US2077720A - Felted product and method of making the same - Google Patents

Description

April 1937- w. R. SEIGLE ET Al. 2,077,720

FELTED PRODUCT AND METHOD OF' MAKING THE SAME Filed May 28, 1935.

INVENTORS. WILLIAM R. SEIGLE. GEORGE 8. BROWN.

ATTORNEY:

Patented Apr. 20, 1937 UNWE FELTED PRODUCT AND METHOD OF MAK- G THE SAME William R. Seigle, Orienta Point, Mamaroneck, N. Y., and George Basil Brown, Somerville, N. .l., assignors to Johns-Manville Corporation, New York, N. Y., a corporation of New York Application May 28, 1935, Serial No. 23,802

13 Claims.

This invention relates to a felted fibrous prodnot and the method of making the same.

An object of the present invention is the production of thermal insulation of felted, fibrous, nonv combustible material, which insulation is high in efficiency, light in weight, easy to manufacture, low in cost and easily and quickly applied where desired.

As an important feature of the invention we employ mineral wool fibres and form a sheet from an aqueous suspension including said fibres, the mixing of the fibres with the water being incompiete, so that a portion of said fibres is well dispersed in the liquid and other portions are less effectively dispersed and occur or remain in clusters or loose nodules. As a result, when the fibers are collected as a thin wet felt or sheet on a permeable conveyer or traveling wire screen and the major portion of the water is sucked out into a vacuum chamber as said screen passes thereover, the fibres are matted and. interlocked together in a sheet of widely varying thickness. As the water is sucked out through the c'onveyer, the fibres of the clusters or nodules become arched,

bent or inclined in all directions, forming highly porous projections of loosely matted fibres, while the more effectively dispersed fibres in the intermediate areas form thinnerportions, withthe fibres lying more nearly in parallel planes.

As a further important feature the sheet, which is thus relatively smooth on the under side and irregular on the upper side, is dried to remove the remaining water, but without calendering or otherwise completely crushing down the very highly porous lumps or projections. A plurality of the layers or sheets are superposed to form a built up structure of the desired thickness, preferably but not necessarily, before drying to remove such water as is not removed by the suction. As

the sheets or layers are brought together the pro- J'ections which have been automatically formed without any embossing or other mechanical action and which are themselves highly porous and are integral with the thinner portions, serve to slightly space the thinner portions to varying degrees. Due to the spacing action and the porosity of the nodules or clusters, an extremely light product is formed, which structure is highly efiicient as a thermal insulator. I

As no mechanical action is required other than an incomplete or ineffective dispersion, a floating of the fibres over the conveyer, a sucking out of a portion of the water and an assembling and drying, the product may be made at very low cost.

To more effectively hold the fibres together in felt form during remoqval from the traveling screen, and the assembling of a plurality of layers of a sheet, and to give greater structural strength to the final product, there may be and preferably is employed a relatively small amount of fibres stronger than the mineral wool fibres, such for in-- stance as asbestos fibres, and there is preferably employed a small amount of some adhesive or binder which may be intermixed with the fibres in the aqueous suspension.

, An embodiment of the invention that is preferred at this time will be described in cormection with the drawing, in which Fig. 1 shows a diagrammatic sectional side view of equipment suitable for use in making the improved product;

Fig. 2 shows a sectional view on line 2-2 of Fig. 1, with the felt somewhat exaggerated in thickness, as compared to its outer dimensions, for clearness of illustration;

Fig. 3 shows a sectional view on line 3-3 of Fig. 1, withthe felt again exaggerated in thickness;

Fig. 4 shows an end view of a. section of tubular pipe covering constructed in accordance with the invention;

Fig. 5 shows a side view of a bat or pad also constructed in accordance with the-invention;

Fig. 6 shows a modified form of bat in the process of formation; and

Fig. 7 shows a side view of another modification of the invention.

In the various figures, like reference characters denote like parts.

In Fig. 1 there is shown a water-permeable conveyer' 9 such as a continuous retiform belt of coarse wire gauze, passing over the guide rollers Ill, II and H of which one, suitably, roller I2 is motor-driven. Placed above the upper reach of the conveyer belt and, suitably, near the roller l I is a feed hopper l3, of width slightly less than the width of the belt. This hopper may be provided with a retaining strip M of rubber composition or other satisfactory sheet material, contacting with the upper surface of the belt 9 andretarding or preventing the flow oi? the mixture from the hopper counter to the direction of movement of the conveyer.

