appl. No.: 320,924
Related US. Application Data AB C  Continuation of Ser. No. 841,215, July 14, 1969,  S T abandoned. Random fiber webs are made from fibers, having dif- 52 CL u ferent coefficients of heat shrinkage. When the web is 1 U 28/76 gf subjected to heat the shrinking of the heat-shrinkable 161/59, 161/152' fibers causes the lower shrinkage fibers to buckle and 161/166, 161/169 loop so that air spaces are created and the bulk and  Int Cl 6 1/02 texture of the web is improved. Various types of fi-  Field 28/72 2 R ets, natural, synthetic, mineral, etc., may be em- 28/76 -}/i 6 153 ployed. Alsocomposite synthetic filaments may be 166 1 72 156762 62 used in which the core and sheath have different coefticients of heatshrinkage.  References Cited 6 Claims, 6 Drawing Figures US, Patent NOV.4, 1975 3,917,448
INVENTOR. DENNIS E. WQOD RANDOM FIBER WEBS AND METHOD OF MAKING SAME This application is a continuation of my application, Ser. No. 841,215, filed July 14, 1969 and now abandoned.
The present invention relates to nonwoven fabrics and more particularly to random fiber webs.
The characteristics of nonwovens are determined by the properties of their component fibers and finishing.
Since the properties of the established fibers and those of the new synthetics differ greatly, the application of these synthetics to nonwovens has ofter been found unsatisfactory. Physical properties such as denier and staple length together with various blends of different fibers can be varied so that greatly diverse nonwovens can be manufactured. However, although these nonwovens offer functional performance they lack the esthetic qualities of handle and appearance.
The primary object of this invention is to produce nonwoven fabrics of great resilience, improved softness, and luxurious tactile handle.
Another object of the invention is to produce nonwoven fabrics having the qualities mentioned in which,the nonwoven fabrics are a blend of natural and synthetic fibers or of various types of synthetic fibers.
Other objects of the invention will be apparent hereinafter from the specification and from the recital of the appended claims particularly when read in conjunction with the accompanying drawing.
It has long been known that synthetic fibers differ from natural fibers in four important respects.
a. Heat sensitivity b. Feltability c. Slickness, and
d. Chemical reactivity It is the first of these differences, heat sensitivity, the ability of man-made fibers to shrink with the application of heat, that is primarily taken advantage of in practicing the present invention. In fact, variation in two properties of the fiber used in the nonwoven, denier and the shrinkage, have proven most valuable in achieving improvements in fabric esthetics.
Although most of the applications have been made using acrylic or polyester fibers, any synthetic fiber may be used which has the ability to shrink, such as Dacron 61 plasticized cellulose acetate, copolymers of polyvinyl chloride and polyvinyl acetate known as vinyon, and polyvinyl alcohol fibers which have not been formaldehyde-treated. Other suitable fibers will readily occur to those skilled in the art.
Lofty nonwovens of acrylic fibers are made by blending fibers possessing different levels of heat shrinkage. Upon hot finishing, the more heat shrinkable fibers cause the nonwoven to shrink so that the lower shrinkage fibers buckle and loop, giving a lofty appearance. It has also been found that after shrinking, the high shrinkage fibers become stable and no further shrinkage will occur in normal use. This effect called the differential shrinkage can be used in nonwovens to improve texture, give light weight, bulky fabrics, improve cover and body, and preferentially place low shrinkage fibers on the nonwoven surface. Cover, bulk and improved texture are caused by the low shrinkage fibers being forced into the spaces previously existing between adjacent fibers. This smooths out the appearance of the nonwoven particularly on the surface of the fabric, making the fibers less apparent both visually and to the touch. The bulk and the amount of shrinkage of a given nonwoven depend on the relative amounts of high shrinkage fibers used and the residual shrinkage of those fibers.
