IE43838B1

IE43838B1 - Method and apparatus for conversion of attenuable material into fibres

Info

Publication number: IE43838B1
Application number: IE1823/76A
Authority: IE
Original assignee: Saint Gobain
Priority date: 1976-02-09
Filing date: 1976-08-17
Publication date: 1981-06-03
Also published as: ES450747A1; AU1686376A; IL50238A; YU191976A; BE845194A; IE43838L; FR2362222A1; MX144202A; DE2636835A1; HU178094B; PL112619B1; EG12094A; SE7609056L; AU504349B2; DD125343A5; FI59979C; NZ181762A; PT65481A; RO69328A; DK369876A

Abstract

1513060 Glass or slag fibre manufacture SAINT-GOBAIN INDUSTRIES 5 Aug 1976 [9 Feb 1976] 32675/76 Heading C1M Fibres of an attenuable material (e.g. glass or slag) are made by introducing at least one stream of the material into the zone of interaction formed by one or more secondary gas jets directed from a distance transversely to a main gas blast, the jet(s) having sufficient kinetic energy to penetrate the blast and smaller lateral dimension than the blast, the stream(s) being first introduced close to the jet(s) into gas currents induced thereby to undergo initial attenuation prior to reacting the blast with further attenuation in the interaction zone.

Description

This invention relates to a method and apparatus for conversion of attenuable material into fibres by attenuating a stream of material introduced into a zone of interaction created by directing a secondary gaseous jet transversely to a main gaseous blast, the jet having a kinetic energy per unit volume sufficient to cause it to penetrate the main blast.

Such a method and apparatus is disclosed in our prior Patent Specification No. 39070 and the present invention relates to improvements in such method and apparatus.

According to one aspect of the invention, there is provided a process for conversion into fibres of an attenuable material by attenuation of at least one stream of the material introduced into a respective zone of interaction produced by directing at least one secondary gaseous jet transversely to a main gaseous current or blast the or each jet having a kinetic energy per unit volume sufficient to cause it to penetrate the main current or blast, and the lateral dimension of the main current or blast being greater than that of the or each jet, wherein the or each jet is discharged at a distance from the main gaseous current or blast and wherein the or each stream is first introduced close to the respective jet into gas currents induced thereby, the or each stream undergoing initial or partial attenuation to form a filament before reaching the boundary of the main gaseous current or blast, the or each filament being subjected to further attenuation in the respective zone of interaction to form a fibre.

According to another aspect of the invention, there is provided apparatus for the manufacture of fibres from attenuable material, comprising:- first means for delivering the material, the first means having at least one supply orifice for delivering - 2 <ί 3 8 3 a a stream of the material; second means for producing a main gaseous current or blast at a distance from the or each supply orifice and for directing the main current or blast transversely to the or each stream; and third means for producing at least one secondary gaseous jet of smaller lateral dimension than that of the main current or blast, the third means having at least one discharge orifice for directing a secondary jet towards the main current or blast, and the third means being constructed and arranged to cause the or each secondary jet to penetrate the main current or blast and thus produce a zone of Interaction between the main current or blast and the secondary jet, the discharge orifice for the or each jet and the respective supply orifice being so disposed in relation to each other that in use the or each stream encounters the jet at a location remote from the main current or blast, so that the or each stream travels with the jet to the zone of interaction thereof with the main current or blast.

The process and apparatus of the invention may operate as follows; The or each secondary jet, being emitted at a distance above the upper boundary of the main current or blast causes induction of air so that the jet forms an envelope of induced air which progressively increases in diameter as it approaches the upper boundary of the main current or blast. The jet thus comprises two parts; the core of the jet itself, which is the part emitted from the jet discharge orifice, and the main body of the jet, often referred to as mixing zone, that is to say the zone formed by the mixture of gas of the core with the induced air. - 3 43838 The core of the jet may extend from the discharge orifice for a distance amounting to 3 to 10 times the diameter of the discharge orifice, depending on the speed at which the jet leaves it. Since the discharge orifice is of small diameter, the distance along which the core of the jet is projected beyond the orifice is relatively short.

