US2517724A - Cushion pad and method of manufacture - Google Patents

Description

Aug. 8, 1950 c. H. SCHUH CUSHION PAD AND METHOD OF MANUFACTURE Filed May 29, 1945 b %m r. 0 f e a ge .m .I l

Porous composite of short length fibers,granular material and binder Aqueous slurry prepared Water drained off and porous matrix obtained Matrix dried Dried matrix partially crushed to loosen bonds between solid materials and render matrix softer and resilient Partially crushed matrix coated with an elastomer ATTORNEY Matrix heated Patented Aug. 8, 1950 CUSHION PAD AND METHOD OF MAN UFACTURE Charles H. Schuh, St. Petersburg, Fla., assignor, by mesne assignments, to Union Carbide and Carbon Corporation, a corporation of- New York Application May 29, 1945, Serial No. 596,599

18 Claims. 1

This invention relates to light-weight highly resilient compositions and more specifically to cushion pads. Such pads will be used for illustrative purposes in the following description of the invention.

Resilient pads have a wide variety of uses, kneeling mats being a familiar example. Pads of suitable size and shape are also used in large quantities at present for the packing of shells and the objects of the present invention are a low cost pad and composition therefor which are resistant to deterioration, for instance deterioration due either to loss of resiliency or to external influences. Other uses of the composition and of sheets, mats or pads made therefrom are as protective cushions in the packaging of glassware, for instance carboys and the like, and for machinery vibration dampening, seat cushions, rug cushions, and similar articles.

In Pamnt No. 2,156,309, issued May 2, 1939, in the name of Charles Schuh, there is described a method of producingcompressed products in which a fine, powdered material and a combined filter aid and medium of extension are mixed in a, dilute aqueous dispersion containing a binder; filtered; compressed somewhat while wet; and dried. According to said patent, the combined filter aid and medium of extension may, for instance, comprise finely-pulped newspaper or wood pulp, the binder may comprise latex or an aqueous resin or wax dispersion and the powdered material may comprise regranulated cork or cork bark. According to copending application Serial No. 457,958, filed September 11, 1942, now Patent No. 2,382,448, issued August 14, 1945, in the name of Charles Schuh, the powdered material may comprise palmetto pith. The compositions prepared in accordance with said patents, although normally of light weight, have relatively little resilience compared, for example, to rubber.

In the preferred practice of the present invention a composition of powdered material, combined filter aid and, medium of extension, and binder are thoroughly mixed in a dilute aqueous dispersion, dewatered under only slight compression, and dried in accordance with the processes of said patents. However, after drying, the compositions are subjected to considerable pressure in the dry state, then given a thin coating, by dipping in a rubber latex or in a dispersion of a synthetic elastomer, dried, cured and then again subjected to considerable pressure. The resultant product is highly resilient, has a high elastic recovery upon release of the compressive force and is suitable for replacing, advantageously, rubber, cork, felt and similar materials in cushion pads andsimilar articles.

For the purposes of further describing the invention, reference may be had to the accompanying drawings wherein Fig. 1 shows, in cross section, a pad; and

Fig. 2 is a flow chart indicating a preferred method of making a pad, and to the following examples which are given to illustrate processes and products of the invention but not to limit the invention to the specific embodiments described.

Easample 1 A dilute aqueous dispersion is made from 31 parts (all parts by weight) of finely-pulped newspaper, 65 parts of palmetto pith, 4 parts of paraffin Wax, and 1250 parts of water. The newspaper is the combined filter aid and medium of extension and may be used in an amount from about 10 to 50 parts. The average individual fiber length preferably should be about or less than approximately 0.08 inch; if long fibers are used, the dispersion or slurry has a tendency to settle nonuniformly dlllil'lg filtration and give a nonhomogeneous and stratified product. A perfectly homogeneous product is desired so that there will be no large voids of irregular size or placement in the product and no irregularlyplaced portions where the materials are more firmly bound than at other portions, for instance by long, coarse fibers or pieces of undisintegrated paper. Irregularlyeplaced large voids or irregularly-placed firm portions deteriorate the product to the extent that they prevent the product from giving uniform yield, resilience and recovery. Although newspaper fibers are the preferred filter aid and medium of extension because of low cost and general uniformity, they maybe replaced in whole or in part by wood pulp of similar fiber length and also by the fibrous material disclosed in said patents. The newspaper or substitute should be thoroughly masticated, beaten, ground, or otherwise prepared to give individualized fibers, either prior to or during the formation of the dispersion so that it is free from lumps and so that it mixes with the other materials to give a homogeneous dispersion.