Bulk is important in nonwovens, since it is an indica- 7 tion of the thermal efficiency of the nonwoven structure. It can be defined as the volume in cubic centimeters of a piece of nonwoven material weighing one gram. The bulk in nonwoven webs is a function of the amount and number of air spaces between the individual fibers within the structure. If straight fibers are used, they tend to lie closely together. Also, the more compact the web the less the covering power. So that if the fibers are curled or crimped, air spaces will be created and the structure will occupy a volume greater than the density of the total fibers. This bu1k" creates a better yield, more warmth and greater aesthetic appeal.
By comparison a nonwoven made of a blend of orlon, 20% wool, 10% rayon without high shrinkage orlon fibers gave an overall shrinkage of 10% yet the appearance was hard and the fibers distinct; the different fibers stood out too sharply, and the fabric felt rough. Yet in a nonwoven with the same parameters but with 30% of the 70% of orlon as high shrinkage fibers, the individual fibers become indistinct, the appearance is softened, and the surface feels smooth and continuous, the overall shrinkage is 24%.
It can be shown that an increase in the amount of high shrinkage fibers from O to 35% will raise the bulk or a representative nonwoven from 3.4 to 4.5 cm /gr. This is caused by the increase in bulk brought about by greater shrinkage. However, if the amount of high shrinkage fiber be increased from 35% to the bulk becomes less and less due to the steady decrease in the number of bulk-forming loops of the low shrinkage fibers. It will therefore be seen that these nonwovens contain a considerably greater volume of air than fiber and that the warmth of the nonwoven is dependent primarily on the amount of air within the material. Therefore the number of fibers and amount of air spaces influence the insulating properties.
The amounts of high shrinkage fiber become increasingly less effective because the decrease in shrinkage forces becomes less as the shrinkage approaches its maximum potential. The use of 30 to 40% high shrinkage fiber has been found to give the best results because at this level the fabric shrinkage is more uniformly controlled and less sensitive to variations in blend composition.
Most nonwovens made of low shrinkage man-made fibers shrink about 10 to 15% depending upon the fiber lay and bonding treatment whereas nonwovens containing high shrinkage fibers can shrink up to 40%. This shrinkage is dependent upon the residual shrinkage of the fiber. Normal residual shrinkage is about 20% but ultra high residual shrinkage fiber of about 50% shrinkage gives very good results.
In general, the objects of this invention are accomplished by forming a nonwoven material with a percentage of shrinkage synthetic fibers blending with non-shrinkable fibers either of naturaLsythetic, vegetable, animal, or mineral types into a web in which the fibers have haphazard arrangement. The web is made of non-matted uncompressed fibers, which are arranged randomly in three dimensions, namely, in all directions along the length, width, and depth of the web. These nonwoven webs may be manufactured by machines which use the air lay principle, where the fibers are collected upon a foraminous surface aided by suction or a reduced pressure such as disclosed in my pending application Ser. No. 691,544, filed Dec. 18, 1967 now US. Pat. No. 3,535,187, issued Oct. 20, 1970.
In this machine two different types of fibers may first be formed into two separate fiber mats, and the fibers are combed from the two mats by rotating lickerins, are doffed from the lickerins by centrifugal force and air streams, and are carried in the air streams through separate ducts into a condensing chamber in the nip between two oppositely rotating foraminate condensers, and simultaneously continuous filaments or another type of fiber may be fed into the condensing chambers between said ducts and also into the nip between the two oppositely rotating condensers. Thus a random fiber is formed, in which different fibers may predominate in different zones of the web but which is different from the ordinary laminated web because of the interfiber entanglement throughout the web and of the blending of fibers at the interface areas of the various zones of the web. The random web formed on the condensers is delivered onto a conveyer which carries it out of the machine.
After formation, the web is exposed to treatment effective to shrink the retractable fibers. The shrinking of these retractable fibers gives the web bulk, increased density, improved softness and luxurious tactile handle not heretofore attained in a nonwoven web.
