US 3720554 A
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llnited States Patent [191 Stumpt 1March 13, 1973 METHOD OF MANUFACTURING HUGH-LOFT, NONWOVEN FABRIC  Inventor: RobertJ. Stumpf, Appleton, Wis.
 Assignee: Kimberly-Clark Neenah, Wis.
 Filed: Sept. 10, 1969  Appl. No.: 856,793
 US. Cl. ..l56/62.6,156/72,156/291, 161/84  Int. Cl ..B32b 17/04, D05c 15/00  Field of Search ..156/72, 62.4, 291, 62.6, 290, 156/471; 161/148, 84, 65; 128/156  References Cited UNITED STATES PATENTS 2,639,250 5/1953 Reinhardt ...l61/65 2,550,686 5/1951 Goldman ..l6l/66 3,047,444 7/1962 Harwood ..156/291 X 3,327,708 6/1967 Sokolowski ..156/290 X 3,316,136 4/1967 Pufahl ..156/291 X 3,214,323 10/1965 Russellet al t ..156/29] X 3,033,721 5/1962 Kalwaites ..l56/29l X 2,986,780 6/1961 Bletzinger ..156/291 Primary Examiner-Carl D. Quarforth Assistant Examiner- E. E. Lehmann Attorney-Wolfe, Hubbard, Leydig, Voit & Osann, Ltd.
 ABSTRACT A high-loft, nonwoven fabric with a substantially continuous backing layer of adhesive and multiplicity of fibers looped outwardly from the backing and a method of making the fabric by first embedding a web of fibers in a relatively thick open pattern of adhesive interconnected by relatively thin webs of the same adhesive, and then consolidating the adhesive into a substantially continuous backing layer while looping the fibers outwardly from the backing.
17 Claims, 12 Drawing Figures PATENTEDHAM cams SHEET 2 OF 3 FIGA FIG
PATENTEUHAR 1 3197s SHEET 3 BF 3 14%; rron/(m.
METHOD OF MANUFACTURING HIGH-LOFT, NONWOVEN FABRIC DESCRIPTION OF THE INVENTION materials have been produced both to replace convenl0 tional woven fabrics and also to create new markets in which woven fabrics have not yet become established. This is particularly true in the case of material for single-use and disposable products, such as: sanitary supplies, hospital garments, and disposable sheets and the like. For these applications the nonwoven fabric is generally made in continuous sheet form with one or more layers of staple length fibers and/or a reinforcing scrim structure adhesively bonded together or laminated between plies of other material such as cellulosic wadding and plastic sheeting. The fibers may be natural, synthetic or various blends and, of course, the particular composition of the nonwoven fabric is greatly influenced by its intended use.
Exemplary nonwoven fabrics are disclosed in U.S. Pat. Nos. 2,902,395; 3,047,444; 3,072,511 and 3,327,708 and copending applications Ser. No. 498,929 now abandoned and replaced by Ser. No. 79,287, filed Oct. 8, 1970; Ser. No. 551,605 now U.S. Pat. No. 3,553,064; Ser. No. 553,483 now U.S. Pat. No. 3,553,065; Ser. No. 769,959, filed Oct. 23, 1968 now abandoned and replaced by Ser. No. 31,225, filed Apr. 23, 1970; and Ser. No. 820,224, filed Apr. 29, 1969, all of which are assigned to the same assignee as the present application.
The applications Ser. Nos. 769,959, 31,225 and 820,224 identified above describe methods of making nonwoven materials by the simultaneous crimping and looping of a large number of synthetic fibers and the incorporation of the crimped fibers into a nonwoven fabric with the fibers extending outwardly from the backing material resulting in a high-loft fabric with a pleasing surface texture and appearance. The fibers are initially embedded in an open pattern of adhesive and then looped outwardly away from the adhesive in the open areas of the pattern, the adhesive being gathered during the looping operation to provide a consolidated or partially consolidated adhesive backing for the resulting fabric. In certain applications, it is desirable to have the adhesive backing only partially consolidated, as described in detail in the aforementioned application Ser. No. 820,224; in other applications the adhesive backing can be consolidated in various degrees and can even vary somewhat throughout the fabric. However, in certain applications, it is essential that the adhesive backing have a high degree of continuity, and that this continuity be achieved at relatively low gathering ratios to enable the material to be produced at relatively high production rates.
It is, therefore, a primary object of the present invention to provide an improved method of making a highloft, nonwoven fabric having a consolidated adhesive backing with improved continuity.
It is another important object of the invention to provide an improved method of the foregoing type which permits the production of improved high-loft, nonwoven fabrics at increased production rates. In this connection, a more specific object of the invention is to provide such an improved method which permits the production of such fabrics by the looping of fibers away from an open adhesive pattern at relatively low gathering ratios.
