FR2594432A1 - Noncircular inorganic fibres and process and apparatus for their manufacture - Google Patents

Abstract

Process and apparatus for manufacturing noncircular inorganic fibres 16 and fibres produced by this process and this apparatus. This process consists in passing a jet 10 through a noncircular orifice 28 starting with a mass of molten inorganic substance 12 and in cooling the inorganic substance of the jet to form an inorganic fibre 16 which has a noncircular section.

Description

NON-CIRCULAR MINERAL FIBERS
METHOD AND APPARATUS FOR THEIR MANUFACTURE
The present invention relates to mineral fibers and the manufacture of mineral fibers for use as textiles, reinforcements, building materials, and insulating materials.

In the context of the present invention, the expression mineral fibers means glass, rock, slag or basalt fibers. In one of its more specific aspects, this invention relates to non-circular mineral fibers and, in particular, non-circular glass fibers.

The production of glass wool fibers by means of the rotary process is well known. In general, molten glass is loaded into a rotating spinning machine which rotates at high speeds. The rotary spinning machine has a peripheral wall provided with a multitude of orifices. The molten glass that a centrifugal force requires to pass through the orifices of the peripheral wall forms streams of molten glass of small diameter. An annular blower is circumferentially positioned around the rotary spinning machine to fold the fibers down and, in some cases, to perform additional or secondary refinement of the initial or primary fibers to produce fibers of greater diameter. When they come out of the orifices, the jets of molten glass are still sufficiently non-viscous for superficial tension forces to pull or shape each.
from them to give them substantially circular sections, regardless of the section configuration of the jets at the moment they leave the orifices. In addition, rotary fiber machines are typically equipped with ring burners or other hot gas sources for secondary refinement of the primary fibers; these hot gases keep the glass sufficiently fluid or non-viscous for. that results in fibers of substantially circular section.

 The production of textile or continuous glass fibers by mechanical drawing of molten jets of glass emerging from orifices in the lower wall of a die or feed apparatus is also well known. Molten jet roundness inequalities tend to be corrected by surface tension forces prior to cooling and hardening of the molten jets in the form of glass fibers. Thus, as in the case of the production of glass wool fibers, it has not been possible to produce substantially non-circular continuous fibers using shaped orifices provided in a die.

 There has long been a need to produce fibers, both in the rotary process and in the continuous fiber process, which have substantially non-circular sections. With respect to the reinforcement of resin matrices, these non-circular fibers would be very useful for imparting considerably greater transverse strength and better shear strength. Use of non-circular fibers as insulators would be advantageous in that an increase in surface area per unit volume of glass would decrease the thermal conductivity of the insulation made from these fibers.

 A measure of the non-circularity of mineral fibers is the "modular ratio", which is defined as the ratio of the diameter of the smallest circle in which the fiber section fits over the diameter of the largest circle that can accommodate inside the fiber section. In this context, fibers having a modular ratio of less than 1.2 are called circular fibers; fibers having a modular ratio greater than or equal to 1.2 are called non-circular fibers.

An attempt to manufacture non-circular glass fibers has been made by Warthen, as described in British Patent No. 3,063,094. Warthen's method uses a mechanical disturbance of the glass jet while it is still in a plastic, deformable state. Warthen teaches that to create a non-circular fiber, the
Glass jet, which is initially in a conical shape of circular section, must be deformed at a zone in which the viscosity of the jet is sufficiently high to cool or solidify rapidly during a refinement of the jets in the form of a continuous fiber, so that a similar deformation of the sectional configuration is maintained at the solidified refined fiber. Warthen also teaches that a heat sink must be applied to the glass jet by direct contact. This increases the viscosity of the molten glass to better preserve and perpetuate the non-circular section character of the mechanically disturbed molten glass jet.

 In the art of organic fiber production, it is common practice to use cooling methods to solidify molten streams of organic material in the form of non-circular sections similar to non-circular orifice shapes. However, these methods are practicable under conditions that differ considerably from the conditions associated with forming mineral fibers.

The production of non-circular organic fibers can be facilitated by a pressurization of dies, while a pressurization of dies containing molten glass poses serious operational problems.

The melting points of glass and organic compositions differ by 15000F (8150C) or more. The inorganic substance of the present invention has a liquidus temperature of greater than about 1000 ° F (64 ° C), while organic compositions are flatting and decomposing at much lower temperatures.