Palmetto pith, preferably prepared so as to be water repellent in accordance with the dis-, closure in said later patent, and regranulated cork arethe preferred powdered materials. One may replace the other in whole or in part or they may be substituted in whole. or in part by 3 the powdered exterior surface of cork bark referred to in said patents, as well as by other light-weight pithy material, for instance ground hibiscus wood, and the like. From 50% to 90% by weight of the powdered material may be used, the preferred range being 55% to 65%, based upon the total weight (dry) of the composition.

The addition of dispersed wax is desired in the composition for making it water repellent. Parafiin wax is the preferred wax because of low cost and it is preferably used as an aqueous dispersion in accordance with the disclosures of said patents. Other water-repellent waxes, resins and binders disclosed in said patents may be used in the composition. The water used in preparing the binder dispersion is considered as a portion of the water used to prepare the final slurry or dispersion. Binder dispersions may be prepared in any suitable manner, for instance by dissolving the binder substance in a solvent and stirring the solution into the large amount of slurry water, whereupon the binder substance, which is preferably insoluble in water, will be thrown out of solution. The methods of forming the binder dispersions which are described in said patents are preferred, however, because of low cost and satisfactory performance.

The slurry should, in general, contain about 96% of water but this may vary between about 92% and 97% by weight. The object is to provide a slurry or dispersion of the type disclosed in said patents. As the water is filtered from the slurry, large amounts of water delay the filtering but there must be sufficient water in the slurry to produce a mixture of uniform structure.

The components of the slurry are thoroughly mixed until a homogeneous dispersion is formed. The slurry is then poured into a mold which is pervious to liquids and allowed to drain to form a matrix as disclosed in said patents. The mold may be in the form of a block from which padcores of the desired shape may be cut or in a form to yield a finished pad-core of the desired size. For continuous operation, a fibrous sheet may be formed on a continuous screen; the sheet may be of the correct thickness to give a final pad of the desired thickness or several sheets may be cemented together. For a pad having a final thickness of about 1% inches, it is preferred that not more than four and preferably not more than two sheets of about equal thickness be united. The best resiliency is obtained when the core is not laminated, and too many laminations kill the final resiliency, for in- 5' stance building up the core from sheets of the usual paper gives a substantially non-resilient product. The process may also be applied to single non-laminated sheets as thin as about /4 inch producing resilient sheets of about A; to inch finished thickness.

If the water is allowed to drain from the slurry in a natural manner, that is without pressure applied to the material in the mold or on the screen, the slurry, in a mold filled with slurry (95% water) to a height of about 6 inches, will settle to give a block of about 1 inches in height. However, I prefer to apply about 3 pounds per square inch pressure to the top of the slurry in the mold and compress the solid components, while wet, to a height of about 1 inch. The block thus formed is removed from the mold and dried either naturally or by heating. This gives a product characterized by unis formity of composition and light weight with a density (dry) of from about 9 to 12 pounds per cubic foot, depending upon whether no compression or the 3 pounds pressure per square inch was used during the filtering or dewatering. For subsequent operations in forming the cushion pads, I prefer to use material which has been compressed under a pressure of at least pound per square inch but not more than 10 pounds per square inch, a pressure of from about 1 to 3 pounds per square inch being preferable.

In the core composition of the pad, the granular material, preferably organic, may comprise from about 50% to of the weight of the composition (on a dry basis) and the medium of extension may comprise from about 10% to 50% of the weight of the composition, these weights being adjusted to allow the composition to contain up to about 6% by weight of parafiin, used in the form of an unstabilized emulsion not requiring a precipitant as is described in said earlier patent. The preferred weight of paraffin is between about /z% and 6% of the weight of the dry composition. The lesser amounts of wax may be used in the case where, for instance, the composition contains the larger amounts of palmetto pith which has been treated so as to be water repellent; and the larger amounts of wax are preferably used when the other components of the composition are not water repellent, or when very high water repellency is desired.