Other objects and advantages of the present invention will become more readily apparent upon reading the following detailed description and upon reference to the attached drawings in which:
FIG. 1 is a schematic side elevation of one form of apparatus which may be employed to practice the method of the present invention;
FIG. 2 is a fragmentary plan view somewhat simplified and exaggerated for the sake of clarity of illustration of an illustrative web of base material prepared by apparatus of FIG. 1 with portions of the material broken away to expose the various layers;
FIG. 3 is an enlarged schematic side elevation illustrating in somewhat idealized fashion the sequence of gathering and looping of individual fibers in the apparatus of FIG. 1;
FIGS. 4 and 5 are enlarged photographs of opposite sides of a nonwoven fabric made in accordance with the invention, FIG. 4 showing the adhesive side and FIG. 5 the fiber side;
FIGS. 6 and 7 are enlarge photographs of opposite sides of a nonwoven fabric made without using the improvement provided by the invention for comparative purposes, FIG. 6 showing the adhesive side and FIG. 7 the fiber side;
FIGS. 8 and 9 are enlarged photographs of opposite sides of another nonwoven fabric made in accordance with the invention, FIG. 8 showing the adhesive side and FIG. 9 the fiber side; and,
FIGS. 10-12 illustrate in plan view alternative adhesive patterns for the base web.
Turning now to the drawings, FIG. 1 schematically illustrates the apparatus for performing the method of the present invention in its preferred form. This apparatus includes a web forming section 10 and an adhesive compacting and fiber looping section 30. The web forming section 10 is generally similar to the apparatus disclosed in previously mentioned copending application Ser. No. 79,287 with certain modifications as disclosed in copending application Ser. No. 553,483, now U.S. Pat. No. 3,553,065. It should be appreciated that fiber webs made in accordance with methods disclosed in either of the above-mentioned applications are usable with the subsequent method steps of the present invention, as are carded webs and webs prepared by other processes, as will appear from the following.
As shown in FIG. 1, multiple slivers ll of textile fibers are drawn from their respective supply cans (not shown) into a draw frame 12 which comprises a series of pairs of grooved rolls 13, the rolls of each pair being driven by appropriate gearing well known in the art, at a peripheral rate of speed slightly faster than the rate of operation of the preceding pair. As the juxtaposed slivers pass through draw frame 12, the individual fibers are drafted and spread out to form a fiat striated web of substantially alined fibers as shown at 14. Web 14 is maintained on a supporting conveyor sheet 15 on the surface of which a patterned adhesive has been previously applied.
Different procedures have been used in preparing the base web. For example, textile length fibers may be processed through conventional cotton card machinery to produce a carded web for the base web. In such a carded web 50 to 70 percent of the fibers may be oriented substantially parallel with the machine direction; it has been found, however, that the most uniform product has been obtained with the method of the present invention by using base webs having a higher percentage of the fibers alined with the machine direction, such as a highly drafted web in which, as a result of the drafting process, 80 to 95 percent of the fibers may be alined with the machine direction. Still referring to FIG. 1, the conveyor sheet comprises an endless conveyor belt treated on at least its outer surface with a release agent. One example of such a belt comprises woven glass fiber with a surface coating of tetrafluoroethylene resin. Other release coatings are well known, and comprise such materials as silicones, fatty acid metal complexes, certain acrylic polymers, and the like. Heat resistant films of thin metal sheets treated with release agents may also be used as the carrier sheet.
Prior to the time the web 14 is picked up by the belt 15, the latter has imprinted on its release-treated surface a pattern of flexible thermoplastic adhesive such as is shown at 16 in FIG. 2. It is understood that the adhesive is actually on the underside of belt 15 which becomes the upper surface after passing around roll 17 whereby the adhesive pattern 16 directly contacts the fiber web 14. The pattern is shown as being visible in FIG. 2 only for illustrative purposes.
The belt 15 is fed around roll 17 at a speed slightly in excess of the delivery speed of the final pair of rolls 13 in order to maintain web 14 under slight tension whereby the individual highly drafted fibers are retained in their alined and tensioned condition. Drive rolls 18, 19 are rotated to drive belt 15 at a speed sufficient to maintain the proper tension on the web 14.
In the method shown for applying adhesive, the belt 15 is fed through a nip formed between a printing roll 20 and a back-up roll 21 maintained in very light pressure engagement therewith. The surface of printing roll 20 is provided with an intaglio pattern which picks up adhesive 22 from dip pan 23. Part of the adhesive thus applied is removed by a doctor blade 24 leaving only the intaglio patterned surface filled. The printing roll 20 then transfers this metered amount of adhesive in a preselected pattern to the underside of release coated belt 15. The pattern shown in FIG. 2 is in the form of an open diamond pattern of adhesive.
