US3485711A - Low-density web-like cushioning structure of cellular filamentary material - Google Patents

Description

Dec- 23, 1969 F. H. FISH. JR.. ETAL 3,485,711

LOWDENSITY WEB-LIKE CUSHIONING STRUCTURE OF CELLULAR FILAMENTARY MATERIAL 2 Sheets-Sheet l Filed June 23, 1965 IGZ M O nn. 1 JE D C... nn. N rr .l H U A V| N m E R D R C nn un A 0 A .l..| EL s.. TL .Inn UA Us EEE ER LC JH RM L G RCL ml Eon rr. n N U D A Dn /o o B0 ...l P 0 u N un vl o o/ BCI A l. D| 0 .IJ D E 0 0 U w N S P vl l. 00 R ww l. l \\J LIC \.l.\l`/ Q C la 5 2 0 2 l N 0u. 5 5/ nl L f\ D A 0 .L m E v s s E R DI um 0 5 C 0 ATTORNEY F. H. FISH, JR, ETAL Low-DENSITY WEB-LIKE CUSHIONING STRUCTURE oF CELLULAR FILAMENTARY MATEMAL 2 Sheets-Sheet 2 Filed June 23, 1965 o O4 o /D a Xo O o G o//lp G N N R11 o Dn| Ml! EN no R0 f .|11 0l 0H Ewuv DTS BU U Pv x C n v nU O 0 0 O O 0 0 0 0 o 0 0 o 0 0 0 O O o nu .Iv .4. 11.... nsf'. Il. m 9 ou 7. 6 5 d.

% COMPRESSION AT 25 PSI (|16 HGJCHZ) INVENTORS FLOYD HAMILTON FISH, JR, CAWLEY RICHARD STINE ATTORNEY nited States Patent O US. Cl. 161-150 9 Claims ABSTRACT OF THE DISCLOSURE A resilient, low-density cushioning structure, suitable as a carpet underlay, comprising randomly arranged, closed-cell, pneumatic, polymeric, cellular filamentary material, is disclosed. The material has superior cushioning properties at exceptionlly low area-Weight.

For many flooring applications it is desirable that the flooring surface have resilient, luxuriant underfoot aesthetics. Usually it is also desirable that the surface feel warm as a result of thermal insulation provided by the surfacing material. Carpets and rugs of 'numerous constructions have been used to provide these functions for ages. In general, carpets are comprised of some dimensionally stable base layer to which textile yarns are attached in such a fashion as to create a wear-resistant decorative surface. These textile yarns provide levels of underfoot aesthetics and insulation approximately in proportion to the quantity of yarn employed per unit of carpet-area, at least for similar carpet-constructions. Ex-

erience has shown that the quantities of yarn required for the desired property levels are so great as to render carpets, as a sole covering over rigid floors, prohibitively expensive for many potential installations.

Carpet-underlays were developed for use between the carpet and the rigid floor, these underlays also providing resiliency and heatand sound-insulation properties. ln general these underlays are much less expensive, less physically strong, and less Visually attractive than the overlying carpets, but their use beneath carpets imparts the desired underfoot aesthetics and insulation to the combined floor-covering with a great reduction in the quantity of expensive textile yarn employed. It is known, moreover, that the use of certain kinds of underlay beneath commercially available carpets can increase the useful carpet life-span by a factor of two, or more.

The specification of required properties for carpetunderlays is particularly diflcult because of the wide variety of conditions to which they are subjected. These include sustained compression under medium to large loads exerted, for example, by furniture legs. Simultaneously, they include transient walking loads ranging from the modest ones of mens feet and shoes to the very concentrated loads applied by ladies narrow spiked heels. After removal of sustained loads, the underlay should regain substantially its original thickness within a reasonable period of time so as not to leave a permanent indentation. Under transient loads, however, the underlay should softly cushion by rather great transient thickness reduction, again with regain of substantially its original thickness. These load-support, cushioning, and recovery properties should also be retained during years of use. In many respects these requirements lead to opposed property specifications, and all known carpet-underlays embody some degree of compromise.

One well-known type of underlay is comprised of animal and/or vegetable fibers in a felt, with or without impregnation by rubber latexes. These are hereinafter ice collectively referred to as hair/ jute underlays, for brevity. Hair/ jute underlays are dense and heavy, have low resilience, decrease usually no more than 50% in thickness under any load characteristic of the end-use, become more permanently compacted and even less resilient with use, and exhibit severe permanent depressions after removal of sustained loads. They moreover can cause extreme dusting, repugnant odors from mildew and degradation, and allergy problems.

Certain sponge-rubber underlays, with either plain or deeply patterned surfaces, constitute the currently most popular products against which other carpet-underlays are compared. In order to provide the desired properties, they must be relatively dense and are7 consequently, expensive. When new, they are very luxurious under foot, but many bottom out rather easily under loads greater than charactersitic of walking loads. Regain of original thickness upon removal of either transient or sustained loads is rapid and substantially complete. After only two to three years of use, however, many sponge-rubber underlays became so degraded from exposure to the atmosphere that they lose much of their resilience, become physically weak, easily crumble, and frequently stick to adjacent floor and carpet surfaces.

More recently, resilient foamed polyurethanes have been introduced for carpet-underlay use but, at economically competitive densities and area-weights, bottom out even more readily than sponge-rubber. In addition, they are physically weak and easily torn even when new. A peculiarity of resilient polyurethane foam is a compression behavoir characterized by initial stiffness, followed by extensive collapse with essentially no increase in load, and suddently terminating in a substantially incompressible state. This intermediate unsupported collapse can give a walking preson a sensation of falling with abrupt termination of the fall, and it is undesirable both because it upsets the walkers sense of balance and because it does not properly support carpets to increase their useful life-span.

Various forms and combinations of the above three types of materials constitute substantially all the commercial Carpet-underlays currently available.

This invention provides a novel carpet-underlay at areaweights greatly less than for any materials heretofore available. Another provision is a carpet-underlay for which the resistance to compression increases continuously with increasing compressive load; i.e., there is no unsupported collapse, and there are no points of inflection in the loadcompression curve. A further provision is an underlay which compresses only 45 to 70% in thickness under a 25 p.s.i'. (1.76 kg./cm.2) load uniformly distributed over a flat indentor at least about 4 in.2 (about 26 cm?) in area. Still another provision is a carpet-underlay which is substantially unchanged in chemical and physical properties during normal life-times in use. A still further provision is an underlay which, used between a carpet and rigid floor, imparts luxuriant underfoot aesthetics. Yet another provision is a carpet underlay which recovers substantially all of its initial thickness after transient or sustained compressive loading characteristic of the enduse.

These and other provisions result from the following invention which is a resilient, low-density, web-like cushioning structure, suitable as carpet-underlay, comprised of closed-cell, pneumatic, polymeric, cellular material in lamentary form, said filamentary material being randomly disposed within said structure to provide numerous crossings of filament-portions, being consolidated so as to distort iilament-portions around one another and provide substantial areas of iilament-to-lament engagement such that the average ratio of volume of said lamentary material to total volume of said structure is at least 0.4, and being bonded at least Within portions of said structure to permanently retain said consolidated volume, major portions of said filamentary material having a density of from about 0.008 to 0.06` gm./cc. and containing within the cells thereof about 6y to 40 gm. of an impermeant inflatant per 100 gm. of polymer.

The above-described cushioning structure possesses a combination of features which makes it outstandingly superior to previously known types of carpet-underlay, It has the coherency and strength of a molded sheet and yet, being based upon a lamentary material, comprises a porous, breathable open network. The pneumatic character of the filaments insures that there will be no unsupported collapse as a compressive load is increased. Moreover, the fact that the pneumaticity is derived from a myriad of small, closed, gas-containing cells in the laments, and not merely from an impervious casing about porous filaments, means that the load will be more evenly distributed within and across the structure. Still another feature of considerable importance is the fact that the filaments are in a particula-rly distorted, e.g. stressed, condition owing to the consolidation-hence increasing the load-support property.