A web constructed in accordance with the invention comprises a plurality of non-matting fibers, either straight or curled or crimped, of various lengths and types, with a percentage of shrinkable fibers in random arrangement throughout the web. The shrinkable fibers may be blended in such way that a preponderance of shrinkable fibers are arranged on one or both surfaces, or may be arranged only within the center structure of the web. The lengths of the fibers may vary from /2 inch to 2 inches.
The truly nonwoven random or haphazard arrangement of the web constructed in accordance with this invention is easily distinguished for prior art webs, which are sometimes referred to as nonwovens, such as batts made by felting, garnetting or carding machinery. In these processes the batts so made have a predominate arrangement of fibers which lay parallel to each other giving strength principally in one direction. These batts are usually light in weight and with little loft. The batts are either laid up by tandem systems or formed by a laminating technique using a series of individual webs and tieing these together; or they may be cross lapped, or formed by a combination of these two methods, whereby suitable weights are built up. These methods are, however, slow and time-consuming. Also, these systems give a layer of fibrous masses and not a true blend as is required by this invention.
Also the process of this invention should not be confused with felt making where a carded batt or a crosslaid material is built up by interlocking the fibers by mechanical work, chemical action, moisture and heat, without spinning, weaving or knitting, the ordinary process being by hardening the batt by rubbing the felting, or fulling, to produce a dense, compact material. Nor should this process be confused with semifelted materials which may also be made ofa carded type batt built up by cross-laying or similar means which contain retractable materials. Such materials must be severely needled to secure the layers of material together; and thereby a compacting effect is caused which may reduce the batt in volume by as much as 50%, so that, after heat-working, the web will be shrunk at least 60% and more. This reduces the number of air spaces or voids thereby lowering the porosity, resilience, and loft.
Preferably with this invention truly isotropic nonwovens are produced with the fibers intermingled randomwise in three-dimensional arrangement throughout length, width, and depth of the web with individual fibers extending transversely throughout-the depth of the web to opposite upper and lower surfaces thereof and tying the web into a intergral structure from said upper and lower surfaces. The importance of having a random, three-dimensional arrangement of uncompressed fibers cannot be over-emphasized.
Preferred embodiments of the present invention are illustrated on the attached drawing, and are as follows:
In the drawing:
FIG. 1 is a fragmentary sectional view of a random fiber web made according to one embodiment of this invention;
FIG. 2 is a similar view of a web made according to another embodiment of the invention;
FIG. 3 is a corresponding view ofa web made according to a further embodiment of the invention;
FIG. 4 is a similar view of a web made according to another embodiment of the invention;
FIG. 5 is a sectional view of a web made according to a Still further embodiment of the invention; and
FIG. 6 is a similar view of a web made according to still another embodiment of the invention.
FIRST EXAMPLE The nonwoven web 10 (FIG. 1) is made on a machine such as mentioned above so that the fibers are preferably of various lengths from about A inch to 2 inches and are a blend of orlon ll, 20% wool 12 arid 10% rayon 14. The 70% of orlon fibers 11, which is made up of 30% high shrinkage fiber with a residual shrinkage of 17% is intermingled in random arrangement so that these fibers lay at various angles, both horizonta'lly and vertically to form a three-dimensional web with the individual fibers contacting each other at their separate points of contact throughout the web. Relatively few pairs of individual fibers contact at more than one point; and each fiber of the web contacts a plurality of other fibers at spaced points which may be in the same or in different planes, there being individual fibers extending transversely throughout the depth of the web to opposite upper and lower surfaces, thereby tying the web into an integral structure from said upper and lower surfaces.
The web, after formation, is transported by acontinuous conveyor to a heating chamber for heating to a temperature of say C for 5 minutes. The amount of heat is sufficient to retract the shrinkable fibers but not allow them to become completely amorphous in character. The residual shrinkage of the 30% of high shrinkage fiber causes them to buckle and loop causing them to be forced into the spaces previously existing between adjacent fibers providing coherence of the already integral web, imparting texture, also lightness and weight,
' bulky softness and porosity.
