CA1274394A - Non-circular mineral fibers and method and apparatus for making - Google Patents

Abstract

ABSTRACT OF THE DISCLOSURE

A method and apparatus are disclosed for making non-circular mineral fibers, as well as the fibers produced thereby. The method comprises flowing a stream from a body of molten mineral material through a non-circular orifice, and quenching the mineral material in the stream to form a mineral fiber having a non-circular cross-section.

Description

39~

~his invention pertains to mineral fibers and the manufacture of mineral fibers for such uses as textiles, reinforcements, construction ma-terials, and insulating materials. With respect to this invention, the term "mineral fibers" means fibers of glass, rock, slag or basalt. In one of its more specific aspects, this invention pertains to non-circular mineral fibers and, in particular, non-circular glass fibers.
The production of wool gla~s fibers by means of lo the rotary process is well known. In general, molten glass is fed into a spinner which revolves at high speeds.
The spinner has a peripheral wall c?ontaining a multiplicity of orifices. Molten glass passed by centrifugal force through the orifices of the peripheral wall forms small diameter molten glass streams.
Positioned circumferentially about the spinner is an annular blower for turning the fibers downwardly and, in some cases, for further or secondary attenuation of the original or primary fibers to produce fibers of smaller diameter. As the streams of molten glass are emitted from the orifices, they are still sufficiently nonviscous that surface tension forces pull or shape each of the molten `~ streams into substantially circular cross-sections, regardless of the cross-sectional shape of the streams as

2~ they are emitted from the orifices. Further, rotary fiberizers are typically equipped with annular burners or other sources of hot gases for secondary attenuation of the primary fibers; thes~ hot gases keep the `~Y~
,~
`~

`~? ` ' . : .

'' ' : ' :
.. ' . : " ' , `'` ' ' ~ ' ' ` ' ' ~ ' ', :' 1 glass sufficiently fluid or nonviscous that fibers of substantially circular cross-section result.
The production of textile or continuous glass fibers by mechanicall~ drawing molten streams of glass from orifices in the bottom wall of a bushing or feeder is also well known. Non-uniformities in the roundness of the molten streams tend to be corrected by surface tension forces prior to the cooling and hardening of the molten streams into glass fibers. Thus, as in the case of wool glass fiber production, it has not been possible to produce significantly non-circular continuous fibers using shaped orifices in a bushing.
There has long been a need for producing fibers, both in the rotary process and in the continuous fiber process, that have significantly non-circular cross-sections. With respect to reinforcement of resin `
matrices, such non-circular fibers would be useful in imparting greatly increased transverse strength and improved shear strength qualities. Non-circular fibers for use as insulation materials would be advantageous in that the increased surface a~ea per unit volume of glass would lower the thermal conductivity of insulation made from such fibers.
A measure of the non-circularity of mineral fibers is the "mod ratio", which is deined as the ratio of the diameter of the smallest circle into which the fiber cross-section fits to the diameter of the largest circle which can fit inside the fiber cross-section. As employed herein, fibers having a mod ratio of less than 1.2 are referred to as circular fibers; fibers having a mod ratio greater than or e~ual to 1.2 are referred to as non-circular fibers.
One attempt to make non-circular glass fibers was by Warthen, as described in U.S. Patent No. 3,063,094 Warthen's method employs mechanical perturbation of the glass stream while it is still in a plastic, ~eformable state. Warthen teaches that to cxeate a non-circular fiber, - . : ................. , .: -. - - :. . .
.-, .