For the production of a circular cushion pad having final dimensions of about 3% inches diameter x 1% inches thickness, two dry rod-like or cylindrical blocks of the material, as described hereinbefore, compressed during settling under a pressure of about 3 pounds per square inch, and having the given diameter and a length or thickness of about 1 inch, are laminated to give a block of about 2 inches total thickness and the composite block is compressed to crush it under a pressure of about 8000 pounds (about 960 pounds per square inch) to a thickness of about inch; then the pressure is immediately released, whereupon the pad returns to a thickness of about 1% inches, that is, about final thickness. The compression appears to disrupt rather uniformly the bonding material within the composition or to cause a slippage and loosening of the interlocking fibers.

The compressed and softened block is then coated with an elastomer, for instance rubber or an elastic synthetic resin. The coating may be accomplished in any suitable manner and with any suitable material; for instance, a latex or dispersion of natural, synthetic or reclaimed rubber or a dispersion of a synthetic resin is used as a bath into which the pad base or core is dipped. Although melted elastomers (in case the elastomer can be melted) or solutions of the elastomers or liquid materials, for instance plasticized vinyl resins, which can later be solidified into elastomers, may be used, dispersions are preferred. Preferably neither the solution nor the dispersion are allowed to'penetrate the base composition very deeply; preferably they are not allowed to enter the base any more than is sufficient to penetrate the first few layers of fibers to unite or integrate these fibers and to unite the coatin firmly with the base. The coating preferably lies substantially entirely on the surface of the core. Melted elastomers in a viscous state and thick solutions and dispersions of the elastomers penetrate the base less than thinly fluid solutions or thinly fluid elastomers due to the larger particle size of the dispersed elastomer games or the viscosity of the thick solutions or the melted elastomers; and water dispersions are preferred as they wet the base material only slightly, particularly in the case where waterrepellent materials, for instance water-repellent palmetto pith and the like, are components of the composition or where the materials are rendered water resistant by the use of dispersed wax as disclosed in said patents. Suitable elastomers for coating materials, in addition to the rubber dispersions or latexes are reclaimed rubber, synthetic rubber, vinyl resins and the like, for instance resins based upon butadiene, vinyl chloride, styrene and the like or copolymers of these materials with other materials, chlorinated or unchlorinated, with or without such plasticizers and amounts thereof as provide the necessary characteristics. Dispersions of these materials may be made in any known manner although it is preferred that the dispersions be free from such wetting agents as cause the base material to be wetted by either the continuous or dispersed phase of the dispersion. Such emulsifying agents as soaps, bentonite, and the like which are predominantly emulsifying agents and have only slight wetting properties may, however, be used in producing the elastomer dispersions. The choice of coating elastomer is somewhat determined by the influences to which the pad is to be subjected, for instance synthetic rubbers are generally more resistant to deterioration by oils and greases than is natural rubber, and synthetic resins of known types are very resistant to water, oils, greases, oxygen in the air, and the like.

The coating may be applied to the base block in any suitable manner, for instance by spraying although dipping the block in the elastomer composition is the preferred method of coating because of the simplicity and general suitability of the coating procedure. A coating of the desired thickness may be obtained by allowing the block to remain in the elastomer composition for the required period or by repeated applications of the coating composition. In general, the dry coating should be, preferably, from about 0.010 to 0.015 inch in thickness, although a coating as thick as about 0.030 inch or more or as thin as about 0.005 inch or less may be applied.

After coating the base it is dried, and when a rubber latex is used the coating is preferably heated sufilciently to vulcanize it in the presence of an accelerator which has been added to the latex. In using rubber latex (or a reclaimed rubber dispersion), the latex is preferably diluted with a a soap solution so that the solids content is preferably about The dipped pad is allowed to drain and is passed through an oven at about 95 C. during a period of about minutes. This dries and vulcanizes the coating. When the pad is treated in this manner, a continuous coating is formed completely enveloping the block, base or core.