This mixture consists of an aqueous suspension of incompletely intermingled fibres of a relatively collapsible nature and fibres or fibrous structure of a less collapsible nature. Thus, the suspension may contain well dispersed fibres of mineral wool II and void-containing clusters Ill of mineral wool fibres unevenly distributed throughout the suction will support.

suspension, Such clusters are commonly called nodules and are resiliently compressible when.

subjected to a, low pressure. The suspension may be formed in a separate tank (not shown) provided with gentle agitation and transferred to the feed hopper I3 by any suitable means.

It will be noted that the conveyer belt, in its upper reach, may travel upwardly in inclined manner, to minimize excessive flowing of the said suspension forwardly along the conveyer, while making possible a substantial hydrostatic head at the deepest portion of the suspension. This head causes filtration through the belt 9 and the collection thereon of a thick felt.

Because the fibrous suspension is not uniform, the felt produced is also of varying nature. Thus, the felt will include portions containing a large proportion of clusters 18 of mineral wool, enclosed by and interfelted with dispersed fibres, and intervening portions 20 in which there are either no clusters of mineral wool or smaller or fewer clusters than in the first-mentioned portions.

Water passing by filtration through the belt may be collected and allowed to flow away through the receiver it that is placed under the said member at a position beneath the hopper l3.

conveyer and contacting closely with the underside thereof. The said member I! is connected to a vacuum line; so that there is applied to the felt, quickly, a suction corresponding,'for ex ample, to 6 inches of mercury or more. This suction causes penetration of the clusters by adjacent fibres, to give integral binding. It also causes collapse of the felt, to an extent varying with the nature of the fibres predominating in different portions of the felt. Thus, in portions in which thickness-establishing clusters of mineral wool predominate, there is less collapse than in intervening portions in which the collapsible dispersed fibres predominate. In a typical operation, a felt one-half inch thick was found to collapse, under the influence of the suction, to a maximum thickness of one-tenth inch. In such a sheet, in which one-tenth inch maximum thickness corresponds to the distance between the tops of the elevated portions and the opposite surface or base of the sheet, the thickness may be only one-twentieth of an inch in the depressed portions, between the said elevated portions.

The result is a product of highly irregular upper surface having elevations at positions corresponding to the location of clusters of mineral wool.

It will be understood that the suction above referred to may be substituted by other equivalent means, such as air under moderate pressure applied to the upper surface of the felt, for subjecting the felt to different pressures on its two faces. Such means are included in the term ,suction.

In the filtration step, the presence of the dispersed-fibres of mineral wool increases the resistance to the passage of fluid through the felt and, thereby, increases the vacuum, expressed in pounds to the square inch, that the felt under This increased suction and the intermingling of the fibres and clusters of rock wool in non-uniform manner causes the uneven and extensive collapse of the felt.

If the felt product is to be used in pipe covering, the felt may be wrapped, in wet form, around the mandrel l8. As illustrated, the felt is not calendered or smoothed but is wrapped upon itself with the projections left upstanding. When the felt has been wound upon itself to the thickness desired, the wound material'is severed from the oncoming sheet, the mandrel and material .wound therearound is removed, and a new mandrel inserted. The winding operation is then resumed. The wound material is subjected to drying, to remove water and cause stiffening or hardening of the binder and setting of the material in the previously established form. In such a composite, the smooth base portion of one ply of the sheet material contacts with the elevated sequent minimizing of circulation of air therebetween, when the finished article is used as thermal insulation.

Before being assembled, the several plies of the felt may be coated discontinuously or lightly with a thin layer of adhesive, so that the several plies are adhesively secured in the final assembly.

In such a laminatedproduct, there is breaking or discontinuity of major voids in the direction of the shortest dimension of theproduct. Being shaped wet and then dried, the final shape desired is thus established and the several layers thoroughly united and fixed in relative positions, particularly because the binder, during drying, may migrate in part to the surfaces of the several laminae, where it is most needed.

A finished section of tubular pipe covering is illustrated in Fig. -i. The tubular insulation may be provided with an inner lining and reenforcing material 2 i, such as a sheet of asbestos paper, and an outer wrapper 22 of suitable reenforcing sheet material, such as cloth or paper. If the inner liner is to be used, it is suitably placed around be made a bat or pad, such as illustrated in Fig. 5, including composited plies of the sheet material of substantially regular lower surface and uneven upper surface. If no binder has been used in the original felted sheet material or if the several sheets have been dried before being composited, then the several plies may be adhered together by means of a small proportion of binder material applied to the surfaces of the sheets before being composited.

