Improved Non-Woven Fibrous Product

The present invention relates to an improved non-woven fibrous product and more specifically to a non-woven blanket of mineral and man-made fibers to which thermosetting resin and carbon black may be added. The blanket may be formed into sheets, panels and complexly curved and configured products.

Non-woven fibrous products such as sheets and panels as well as other thin-wall products such as insulation and complexly curved and shaped panels formed from such planar products are known in the art.

In U.S. Pat. No. 2,483,405, two distinct types of fibers therein designated non-adhesive and potentially adhesive fibers are utilized to form a non-woven product. The potentially adhesive fibers typically consist of a thermoplastic material which are mixed with non-adhesive fibers to form a blanket, cord or other product such as a hat. The final product is formed by activating the potentially adhesive fibers through the application of heat, pressure or chemical solvents. Such activation binds the fibers together and forms a final product having substantially increased strength over the unactivated product.

U.S. Pat. No. 2,689,199 relates to non-woven porous, flexible fabrics prepared from masses of curled, entangled filaments. The filaments may be various materials such as thermoplastic polymers and refractory fibers of glass, asbestos or steel. A fabric blanket consisting of curly, relatively short filaments is compressed and heat is applied to at least one side to coalesce the fibers into an imperforate film. Thus, a final product having an imperforate film on one or both faces may be provided or this product may be utilized to form multiple laminates. For example, an adhesive may be applied to the film surface of two layers of the product and a third layer of refractory fibers disposed between the film surfaces to form a laminate.

In U.S. Pat. 2,695,855, a felted fibrous structure into which is incorporated a rubber-like elastic material and a thermoplastic or thermosetting resin material is disclosed. The mat or felt includes carrier fibers of long knit staple cotton, rayon, nylon or glass fibers, filler fibers of cotton linter or nappers, natural or synthetic rubber and an appropriate resin. The resulting mat or felted structure of fibers intimately combined with the elastic material and resinous binder is used as a thermal or acoustical insulating material and for similar purposes.

U.S. Pat. No. 4,612,238 discloses and claims a composite laminated sheet consisting of a first layer of blended and extruded thermoplastic polymers, a particulate filler and short glass fibers, a similar, second layer of a synthetic thermoplastic polymer, particulate filler and short glass fibers and a reinforcing layer of a synthetic thermoplastic polymer, a long glass fiber mat and particulate filler. The first and second layers include an embossed surface having a plurality of projections which grip and retain the reinforcing layer to form a laminate.

It is apparent from the foregoing review of non-woven mats, blankets and felted structures that variations and improvements in such prior art products are not only possible but desirable.

The present invention relates to a non-woven blanket or mat consisting of a matrix of mineral fibers and man-made fibers. The mineral fibers are preferably glass fibers and the man-made fibers may be polyester, rayon, acrylic, vinyl, nylon or similar synthetic fibers. A thermosetting resin bonds the fiber matrix together. A conductive material such as copper or aluminum powder or a conductive/coloring agent such as carbon black assists static dissipation during manufacture resulting in a product with improved surface finish. Alternatively, the conductive material may be in the form of fibers.

The product consists essentially of fiberized glass fibers of three to ten microns in diameter. Such fibers, in an optimum blend, comprise 62% of the resulting product. The synthetic fibers may be selected from a wide variety of materials such as polyesters, nylons, rayons, acrylics, vinyls and similar materials. Larger diameter and/or longer synthetic fibers typically provide more loft to the product whereas smaller diameter and/or shorter fibers produce a denser product. The optimum proportion of synthetic fibers is approximately 21%.

A thermosetting resin is utilized to bond the fibers together. The thermosetting resin preferably includes a conductive material such as copper or aluminum powder or a conductive/coloring agent such as carbon black. The thermosetting resin may be selectively activated to bond primarily only those fibers adjacent one or both faces of the blanket, partially activated throughout the blanket or activated throughout the blanket, if desired. The optimum proportion of the thermosetting resin and conductive material is approximately 17%. If desired, a foraminous or imperforate film or skin may be applied to one or both surfaces of the blanket during its manufacture to provide relatively smooth surfaces to the product.