Since the surface of belt 15 is treated with a release coating, the adhesive remains substantially on the surface with no penetration therein and is preferably in a somewhat tacky condition. The printed belt is drawn from the printing nip around roll 17 positioned closely adjacent the output end of draw frame 12, and, as stated above, at a speed slightly in excess of the delivery speed of the last two rolls in the draw frame. The web 14 emerging from the draw frame 12 is deposited on the tacky adhesive 16 on belt 15 and held in tensioned engagement therewith by the adhesive and the above-mentioned speed differential. This continuous tension prevents the fibers in the web from losing their highly drafted and alined condition.
may be driven at a speed slower than that of the belt 15 i so that as each transverse segment of the adhesive pattern engages the belt 15, it is drawn away from the roll 20 at a speed greater than the surface speed of the roll 20, thereby drawing a thin film of adhesive between successive transverse segments of the adhesive pattern. Consequently, the adhesive pattern 16 formed on the belt 15 comprises a relatively thick open pattern of adhesive 160, corresponding to the pattern defined by the printing roll 20 but elongated due to the greater speed of the belt 15, and relatively thin webs 16b of the same adhesive interconnecting the relatively thick open pattern of adhesive. That is, the relatively thin webs of adhesive 16b bridge the spaces in the relatively thick open pattern of adhesive 16a.
Alternatively, the thin webs of adhesive 1612 may be formed by running the printing roll 20 at a speed greater than that of the transfer belt 15. In this case, the relatively thick open pattern of adhesive formed on the transfer belt 15 is a compressed version of the pattern defined by the printing roll 20, i.e., the machine direction dimensions of the pattern 16a on the web 15 are shorter than the corresponding dimensions of the pattern on the roll 20 due to the greater speed of the roll 20. However, the open spaces of the relatively thick pattern of adhesive 16a on the belt 15 are again bridged by the thin interconnecting webs of adhesive 16b formed by the differential in the speeds of the belt 15 and the roll 20.
An example of the web 14 formed by the method of the present invention on the apparatus l0'is shown in FIG. 2. As previously mentioned, a series of parallel and diagonally disposed lines of adhesive are printed in a criss-cross fashion on the belt 15 to form a relatively thick pattern of adhesive 16a in the configuration of interconnected diamonds, with the open spaces of the diamonds being bridged by the relatively thin adhesive web 16b. That is, the belt 15 carries a substantially continuous thin film of adhesive having raised portions forming an open pattern with the open spaces of the pattern bridged by intervening portions of the thin adhesive film. It should be appreciated, of course, that FIG. 2 is only intended to be illustrative and, while the lines representing the fibers are spaced apart for clarity, in practice the highly drafted fibers are vary close to one another.
Following the deposit of web 14 on the adhesive printed belt 15, the belt is drawn around a heated drum 29 where fusing and curing of the adhesive is substantially completed while the web 14 is maintained in firm contact therewith to bond the individual fibers. To insure effective heating and fusing of the adhesive, it is desirable that travel of the combined belt and web be around a substantial portion of the drum 29. The fibers of the web 14 are thus bonded together while retaining their highly-drafted and substantially alined condition in the particular pattern in which they were deposited on the pattern of the adhesive 16 printed on the belt 15.
The combined web 14 and belt 15 are preferably passed over a fly roll 29a and then a drive roll 19 which also serves as a cooling drum, to cure and set the adhesive. The bonded web 14 is stripped from the release coated surface of the belt 15 by the stripping roll 31 as the web leaves the cooling drum 19.
While various well-known adhesives may be employed in the foregoing process, advantages reside in the use of plastisols, which are colloidal dispersions of synthetic resins in a suitable organic ester plasticizer, and which under the influence of heat provide good binding power while remaining soft and flexible. While many adhesives of this type are known, those found particularly useful for incorporation in the product of this invention include vinyl chloride polymers, and copolymers of vinyl chloride with other vinyl resins, plasticized by organic phthalates, sebacates, or adipates. These provide a fast curing plastisol adhesive characterized by relatively low viscosity, low migration tendencies, and minimum volatility. Such adhesives remain soft and flexible after curing, and can be reactivated by subsequent heating.
It has been found that other adhesive systems may be employed in the process, such as organisols, utilizing resins such as the vinyl chloride polymers, and copolymers. Furthermore, other adhesives may be employed provided that they satisfy specified characteristics in the base web produced in the web forming stage, and in the finished fabric produced in the adhesive compacting and fiber looping stage. In general, such adhesives should be applicable to the base web 14 by procedures which will not disarrange the fibrous structure of the web; such adhesives should heat set at temperatures below the degradation temperature of the fibers in the base web 14 to secure bonding of the fibers to that adhesive; such adhesives should be reactivatable in the subsequent adhesive gathering and consolidation stage of the process; and such adhesives should form a flexible backing layer for the finished fabric and should strongly bond the fiber loops in place. For example, emulsions of thermoplastic resins such as acrylics and rubber-like compounds, illustratively ABS, have the requisite properties to serve as the bonding adhesive for the web 14.