In making a bat, the felt from position 23, Fig. 1, may be lapped on itself by a reciprocating lapping mechanism, illustrated generally at 24, Fig. 6, this mechanism replacing, for the purpose, the mandrel l8.

In another modification, such as illustrated in Fig. 7, clusters 25 of rock wool may be dropped upon the surface of the wet felt as at approximately the position of section line 2-2, Fig. 1. These clusters become entangled (interlocked) with the fibres of the surface portion of the felt j may admix starch or a casein adhesive.

aoravao asbestos fibres to which there has been applied and remain secured thereto as the felt is subsequently collapsed by passage over the suction member i I. A number of plies of felt so made may be composited, as illustrated, the clusters 25 serving as very effective spacing means between the several plies.

In making the fibrous suspension to be charged to thehopper i3, we have used to advantage a mineral wool of silica content above the usual normalfor such wool, as, for example, a rock wool containing approximately 52 to 62 per cent by weight, of silica, this type of wool having been found to be resistant to disintegration or solution in the water in the hopper l3 or in the preceding mixing step. Other wool compositions are, of course, capable of use, and the high silica content wool is mentioned merely as an example.

The mineral wool fibres may be of length that is medium for common mineral wool products. Fibres that are too short give a felt that is not sufiiciently strong, whereas fibres that are too long do not mat down well in the finished felt. A fibre that has been used satisfactorily contains a predominating proportion of fibres of the average length of about one-half centimeter.

Into the selected mineral wool in the form of nodules, there are blended and dispersed, nonuniformly, fibres of collapsible material of the type of mineral wool in not nodulated condition. say, in the proportion of 5 to parts by weight of the latter for 100 parts by weight of the nodules. There is suitably incorporated, in the aqueous suspension from which the felt is formed, a binder that is weak when wet or in solution and stifi or semirigid when dry or in solid form. Thus, we One per cent of the binder on the dry weight of the mixed fibres is a satisfactory proportion.

Reenforcement and bonding of the fibrous clusters by asbestos, substituted for the dispersed fibres of mineral wool in the process described,

is particularly satisfactory. For this purpose, we have used to advantage fibres of amosite asbestos. We may use also chrysotile asbestos fibres of medium length or longer, preferably in a mixture with amosite fibres. The asbestos fibres, being of relatively fine texture, decrease the openness of structure during the filtration step and give greater strength to the finished product than.-

when all mineral wool is used. Also, the asbestos fibres may substantially enclose the fibrous clusters, and minimize air circulation therethrough, whereby the effectiveness as thermal insulation is increased.

The nodules of mineral wool used may be those made conventionally by suitable tumbling of mineral wool in dry form. For best results, how

ever, large nodules or clusters formed by a wet mixing process are used.

In-this wet mixing process for forming nodules, mineral wool in felted but not nodulated form is charged into a large volume of waterin a mixing tank with a slow speed rotary agitator. The large volume of water serves to give a fiuent uneven suspension. Thus, thirty pounds of rock wool may be stirred into one thousand gallons of water, the agitator revolving at a rate of about revolutions per minute. This wet process gives very large nodules. g

The resulting uneven mixture is then charged into the hopper l3 and fabricated as described.

For the nodules of mineral wool, there may be substituted other void-containing fibrous clusters,

75 as, for example, aggregations made by tumbling a small proportion of a suitable adhesive.

The product made as described has interesting properties. effective in thermal insulation; it has a low coefiicient of heat transfer and all parts thereof are semirefractory. Because of the interlocking of the intermingled fibres of which the material is composed, the product is coherent. The dispersed fibres engage the exterior surfaces of the clusters of mineral wool and extend as felted or matted material between the individual, adjacent clusters or nodules. The fibres serve to reenforce and skeletonize the whole, with preservation of voids within the clusters. The matted fibres in. the composited articles shown in Figs. 4-7 extend predominantly generally transversely with respect to the shortest dimension of the articles.

There appear to be larger pores or less close knitting of the fibres in the base than in the opposite portion or upper surface of the felt, as made, this upper surface having the upstanding projections therein. The close knitting of the upper surface seals the voids in the clusters, that is, minimizes circulation of air therethrough or through a composite of a plurality of felts of the kind described.

This result is evidently due to partial segregation of fibresand clusters according to rate of settling in hopper it and/or to the washing away of fine fibres initially lodged in the base portion, due to water rushing therethrough during felting or under suction. To facilitate filtration and washing out of fines, the wire gauze constituting the belt 9 may be about 20-mesh or coarser.