A clear picture of the differences in physical characteristics can be obtained by comparing the surface viscosity ratio of the glass with the marl ratio relative to an organic cheese-cr substance. The viscosity / surface tension (poise / ynes / cm) ratio of polymers is in the range of approximately 25 to 5000. The ratio for glass is in the range of approximately 0.1 to 25, preferably the range from approximately 0.25 to 15, and more preferably in the range of approximately 0.4 to 10. The viscosity of the molten glass at fiber forming temperatures is typically about 300 poises, whereas the viscosity of the organic melt is typically in the range of about 1000 to 3000 poises. Similarly, the surface tension forces of the glass (of the order of about 250 to 300 dynes / cm) are of an order of magnitude greater than those of the organic substance (about 30 dyneslcm). The lower viscosity and the higher tension of the glass make it less than 10Q

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In the past, there has never been a commercially successful process or apparatus for achieving the goal of making non-circular fibers from non-circular orifices.

 It has now been discovered that it is possible to produce inorganic fibers, such as glass fibers, having non-circular sections, by expelling jets of a molten mineral substance from non-circular orifices and by forcing cooling them. jets quickly enough to cure them as non-circular mineral fibers. This forced cooling of the jets hardens them in the form of fibers of non-circular sections before surface tension forces can force them to take circular sections. The aspect of the rapid cooling of the present invention makes it possible to produce mineral fibers having modular ratios higher than those practically achievable with the methods of the prior art. The present invention can be used both in the rotary process and in a continuous fiber process.

 Although the preferred means for rapidly cooling the jets is a relatively cold gas stream (eg, at room temperature), such as air, directed to come into contact with the jets, any suitable means for rapidly cooling Jets, such as fluid stream, water spray, liquid bath, ultrasonic or fin screens, can be used. Jets with higher modular ratios will generally have larger surface areas (ie ie greater perimeter of the jet section) and, therefore, higher heat transfer characteristics (and cooling rates) than those with smaller modular ratios When a cooling gas is used, the temperature and speed of the cooling gas flow also affect the cooling rate, as well as the speed of the jets and the time required for their passage through the flow of cooling gas as well as the distance traveled before the jets hardened in the form of fibers.

 The mineral fiber forming process of the present invention can be influenced by many variables, including inertial forces (hydrostatic pressure or pressurization in a textile process, hydrostatic pressure forces in a rotary process), mass forces in a rotary process, the initial temperature and viscosity of the mineral substance, the thickness or depth of the non-circular orifice, the surface tension characteristics of the molten mineral substance, the speed of jet movement, and the cooling rate of the jets.

 Pressurization of the molten glass mass, or the inertial force exerted on the glass coming out of the rotary spinning machine, or the mechanical tensile force in a continuous fiber process, can influence the final modular fiber ratio mineral. Insofar as surface tension forces begin to act to return the jets of circular sections before they reach the cooling gas stream, whose source may be positioned at a distance below the non-cooling orifices. circular, the time required for jets to reach the cooling gas flow zone may be critical.

 According to the present invention, there is provided a method for making non-circular mineral fibers comprising expelling non-circular orifices a molten mineral substance to produce jets of non-circular section, and cooling the jets to harden them in the form of fibers having a configuration of non-circular section similar to the configuration of the orifices, before they can take a circular section. Several of these orifices may be positioned in a wall of a container for containing a mass of molten mineral substance. The container may be, for example, a rotary spinning machine or a feeding apparatus.

 According to one aspect of the invention, the cooling of the mineral substance is effected by directing a cooling fluid to bring it into contact with the glass jet in a proportion and at a location sufficient to prevent the substance from taking a circular section. .

 According to the present invention, there is also provided an apparatus for making non-circular mineral fibers, having an orifice die for expelling one or more streams of molten mineral substance, the orifices having a modular ratio greater than about 1.2, and means for cooling the jets to form mineral fibers having a non-circular section configuration similar to the configuration of the orifices. Preferably, the orifices have a modular ratio in the range of approximately 1.2 to 50, more preferably in the range of approximately 1.3 to 25, and even more preferably in the range of approximately 1.7 to 10. The orifices may be trilobed, the three lobes being, in general, angularly spaced from one another, in a uniform manner.