7~39'1 1 the glass stream, initially in a conical shape with a circular cross-section, should be distorted at a region where the viscosity of the stream is sufficiently high as to become rapidly chilled or solidified during attenuation of the streams to a continuous fiber whereby a similar distortion in the cross-sectional configuration is retained in the attenuated solidified fiber. Warthen also teaches that a heat sink is to be applied to the glass stream by direct contact. This raises the viscosity of the molten glass to better enable retention and perpetuation of the non-circular cross-sectional character of the mechanically perturbed molten glass stream.
In the art of producing organic fibers, it is a common practice to use quenching methods to solidify molten streams o organic material into non-circular cross-sections which are similar to the shapes of the non-circular orifices. However, these methods are practical under conditions which differ greatly from conditions associated with forming mineral fibers. The production of organic non-circular fibers can be facilitated by pressurization of the bushings, whereas pressurization of bushings containing molten glass presents severe operating problems. The melting points of glass and organic compositions differ by 1500F (815C) or more. The mineral material of this invention will have a liquidus temperature greater than about 1200~F (649-C), whereas organic compositions soften - and/or decompose at much lower temperatures.
The differences in physical characteristics can be clearly understood by comparing the ratio of viscosity-to-surface tension ~or glass with the same ratio for organic fiber formin~ material. The viscosity-to-surface tension ratio ~poises/(dynes/cm)) of polymers lies within the range of from about 25 to about - 5000. The ratio for glass is within the range of from about 0.1 to about 25, preferably within the range of from about ~25 to about 15, and most preferably within the range of from about 0.4 to about 10. The viscosity of molten glass ~7~

at fiber forming temperatures is typically about 300 poi~e whereas the viscosity of the molten organic material is typically on the order of about 1000 to about 3000 poises.
~150, the surface tension forces of glass (on the order of about 250 to about 300 dynes/cm) are an order of magnitude greater than those of the organic material (about 30 dynes/cm). The lower viscosity and higher surface tension of glass make it about 100 times more difficult to preven-t the shaped glass fibers from re-forming into glass fibers having circular cross-sections.
In spite of pa.st attempts to manufacture non-circular mineral fibers, there has never been a commercially successful method or apparatus for achieving the goal of making non-circular fibers from non-circular orifices.
Accordingly, one aspect of the invention provides the method of making non-circular ~ineral fibers having a mod ratio greater than about 1.2 comprising discharging molten mineral material having a liquidus greater than about 1200~F (649C) from non-circular orifices to produce molten streams of non-circular cross-section, said non-circular orifices being positioned in a wall of a container for holding a body of molten mineral material and the mineral material in said streams having a low enough initial viscosity that said steams would assume circular cross-sections in the absence of quenching, and quenching said streams to harden them into mineral fibers having a non-circular cro~s-sectional shape similar to the shape of said orifices before the stream~ can assume circular ~ross sections.
Another aspect of the invention provides apparatus for making non-circular mineral fibers having a mod ratio greater than about 1.2 comprising an orifice bushing wall for discharging one or more stream6 of molten mineral material having a liquidus greater than about 1200F (649C), said orificed bushing wall being positioned in a container for holding a body of molten mineral material and the mineral material in said strea~s ` ' ' ' ' : '- ' , " .
~ '' ' ' , :
- . . ,,- : . .:. :
- . ~ ' . . , - ~

~X~3~

having a low enough initial viscosity that said streams would assume circular cross-sections in the absence of quenching, the or~fices having a mod ratio within the range of from about 1.3 to about 25, and means for quenching said streams to form mineral f ibers having a non-circular cross-sectional shape similar to the ~hape of said orifices.
Thus, it has now been found that mineral fibers, such as glass fibers, can be produced with non-circular cross-sections by dischargin~ streams of molten mineral material from non-circular ori~ices and forcibly quenching the steams sufficiently fast to harden them into non-circular mineral fibers. This forcible cooling of the streams hardens them into fibers with non-circular cross-sections beore surface ten~ion forces can cause the stream~ to assume circular cross-sections. The rapid cooling aspect of this invention e~ables the production of mineral fibers having higher mod ratios than those practically feasible with the processes of the prior art.
The invention can be employed in both the rotary process and in a continuous fiber process.
Although the preferable means for quickly quenching the streams is a relatively cold (e.g. room temperature) gaseous flow, such as air, directed into contact with ~he st~eams, any suitable means for rapidly cooling the streams, such as fluid flow, water spray, liquid bath, ultr~sonics or fin shields, can be employed.
Streams having greater mod ratios will, in general, h~ve greater surface areas ~i.e., greater perimeter of the stream cross-section) and hence greater heat transfer characteristics (and quench rates) than those streams with lesser mod ratios. When using a cooling gas, the temperature and velocity of the cooling gas flow al50 a~fect the quench rate, as does the velocity of the streams and the time required for passage of the streams throu~h the quenching gas flow as well as the distance traveled before the streams are hardened in-to fibers.