The core is conical and the mixing zone envelops it from the emission plane of the orifice, and this mixing zone, whose diameter increases progressively downstream, extends beyond the apex of the conical core. The distance between the discharge orifice and the boundary of the main blast is such that the point Cf intersection with the blast is usually situated beyond the apex of the core, although in some arrangements the core could reach close to the blast or even enter it. Whatever the arrangement, the jet should in all cases have a sufficient kinetic energy and velocity at its point of intersection with the main current or blast to enable it to penetrate the latter and thus establish a zone of interaction between itself and the main current or blast.

) This zone of interaction has the same general characteristics as the zone of interaction described in our Patent No. 39070.

Bearing in mind the above, there will now be considered a glass stream and its behaviour in relation to the secondary jet and the main current or blast. As has been stated, the stream is supplied from an orifice disposed at a distance above the main blast or current and also an appreciable distance above the discharge outlet for the jet. The supply orifice is - 4 preferably situated so that it delivers a stream which, falling by gravity, takes a direction such that it encounters the axis of the jet at a point distinctly above the upper boundary of the main blast or current and consequently also above the zone of interaction. As the stream approaches the jet, it comes progressively under the influence of the currents of induced air and is thereby forced to bend towards the jet above the point where it would otherwise have encountered it. The effect of induction forces the stream to move towards the jet and, according to the position of the glass supply orifice, this induction effect forces the stream either to enter the main body of the jet at a level downstream of the core or to enter the envelope or surrounding layers of induced air. In both cases, the stream follows a path which leads into the mixing zone and moves inside the body of the jet as it descends to the zone of interaction with the main gaseous current or blast.

The stream is thus carried by the induced air currents into the mixing zone of the jet but does not enter the core of the jet. The stream may be carried as far as the surface of the core by the induced air without being able to enter it. This is desirable to prevent fragmentation of the stream.

Since the stream is at that moment under the influence of the mixing zone of the jet, it is subjected to preliminary attenuation and its velocity increases progressively as it approaches the upper boundary of the main current or blast. - 5 43338 In addition to this attenuating action, which is aerodynamically produced, the stream is subjected in the course of this attenuation to other dynamic forces which tend to increase the attenuation effect. This results from the tendency of the stream to move towards the interior of the jet whence it is pushed back to the boundary of the jet, to be subjected to the influence of the induced air which pushes it back to the interior of the jet. These repeated impulses bring about the aerodynamic attenuating action.

The partially attenuated glass filament is then introduced into the zone of interaction between the jet and the main current or blast, partly due to acceleration of the glass by gravity and the effect of the preliminary attenuating action and partly under the influence of currents established in the zone of interaction itself as discussed in our said prior Patent referred to above.

It can be seen therefore that according to the invention the stream is subjected to two attenuating stages. It can also be seen that since the stream is subjected to the influence of the jet by virtue of the induced currents, the preliminary attenuating stage is achieved without fragmentation of the stream, and the second attenuating stage, which takes place in the zone of Interaction between the jet and the main gaseous current or blast, is also achieved without fragmentation of the fibre which is in course of formation. This two-stage technique enables long fibres to be produced.

The present invention provides advantages when compared with various known techniques. It enables long fibres to be - 6 42838 produced while at the same time enabling a greater distance to be maintained between various parts of the equipment, and in particular between the main blast generator or burner with its nozzle, the nozzle for the secondary jet and the associated means for supplying air or gas, and the means for supplying the glass, including the bushing or other equipment which has the supply orifices. This spacing apart of the various parts is not only advantageous from the structural point of view, but has the advantage of making control of the operating conditions easier and more accurate, in particular control of the temperature of the main current or blast and of the secondary jet producing means and the attenuable material supply means.

Another advantage of the invention is that the space now available between the material supply means and the zone where the material encounters the secondary jet enables a larger supply orifice to be used (which is sometimes desirable for special’ purposes or for the use of a particular material) because as the stream decends under free fall conditions, its diameter decreases under the influence of gravity and surface tension. It must be understood however that the stream is of a relatively small diameter when it is initially attenuated, and this small diameter can be obtained as a result of the free fall even if a relatively large supply orifice is used.

