SI8310794A8 - Improvements in fibre formation techniques comprising centrifugation - Google Patents

Description

ISOVER SAINT-GOBAIN

The process of forming fibers from thermoplastic material

It is a technical field of the invention

The invention relates to the manufacture or treatment of parts of fibers or filaments obtained from glass, minerals or softened slag. The expected classification of the subject by MCC is C 03B 37/04.

The present invention relates to a process for forming fibers of thermoplastic material comprising a centrifugation operation.

More specifically, the invention relates to techniques whereby a material (© intended for processing is introduced in a stretchable state into a centrifugal assembly having a larger number of mouths at the circumferential circumference. Under the effect of centrifugal force, the stretchable material passes through these mouths to form either threads or nails. The circumferential wall of the centrifugal assembly is encircled by a high-temperature gas annular gas stream, neither being ejected into this gas stream.This gas flow is neither complete nor formed, nor formed by the gas itself.

- 2 Technical problem

There was a need to find a new, technologically advanced process for forming fibers of thermoplastic material, comprising a high circumferential centrifugation operation that produces very fine and regular fibers with very good insulation and mechanical quality, with desirable production capacity and rational energy consumption.

The state of the art

According to these known techniques, strands are formed by gas transport to a receiving body, which is typically shaped as a gas-permeable conveyor belt. The fibers are lodged in the form of a web or carpet on a conveyor belt.

However, where the final product must have some cohesion, the fibers are coated with a binder to be added to the fibers as they travel towards the conveyor belt. The lining of the coated fibers passes into a heat treatment casing to provide binder polymerization. It is then cut and conditioned according to the shape of the finished product.

These fiber forming techniques, which result in the spinning and the stretching effect of hot gas flow on the one hand, are of particular interest. In particular, they make it possible, in particular, to achieve, in economically satisfactory circumstances, insulation products which have the most satisfactory quality at a reasonable price. The mouthpiece system, which feeds the primary threads of the molten material, a thermoplastic material, ensures to some extent good uniformity in the formation of the primary fibers. The formation of uniform primary fibers is a prerequisite for achieving finely drawn finite fibers. Otherwise, the hot gas drafting allows a relatively significant amount of material to pass through each orifice. As a result, the production capacity of each centrifugal assembly is increased, thus reducing unit costs.

These very schematic reasons are certainly insufficient to report the benefits of this type of process. However, they allow us to emphasize how the type procedures of the invention differ from the processes that are apparently related to them and which, however, are very different in their function and in their results.

- 3 E.g. state that techniques are known by which spin is only centrifugal. According to these techniques, the annular gas flow around the centrifugal assembly is either absent or not involved in the pulling of the fibers. An assumed advantage of these techniques is the saving on energy consumption corresponding to the creation of high-temperature and high-speed draft gas. The savings realized in this way, however, are reflected in the significantly smaller production capacity of the centrifugal assembly and the global production costs are not reduced.

It is necessary to recall that the production of fibers, and therefore the production of products prepared with these fibers, is not only subject to quality requirements but also to production costs. These requirements cover many aspects, as we will see later in the course of the description. Quality is first the insulating properties of the products, but the mechanical properties also play a very important role. Cost differences are even greater and investment, labor, raw materials, energy must be taken into account ...

The state of the art teaches ways to produce fibers and insulation products that are of better quality than those typically obtained by more conventional techniques. However, this instruction corresponds to designs that are relatively unfavorable in terms of production costs, because either production is weak, energy consumption is too high, or expensive fibrous compositions have to be used ...

The improvements that have been proposed so far for the type of process to which the present invention relates are extremely different, even when we confine ourselves to devices that relate only to the fiber formation phase and therefore exclude anything that relates to later treatments to which the fibers are subjected to the final product.

Recent publications on the subject include French patent application no. 2 443 436 which belongs to the applicant and contains a number of proposals. They are focused in particular on the nature of the fibrous material, with the purpose of the assembly of devices being to better control the temperature and travel of the material in the centrifuger, the specific structures of the centrifuger itself, etc. ...

- 4 Other previous posts such as. French patent no. 1 382 917, which also belongs to the applicant, relates to the improvement of the dumping conditions of primary fibers in traction gas.

These two examples represent only a small part of the literature that is very rich about this subject. However, they show what the difference may be in the proposals offered to improve this type of procedure.

Although in all cases the purpose of improving fiber quality and the cost of production is perfectly clear, this does not apply to the technical means used to achieve it.

The disadvantages of the solutions known so far are that they do not provide fibers that are sufficiently high insulating and mechanical in quality, and in addition the known processes do not reach the desired production capacity or use too much energy.

In view of the shortcomings of the procedures known so far (Fr.pat.

443 436), which are carried out at a peripheral speed not exceeding 38 m / s and which give fibers of insufficiently high insulating and mechanical quality, nor of sufficient production capacity, the further disadvantage of which are that they are suitable only for certain baselines materials - a technical problem is posed before the inventor, with what and what process parameters can be achieved the desired insulation and mechanical quality of the fibers and the desired increased production capacity.