The invention Will be further described with reference to the drawings wherein:

FIGURE 1 represents an unconsolidated filament-batt from which the products of this invention can be prepared.

FIGURE 2 is the batt of FIGURE 1 consolidated to a cushioning structure of this invention.

FIGURE 3 is a preferred, one-side-embossed cushioning structure of this invention.

FIGURE 4 is the cross-section yL10-40 of the underlay 'of FIGURE 3 showing it installed on a floor beneath a carpet.

FIGURE 5 is a load/compression diagram comparing certain products of this invention with conventional underlays.

FIGURE 6 is a comfort map for various underlay products.

`Cushioning structures according to this invention can be regarded as being in sheet form; i.e., their parallel broad faces are very extensive compared to the thickness, which is about 0.1 to 1.0 inch (0.25 to 2.5 cm.) and preferably from 0.2 to about `0.45 inch (0.50 to about 1.15 cm.). The preferred thicknesses correspond to those of commercially available carpet-underlays. These cushioning structures are comprised of one or more closed-cell foam-filaments, the cells of which contain impermeant inflatant gas (as more fully described hereinafter). Because of the presence of impermeant inflatant gas, an osmotic gradient for the inward permeation of air exists, and the gas pressure within the closed cells exceeds atmospheric. Consequently, the foam-filaments are inflated, resilient, and pneumatic so as to be relatively resistant to bending. Either continuous or staple filaments can be used. Length-to-diameter ratio for staple filaments is preferably at least in order to insure adequate strength and stability for the ultimate cushioning structure.

In forming these cushioning structures, foam-filament are laid down in such a fashion as to build up the thickness while creating a random distribution of filament directions in the plane of the structure.' Thus, there are numerous crossings of filament-portions and considerable penetration of portions of filaments generally positioned at one thickness level into adjacent thickness levels. Area-weight of foam-filaments in a cushioning structure should be substantially constant when measured on areas with linear dimensions very much larger than the filament-diameter. In order to achieve satisfactory uniformity of filament-Weight distribution, it has been found that the thickness of the structure at any point should be equivalent to at least 3 times the average contribution of a single filament to the thickness in the immediate area.

Stated differently, the thickness of the structure is equivalent to at least 3 filament-thicknesses regardless of the state of filament distortion in that area. Area-weights ot' the structures of this invention, based only on the weight of filaments, are broadly from about 1.0 to 10 oz./yd.2 (34 to 340 gm./m.2) and preferably from about 1.5 to about 5.0 oz./yd.2 (50 to 1720 gm./m.2); but structures of higher area-weight can also be provided, if desired.

As initially deposited in a filament-batt, the pneumatic filaments are much too stiff and too light to drape or bend around one another at their crossings. Only point-contacts between crossing filament-portions are made, and these are rather widely spaced. Unless forced into a consolidated state, the filaments occupy only a small fraction of the effective volume of the batt, this volume fraction usually being less than about 0.25. When such non-consolidated structures are compressed, thickness reductions of from 25 to 50% can result from loads of only about l p.s.i. (70 gm./m.2). Such soft cushioning results, primarily, because initial thickness distortion is a combination of filament-bending and filament-compression at the point-contact filament-crossings Where the volume of gas being compressed is extremely small compared to the total volume of the batt.

Compressive loads to be resiliently supported by carpetunderlay are characteristically of the order of 25 p.s.i. (1760 gm./crn.2), or greater. In order that the filamentbatts can support these loads without being excessively thick or initially too soft, it is necessary that the batts be consolidated, that is, reduced in thickness until the filaments are forced to bend around one another, thus forming more numerous and extensive interfilament contacts. In effect, the pneumatic filaments in the products of this invention are pre-loaded. Volume fraction of foam-filaments exceeds 0.4 but is less than 1.0; i.e., filament identity is retained and numerous interlament passageways remain to provide a breathable, open, filamentnetwork.

Interfilament bonding must be provided to prevent spontaneous re-expansion of the consolidated batt to its unconsolidated state. Consolidation does not decrease the super-atmospheric pressure within the closed cells of the filaments, except in minor areas where the foam is either completely collapsed or melted to effect bonding. Consequently, the filaments remain pneumatic and Will regain their unconsolidated orientation unless constrained.

Referring now to the figures, FIGURE l represents an unconsolidated filament-batt generally indicated by the numeral 10 and comprised of inflated filaments 11 which are undistorted except for perhaps minor folds along some filament-lengths where curvature is excessive. FIGUR-E 2 represents one cushioning product 20 according to this invention and is the batt 10 of FIGURE 1 consolidated normal to its faces 13 to provide a carpet underlay, or similar cushioning batt, with a space-filling density based on filament-weight of from about 0.7 to 1.16 lb./ft.3 (0.011 to 0.026 gm./cc.). Such plane-surfaced carpetunderlays are kept consolidated by adhesives introduced to the batts in such a way as to form bonded interfilament crossings while the filament-batt is consolidated.

While plane-surfaced structures 20 as shown in FIG- URE 2 are effective forms of this invention, other preferred forms are consolidated lby embossing. By embossing is meant herein applying to the surface of a cushioning structure a repeated and nested set of geometric shapes formed from simple line elements, straight or curved, such that each line element is the common boundary of two geometric shapes (excepting those at the edges of, for example, the embossing roll). Examples of such suitable geometric shapes are triangles, diamonds, rectangles, hexagons, and the like. Along each line element the cushioning structure is thinnest and densest, while at the center of each shape the cushioning structure is thickest and least dense. The width of each line element can vary from that of a knife-edge to about 0.25 inch (0.635 cm.). `It should be at least as long as times the maximum transverse cross-sectional dimension of the fully inflated filament employed but no greater than about 30 times that dimension. Larger patterns may fail to produce sufficient consolidation in the thicker areas. Less than 50%, and preferably less than 25%, of the surface area of the cushioning structure should be reduced to the minimum thickness. The filaments along the line elements are stabilized in this reduced thickness configuration thereby rendering the cushioning structure strong and tear-resistant while simultaneously providing the con- `straint which keeps the whole structure consolidated. Thickness stabilization along these embossed lines can result either from applied adhesive or by thermal fusion of the polymeric foam.

FIGURE 3 is a perspective view of a carpet-underlay 30 of the preferred one-side embossed construction. FIG- URE 4 is a cross-sectional representation of the underlay 30 of FIGURE 3 as shown at l0- 40, FIGURE 4 including in addition an overlyingI carpet 41 and supporting rigid floor 43. With the rounded protuberances 4S, formed by embossing, against rigid floor 43 this form of the invention has particular advantages. Since only a small area of each protuberance 45 contacts the fioor, and since this is its lowest density, softest portion, the underlay is more readily compressed by light loads on overlying carpet 41. As the compressive load increases, more area of each protruberance 45 comes into contact with rigid fioor 43, and the density of compressed cushioning structure 30 in that area increases. The resistance to compression thereby increases with increasing compression, as is most desirable, and the underlay is most luxurious underfoot for the lighter transient loads. Under heavy loads, however, the underlay remains resiliently compressible because, in the limit, it becomes substantially a uniform layer of compressed gas. Moreover, since the gas is enclosed in closed foam cells, it quickly returns the underlay to its original thickness by its expansion.

A further advantage of the preferred structure 30 of FIGURES 3 and 4 is that, even if some air ultimately escapes from the cells under sustained loads, the underlay immediately regains essential fiatness of its plane surface 47 to support the overlying carpet 41 without temporary apparent indentation. The collapsed protuberance(s) 45 may pull away from the fioOr 43 for a short time, but impermeant infiatant within the foam-cells provides an osmotic gradient for re-entry of displaced air and eventual recovery of the protuberance(s) 45 to substantially the original size and shape.

