US2126411A - Method for making mineral wool - Google Patents

Description

Aug. 9, 1938. E. R. POWELL METHOD FOR MAKING MINERAL ,WOOL

Filed April 17. 1934 [NI/TOR. Edward R Powell ATTORNEY Patented Aug. 9, 1938 UNITED STATES PATENT OFFICE IHETHOD FUR ING MNERAL WOOL Edward R. Powell, Alexandria, ind, aesignor to Johns-Manville Corporation, New York, N. Y.,

a corporation of New York Application April it, 193d, Serial No. 720,980

12 Claims.

of high velocity.

A typical composition oi a commercial mineral wool of usual type is as follows:

Component Parts by weight Silica 39. 5 to 41. 0 Aluminum 0Kld8 8. 0 to 12.0 Iron oxide... 1. 5 to 2. 5 Calcium oxide 27. 0 to 32. 0 Magnesium oxide 8.0 to 12.0 Miscellaneous ingredients... Less than 6.0

In the composition given the proportion of silica (acid ingredient) to the sum of the iron,

calcium and magnesium oxides (basic ingredients) is frequently about 1.0 to 1.0, but may be as low as 1.0 to 1.3 vfor the general type of mineral wool represented by the above analysis.

Suitable raw material for this wool, such as an arglllaceous limestone, is charged, usually in lump form, into a cupola type of furnace, melted, and

discharged continuously in a stream at the rate of about 600 to 1,000 pounds an hour, at a temperature of approximately 2500 to 2600 degrees F. The material in the stream is fiberized by means of a very strong, rapidly moving jet of steam issuing from two slots meeting, for example, at a point to form a v-shape. Each slot of the V may be about two inches long and 0.05 to 0.07 inch wide. The steam jets may issue at the velocity produced by gauge pressure of to pounds per square inch oi steam pressure and may be superheated, say, to the extent of one hundred degrees or less.

A mineral wool so made contains a very large proportion of material in undesirable form, especially in the form of very short fibres or of bead-like aggregates known commercially as shot. Since most of the short fibres are probably not over one-sixteenth inch in length, it is customary to add a spray of oil or other binder in the blowing operation to adhere much of the fine material together and avoid its being lost from the chamber as dust. As to the proportion of "shot, it is possible to separate as much as 25% of this material from commercial mineral wools, as by settling in water.

01 fibres which have a desirable length, as, for example, a length of several inches, there is a very small proportion. Further, what long fibres are presl5 ent are substantially straight.

An object of the invention is to produce a matted mineral wool product of greater resiliency and lower density than previously obtained from raw material of a given composition, to provide in a viscous melt-from which fibres of the desirable type may be stretched or blown, to-produce mineral-wool of minimized proportion of short fibres and. shot", and/or to produce a mineral wool comprising a relatively high proportion of fibres it of desirable length and shape, suitably slightly curled in such manner as to decrease appreciably the compactness of a i'elt into which the fibres settle from an aerilorm suspension. i

In one embodiment, the invention includes the 20 steps of forming a melt of suitable raw material that is viscous, that is of molasses-like consistency, and the stretching or drawing out of material in this melt to form fibres of maximum length as will be described.

Another embodiment of the invention comprises the successive reduction of a stream oi molten material first into smaller streams and eventually into fibres, preferably by a method including contacting a plurality of steam jets one 30 after another, at closely spaced intervals, the steam in a given jet being at a higher pressure than the steam previously contacted with the molten material.

The pressure referred to in connection with w the steam jets is obviously the pressure in the lines supplying the steam before the steam escapes therefrom. Thus, high pressure steam would produce a steam jet of high velocity, after the steam escapes from the pipe or nozzle, and m low pressure steam would, likewise, give a steam jet of low velocity.

The invention is as illustrated in the accompanying drawing forming a. part of this specification in which Fig. 1 is a diagrammatic side view of an apparatus constructed in accordance with the present invention;

Fig. 2 is a diagrammatic side view of a modified form of the invention which includes means 50 for heating the steam;

Fig. 3 is a diagrammatic side view of a suitable apparatus for contacting a plurality of steam jets with a stream of molten material and also the approximate course which the molten ma- 55 terial assumes on being passed through the apparatus;

Fig. 4 is a front view of the apparatus illustrated in Fig. 3 and. includes a diagrammatic representation of the course of the stream of molten material up to and including the stage at which the molten material is contacted with the first steam jet;

Fig. 5 is a front view of an element suitable for use in contacting steam with the stream of molten material;

Fig. 6 is a view partly in vertical section and partly diagrammatic, of a chamber for adjusting the temperature of suitable molten material to that desired, and of accessories and steam jets for shredding the molten material issuing from the chamber into fibres of the desired properties, and

Fig. '7 is a front view, partly diagrammatic, of the end of the apparatus illustrated at the right of Fig. 6.