Another advantage results from the fact that a higher temperature can be used in the bushing or other material supply means, so that it is possible to use materials which can be attenuated at higher temperatures. In fact, during the free fall of the stream of attenuable material it is slightly cooled by its contact with the surrounding air and is reduced to a temperature suitable for the initial attenuation.

By virtue of some of the factors indicated above, the invention facilitates the use of some molten materials for the manufacture of fibres; for example slag, or formulations of glass which do not flow in a uniform manner through small supply orifices. Since it is now > possible to use larger orifices and higher temperatures, it becomes possible to achieve greater uniformity of supply and of attenuation, even with attenuable material which would otherwise be unusable in a technique for production of fibres by attenuation of a stream of molten material.

Embodiments of the invention will now be described by way of example, with reference to the drawings, in which:Figure 1 is a partial diagrammatic isometric view showing means for producing the main blast, means for producing a row of secondary jets situated above the main blast and directed downwards into it, and means for forming glass streams which descend by gravity from a zone above the jets into the zone of influence of the jets and which are finally under the influence of the zone of interaction of the jets with the main blast; Figure 2 is a diagrammatic vertical section showing one stream, one jet, and the main blast; and Figure 3 is similar to Figure 2 but showing some - 8 43838 numerical relationships to be taken into consideration when choosing the conditions which are believed to be advantageous for carrying out the invention.

Referring to the drawings, the means for delivering attenuable material in the form of molten glass comprises a crucible or bushing 1 supplied with the molten glass by, for example a forehearth 2, Figure 3. Glass outlet orifices 3 deliver streams S of molten glass which fall by gravity.

A main gaseous blast 5 is emitted in a generally horizontal direction by a nozzle 4. The main blast is produced by a generator in the form of a burner so that the blast is composed of products of combustion, with or without added air. The main blast is generally horizontal below the orifices 3.

At a height intermediate between the bushing 1 and the nozzle 4 is a row of secondary jet tubes 6 each having an outlet orifice 7, these tubes being supplied with gas from a common manifold 8 which itself may be supplied by way of a connection indicated at 9.

The gas for supplying the jet tubes 6 may be provided from a burner, and the products of combustion may serve to produce the jet, with or without added air. The combustion gases are preferably diluted with air to prevent excessive temperature of the gas in the jet tubes. - 9 42838 Each jet tube 6 and orifice 7 are arranged so that the respective secondary jet is discharged downwards from a point close to the path of the respective stream S, and preferably on that side of it which is upstream in relation to the direction of flow of the main blast 5. Further, each jet tube 6 and orifice 7 are arranged so that the respective secondary jet is directed downwards and towards the main blast, the axis of the jet being inclined to the vertical so that the projection of the path of the glass stream and the projection of the jet meet at a point some distance above the upper boundary of the main blast 5, Figure 3.

It can be seen that both the height and width of the main blast are considerably greater than the transverse dimension of each secondary jet (Fig. 1) so that an appropriate volume of main blast encounters each jet so as to produce a zone of interaction with the main blast. It is also for this reason that the kinetic energy of the jet is sufficiently high in comparison with that of the blast in the operational zone of the jet and blast to cause the jet to penetrate the blast. As indicated in our Patent No. 39070, this requires the kinetic energy per unit volume of the jet to be substantially greater than that of the blast. In addition, the jet should preferably have a considerably higher velocity than the glass stream which is falling by gravity to its point of contact with the jet, and its velocity should also be greater than that of the main blast - 10 The mode of operation will now be described.

Referring to Figure 2, the core part C of the jet causes induction of air currents indicated by lines A, the quantity of induced air progressively increasing along the -th of the jet. When the body of the jet, that is to say the gas at the core of the jet mixed with the induced air, reaches the boundary of the main blast, a zone of interaction is formed in the region indicated by the dash-dot lines 1 in Figure 2.