In keeping with the present invention, the base material made as heretofore described and comprising a web of highly drafted fibers embedded in the adhesive pattern 16, is fed into the adhesive consolidating and fiber looping section 30 of the apparatus shown in FIG. 1. As illustrated, the web 14 while still under tension is fed around an idler roll 32 and onto the surface of a heated forming drum 37. In its preferred embodiment the drum 37 is made of metal with a highly polished chromium plated surface which is heated and maintained at a temperature of approximately 250 F. Also the web 14 is arranged to travel a substantial distance around the drum 37 with the pattern of adhesive 16 in contact with the heated drum surface. As the web 14 is fed onto the drum 37 the heat from the drum surface reactivates and softens the adhesive printed on the underside of the web causing it to become tacky and to adhere slightly to the drum surface thereby maintaining the web under constant tension. The drum temperature, however, is maintained below the melting point of the adhesive to prevent dispersion of the adhesive into the fibers of the web.
The web 14 of fibers and softened adhesive is reformed by the cooperative action of the drum 37 and a gathering blade 38 having a flat edge 39. The blade edge 39 operates to consolidate the adhesive pattern 16 into a substantially continuous backing layer of adhesive while simultaneously looping the fibers of the web outwardly from between the open spaces in the original adhesive pattern. The reformed and consolidated material 40 then leaves the blade edge 39 and onto a flat take-off surface 41 and a discharge conveyor 42.
Turning now to FIG. 3, the method of making the high-loft, nonwoven fabric 40 will be explained in greater detail in connection with an illustrative sequence of the gathering and looping of a single fiber of the web 14 and the consolidation of its original points of adhesive attachment in the raised adhesive pattern 16a. As seen in FIG. 3, the fiber has a portion P which extends across the open space of the relatively thick diamond pattern of adhesive 16a, from point A to point B where it is embedded in the adhesive. The series of views in FIG. 3 illustrates how the portion P of the fiber is formed into a loop simultaneously with the consolidation of the adhesive 16 to form a substantially continuous adhesive backing. When Point A being carried around the heated drum 37 impinges against the gathering blade edge 39, its forward motion is halted and it is scraped along the surface of the drum. Point B continues to advance with the drum surface since due to its softened and tacky condition it adheres to the smooth drum surface.
As point B advances relative to point A, the portion P of the fiber between points A and B is caused to bow outwardly from the drum surface. At the same time, the relatively thin adhesive web w that bridges the open space between points A and B collects on the upstream side of point A, thereby gradually filling in the space between the points A and B, i.e., gradually increasing the thickness of adhesive in the web areas 16b toward the level of adhesive in the raised areas 16a. Finally, point B overtakes point A and these points of adhesive are substantially consolidated along with the adhesive gathered from the interconnecting web w. In the meantime, fiber portion P has been looped outwardly from the drum surface. As additional adhesive points C, D, etc., travel around the drum 37 and impinge against the gathering blade edge 39, successive pairs of adhesive points, B-C, C-D, etc. and the corresponding interconnecting webs W1, W2, etc. are consolidated simultaneously with the looping of their respective intermediate fiber portions P1, P2, etc. This occurs simultaneously at all points across the web at the blade edge producing a substantially continuous layer of adhesive from which extends the multiplicity of loops formed by the fibers of the base web. The consolidated layer of adhesive is carried away from the blade edge along the take-off surface 41 and provides a backing layer for the outwardly looped fibers, thus producing the fabric 40.
It has been found that the relatively thin webs of adhesive 16b formed by running the transfer belt 15 and the printing roll 20 at different speeds produces a significant improvement in the continuity of the adhesive backing in the final product, and yet the adhesive webs surprisingly do not interfere with the desired looping of the individual fibers in the web 14. Although it is not intended to limit this aspect of the invention to any specific theory, it is believed that the fiber portions P,
P1, P2, etc., are suspended between two or more successive points A-B, B-C, C-D, etc., of the relatively thick open pattern of adhesive 16a, i.e., the fiber portions P are held slightly spaced away from the thin adhesive webs or membranes 16b by the relatively thick or raised adhesive pattern 16a. Consequently, as can be seen from the sequential representations in FIG. 3, the thin adhesive webs w, W1, W2, etc. do not interfere with the looping of the fiber portions P by the gathering blade 38. The thin adhesive webs 16b are gradually consolidated as successive segments of the thick adhesive pattern 16a approach each other during the looping of the fiber portions P, but the looping of the fiber portions P away from the adhesive webs 16b prevents the fibers from becoming embedded in the thin webs. As successive transverse segments of the thick adhesive pattern continue to approach each other, the consolidation thereof is enhanced by the consolidation of the thin adhesive webs between the successive thick transverse segments, thereby producing an adhesive backing of significantly improved continuity.