The density of the product may be adjusted by adjusting the thickness of the blanket which is initially formed and the degree to which this blanket is compressed during subsequent forming processes. Product densities in the range of from 1 to 50 pounds per cubic foot are possible.

It is therefore an object of the present invention to provide a non-woven matrix of glass and synthetic fibers having a conductive material dispersed therethrough and adhered together by a thermosetting resin.

It is a still further object of the present invention to provide a non-woven matrix of glass and synthetic fibers having a conductive material and thermosetting resin dispersed therethrough wherein said thermosetting resin may be differentially activated through the thickness of the matrix to provide layers of distinct rigidity.

It is a still further object of the present invention to provide a non-woven matrix of glass and synthetic fibers having a conductive material and thermosetting resin dispersed therethrough wherein said thermosetting resin may be uniformly partially activated throughout the product.

It is a still further object of the present invention to provide a non-woven matrix of glass and synthetic fibers having a conductive material and thermosetting resin dispersed therethrough and a skin or film on one or both surfaces of the matrix.

It is a still further object of the present invention to provide a non-woven matrix of glass, synthetic fibers, thermosetting resin and conductive material which has its strength and rigidity adjusted by the degree of activation of the thermosetting resin.

Further objects and advantages of the present invention will become apparent by reference to the following description of the preferred and alternate embodiments and appended drawings.

FIG. 1 is an enlarged, diagrammatic, plan view of a non-woven fiber matrix according to the present invention;

FIG. 2 is an enlarged, diagrammatic, side elevational view of a non-woven fiber matrix according to the present invention with unactivated thermosetting resin;

FIG. 3 is an enlarged, diagrammatic, side elevational view of a non-woven fiber matrix product according to the present invention in which the thermosetting resin is partially differentially activated;

FIG. 4 is an enlarged, diagrammatic, side elevational view of a non-woven fiber matrix product according to the present invention in which the thermosetting resin is partially homogeneously activated;

FIG. 5 is an enlarged, diagrammatic, side elevational view of a non-woven fiber matrix product according to the present invention in which the matrix is significantly compressed and the thermosetting resin is fully activated;

FIG. 6 is an enlarged, fragmentary, diagrammatic, side elevational view of a non-woven fiber matrix product according to the present invention having a film disposed on one surface thereof;

FIG. 7 is an enlarged, fragmentary diagrammatic, side elevational view of a non-woven fiber matrix product according to the present invention having a film disposed on both surfaces thereof; and

FIG. 8 is an enlarged, fragmentary diagrammatic, side elevational view of a first alternate embodiment of a non-woven fiber matrix product according to the present invention in which the conductive material is in the form of fibers and which includes a film dispersed on a surface thereof.

Referring now to FIG. 1, a non-woven fibrous blanket which comprises a matrix of mineral and man-made fibers according to the present invention is illustrated and generally designated by the reference numeral 10. The non-woven fibrous blanket 10 comprises a plurality of first fibers homogeneously blended and dispersed through a plurality of second fibers 14 to form a generally interlinked matrix. The first fibers 12 are preferably mineral fibers, i.e., glass fibers. Preferably, such fibers 12 are substantially conventional virgin, rotary spun, fiberized glass fibers having a diameter in the range of from 3 to 10 microns. The fibers are utilized in a dry, i.e., non-resinated, condition. The length of the individual fibers 12 may vary widely over a range of from approximately one half inch or less to approximately 3 inches and depends upon the shredding and processing the fibers 12 undergo which is in turn dependent upon the desired characteristics of the final product as will be more fully described subsequently.

