US 3575782 A
Description (OCR text may contain errors)
April 2, 3971 P. E. HANSEN 3,575,732
ELASTIC SHIRRED WEB PRODUCT Filed May 19, 1967 INVENTOR.
840; f. fi /v55 BY M F W Unite States 3,575,782 ELASTIC SHIRRED WEB PRODUCT Paul E. Hansen, North St. Paul, Minn, assignor to Minnesota Mining and Manufacturing Company, St. Paul, Minn.
Filed May 19, 1967, Ser. No. 639,689 Int. Cl. D8411 5/04 U.S. Cl. 161141 Claims ABSTRACT OF THE DISCLOSURE A covering material consists of partially extended spaced aligned elastic yarns sealed between two thin porous gathered non-woven fibrous webs, or between a web and a non-porous film, by means of a soft flexible polymeric coherent binder.
This invention relates to elastic web or sheet material and to methods of making the same. Elastic shirred or corrugated fabrics are described, as early as U.S. Pat. No. 22,038 as consisting of threads of india rubber stretched and bonded between two laminae of cloth and then permitted to retract thereby causing puckering or gathering of the fabric to provide the desired shirred effect. The rubber yans aeetaoinshdluwCMFM sirred effect. The rubber yarns are substantially completely retracted. The sheet is heavy and bulky and is only moderately porous. Cut edges must be prevented from raveling or separation by folding and cementing.
The present invention in one important aspect likewise involves the formation of a shirred or puckered fabriclike web or sheet material but distinguishes over the products of the prior art in a number of significant and unanticipated respects. The sheet is extremely thin yet surprisingly strong. Despite the high proportion of polymeric binder, the sheet remains high in porosity. It may be stretched sufficiently to overcome all puckering by simple hand pulling, and will then retract to its initial length and appearance upon release of tension. Surprisingly, it may be caused to undergo significant additional shrinkage under appropriate treatment, yet is dimensionally unchanged under normal storage and use conditions.
In one preferred form the product of the invention has utility as a self-adherent porous elastic bandage. In the usual widths of six inches or less the strip is easily stretched to any degree desired up to the full extensibility of the material, and when then wound about an injured member is found to conform fully and to be self-adherent. In applying a knee or ankle bandage, for example, the strip may be placed under minimum holding tension at the extremities and under much greater tension along the sprained or otherwise injured central section of the affected member. The bandage remains under tension 7 and firmly in place, yet does not adhere to the skin and is easily removed by stripping when desired.
In another form the product is non-adherent at noraml temperatures but may be sealed to itself under heat and pressure, thereby making possible the simplified preparation of shaped elastic coverings such for example as gloves, caps, or bags.
In the drawing,
FIG. 1 is a schematic representation showing the manufacture of the elastic sheet material, and
3,575,782 Patented Apr. 20, 1971 FIG. 2 is a representation in plan view of a portion of the product.
As shown in FIG. 1, elastic yarns 10 from a beam 11 are unwound under tension provided by a brake 12 and through a comb 14. Thin non-woven fibrous webs 15 and 17, from supply drums 16 and 18 respectively or di rectly from the forming machine if desired, are brought into contact with the yarns and with each other between squeeze rolls 19 and 20, the latter dipping into a pan 21 containing a fiuid binder mixture 22. The composite web passes directly into a drying oven 24 and thence between pull drums 25 and 26. The web next passes around idler roll 27, between heating platens 28 and 29, around pull drum 30 and idler roll 31, and is wound up to form stock roll 32.
Squeeze rolls 19 and rotate at a considerably greater surface speed than does beam 11, and the yarns 10 are accordingly stretched a corresponding amount. This stretch is maintained by operating pull drums and 26 and turn-around drum 27 at the same or slightly higher speed compared with rollers 19 and 20. Pull drum and windup drum 32, however, are again operated at a slower speed to permit shrinkage of the web as it passes between the heater plates 28 and 29. The composite web 34, which is smooth as it reaches the roll 27, becomes increasingly puckered or shirred as it passes through the heating zone, the result being further indicated in FIG. 2.