The improved continuity of the adhesive backing achieved by the adhesive pattern illustrated in FIGS. 2 and 3 is ofsignificant value when the final product is to be used in applications requiring improved integrity of the material, or where the appearance of the material backing is important. Furthermore, perhaps an even more significant advantage of this aspect of the invention is that a backing of improved continuity can be produced at relatively low gathering ratios, e.g., ratios of :1 or lower, so that relatively high production rates can be achieved.
In one example of the particular process described above and illustrated in FIGS. 1-3, a base web of polyester fiber having an average fiber length of 3 inches and a weight of 6.5 grams/sq. yd. was used with a polyvinyl chloride plastisol adhesive, a preheat drum temperature of 301 F., a heating drum temperature of 248 F., and a gathering blade angle of 34. The adhesive was applied to the transfer belt from a diamondpatterned printing roll driven at a surface velocity of 60 ft./min. with the transfer belt running at a velocity of 54 ft./min., and the weight of the resulting fiber-adhesive composite on the transfer belt was 14.0 grams/sq. yd. The material produced at a gathering ratio of 17:1 is shown in FIGS. 4 and 5, FIG. 4 showing the fiber adhesive side and FIG. 5 showing the fiber side of the material.
The above process was repeated using exactly the same conditions, but with the transfer belt and the printing roll running at exactly the same speeds (54 ft./min.) so that the interconnecting adhesive webs were not produced. The weight of the fiber-adhesive composite on the transfer belt in this case was 13.3 grams/sq. yd. The resulting material is shown in FIGS. 6 and 7, FIG. 6 showing the adhesive side and FIG. 7 showing the fiber side. Comparison of FIGS. 4 and 5 with FIGS. 6 and 7, respectively, reveals a dramatic difference in the two materials, particularly in the continuity and integrity of the adhesive backing.
In another example of the invention, the process described above was repeated with the transfer belt running at a velocity of 53 ft./min. and the printing roll driven at a velocity of 43.5 ft./min. The weight of the fiber-adhesive composite on the transfer belt in this case was 12.9 grams/sq. yd. The resulting material is shown in FIGS. 8 and 9, FIG. 8 showing the adhesive side and FIG. 9 the fiber side. It can be seen that this material also represents a substantial improvement over the material of FIGS. 6 and 7.
It has been found that as each fiber portion P loops outwardly from the drum surface, it turns, reaching a position in the fabric 40 generally perpendicular to the direction of the original alinement of fiber portion P. Thus, the fiber loops arrange themselves so that the plane of each loop is substantially normal to the original fiber alinement shown in FIG. 2. The reason for the loop twisting as it is formed may be explained by this observation: if two spaced points of a single fiber not in a web are brought together, it has been observed that the fiber will form a loop, and as the loop is formed it twists towards a position of a minimum internal stress, turning through an angle approaching In carrying out the method of the invention, because of the great number of fibers in the web and their proximity to one another, each fiber loop engages the neighboring fiber loops with the result that all the loops are blocked from turning beyond a plane substantially normal to the machine direction, and are constrained in that position by the interference between the loops. In practice, of course, actual direction and degree of loop twist depend upon the characteristics of the fibers in the original web 14.
The heights of the fiber loops vary throughout the fabric according to the spacing between the points of attachment of each fiber to the raised open adhesive pattern in the base web. This results in a dense fabric with the lower loops supporting and filling around the higher loops and the top surface of the fabric being formed by the tops of the higher loops. The appearance of a fabric so constructed depends not only on the height of the fiber loops but also on the type and denier of the fibers used in the base web, and one of the features of the invention is that the depth of the fabric and the evenness of the surface may be varied by adjusting the control parameters, as will be explained below. In general, it may be said that for moderate and low-loft materials which have been produced with the method of this invention, the fabric appears to have a uniform thickness with a somewhat uneven surface texture. With very deep high-loft fabrics, particularly when made from flexible, low denier fibers, the higher loops tend to lay one over the other providing a very soft, napped, fuzzy, fibrous surface. For usages where a more uniform surface texture is desired, moderate and high-loft fabrics made according to this invention may be sheared at some intermediate height. In such cases a higher percentage of the fibers will extend outwardly from the backing layer fully to the finished surface of the fabric and the fabric then has a cut-pile appearance.