The present invention will now be described by way of non-limiting example with reference to the accompanying drawings in which:
Figure 1 is a schematic elevational view of an apparatus for forming continuous non-circular glass fibers from a die in accordance with the principles of the present invention;
Figure 2 is an upward plan view of a die bottom plate having 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 characteristics as a function of distance from the die;
Figure 5 is a schematic elevational view of a non-circular orifice according to the principles of the present invention; ;
Figures 6 to 9 illustrate non-circular sections of glass fibers made under different cooling conditions;
Figure 10 is a sectional view, on an enlarged scale, of the trilobal fiberglass of Figure 9;
Fig. 11 is a graph showing the relationship between the modular ratio and the cooling rate;
Figure 12 is an isometric perspective view of a resin matrix reinforced with non-circular fibers;
Fig. 13 is an isometric view in perspective and on an enlarged scale of three of the trilobal fibers of Fig. 12;
Figure 14 is an upward plan view of a lower die wall having both circular and non-circular orifices;
Figure 15 is a schematic sectional and elevational view of the invention applied to a rotary process;
Figure 16 is a schematic elevational view of the rotary spinning machine of Figure 15;
Figure 17 is an enlarged sectional view of a crescent-shaped fiber produced in the apparatus of Figures 15 and 16;
Figure 18 is a plan view of an embodiment of a non-circular nozzle orifice.

 The present invention will be described in connection with a method and apparatus for forming glass fibers, and products made therefrom, although it is understood that the process is suitable for fibers made from other mineral substances , in particular mineral substances such as rock, slag and basalt.

 As shown in FIG. 1, jets of molten glass 10 are expelled from a bottom wall of orifice dies 12 of a feed apparatus or a die 14, and are drawn in the form of fibers 16 by n Any suitable means, such as the mechanical action of a coiler 18. A collector pad 20 and a sizing applicator 22 may be used in the manner known in the art. The die contains a mass of molten glass 24 from which the molten glass jets are drawn. As illustrated, air injectors 26, which constitute means for cooling the molten glass jets, are positioned to direct air so that it comes into contact with the melted jets at the moment when they are The stream of air cools the molten streams sufficiently rapidly in the form of glass fibers so that they retain the generally non-circular configuration of the molten streams. Other suitable cooling fluids, such as carbon dioxide, nitrogen, steam or water, may be used to forcibly cool the jets.

 As shown in Figures 2 and 3, the lower die wall has trilobal orifices 28 provided with lobes positioned uniformly about their periphery. The orifices and the resulting fibers may be of various shapes, such as, for example, cruciform, star-shaped, five-lobed, eight-lobed, or rectangular.

 To describe quantitatively the formation of non-circular glass fibers, it is useful to consider a time constant r for the deterioration of the configuration of a non-circular section into a circular section. As soon as a stream of molten glass of non-circular section emerges from a non-circular orifice, surface tension forces act on it to transform its section into a circular section. In opposition to these forces, viscous forces tend to resist changes in jet shape. The viscous forces increase extremely rapidly due to cooling occurring as the molten glass of the jet moves away from the orifice. To succeed in making noncircular fibers, the viscous forces must be increased sufficiently rapidly ( that is, viscosity) to retard the effect of surface tension forces.

 It is thought that the time constant is a function of the viscosity of the glass, the equivalent radius of the glass jet, and the surface tension, according to the equation: q7 = J; Lrl6. This equation can be transformed using a velocity factor to allow integration over a distance along the fiber, i.e., a vertical distance down from the orifice, and not by compared to time.

In operation, when only a few time constants pass before the viscosity of the glass is hardened or substantially increased, the fiber still retains its non-circular shape. But, when many time constants flow, before reaching a high viscosity, the Glass Spray finds a circular section and produces a circular fiber. When we integrate the inverse of the time constant over the distance up to a 100% attenuation, we get the ratio of time-to-become-viscous over time-to-find-a-circular-section This ratio, difficult to measure exactly, can be evaluated thanks to the Z ratio given by the following equation: ZU 0 / (x 75 oo reo) * (1 / seen) * 1 / (MRo-1) in which:
X75 is the distance from the die with attenuation of 75 percent (cm);
is the initial viscosity (poise);
r is the initial equivalent fiber radius (cm);
eo
is is the initial surface tension of the substance
mineral (dynes / cm);
vO is the initial velocity (cm / sec) of passage in the ori
profits; and
MR is the initial modular ratio of said jets.

o
Factor 1 / (MR -1) is a factor indicative of the ratio
o Modular orifice, and, therefore, the initial modular ratio of the glass jet. It has been found that this equation is in perfect correlation with theoretical considerations illustrated in Figure 4, in which the curve represents the reciprocal of the time constant as a function of a distance from the die. The integral is the area under the curve, and the smaller the area under the curve, the smaller the number of time constants elapsed before curing the jet, and therefore the modular ratio is important. It has been observed that for the final fiber to be. non-circular, Z must be less than or equal to 2, and preferably less than or equal to 1.