The invention will be described in connection with the figures in all of which like reference characters denote like parts.

There is shown a stream of suitable molten material II being passed near one or more steam outlets l2 which provide a jet or jets of steam 13 that strike the stream of molten material and tend to divide it into a plurality of elongated masses or smaller streams. The portions of the thus divided or treated stream contact with another jet ll of steam, issuing from the nozzle l5 which shreds the molten material into the fibrous composition Hi,

The pressure in the steam jets l3 and H may be adjusted by any suitable means, as, for example, by the valves l1 and I8.

In the embodiment shown in Fig. 2, the apparatus and method of Fig. 1 is modified to the extent that one or more gas flames I! are caused to impinge upon steam jet [3 and strongly superheat the steam therein before the jet strikes the stream of molten material. This superheating of the steam, say, to a temperature that may be approximately as high as the temperature of the molten material in the stream, minimizes the cooling produced by the steam upon the molten material and prevents any sudden or explosive expansion ot the steam in contacting the melted rock.

In the apparatus illustrated in side view in Fig. 3, and in front view in Fig. 4, the molten material ll passes in front of a bank of very small and relatively low speed steam .jets issuing from the apertu-red member 20. In this member the proportion of the face area that is perforated may increase toward the outer edge, the inner portion being, for example, either imperforate or provided with smaller or less closely spaced apertures than the said outer portion. With such a member, jets are caused to issue which, while spreading the stream of molten material and tending to break it into smaller streams, tend also to confine the final width of the mingled smaller streams to something less than the width of 'the member 20, as illustrated disgrammatically in Fig. 4.

On passing in front of the member 20, the molten material is not only partially divided into smaller streams but also. is deflected in direction away from the said member and into contact with a second jet of steam of higher pressure than the first jet. This second jet of steam 2| issues from the slot 22 as shown. The jet 2| causes further subdivision and stretching of the stream of molten material and deflects it, as illustrated, in the direction of the third steam jet 23 issuing, for example, from the V-shaped slot of the member 24.

The distance between the positions of first contact of adjacent jets with the molten material is advantageously of the order of 1.5. to 4 inches.

Each of these members for providing the three steam jets contain separate pressure control elements, such as a valve 25 and a restriction in the form of a small orifice 26 in the line admitting steam to the low pressure steam member 20. As a substitute for the member 20, there may be used a corresponding member 21, apertured as illustrated in Fig. 5, with the apertures spaced far apart or omitted from the central portion, and with orifice 26.

It will be understood that steam enters at the bottom of the assemblies shown in Figs. 1-4.

To properly condition the molten material before it is subjected to the flberizing operation, described above, the material is adjusted in consistency to promote ductility, by which term is meant the property of being adapted to be drawn out into filaments of satisfactory average length before being severed or broken. The material of preferred viscosity is molasses-like in consistency. When of this consistency, the material may be stretched into long filaments, if properly manipulated, in distinction from the tendency to pull apart quickly or spatter when contacted at conventional and much lower viscosities with a steam jet. The preferred viscosity of the molten material is slightly more than that of castor oil at 20 C.

For the proper drawing consistency or ductility of the material as it passes in the stream II to the filament forming operation, I have found desirable a temperature not substantially in excess of 2300 F., say, between 2200 and 2300 F. The temperature should be above that of crystallization in the mass, about 2150 F. for the composition given, and below the temperature adapted to cause the material to be non-tenacious (watery in consistency), to part quickly and spatter in the blowing operation. The temperature required to give the optimum consistency and ductility described will vary somewhat with the composition of the molten material. The temperatures stated apply to a material of the composition tabulated above as representing a typical commercial mineral wool. As there are added ingredients, such as silica, that are known to increase the viscosity in this range of temperatures, the temperature at which the stream is fed to the blowing operation is to be raised correspondingly. A few simple tests with a given composition will suflice to determine the optimum temperature.