The various parameters that affect adhesive consolidation and fiber looping in the illustrative process are described in detail in the aforementioned applications Ser. Nos. 769,959, 31,225 and 820,224, and reference may be had thereto for a complete understanding of the effect of variations in the different parameters such as the blade-edge angle and the like. One parameter of interest in connection with the present invention is the adhesive pattern applied to the fibers in the formation of the base web. In the examples described above, the adhesive was applied in the form of diagonal lines, criss-crossed to provide an open diamond pattern with the size of the opening in the diamond in the machine direction being less than the lengths of the fibers used for the base webs. Other adhesive patterns which may be used include unevenly spaced lines of adhesive such as evenly spaced diagonal lines 50 extending across the web, as shown in FIG. 10 to produce a fabric with loops of uniform height. The spacing between the lines of adhesive may be increased or decreased to obtain a higher or a lower pile height, as desired. Another adhesive pattern which produces loops of uniform height is evenly spaced transverse zig zag lines 51 as shown in FIG. 1 1. Similar results may be achieved with a brick pattern as shown in FIG. 12. With all such patterns, if broken lines of adhesive are utilized as in FIG. 12, the obtain looping, the gaps in the lines of adhesive 86 should be staggered such that the web elements longitudinally span the spaces between the adhesive lines and are securely attached to the adhesive.
When the spacing of points of attachment of the fibers to the adhesive varies regularly over the area of the base web as, for example, whenan open diamond pattern of adhesive is used, the loops in the finished fabric will vary in height in a regular manner to provide a uniformly varying surface having a textured appearance. When, on the other hand, an open pattern of adhesive is used in which in the cross direction of the base web the lines of adhesive are parallel, or evenly spaced it will be seen that the spacing of points of attachment of the elements to the adhesive will be uniform over the total area of the fabric, and the loops in the finished fabric will be of uniform height to provide a more even surface. The appearance of such a surface will, of course, be affected by the characteristics of the elements which form the loops. Thus, where the elements are yarn or heavy strands of fibers, the loops will be clearly visible, while where the elements are small diameter, flexible fibers, the surface will have a fibrous appearance, the fiber looping being less evident.
The blade edge angle, i.e., the angle that the blade edge forms with a line tangent to the surface of the drum 37, is another parameter that can be adjusted to control the product characteristics. As a result of trying different blade edge angles, it has been determined that the preferred blade edge angle is between about 17 and about 34. With blades having edge angles within this preferred range, fabrics have been produced with a uniformly consolidated adhesive backing layer having no fissures or gaps and with a dense, regular mass of loops that provide a textured, somewhat uneven surface. With blades having edge angles less than l7, difficulty has been experienced in obtaining a uniformly consolidated, adhesive backing layer. This appears to be the result of insufficient relief between the blade edge and the drum surface for the fabric to flow evenly and smoothly off the drum surface as the result of the action of the blade, which produces varying degrees of consolidation of the adhesive and a non-uniform layer with fissures and gaps and scattered areas where the looping is irregular tending to spoil the surface appearance of the fabric. With blades having edge angles substantially above 34, both the problem of nonuniform adhesive consolidation and poor loop formation has been experienced. There is also a tendency as the angle of the blade edge is increased substantially above 34 for the fabric to be formed with pronounced ridges, which may be undesirable in the finished product.
Still another control parameter is the location of the take-away surface 41. The preferred location of the take-away surface 41 is tight against the blade 38 and even with the outside corner of the blade. It has been found that by lowering the take-away surface 41 from its preferred location, the structure of the fabric will be drastically affected, e.g., the bulk of the fabric may be increased substantially by lowering the take-away surface 41. The effect of lowering the surface is somewhat similar to the effect from using a blade with an edge angle substantially above the preferred range in that pronounced ridges are also produced in the fabric, thereby increasing its bulk. A further related parameter that affects the gathering function of the blade is the take-away speed of the fabric from the blade edge. With blade 38 having an edge angle within the preferred range, and a take-away surface at the preferred location, the take-away speed is desirably regulated to remove the newly formed fabric at the rate at which it is being formed, and it has been found that under these conditions the normal ratio of the surface speed of the heating drum 37 to the take-away speed will be about 10:1. As mentioned previously, the improved continuity of the adhesive backing provided by the present invention permits the use of relatively low gathering ratios, and correspondingly higher production rates. By increasing the ratio up to, for example, 15:1, by slowing down the fabric take-away speed, more uniform adhesive consolidation has been obtained while the mass of the fiber loops is made somewhat more dense, so that a fabric with a higher weight has been produced. By increasing the fabric take-away speed, such that the fabric is not allowed to gather at the blade edge, the fabric will be drawn or extended while the adhesive layer is still in a plastic condition, thereby expanding the adhesive layer, thinning the fabric pile and reducing the weight of the finished material. A number of different fibers may be used in the method of the invention, including natural fibers and various synthetic fibers and blends thereof. For example, acrylic, olefin, and polyester fibers have been used, and it is within the contemplation of the invention to use any or all of these fibers by themselves or in blends, as well as the natural fibers, acetate, nylon and other synthetic fibers in staple length or in monofilament form. Moreover, not only highly drafted webs and carded webs of staple length fibers may be used for the base web but also garneted and air laid webs of such fibers as well as directly laid alined webs of monofilament. It has been noted however, that when webs such as carded webs are used for the base web in which an important proportion of the fibers are randomly oriented, those fibers not alined with the machine direction appear to interfere with the loop production by the gathering blade. The most regular formation of loops with the loops turned normal to the machine direction has been produced with those base webs having the highest proportion of fibers alined with the machine direction, as, for example, the highly drafted webs made with the apparatus illustrated in FIG. 1.