Inertial forces or glass pressure at the ports can affect the limit to which non-circular fibers can be formed. The pressure may be generated by any means, such as the hydrostatic pressure of the molten glass, a gas pressurization of the feed apparatus, or a combination of both means. For the production of continuous glass fibers, the hydrostatic pressure is preferably in a range of from about 800 psig (2,800 Pascals) to about 100 psig (690,000 psig).
Pascals). More preferably, the molten mineral will be subjected to a hydrostatic pressure within the range of about 0.7 psig (4,800 Pascals) to about 5 psig (34,000).
Pascals).

 Although the die shown in FIGS. 1 to 3 has orifices without nozzles, the invention may be realized with nozzle orifices as well. The orifice of Figure 5 has a depth "t".

It has been found that lower or lower apertures make it possible to improve or increase the modular ratio of the non-circular fibers. The depth of the orifices is preferably in the range of approximately 0.001 inches. (0.025mm) to 0.250 in. (6.4mm).

 The mineral fibers produced according to the present invention will, in general, have equivalent diameters in the range of approximately 0.2x105 in. (0.05 microns) at 300x105 in.

(76 microns) although non-circular fibers exceeding the limits of this range are achievable. Preferably, the mineral fibers are in the range of filaments B to Y, i.e., in the range of approximately 10x10-5 in. (2.5 microns) at 120x10-5 in. (30 microns). More preferably, the mineral fibers of the present invention are G to T filaments in the range of approximately 35x165in. (8.9 microns) at 95x10-5in. (24 microns).

 Figures 6 to 9 illustrate sections of four non-circular fibers produced from an apparatus similar to that shown in Figures 1 to 3. These fiber sections are all of a shape similar to that of the trilobal orifice. The apparatus was monitored under substantially constant operating conditions, except for coolant velocities. Speeds were different for each fiber. It is believed that the rate at which the molten glass jet is cooled is a function of the coolant speed, when all other conditions are the same. A fiber 16a of Figure 6 has been produced with a cooling air velocity at the die orifice of about 10 meters per second, and has a modular ratio of about 1.35. A non-circular fiber 16b shown in Figure 7 has been produced with a cooling rate of about 15 meters per second, and has a modular ratio of about 1.45. A fiber 16c shown in Figure 8, having a modular ratio of about 1.75, was produced with a cooling rate of about 20 meters per second. A non-circular fiber 16d shown in Figure 9, having a modular ratio of about 2.70, was produced with a cooling rate of about 30 meters per second. Although cooling rates of up to 60 meters per second, or more, can be used in conjunction with the invention, it has been found that the preferred cooling rate of air at ambient temperature (approximately 800F, 270C ) is less than about 40 meters per second. More preferably, the cooling rate is in the range of approximately 5 to 30 meters per second. These cooling rates contrast with those used in normal air-cooled dies used to prevent flooding, for which cooling rates at the die nozzles are in the range of about 2 to 4 meters per second.

As shown in FIG. 10, the dimensions of the non-circular fiber 16d can be characterized using the modular ratio, which corresponds to the external diameter Do divided by the internal diameter Di
The outer diameter is the smallest circle in which the entire section can be placed. The inner diameter is the largest circle that can be placed inside the fiber section.

 As shown in Figure 11, the modular ratio increases with the cooling rate. It can also be seen that when the die is pressurized, the modular ratio increases.

 In Figures 12 and 13, it is shown that continuous trilobal fibers 16d can be fabricated and positioned in a matrix, such as a plastic resin 32, for reinforcement. The mineral fibers of the present invention are useful for reinforcing any organic or mineral matrix suitable for use in combination with other types of reinforcement. For example, thermoplastic or thermoset resins, such as polyesters or epoxy resins, may be used. Cements, low-melting metals, and silicate matrices may also be reinforced. Dies reinforced with the non-core sidewires of the present invention may at the same time be reinforced by any other suitable reinforcement, such as mineral fibers or circular organic fibers.