But other results are obtained by the heating at this point in the process. As the binder in the core material is preferably plastic or thermoplastic and as the block has been crushed, the heatin releases certain strains or stresses in the core composition and allows the coated core to puff up slightly, the conditions of treatment preferably being such that the core is allowed to puff freely, no pressure or substantially no pressure being applied during the heating. The

puffing is assisted by an expansion. of the air or volatiles in the core where the coating is complete or substantially completeso that the gases do not readily escape; In the case of a covered core prepared as previously described, the 1% inches thick covered core expands to about 1 inches in thickness, or from about 10% to 20% of its crushed thickness which may be more or less: depending upon whether the temperature is higher or lower than the C. temperature stated above and depending upon the time allowed for'softening the binder of the core. This expansion also loosens up the core material quite uniformly;

After the coating has been dried or cured, the coated block is again strongly compressed to crush it, conveniently under a pressure of about 250 pounds per square inch, so that, for example, the 1% inches coated pad is compressed to about 1 inch and then again returns to 1% inches upon release ofpressure. This compression further loosens the fibers within the block quite uniformly and makes the resultant pad highly resilient; In the preferred pad this is ascribed to thevery uniform crushed composition of the block and the elastomeric coating. If the block were not uniform, for instance if the block had large openings in it, portions of the composition could break loose from the walls of the openings and lie therein, in which case there would be Weak places in the surface of the pad after the compressive force is released; also, if the composition contained long fibers, these fibers might cut through the short fiber composition or resist the compressive force, in which case there would be either weak surface areas or areas which would be more highly resistant to compres'si'on, in the finished pad. But where the composition is uniform and the fibers are short and the voids between the fibers are extremely small and uniform and uniformly spaced, the small fibers yield uniformly into the small voids and hence there is uniform yield over the surface of the pad with substantially no areas which are weaker or firmer than others. While the fibers themselves, due to their short length, may not have sufiicient resilience, in themselves, to give substantially complete elastic recovery, they are assisted in the recovery by the elastomeric covering so that the pad has substantially complete elastic recovery.

Pressures between about 250 and 1500 pounds per square inch may be used for the compres sion of the uncoated block. The effect of using pressures that are too low or too high is to reduce the resiliency of the finished pad. About 500 to 1000 pounds give best results. When the basic composition is made under low pressure and is of low density, lower pressures should be used in compression prior to coating than when the basic composition is made with higher pressures and is of high density. High density compositions call for higher pressures to be applied before coating. For maximum resiliency with the palmetto pith product, it is preferred to use a basic composition of about 11 pounds per cubic foot density and pressure of about 950 pounds per square inch. for compression before coating.

Pressures between about 50 and 750 pounds per square inch may be used for the compression of the coated block. The effect of using the lower pressure is to cause the percentage of recovery of the finished pad to be lowered, and the effect of using the higher pressure is to cause the percentage of shrinkage under a given load-to be lowered. in the finished pad. Generally, about 250 to 400 pounds per'square inch is the preferred range of finishing pressureto be applied to the coated pad for maximum resiliency of 11 pounds density material. It is possible'to effect the crushing by pressing the material under rolls instead of a platen press, for example by hy,- draulic press, which is preferred, and if rolls are used the amount of squeeze should be adjusted to produce the same finished thickness as if the material were pressed in a hydraulic press.