' ~

~, . , - . ,: , --- ~
- . .. .
: :

~ ~74~

The mineral fiber forming process of this invention can be effected by numero~ variables, including inertia forces (hydrostatic head or pressurization in a textile process; hydrostatic head forces in a rotary procecs), body force~ in a rotary process, initial temperature and viscosity of the mineral material, thickne~s or depth of the non-circular orifice, surface tension characteristics of the molten mineral material, - speed at which the streams are -traveling, and the rate a-t which the streams are quenched.
Pressurization of the body of molten glass, or the inertial force on the glass from the spinner, or the mechanical pulling force in a continuous fiber process, can affect the ultimate mod ratio of the mineral fibers.
To the extent that surace tension forces start to act to re-form the streams into circular cross-sections before the streams reach the cooling gas flow, the source of which may be positioned some distance below the non-circular orifices, the time for the streams -to each the region of the cooling gas flow may be critical.
As mentioned above, the method of making non-circular mineral fibers comprises discharging molten mineral material from non-circular orifices to produce streams of non-c.ircular cross-section, and cooling the streams to harden them into fibers having a non-circular cross-sectional shape similar to the shape of the orifices before the streams can assume a circular cross-section. A
plurality of such orifices can be positioned in a wall of a container for a body of molten mineral material. The container can be, for example, a spinner or a feeder.
: In one embodiment of the invention, the quenching of the mineral material is effecte~ by directing a cooling fluid into contact with the glass stream in an amount and at a locus sufficient to prevent the material from assuming a circular cross-section.
The apparatus of the invention for making non-circular mineral fibers comprises an orificed bushing for discharging one or more streams of molten mineral ` ~

` '`` ' ~, .

~7~

material, the orifices advantageously having a mod ratio greater than about 1.2, and mean~ for quenching th2 streams to form mineral fibers having a non-circular cross-sectional shape similar to the shape of the orifices. Preferably, the orific~s have a mod ratio within the range of from about 1.2 to about 50, more preferably within the range of from about 1.3 to about 25, and most preferably within the range of from about 1.7 to about 10. The orifices can be trilobal, with the three lobe~ being generally, evenly, angularly spaced from each other.
Embodiments of the invention will now be described, by way o~ example, with reference to the accompanying drawing3, in which:
Figure 1 is a schematic view in elevation of one apparatus for forming continuous non-circular glass fibers from a bushing according to the principles of the invention;
Figure 2 is an upward plan view of a bushing bottom plate containing an array of non-circular orifices;
Figure 3 is a perspective view of a non-circular orifice of Figure 2, and a non-circular glass fiber being formed;
Figure 4 is a graph of fiber charac-teristics as a function of distance from the bushing;
E'igure 5 is a schematic vlew in elevation of a non-circular orifice according to the pri~ciples of the invention;
Figures 6 through 9 illustrate non-circular cross-sections of glass fibers made under various conditions of quenching;
Figure 10 is an enlarged cross-sectional view of the trilobal glass fiber of Figure 9;
Figure 11 is a graph indicating the relationship between the mod ratlo and quench velocity;
Figure 12 is an isometric view in perspective of a resin matrix reinforced with non-circular fibers;
. ~

. ~

- :
- , ' ~ ' ` ' :

:
- . :