Description of solution to a technical problem with implementation examples

To solve the above technical problem, we therefore propose a new process for forming fibers of thermoplastic material, such as glass, in which the material is in a stretchable state - such as a viscosity of 100 Pa.s and a temperature of 1030 to 116O ° C - to a centrifugal assembly which has its own a perimeter provided with mouths, the material being discharged through these mouths outside the centrifuge assembly in the form of filaments which are removably taken and drawn by a high temperature gas jet directed along the perimeter of the centrifugal assembly transversely to the threading direction, that the flow of material to the mouth is in the range of 0.1 to 3 kg / day, the circumferential speed of the centrifuge assembly at the mouth level from which the threads protrude is between 50 and 150 m / s, to centrifuge from 800 to 8000 rpm to gas. high temperature flow occurs at a pressure of 1000 to 10,000 Pa and the width of the emission nozzle, as max. 20 mm, and that is

- 5 flow of fibrous material resulting from a centrifugal assembly greater than 12 tonnes of material per day.

On the basis of extensive research and testing according to the invention, it is found that the solution of the technical problem so far solved above is in the relevant parameter of the circumferential velocity of the centrifugal assembly, which must be substantially higher than the only permissible circumferential velocity of 38 m / sec so far and which according to the invention is from 50 to 90 m / s, wherein according to the selected circumferential velocity parameter according to the invention, further parameters of the process according to the invention are causally related, namely, the parameter of the maximum daily amount per mouth of the centrifuge assembly, which is 3 kg / day, preferably 0 , 7 to 1.4 kg / day, where the parameter of the total quantity in terms of the process for all mouths is more than 17 tonnes / day up to 20 oz. 25 tonnes / day, the traction gas pressure parameter for fibers is 1000 to 10,000 Pa, preferably 2000 to 6000 Pa, and the velocity parameter from the gas emitter of the outgoing traction gas is greater than 100 m / sec, with a centrifugal traction of molten material being approx. 100 Pa.s and the temperature according to the selected material quality is below 116O ° C and the minimum temperature of the molten material is 1030 ° C, thus reducing the load on the centrifuge assembly.

In view of the technical problem discussed above, the process according to the invention provides a new process for forming mineral fibers, in particular an increase in production capacity at a constant quality of production fibers. The solution according to the invention is that it provides new conditions for centrifugal treatment to achieve the above results.

The solution according to the invention is also to lead to insulation products prepared according to new proposals and with suitable insulating and mechanical properties, without the production price being inaccessible.

The inventors have shown through the conducted research that it is possible to achieve these goals and other results, which will be presented in the following description, by choosing a process for forming fibers under well-defined spin conditions.

In general, centrifugation according to the invention should be carried out such that the peripheral velocity, i.e. the velocity of movement of the mouths positioned at the circumference of the centrifugal assembly is relatively high.

The reasons why it is possible to improve the quality of prepared products when operating at high peripheral speeds are not yet fully understood. To some extent, this result is quite surprising. It is known that the pulling of the fibers of the material arising from the mouths located at the periphery of the centrifugal assembly is a complex phenomenon involving the movement of the centrifugal assembly and the movement of the gas stream · which pulls the fibers with them. The consequence of the simultaneity of both these phenomena is that it is not possible to determine with certainty the role of each of them in the traction mechanism and in the effects they produce.

However, if we want to analyze the phenomenon, we can reasonably say that we get a fiber because it can be compared to mechanical drawing, with the thread being maintained at one end by centrifugal torque and at the other end by friction by the surrounding air. In this hypothesis, the relative motion of both ends of the fiber is due to the composition of the rotational motion of the centrifugal assembly and the movement of the gas streams.

The direction followed by niΐί when exiting the centrifugal assembly clearly indicates that such a composition of movements effectively mediates traction. The projection of the thread path in a plane tangential to the centrifugal assembly and the armor is determined as the gas flow direction (usually parallel to the axis of the centrifugal assembly), and we find that this angle is in fact a function of the relationship between the circumferential velocity of the centrifugal assembly and the gas velocity.

Under normal operating conditions, it is relatively small, since the gas velocity is much higher than the circumferential velocity of the centrifuge assembly. This hi tended to emphasize the predominant part of gas flow compression in the fiber traction mechanism.

In the above we only considered the projection of pom. The experiments also show that the threads are slightly offset from the perimeter wall, so the comments we made about dumping also apply to the true path of the fiber.

Following these comments, considerations of a purely geometric nature, which will be analyzed in more detail later, would necessarily lead to the conclusion that increasing the gas velocity is the best solution to improve fiber traction.

In reality, however, we find that under the remaining unchanged conditions, with a significant increase in gas velocity, s. which we strive to get extremely fine fibers from, we get products whose properties are much less good, these fibers are especially very uneven, brittle and short, and the insulating mats made with these fibers show poor mechanical properties and even worse thermal properties, although in slightly smaller.

At the surprise j iv. In this way, the inventors have found that a very significant improvement in the quality of insulation products is achieved when they increase the circumferential velocity under unchanged other conditions.

If it is desirable to have a high circumferential velocity, it is inherently understandable that for technological reasons this velocity cannot be infinitely increased. In practice, it is difficult to exceed speeds of the order of n / s and most often the speed 'in the invention is between 5θ and 90

The circumferential velocity is limited especially with regard to the mechanical strength of the centrifugal assemblies used. Although the occasional replacement of the centrifugal assembly is inevitable, its operating life under the invention will have to remain compatible with the conditions of technical certainty and also the prices which are an integral part of any industrial exploitation must remain within reasonable limits.

Replacement of the centrifugal assembly under conventional operating conditions is usually required after several hundred hours of operation. It is important that the lifespan of the inventive inventions should not be shorter than that of the prior art and, in the present case, be substantially longer.

Limiting the rotational speed - and thus limiting the loads carried by the centrifugal assembly - that would not interfere with predefined conditions, therefore, seems particularly desirable for carrying out the invention. Given the commonly used materials, it seems appropriate not to exceed the 8000rpm limit.