The second fibers 14 are man-made, i.e., synthetic, and may be selected from a broad range of appropriate materials. For example, polyesters, nylons, Kevlar or Nomex may be utilized. Kevlar and Nomex are trademarks of the E. I. duPont Co. for their organic aramid fibers which are members of the aromatic polyamide family. The second fibers 14 preferably define individual fiber lengths of from approximately one quarter inch to four inches. The loft/density of the blanket 10 may be adjusted by appropriate selection of the diameter and/or length of the synthetic, second fibers 14. Larger and/or longer fibers in the range of from 5 to 15 denier (approximately 25 to 40 microns) and one to four inches in length provide more loft to the blanket 10 and final product whereas smaller and/or shorter fibers in the range of from 1 to 5 denier (approximately 10 to 25 microns) and one quarter to one inch in length provide a final product having less loft and greater density. The second fibers 14 may likewise be either straight or crimped, straight fibers providing a final product having less loft and greater density and crimped fibers providing the opposite characteristics.

The first, glass fibers 12 and second, synthetic fibers 14 are shredded and blended sufficiently to produce a highly homogeneous mixture of the two fibers. A uniform mat or blanket 10 having a uniform thickness is then formed and the product appears as illustrated in FIG. 1. Typically, the blanket will have a thickness of between about 1 and 3 inches although a thinner or thicker blanket 10 may be produced if desired.

Referring now to FIG. 2, the blanket 10 also includes particles of a thermosetting resin 16 dispersed uniformly throughout the matrix comprising the first, glass fibers 12 and the second, synthetic fibers 14. The thermosetting resin 16 may be one of a broad range of general purpose, engineering or specialty thermosetting resins such as phenolics, aminos, epoxies and polyesters. The thermosetting resin 16 functions as a heat activatable adhesive to bond the fibers 12 and 14 together at their points of contact thereby providing structural integrity, and rigidity as well as a desired degree of resiliency and flexibility as will be more fully described below. While the quantity of thermosetting resin 16 in the blanket 10 directly affects the maximum obtainable rigidity, the portion of such resin which is activated affects the density and loft as well.

The control of density and loft in this manner is a feature of the present invention and the choice of thermosetting resins 16 is one parameter affecting such characteristics. For example, shorter flowing thermosetting resins such as epoxy modified phenolic resins which, upon the application of heat, quickly liquify, generally rapidly bond the fibers 12 and 14 together throughout the thickness of the blanket 10. Conversely, longer flowing, unmodified phenolic resins liquify more slowly and facilitate differential curing of the resin through the thickness of the blanket 10 as will be described more fully below.

The blanket 10 also includes a conductive material 18 dispersed uniformly throughout the matrix comprising the first, glass fibers 12 and the second, synthetic fibers 14. The conductive material 18 may be in either fibrous or a particulate form. If the conductive material 18 is in particulate, i.e. powder form, the particles of conductive material 18 may be mixed with the fibers 12 and 14, or mixed with the thermosetting resin 16 prior to application to the blanket 10 or the resin 16 and the particles 18 may be applied to the blanket 10 separately. Alternatively, if in the form of fibers, the conductive material 18 may be blended with the first, glass fibers 12 and the second, synthetic fibers 14 at the time the fibers are blended and formed into the blanket 10 as illustrated in FIG. 8 and described below.

The particles of conductive material 18 may be powdered aluminum or copper or carbon black. Other finely divided or powdered conductive materials, primarily metals, are also suitable. The carbon black may be like or similar to Vulcan P or Vulcan XC--72 fluffy carbon black manufactured by the Cabot Corporation. Vulcan is a trademark of the Cabot Corporation. Pelletized carbon black may also be utilized but must, of course, be pulverized before its application to the blanket 10 or mixing with the thermosetting resin 16 and application to the blanket 10.