It is desirable for the two compressions to be effected because the first compression causes relatively great slippage of the fibers and-softening of the composition, as well as a reduction in thickness, and if the first compression is omitted and the only compression is the compression, of the coated block, the resiliency of the finished pad will be reduced and the coating on the: finished pad will become wrinkled around the edges of the pad, especially if the pad is of considerable thickness. This is due to the decrease in thickness after the initial pressing. The first compression preferably reduces the thickness of the core tothe final size or about the final size and the elastomeric coating is preferably applied to the core in the reduced condition. Then when the coated core swells under heat and is again compressed and returns to final size, the elastomeric coating is relatively tight and unwrinkled. If there is no compression of the coated block or further loosening of the fibers after coating, the percentage of recovery of the coated pad under its initial load will be low. The result of pressing the coated pad is to remove the shrinkage in thickness that takes place with the first compression or loading to which the pad is subi jected. Thereafter the percentage of recovery will be very high. The preferred finished pad thus comprises a block of crushed, soft, resilient light-weight material having a fine uniform structure free from large, visible, irregularlythe core made as and of the materials disclosed 8 the volume of voids in the core is between 50% and 85% of the total volume of the core, good results being obtained where the core material has a minimum of about 40% by weight of short length fibers averaging not over 0.12 inch in length in a total of 100% by weight of fibrous material or a minimum of about 15% by weight of the short length fibers on the total weight of the core, although best results are obtained where all of the fibrous material has an average length of about or less than approximately 0.08 inch. It is to be understood that the compressions are to crush the core material and render the core resilient; and the core material is not firmly or rigidly bound in its compressed condition as is usual, for instance, in the production of molded or laminated board where the board is held under pressure until a binder hardens and retains a fibrous or other filler in a compressed condition, in fact the pressure should preferably be released quickly under this treatment.

The production of a preferred pad has been described. It is, of course, possible to obtain some of the benefits of the invention by varying the materials and process. For instance, the core of the pad may be made entirely of palmetto the pith of the palmetto serving as the granular material and the fibers of the palmetto serving as the fibrous material; and the fibers may be longer than the lengths given, but at the expense of desirable characteristics as previously explained. The granular material is preferably a non-hardening material, that is, it preferably remains in about the condition first used and does not harden as does inorganic plaster or cement, it preferably remains as individual granules of the size first used which do not agglomerate as do cement or plaster and no hardened mass is formed within the core to prevent a component of resilient movement perpendicular to the fiat faces of the pad described. In case the core is made of laminated material, the cement between the layers of core material is preferably yieldable and non-rigid, as is an elastomer, although in this case a layer of somewhat rigid material may be used as the layer is thin, preferably being no thicker than necessary to hold together the layers of core material, for instance no thicker than the thin coatings, and it lies across the direction of resilient movement. One of the compressions may be omitted as may the heating but at the expense of desirable characteristics as previously explained. Also denser core material may be used; core material having a density of 22 pounds per cubic foot has been processed with beneficial results but the amount thickness while the pressure is applied is within the range of about 35% to 80%, with a preferred range of about to In the second pressing, that is the pressing after coating, the pressure used should be such that the reduction in thickness of the pad, after the pressure is released, is within the range of about'6% to 24% of the thickness of the coated pad, with a preferred range of about 15% to 21%. The reduction in thickness while the pressure is applied is within the range of about 25% to with a preferred range of about 40% to 75%. These compressions are an important feature of the invention irrespective of the composition of the core, so long as it is porous and fibrous, Where of resiliency or more particularly the percentage of compression under a given load is very much less, for example 20% as compared to 50% for the 11 pounds density material.

The preferred pad thus finished is resistant todeteriorating influences, is of light weight and is highly resilient. The weight of the inner crushed material of the pad is from about 14 to 30 pounds per cubic foot. The total weight of a finished pad will depend somewhat upon the weight of coating material. Under a total load of about 1000 pounds, a circular pad such as described above of about 3% inches in diameter and 1% inches in thickness showed a reduction in thickness of about 50% and a recovery to about of its original thickness upon release of the load. A pad of the given dimensions with a coating of reclaimed rubber about 0.015 inch thick weighed about (slightly less than) 2 ounces.

Example 2.

As a further example of the use or other granular materials, a cushion: pad was made i a manner similar to that described above in which fine regranulated cork was substituted for the palmetto pith in the same formula producing cylinders of dried material 3 /4 inches in diameter and 1 inch thickand' about ll pounds per cubic foot density. The particles of cork or other similar granular material should be of an average size within the range of about 100 mesh to 4 mesh, preferably Within the range of about 50 mesh to lZmesh. Two: of-these cylinders were laminated as before, producing a cylinder 2 inches thick by 3% inches in diameter. This core was then subjected to a pressure of 600 pounds per square inch; reducing its thickness to 1-1, inch and upon release of 'pressure the thickness returned to 1 inches.

The core Was then element comprising an elastomer integrated with the outside of the core element.