If the rotational speed is limited so that the centrifugal assembly is not subjected to excessive stress, it is necessary that the centrifugal effect remains sufficient to allow the material to be transferred to the fibers to be thrown from the mouth of the centrifugal assembly under satisfactory conditions, in particular flow. Thus, it is preferred that the rotational speed is not less than 800 rpm.

In the practical choice of rotational speed and circumferential speed, the questions posed by the limit resistance of dispatch usually mean that the maximum circumferential speeds are related to the lowest rotational speeds and vice versa. This mode of operation does not necessarily represent optimization in the field of product formation, but a compromise to ensure a sufficiently long device life.

The amount of material coming through each mouthpiece of the centrifuge assembly is a very important factor in this type of process. Of course, this quantity directly determines the global production capacity of the centrifugal assembly. More indirectly, this quantity at the mouth is also an element that significantly affects the properties of the fibers produced.

It is easy to understand that the greater the amount falling on each mouth, the more intense it must be to pull in to achieve the constant fineness of the fibers.

Considering the practical needs of production, the volume per mouthpiece should not be too small. For glass-based material or a similar analogue, we can consider the lower limit to be 0.1 kg / day, below which it is no longer economical to operate.

In contrast, too much does not allow very fine fibers to be reached. However, for the qualities required of insulating material, the quantity of material is preferably not greater than; 3 kg / day.

Conveniently, trade-offs between production capacity and fiber quality lead to volume regulation at the mouth at between 0.7 and 1.4 kg / day.

Under the conditions of the invention, the production capacity of the centrifuging body can reach very significant values without reducing the quality of the fibers or the quality of the finished product. It goes without saying that it is also possible to maintain production at a lower level, especially to further improve quality.

- ΊΟ

The advantages of the invention from this point of view are very clear.

Increasing production is an economically important factor and of particular importance. In the state of the art, he was the subject of many suggestions; increasing the number of mouths of the centrifugal assembly, increasing the cross-section of these mouths, increasing the fluidity of the material… .These various elements allow for an effective modification of the amount of material passing through the centrifugal assembly, but the downside of such proposals is a decrease in quality or problems relating to the living the lazy age of the device. Thus, increasing the density of the mouth at the circumference of the centrifugal assembly, i.e. the number of mouths per unit of surface not only weakens the centrifugal assembly but, when exceeding a certain threshold, proves to be unfavorable to the fiber quality. It can be assumed that the primary fibers, which are initially too compressed, are entwined and stuck together before their drawing is complete. This may explain why the fibers obtained under these conditions are less uniform, less fine and shorter.

We face a similar problem when - still with the intention of increasing production capacity - the mouth section is increased to maintain the same viscosity conditions of the fibrous material. In this case, the primary fibers are thicker and satisfactory traction is difficult to achieve, even if we modify the ring gas regime to pull the fibers.

Increase in fluidity for a given material, i.e. increasing its temperature, however, poses different problems. Operating temperatures are usually located at the limit of what the alloy of the centrifugal assembly can withstand. Often, they even choose the nature of the fiber translation composition to follow this type of restriction. Increasing the temperature according to this hypothesis is impossible unless we use valuable materials for the construction of a centrifugal assembly, which in turn causes other problems, namely the cost and mechanical properties.

Fluid enhancement can also be achieved by using materials whose composition is determined to lead to this result. However, the disadvantage of these compositions is that they are significantly more expensive.

Conversely, in older literature, processes aimed at improving quality lead to a decrease in production.

Thanks to the invention, the result is found to be at a much better level, despite maintaining the contrast between quality and quantity. Even when we set ourselves the goal of producing good quality (below we will see how we evaluate it), comparable to the one obtained so far with this type of process, we can easily exceed the production of about 12 tonnes of fibrous material daily and after centrifugal assembly.

In practice, it is considered appropriate to maintain production at the level above 17 t per day according to the invention and can also achieve production of 20 to 25 t or more, while maintaining the product with excellent quality.

It is worth mentioning that we can achieve these results without using the previously indicated modifications. It is not necessary to change the density of the mouths or their dimensions, etc.

Creator primary fibers are therefore fully comparable to those obtained by conventional analogue techniques and, due to improved traction, as previously stated, product quality is also better.

The drawing of the fibers by means of gas streams is effected by means of a generator whose annular orifice is positioned in the immediate vicinity of the centrifuge assembly. The gas stream has a certain width to keep the threads completely immersed in the gas stream from the centrifuge assembly, keeping them in conditions suitable for drawing them.

The width of the current, of course, depends on the exact geometric configuration of the fiber fabrication device. For a given preparation, the useful variations are relatively limited, considering that in order to reduce energy consumption, we make every effort to reduce the width of the gas stream as much as possible.

For conventional preparations, the width of the gas stream at the beginning of the order is 0.3 to 2 cm.

The leakage gas pressure under these conditions ranges from values that can vary from 1000 Pa to 10,000 Pa for a flow width of less than 2 cm and preferably from 2000 to 6000 Pa for a flow width of less than 1.5 cm.

In analyzing what happens before the effects related to circumferential gyration, material flow rate and traction gas pressure, we have repeatedly been led to determine that, in practice, these different parameters mediate together in the quality or price of the products obtained. .

Among these different parameters we can determine the relationships without. _{: of} exact physical importance, in order to take into account the most favorable operating conditions proposed by the invention.

however, regardless of these operating parameters, it is important for these formulas to have a criterion expressing the quality of the product obtained. In this way, these terms clearly distinguish the conditions for carrying out the process of the invention from those of the prior art.