~L~7~39 ~a Figure 13 is an enlarged isometrlc view in perspective of three of the trilobal fibers of Figure 12;
Figure 14 is an upward plan view of a bushing bottom wall containing both circular and non-circular orifices;
Figure 15 is a schematic cross-sectional view in elevation of the invention applied to a rotary process;
Figure 16 is a schematic view in elevation of the spinner of Figure 15;
Figure 17 is an enlar~ed cross-sectional view of a crescent-shaped fiber produced on the apparatus of Figures 15 and 16; and Figure 18 is a plan view of an embodiment of a tipped non-circular orifice.
This invention will be described in terms of a glass fiber forming process and apparatus, and products made therefrom, although it i-q to be understood that the process is suitable for fibers of other mineral materials, particularly of such mineral materials as rock, slag and basalt.
As shown in Figure 1, molten ~lass streams 10 are emitted from orificed bushing bottom wall 12 of feeder or bushing 14, and are drawn into fibers 16 by any - suitable means, such as by the mechanical action of winder 18. Gathering shoe 20 and size applicator 22 can be employed in the manner well known in the art. The bushing contains a body of molten glass 24 from which the streams of molten ' ' ' ~ .
, ,: - -~ ~ .

~7~35a~

1 glass are drawn. As illustrated, air nozzles 26, which are means for quenching the streams of molten glass, are positioned to direct air into contact with the molten streams as they are emitted from the bushing bottom wall.
The air flow cools the molten streams quickly enough into glass fibers so that they retain the general non-circular shape o~ the molten streams. Other sui~able cooling fluids, such as carbon dioxide, nitrogen, steam or water, can be employed to forceably cool the streams.
As shown in Figures 2 and 3, the bushing bottom wall contains trilobal orifices 28, having the lobes positioned evenly around the periphery. The orifices and the resulting ibers can be of various shapes, such as, for example, cross-shaped, star-shaped, pentalobal, octalobal, or rectangular.
In order to ~uantitatively describe the formation of non-circular glass fibers, it is useful to consider a time constant r for the decay of the shape from non-circular cross-section back to circular cross-section.
As soon as a molten glass stream of non-circular cross-section flows from a non-circular orifice, surface tension forces act on the stream to change it into a circular cross-section. Opposing these forces are viscous forces, which tend to resist changes in the shape of the stream. The viscous forces increase extremel~ rapidly because of cooling as the molten glass in the stream moves away from the orifice. In order to successfully make non-circular fibers, the viscous forces (i.e., the viscosity) must be increased quickly enough to retard the effect of the surface tension forces.
The time constant is believed to be the function of the viscosity of the glass, the e~uivalent radius of the glass stream, and the surface tension, according to the e~uation: r - ~r/ ~ . This equatior. can be transformed - 35 with a velocity ~actor to enable integration over distance along the fiber, i.e., vertical distance downward from the orifice, instead of with respect to time. In operation, 741;~
g 1 when only a few time constants pass prior to the hardening or greatly increased viscosity of the glass, the fiber still main-tains its non-circular shape. When many time constants pass, however, prior to reaching high viscosity, the glass stream returns to a circular cross-section and produces a circular fiber. When the inverse of the time constant is integrated over the distance to 100~ attenuation, the ratio of the time-to-become-viscous to the time-to-revert-to-a-circular-cross-section is obtained.
This ratio, di~icult to measure exactly, can be estimated by the ratio Z, as given by the following equation:
750~0~rO reo) (l/vo) * l/(MRo -1) where:
X75 is the distance from the bushing at 75 percent attenuation (cm);
is the initial viscosity (poise);
reO is the initial equivalent fiber radius (cm);
is the initial surface tension of the mineral material (dynestcm);
~ 20 vO is the initial velocity (cm/sec) through the -~ orifices; and MRo is the initial mod ratio of said streams.
The factor 1/(MRo -1) is a ~actor indicative of the mod ratio of the hole, and hence the initial mod ratio of the glass stream. It has been found that this equation correlates very well with theoretical considerations as shown in Figure 4 where the curve represents the reciprocal of the time constant as a function of distance from the bushing. The integral is the area underneath the curve, and the smaller the area underneath the curve, the smaller the number o~ time constants experienced by the stream before hardening and therefore the greater the mod ratio. It has been found that in order for the final ~iber to be non-circular, Z should be less than or equal to 2, and preferably less than or equal to 1.
The inertia ~orces or glass pressure at the ori~ices can af~ect the extent to which non-circular ~ibers '7~3~a~