SECOND EXAMPLE The required web 15 (FIG. 2) is prepared from 70% polyacrylonitrile fibers 16, 20% wool fibers 17, and staple 150 Lurex MM metallic fibers 18, so that 60% of the acrylic fibers are retractable with a residual shrinkage of 25%. These fibers are blended in three groups; (a&b) 5% Lurex, 10% wool and 23% acrylic shrinkable fibers per group, and (c) 10% nonshrinkable, 14% shrinkable acrylic fiber. Blends (a&b), 24 and 26, respectively, are processed through the outside randomizing chambers of the machine disclosed in the above-noted U.S. Pat. No. 3,535,187; blend (c), 25, is processed through the center section of this machine, giving a truly isotropic web; yet arranging the blends in three zones 24, 25, 26, so that the wool and Lurex fiber appear in both the upper and lower surfaces of the web. The web so formed is needled and heat treated so that the overall shrinkage is only 27% with a bulk of a little over four cubic centimeters per gram.
This example is given to illustrate the interesting and novel types of webs which may be formed from materials dissimilar in characteristics and from fibers of differentially retractable residual shrinkages. For example, a three blend web may be prepared with two zones of one material and a third zone of a different material, so that when the web is treated, only two zones retract at the outer surfaces providing an integral inner cushion of material securely held by the outer two zones.
THIRD EXAMPLE Another interesting and novel product that may be formed comprises a 50/50 blend of denier 2 inch staple polyethylene terephthalate fibers, with 50% residual shrinkage fibers, and 6 denier alginate fibers, that will constitute a truly isotropic web of a depth of 1% inches. This web is passed through a needle loom with regular barbed needles so that the web receives about 450 penetrations per square inch on each surface. The needled web is then immersed in boiling water for two minutes so that theweb shrinks 26% in area at the same time the polysaccharide material is removed by the water so as to achieve a fineness not otherwise obtainable and increase the porosity of the web some 180%.
FOURTH EXAMPLE 7 A further interesting product, produced in accordance with this invention, comprises an isotropic web 30 (FIG. 3) prepared from two fibrous materials, one, a very coarse fiber 31 of 200 denier Dacron 61 with a 17% residual shrinkage and a fiber length of 1% inch staple; and another, very fine fiber 32 of micro denier beta glass with a fiber length of between 5 inch and 1% inch staple. These fibers may be processed through the three-zone machine disclosed by my patent mentioned above, the Dacron 61 polyester fiber being processed through the center section, and the glass fiber 22 through the two outer randomizing chambers. These fibers are processed simultaneously and are-atomized within the condensing chambers and deposited upon the pair of suction rolls or condensers of the machine, which are set so that the distance between these rolls corresponds to the web thickness of 1% inches. The fibers are carried in the air currents the width of the machine and are deposited upon these suction rolls or condensers in such a manner that the fibers build up into the roller gap and over their entire width in a three-zoned random arrangement throughout the structure so that the two outer surfaces contain a majority of glass fibers while the inner region contains the polyester fiber which protrudes into the outer areas of the upper and lower surfaces of the web. The fibers so positioned are intermingled in a random arrangement so that they lay at various angles, both horizontally and vertically to form a uniform three-dimensional structure in length, width and depth, there being individual polyester fibers extending transversely throughout the depth of the web to its upper and lower surfaces. Both fibrous materials contact each other at their various points of contact throughout the web, there being relatively few pairs of individual fibers which contact at more than one point; and each fiber of the web contacts a plurality of other fibers at spaced points which may be in the same or in different planes throughout the web, thereby tying the web into an intergral structure in length, width, and depth.
