US2437689A - Process for making needle felts - Google Patents

Description

Patened Mai- 16,

. 2,437,689 PROCESS FOR MAKING NEEDLE FELTS Carleton 8. Francis, Jr.,

assignor, by mesne assignments. Viscose Corporation, Wilmington,

poration of Delaware West Harwich, Mass., to American Dei., a cor- No Drawing. Original application October 23,

1939, Serial No. 300.876. piication April 11, 1944, Serial No. 530,553

This invention relates, in general, to felted fibrous structures, and, in particular, to a process for producing felts and includes correlated improvements designed to enhance the properties, characteristics and to extend the uses of the felts so produced. This application is a division of my copending application Serial No. 300.876, filed October 23, 1939, which in turn is a continuation-inpart of application Serial No. 157,018, filed August 2, 1937 (now Patent 2,253,000).

It has previously been impractical to make felts from fibres other than wool and like fibres which have a substantial curl and, even more important, a rough surface. When attempts are made to produce felts from smooth-surfaced and relatively straight fibres such as artificial fibres, the products produced invariably lack strength, and in many cases are devoid of any felt structure whatever, because the smooth surface of the fibres and their relatively straight form prevents the fibres from interfelting and clinging together in the manner of wool fibres. Even when artificial fibres have been given an artificial crimp or curl, they do not make satisfactory felts because the smooth-surfaced fibres slide upon one another and are not fixed in position by the felting operation.

It is a general object of the present invention to provide a method for producing felts from relatively smooth surfaced and/or relatively straight fibres.

Another object of the invention is to provide an improved felt from smooth-surfaced and/or relatively straight fibres, such felts having certain desirable characteristics among which are increased strength and greater tenacity between component fibres and improved wet strength.

A specific object of the invention is to provide a shaped felted structure adapted for use as a substitute for woven fabrics and which may be manufactured according to the'invention at less cost and with less expenditure of time than woven fabrics.

Other objects of the invention will in part be obvious and will in part appear hereinafter.

In accordance with the present invention, felts of substantial strength and high tenacity are made from a mixture of normally non-felting fibre and synthetic resin fibres, the non-felting fibres being maintained in a felted condition by the thermal tackiness of the resin fibres. The process of the present invention may be carried out by mixing together normally non-felting fibres with synthetic resin fibres which are nontacky at room temperature, but which become Divided and this ap- 5 Claims. (01- 154-101) tacky below the temperature at which the nonfelting fibres are damaged, felting the mixture of fibres, heating the felted mixture to a temperature at which the resinous fibres become tacky and cooling the felt to effect fibre adhesion. The resin fibres may be rendered tacky during or after the felting operation and the felt is preferably subjected to pressure while the resin is in an adhesive condition. The expression "felt" as used in the specification and claims is intended to include both textile felts and unwoven felted structures formed therefrom. Paper felts are not claimed herein since such felts are claimed in my copending U. 8. application Serial No. 444,438, filed May 25, 1942.

Thus the present invention enables improved felts to be made from various natural or synthetic fibres and filaments which are smooth-surfaced and/or relatively straight and which do not felt readily. Among the natural fibres which may be used are cotton, flax, Jute. kapok, silk, and the like, or they may be synthetic fibres of cellulosic composition, such as a cellulose hydrate, cellulose derivatives, as cellulose esters, mixed cellulose esters, cellulose ethers, mixed cellulose esterethers, mixed cellulose ethers, cellulose hydroxyethers, .cellulose carboxy-ethers. cellulose etherxanthates, cellulose xantho-iatty acids. cellulose thiourethanes; natural and synthetic rubber and derivatives thereof; alginic acid, gelatine, casein; and mineral fibres such, for example, as spun glass, asbestos, mineral wool and the like, and fibres made of natural and synthetic resins which should be of such type that they are not rendered tacky when the potentially adhesive resin fibres are rendered tacky by heating; also fibres and filaments made by slitting, cutting or shredding non-fibrous films, such as waste Cellophane.

The potentially adhesive resin fibre may be composed of a wide variety of materials, and may comprise any synthetic resinous material capable of being formed into fibres which have an inherent tackiness upon heating to a temperature below that at which the non-felting fibres are damaged or rendered tacky and which are nontacky at room temperature such, for example, as

the resins formed by the polymerization of various organic compounds such as coumarone, inclene hydrocarbons, vinyl, styrene, sterol aldehyde, furfural ketones, urea, thiourea, phenolaldehyde resins, either alone or modified with oils, urea-aldehyde resins. amine-aldehyde resins, sulfonamide-aldehyde resins, polyhydric a1oohol polybasic acid resins, drying oil-modified alkyd resins, resins formed from acrylic acid, its homologues and their derivatives, sulfur-oiefine resins, resins formed from dicarboxylic acids and diamines (nylon type); fibres formed from synthetic or artificial rubber such for example as polymerized butadiene, oleflne-polysulfides, e. g. Thiokol. isobutylene polymers, chloroprene polymers and polyvinyl-halides, e. g. Koroseal, fibres formed from a resin comprising the product of co-polymerizing two or more resins, such, for example. as co-polymers of vinyl halide and vinyl acetate, co-polymers of vinyl halide and an acrylic acid derivative, co-polymers or vinyl compound and styrol compound; and also fibres formed from a mixture of resins, such for example as a mixture of vinyl resins and acrylic acid resins or methacrylic acid resins, a mixture of polyolefine resins and phenol-aldehyde resins, or a mixture of two or more resins from the difi'erent classes Just named.