1 can be formed. The pressure can be produced by any means, such as the hydrostatic head of the molten glass, gas pressurization of the feed~r, or a combination of both. For the production of continuous glass fibers, the hydrostatic pressure is preferably within a range of from about 0.4 psig (2,800 Pascals) to about 100 psig (690,000 Pascals). Most preferably, the molten mineral material will be subjected to a hydrostatic pressure within the range of from about 0.7 psig (4,800 Pascals) to about 5.0 psig (34,000 Pascals).
Although the bushing shown in Figures 1~3 contains tipless orifices, the invention can be performed with tipped orifices as well. The orifice in Figure 5 has depth "t".
It has been found that shallower or less deep ori~ices enable an improvement or increase in the mod ratio of the non-circular fibers. Preferably, the depth of the orifices is within the range of from about .001 in. (.025 mm) to about .250 in. (6.4 mm).
The mineral fibers produced according to this invention will, in general, have equivalent diameters within the range of from about .2xlO 5 in. (.05 microns) to about 300xlO 5 in. (76 microns), although non-circular fibers outside this range are possible. Preferably, the mineral fibers are within the range of B to Y filaments, i.e., within the range of from about lOxlO 5 in. (2.5 microns3 to about 120xlO in. (30 microns). Most preferably, the mineral fi~érs of this invention are G through T ~ilaments, within the range of from about 35xlO 5 in. (8.9 microns) to about 95xlO 5 in. (24 microns).
Figures 6 through 9 illustrate cross-sections of four non-circular fibers produced from apparatus similar to that shown in Figures 1-3. These fiber cross-sections are all similar in shape to the trilobal orifice. The apparatus was controlled at substantially constant operating conditions except for the velocities of the quenching fluid.
The velocities were different for each of the ~ibers. It is believed that the rate at which the molten glass streams is cooled is a function of the velocity of the ~uenching medium , ~27~3~

1 when all other conditions are equal. Fiber 16a in Figure 6 was produced with a quench air velocity at the bushing orifice of approximately 1~ meters per second, and has a mod ratio of about 1.35. Non-circular fiber 16b shown in Figure 7 was produced with a quench rate of approximately 15 meters per second, and has a mod ratio of about 1.45. Fiber 16c shown in Figure 8, having a mod ratio of about 1.75, was produced with a quench rate of approximately 20 meters per second. Non-circular fiber 16d shown in Figure 9, having a ~ mod ratio of about ~.70, was produced with a ~uench rate of approximately 30 meters per second. Although quench velocities of up to 60 meters per second, or more, could possibly be used with the invention, it has been found that the preferred quench velocity of room-temperature (approximately 80 F, 27 C) air is below about 40 meters per secon~. Most preferably, the quench rate is within the range of from about S to about 30 meters per second. These quench velocities are in contrast to those used in normally operating air-quenched bushings used to prevent flooding, which have quench rates at the bushing tips on the order of about 2 to 4 meters per second.
As shown in Figure 10, the dimensions of non-circular fiber 16d can be characterized by using the mod ratio, which is the outer diameter Do divided by the inner diameter Di. The outer diameter is the smallest circle into which the entire cross-section can be placed. The inner diameter is the largest circle which can be positioned within the fiber cross-section.
As shown in Figure 11, the mod ratio in~reases with an increase in the quench velocity. It is also shown that when the bushing is pressurized, the mod ratio increases.
As shown in Figures 12 and 13, continuous trilobal fibers 16d can be made and positioned in a matrix, such as plastic resin 3~, for reinforcement. The mineral fibers o~
this invention can be used to rein~orce any organic or inorganic matrix suitable for use with other types of 1 reinforcement. For example, thermoplastic or thermoset resins, such as polyesters or epoxies, could be used.
Cements, low melting point metals, and silicate matrices could also be reinorced. Matrices reinforced with non-circular mineral fibers of this invention could also be simultaneously rein~orced by any other suitable reinforcement, such as circular mineral fibers or organic fibers.
As shown in Figure 14, the bushing bottom wall 12 can contain both non-circular orifices 28a and circular orifices 34 to produce strands of fibers, some of which have circular cross-sections and some of which have non-circular cross-sections.
As shown in Figure 18 a tipped bushing can be used to produce non-circular fibers of the invention. The three legs 54 of the orifice have enlarged leg ends 56. The orifice is formed in the bottom end of a ciosed end tube tip 58.
When the invention is carried out using the rotar~
process, the "container" is a spinner rather than a feeder or bushing, and the non-circular orifices are positioned in the spinner peripheral wall rather than in the bushing bottom wall.
As shown in Figure 15, molten glass 40 can be supplied to rotating spinner 42. The molten glass impinges on bottom wall 44 of the spinner and flows outwardly by centrifugal force to the spinner peripheral wall 46. The spinner peripheral wall contains non-circular orifices 48 through which molten streams of glass 50 emanate. The relative motion of the glass streams emanating from the spinner and the air surroundiny the spinner results in a quenching of the molten streams into glass fibers 52. To some extent, the rate of quenching can be controlled by the rotational rate of the spinner. An annular blower, such as

