US3523861A - Nonwoven liner material and method of making same - Google Patents

Description

Aug. 11, 1970 N. s. NEWMAN ErAL 3,523,861

NQNWOVEN L INER MATERIAL AND METHOD OF MAKING SAME.

Filed Dec. 20, 1966 FIG 2 United States Patent Office 3,523,861 Patented Aug. 11, 1970 3,523,861 NONWOVEN LINER MATERIAL AND METHOD OF MAKING SAME Nicholas S. Newman, West Newton, Mass., assignor to The Kendall Company, Boston, Mass., a corporation of Massachusetts Filed Dec. 20, 1966, Ser. No. 603,226 Int. Cl. D04h N58 US. Cl. 161-151 8 Claims ABSTRACT OF THE DISCLOSURE An unspun and unwoven array of textile-length fibers or blend of such fibers is lightly needled until a portion of the fibers have been reoriented into closer mechanical engagement with each other. This array of fibers is brought into contact, under heat and pressure, with the surface of a transiently thermoplastic film capable of becoming thermoset when heated, adhesive being effected along only a portion of the lengths of the fibers.

This invention relates to nonwoven fabrics, and more particularly to nonwoven lining or interlining material comprising a needled array of textile-length fibers bonded to a conformable film.

Textile fibers as delivered by a card, garnett, or air-lay machine are customarily arrayed in a web or fleece wherein the thickness of the fleece is only a fraction of the fiber length, so that the principal fiber axis lies in a more or less horizontal plane. The fibers may be predominantly parallelized or randomly oriented within that horizontal plane.

Various methods of unifying such fibrous arrays, to form nonwoven fabrics, are practiced, the most common being that of impregnating the array with a polymeric binder to form a so-called bonded nonwoven fabric. Such products have a wide utility in the industrial and consumer product fields, but due to certain deficiencies in pliability and conformability, coupled with their undesirable high density and lack of loft or insulating value, bonded nonwoven fabrics have not found wide acceptance in the field of liners or interliners for garments.

In order to provide nonwoven fabrics which are soft and felt-like, therefore, it is common practice to subject fibrous arrays to a needling operation, as in a needle loom, whereby barbed needles descending perpendicularly to the principal plane of the fibers will grasp a certain proportion of the fibers and forcibly reorient them in a direction more or less normal to their original horizontal orientation. The affected fibers are packed together into aggregated configurations which have been called ligations. This operation lends a degree of strength to the fibrous array, while maintaining loft and softness if the needling operation is not too severe.

The strength thus provided, however, is due to a purely mechanical entanglement of the fibers. Since the majority of the fibers in a lightly-needled fleece are either unaffected or only slightly affected by the needling, lightlyneedled fleeces have low abrasion resistance, and shed fibers rather readily when subjected to friction. If attempts are made to overcome this by repeated needlings, it is found that increased fiber anchorage is indeed attained, but at the expense of increased compactness and density of the fabric, and decreased conformability, softness, and insulating value.

Other expedients which have been resorted to in order to achieve better fiber anchorage include back-coating the needled fleece with a binder: flash-heating certain fibrous arrays to effect thermal bonding; and spraying the fleece with a solvent or with a latent solvent which is subsequently activated. All such expedients have undesirable aspects of either wet processing and the need for drying; possible fire hazard; or the known hazards of solvent spraying. It is with improvements in the art of producing soft, conformable, needled nonwoven fabrics, suitable for interlinings, that the present invention is concerned, and a method of producing such nonwoven fabrics is the primary object of the invention.

It is also an object of this invention to provide a method of treating a needled nonwoven fabric so that its tensile strength is increased, while its elongation is decreased without a substantial decrease in conformability.

It is a further object of the invention to provide a needled nonwoven fabric which can be napped without destruction or excessive fiber loss.

Other objects of the invention will be more readily understood from the following description and drawing, in which FIG. 1 represents an apparatus suitable for carrying out the process of this invention FIG. 2 is an enlarged cross-sectional view of a product of this invention.

The present invention comprises the steps of:

(1) Forming a fleece or batt of textile-length fibers on a fiber-arranging device.

(2) Lightly needling the fibrous array in a needle-loom.

(3) Bringing the needled fibrous array into face-to-face contact with one surface of a transiently thermoplastic film while the surface of said film is in an adhesive condition.

(4) Combining the needled fibrous array with the film by means of heat and pressure.