Thus, according to the invention, the circumferential velocity at the mouth of the centrifuge assembly, expressed in m / sec, is selected, the mass of material passing through each mouth of the centrifuge assembly, expressed in kg per mouth and per day, and the emission pressure £ of the traction gas, expressed in Pa for the length emissions of a minimum of 5 mm and a maximum of 12 mm, such that the qv / p ratio is in the range of 0.007 to 0.05 and preferably between 0.0075 and 0.02. i

It is convenient to give a good account of the particularities of the invention in order to introduce the parameters which affect the fineness of the fibers. However, fineness is not the only criterion for product labeling, as we will see below. We chose it because it is without a doubt the most accessible and significant parameter for the quality of traction achieved.

Fiber fineness is conventionally determined indirectly by so-called. micron number (F).

The micron number is measured as follows. A sample of the product, usually 5 g, is placed in the compartment through which the gas flow is transmitted, which is emitted under specified conditions, in particular pressure. The pattern the gas passes through is an obstacle that tends to inhibit the passage of that gas. The measured gas flow is read on a scale gauge with a scale. These are defined values for the normalized conditions that are read.

The finer the fibers for the same sample mass, the better the flow rate.

The most common micron numbers for insulation products are between 2 and 6 for 5 g. Products with a micron number less than or equal to 3 by 5 g are considered very fine. In general, they are given better insulation capacity per unit mass of product.

According to the invention, the ratio q.v / p.F is better than 0.0035, with p, v, p and F (for 5 g) being expressed in the units mentioned above. Preferably, this ratio is above'0.0040.

When operating under certain pressure conditions, the invention can be expressed by a simplified ratio q.v / F. This ratio is advantageous in the invention over 17 and preferably over 18.

In the foregoing formulas, the q / F ratio expresses in a certain way the advantages of the process of the invention. It is all the greater when we get the product in bulk and with a finer structure. The parameters v and p, however, can be approximated by the method of drawing the fibers. However, the formulas used as stated above have only the function of allowing a good characterization of the invention in the cases by known techniques.

An advantage of the type process of the invention is that it can be used to form fibers originating from the Syrian material field. Of particular useful materials are particularly preferred glass compositions defined as follows:

- 15 - Si0 ₂ 61 - .'66 - At ₂ 0 12.55-16.5

- A1 ₂ O ₃ 2.5-5 - K ₂ 0 O - 5

- CaO 6-9 - O - 7.5

- MgO O - 5 - ^ θ2θ3 under. θ * θ

The values indicated above are expressed as a percentage by mass of each of the compositions. However, the exact composition can also include traces of different elements.

• Other conditions are also involved in carrying out the process of the invention. They refer in particular to the material (temperature) and the gas flow for drawing (temperature). These conditions, however, do not differ significantly from the corresponding conditions described in the prior art. Therefore, we do not consider it necessary to re-examine them here.

Other advantages and features of the invention will appear in the following description and in the embodiments. However, their purpose is merely to explain the invention in a more detailed manner and they have no restrictive character:

The continuation of the description relates in particular to the type of device used in which the fiber forming process of the invention can be carried out. We refer to the drawings in which:

- Figure 1 is a perspective view of the centrifuge assembly and the path of the formed fiber at the circumference of the centrifuge assembly,

- Figure 2 shows a projection of the fiber path from FIG. 1 in the plane passing in terms of tangent to the centrifuge assembly,

- Fig. 3 is a cross-sectional view of a fiber assembly assembly of the invention,

- Fig. 4 is an enlarged scale detail of Fig. 3 showing various elements operating in the area where the fiber is pulled.

- 16 The purpose of Figures 1 and 2 is to show us the effects of spinning and gas flow on fiber drawing.

Figure 1 shows in a schematic manner a centrifugal assembly on which the peripheral walls are arranged mouths. The path of fiber F is also shown in this drawing as well as the tangential plane T to the wall of the centrifuge assembly at the level of the outlet of fiber F.

The direction of rotation of the centrifuge assembly is indicated by an arrow.

although schematic, the fiber path in this drawing is at the heart of the characteristics we have actually observed.

Thus, we find that the material moves away from the wall of the centrifugal assembly, but after a very short distance the path is obstructed by the hot gas flow that surrounds the wall.

Thereafter, the development of the fiber follows approximately the direction corresponding to the composition of the velocity of the centrifugal assembly and the gas flow.

On the plane tangential to the centrifugal assembly, the projection of this composition of the type shown in Figure 2, 0 is the estuary and the angle formed by the projection with the direction of gas advance is shown by the OG vector.

As with conventional spin velocity conditions (represented by the vector OB) and gas velocities of the order of 20 ° or less.

Thus, it is understood that even a relatively significant increase in the velocity of the centrifuge assembly (as shown by the Dashed Line) could not significantly modify the drag of the fibers. The intensity of this drag can be represented by the sum of the vectors OG and OP. Increasing the OP, however, only causes a slight variation in the sum, because it is small. On the contrary, it seems that it would be more convenient to increase the gas velocity to improve traction. In the examples of the invention, however, we see that the opposite is true and that for better drawn fibers of better quality, it is preferable to increase the circumferential speed of the centrifuge assembly. and '

Now let's take a closer look at the composition of the fiber forming assembly.

The fiber forming apparatus shown in FIG. 5, comprises a centrifugal assembly in the narrow sense of the word, which is fully denoted by reference 1. This centrifugal assembly, which is mounted horizontally, bears the assembly 4 which forms the shaft of the device. This shaft is housed in the bearing housing 5- The shaft assembly 4 and the centrifugal assembly drives the motor 6 into rotation by means of a transmission mechanism such as e.g. a belt drive that is not shown in the nax Line.