 As shown in Figure 14, the lower die wall 12 may have both non-circular orifices 28 and circular orifices 34 to produce fiber jets, some of which have circular sections and others non-circular sections.

 As illustrated in Figure 18, a nozzle die can be used to produce non-circular fibers of the invention. The three branches 54 of the orifice have ends of flared limbs 56. The orifice is formed in the lower end of a tubular nozzle with closed end 58.

 When the invention is implemented using the rotary method, the "container" is a rotary spinning machine and not a feed apparatus or a die, and the non-circular orifices are positioned in the peripheral wall of the machine. rotating spinning instead of being positioned in the lower die wall.

 In FIG. 15, it can be seen that the rotary spinning machine 42 can be fed with molten glass 40. The molten glass collides with a lower wall 44 of the rotary spinning machine and flows outwards under the effect centrifugal force towards the peripheral wall 46 of the machine. The peripheral wall of the rotary spinning machine has non-circular orifices 48 through which molten glass jets 50 emerge. The relative displacement of the jets of glass that emanate from the machine and the air surrounding it cause cooling. Molten jets in the form of glass fibers 52. To a certain extent, the cooling rate can be controlled by the speed of rotation of the spinning machine. An annular blower, such as the blower 54, can be positioned concentrically around the spinning machine to fold the fibers downward for collection, which can be accomplished by conventional means.

 It is possible to equip the rotary spinning machine with non-circular orifices of various shapes, such as slots or crosses, and of different configurations. As illustrated in FIG. 16, the spinning spinning machine may be provided with crescent-shaped orifices to produce glass fibers 52 having the sectional configuration shown in FIG. 17.

EXAMPLE I
Continuous tri-lobed E-glass fibers having a modular relationship
The average of about 2.3 was made from a nozzleless die with 20 trilobal holes under the following conditions.

Trilobal orifice dimensions:
depth: 0.015in. (0.38 mm)
width of each branch: 0.009 in. (0.23 mm)
length of each branch
to the center of the orifice: 0.027 in. (0.69 mm)
Glass temperature: 21900F (12000C)
Glass type: 200E
Filtration pressure (total): 8.7 psig (60 KPa)
Glass flow rate: 0.034lb / hr / hole (0.26 g / min / orifice)
Number of filaments: 20
Orifice arrangement: 2 rows, 10 holes / row, arrangement
in a staggered arrangement,
space between rows: 0.125 in. (3.18 mm)
spacing of holes in a row:
0.120 in. (3.05 mm)
Coolant: air at 800F (270C)
Injector dimensions of cooling: hcrizcntal.1,5 in. (38.1 mm) x
vertical. 0.25 in. (6.35 mm)
Cooling injector position: 1 in. (25 mm) from the median axis of
the nozzle (median axis between two rows)
15 degree angle to the horizontal
Cooling injector flow: 300 scfh (10.2 kg / hr)
Cooling rate: 32 ft / s (9.8 m / s) at the level of
injector
29-32 ft / s (8.8-9.8 m / s) at the axis
median of the sector
(very slight deterioration in speed, the
optionally)
Winder speed: 1550 ft / min (7.87 m / s)
Medium fiber diameter: M filament, 65 HT (16.5microns) based
section area
EXAMPLES II & III
Continuous trilobal glass fibers E were made using a nozzle die with 14 holes using finned screen cooling. The nozzles were closed-ended tubular nozzles having orifices having the pattern shown in Figure 18, machined in the lower nozzle portion. The particular dimensions of the pattern used determined the modular ratios of final fibers. The following conditions were applied to all nozzles.

Nozzle tube diameter: 0; 130 in. (3.3 mm)
Nozzle tube length: 0.240 in. (6.1 mm)
Terminal Thickness (orifice depth): 0.011 in. (0,28mm)
Nozzle model: 2 rows, 7 nozzles / row, rectilinear model
space between rows - 0.030 in. (7.6 mm)
nozzle spacing on a row - 0.23 in. (5.8 mm)
Finned screen geometry: fin thickness - 0.055 in.