3~ blower 54, can be positioned concentrically around the spinner to turn the fibers down for collection of the fibers, which can be by conventional means.

~7~ 4 1 The spinner can be adapted with non-circula~
orifices of various shapes, such as slots or crosses, and in various configurations. As shown in Figure 16, the spinner can be adapted with crescent-shaped orifices to produce glass fiber 52 having the cross-sectional shape shown in Figure 17.

Continuous E glass trilobal fibers having an average mod ratio of about 2.3 were made from a tipless bushing having 20 trilobal orifices under the following conditions:
Trilobal Qrifice size:
depth: .015 in. (.38 mm) width of each leg: ~009 in. (.23 mm) length of each leg to center of orifice: .027 in. (.69 mm) Glass temperature = 2190 F (1200 C) Glass type: 200E
Bushing pressure (total): 8.7 psig (60 KPa) Glass flow rate: .034 lb/hr/hole (0.26 g/min/hole) Number of filaments: 20 Hole pattern: 2 rows, 10 holes/row, staggered pattern sp~cing between rows: .125 inch (3.18 mm) hole spacing along row: .120 inch (3.05 mm) Quench medium: air at 80F (27C) Quench nozzle size: 1.5 in. (38.1~n) horizontal ~ .25 in.
(6.35mm) vertical Quench nozzle position: 1 inO (25mm) from center line of bushing (center line between two rows) 15 degree angle ~rom horizontal Quench nozzle flow rate: 300 scfh (10.2 kg/hr) Quench velocity: 32 ft/s (9.8 mts~ at ~uench nozzle 29-32 ft/s (8.8-9.8 m/s) at bushing center line (very little velocity decay, if any) Winder speed: 1550 ft/min (7.87 m/s) ~ ;~74~

1 Average fiber diameter: M filament 65 HT 116.5 microns) based on cross-sectional area EXAMPLES II & III
Continuous E glass trilobal fibers were made with a 14 hole tipped bushing using finshield quench. The tips were closed end tube tips with orifices of the design shown in Figure 18 machined in the tip bottom. The particular dimensions of the design used determined the final fiber mod ratios. The following conditions pertained to all tips:
Tip tube diameter: 0.130 in. (3.3 mm) Tip tube length: 0.240 in. (6.1 mm) Tip end thickness (depth of orifice): 0.011 in. tO.28 mm) Tip pattern: 2 rows, 7 tips/row, straight pattern spacing between rows - 0.030 in. (7.6 mm) tip spacing along row - 0.23 in. (5.8 mm) Finshield geometry: fin thickness - 0.055 in. (1.4 mm) fin height - 0.625 in. (15.9 mm) fin length - 1.68 in. (42.7 mm) fin blade spacing - 0.23 ln. (5.8 mm) Glass type: 20OE
Glass temperature: 2250F (1230C) Bushing pressure (total): 1.1 psig (7.6 KPa) Winder speed: Approximately 750 ft/min (3.81 m/s) This varied somewhat during the ;
experiments.
EXAMPLE II
Hole dimensions: D - 0.025 in. iO.64 mm) P - 0.020 in. ~0.51 mm) W - 0.010 in. (0.25 mm) Glass flow rate: 0.018 lb/hr/hole (0.14 gm/min/hole) Average fiber diameter: N filament, 70 HT (17.8 microns) Average mod ratio: 2.2 EXAMPLE III
Hole dimensions: D - 0.025 in. (0.64 mm) 3~ P - 0.020 in. (0.51 mm) ~ - 0.005 in. (0~13 ~n) ~7~3~