Maximum thickness of embossed underlay 30 is also the effective underlay-thickness between carpet and floor. Underlay-density computed from this maximum thickness and from the constant area-weight of foam-filaments should be in the range from about 0.3 to about 1.6 lb./ft.3 (0.005 to 0.026 gm./cc.). This minimum density usually occurs only near the center of each geometric shape, the density increasing along the line elements 31 to a maximum of from about 8 to 100% of the density of the unfoamed, solid polymer.

Cellular filaments for use in the products of this invention require certain characteristics and properties. A particularly essential characteristic is that they have a major proportion of closed cells since open cells cannot confine the required impermeant inliatant and cannot provide the pneumaticity from which the cushioning properties derive. Visual or microscopic examination is usually sufficient to detect whether closed cells predominate; but, otherwise, the closed cell content can be determined by the gas displacement method of Remington and Pariser, Rubber World, May 1958, p. 261, modified by operating at as low a pressure differential as possible to minimize volume changes.

The cell-walls of suitable cellular filaments are composed of high molecular weight polymers-usually synthetic organic thermoplastic polymers. A `wide variety of both addition and condensation polymers can form cellular structures with the essential characteristics. Typical of such polymers are polyolefins, polyamides, polyesters, and halohydrocarbon polymers such as polyvinyl chloride and the like. The filaments are homogeneously foamed throughout; i.e., the outer surfaces are comprised of numerous cell-walls rather than being separately identifiable casings or coverings. The pneumaticity and resilience of the products of this invention derive from gas confined within the foam-cells, and these properties are provided at underlay area-weights very much less than can be obtained from filaments with dense casings.

Fully intiated filaments useful in constructing the products of this invention are recoverably yieldable with densities in the range from about 0.008 to about 0.06 gm./cc. A highly suitable class of cellular structures has polyhedral-shaped cells defined by thin, film-like cell-walls. Such thin cell-walls are very fiexible, contributing greatly to the yieldable nature of the filaments; and, as described hereinafter, are readily plasticized for `the inward permeation of impermeant infiatant.

A particularly desirable type of cellular material is ultramicrocellular as described in U.S. Patent No. 3,227,664 to Blades et al., the disclosure of which is incorporated herein by reference. These preferred structures contain at least 1,000 cells per cc., the average transverse dimension of which cells is less than 1,000 microns. Substantially all of the polymer is present in the cell-walls which are film-like elements less than 2 microns, and preferaby less than 0.5 micron, thick. The thickness of a cell-wall, bounded by intersections with other walls, does not ordinarily vary by more than i30%; and adjacent walls are commonly of substantially the same thickness, i.e. within a factor of 3. Moreover, the polymer in the cell-walls exhibits uniplanar orientation and a uniform texture, as fully described in the aforementioned patent.

One of the features `of ultramicrocellular structures is the high degree of orientation of the polymer in the cell walls, `which contributes to the unique strength of these structures. A preferred class of polymers from which to make cellular filaments for use in the products of this invention is that class which responds to an orienting operation (eg, drawing of bers or films) by becoming substantially tougher and stronger. This class is wellknown in the art and includes, for example, linear polyethylene, stereo-regular polypropylene, 6-nylon, and polyethylene terephthalate. Because most gases permeate through polyethylene terephthalate very slowly, it is particularly preferred.

An impermeant infiatant gas is one that permeates the cell-walls so slowly, as compared to air, that it is substantially permanently retained within closed cells, even under compression. The rate of permeation for any gas through a given polymer increases as its diffusivity and solubility increase. Accordingly, candidates for impermeant inflatants should have as large a molecular size as is consistent with a high vapor pressure, that is, a vapor pressure of at least 50 mm. of mercury at normal room temperatures. Atmospheric boiling points for preferred impermeant infiatants are less than 25 C., and preferably less than 15 C. Preferred impermeant infiatants are also from that class of compounds whose molecules have chemical bonds different from those in the confining polymer, a low dipole moment, and a very small atomic polarizability, thus assuring insolubility in the polymer.

Suitable impermeant infiatants are inert materials selected from the group consisting of sulfur hexafluoride and saturated aliphatic or cycloaliphatic compounds having at least one fluorine-to-carbon covalent bond and wherein the number of fluorine atoms preferably exceeds the number of fluorine atoms preferably exceeds the number Of carbon atoms. Preferably these inliatants are perhaloalkanes or perhalocycloalkanes in which at least 50% of the halogen atoms are fluorine. Although these inflatants may contain ether-oxygen linkages, they are preferably free from nitrogen atoms, carbon-to-carbon double bonds, and

reactive functional groups. Specific examples of useful impermeant inflatants include sulfur hexafluoride, perfluorocyclobutane, sym-dichlorotetraiiuoroethane, chlorotrifluoromethane, dichloroditiuoromethane, and chloropentaliuoroethane. Particularly preferred because of its inertness, very low permeability rate, large molecular size, and lack of toxicity is peruorocyclobutane with an atmospheric boiling point of about 6 C.

The presence of impermeant iniiatant gas within the foam-cells guarantees full inflation of the filaments by providing an osmotic gradient for the inward permeation of air until internal pressures are super-atmospheric. If some air is lost during compression, the filaments thereby spontaneously re-inate after removal of the load. Foam-filaments containing impermea-nt inliatant are seen to be durably pneumatic, as opposed to those inated only with air or with rapidly permeating fo-aming agents. In practice, a certain minimum concentration of impermeant inflatant is required to provide these advantages. From about to about 40 grams of impermeant infiatant per 100 grams of polymer has proved effective for use in carpetunderlay.

Fully inflated foam-filaments useful in the construction of the products of this invention have major cross-sectional dimensions the range of 0.025 to 0.25 inch (0.635 to 6.35 mm.) but are preferably in the range from 0.050 to 0.100 inch (1.27 to 2.54' mm.). Although various cross-sectional shapes can be formed, circular ones are usually preferred for which the circular extrusion orifices are easily made. In deeply embossed carpet-underlay it is possible to reduce filaments along the line elements to solid polymer containing essentially no impermeant infiatant. At other points, the necessary consolidation may severely alter cross-sectional shape of the filaments. The specification of levels of retained impermeant infiatant refers only to the major portion of the underlay in which the filaments remain inflated, however distorted they may be in cross-section.

The determination of quantity of confined impermeant inatant is readily carried out. A foam-filament with impermeant inflata-nt in its lcells and at osmotic equilibrium with air has an internal partial pressure for air of about one atmosphere. Total internal cell pressure exceeds atmospheric by about the partial pressure of the impermeant intiatant. With these conditions, air buoyancy corrections to weights in air are, at best, only second order. Weight in air W1, of an inflated sample is measured. The sample is then reduced between heated platens to a solid, non-foamed film, after which its weight in air W2, is measured. Platen temperatures must, of course, be low enough that no weight change attributable to polymer degradation can occur. Impermeant infiatant content I, in grams per 100 grams of polymer is then readily computed using Equation 1.

100ml-W2) W2 (l) Other physical methods, such as gas chromatography or spectrophotometry, can also be used to determine concentration of impermeant inflatant.

When adhesives are employed in constructing underlay, they must adhere well to the filaments and be durably flexible so as not t0 fail during compressive exercising. A great variety of commercial latexes, both natural and synthetic, are suitable. Adhesive bonds must be elastic, but not necessarily elastomeric. Elastomeric adhesives are, however, frequently employed. Types of adhesives found satisfactory include thermoplastic, thermosetting, heatcurable, melt, and the like. Since adhesives are normally applied in the form of dilute solutions or dispersions, those adhesives either soluble or dispersible in volatile liquids which are non-solvents for the polymer are preferred.

The amount of adhesive required for internal constraint against loss of consolidation depends on the type of adhesive and in what form it is applied. Normally this amount is less than of the weight of foam-filament, and preferably less than about 25%.