The web is then transported by a continuous conveyor to a needle punch loom and lightly needled on both sides so that the structure receives about penetrations per square inch, thereby increasing the specific gravity. The resulting web is then heat treated sufficiently to retract the shrinkable fibers. Upon shrinkage the polyester fibers buckle, curl, loop, and generally deform causing interlocking of the structure and providing coherence to the already integral web. A nonwoven so made has a three-zoned porous structure whose upper and lowersurfaces or zones are an arrangement of fine glass fibers while its inner core is largely constructed of the coarse fiber which in turn causes a difference in the air spaces or voids within the web such that the inner core will have the larger voids while these will become more numerous and smaller in size towards the outer surfaces; giving the structure a differential filtering characteristic.
FIFTH EXAMPLE By the way of another example: a blend 40 (FIG. 4) of 50% 80s wool 41 and 50% 6 denier polyesterfiber 42, both nonshrinkable, are processed through the outside chamber or zones of the machine disclosed in U.S. Pat. No. 3,535,187. A heat shrinkable premanufactured polyester or acrylic scrim or netting material is run through the center section so that a web is formed around the plastic netting within the center zone. The web so formed istransported to a needle loom where the web is lightly needled to give about 20 penetrations per square inch on both sides. The needled web is the exposed to dry heat at 280F for 5 minutes with the result that the polyester netting retracts causing the fiber blend trapped between the netting squares to fluff up and contract the fibers around the adjacent open square of the netting.
SIXTH EXAMPLE Yet another example is a blend as above but instead of a shrinkable netting material being encapsulated in the isotropic web, continuous shrinkable filaments are projected into the web in a completely random fashion so that after needling and the: required heat treatment the retracted filaments impart a curious surface effect such that random hills and valleys are formed.
SEVENTH EXAMPLE In another example the required web 50 (FIG. is produced, using the methods disclosed by my patent application above mentioned, where a polyvinyl alcohol fiber 51 known as Vinal VP-lOl was processed through one of the outer zones of the preferred ma chine to produce an outer zone 54 of approximately 2% oz. per sq. yard using a staple length mixture of 2% inch to 2 inches. Through the center section 55 a light weight web 52 of about 1% oz. per sq. yard is processed using Du Ponts Dacron 54 polyester fiber of 1 inch staple length and in the other outer zone 56 of the ma; chine a wool web 53 is manufactured at 3 oz. per sq. yard.
The resultant 3 ;zoned composite nonwoven is then transported to a two roll calender where one roll is heated and has an embossed pattern upon its surface and the other is a filled roll of 100% cotton fibers. The two rolls have different surface speeds. The web is pro cessed through the calender so that with the combina; tion of heat and pressure the nonwoven web is consoli dated into an integral matrix so that the retractable fi; bers are drawn together and are thrust upwards out of the plane of the web into a series of buckled ridges which are further extended with the use of the emboss; ing roll. The differential shrinkage of the matrix is 35% which gives the polyvinyl alcohol surface of the web firm, highly pronounced and deeply textured surface ridges which have an extremely good resemblance to the material known as Persian lamb since it consists of wool fibers and hard wearing polyester fibers organized into the tightly looped ridges of the skin like polyvinyl alcohol fibers, giving a flexible and fine grained sur; face.
The following examples are given to illustrate the em: bodiment of this invention when using composite fibers known as bicomponent and biconstituent or biconju gate.
The bicomponent fiber is a composite synthetic fiber formed by combining two or more components of the same type but with various characteristics. The bicon; stituent fiber is a composite synthetic fiber formed by combining at least two different compositions in conju; gation sometimes referred to as f Hetero filaments". The biconjugate fiber is a composite synthetic com: pound fiber formed in conjugation so that each of the two or more main constituents contain one or more dif; ferent polymers being a combination of the bicompo; nent and biconstituent types.