1 Glass flow rate: 0.0141b/hr/hole (0.106gm/min/hole) Average fiber diameter: 1 filament, 59 HT (14.9 microns) Average mod ratio: 5.3 It will be evident from the foregoing that various modifications can be made to this invention. Such, however, are considered as being within the scope of the invention.
INDUSTRIAL APPLICABILITY
-This invention will be found to be useful in the production of glass fibers for such uses as thermal and acoustical insulation products, and reinforcements for resin matrices.

lS

-- .

:

Claims (12)

C L A I M S

1. The method of making non-circular mineral fibers having a mod ratio greater than about 1.2 comprising discharging molten mineral material having a liquidus greater than about 1200°F (649°C) from non-circular orifices to produce molten streams of non-circular cross-section, said non-circular orifices being positioned in a wall of a container for holding a body of molten mineral material and the mineral material in said streams having a low enough initial viscosity that said streams would assume circular cross-sections in the absence of quenching, and quenching said streams to harden them into mineral fibers having a non-circular cross-sectional shape similar to the shape of said orifices before the streams can assume circular cross sections.

2. The method of claim 1 in which the ratio of the viscosity (poises) to the surface tension (dynes/cm) is within the range of from about 0.1 to about 25.

3. The method of claim 1 in which said non-circular orifices are positioned in a bushing wall of a feeder for forming continuous glass fibers.

4. The method of claim 1 in which said non-circular orifices are positioned in the peripheral wall of a spinner for centrifuging mineral fibers.

5. The method of claim 3 in which the molten mineral material in said bushing at the orifices has pressure within the range of from about 0.4 psig (2,800 Pascals) to about 100 psig (690,000 Pascals).

6. The method of claim 3 comprising quenching said streams by directing a cooling fluid into contact with said streams.

7. The method of claim 6 comprising quenching said streams with fin shields.

8. The method of claim 3 in which said quenching step is sufficient to satisfy the equation: Z ? 2 where:
Z(X75 ? o/µo reo) * (1/vo) * 1/(MRo -1) and where:
X75 is the distance from the bushing at 75 percent attenuation (cm);
µo is the initial viscosity (poise);
reO is the initial equivalent fiber radius (cm);
?o is the initial surface tension of the mineral material (dynes/cm);
vo is the initial viscosity (cm/sec) through said orifices; and MRo is the initial mod ratio of said streams.

9. Apparatus for making non-circular mineral fibers having a mod ratio greater than about 1.2 comprising an orificed bushing wall for discharging one or more streams of molten mineral material having a liquidus greater than about 1200°F (649°C), said orificed bushing wall being positioned in a container for holding a body of molten mineral material and the mineral material in said streams having a low enough initial viscosity that said streams would assume circular cross-sections in the absence of quenching, the orifices having a mod ratio within the range of from about 1.3 to about 25, and means for quenching said streams to form mineral fibers having a non-circular cross-sectional shape similar to the shape of said orifices.

10. The apparatus of claim 9 in which said bushing wall is positioned in a feeder for forming continuous glass fibers.

11. The apparatus of claim 9 in which said orificed bushing wall is the peripheral wall of a spinner for centrifuging mineral fibers.

12. The apparatus of claim 10 in which said means for quenching comprises fin shields.