When the stream of molten glass S approaches the jet, the induced air currents cause a deviation of the stream towards the jet, as indicated at 10. Although the glass supply orifice 3 may be of larger diameter or cross-section than the jet orifice 7, the delivery of the stream S by gravity results in a considerable reduction in the diameter of the glass stream as shown, so that by the time the stream enters the jet its diameter will be considerably smaller than that of the glass supply orifice 3. Due to the high velocity of the jet in relation to that of the glass stream even when the stream encounters the jet in the upstream region close to the core of the jet, the glass stream does not penetrate the core of the jet. However, due to the induced air currents surrounding the jet, the glass stream is caused to ride on the surface of the core C in the envelope of induced air surrounding the jet, or to enter the body of the jet downstream of the core.

The action of the induced air in conducting the stream to the jet stabilises the delivery of the stream and compensates - 11 43838 for any small faults of alignment of the glass outlet orifice with the jet orifice. Due to the induction effect of a jet, the glass stream is conducted into the mixing zone of the gas originating in the jet core and induced air without either the stream itself or the filament formed from it being fragmented or broken. This effect is reinforced in that in the present apparatus, the glass stream is not subject to any sudden angular change of path before being subjected to any appreciable attenuation such as to reduce its diameter and inertia.

The glass stream is partially attenuated as a result of its introduction into the mixing zone of the jet. This action constitutes the first stage of the two-stage attenuation mentioned above. As a result of this partial attenuation, L5 the length of the stream, which can now be considered as a filament, is increased, and elongation is facilitated by the formation of undulations and loops 12. It should be noted however that the glass filament remains intact, the loops in this first attenuating stage being transported downwards with the descent of the filament into the zone of interaction.

The jet penetrates the main blast where it meets the blast. This penetration of the blast by the jet produces currents in the zone of interaction between the jet and blast, and these currents cause the filament or partially attenuated stream to penetrate the interior of the blast, thereby bringing about a second stage of attenuation.

This action also results in elongation of the filament during fibre formation. This increase in the length of the filament - 12 43838 is assisted by the formation of additional undulations giving rise to further even larger loops inside the main blast, as indicated at 13. The glase remains intact in spite of this action and is carried away by the main blast in the form of a fibre of considerable length. A single stream of molten glass is thus converted into a single long fibre in a two-stage attenuation operation.

It will be understood that when attenuation is carried out in two stages as described above, the temperature of the glass and the temperature of the jet, as well as the temperature of the main blast, are adjusted to values which will maintain the glass in the desired condition for attenuation during the whole of the first attenuating stage and during the whole of the second attenuating stage until the attenuation has been completed in the zone of interaction of the jet with the main blast.

It will also be understood that a row of stations as shown in Figure 1 may be used for carrying out the invention, in which case a main blast 5 will extend, or have its major dimension, in the direction perpendicular to the plane of the drawings in Figure 2 and the bushing 1 will also extend in the same fashion and have a plurality of glass supply orifices 3. There will also be provided a plurality of jet tubes 6 each having an orifice 7 adjacent one of the glass streams S. The jet tubes are supplied with gas from the common manifold 8.

Additional information relating to the general arrangements used in multiple stations and other details, for 838 f η kt a* example the means for collecting the fibres and the system for delivering glass and the main blast and secondary jet, will be found in the description relating to our Patent No. 39070. That description also includes information concerning the parameters used for producing a zone of interaction of a secondary gaseous jet with a main gaseous blast.

For information about numerical data relating to the apparatus of the invention, reference will bs made to Figure 3 in which various symbols represent various dimensions. These symbols are enumerated in the table below which also gives the standard or mean dimensions in millimetres and the permissible limits of variation for the dimensions.

Part of installation Dimension Symbol Average Value (mm) Limit of variation (mm) Bushing Diameter of glass supply orifice: DT 4 1—10 Distance between two orifices: 10 5 minimum 20 Secondary jet Internal diameter of jet tube: dfc 1 0.3—3 External diameter of jet tube: 1.5 0.7—5 !5 Distance between two tubes: 10 5 minimum Main blast nozzle: Vertical spacing of its inner walls: 1D £3 25 10—50 Width: 300 20—50 42838 In addition to the dimensions given above, certain spatial and angular relations should aleo be observed.

These will be found in the following table which gives the standard or average dimensions in millimetres or degrees and the limits of variation.