The conductive material 18, if in particulate form and especially if it is carbon black, changes the appearance of an improved product 20, illustrated in FIG. 3, from its natural tan color through grey to silvery black and black depending upon the relative amount of carbon black added to the product 20. This color shading and particularly the choice of the degree of shading is advantageous in the automotive product market and in applications where the product 20 must be inobtrusive and/or blend with dark surroundings. Automobile hood liners and similar products are ideal applications for the product 20 which has been darkened by the inclusion of carbon black.

The incorporation of conductive material 18 into the blanket 20 also improves the surface uniformity and thus appearance of the product 20. This is apparently the result of the draining off or dissipating of static electrical charges generated during the mixing of the fibers 12 and 14 and forming of the blanket 10. The improved product 20 containing conductive material 18 exhibits greatly reduced wrinkles and other surface imperfections.

The following Table I delineates various ranges as well as an optimal mixture of the two fibers 12 and 14, the thermosetting resin 16 and the conductive material 18 discussed above. The table sets forth weight percentages.

Referring now to FIG. 3, one manner and result of partial activation of the thermosetting resin 16 is illustrated. Here differential activation that is, activation of the thermosetting resin 16 in relation to the distance from one face of the blanket 10 will be described. As noted, one of the features of the present invention is the adjustability of the rigidity, density and thickness of the product 20 to either match the requirements of a given application or match, i.e., anticipate, those of secondary processing associated with the production of modified, final products.

In FIG. 3, the product 20 illustrated includes the first fibers 12, the second fibers 14 and the conductive material 18. The fibers 12 and 14 have been bonded together in the lower portion 20A of the product 20 by activation of the thermosetting resin 16 as illustrated by the bonded junctions 22. In contrast to the lower portion 20A, is the upper portion 20B of the product 20, wherein the thermosetting resin 16 has not been activated. Such partial differential activation of the thermosetting resin 16 is accomplished by the application of heat, radio frequency energy or other appropriate resin related activating means such as a chemical solvent only to the lower surface 24 of the product 20.

The resulting product exhibits substantially maximum obtainable rigidity and strength in one portion (20A) of its thickness and minimum rigidity and strength in the remaining portion (20B) of its thickness. Thus the lower, activated portion 20A serves as a substrate of controlled rigidity which lends structural integrity to the product and facilitates intermediate handling prior to secondary forming of the product 20 into a final product having fully activated thermosetting resin 16 and concomitant increased structural integrity. It will be appreciated that the relative thicknesses of the initially activated portion 20A and unactivated portion 20B of the blanket 10 may be varied in a complementary fashion from virtually nothing to the full thickness of the blanket 10, as desired.

Referring now to FIG. 4, a second manner and result of partial activation of the thermosetting resin 16 is illustrated. In this product 20', partial homogeneous activation of the thermosetting resin 16, that is, partial activation of the thermosetting resin 16 throughout the blanket 10, will be discussed. The product 20' likewise includes first, glass fibers 12, second, synthetic fibers 14 and the conductive material 18. The fibers 12 and 14 have been partially bonded together by substantially uniform, though partial, activation of the thermosetting resin 16 throughout the blanket 10. Such partial, homogeneous activation is preferably and more readily accomplished with longer flowing resins and careful control of heat or other resin activating agents. The portion of thermosetting resin initially activated in this manner may be varied as desired. The portion of the thermosetting resin 16 activated will be determined by considerations of required or permitted structural integrity of the product 20', for example.

The products 20 and 20' so produced exhibit several unique characteristics. First of all, their strength and rigidity are related to the strength and rigidity of a fully cured (thermosetting resin fully activated) product in direct proportion to the percentage of activated thermosetting resin 16. Thus, a desired rigidity may be achieved by selective application of heat or other means to activate a desired proportion of the thermosetting resin 16 to provide a desired proportion of bonded junctions 22 within the product 20. Secondly, both the products 20 and 20' facilitate secondary processing and final forming of the products 20 and 20' into complexly curved and shaped panels and other similar products. That is, the activated thermosetting resin 16 and junctions 22 provide interim, minimal strength whereas the unactivated regions are still flexible, thereby not rendering the products 20 and 20' overly rigid and creating difficulties with inserting the products 20 and 20' into a final mold while still providing necessary material and bulk for the final product. For example, automobile headliners and other sound and heat insulating complexly shaped panels may be readily formed from the product 20 or 20'.