(1.4mm)
fin height - 0.625 in. (15.9 mm)
fin length - 1.68 in. (42.7 mm)
spacing of blades forming fins
0.23 in. (5.8 mm)
Glass type: 200E
Glass temperature: 22500F (12300C)
Die pressure (total): 1.1 psig (7.6 KPa)
Winder speed: approximately 750 ft / min (3.81 m / s)
This value varies somewhat during the experiments.

EXAMPLE II
Orifice dimensions: P - 0.025 in. (0.64 mm)
R-0.020 in. (0.51 mm)
L - 0.010 in. (0.25 mm)
Glass flow rate: 0.018 lb / hr / hole (0.14 gm / min / orifice)
Medium fiber diameter: N filament, 70 HT (17.8 microns)
Average Modular Report: 2.2
EXAMPLE III
Orifice dimensions: P - 0.025 in. (0.64 mm)
R-0.020 in. (0.51 mm)
L - 0.005 in. (0.13 mm)
Glass flow rate: 0.014 lb / hr / hole (0.106 gm / min / orifice)
Medium fiber diameter: filament L, 59 HT (14.9 microns)
Average modular ratio: 5.3
It is evident from the foregoing description that various modifications can be made to the present invention without departing from the scope of the invention.

 It will be seen that this invention is useful for the production of glass fibers for use as thermal and acoustic insulation products, and as reinforcements for resin matrices.

Claims (12)

 Process for producing non-circular mineral fibers (16, 52) having a modular ratio greater than about 1.2, characterized in that it expels non-circular orifices (28, 48) a molten mineral substance ( 24, 40) whose liquidus is greater than about 12000F (6490 C) to produce molten jets of non-circular section (10, 50), said non-circular orifices being positioned in a wall (12, 46) of a container ( 14, 42) for containing a mass of molten mineral substance and the mineral substance of said jets having a low initial viscosity so that said jets would take circular sections in the absence of cooling, and to cool said jets to harden them. in the form of mineral fibers (16, 52) having a configuration of non-circular section similar to the configuration of said orifices before the jets (10, 50) can take circular sections.  2. Method according to claim 1, characterized in that the ratio of the viscosity (poise) to the surface tension (dynes / cm) is in the range of approximately 0.1 to 25.  The method of claim 1, characterized in that said non-circular orifices (28) are positioned in a die wall (12) of a feed apparatus (14) to form continuous glass fibers (16).  4. Method according to claim 1, characterized in that said non-circular orifices (48) are positioned in the peripheral wall (46) of a rotary spinning machine (42) for centrifuging mineral fibers.  Process according to claim 3, characterized in that the molten mineral substance (24) contained in said die (14) has a pressure in the range of approximately 0.4 psig at the ports (28) ( 2,800 Pascals) at 100 psig (690,000 Pascals).  6. Method according to claim 3, characterized in that it consists in cooling said jets (10) by directing a cooling fluid to bring it into contact therewith.  7. Method according to claim 6, characterized in that it consists in cooling said jets (10) using finned screens.  8. Process according to claim 3, characterized in that said cooling step is sufficient to satisfy the equation: Z 4 2 in which:  and in OreO) o and in which:  X75 is the distance from the die with an attenu  (cm) 75 percent;  is the initial viscosity (poise);  r is the initial equivalent fiber radius (cm); is is the initial surface tension of the substance  mineral (dynes / cm);  vO is the initial velocity (cm / sec) of passage in said  ports; and  MRo is the initial modular ratio of said jets.  Apparatus for producing non-circular mineral fibers (16) having a modular ratio greater than about 1.2, characterized in that it comprises an orifice die wall (12) for expelling one or more jets (10) from a molten mineral substance (24) whose liquidus is greater than about 12000F (6490C), said orifice die wall being positioned in a container (14) for containing a mass of molten mineral substance and the mineral substance of said jets having a low initial viscosity such that said jets would take circular sections in the absence of cooling, the orifices (28) having a modular ratio in the range of approximately 1.3 to 25, and means (26) for cooling said jets to form mineral fibers having a non-circular section configuration similar to the configuration of said orifices.  Apparatus according to claim 9, characterized in that said die wall (12) is positioned in a feed apparatus (14) to form continuous glass fibers (16).  Apparatus according to claim 9, characterized in that said orifice die wall (12) corresponds to the peripheral wall (46) of a spinning spinning machine (42) for centrifuging mineral fibers (52).  12. Apparatus according to claim 10, characterized in that said cooling means (54) comprise finned screens.