Certain adhesives may have a tendency to yield a iinished product which is somewhat noisy; i.e., the filamentsurfaces slip against one another during compression to cause squeaky or scratchy sounds. This noise may be largely overcome by applying a lubricant to the filament batt, such as various silicone oils or detergents. In a preferred method of treatment for silencing, which also provides decorative colored surfaces, the underlay-surface is first sprayed with a solution of the above adhesives and a desirable dye and then dipped in a solution of silencer. Up to 100% or more, by weight of filaments may be added to the area-weight of underlay in this manner. In typical underlay constructions the weight percent of foam-filament varies between 20 and 80. Although the proportional quantities of adhesive involved may seem very large, it must be remembered that any addition of dense adhesive to the ultra-low-density filaments in the products of this invention must of necessity be a sizeable fraction by weight. Within the specified limits, the quantity of adhesive employed leaves essentially unchanged the openness and breathability of the consolidated filament batt.

In alternative forms of this invention, either or both surfaces can be covered with a variety of surfacing materials. Adhesively bonded surfacing materials include various net-like fabrics, many nonwoven fabrics, foils of open-cell foams, and many commercial plastic films such as those of polyethylene, polypropylene, polyvinyl chloride, and polyethylene terephthalate. It is also advantageous in some instances to coat or extrude onto the surfaces foamable compositions of, for instance, rubber, polyurethane, or neoprene, which become self-bonded while at the same time expanding into an open-celled foam layer. Also, carpet pile yarns may be attached. Other variations will be immediately apparent to one skilled in the art.

For purposes of testing and comparing the products of this invention with previously available materials, a load of 25 p.s.i. (1.76 lig/cm2) was selected as characteristic of both transient and sustained compressive loading. Load vs. compression curves were obtained on ll by 16 inch (27.9 by 40.6 cm.) underlay specimens using a 4 in 2 (25.8 cm?) round indentor with a fiat bearing face. Indentor speed of entry was nominally 0.5 in./rnin. (1.27 cm./min.), and it was maintained up to a load of at least 25 p.s.i. (1.76 kg./cm.2). FIGURE 5 presents such load-compression curves for four products of this invention and compares them with commercially available underlays. The upper heavy curve within its shaded area is for a typical hair/jute underlay, the shaded area showing the range covered by the general class of such hair/jute constructions. The intermediate heavy curve and its shaded area likewise represent available, new, patterned` sponge-rubber underlays. The lowest curve and shaded area are for various new polyurethane underlays. Overlaid in dashed lines are load-compression curves for 4 selected underlays of this invention.

Important advantages of the products of this invention are evident from inspection of FIGURE 5. First, they may be constructed with 25 p.s.i. (1.76 kg./cm.2) compression properties extending continuously from those of firm hair/ jute to those softer than sponge-rubber. Consumer preference tests in which housewives walked on identical carpet samples beneath which were concealed several currently popular underlays and a variety of the products of this invention revealed a distinct preference for those underlays which, tested at a load of 25 p.s.i. (1.76 kg./cm.2), compressed about 45 to 70% of their initial thicknesses. This property level, supplied only by the more expensive commercial underlays, is Well within the range most characteristic of those structures of this invention. Finally, the shape of the load-compression curve for the underlays of this invention is different from and improved over those for known underlays. Products of this invention decrease in rate of compression continuously with increasing load. Both sponge-rubber and polyurethane foam compress rapidly at low loads, decrease this response precipitously at or below p.s.i. (0.35 kg./cm.2), and compress quite slowly thereafter.

In addition to satisfactory load/ compression behavior in one cycle of compression, it is also necessary that carpet underlays remain resiliently compressible under cyclic loading at the end-use load. This is indicated by dynamic modulus for which low values characterize superior performance. Dynamic modulus, Z, is best defined by its method of determination. Sample size, indentor, and apparatus are the same as for load/compression determination. The sample is cycled between and 25 p.s.i. (1.41 and 1.76 lig/cm?) loads 10 times with about 0.5 inch/ min. (1.27 cm./min.) indentor rates for both compression and recovery and with no time-delay *between cycles. A secant modulus to the tenth compression cycle is dynamic modulus in p.s.i. (kg/cm?) Computation is according to Equation 2.

(J2-C1 (2) wherein AL is 5 p.s.i. (0.35 14g/cm2), C2 is percent compression at p.s.i. (1.76 kg./cm.2), C1 is percent compression at 20 p.s.i. (1.41 kg./cm.2), and C is computed from ho-h ho (3) wherein h is sample thickness at a given load and 1z0 is uncompressed original sample thickness. Table I lists pertinent dynamic modulus results for 31 commercially available carpet-underlays and 22 different experimental samples according to this invention.

fragile items such as easily bruised fruit. They are also useful for thermal insulation in walls of buildings, in refrigerated containers, and the like.

The following examples are illustrative of the present invention but are not intended as a limitation thereof except as provided in the appended claims. Where tensile strength is specified it is the force per unit of width at tensile failure for a 3 inch (7.6 cm.) wide and 7 inch (17.8 cm.) long sample clamped in jaws separated by 5 inches (12.7 cm.) and moved apart at 5 in./min. (12.7 cm./min.). All parts and percentages are by weight unless otherwise specified.

EXAMPLE I Ultramicrocellular filaments were prepared by extrusion of a foamable composition from a l-liter cylindrical pressure vessel through a 5-hole die into the ambient atmosphere. Charged to the vessel under anhydrous conditions were the following:

Polyethylene terephthalate gm 400 Methylene chloride (at -25 C.) ml-- 350 1,1,2-trichloro-l,2,2-tri1iuoroethane (at -25 C.)

ml Peruorocyclobutane gm 52 The polyethylene terephthalate was a homopolymer with relative viscosity (RV) of about 41. Relative viscosity as used herein is the ratio of absolute viscosities at 25 C. of polymer solution and solvent, with the solvent being itself a solution of parts of 2,4,6-trichloropheno1 in parts of phenol and with the polymer solution containing 8.7% polyethylene terephthalate. Before use, the granular polymer was dried at 220 C. for 16 hours under vacuum with a small nitrogen bleed. Liquid foaming agents which may replace methylene chloride in the extrusion of ultramicrocellular polyethylene terephthalate TABLE I.DYNAMIC MODULUS COMPARISONS Average Minimum Maximum No. of Class Types p.s.i. (kg/cm?) p.s.i. (kg/cm2) p.s.i. (kg./em.2)

Hair/Jute 1 11 631 (44. 4) 539 (37. 9) 759 (53. 4) Sponge-Rubber (patterned) 6 583 (41.0) 526 (37. 0) 42 (45. 2) Sponge-Rubber (premium-fla 6 420 (29. 6) 333 (23. 4) 184 (a5. 2) Polyurethane 8 1, 288 (90. 6) 820 (a8. 3) 1, 60o (113. 0) This Invention 22 390 (27. 4) 240 (16. 9) 547 (28. 5)

From Table I it is quite apparent that the underlays of this invention have the lowest dynamic moduli and are, therefore, more resiliently compressihle under enduse loads. These results are shown graphically in FIG- URE 6 which is a comfort map for carpet-underlays. Area I encloses presently available hair/jute candidates. Area II (and its one widely different point) the premium fiat sponge-rubber candidates, Area III the Weihe, nipple, etc. patterned sponge-rubber candidates, and Area IV the candidates based on polyurethane foams. Variously shaped points indicate underlay according to this invention, as completely described `in appended examples. It will be seen from FIGURE 6 that the carpet-underlay of this invention has superior dynamic modulus over a broad range of percent c-ompression values, including the most preferred range.

As is shown in the examples, these products have excellent recovery from both transient and sustained loads, and they have high tensile strengths. They also maintain their integrity and cushioning over a long life-time, do not dust, are non-allergenic, and do not decompose to create foul odors. Not only do they provide carpetuuderlay of unprecedentedly low area-weight, but their load-compression properties are superior to any heretofore known carpet-underlays.

Being particularly useful as carpet-underlay, the products of this invention are not so limited. Thus they serve in numerous cushioning applications such as in the walls of cushioning cartons or as separator sheets between foams include ethylene chloride, chloroform, and carbon tetrachloride.