Referring now to FIG. 5, a product 30 including the first, glass fibers 12, second, synthetic fibers 14 and particles of conductive material 18 is illustrated. Here, all of the thermosetting resin 16 has been activated by heat or other suitable agents. Thus, the bonded junctions 22 appear throughout the thickness of the product 30. Since the thermosetting resin 16 is fully activated in the product 30 illustrated in FIG. 5, it is generally considered that the product 30 is finished and will likely be utilized in this form. The product 30 typically will be planar and could be utilized as a sound absorbing panel in thicknesses from one sixteenth to one and one half inches for acoustical treatment of living spaces or other similar heat or sound insulating or absorbing functions.

It should be understood that when the product 20 illustrated in FIG. 3 or the product 20' in FIG. 4 are subsequently processed by heat, molding or other appropriate steps to fully activate the previously unactivated portion of the thermosetting resin 16, they will appear substantially the same as or identical to the product 30 illustrated in FIG. 5.

Another variant of the product according to the present invention is illustrated in FIG. 6. Here, a product 34 including first, glass fibers 12, second, synthetic fibers 14, the particles of conductive material 18 and the thermosetting resin 16, further includes a thin skin or film 36. Preferably, though not necessarily, the film 36 is adhered to one surface of the product 34 by a suitable adhesive layer 38. The film 36 preferably has a thickness of from about 2 to 10 mils and may be any suitable material such as spunbonded polyester, spunbonded nylon as well as a scrim, fabric or mesh material of such substances. The skin or film 36 may be either foraminous or imperforate as desired. The prime characteristics of the film 36 are that it provides both a supporting substrate and a relatively smooth face for the product 34, which is particularly advantageous if it undergoes primary and secondary activation of the thermosetting resin 16 as discussed above with regard to FIG. 3. It is preferable that the skin or film 36 not melt or become unstable when subjected to the activation temperatures or chemical solvents associated with curing the thermosetting resin 16 into the junctions 22. It should be well understood that the skin or film 36, though illustrated on a product 34 having fully activated thermosetting resin 16, is suitable, appropriate and desirable for use with a product such as the products 20 and 20' illustrated in FIGS. 3 and 4 which are intended to and undergo primary and secondary processing and activation of the thermosetting resin 16 as described above.

With reference now to FIG. 7, another product 34' is illustrated. Here, a non-woven matrix of first, glass fibers 12, second, synthetic fibers 14, the thermosetting resin 16 and the conductive material 18 is covered on both faces with thin skins or films 36. The films 36 are identical to those described directly above with regard to FIG. 6. Adhesive layers 38 may be utilized to ensure a bond between the fiber matrix, as also described above. The thermosetting resin 16 has been cured to form the junctions 22. It will be appreciated that either of the products 34 or 34' having one or two surface films 36, respectively are intended to be and are fully suitable and appropriate for partial differential or partial homogeneous activation of the thermosetting resin 16, as described above with reference to FIGS. 3 and 4, respectively.

Referring now to FIG. 8, a first alternate embodiment product 40 of the product 20 and variants 20', 34 and 34', described above, is illustrated. The alternate embodiment product 40 includes first, glass fibers 12, second, synthetic fibers 14, the thermosetting resin 16 which has been activated to form the junctions 22 and the conductive material 18. In the first alternate embodiment 40, the conductive material 18 is in the form of fibers 42. The fibers of conductive material 18 may be carbon or graphite fibers or metals such as copper or aluminum capable of being drawn or formed into small diameter fibers. Typically, the fibers 42 will be blended with the first, glass fibers 12 and second, synthetic fibers 14 such that they become an integral part of the matrix as illustrated in FIG. 8 and are thus uniformly dispersed throughout the alternate embodiment product 40. As illustrated in FIG. 8, the alternate embodiment product 40 also includes a film or skin 36 disposed on one surface. Preferably, though not necessarily, the film 36 is adhered to the product 40 by a suitable adhesive layer 38.