An annular hot gas stream flows out of the burner

2.

The blow nozzle 3, concentrically positioned relative to the centrifugal assembly, also provides a low-temperature air flow.

A high frequency induction heating element 12, shaped like a ring, surrounds the lower part of the centrifuge assembly.

- 18 In order to avoid stresses and deformations, ^σ ο various suitable insulation or cooling elements, which are not shown in the design, are installed at suitable preparation points.

The composition of the centrifuge assembly, which in a particular case relates to FIG. 4, is as follows:

The hollow shaft 4 is secured with a hub

9. With a hub 9, a disc-shaped rim 16 is carried in one piece, which on one side bears a distribution drum 11 and a portion 15 of the centrifuge assembly.

The circumferential wall 7 of the centrifugal assembly from which the primary fibers are discharged is firmly connected to part 15. This circumferential wall is slightly inclined with respect to the vertical such that burner 2 leaking gases uniformly enclose its entire surface.

The deformation resistance of the centrifuge assembly is reinforced by a flange 8, which represents the continuation of the circumferential wall 7 and. is made from it from one piece.

Figures 5 and 4 do not show the mouths through which the centrifuged material intended for fiber production is due to; ..their small dimensions. These mouths are evenly distributed in horizontal rows. The mouthpieces in two consecutive rows are moved to each other to provide maximum distance between adjacent mouths.

The design of the centrifugal assembly must be designed in such a way that it can withstand considerable mechanical stress. However, it seems preferable to keep the bottom open. Such an arrangement, in addition to the advantages it offers to produce a centrifugal assembly, prevents any deformation that would occur

- 19 may occur due to temperature differences between the circumference and the bottom of the centrifuge assembly.

The flow of material intended for fiber production is as follows in the shown preparation. The continuous thread of molten material extends into the axis of the hollow shaft 4. This molten material receives the bottom of the drum 11. The rotation of the latter leads the material to the circumferential portion of the drum 11, which has a large number of mouths at the circumference. Starting from these mouths and under the effect of spin, the material 'is disposed of on the inner circumferential wall 7 of the spinner s / assembly 1. There the material forms a continuous layer. Still, under the effect of centrifugation, the material passes through the mouths of the wall 7 and is discarded in the form of fine filaments into the stream of drawing gases, where it is finally drawn into the form of fibers. These gases flow out of the tube 15 of the burner 2. The annular fan 5 generates a gas net that wraps the gas stream for drawing and in particular, in order to prevent the fibers from hitting the ring inductor 12.

The separation drum 11 plays an important role in the design of the traction conditions. It represents the first reserve that equalizes the flow of material. This in particular allows the material to be distributed in a very uniform manner throughout the inner surface of the circumferential column 7.

A detailed study of the distribution drum, which occurs in the Framosian pat. report no. 2442 426, cited above, emphasizes certain important features for the good operation of the assembly. In particular, it is the dimension of the mouth positioned at the circumference of the drum, from where the material is intended to be translated into fibers,

- 20 is disposed of on the inner surface of the circumferential wall 7, and on the spatial arrangement of the drum and in particular the mouth of the drum against the centrifugal assembly. More information on this subject can be obtained appropriately from the senior patentee cited above.

Centrifugal assemblies for the realization of the invention must, in addition to the aforementioned characteristics, differ from the analogous devices already known, in very large dimensions. The diameter of the centrifugal assembly at the circumferential (

walls equal to or greater than 500 mm and may reach and even exceed 1000 mm, while the centrifugal assemblies used so far do not exceed 400 mm.

This increase in the diameter of the centrifuge assembly plays an important role for many performance characteristics of this type of process. Thus, increasing the circumference of the centrifuge assembly without altering the circumference of the circumferential wall increases the surface area available for the mouth. Without changing their distribution, especially without changing their number per unit area, <we thus have a greater number of estuaries and thus increase production capacity. Improving the production achieved in this way does not affect the principles governing the quality of the fibers, and even increasing the traction effect resulting from the circumferential velocity with respect to the traction effect by gas flow under the conditions defined by the invention even makes it possible to improve these qualities. .

Although the use of centrifugal assemblies with diameters larger than the Conventionalamine dimensions is too small, the use of centrifugal assemblies with diameters of size 200

-21 300, or 400 mm at the conditions provided for in the invention of a particular advantage. Operating at circumferential speeds exceeding 50 m / sec. it enables, independently of the dimensions of the centrifugal assembly, to improve the quality of the insulation products generated.

For conventional centrifugal assemblies, an increase in circumferential speed requires an increase in rotational speed, which can reach as high as 8000 rpm. or more. The speed limits, as we have already indicated, are practical in nature. They are determined by the resistance of the centrifuge assembly to the loads exerted on it during operation.

For very large diameter centrifugal assemblies of the invention, the rotational speed is preferably between 1000 and 225 ° rpm.

For the assembly to function well, it is essential that the traction conditions are strictly identical at all points of the circumference of the centrifugal assembly. In this respect, it is necessary that the flow ί of the high temperature gas is indeed uniform.

In the most conventional embodiments, a gas stream is formed from several combustion chambers arranged uniformly around the centrifugal assembly. A chamber of this type is shown at 14 in FIG. 3 · The combustion gases produced in the chamber 14 are introduced near the circumferential wall of the centrifugal assembly and leak through the annular nozzle 15 'common to the assembly of the various combustion chambers 14.