Each hole of the extrusion die was 0.003 in. diameter by 0.006 in. long (0.0762 rnrn. x 0.1524 mm.), and the die was attached to one end of the cylindrical pressure vessel. A sandwich of screens was affixed upstream from the extrusion holes being 50, 325, 325 and 50 mesh screens respectively (U.S. Sieve Series). The sealed pressure vessel was rotated end-over-end while being heated. With the temperature of the contents at 213 C., rotation was stopped with the die facing downward and held that way for 2 minutes to allow drainage of the solution before opening the die holes. In this period, connection to a 1200 p.s.i.g. (84.4 kg./cm.2 gage) nitrogen ballast tank was made through a valve in the top of the vessel. About 40 minutes were required to extrude all of the foamable composition.

The extruded filaments expanded to their maximum diameter near the face of the extrusion die, but thereafter rapidly collapsed due to vaporization and loss of methylene chloride, to a density of about 0.065 gru/cc. By subsequent heating for a few minutes at about C., air could diffuse into the closed cells to re-expand the filaments to their maximum diameter of about 0.010 inch (0.25 mm.). Filaments produced in such a way will generally have a density of from 0.025 to 0.03 gm./cc. in the fully inflated state and will retain within their closed cells from 1.0-1.5% of perfluorocyclobutane and about 5% of the trichlorotritiuoroethane impermeant 11 natants (percentages by weight of the expanded filaments).

These filaments were to be used in the construction of a carpet-underlay specimen. Accordingly, the iilaments were collected by and passed through a 0.25 inch (0.635 cm.) diameter pipe located several feet below the extrusion die and fed with a downward-directed air stream from a supply at 20-25 p.s.i.g. (1.4 to 1.8 kg./cm.2 gage). Between the die and the pipe was placed a magnesium bar over which each iilament was passed. About 4 feet (1.22 m.) below the exit end of the pipe, a large aluminum plate was held for randomly collecting the filaments. Water was iinely sprayed onto the filaments from a paint spray-gun (Binks Mfg. Co. Type No. D5661) located at the level of the air-pipe. It was known that, without the added weight of water, the extruded iilaments would be blown off the aluminum collection plate by the air jet. The aluminum plate was held by hand and moved in such a way as to build up a uniformly thick batt about 3.5 inches (8.9 cm.) thick. An 8 X 8 inch (about 20 x 20 cm.) square cut from this batt was sliced to provide two squares, each of about one-half the original thickness. These were designated A and B, B being slightly thinner than A.

Batts A and B were converted to carpet-underlay specimens by the same general procedure. Expanded-metal sheets were placed on one face of each sample, each metal sheet being about 0.040 inch (1.02 mm.) thick and having diamond-shaped openings with approximately 1.5 X 0.5 inch (3.8 x 1.26 cm.) diagonals. Each opening was separated from the next by a strip of metal approximately 0.2 inch (5.5 mm.) wide. Each sample with its aligned expanded metal plates in place was put on one platen of a hydraulic press, and the other platen was closed onto the sample at room temperature to emboss the sample with the pattern of the expanded metal sheet. Removed from the press, the sample was sprayed with a dilute solution in trichloroethylene of a polyurethane-based adhesive prepared by capping a polyester macroglycol with a diisocyanate, blocking the isocyanato groups with the oxime of methyl ethyl ketone, and further reacting with methylene-bis-orthochloroaniline. The sample was then placed in an air-oven at 120 C. for one hour whereupon the diamonds corresponding to the holes of the expanded metal grew thicker from air-reinflation of the filaments. The embossed outlines did not expand, however, and served to keep the sample consolidated. This heat treatment also dried the samples. Although embossed from one side only, the re-iniiated samples grew thicker in both directions so as to appear to have been embossed from both faces.

Sample A employed four superimposed layers of the expanded-metal sheet and was pressed at 500 p.s.i. (35.2 kg./cm.2) for minutes. Thickness within embossed outlines was 0.265 inch (0.67 cm.) for the final product. Assuming this thickness constant over the whole area, density was 2.5 lb./ft.3 (0.020 gm./cc.).

Sample B employed iive superimposed layers of the expanded-metal sheet to make a still more flexible product. Applied pressure was 500 p.s.i. (35.2 kg./cm.2) for 5 minutes. Final thickness within the embossed outlines was about 0.25 inch (0.635 cm.), corresponding to a density of about 1.8 1b./ft.3 (0.029 gm./cc.).

Both A and B possessed the thickness, firmness, and resilience characteristic of desirable carpet underlay.

EXAMPLE II A deeply embossed and thermally bonded carpet underlay is described.

Ultramicrocellular polyethylene terephthalate filaments were prepared by extrusion of a uniform foamable solution from a 3-liter cylindrical pressure vessel, through an orifice 0.012 in. (0.305 mm.) in diameter and 0.006 in.

(0.152 mm.) long, and into the ambient atmosphere. Charged to the pressure vessel were:

Dried polyethylene terephthalate (RV=50) gm 1485 With the closed pressure vessel mounted in a box and exposed to hot circulating air, temperature of the contents was raised to 200 C. in 160 min. The pressure vessel was rotated end-over-end for 400 more minutes until temperature reached 220 C. During the next 135 min.. temperature was reduced to 190 C., after which the contents were allowed to extrude through the orifice. Prior to extrusion, a nitrogen ballast pressure of 1100 p.s.i.g. (77.4 kg./cm.2 gage) was applied, but this was reduced to 525 p.s.i.g. (36.9 kg./cm.2 gage) just before extrusion commenced. After being heated, the extruded filament had a smooth surface, a round cross-section, and no skin of dense polymer other than that in exposed cell walls. Apparent density was about 0.020 gm./ cc., diameter about 0.070 inch (1.78 mm.), and average cell transverse dimension about 22 microns. About 8 to 9 grams of 1,1.2- trichloro-1,2,2-triuoroethane were retained in the closed cells per 100 gm. of polymer.

The extruded iilaments were laid down randomly but uniformly on a moving screen belt in such 'a fashion that lengths of dierent area-weights Were obtained. From the belt, the Iilament batt passed immediately through the nip of a roll exerting about 2.0 lbs/in. (0.36 kg./cm.) or' width. This initial consolidation rendered the batt more coherent and easily handled without disintegration. The batt was rolled up between layers of kraft paper, held about 25 minutes, and then embossed. Embossing was between the plates of a flat-bed press. To one of the plates was fastened a deeply engraved embossing plate with a repetitive, nested, diamond design with 2 inch X 1 inch (5.08 X 2.54 cm.) diagonals and extending to 0.5 inch (1.27 cm.) deep into the plate. Separating each pattern was an embossing line nominally 0.0625 inch (0.159 cm.1 wide. The other plate of the flat bed press was not modified. Both were heated to about 250 C. The plates were closed on the batt to an averaged pressure of 45 p.s.i. (3.2 kg./cm.2) and held closed for a time period depending on area-weight of the batt being embossed. For 2.5-3.0 02./ yd" (S5-102 gm./m.2) batts, about 15 sec. was optimum, increasing to 30 sec. for 5.0 oz./yd.2 (170 gm./rn.2) batts. Successful deep embossing and permanent consolidation were obtained over a press plate temperature range ot` 250i20 C. Higher temperatures were found to cut through the batt along embossing lines and/or to melt other parts of the pattern to a solid iilm. Lower temperatures, even at higher pressures and residence times, failed to provide permanent consolidation so that delamination occurred upon subsequent iilament inflation.

Samples of a range of area-weights were cut from the above product, each 11 x 16 inches (27.9 X 40.6 cm.). These samples were placed in a large autoclave containing 2 ,liters of methylene chloride. Eight pounds (3.63 kg.) of peruorocyclobutane were then transferred to the closed autoclave. Heated to 55 |-2 C., autoclave pressures rose to i5 p.s.i.g. (6.3 to 7.0 kg./cm.2 gage). Liquid level was below the samples, but a circulating pump showered the mixed liquid over the samples for 5 min. The liquids were then blown from the autoclave, and the samples were removed and dried for 15 min. in an aircirculating oven at 125 C. Filaments cut from the centers of the embossed patterns were found to contain 15i2 grams of peruorocyclobutane impermeant inflatant per gms. of polymer. None of the 1,1,2-trichloro-1,2,2-trifluoroethane remained.