To adjust the materialto the proper viscosity, a stream I of molten rock or slag from the conventional cupola furnace may be charged into a temperature adjustment chamber 2. This cham ber may be pivotally supported at position 3 adjacent to one end and adjustably supported at the other end as illustrated at 4, whereby the level of the fluid 5 in the chamber may be adjusted. A conventional bame 6 is used to prevent material charged at one end from flowing directly to the outlet at the other end. The outlet consists of a series ofnotches or weirs I, arranged side by side and adapted to permit the simultaneous outflow therefrom of a plurality of relatively small streams H of the fluid material.

These individual streams, of viscosity specified,

to 300 pounds.

should be small", that is, should deliver each not more than 400 pounds an hour, suitably 250 With streams of such size,'sufiicient force of steam may be applied to the out.- side of the stream to give thorough fiberizing of the material of the stream, without objectionable spattering. The temperature of the material in the chamber is adjustable by means of the burner 9. At no point in advance of 'the fiberizing should the material be alio wed to be cooled by the apparatus to the temperature of crystallization. The temperature of the material may be further controlled by gas flames 8 and I played upon the material as it flows from the outlets I. Since there is a separate burner or adjustment for each of the said outlets, the temperature of the material issuing from any outlet may be adjusted independently of the temperature of material issuing from adjacent outlets; in this way material may be blown at different viscosities simultaneously and the resulting fibres blended in the final stream.

It will be understood that cooling to adjust the material to the desired consistency for blowing may be accomplished by the steam jets l3 and/or ll contacting with the molten material flowing directly from the melting furnace. beiore the material strikes the final shredding stream oi steam.

The several streams issuing from the outlets l of Fig. 6 may be shredded individually, as by apparatus illustrated in Figs. 3 and 4. Or. all the streams, in spaced relationship to each other, may be passed through a larger shredding apparatus such as illustrated in the lower part of Fig. l, the various elements thereof corresponding to those illustrated in Figs. 3 and 4 but being of greater width.

Using the method and apparatus described. I

have been able to make a wool which is much' different from the conventional product, in containing a large proportion of long fibres and a Bil ill

decreased proportion of short fibres and "shot and being of lower density in felted form. Thus, I have been able to make a felt. slightly oiled in accordance with usual oiling methods. that weighs less than three pounds to the cubic foot, and sometimes approximately two pounds to the cubic foot. when compressed at fifteen pounds pressure to the square foot. This density is much lower than the conventional felts which, under comparable conditions. weigh usually as much as seven pounds to the cubic foot and seldom, if ever, less than four pounds. Furthermore, the fibres in my ielt are more adherent, possibly because of the greater length and possibly because oi the slight curvature formed in some of the iibres by the successive blasts of steam directed at substantial angles with respect to each other and contacting at closely. spaced intervals with the material being blown.

Having observedthe effect of my method and apparatus, various theories or explanations may be advanced to account for the results obtained. A possible explanation lies in the fact that the flow of a viscous liquid under pressure or tension has a time factor which for convenience, l have called the limit of ductility. When the viscous material in the stream being shredded is drawn too rapidly, the limit of ductility is exceeded and the material is quickly severed, since the material cannot flow sufficiently rapidly to preserve the continuity of the stream. This severance is delayed and the formation of continuous elongated masses is favored in my process,

in that the rate of stretching of the material is controlled. In place of giving to the molten material its final velocity and shredding by one sharp, sudden blast of air, as in conventional practice, I gradually step up the speed of movement and draw the material into fibres in two or three or more stages. Furthermore, the stepwise shredding gives progressively smaller streams, with each contactwith the jet of steam, so' that the final blast of steam operates on streams of material that are already small in size.

While the invention has been described in connection with the use of steam under pressure -for subdividing or fiberizing the molten material, other streams of suitable gases may be used, as, for example, heated air or flue gas or burning gases, and the term steam is used herein to include other suitable types of gaseous streams.

The term drawing, as applied to forming the fibres, includes the effects commonly referred to in the conventional process as blowing or shredding.

The terms low and high pressure, used to describe steam pressures, are relative with respect to each other. The low pressure is suitably lower than 30 pounds, frequently as low as 10 pounds, to' the square inch and the high pressure may be several times the low pressure, say, as high as 150 pounds.

Fibres are said to be long or long fibres to be present in large proportion, when the average length is greater to an important extent than the length obtained from similar compositions by using conventional processes or apparatus. It will be understood that thedetails that have been given are for the sake of illustration, not restriction, and that variations may be made within the scope of the appended claims.