it is also contemplated that flexible threads, yarns or strands may be used for forming a base web. To obtain regular loops of such elements in the finished material, it is clear that substantially all such elements should be parallel and extending longitudinally of the web, for loop formation will be interfered with by those elements that substantially depart from such longitudinal alinement. It is also recognized that to produce a material in accordance with the invention, the elements should be sufficiently flexible to allow the loops to form and to twist normal to the machine direction while being formed, under the action of the adhesive consolidating and gathering blade. Thus, neither stiff strands which do not loop under the action of the gathering blade, nor multiple strand yarns in which the lay of the strands opposes the tendency of the loops while being formed to twist under the action of the blade, will satisfactorily serve as elements of the base web when it is desired to produce a fabric fully in accordance with the invention. The temperature of the forming drum is determined by the adhesive utilized, and is typically a lower temperature than the temperature of the first stage adhesive heating drum 29 sufficient to reactivate the adhesive and make it tacky, so that it will adhere to the drum 37, but a lower temperature than was required at the heating drum 29 to fuse the polyvinyl or other resin of the adhesive and thereby secure an adequate bond to the fibers. The forming drum temperature will depend on the particular adhesive used as well as the operating surface speed of the drum and the distance that the web is maintained in contact with the drum. The degree of heat set that can be obtained depends on the softening temperature of the thermoplastic fibers in the web. Thermoplastic fibers which are heated to their softening temperature will be heat set into the looped or crimped shape that is imparted to such fibers by the gathering blade. The pile of the finished fabric embodying such heat set fibers has resiliency and resists crushing, so that where these properties are desired, the thermoplastic fibers for the base web should be selected with consideration of their softening temperature and the operating temperature of the forming drum. It has also been observed that certain types of thermoplastic fibers will be shrunk by exposure to the heat of the heating drum 29 or the forming drum 37. Fiber shrinkage will affect the size of the loops formed by such fibers and, therefore, the appearance of the finished material. Fiber shrinkability at the operating temperature of the heating and forming drums 29 and 37 must, therefore, also be considered in selecting the fiber for the base web.
I claim as my invention:
1. A method for producing a high-loft, nonwoven fabric which comprises forming a thick open pattern of adhesive on a continuously moving supporting surface with the thick open pattern of adhesive being interconnected by thin webs of the same adhesive, preparing a web including flexible fibers extending longitudinally of the web, bonding the flexible fibers in said web to said thick open pattern of adhesive while said adhesive is in a tacky state so that it adheres to said surface with said fibers spanning said thin webs of the same adhesive within said thick open pattern, carrying said web on said surface to the edge of a gathering blade, looping the portions of said fibers spanning said thin webs of adhesive outwardly from said surface and consolidating said thin webs of adhesive and the adjacent portions of said thick open adhesive pattern into a substantially continuous adhesive backing for said outwardly looped fibers by impinging said fibers and adhesive against the edge of said gathering blade, and conveying said adhesive backing and outwardly looped fibers away from said surface and said gathering blade.
2. A method for producing a high-loft, nonwoven fabric as set forth in claim 1 wherein said web of flexible longitudinally extending fibers bonded in said thick open pattern of adhesive is formed by applying said thick open pattern of adhesive to a continuously moving transfer belt and then bringing thc adhesive-containing side of said transfer belt into engagement with a fibrous web.
3. A method for producing a high-loft, nonwoven fabric as set forth in claim 1 wherein said web of flexible longitudinally extending fibers bonded in said thick open pattern of adhesive is formed by continuously advancing a transfer belt over a rotating printing roll containing an open pattern of adhesive to transfer the adhesive from said roll to said belt, and then bringing the adhesive-containing side of said transfer belt into engagement with a fibrous web to transfer the adhesive from said belt to said web.
4. A method for producing a high-loft, nonwoven fabric as set forth in claim 3 wherein said transfer belt and said printing roll are driven at different velocities to draw said thin webs of adhesive across the open spaces of said thick open pattern of adhesive transferred from said roll to said belt.
5. A method for producing a high-loft, nonwoven fabric as set forth in claim 4 wherein said transfer belt is driven at a velocity greater than the surface velocity of said printing roll to draw said thin webs of adhesive across the open spaces of said thick open pattern of adhesive transferred from said roll to said belt.