To silence the noise (scroopiness) of these underlay samples, they were dipped in a silencer solution, drained. and dried for 30 min. in an air-circulating oven at 125 C. Such samples are labeled 11 and 11a in Table Il, and

13 denoted by filled circles in FIGURE 6. Curve d of FIG- URE corresponds to sample No. 11.

The silencer solution contained: (1) 9 parts of a 40% aqueous emulsion of approximately equal parts of poly- (dimethylsiloxane) and poly-(methylsiloxane), (2) l part of Dow-Corning Catalyst 21 (a mixture of dibutyltindilaureate and the zinc salt of Z-ethyl hexoate), and (3) 90 parts of distilled water.

Alternatively, the thermally embossed structures were immersed in a latex solution, dried minutes at 125 C. and then given the above silencing treatment. I ess silencer was picked up this way, and pigment dispersed in the latex solutions imparted color to the otherwise White underlay samples. Samples l0, 10a-f, 12, 12a, and 12b of Table II were so prepared. Curve c of FIGURE 5 corresponds to sample 10. Open circles in FIGURE 6 denotes these samples. In no case was latex pick-up sufcient to significantly decrease the amount of open space in the samples. The latex solution Was a preparation containing 3 components provided by Alco Chemical Co.

Parts Foamtol BGL-9002 latex (a 58% dispersion in water of a mixture of 70 parts of natural rubber and 30 parts of butadiene/styrene (7S/25) co- These three components were dispersed in 900 parts of a surfactant solution prepared from 100 parts of Aquarex@ ME surfactant, 10 parts of Daxad 11 dispersing agent, and 890 parts of distilled water. (Aquarex is a registered trademark of E. I. du Pont de Nemours and Co., Inc., for their sodium salts of sulfate monoesters of certain mixed higher fatty acids. Daxax is a trademark of Dewey & Almy Chemical Co. for their polymerized sodium salts of alkyl aryl and aryl alkyl sulfonic acids.)

A particularly effective silencing of these structures results if they are sprayed with or dipped in water dispersions of Elvax ethylene/vinyl acetate resins and talc, such as those described in Examples III and IV (Elvax is a registered trademark of E. I. du Pont de Nemours and Co., Inc.). Not only do these dispersions effect silencing, but they are also effective primary binders; and they are relatively inexpensive. Thus, they can constitute the sole binder employed, or they can alternatively be applied to previously bonded batts.

(0.011 to 0.018 gm./cc.). In general, thicknesses of samples in Table 1I are equal to or slightly greater than those preferred for carpet-underlay. Volume fractions of foam in the samples varied from about 0.55 to about 0.70. FIG- URES 5 and 6 show that these samples perform as underlay almost equivalently to the flat sponge-rubber underlays, which are the best and most expensive of previously available products. Area-weights for sponge-rubber underlays range from about 40 to about 80 oZ./yd.2 (about 1360 to 2700 gm./m.2) as compared to the 3.7 to 7.1 oz./yd.2 (126 to 241 gm./m.2) range of these samples.

To test recovery and durability under load, these sarnples were indented over a 1.0 in.2 (6.45 cm?) area with a 200 lb. (90.7 kg.) load for 4.0 days. On the average after removal of the load, 46% of the original thickness was recovered immediately, in 1 day, 76% in 2 days, 88% in 4 days, and substantially 100% in the limit.

EXAMPLE III This example is of an embossed carpet underlay prepared with a thermoplastic binder. Because the baths used for introducing impermeant iniiatant to the foamcells either dissolve or seriously weaken such a binder, it was necessary to introduce inflatant gas before consolidation of the laments to a carpet underlay.

The ultramicrocellular filaments used were prepared as described in Example II. A rotating blade mounted below the extrusion die cut the laments into staple with lengths of 5 il inches (l2.7i2.5 cm.). Peruorocyclobutane impermeant inatant was introduced into the foamcells by immersing the staple in a bath composed of methylene chloride/perlluorocyclobutane lboiling at 6 C. under atmospheric pressure and containing at least 9% of peruorocyclobutane. After 15 minutes in an air-oven at 125 C., the staple was fully inilated with a diameter of about 0.075 inch (1.90 mm.), a density of about 0.015 gm./cc., and a peruorocyclobutane level of 14 grams per grams of polymer.

A thermoplastic binder dispersion was prepared by mixing together This binder dispersion was sprayed onto the staple, the staple was placed in a box with a 15 X 25 inch t(38.1 x 63.5 cm.) open top, `and the box was placed in an oven `at C. until the water in the binder composition had TABLE )L- PROPERTIES OF THERMALLY CONSOLIDATED AND EMBOSSED UNDERLAY Area Weight (oz./yd.2)(gm.2) Percent Com- (1) pression at Dynamic Sample Silencer Thickness 25 p.s.i. or at; Modulus (p.s.i.) (2) No. Color Total Filament and Latex (inem-(cm.) 1.76 lig/cm!) (kg/cm?) R.M.A.

10 Goldeuyellow 6.7 (227) 4.2 (142) 2.5 (85) .510 (1. 29) 62.7 392 (27.6) 160.5 r 6.2 (210) 4.0 (136) 2.2 (75) .460 (1.17) 65.0 861 (25.4) 167.0 5.5 (187) 3.5 (119) 2.0 (68) .490 (1.24) 69.7 438 (30.8) 78.9 7.1 (241) 4.6 (156) 2.5 (85) .570 (1. 45) 55.5 425 (29. 9) 225.2 5.9 (200) 4.0 (136) 1.9 (64) .430 (1.09) 60.9 538 (37.8) 152.1 5.8 (197) 3.8 (129) 2.0 (68) 480 (1.22) 66.8 420 (29.6) 121.1 5.3 3.5 (119) 1.8 (61) 460 (1.17) 68.3 390 (27.4) 143.6 3.7 (126) 3.0 (102) 0.7 (24) 430 (1.09) 78.7 446 (31.4) 70.7 4.4 (149) 3.5 (119) 0.9 (31) 530 (1. 35) 72.1 456 (32.1) 73.2 5.6 3.1 (105) 2.5 (85) .550 (1.40) 68.0 364 (25.6) 140.8 4.0 (136) 2.2 (75) 1.8 (61) .470 (1.19) 75.8 391 (27.5) 70.4 4.5 (153) 2.4 (81) 2.1 (71) .470 (1.19) 59.6 419 (29.5) 163.3

(1) Obtained using a 4 in.' (25.8 cm) round indentor.

(2) RMA. is a trade-recognized abbreviation for the load in pounds on a 50 in.2 (332.6 0111.2) indentor to produce a 25% decrease in thickness. These values were computed by multiplying the 4 in.e load by (5D/4) The maximum-to-minimum thickness ratios for all of these samples were greater than 5. Minimum densities computed from area-weight of laments and effective (maximum) thickness, Were 0.60 to 0.77 lb./ft.3 (0.0096 to 0.0123 gm./ cc.) for the seven 10-coded samples, about 0.56 lb./ft.3 (0.0090 gm./cc.) for the ll-coded samples, and 0.39 to 0.47 lb./ft.3 (0.0062 to 0.0075 gm./cc.) for the 12-coded samples. Corresponding densities computed from total area-weight range from .71 to 1.14 1b./ft.3 75 embossing plate was composed of nested diamond-shaped patterns, with approximately 1 x 2 inch (2.5 x 5.0 cm.) diagonals which were recessed about 0.5 inch (1.27 cm.) into the plate. The raised embossing lines defining the patterns were about 0.0625 inch (1.50 mrn.) wide. The plates of the press were internally steam-heated to a temperature of about 125 C. Holding the uncompressed batt between the plates reactivated the adhesive, whereupon the plates were closed on the batt to a pressure of 40 p.s.i. (2.8 kg./cm.2), the steam was turned off, and cold water was circulated within the plates until their surface temperature reached about 50 C. On removing the sandwich, it was found to be stably consolidated and to retain the embossed pattern. The foam-foils were securely bonded to both surfaces, the one on the embossed face conforming precisely to the embossed pattern.