The resins above mentioned may be classified as:

(a) Heat-non-convertible resins such for example as glycol polybasic acid resins, vinyl resins filkld the acid type phenol-aldehyde resins, and the (b) Heat-convertible resins such for example as a glycerol-polybasic acid resin, polyolefine resins, phenol-aldehyde resins and the like.

(c) An element-convertible resin (which becomes infusible through the action of certain elements, such as oxygen and sulfur) such for example as glycerol-polybasic acid-drying oils, resins and olefine sulfur resins.

For felts that are subjected to laundering or dry cleaning, the synthetic resin fibre should be insoluble in water and inert to the detergents used for laundering and dry-cleaning. The resins employed are preferably those which do not soften appreciably at temperatures reached in laundering and blocking" (as in the making of h t f l hough softening during blocking is not objectionable.

In the new preferred embodiment there is used synthetic resin fibre comprising a co-polymer of vinyl acetate and vinyl chloride which fibres are made of suitable methods known in the art. This fibre resembles rayon and is similar thereto in many respects, but it differs therefrom since it becomes tacky when heated to a temperature of from 200 F. to 350 F. When heated, it becomes adhesive to other fibres in contact with it and adheres thereto upon cooling, It is tough and firm at ordinary temperatures, insoluble in water, and inert to the agents used in laundering and drycleaning and shows no substantial decrease in tensile strength on being wetted.

The ratio of synthetic resin fibre to other fibre may also vary widely depending on the properties of the two types of fibres and may be regulated to suit the purpose for which the felt is destined, but in general a minor proportion, preferably from 3 per cent to 20 per cent of the synthetic resin fibre will be employed. Where a greater degree of strength or a closer bonding of the component fibres is desired, the percentage will be relatively high, whereas in felts, such as papers of certain construction where it is desirable to have a comparatively small amount of bonding of the component fibres, the percentage will be relatively small.

The synthetic resin fibre and other fibre have been mixed by a method suitable to the production of a particular type of felt, for example. the fibres may be mixed by carding.

The inherent tackiness of the resin fibres 5 8&-

tivated by heating the felt to an appropriate temperature, for example by the use of ry hot contact with heated surfaces, steam or hot water. The temperature of the heat-treatment will depend on the properties of the synthetic resin fibre and must necessarily be below that at which the felt is damaged. When the felt is cooled, the synthetic resin fibres become non-tacky and tough, and adhere to the other fibres, thus providing a felt which possesses increased strength and greater tenacity between component fibres.

Generally, it is preferred to immerse the felt in water at or approximating the boiling point, as it is found thatthe water carries the heat unlformly through the felt and accordingly reacts on the thermoplastic fibres throughout the entire felt. In certain cases, however, where it is desirable 'to obtain a surface-glazed effect on felts, wherein the thermoplastic fibres are largely exposed on the surface thereof, it may be more desirable to heat the fabric by surface contact with heated metal, such as is practiced in the conventional heated calender, The method of heating may be carried out in whichever manner may be selected tolcon form most'satisfactoriiy with the effect desired in the finished felt.

The tackiness of the resin fibres may be modified by heating the resin fibres in the presence of a suitable plasticizer depending on the particular type of resin. The plasticizer may be incorporated in or carried by the resin fibres and/or by the non-feltable fibres and may be incorporated in the fibres at any point prior to heating. In the preferred embodiment the plasticizer is incorporated in the resin'mass prior to its formation into fibres and filaments. The plasticizer lowers the temperature at which the resin fibres are rendered tacky upon heating. After heating, the plasticizer is preferably removed by suitable means such as evaporation or extraction, thereby preventing the resin fibres from again being rendered tacky at the original activating temperature and rendering them capable of remaining non-tacky at ironing temperatures.

The mixture of fibres may be felted in a predetermined shape by use of a suitable mold, or the felt may be shaped and given a desired form. The shaping takes place in the case of paper felts, preferably by molding or shaping the wet paper sheet. In the case of textile felts, it is preferable to shape the felt after its initial formation and after the thermal activation of the potentially adhesive fibres and while such fibres are in an adhesive condition. The predetermined shape of both paper and textile felts may be permanently set by the deactivation of the adhesive or of the adhesive fibres. By this means there may be produced a wide variety of shaped, felted structures which may be used as substitutes for woven, knitted or netted fabrics and articles made from the same. As the felting and shaping process herein described involves no spinning, weaving, knitting or other similar textile operation, it is obvious that the shaped, felted structures can be produced at a very low cost.

The invention is applicable for making various types of textile felts, such for example as "woven felts, "needle felts and pressed textile felts.

In the case of woven felts the basis is a woven construction having a full na or pile which is felted until the woven structure is obscured. After the woven construction is shrunk and the flap felted in the usual manner, the felt 15 subiected to heat to render the resin fibres the felted nap fibres.