In an illustrative example, the yarns 10 are 820 denier Lycra spandex or linear polyurethane monofil'aments spaced six yarns per inch of width and each of webs 15 and 16 consists of 1%. denier staple rayon fibers of inch length, formed into a non-woven batt weighing approximately one-fourth ounce per square yard. Centrifuged natural rubber latex at 60% concentration serves as the fluid binder mixture 22, and the amount retained in the composite web is sufficient nearly to double the weight of the web after drying. The beam 11 has a surface speed of 7 feet per minute, whereas, the speed at rolls 19 and 20 is 30 ft./min., that at rolls 25, 26 and 27 is 32 ft./min., and that at rolls 30 and 32 is 20 ft./min.
The heat supplied by the platens 28 and 29 is sufficient to cause considerable fuming of the sheet material and to relax the structure sufficiently to permit the elastomeric yarns to retract and produce the desired degree of puckering or shirring as controlled by the speed of the pull drum 30. The temperature may be regulated by adjusting both the energy input to the platens and the distance between the platens and the web. In a typical installation for producing a web having a finished width of 32 inches before trimming, the electrically heated platens are each 15 inches high and inches wide, and are spaced between six and nine inches from the web. A thermometer placed adjacent the web between the platens registers about 200- 250 F. The duration of the heat treatment may be regulated, for a given length of platen, by adjusting the speed of travel of the web, sufficient time being provided to permit retraction of the web to the desired degree. The platens are maintained at a temperature sufficient to keep the web taut during the shrinking operation between rolls 27 and 30 at the speed indicated but not so high as to cause deterioration of the web as evidenced by excessive fuming and discoloration thereof. For most purposes the length of the relaxed web after retraction will be within the range of about one-third to about two-thirds the fully extended length. The elastic yarns are initially stretched to a length of about three to five times their fully relaxed length, and are permitted to relax only partially during the puckering step. Nevertheless the shirred product is dimensionally stable, the heat treatment serving to provide an effective degree of heat-setting or stabilizing, and neither shrinks nor expands when allowed to stand at normal temperatures and under no external stress; and it returns to such dimensions when first stretched and then permitted to retract. It is possible further to shrink the web, for example by at least an additional ten percent in the product made as above described, by further heating it sufficiently under stress-free or limited-stress conditions; but the structure obtained by shrinking to Within the approximate limits heretofore stated is found to provide a balance of properties best suited to the utility of the material for the purposes indicated and is greatly preferred. Thus the product when designed as an elastic self-adhering bandage may be resiliently extensible to a length of about 12 inches from a relaxed length of six or seven inches, whereas a product destined for the preparation of a cap, bowl cover, arm band, or similar article may be elastically stretched to as much as 20 or 21 inches from a relaxed length of seven inches.
In other illustrative examples the elastic yarn has been 1120 denier spandex elastic yarn or No. 70 rubber yarn, and the number of yarns has varied from two to eight per inch of width at the comb 40 and up to about 40% by weight of the total weight of the web, although preferably not exceeding about 8 ot 10 percent.
The thin fibrous matts are conveniently prepared on a garnetting machine or preferably on a Rando-Webber machine. Matts of polyester or rayon staple fibers or mixtures are preferred. The fibers are desirably of about 1 /2 denier and about to 1 /2 inch in length, and the matt is about A to /2 oz./sq. yd. or about 5-10 lb. per 320 sq. yd. These very thin matts are fragile and flimsy, but show surprising strength when combined in composite structures of the type and in the manner hereinabove indicated. Where the flimsiness of the untreated matt presents inordinate difficulties in handling, the matt as first formed may be reinforced by lightly treating with a compatible bonding agent. As an example, the reinforced matt may consist of 90 parts by weight of viscose rayon fibers and ten parts of polyethyl acrylate, the latter being applied at the forming machine by saturating with a dilute emulsion of the polymer, removing the excess between squeeze rolls, and drying in an oven.