Area-weight of the embossed, carpet-'underlay specimen was about 6 oz./yd.2 (204 gm./m.2) of which both the ultramicrocellular staple and the binder contributed about 2.5 oz./yd.2 (85 gm./m.2) each. Maximum thickness at the rounded humps of the diamond-shaped patterns was about 0.36 inch (0.91 cm.), and minimum thickness along the embossed lines was about 0.07 inch (0.18 cm.). These thicknesses corresponded to densities of labout 1.4 1b./ft.3 (0.022 grrr/cc.) yand 7.2 lb./ft.3 i(0.115 gm./cc.) respectively.

A portion of the carpet-underlay was tested for durability by repetitively stomping it with `an indentor applying from to 15 p.s.i. (1.05 kg./cm.2) load in cycles of 5 seconds each. An average life-time for carpet-underlay so treated was estimated to be about 25,000 cycles. At the end of 25,000 cycles of stomping, and after allowing two days for recovery, 85% of the original thickness was regained in the area of test. Similarly measured at the end of 200,000 cycles of stomping 74% of the original thickness was regained. On another square-inch of the carpet-underlay, 111 pounds (50.3 kg.) were statically maintained for two weeks. During the week following removal of the load, 82% of the original thickness was regained. Excellent cushioning for this underlay is indicated by its immediate compression to only 27.5% of its original thickness under a load of 200 lb. (90.7 kg.) uniformly distributed over a 10 in.2 (64.5 om?) area. Average tensile strength at failure in the two principal directions was about 8 lb./in. (1.43 kg./cm.). This structure is seen to possess excellent durability, resilience, and strength properties for carpet underlay use.

EXAMPLE IV Wet parts Ethylene/vinyl acetate (67/33) copolymer (50% solids in water) 390 Talc (60% solids in water) 332 Extra Water 1300 The loosely bonded batt was placed between the fiat plates of 4a hydraulic press, steam-heated and watercooled as before. The stably consolidated fiat product was about 0.3 63 in. (0.922 cm.) thick with a density of about 0.84 lb./ft.3 l(0.0135 gm./cc.) of which -about 57% was contributed by foam-filaments and 43% by the binder. The product was about 13.5 inches (34.3 cm.) wide yand 22 inches (55.9 cm.) long. A number of flat carpet underlay specimens were similarly constructed to have either or both faces covered with surfacing materials including kraft paper, polymeric films, foam-foils, net-like fabrics, nonwoven tabriCS, and Carpeting- 1 5 EXAMPLE v This example illustrates that carpet underlay according to this invention, when maintained stably consolidated with a thermoplastic binder, can later be re-expanded to a greater thickness by a simple heat treatment. By overconsolidation, such products yare more easily and inexpensively shipped, to be re-expanded at the point of use.

The same materials and procedures described in Example IV were used to prepare ya flat carpet-underlay specimen about 13.25 inches (33.6 cm.) wide and 21.5 inches (54.6 cm.) long. Its over-consolidated thickness was 0.237 inch (0.602 cm.) at a density of about 1.88 lb./ft.3 (0.030 gm./Cc.), of which -about 55.6% was contributed by foam-filaments and 44.4% by binder. Two rigid expanded-metal plates were clamped over spacers to provide an opening of about 0.75 inch (1.90 cm.), `and the specimen was slipped into the space between the plates. With the assembly in an air-oven at C., the thermoplastic binder softened to allow the specimen to ll the space. Rebonding occurred on cooling to room temperature, `and the specimen finally obtained was stably consolidated at a thickness of about 0.75 inch (1.90 cm.) and at a density of about 0.595 -lb./ft.3 (0.0096 grd/cc).

EXAMPLE VI This example illustrates still another method for forming the cushioning products of this invention. A heated blade (or alternatively a spaced assembly of them) is drawn across the surface of the batt to melt some of the polymer, to smear molten polymer along the line of passage, land thereby to create an embossed line which provides the necessary constraint for stable consolidation. In order that sufficient constraint be provided by the tiny quantities of polymer which can be melted, it is necessary that the filaments be fully collapsed, i.e., have little or no gases within their closed cells. If they are fully inflated, the gaps between adjacent filament portions are so large that the available molten polymer cannot bridge the gaps to provide a stable, coherent, ernbossed line.

Substantially completely collapsed, continuous, ultramicrocellular filaments were prepared by extruding a 60% solution of polyethylene terephthalate in methylene chloride through a single orifice 0.015 inch (0.381 mm.) in both diameter and length. Relative viscosity of the polymer was about 56.5 and it contained only about 58 p.p.m. of water. Extrusion pressure was 800 p.s.i.g. (56.3 kg./" cm.2 gage) at a temperature of about 206-208 C. A sixlayer screen-pack upstream of the orifice contained 20. 100, 20, 200, 20 and 20-mesh screens respectively (U.S. Sieve Series).

A 10 foot (3.05 meter) long, 8 inch (20.3 cm.) diameter metal duct was swiveled near the extrusion die, its other downward end being automatically programmed to traverse the width of a conveyor belt while simultaneously moving in a complicated, perpendicular, zig-zag pattern. A downwardly directed jet of air from a 60-90 p.s.i.g. (4.2-6.3 lig/cm.2 gage) supply entering the duct about 3 feet (0.91 m.) below the orifice, carried the filament through the duct to randomly deposit it onto the moving conveyor belt. Area-weight of the collected batt was determined by the speed of the conveyor belt. Downstream from the collection area, the conveyor belt passed beneath a compaction roll exerting about 2 pounds/inch (358 gm./cm.) by `which the loose batt was converted into a weakly coherent sheet capable of being wound into a roll.

A portion of the above sheet was selected for conversion to a carpet-underlay specimen. It weighed about 4.9 oZ./yd.2 (166 gm./m.2) and was about 0.13 inch (0.33 cm.) thick. A 2 x 1 x 0.125 inch (5.08 x 2.54 x 0.318 cm.) metal blade, coated with polytetrafiuoroethylene resin was attached to an electrically heated soldering gun so that the first and last of its above dimensions described the lower surface. Heated by the soldering gun to about 300 C., the blade was moved in a straight line across the batt at about 8 ft./min. (2.44 JIL/min.) while exerting a force on the batt surface `of about p.s.i. (0.7 kg./cm.2). The heated blade melted part of the foam along its path, and smeared it along the 0.125 inch (0.318 cm.) wide path. Subsequent cooling and solidication of the melted polymer securely bound adjacent foam-filaments. In identical fashion, such lines were formed over the lwhole surface of the batt spaced about 2 inches (5.08 cm.) apart. Then the batt was turned over, and parallel lines spaced between those of the other face were formed. Each melted line penetrated about 0.07 inch (0.18 cm.) into the batt, corresponding to about 4 filament layers. Tensile strength at failure for this collapsed batt Vwas about 10 lb./in. (1.79 kg./cm.). A section of this embossed specimen was immersed in a bath containing methylene chloride and peruorocyclobutane for 40 minutes. This bath was a constant-boiling solution with a boiling point of -6 C. at atmospheric pressure. Removed from the bath, the portion was quickly placed between two metal screens spaced 0.5 inch (1.27 cm.) apart, the assembly being placed in a hot-air oven at 125 C. for 15 minutes. Removed from the oven and the screens, and equilibrated in air, the batt stabilized in thickness at about 0.7 in. (1.8 cm.) and contained in excess of 8 gm. of perliuorocyclobutane per 100 gm. of polymer. Thickness along the melted lines was about 0.21 inch (0.533 cm.) indicating that approximately 40% of the polymer along the lines remained cellular.