Needle felts are commonly prepared by placing a layer of unfelted fibres on one or both sides of a woven gauze and the fibres drawn partly through the gauze by means of barbed needles, after which the article is pressed. In this embodiment the layer of fibres comprises a mixture of unfeltable fibres and resin fibres. After .the fibres are drawn into the gauze, the felt is subjected to heat and pressure to activate the inherent tackiness of the resin fibres to cause a permanent adhesion of the fibres in the layer and to effect an anchoring of the felted fibres to the gauze base.

The present invention has special application to the manufacture of pressed textile felts such as are used for hats, chair pads, rug cushions.

sound and shock absorbers and the like. In the formation of such felts, a mixture of the unfelta-ble fibres and resin fibres is prepared as by carding and shaped into a layer. The layer of fibres is placed between heavy sheets of fabric, such as canvas, preferably moistened with water and then placed between heated metal plates which are vibrated rapidly when in contact with the enclosed layer, thus causing the fibres to become matted together in a compact layer. If desired'the layer of fibres may now be heated to render the resin fibres tacky and effect a permanent adhesion of the fibres in the felted condition, or this heating step may be carried out at a later time. The layer of felted fibres, before or after heating, may be folded and placed in the usual felting box provided with conventional hammers by which the layer may be pounded to a desired thickness, firmness, length, width, con figuration. etc., after which the felt is heated. if desired, to render the resin fibres tacky and the felt is then finished in the usual manner. For smoothsurfaced felts the layer is run through calenders which may be heated to render the resin fibres tacky.

As an illustrative embodiment of a manner in which the invention may be practiced. the following examples are presented:

Example I A rayon staple may be cut to a length of 1.5 to 2 inches and a resinous fibre as a oil-polymer of vinyl acetate and vinyl chloride may be cut to a corresponding length. The cut fibres may then be mixed in a suitable carding machine in the proportions of about 90% of cut staple rayon and of the resin. A textile felt may then be formed from the mixture in a suitable manner, and the admixture is heated sufilciently to soften the resin. As a rule a temperature of about 200 F. will serve to soften the resinous fibre, and hence such temperature preferably is used. While in a heated, softened condition, the resin fibre becomes adhered to the other fibres surrounding it. causing the fibres to cling together. On cooling, the resinous material becomes solid and non-tacky and tough. although still adhering to the fibre surrounding it. with the result that the fibres are substantially fixed in position. thus imparting strength and the felt.

Since certain changes in carryin out the above process. and certain modifications in the article which embody the invention may be made without departing from its scope. it is intended that all matter contained in the above description maintaining the shape of tacky which effects an adhesion or bonding of shall be interpreted as illustrative and not in a' limiting sense.

The product hereinabove described is the subject matter of a divisional application Serial No. 782,870, filed October 29, 1947, and. entitled Textile product.

Having described my invention, what I claim as new and desire to secure by Letters Patent is: 1. The process of making self-binding fabric having a woven textile base, which consists in mixing non-fusible and fusible fibres into a bat. needle punching the bat upon a textile base, and then subjecting the two plies thus formed to heat and pressure to fuse the latter fibres into an anchoring web on both sides of the textile base. 2. The process of making self-binding fabric containing a prefabricated textile base, which consists in mixing non-adhesive fibres and potentially adhesive fibres, spreading the mixed fibres on one face of the prefabricated base, needle-punching a substantial proportion of said mixed fibres into said base, activating said potentially adhesive fibres to render said potentially adhesive fibres tacky, and deactivating said potentially adhesive fibres to bind said non-adhesive and said potentially adhesive fibres to said base.

3. The process of making self-binding fabric containing a prefabricated textile base, which consists in mixing non-adhesive fibres and thermoplastic fibres, spreading the mixed fibres on one face of theprefabricated base, needlepunching a substantial proportion of said mixed fibres into said base, activating said thermoplastic fibres by the application of heat thereto to render said fibres tacky, and cooling said product to bind said non-adhesive and said thermoplastic fibres to said base. I

4. The process of making self-binding fabric containing a prefabricated textile base. which consists in mixing non-adhesive fibres and thermoplastic fibres into the form of a bat, superposing said hat on one face of the prefabricated base, needle-punching a substantial proportion of the mixed fibres constituting said bat into said base, activating said potentially adhesive fibres by the application of heat thereto to vcontaining a prefabricated textile base, which consists in mixing non-adhesive fibres and thermoplastic fibres, spreading the mixed fibres on one face of the prefabricated base. needlepunching a substantial proportion of the mixed fibres through said base to and beyond the opposite face thereof. subjecting said product to pressure and activating said thermoplastic fibres by the application of heat thereto to render said fibres tacky while the product is under pressure, and cooling said product to bind said non-adhesive and said thermoplastic fibres to said base on said opposite faces respectively thereof.

caamrou s. FRANCIS, in.

sameness orran The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name @Dato 2,232,647 zirkmsn Feb. 18, 1941 2,277,049 Reed Mar. 24, 1042 2,181,048 Boeddinghius Nov. 21, um