(5) Post-heating the assembly to convert the film to a thermoset condition.

By textile-length fibers is meant those which are long enough to be handled satisfactorily on dry-process fiberassembling textile machines, such as cards, garnetts, air-lay machines and the like. In general, the average fiber length is one-half inch or greater. The particular type of fiber used will depend on the use to which the nonwoven fabric is put, and on economics. Cotton, wool, rayon, polyamide, polyester, polyacrylic, and modified acrylic fibers, or blends thereof are suitable fibers of choice. When synthetic fibers are used, it is frequently convenient to use a blend of fibers of different deniers, to get a combination of high cover factor and high loft.

The needling operation is conventional, as in a Hunter Needle Loom, and needs no further description here except to indicate that for maximum insulating and cushioning value, the preferred products of this invention are subjected to not more than to 300 needlings per square inch.

The particular types of film with which the needled fibrous array is brought into contact are those which have a temperature range within which they are tacky and adhesive, but which contain cross-linking reactants so that on heating or curing at elevated temperatures, the film becomes irreversibly set and cannot be reverted to a plastic condition. Such films at room temperature or somewhat above partake of the natureof thermoplastic films, and will for convenience be called herein transiently thermoplastic.

One type of such films particularly useful in the practice of this invention is a modified acrylic film supplied by Rohm and Haas under the trademark Oroform. This film is tacky and plastic at room temperature, flowing readily under modest heat and pressure. If heated to 300 F. or higher, the film cross-links internally and becomes thermoset. Subsequent to such a heat-setting or curing process, the film is quite thermostable, withstanding prolonged exposure to temperatures of 300 F. and over. It will yellow slightly in one minute at 400 F., but does not melt or decompose to an adverse degree even at higher temperatures.

For a description of a suitable process for producing the products of this invention, reference is made to FIG. 1, wherein a' supply of transiently thermoplastic film 10 is drawn from a supply roll 12, said film being mounted on a backing of release paper 13. The release paper is desirable due to the soft and somewhat adhesive nature of films of this type: its use is well known to those skilled in the film art and will not be elaborated upon here. From the supply roll the film upon its release paper passes to the nip formed by a pair of calender rolls, heated, one roll conveniently being of steel or other metal and the other of a resilient composition such as fiber or husk. At the nip, the semi-adhesive film is combined with a lightly needled nonwoven fabric 14, from a conventional supply roll 16.

At the calender nip the needled nonwoven fabric and the semi-adhesive film are forced by pressure into intimate contact, as explained more fully in connection with FIG. 2. If the temperature in the calender rolls is 400 F. or over and the contact time is prolonged, the conversion of the film from a thermoplastic to a thermoset condition may occur in the calendering operation. For speed in processing, however, it is preferred to have the calender operate at 300-350 R, which unites the film and the needled web, and to effect the conversion of the film to a thermoset condition in a subsequent heating stage 22, which may be a heated oven, a bank of infra-red lamps, or the like. From this curing stage the film-fabric combination passes to a wind-up roll 26, while the release paper, separating from the film at the calender nip, is recovered at the wind-up roll 24.

A typical product of the invention is shown considerably enlarged at FIG. 2, wherein a lightly-needled nonwoven fabric 40 is shown adhering to a now-thermoset film 42. It is characteristic of the economies of this invention that although the film layer in the final product is not thermoplastic or temperature-sensitive, during the combining operation no added adhesive layer on the film is necessary to secure a satisfactory bond between fibers and film.

The internal resistance to delamination, which manifests itself in minimal fiber shedding, is a result in part of the fact that needled tufts of fibers or ligations, 44, are firmly embedded in the film substance at their lower extremities. An even more significant factor, however, is that a substantial number of the fibers which have escaped being engaged in the needling process, as at 46, have been pressed down onto the surface of the film during the calendaring operation and have become firmly adherent thereto along a portion of their length. The fibers are therefore not only mechanically engaged at intervals by needling, but a large proportion of them are adhesively bonded to the base film, and therefore resist abrasion.

- One specific embodiment of the present invention is illustrated in the following example.

EXAMPLE I By means of a cross-lay device, a fibrous fleece was prepared from 1.5 inch long acrylic fibers, 50% 3 denier, 40% 5 denier, and 8 denier. The fleece was lightly needled in a Hunter needle loom at a rate of 260 needle penetrations per square inch. The original weight of the fleece, 180 grams per square yard, dropped to 140 grams per square yard in the needling process.