The nonwoven matrix is formed using the method as disclosed by my above mentioned patent, where the isotropic web 60 (FIG. 6) is prepared from 50% of bi component fibers 61 formed from two copolymers 62, 63 of acrylonitrile, which in their separate fiber form differ in shrinkage characteristics, 10% wool and 40% of the triacetate fiber fArnel. These fibers are of vari: ous lengths from about k inch to 2 inches and various deniers from 5 denier to 50 denier, blended in three groups, 66, 67, 68:
a&b. 20% of the bicomponent fiber and 20% of the Arnel fiber c. 10% of the bicomponent fiber and the wool fiber.
Blends (a&b) are processed through the outside ran; domizing chambers of the aforementioned machine while the third blend c is processed through the center section giving a truly isotropic web yet arranging the blends in three regions or zones so that the two outer zones are of the same configuration while the center zone is formed with the wool-synthetic blend which protrudes into the inner a eas of the upper and lower surfaces of the web. The fibers so positioned are intermingled in a random arrangement and lie at various an: gles both horizontally and vertically to form a uniform three-dimensional structure in length, width, and depth. The web so formed is passed through a needle loom with regular barbed needles so that the web receives about three hundred penetrations per square inch on each surface. The needled web is then exposed to heat designed to retract the bicomponent shrinkable fibers so that, because of the differing shrinkage char; acteristics, the fiber becomes highly crimped; and it buckles and loops into the spaces previously existing between adjacent fibers providing interfiber locking giving coherence of the already integral web, imparting texture, porosity and bulky softness.
EIGHTH EXAMPLE In a further instance, the manufacture of the fiber nonwoven is performed by vertical and horizontal de; position of continuous elements within a matrix of sta: ple fibers and combining the two constituents into one integrated structure. The materials used in this example were a biconstituent staple fiber known as Tricelon which is a combination of triacetate and ffNylon 6 in various deniers over the range 15 to 30 and in lengths of between 5% inch and 1% inches processed through the outer chambers of the aforementioned machine, while simultaneously continuous filaments are processed through the center section of the machine. These continuous filaments are a bicomponent fiber where two or more species of polyvinyl chloride, both or all of high syndiotactic index but differing in shrink; age characteristics, have been extruded under condi; tions that the polymers are not uniformly mixed in the filaments so that one component may be in the form of a sheath around a core of the other.
The fibers and filaments are processed simulta; neously and are intermingled in the condensing cham; ber air stream and deposited upon the pair of condens; ing cylinders which are so set that the distance between these suction rolls corresponds approximately to the desired thickness of the web, in this case 1 inch. The fibers and filaments are carried in the current of gas the width of the machine and deposited upon the suction rolls in such a manner that the fibers and filaments build up into the roller gap and over its entire width. Due to the turbulence of the air stream, the filaments begin to swing and oscillate back and forth in front of the condensing rolls. They are therefore seized in irreg; ular order, sometimes by one suction roll, sometimes by the other. As they advance between the roller gap they are embedded within the staple fibers. Since the rate of delivery of the continuous filaments is a multiple of the rate atwhich the matrix is formed, a short length of an individual filament is drawn to one side of the condenser suction area, and, due to the oscillation of the air stream carrying the fibers and filaments, an ad; jacent part of the same filament is seized in the next moment by the opposite suction roll and thus the fila ment is disposed in a horizontal orientation within the staple fiber st ucture. Since the air stream oscillates not only back and forth but also from side to side, the next moment another continuous filament is laid crosswide at a random angle to the previously deposited filament. This process is repeated in rapid succession over the entire fiber forming apparatus such that a random homogeneous fiber structure is produced between the staple fiber and continuous filaments in length, width, and depth. Thus, in this example my invention comprises advancing a plurality of continuous filaments along a path leading to the nip between spaced web forming condensing members so that the filaments move adjacent and onto said members while at the same time a matrix of the staple fiber is being formed. The gas streams within the condensing chamber are passed in a direction extending transversely to the continuous filaments and the gas streams have a component horizontal to the fiber and filament flow path, so that movement of the filaments, as they pass between the matrixforming cylinders, is disrupted, and individual filaments are caused to be dispersed in a side to side and back and forth random array within the staple fiber structure.