It should be understood that the alternate embodiment product 40 containing conductive fibers 42 may also include a second skin or film 36 (not illustrated) such that the product will appear quite similar to the product 34' illustrated in FIG. 7 or have no skin or film and thus appear quite similar to the products 20, 20' and 34. Likewise, it should be understood that the various resin activation schemes described above in relation to the products 20, 20', 34 and 34' are fully applicable to and functional with the alternate embodiment product 40 with no, one or two skins or films 36.

The activation of the thermosetting resin 16, as generally described in relation to FIGS. 3, 4, 5, 6, 7 and 8 is preferably accomplished by heat inasmuch as partial activation of the thermosetting resin 16 is more readily and simply accomplished thereby. However, as noted, activation means such as radio frequency energy, chemical solvents and the like functioning to cure various types of thermosetting resins 16 are suitable and within the scope of the present invention. With regard to temperature activation of the thermosetting resins, fast curing resins typically are activated at relatively high temperatures of about 300-400.degree. Fahrenheit and above. In situations where partial activation of the thermosetting resin is desired such as that illustrated in FIGS. 3 and 4, slower curing, unmodified phenolic resins typically require temperatures of between about 200.degree. and 300.degree. Fahrenheit applied to one or both faces of the product 20, as desired.

In summation, it will be appreciated that the present invention provides a non-woven fibrous product consisting of a matrix of glass and synthetic fibers having a thermosetting resin and particles of a conductive material dispersed therethrough. The conductive material provides a surface finish which is significantly smoother when compared to similar products which do not include it. If the conductive material is carbon black or other material having significant coloring effect, the appearance of the product may be altered. As indicated above, carbon black, depending upon its mixed proportion, will alter the color of the product from tan, through grey to black. One surface of the product may include and be defined by a film such as a foraminous or imperforate film or plastic mesh or fabric. In a product which either includes or excludes the film, the thermosetting resin may be partially activated through the thickness of the product to provide in a initial product having minimal rigidity and structural integrity but which is not so rigid as to inhibit placement and subsequent final forming in a complexly curved mold. During the final forming, the remainder of the thermosetting resin is activated and the product takes on increased rigidity. The proportion of thermosetting resin initially activated may be varied as desired. Furthermore, the thermosetting resin in surface adjacent regions of both faces of the product may be activated with the appropriate application of heat to render a medial, i.e. center, section unactivated, if desired.

The product in its final form, which will typically include fully activated thermosetting resin such as those products illustrated in FIGS. 5, 6, 7 and 8, though relatively rigid, exhibits sufficient resiliency and flexibility that it may be relatively sharply bent without damaging the fiber matrix. The product will thus return undamaged to its original position and condition. This feature is a function of the interlinked fiber matrix and the flexibility provided primarily by the synthetic fibers. Flexibility of the final product is increased by increasing the proportion of a synthetic fibers and increasing the length of the synthetic fibers as well. On the other hand, the rigidity of the final product is increased by increasing the proportion of the thermosetting resin, the proportion of glass fibers and compressing the final product to have relatively high density. The density of the final product may be adjusted by such means to between 1 and 50 pounds per cubic foot.

The foregoing disclosure is the best mode devised by the inventors for practicing this invention. It is apparent, however, that products incorporating modifications and variations will be obvious to one skilled in the art of fiber matrix products. Inasmuch as the foregoing disclosure is intended to enable one skilled in the pertinent art to practice the instant invention, it should not be construed to be limited thereby but should be construed to include such aforementioned obvious variations and be limited only by the spirit and scope of the following claims.