In general. the details that have been given are for the purpose of illustration, not restriction. Variations within the spirit of the invention are intended to be included within the scope of the appended claims.

What we claim is:

1. In making a lightweight fibrous product, the method which comprises forming 'an aqueous sus pension of the selected fibrous material, forming a wet felt from the said suspension, applying to a surface of the wet felt clusters of fibrous material adapted to be interlocked in the said felt, to give a sheet of irregular surface and thickness, and then drying the said sheet, to set the shape thereof. 2. A sheet comprising resiliently compressible nodules of mineral wool constituting thick portions of the sheet and a thin web of matted fibres extending between the said nodules, therearound, and thereinto, the web being interlocked with the nodules and forming therewith a coherent sheet provided with irregularities of surface and the sheet being in unsmoothed condition.

- 3. An insulating covering comprising superimposed sheets including spaced, void containing, loosely felted clusters of mineral wool fibres, and a web of less thickness than the clusters and comprising more closely felted mineral wool fibres extending between and interlocked with the fibres of the clusters, the clusters spacing the adjacent sheets apart and coacting with. the sheet faces to form pockets containing air.

4. An article of manufacture comprising a flexible insulating sheet comprising void containing It is light in weight. It is very clusters, whereby circulation of air through the clusters is minimized.

5. In making a lightweight, felted sheet product, the method which includes the steps of forming an aqueous suspension comprising mineral fibres, a portion of the fibres being in separate dispersed condition and other portions of the fibres being in definite clusters, depositing the fibres on a permeable, travelling supporting surface to form a wet mass of interengaged fibres, applying sufficient suction to remove the major portion of the water from the wet felt through said supporting surface and to mat the dispersed fibres and collapse the clusters only partially, so as to form projections on the face of the sheet, and assembling a plurality of layers of said sheets in superimposed relationship, the said projections serving to space the layers.

6. An article of manufacture comprising superimposed flexible insulating sheets including void containing, loosely felted clusters of mineral wool fibres disposed in a substantially common plane, and a web of less thickness than the clusters and comprising more closely felted fibres of mineral wool and asbestos interconnecting the clusters and interlocked with the cluster fibres and extending predominantly in a direction generally transverse to the direction of the shortest dimension of the sheet.

' 7. An article of manufacture comprising a flexible insulating sheet comprising void containing,

loosely felted clusters of mineral wool fibres disposed in a substantially common plane, and a web of more closely felted fibres of mineral wool and amosite extending between and interlocked with the cluster fibres and thinly coating the clusters,

whereby circulation of air through the clusters is minimized.

8. An article of manufacture comprising superimposed flexible insulating sheets including void containing, loosely felted clusters of mineral wool fibres disposed in a substantially common plane and a web of less thickness than the clusters and comprising more closely felted fibres of min eral wool and asbestos interconnecting the clusters and interlocked therewith, a coating of the circulation of air through the web material extending entirely over the clusters, whereby circulation of air through the clusters is minimized, the clusters spacing adjacent sheets apart and cooperating with the web to form pockets containing air.

9. A flexible insulating sheet comprising void containing, loosely felted, fibrous clusters, and a web of less thickness than the clusters and ineluding more closely felted fibres which interlock with the cluster fibres and interconnect the clusters.

10. An insulating covering comprising 5111M rimposed sheets including void containing, ioosgly felted, fibrous clusters, a web of less thickv ness than the clusters and comprising more closely felted fibres interlocked with the cluster fibres; and interconnecting the said clusters, and a binder material which is semi-rigid when dry and which produces adherence between the various fibres as well as between the sheets.

11. An insulating covering comprising a strong flexible sheet including void containing, loosely felted, fibrous clusters, and a web generally of less thickness than the clusters and comprising the same but more closely felted fibres extending between and interlocked with the fibres of the clusters.

12. A flexible insulating sheet comprising void containing, loosely felted clusters of mineral wool fibres disposed in a substantially common plane, and a web of more closely felted fibres of mineral wool and asbestos interlocked with the fibres of the clusters and coating the clusters, whereby clusters is minimized.

' 13. A flexible insulating sheet comprising void containing, loosely felted clusters of mineral wool fibres disposed in a substantially common plane, and a web of more closely felted fibres of mineral wool and amosite interlocked with the fibres of the clusters and coating the clusters, whereby circulation of 'air through the clusters is minimized.

WILLIAM R. SEIGLE. GEORGE BASIL BROWN.

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