6. A method for producing a high-loft, nonwoven fabric as set forth in claim 4 wherein said printing roll is driven at a surface velocity greater than the velocity of said transfer belt to draw said thin webs of adhesive across the open spaces of said thick open pattern of adhesive transferred from said roll to said belt.
7. A method for producing a high-loft, nonwoven fabric as set forth in claim 1 wherein said relatively thin webs of adhesive are spaced away from said flexible fibers in the open spaces of said thick open pattern of adhesive prior to the consolidation of said adhesive.
8. A method for producing a high-loft, nonwoven fabric as set forth in claim 1 wherein said flexible longitudinally extending fibers are bonded to said thick open pattern of adhesive, and said thin webs of the same adhesive bridge the open spaces of said open pattern without bonding said flexible fibers, said thin webs of adhesive being consolidated along with said thick open pattern of adhesive upon impingement of said fibers and softened adhesive against the edge of said relatively moving gathering blade.
9. A method for producing a high-loft, nonwoven fabric which comprises coating a continuously moving supporting surface with a substantially continuous thin film of adhesive having raised portions of said adhesive extending away from said surface in an open pattern, the open spaces of said open pattern being bridged by intervening portions of said thin film, preparing a web including flexible fibers extending longitudinally of the web, bonding the flexible fibers in said web to said thick open pattern of adhesive while said adhesive is in a tacky state so that it adheres to said surface with said fibers spanning said thin webs of the same adhesive within said thick open pattern, carrying said web on said surface to the edge of a gathering blade, looping the portions of said fibers extending between said raised portions of adhesive outwardly from said surface and consolidating successive transverse segments of said raised portions of adhesive and said intervening portions of said thin film of adhesive into a substantially continuous, adhesive backing for said outwardly looped fibers by impinging said fibers and adhesive against the edge of said gathering blade, and conveying said adhesive backing and outwardly looped fibers away from said surface and said gathering blade.
10. A method for producing a high-loft, nonwoven fabric which comprises providing a driven printing roll having an open pattern of liquid adhesive on the surface thereof, advancing a continuously moving supporting surface over said printing roll to apply said open pattern of liquid adhesive to said supporting surface, said printing roll and said supporting surface being driven at different speeds so as to draw thin webs of said adhesive across the open spaces of said open pattern of adhesive so that the adhesive applied to said supporting surface includes a thick open pattern of adhesive interconnected by said thin webs of the same adhesive, preparing a web including flexible fibers extending longitudinally of the web, bonding the flexible fibers in said web to said thick open pattern of adhesive while said adhesive is in a tacky state so that it adheres to said surface with said fibers spanning said thin webs of the same adhesive within said thick open pattern, carrying said web on said surface to the edge of a gathering blade, looping the portions of said fibers spanning said thin webs of adhesive outwardly from said surface and consolidating said thin webs of adhesive and the adjacent portions of said thick open adhesive pattern into a substantially continuous adhesive backing for said outwardly looped fibers by impinging said fibers and adhesive against the edge of said gathering blade, and conveying said adhesive backing and outwardly looped fibers away from said surface and said gathering blade.
11. A method for producing a high-loft, nonwoven fabric as set forth in claim 10 wherein said printing roll is driven at a speed greater than the speed of said continuously moving supporting surface.
12. A method for producing a high-loft, nonwoven fabric as set forth in claim 10 wherein said supporting surface is advanced at a speed greater than the surface speed of said printing roll.
13. A method for producing a high-loft, nonwoven fabric with a surface oflooped flexible elements, from a web formed of a multiplicity of flexible, extended elements, comprising the steps of:
embedding said web of flexible, extended elements at spaced points on said elements in a substantially continuous thin film of adhesive,
activating the adhesive film to a softened,
gathering the softened adhesive film while outwardly looping the portions of said elements between said points, to form 1. a flexible, substantially continuous, gathered adhesive backing layer, and
ii. a multiplicity of loops providing the fabric surface with the ends of each loop embedded in said adhesive backing layer; and
setting the gathered adhesive backing layer.
14. A method according to claim 13 for providing a high-loft, nonwoven fabric, in which said flexible, extended elements are selected from the group consisting of natural fibers, synthetic fibers, and blends of natural and synthetic fibers, in staple length and monofilament form, and threads, yarns and strands.
15. A method according to claim 13 for producing a high-loft, nonwoven fabric wherein the film of adhesive in which the web of elements is embedded, is in the form of an open pattern of adhesive interconnected by webs of the same adhesive.
16. A method according to claim 15 for producing a high-loft, nonwoven fabric, wherein said continuous thin film of adhesive has raised portions forming an open pattern with the open spaces of said pattern bridged by intervening portions of a thin adhesive film.
17. A method according to claim 13 for producing a high-loft, nonwoven fabric, wherein the film of adhesive in which the web of elements is embedded, is in the form of an adhesive pattern.