When the dimensions of the centrifuge assembly and the draft gas generator are not too large, the gas flow is uniformly achieved without too much difficulty. The leakage gas is predominantly of the same characteristics; .the whole dimension of the nozzle 15. This becomes increasingly difficult to achieve when the dimensions are larger than is eventually the case in the invention.

In order to facilitate the achievement of conditions of uniform blowing when exiting the burner, it seems appropriate to use a single combustion chamber surrounding the centrifugal assembly. This, a single combustion ring chamber, enables better f balancing of pressures and gas flows over the entire width of the nozzle 15.

At this point in the description, and before examining the embodiments of the invention and the products obtained, it is necessary to determine the quantities which characterize the products in order to better understand the nature of the improvements which we have brought with the invention.

In this approach, we consider essentially the production of insulating materials made of felt or carpet fibers. These products themselves represent a significant part of the mineral fiber cup collection. Of course, this does not exclude the invention from the preparation of products intended for other uses

As we have already indicated, the two main types of quality we strive to achieve are thermal insulation quality, but also mechanical quality. The latter relate to very specific aspects of insulation products. In particular, the product must be well suited for the maintenance and conditioning required by products of high volume and low specific mass.

For a given product, the insulating quality is determined by its thermal resistance R. It expresses the capacity of the product under consideration to resist thermal changes when different temperatures at one and the same temperature. the other end of the product. However, this value depends not only on the characteristics of the fibers and their distribution at the heart of the product, but also on the thickness of the product.

The more dense a product is, the greater its volume

thermal resistance. To compare the thermal resistance of different products, it is therefore necessary to determine the thickness of these products. We will see later that the question of thickness f

closely related to the mechanical properties of the products. Thermal conductivity is also sometimes referred to in the literature, i.e. a size that excludes product dimensions. It's kind of an intrinsic measure of insulation quality. In practice, thermal resistance is most commonly used to characterize products. That is why we have maintained this magnitude in cases.

Despite numerous studies conducted on this subject, it is still not possible to establish a complete correlation between thermal resistance or thermal conductivity and measurable defects related to product structure. However, taking into account certain facts allows us to direct production according to the result sought.

Thus, a larger amount of fibers with the same covered surface increases the insulating properties. However, this increase is accompanied by an increase in costs. It is therefore interesting to have a given thermal resistance with the least number of fibers to the extent possible. Comparison of gram number, i.e. the mass of fibers per unit area for different products with the same thermal resistance is a measure of their quality.

- 24 In this case, the quality of the product varies inversely with the gram number.

Fiber fineness is also found to be an important factor in characterizing insulating qualities. For the same gram number, the product is as isolated as the finer the fibers.

Mechanical quantities useful for product evaluation are essentially related to the conditioning problem.

All in all, these are very voluminous products that are conveniently stored in a compressed state. However, it is necessary for the compressed product to resume a certain volume when released to best develop its insulating properties.

After compression, the fiber carpet takes up a certain thickness, different from the pre-compression thickness and the compressed state. It is desirable for the material to take as much thickness as possible after removal from the packaging to obtain a product with good thermal resistance.

In particular, for a product (taken from packaging) whose characteristics are well normalized and in particular whose thickness is guaranteed, it is important to keep a minimal volume in the compressed state. This guaranteed return thickness is also expressed by the allowable compression ratio.

It is difficult to establish a close relationship between the mechanical and insulating properties of a product, even when trying to analyze each other in terms of structure, fiber dimensions, etc. ... However, experience only shows that the improvement of insulation properties is compatible with the compression ratio.

- 25 The following are examples of embodiments of the invention.

j ° / Comparative example

These comparative examples were performed to demonstrate the advantage of operating under the conditions prescribed by the invention with respect to prior operating conditions.

The problem of setting comparative examples is elephants, as we have seen, in the variety of factors that are capable of influencing the quality of the finished product.

As far as possible, in these experiments we investigated the conditions for implementation, which allow to maintain constant parameters that are sensitive to different influences.

The following table summarizes the variable characteristics and the results obtained with respect to the finished product.

The first three experiments were performed under operating conditions that did not conform to the invention.

. I II III IV - peripheral speed (in) (m / s) 38 38 38 56.5 - flow to the mouth (kg / day) 1,30 1.16 1.1 - pressure (p) (Pa) 7580 10200 6500 4700 - Q.v / p 0,0055 0,0048 0,0068 0.013 · - micronutrient number 5 g (F) 5 3 4.5 3 - q.v / p.F 0,0018 0,0016 0,0015 0,0043 - q.v / P 13,9 16.4 9.79 20,7 - total flow in the centers of the joint (tons / day) 9 18 18 18 - gram number for, R = 2 (g / m2) 945 1080 1215 945 - compression ratio 4 2 4 4 - elongation resistance (g / g) 25O 150 250 250 Quality of prepared products is defined in this in particular the gram number needed to reach the separate thermal resistance for thickness which is right so determined- čena. We are for reference have chosen value · thermal resistance 2 m ^ ° K / U, measured at 297 ° K with thickness 90 mm. These conditions

correspond to a normalized insulator.

Compression ratio is the ratio of the guaranteed nominal thickness after 3 months' storage in the compressed state to the thickness of the compressed product.

- 27 Tensile strength was measured according to ASTM C 686 - 71 T.

Several conclusions can be drawn from the table above.