5. A resilient pad comprising a core element and a covering element; the core element having a water-resistant, uniform, partially crushed bonded composition having the bonds loosened and comprising a finely-divided granular material, a fibrous materialand a binder, the fibers of the fibrous material being short and, individualized; the covering, element comprising an elastomer integrated with-the outside of the core element.

6. A resilient pad comprising a core element and a covering element; the. core element havdipped and vulcanized as before and the-thickand'a recovery to about 97 of its originalthicknessafter release ofthe load;

The pads described herein are made with a maximum amount of low cost materials and a minimum amount of more costly materials and, although very resilient, have the advantages,

ing a. uniform, partially crushed bonded composition having the bonds loosened and comprising palmetto pith, afibrous material and a binder, the fibers of the fibrous material being. short and individualized; the covering. element comprising an elastomer integrated, with the outside of the core element.

'7. A resilient pad comprising a core element and a covering element; the core element having a uniform, partially crushed bonded compo.- sition having the bonds loosened and comprising finely-divided cork, a fibrous material and. a binder, the fibers of the fibrous material being short and individualized; the covering element comprising anelastomer integrated with the outside of the core element.

8. A resilient pad comprising a core element and a covering element; the core. element being substantially free from. large voidsand having a uniform, partially crushed bonded composition among others, of being much less costly and much lighter in weight than solid rubber, much more; resilient than cork or felt, much less absorptive of liquids than either baker cork-board,

tomer integrated with the outside of the core element. l

2. A resilient pad comprising a core element and a covering element; the core element comprising a resilient, partially crushed, fibrous, po-

rous bonded material of substantially uniform composition having the bonds loosened; the covering element comprising an elastomer integrated with the outside of the core element.

3. A resilient pad comprising a core element and a covering element; the core element having a uniform, partially crushed bonded composition having the bonds loosened and comprising a finely-divided granular material, a fibrous material and a binder, the fibers of the fibrous material being short and individualized; the cove5 ering element comprising an elastomer integrated with the outside of the core element.

4, A resilient pad comprising a core element and a covering element; the core element having a uniform, partially crushed bonded composition having the bonds loosened and comprising a finely-divided granular material, a fibrous material and a binder, the fibers of the fibrous material being individualized and having an average length of not over about 0.08 inch; the covering having the bonds loosened and comprising a finely-divided granular? material; a, fibrous material, and; abinder, the fibers of, the fibrous material being, short and-individualizedythe covering element comprising an elastomer integrated with the outside of thecore element.

9. A resilient pad comprising a core element and a covering, element; thecore element being substantially free, from large irregularly-placed voids and having, a uniform, partially crushed bonded. composition having the bonds loosened and comprising a finely-divided: granular material, a fibrous material and a' binder, the fibers of'the fibrous materialbeing short and individualized; the covering element comprising an elastomer integratedwith the outside of the core element,

10. A resilient pad comprising'ai core element and a covering element; the core element having a uniform, partially crushed bonded composition having the bonds loosened and comprising a finely-divided granular material, a fibrous material and a water-insoluble binder, the fibers of the fibrous material being short and individualized; the covering element comprising an elas tomer integrated with the outside oi the core element.

11. A resilient pad comprising a core element and a covering element; the core element having a uniform, partially crushed bonded composition having the bonds loosened and comprising a finely-divided granular material, a fibrous material and a binder comprising a Wax, the fibers of the fibrous material being short and individualized; the covering element comprising an elastomer integrated with the outside of the core element.

12. A resilient pad comprising a core element and a covering element; the core element having a uniform, partially crushed bonded composition having the bonds loosened and comprising a finely-divided granular material, a fibrous material and a binder comprising paraffin wax, the fibers of the fibrous material being short and individualized; the covering element comprising an elastomer integrated with the outside of the core element.

13. A resilient pad comprising a core element and a covering element; the core element having a uniform, partially crushed bonded composition having the bonds loosened and comprising about 65% by weight of water-resistant palmetto pith, about 31% of newspaper pulp in which the fibers are individualized and have an average length of not over about 0.08 inch, and

about 4% of paraffin wax; the covering element being elastic reclaimed rubber integrated with the outside of the core element and being about 0.015 inch thick, said pad having a compression value of about 50% under a load of 125 pounds per square inch and a recovery of about 95%.