The bicomponent continuous filaments have been so engineered that the inner core has a higher differential shrinkage than that of the outer sheath, so that, when the nonwoven web is exposed to heat, the bicomporient polyvinyl chloride shrinks at different rates causing the continuous filament to crimp, buckle, and loop imparting to the structure improved texture, cover and body while having a full natural luxurious silky handle and great resilience, together with inherent fiber to fiber and filament integrated locking, imparting cohesion to the nonwoven web which is an important characteristic of this invention.
The webs formed as described above are mostly uncompressed yet self-sustaining and have considerable strength in their lateral, longitudinal, and transverse dimensions. They can be handled and, if required, spraybonded and are capable of being stitched and cut without the addition of any backing material. The web so formed may be stitched directly to woven fabrics to form a laminated fabric.
The webs have excellent air-retaining properties; and the insulating values therefore are high. Because of the random three-dimensional arrangement of the fibers, there are innumerable intercommunicating voids in the web and air can pass through that batt, but only at a relatively slow rate. The web can be compressed without the loss of loft provided the memory factor of the fiber to its recovery rate is good.
While the invention has been described particularly in connection with use of heat-shrinkable fibers, it will be understood that .fibers retractable by other media also may be used. For instance, when natural cellulosic fibers are employed, the shrinkage may be effected by treating the web with a sodium hydroxide solution of medium strength. Water-shrinkable fibers may also be used, and shrinkage effected by treating the web with water. Steam may be used also to effect shrinkage of fibers when they are susceptible to shrinkage with heat and water.
Because of the deeply textured surfaces ridges that may be produced with the process of the present invention, the fibrous surface of a web formed according to this invention may be ornamented with an in-depth colored design by printing such a design onto one or both surfaces of the matrix prior to effecting shrinkage of the web, so that when the retractable fibers in the web are shrunk, the colored surface will extend in depth down into the retracted and textured material.
Other modifications and applications of the invention will occur to those skilled in the art.
Having thus described my invention, What I claim is: 1. A process of making a non-woven fabric having a high degree of loft, which comprises aerodynamically depositing different types of fibers, some retractable and others non-retractable under the conditions of the process, simultaneously in an area where said fibers intiermingle to form a web having a random pattern of fiber arrangement throughout the entire length, breadth and depth of said web, systematically controlling the deposition of said fibers in said area to vary the predominance of one type of fiber over others of said different types of fibers in zones ar ranged depthwise of and essentially parallel with the major surfaces of said web, a zone delimited by a major face of said web being composed of predominantly different fibers than those of a zone immediately adjacent thereto, and to position said fibers so that some extend from one zone into another and some through all of the plurality of zones lying between the major surfaces of said web and, thereafter, subjecting said zoned web to a retracting operation to effect shrinkage of said retractable fibers and cause said retractable fibers to loop, buckle and curl and, thereby, lock adjacent fibers together at their points of contact and tie said web structure together from within without significantly elimiating interfiber voids.
2. The method of making a nonwoven fabric according to claim 1, wherein the retractable fibers are heatshrinkable, and the other fibers are non-heatshrinkable, and heat is applied to the web after its formation to retract the heat-shrinkable fibers.
3. The method of making a monwoven fabric according to claim 1, wherein the retractable fibers are natural cellulosic fibers and retraction is effected by treating the web with a sodium hydroxide solution of mercerizing strength.
4. The method of making a nonwoven fabric according to claim 1, wherein the retractable fibers are watershrinkable, and shrinkage is effected by treating the web with water.
5. The method of making a nonwoven fabric according to claim 1, wherein one major surface, at least, of the web is ornamented with an in-depth colored design by printing a colored design on said one surface, and causing the retractable fibers to shrink, whereby the colored surface extends in depth down into the retracted material.
6. A non-woven fiber web produced by the process of claim 1. I