In an apparatus arrangement similar to that of FIG. 1, the needled fleece was superimposed up on a breathable, tacky Oroform C-16 film, supported on release paper. The laminar combination was then passed through a nip formed by a fiber-filled roll and a steel roll heated to 280 F., at a pressure of 1,000 pounds per inch of nip width (total journal ram pressure divided by width of nip). The film portion of the laminate was then cured to a thermoset condition by heating the combination to 320 F. for one minute in an oven.

The interaction between film and fabric is shown by the following physical constants:

Tensile strength, lbs. Elongation, percent The thickness of the final product was about A inch, and the apparent density of the nonwoven portion (weight divided by unloaded volume) was 0.11 grams per cubic centimeter, compared with an absolute density for acrylic fibers of 1.17 grams per cubic centimeter.

As mentionedabove, theproducts of this inventionare suitable for use as garment liners, on account of their insulating value. The insulating value of a liner material is related to the free air spaces between the fibers, and is therefore inversely proportional to the density of the fibrous mass. In the preferred embodiments of this invention, the combined effects of needling and adhesive bonding are such that 'the' unloaded fibrous product has an apparent density not greater than 20% of the absolute density of the substance. Thus, for viscose rayon fibers with an absolute density of about 1.5 grams per cubic centimeter, the density of the final product is preferably not more than 0.3 grams per cubic centimeter. It is difficult, if not impossible, to maintain such a low fiber density either by needling or film-bonding alone, and simultaneously maintain adequate tensile strength.

The unexpected interaction between film and fiber is also shown by considering the way in which each suppresses the elongation of the other. Both the film and the nonwoven fabric had an elongation at break in the machine direction of over which indicates a lack of stability and retention of shape for lining purposes. By embedding a substantial portion of the fibers into the surface of the film substance by the process of this invention, the elongation at break of the combination is only a small fraction of the elongation of the separate components, and the enhanced stability of the product makes it suitable for use as a garment liner.

The degree of embedment of the fibers of the nonwoven fabric is attested by the fact that the product of Example I can be napped on commercial napping equipment, doubling its apparent thickness, without objectionable fiber loss or damage to the integrity of the structure.

In the preferred products of my invention, the bonding of the fibers to the film is effected solely by film substance, but minor amounts of added binder may be used without substantially detracting from the utility of the products.

Having thus described my invention, I claim: 1. A soft, conformable nonwoven fabric suitable for garment lining purposes which comprises:

an unspun and unwoven array of textile-length fibers in combination with a thermoset film,

a portion only of said fibers being needled into mechanical engagement with each other by subjecting said fibers to not more than to 300 needle punches per square inch,

certain fibers from said portion as well as certain of the other fibers being adhesively bonded to the surface of said thermoset film along a portion only of their lengths,

the adhesive bonding of said fibers being derived essentially from said film substance.

2. The product according to claim 1 in which the fibers are distributed isotropically. 3. The product according to claim 1 in which the fibers comprise a blend of man-made fibers of different deniers.

4. The product according to claim 1 in which the density of the fibrous portion of the product is not greater than one-fifth of the absolute density of thefibers.

5. The product according to claim 1 in which the thermoset film comprises a cross-linked acrylic polymer.

6. The process of making a soft, conformable nonwoven fabric suitable for garment lining purposes which comprises forming an unspun and unwoven array of textile-length fibers.

lightly needling said fibrous array by subjecting said fibers to not more than 150 to 300 needle punches per square inch,

superimposing said array on a transiently thermoplastic film capable of becoming thermoset on heating,

and uniting along a portion only of their lengths a substantial portion of said fibers to the surface of said film by heat and pressure.

7. The process of claim 6 in which the extent of the needling operation is not over 300 penetrations per square inch.

8. The process according to claim 6 in which the film is a cross-linkable acrylic film with a tacky, adhesive surface at room temperature,

said film being capable of becoming non-tacky and heat-set at elevated temperatures.

References Cited UNITED STATES PATENTS 3,206,351 9/1965 Smith 16180 3,282,771 11/1966 Goodman et a1 161151 3,348,992 10/ 1967 Cochran 16166 OTHER REFERENCES Union Carbide Technical Int., UCAR Latex 893, June, 1966 (Class 161Acrylic Resin Digest).

ROBERT F. BURNETT, Primary Examiner R. L. MAY, Assistant Examiner US. Cl. X.R. 156-148, 306

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