14. Method of forming a resilient pad which comprises: forming a slurry having a dispersed phase comprising finely-divided pithy granular material, a fibrous material and a binder material, and a continuous phase comprising water; draining the water from the slurry to form a porous matrix; drying the matrix; crushing the dried matrix thereby loosening the bonds between said materials; and covering the crushed matrix with an elastomeric material.

15. Method of forming a, resilient pad which comprises: forming-a slurry having a dispersed phase comprising finely-divided pithy granular material, a fibrous material and a binder material, and a continuous phase comprising water; draining the water from the slurry to form a porous matrix; drying the matrix; covering the dried matrix with an elastomeric material; and partially crushing the assembly thus produced thereby loosening the bonds.

16. Method of forming a resilient pad which comprises: forming a slurry having a dispersed phase comprising finely-divided pithy granular material, a fibrous material and a binder material, and a continuous phase comprising water; draining the water from the slurry to form a porous matrix; drying the matrix; crushing the dried matrix thereby loosening the bonds between said materials; covering the crushed matrix with an elastomeric material; and heating the covered matrix.

1'7. Method of forming a resilient pad which comprises: forming a slurry having a dispersed phase comprising finely-divided pithy granular material, a fibrous material and a binder material, and a continuous phase comprising water; draining the water from the slurry to form a porous matrix; drying the matrix; crushing the dried matrix thereby loosening the bonds between said materials; covering the crushed matrix with an elastomeric material; heating the covered matrix; and partially crushing the assembly thus produced.

18. Method of forming a resilient pad which comprises: forming a slurry having a dispersed phase comprising about parts of water-resistant palmetto pith, about 31 parts of newspaper pulp in which the fibers are individualized and have an average length of not over about 0.08 inch and about 4 parts of parafiin wax and a continuous phase of about 1200 parts of water, all parts by weight; running the slurry into a mold; draining the water from the slurry to form a matrix; drying the matrix; crushing the dried matrix to substantially the size of the core of the finished pad thereby loosening the bonds between said materials; applying to the surface of the crushed matrix a water dispersion of reclaimed rubber and integrating the rubber with the matrix material at their adjacent surfaces to cover the matrix material; heating the covered matrix thereby causing it to puff; and partially crushing the covered matrix to the size of the finished pad.

CHARLES H. SCI-IUI-I.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 38,813 Davis June 9, 1863 1,543,394 Parsons June 23, 1925 1,904,026 Field et al Apr. 18, 1933 1,906,028 Weber et al Apr. 25, 1933 1,909,521 Bryant 1. May 16, 1933 2,021,370 Mallay Nov. 19, 1935 2,155,020 Nanfeldt Apr. 18, 1939 2,382,448 Schuh Aug. 14, 1945 2,395,218 Gauthier Feb. 16, 1946 2,401,936 Jenkins June 11, 1946

Claims (2)

1. A RESILIENT PAD COMPRISING A CORE ELEMENT AND A COVERING ELEMENT; THE CORE ELEMENT COMPRISING A RESILIENT, PARTIALLY CRUSHED, FIBROUS, POROUS BONDED MATERIAL HAVING THE BONDS LOOSENED; THE COVERING ELEMENT COMPRISING AN ELASTOMER INTEGRATED WITH THE OUTSIDE OF THE CORE ELEMENT.

14. METHOD OF FORMING A RESILIENT PAD WHICH COMPRISES: FORMING A SLURRY HAVING A DISPERSED PHASE COMPRISING FINELY-DIVIDED PITHY GRANULAR MATERIAL, A FIBROUS MATERIAL AND A BINDER MATERIAL, AND A CONTINUOUS PHASE COMPRISING WATER; DRAINING THE WATER FROM THE SLURRY TO FORM A POROUS MATRIX; DRYING THE MATRIX; CRUSHING THE DRIED MATRIX THEREBY LOOSENING THE BONDS BETWEEN SAID MATERIALS; AND COVERING THE CRUSHED MATRIX WITH AN ELASTOMERIC MATERIAL.

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