When comparing experiment no. IV according to the invention of Experiment II, for example, it is found that for constant fineness of the product and for the same global flow through the centrifugal assembly, operation under the conditions prescribed by the invention yields, on the one hand, a better quality product (gram number is less) , significantly improved compression ratio and better stretching resistance.

The observed improvement in gram number makes it possible to increase the amount of product by about 10% by the same amount of fibrous materials. Improving the compression ratio makes it very important to save on transport and storage costs.

If, as for cases I and IV, we regulate the operating conditions to have the same product quality, we find that the flow in the centrifugal assembly of the invention increases in a considerable amount, which makes the process obviously more economical.

Another way of comparing the invention to the prior art is to establish such conditions that the flow and mechanical properties are identical. In the case of Examples III and IV, however, it is found that the operation according to the invention results in a significant reduction in the micron number, which proves that the fibers produced are finer, which explains that for the same thermal resistance the gram number is smaller .

-28 Whatever the embodiment of the invention is considered, however, it is a significant improvement with respect to the prior art, as confirmed by the following results of experiments performed under other operating conditions.

2 ° / Attempts to vary different parameters

Various other parameters were modified according to the desired product quality, while remaining under the conditions of the invention.

The results of these experiments are given in the following table: V 'VI VII VIII IX - peripheral speed (in) (m / s) 56.5 56.5 75 56.5 71 - flow to the mouth (q) (kg / day) 1 0.9 0.7 1,25 1 - pressure (p) (Pa) 1600 3250 2700 4400 3000 z _f kg m 1 \ 0.035 0.015 0.019 0.016 0.024 - micron number for 4 5 e (?) 3 3 4 3 - o-v / p.F, (afe-j-k ' 0,0038 Ό, ΟΟ52 0,0064 0,0040 0,0078 ^{q, V / Zp} ' ⁽ 3an * s ⁾ 14,12 16,95 17.5 17,65 23.6 - total flow of centrifugal assembly (tons / day) 18 ' 18 18 25 20 - gram number 1080 945 915 1140 865 for R = 2 (g / m ^) - compression ratio 4 4 - 3 4 - resistance to 300 250 - 250 250

draw (g / g)

- 29 Example V is an embodiment of the conditions of the invention for the preparation of a product which can be compared with the product of Example IV. The mechanical properties are fully preserved. The micron number goes from 3 to 4, meaning that the fibers are slightly less fine. This results in a slightly smaller gram number.

The type of production corresponding to Example V, even when the products have a higher gram number than those of Example IV, is of interest. In fact, under identical spin conditions, a change in the fineness of the fibers occurs. Due to the different functioning of the burner, from which the hot drafting gases are derived. numbers.

Although an exact comparison is not possible because the micron numbers are not strictly the same in both cases, it can be done by extrapolation to keep the gram number under the conditions of the case V smaller than that of the case III. This confirms what appears at Comparison of Examples II and IV, ie the quality of the insulation products obtained according to the invention is better than that of the products obtained according to the state of the art, although this difference is more significant for the finer products.

Example VI is analogous to Example IV, except that it maintains a peripheral speed and a decrease in rotational speed. The product properties are the same as the experimental approximations.

- 3θ Case VII is equally interesting in the same sequence of ideas. The influence of the peripheral velocity on the prepared insulation products is again clearly reflected in the values of the gram number.

Example VIII is an experiment for a flow rate of 25 tonnes / day, which is not a limitation of the process of the invention, but clearly distinguishes it from the prior art in this field, when we want fibers that have good properties. The micron number remains in fact relatively small and the gram number the same, though slightly higher than in the case of V.

The significant increase in production thus obtained strongly compensates for this slight increase in the required GaA number to achieve the required insulating properties.

Example IX is another embodiment of the invention which, on the one hand, is distinguished by its increased circumferential speed and relatively low rotational speed. These operating conditions make it possible to achieve excellent mechanical and insulation properties (the gram number is particularly small) for high flow through the centrifugal assembly.

5 ° / Experiment with constant ratio q.v / p

These experiments were performed with a 300 mm diameter centrifugal assembly having d 1500 mouths.

The flow through the mouth is kept constant and, at the same time, the tangential velocity and pressure in the burner increase, approximately in the same proportions, to maintain the q.v / p ratio largely constant.

The following table summarizes results for i six market conditions. IX X . XI XII - peripheral velocity (v) .f% j 68 76 85 , 100 - flow to the mouth (q) 1 1 1 1 (kg / day) - - pressure (p) (Pa) 4100 4600 5100 6000 - ° ' ⁰¹⁶⁵ 0,0165 0,0165 0.0166 - micron number 4.0 3.5 3.0 2.5 for 5 S (R) 0,0047 0,0055 0,0068 - ·. <ή! ε · ϊ>. V 21.7 28,3 40 - total flow centers - 11.5 11.5 11.5 11.5

of the assembly.gunn.ega (ton / day)

This table shows that, under the conditions of the invention, when regulating the choice of variables \ k> v and p, it is possible to obtain finer fibers within the same limits for the same uniform flow, while increasing the circumferential velocity and the pressure of the burner, i.e. the velocity of the gases. This results in a significant reduction in the micron number and thus a useful gram number. It is also possible to obtain as small a micron number as j «2 for the material flow, which remains relatively considerable.

An analogous experiment, without modifying the burner pressure in this case, shows that, in order to achieve a very small micron number, it is necessary to significantly reduce the flow per unit and thus the total flow of the preparation.

- 32 ι ·

The same centrifuge assembly was used in this series of experiments.