What I claim is:

1. In making mineral wool, the method which comprises melting suitable raw material, adjusting the temperature of the molten material to render it of consistency suitable for shredding, into fibres, forming a stream of the molten material of the said consistency, contacting a steam jet of low velocity with the said stream so as to divide the stream, and then contacting a steam jet of high velocity with the components of the divided stream, in molten condition, the positions of initial contact of the two jets of steam with the'said stream and components, respectively, being spaced from each other by a distance of the order of 1.5 to 4 inches.

2. The method described in the immediately preceding claim which comprises directing the said steam jets at a substantial angle to each other,,so that substantially all of the material is caused to continuously undergo a sudden change of direction after having passed for a substantial distance from the position of contact with the first of the said jets, whereby appreciably curled fibres are formed.

3. In making mineral wool, the method which comprises melting suitable raw material, adjusting the temperature of the molten material to provide a consistency suitable for shredding into fibres, forming a stream of the molten material of the said consistency, contacting therewith a plurality of small substantially parallel steam jets of low velocity, to divide the stream, and then contacting a steam jet of high velocity with the components of the divided stream, in molten condition, to shred the said components into fibres.

4. In making mineral wool, the method which comprises melting suitable rawmaterial, adjusting the temperature of the molten material to render it oi consistency suitable for shredding into fibres, then forming a downwardly flowing stream of the molten material, contacting therewith a Jet of downwardly directed steam, to form a plurality of streams oi! material, and contacting with the plurality of streams, in molten condition, a shredding jet of steam directed substantially horizontally, H

5. In making mineral wool, the method which comprises melting a suitable material, forming the melted material into a small stream delivering not more than 300 pounds of material an hour, contacting with the stream a jet oi steam, to cool the material of the stream to the consistency desired for shredding, and contacting another jet of steam with the cooled but still molten stream, to shred it into fibres, the positions of initial contact of the jets of steam with the said streams being spaced from each other at a distance of the order of 1.5 to 4 inches.

6. A method of making mineral wool comprising melting suitable raw material and discharging the molten material in the form of a stream, contacting the molten material stream with a fiuid jet to divide the stream into a plurality of molten material streams, and contacting the plurality of streams with fluid moving at high velocity to convert the molten material into fibres.

'I. A method of making mineral wool comprising melting suitable raw material and discharging the molten material in the form of a stream, contacting the molten material stream with a plurality of fluid Jets to divide the stream into a plurality of molten streams, and contacting the plurality of streams with fluid moving at high velocity to reduce the molten material to fibres.

8. A method of making mineral wool comprising melting suitable raw material and discharging the raw material in the form of a stream, contacting the molten material stream with a fluid jet to divide the stream into a plurality of molten material streams, and contacting the plurality of molten material streams with a succession of fluid jets for progressively converting the molten material into fibres.

9. A method of making mineral wool comprising melting suitable raw material and discharging the raw material in the form of a stream, contacting the molten material stream with a fluid jet to divide the stream into a plurality of molten'material streams, and contacting the plurality of streams with a succession oi fluid jets having increasing velocities for progressively converting the molten material into fibres.

10. A method of making mineral wool comprising melting suitable raw material and discharging the molten material in stream form, contacting the molten material stream with a fluid jet to divide the stream into a plurality of streams of molten material and propel the streams in a general direction, and contacting the plurality of molten material streams with a continuously acting fluid jet to further divide the plurality of molten material streams into smaller streams and cause substantially all of the material to undergo a sudden change of direction.

11. A method 01' making mineral wool, comprising melting suitable raw material and discharging the molten material in stream form, and subjecting the molten material, while at a temperature and consistency suitable for shredding into fibres, to the action of a succession of steam jets spaced a predetermined distance apart along the line of flow of the stream, to act successively on said stream and to draw out and flberize the same, the initial jets being of such velocity as to perform predominantly a drawing function.

12. A method of making mineral wool, comprising'melting suitable raw material, and gradually fiberizing said molten raw material by discharging the molten material in the form of a stream and contacting the molten material, while at a temperature and consistency suitable for shredding into fibres, with a succession of steam jets, spaced a-predetermined distance apart along the line of flow of the stream, to act successively on said stream, said succession of steam jets having progressively increasing velocities, and the velocity of the final Jets being such as to fiberize the stream.

EDWARD R. POWELL.

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