Limit of Average variations value (mm (mm or Characteristics Symbol or degree) degree) Vertical distance between discharge orifice of jet and upper boundary of main blast; ZJB 45 Vertical distance between glass supply orifice and discharge orifice of jet; ZJF 85 Horizontal distance between axis of glass stream and discharge orifice of jet: XjF 5 Horizontal distance between axis of glass stream and main blast nozzle: XgF 5 Angle of inclination of jet tube to axis of glass stream: ajp 10° Angle of inclination of jet tube to direction of flow of main blast: <*jB 80 —60 0-150 1—15 0—30 3°—45 87°—45° Concerning the parameters for carrying out the process of the invention, it is noted that the glass should be delivered from its orifice at a stable and continuous rate. For this purpose, the rate of flow of glass, the temperature of the bushing and the diameter of the glass supply orifice should preferably have values above certain a priori established limits. Thus, the rate of flow of glass should be above 60kg per orifice for each 24 hour period, the temperature of the bushing should be above 125O°C and the diameter of the glass supply orifice should be above 2.5 mm. By observing these limits it is possible in the case of certain glass compositions to prevent irregularities which tend to increase to the point of formation of distinct drops. This LO phenomenon would be incompatible with acceptable fibre formation.

The following values may be applied under standard or average operating conditions:100 kg per orifice per day, a. temperature of 1400°C L5 for the bushing and a glass supply orifice of diameter 3 mm.

Additional data about operating limits are given below:- Velocity: Secondary jet: 200 m/seo—900 m/seo Main blast: 200 m/sec—800 m/sec Pressure: Secondary jet: 0.5 to 50 bar Main blast: 0.05 to 0.5 bar Temperature: Secondary jet: 20°C to 1800°C Main blast: 1300°C to 1800°C Ratio of kinetic Secondary energies 5 jet 10/1 to 1000/1 Main blast The following example gives a glass formulation which may be used in carrying out the invention: - 16 Example 4Ξ838 SiO? 46.92Fe2°3 1.62 ^2θ3 9.20 MnO 0.16 CaO 30.75 MgO 3.95 Na20 3.90 k2° 3.50 (all In parts by weight) Physical properties; Viscosity: 30 poises at 1310°C 100 poises at 1216°C 300 poises at 1155°c Glass: Orifice: 3 mm Temperature: 1400°C Plow Rate: 100 kg/day per orifice Main blast: Temperature: 1550°C Pressure: 0.25 bar Velocity: 530 m/s Secondary jet: Temperature: 2O°C Pressure: 6 bars Velocity: 330 m/s Diameter of jet orifice: 1 mm Secondary jet Ratio of kinetic - 24 energies : Main blast 1 Diameter of

Claims

1. CLAIMS:1. A process for conversion into fibres of an attenuable material by attenuation of at least one stream of the material introduced into a respective zone of interaction produced by directing at least one secondary gaseous jet transversely to a main gaseous current or blast,the or each jet having a kinetic energy per unit volume sufficient to cause it to penetrate the main current or blast, and the lateral dimension of the main current or blast being greater than that of the or each jet, wherein the or each jet is discharged at a distance » from the main gaseous current or blast and wherein the or each stream is first introduced close to the respective jet into gas currents induced thereby, the or each stream undergoing initial or partial attenuation to form a filament before reaching the boundary of the main gaseous current or blast, the or each filament being subjected to further attenuation in the respective zone of interaction to form a fibre.

2. A process according to claim 1 wherein the or each jet is in a position which in relation to the direction of flow of the main current or blast is upstream of the or each stream of ι attenuable material.

3. A process according to claim 2 wherein the or each jet is at an angle to the vertical and intercepts the path of the or each stream at a location anove the upper Boundary of the main current or blast.

4. A process according to claim 1 wherein the or each stream of attenuable material falls by gravity from a point substantially above the level at which the stream is brought into contact with the respective jet. - 18

5. A process according to claim 4 wherein the direction o£ the or each jet ie at an angle of from 3 to 45° with the direction of the respective stream.

6. A process according to claim 5 wherein the angle is 10°.

7. A process according to any of claims 4 to 6 wherein the or each stream is delivered from a point above the zone where it is introduced into the gas currents induced by the respective jet, the stream, in its flow from the said point to the zone of introduction, undergoing a reduction in diameter before reaching the zone of introduction.