Another portion of the collapsed batt was similarly embossed and reinfiated, but the two sets of melted lines were formed on the same surface to intersect diagonally and to produce a repeated diamond-pattern with diagonals of about 2 x 4 inches (5 x 10.2 cm.). As indicated by the square point of FIGURE 6, percent compression at 25 p.s.i. (1.76 kg./cm.2) for this product was about 72.7% and dynamic modulus was about 696 p.s.i. (49.0 kg./ cm.2). While both thickness and dynamic modulus for this specimen were higher than preferred, they could both be altered in obvious fashion. The broad range of properties obtainable in the products of this invention is clearly shown.

EXAMPLE VII This example illustrates the use of cushioning structures according to this invention as the major element in a composite carpet-underlay. The ultramicrocellular filaments employed were prepared as described in Example II. Unlike Example II, however, the filaments were postinflated with peruorocyclobutane impermeant inflatant before formation of the batts, but the same post-inflation bath, at the same conditions, was used, followed by airreinflation for 10 minutes at 120 C. Following this treatment, the filaments contained about 22 grams of perfluorocyclobutane per 100 grams of polymer, corresponding to a partial pressure of 320 mm. of mercury and a total gas pressure within the cells of about 1.42 atmospheres.

An adhesive formulation and a surfactant formulation were separately provided. The adhesive formulation was 3005 antioxidant dispersion (as used in Example II). The surfactant formulation contained parts of the Aquarex@ ME surfactant of Example II, 10 parts of the Daxad II dispersing agent of Example II, parts of #Z2-4 Heliozone Emulsion as supplied by Lukon, Inc. (Heliozone is a registered trademark `of E. I. du Pont de Nemours and Co., Inc., for emulsions of blended petroleum waxes melting between 163 and 170 C. as determined by the drop point method), and 890 parts of distilled water. A single binder composition was prepared by mixing 272 parts of adhesive formulation, 28.2 parts of surfactant formulation, and 625.5 parts of distilled water.

The mold used for consolidating portions of the above filaments `was entirely of metal coated with polytetrafluoroethylene resin. Onto a rigid, expanded metal sheet was placed a 54-mesh screen. Around the margin were placed spacer bars. The portion of filaments was randomly arranged within the box so formed, and then squeezed into the space by another screen and expanded metal sheet combination. Although the filaments were forced to bend around one another to fit the available space, they did not lose their filament identity; and the batt so formed had numerous intercommunicating open channels between filament portions. The above binder composition was air-frothed beneath the mold until its froth had risen up through the batt, where the froth collapsed and tended to collect at the crossings of filament portions. The binder composition was gelled by passing carbon dioxide gas through the batt, and then cured by heating in air at 125 C. for one hour. Removed from the mold, the consolidated batt was 0.33 inch (0.84 cm.) thick, i15%. It was cut to a finished size of 11.25 x 16 inches 1.28.6 x 40.6 cm.).

The consoliated batt was placed in another releaseagent-coated frame, and a 20 to mil (0.5 to 1.5 mm.) layer of wet, open-celled, neoprene froth was doctored on. After l to 2 minutes of gelling time, a thin expandedmetal sheet was placed onto the foam-layer in order to provide a shallow molded pattern. Covered with a flat steel plate, the frame was over, and a neoprene-foam coating was similarly doctored onto the other face of the batt. Drying of the neoprene foam was at 162 C. for 15 mintues. The function of the neoprene-foam surfaces was simply to provide a visually attractive surface. The neoprene foam was produced substantially as described in Neoprene Latex, I. C. Carl, E. I. du Pont de Nemours and Co., Inc., 1962, p. 91. It was based on neoprene T-60 latex (Du Pont), and incorporated various dyes for attractive coloration. The formulation shown was modified by the addition, in the amount of 20 parts per 100 of T-60 latex solids, of PAPI@ polymethylene polyphenylisocyanate as produced by the Carwin Div. of The Upjohn Co. This additive has about 2.7 to 2.8 isocyanato groups per molecule. Among other advantages, this addition imparts very short gel times to the frothed foam and permits of room-temperature curing.

Six carpet-underlay specimens were prepared as described, and their properties are shown in Table III. Specimen code 7 denotes golden-yellow neoprene foam, code 8 denotes white, and code 9 denotes green.

TABLE IIL-ADHESIVELY BONDED UNDERLAY SURFACED WITH NEOPRENE FOAM (l) Percent Compression at Dynamic Sample Latex Neoperene Thickness 25 p.s.i. or at Modulus [p.s.i. (2) No. Total Filament Binder Foam Iinch-(cm.)l 1.76 Lrg/cm.2 (kg./crn.2)] R.M.A.

(l) Obtained using a 4 111.2 (25.8 cm?) round indentor. l (2) R.M.A. is a trade-recognized abbreviation-for the load in pounds on a 50 in.2 (322.6 cm.2) iudentor to produce a 25% decrease 1n thickness. These values were obtained by multiplying the 4 in.2 load by (50/4).

composed of 182.5 parts of Foamtol BGL-9002 latex,

Dynamic modulus versus percent compression for these 10 parts of ITV-2003 curing agent, and 12 parts of FZ- 75 six carpet-underly specimes is indicated by small xs in FIGURE 6. Load-compression behavior for sample No. 7 is shown by curve b of FIGURE 5, and curve a corresponds to sample No. 9. Although not shown, load-compression for sample No. 8 closely approximates curve c. Except for slightly increasing the extent of compression at a given load, the neoprene foam had substantially no effect on the carpet-underlay performance properties. Also suitable for surfacing these carpet underlays are various flexible polyurethane foams. They can either be foamed in place or be adhesively bonded to the surface as foils of previously foamed material.

What is claimed is:

1. A resilient, low-density, web-like cushioning structure, suitable as carpet-underlay, comprised of closedcell, pneumatic, polymeric, cellular material in filamentary form, saidlamentary material being randomly disposed within said structure to provide numerous crossings of lament portions, being consolidated so as to distort lament portions around one another and provide substantial areas of lament-to-lament engagement such that the average ratio of Volume of said lamentary material to total volume of said structure is at least 0.4, and being bonded at least within portions of said structure to permanently retain said consolidated volume, major portions of said tilamentary material having a density of from about 0.008 to 0.06 gm./cc. and containing within the cells thereof about 6 to 40 gm. of an impermeant inflatant per 100 gm. of polymer.

2. Structure according to claim 1 having a thickness of about 0.1 to 1.0 inch and a weight, of lilamentary material only, of about 1.0 to 10 oz./yd.2

3. Structure according to claim 1 in which the cellular material is ultramicrocellular exhibiting uniform texture and uniplanar orientation.

4. Structure according to claim 3 in which the said polymer is polyethylene terephthalate.

5. Structure according to claim 1 in which said impermeant inflatant is selected from the group consisting or' sulfur hexauoride and saturated aliphatic and cycloaliphatic compounds having at least one fluorine-to-carbon covalent bond.

6. Structure according to claim 5 in which said impermeant inatant is perfluorocyclobutane.

7. Structure according to claim 1 wherein said filament portions have a major cross-sectional dimension of about 0.025 to 0.25 inch.

8. Structure according to claim 1 wherein the filamentary material is fusion bonded and densied in a pattern of line elements across and along the structure.

9. Structure according to claim 1 wherein the lamentary material is bonded by an adhesive.

References Cited UNITED STATES PATENTS 3,227,664 l/l966 Blades et al.

2,464,301 3/1949 Francis 161-159 X 3,080,580 3/1963 Tobari 51-361 3,106,507 1'0/1963 Richmond l6l-l78 X 3,179,551 4/1965 Dudas 156-209 X 3,278,954 10/1966 Barhite 161-170 X 3,344,221 9/1967 Moody etal ll-159 X ROBERT F. BURNETT, Primary Examiner L. M. CARLIN, Assistant Examiner U.S. Cl. X.R.

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