Concentrated natural rubber latex is preferred as the impregnating and bonding or unifying medium where coherency between layers of the sheet product is desired. Other elastomers or blends of elastomers having similar properties may be used. The dried rubbery residue, although presenting a slightly tacky feel, does not adhere to the skin, but coherently bonds to itself with sufiicient force to hold the contacting layers together against reasonably high shearing stresses. For those applications in which bonding is to be achieved only at elevated temperatures, polymers such as polyethyl acrylate are substituted for the self-tacky rubbery polymers, a suitable commercially available material being Rhoplex Bl5 polyethyl acrylate dispersion. These impregnating and bonding materials may be used without further modification, but will ordinarily be blended with pigments or other visual modifiers. For products which are to be used as surgical wrappings or the like it is usually preferred to incorporate pigments of the type and in the amount required to produce a flesh color in the sheet product, an example being a mixture of 50 grams each of Kohnstamm Cosmetic Umber No. 1985 and Raw Sienna No. 2673 pigments in each ten gallons of the liquid latex. For decorative applications other color bodies may be substituted as desired.
An example of a sheet having particular utility as a c0- hesive bandage is made with four ends of 1120 denier spandex elastic yarn per inch of width, sandwiched between two non-woven fibrous webs each weighing A ounce per sq. yd. and containing of 1 /2 denier inch polyester fibers and 10% of polyethyl acrylate, the whole weighing 15 lbs./ 320 sq. yds. and being impregnated and held together with an additional 25 lbs/320 sq. yds. of lightly pigmented natural rubber. The sheet in shirred or puckered form has an apparent caliper of 20 mils, a yarn count of slightly more than five ends per inch width, and weighs lbs./ 320 sq. yds., whereas in fully stretched or extended form the caliper is 7 mils, the thickness in both instances being determined with a papermakers caliper having a pressure foot and anvil onehalf inch in diameter. The porosity reading, ice. the time required to pass 400 ml. of air through a sample one square inch in area in the Model 4118 Gurley Densometer, is six seconds.
For many applications a nonporous structure is preferred. Such materials, having the desirable stretchiness and retractability of the products hereinabove described but in addition being non-porous and water-repellent, and being capable of being coherently bonded to themselves under pressure applied either at room temperature or at elevated temperature, are particularly useful as waterresistant wrapping or bandaging materials or in the manufacture of elastic waterproof coverings such as bowl covers or shower caps. The substitution, for one of the porous webs 15 or 16, of a thin flexible film or foil, of which 0.4 mil polyethylene film or thin bright aluminum foil are illustrative, results in non-porous elastic webs having these desirable properties. The use of brightly colored, patterned, or reflective films or foils for such purposes provides a particularly attractive decorative elastic sheet material.
What is claimed is as follows:
1. A self-bonding elastic shirred web product comprising a series of spaced elastic yarns between coextensive thin webs of which at least one is a non-woven porous fibrous web, the whole being uniformly impregnated throughout and bonded together in a unified structure with a polymeric binder having a weight per unit area at least equal to the weight per unit area of said webs, said yarns being maintained under partial tension in said unified structure, said web product being resiliently extensible under hand pulling to the extent of at least about one-third of its length.
2. The product of claim 1 wherein each web is a nonwoven porous fibrous web.
3. The product of claim 2 wherein said web is coherently bondable at least at moderately elevated temperatures and is elastically extensible to at least about twice its relaxed length.
4. The product of claim 1 further characterized as being coherently bondable under pressure at normal room temperature and wherein said polymeric binder comprises natural latex rubber.
5. The product of claim 1 further characterized as being coherently bondable under heat and pressure and wherein said polymeric binder comprises a soft non-tacky synthetic polymer.
6. The product of claim 1 wherein said elastic yarns are uniformly spaced at about two to about eight yarns per inch width.
7. An article of manufacture comprising two segments of the elastic web product of claim 1 coherently bonded together along an overlapping marginal area.
8. The product of claim 1 wherein one of said thin Webs is a polymeric film.
'9. The product of claim 1 wherein one of said thin webs is a metal foil.
10. The product of claim 1 wherein one of said webs comprises a reflective film.
(References on following page) References Cited UNITED STATES PATENTS Solis 156161 Plechner 16177X 5 Scheuer 16177X Martin 161-76X Galligan et a1 161-76 ROW 156183 10 6 2,561,891 7/1951 Tucker 161Met. Foil 3,316,136 4/1967 Pufahl 156160 3,468,748 9/1968 Bassett 161-122 ROBERT F. BURNETT, Primary Examiner R. L. MAY, Assistant Examiner US. Cl. X.R.