8. A process according to any preceding claim wherein the cross-sectional area of the or each stream of attenuable material in the region where it comes into contact with the respective jet is less than or equal to that of the jet.

9. A process according to any preceding claim wherein the attenuable material is a thermoplastic material.

10. A process according to claim 9 wherein the material . is glass.

11. Apparatus for the manufacture of fibres from attenuable material, comprising:first means for delivering the material, the first means having at least one supply orifice for delivering a stream of the material; second means for producing a main gaseous current or blast at a distance from the or each supply orifice and for directing the main current or blast transversely to the or each stream; and £r 838 third means for producing at least one secondary gaseous jet of smaller lateral dimension than that of the main current or blast, the third means having at least one discharge orifice for directing a secondary jet towards 5. The main current or blast, and the third means being constructed and arranged to cause the or each secondary jet to penetrate the main current or blast and thus produce a zone of interaction between the main current or blast and the secondary jet, the discharge orifice for the or each > jet and the respective supply orifice being so disposed in relation to each other that in use the or each stream encounters the jet at a location remote from the main current or blast, so that the or each stream travels with the jet to the zone of interaction thereof with the main current or blast.

12. Apparatus according to claim 11 wherein the first means is so disposed that the or each stream falls therefrom, wherein the second means discharges the main current or blast a distance from, and below, the or each supply orifice, and wherein the or each discharge orifice of the third means directs the respective jet downwards of the main current or blast.

13. Apparatus according to claim 11 or claim 12 wherein the third means is upstream of the stream or streams of attenuable material in relation to the main current or blast.

14. Apparatus according to any of claims 11 to 13 wherein - 20 42838 the third means is arranged obliquely so as to cause the or each jet to penetrate the main current or blast in a zone which is spaced horizontally in relation to the respective supply orifice.

15. Apparatus according to any of claims 11 to 14 wherein the third means is so disposed as to direct the or each jet along a path which is at an angle of 45 to 87° to the direction of flow of the main current or blast.

16. Apparatus according to any of claims 11 to 15 wherein the distance between the or each discharge orifice and the upper boundary of the main current or blast is from 30 to 60 mm.

17. Apparatus according to claim 16 wherein the distance is 45 mm.

18. Apparatus according to any of claims 11 to 17 wherein the diameter of the discharge orifice for the carrier jet is from 0.3 to 3 mm.

19. Apparatus according to claim 18 wherein the diameter is 1 mm.

20. Apparatus according to any of claims 11 to 19 wherein the vertical distance between the or each supply orifice and the respective discharge orifice is not more than 150 mm.

21. Apparatus according to claim 20 wherein the vertical distance is 85 mm.

22. Apparatus according to any of claims 11 to 21 wherein the or each supply orifice is of diameter of from 1 to 10mm.

23. Apparatus according to claim 22 wherein the said diameter is 4 mm. - 21 43838

24. Apparatus according to any of claims 11 to 23 wherein the or each discharge orifice and the respective supply orifice are spaced apart in the direction of flow of the main current or blast a distance of from 1 to 15 mm.

25. Apparatus according to claim 24 wherein the said distance is 5 mm.

26. Apparatus according to any of claims 11 to 25 wherein the dimension of the outlet of a burner producing the main current or blast, measured in the direction of delivery of the attenuable material, is from 10 to 50 mm.

27. Apparatus according to claim 26, wherein the said distance is 25 mm.

28. Apparatus according to any of claims 11 to 27 wherein the distance of the axis of the or each stream from the burner outlet, measured perpendicularly to the direction of delivery of the stream, is not more than 30 mm.

29. Apparatus according to claim 28 wherein the said distance is 5 mm.

30. A process for producing fibres from attenuable material substantially as herein described with reference to the drawings.

31. Apparatus for producing fibres from attenuable material, constructed and arranged substantially as herein described and shown in the accompanying drawings.

32. Fibres whenever manufactured by a process according to any of claims 1 to 10 and 30 Or by apparatus according to any of claims 11 to 29 and 31