XIII JfIV XV XVI XVII - peripheral speed 63 72 81 90 108 (v), (m / s) ' 1 - flow to the mouth 1.3 1.14 1.0 0.9 0.76 (q) (kg / day) - pressure (p), (Pa) 4100 4100 4100 4100 4100 - q.v / p. , (^ .. B. ^ -) 0.020 0.020 0.020 0.020 0.020 - micron number 4.5 4.0 3,5 '' 3.1 2.7 for 5 S (F) • - - «• 'VP- ^ Cdfn-s-pa ) 0.0044 0,0050 0,0056 0,0063 0,0074 18,2 20.5 23.1 26.1 30.4 - total flow 15 13 11.5 10.3 8.8

c entrifugime assembly (tons / day)

Both previous operations, in which either increasing the peripheral velocity and pressure to increase the insulating properties of the product, while reducing the flow of material, do not lead to completely equivalent results.

Experience has shown, in fact, that the mechanical properties of the formed wool are significantly better in the case of products obtained with a low burner pressure than previously indicated. We attribute these differences to the better quality of the fiber produced due to the relatively slow drag of the gas stream in the case of that resulting from the rotational motion of the centrifuge assembly.

- 55 In the previous cases, we proved by comparing certain differences in the field of manufactured products, and on this occasion said that the differences reflected in the field of production costs. It is difficult to accurately assess the economic advantage of the invention in the industrial field. Considering the various mediating factors, energy, product, material, the estimated profit may be about 10% of the unit price or more, depending on the conditions selected.

In the course of these experiments, analyzes were conducted to identify some of the specificities of the fibers produced according to the invention, in comparison with the fibers obtained according to the state of the art, in order to try to explain the improvements found, in particular by evaluating the fineness fibers to determine the micron number. Apart from this indirect approach, it is difficult to determine the characteristics of the fibers, especially their length.

However, on the basis of several findings, we can assume that the operating conditions of the invention have a beneficial effect on the formation of longer fibers. This is, for example, improved drag resistance, as well as the ability of products to withstand higher compression ratios. Further, this is the thickness of the fiber carpet that protrudes from the receiving chamber before entering the enclosure for thermal treatment of the binder. In the operation of the invention, in fact, a significant increase in thickness can be observed, which can reach or exceed 25%, however, when the conditions, the prophetic material prophet, remain identical. All these aspects can be related in some way to the increase in fiber length.

Otherwise, after attempting continuous operation for more than 200 hours, we found that the use of the centrifugal assemblies was not sufficient to replace them.

The foregoing is just a few examples of the many embodiments of the process of the invention.

They allow us to appreciate the nature of the improvements brought by the invention and also the type of benefits that can easily come from the consumer.

The production of carpet fibers by insulation has been studied in order that it represents a particularly typical use of the fiber forming process, both in terms of the quantities produced and the quality required of the fibers forming these carpets.

The invention is, of course, not limited to this type of use, the advantages it offers in the degree of fiber design, since their advantages are also found in products prepared with these fibers.

-35An indication of the best applicant-known way of economically exploiting the invention

The invention relates to a process for forming fibers of thermoplastic material, in which the material in a stretchable state is brought to a centrifugal body provided with a mouth at its circumference, the material being discharged through these mouths outside the centrifugal body in the form of filaments taken and drawn by a high-temperature gas jet directed along the circumference of the centrifugal body transversely to the threading direction.

In order to make the best economic use of the invention, it should be borne in mind that the process is carried out with the following parameters and experience gained from embodiments of the process.

The circumferential velocity of the centrifugal organ at the mouth level from which the thermoplastic material escapes should be v = 56.5 m / s. The flow of material to the individual mouth of the centrifuge assembly should be 1.1 kg / day. The emission pressure of the gas stream should be 4700 Pa. The ratio qv / p should be 0.013. Micron number (for 5 g) F should be 3 · The qv / pF ratio should be 0.0043 · The qv / F ratio should be 20.7 · The total material flow in the centrifuge assembly should be 18 t / day. The gram number of fibers obtained for R = 2 (g / m ² ) should be 945. The compression ratio is 4 and the tensile strength g / g is 250.

The quality of the prepared products is defined in the quantities given above, in particular by the gram number necessary to achieve a certain thermal resistance for the thickness which is also determined. For reference, we chose a thermal resistance value of 2 m ^ ° K / W, measured at 297 ° K with a thickness of 90 mm. These conditions correspond to a normalized insulator.

Compression ratio is the ratio of the guaranteed nominal thickness after 3 months of storage in the compressed state to the thickness of the compressed product.

Tensile strength was measured according to ASTM C 686 - 71 T.

Several conclusions can be drawn from the above explanations.

When comparing experiment no. IV according to the invention of Experiment II, in the conventional technique it is found, for example, that for constant fineness of the product and for the same global flow through the centrifugal assembly, the product of the higher quality (gram the number is smaller), significantly improved compression ratio and better resistance.

The observed improvement in gram number makes it possible to increase the amount of product by about 10% by the same amount of fibrous materials. Improving the compression ratio makes it very important to save on transport and storage costs.

To the extent that in case I of the conventional technique and of case IV of the invention we regulate the operating conditions so that we have the same product quality, we find that the flow in the centrifugal assembly of the invention increases in a considerable amount, which makes the process obviously more economical.

Another way of comparing the invention to the prior art is to establish such conditions that the flow and mechanical properties are identical. In the present case, which relates to example III according to the conventional technique and example IV according to the invention, we find that the operation according to the invention results in a significant decrease in the micron number, which proves that the fibers produced are finer, which explains that for the same thermal resistance gram number smaller.

Claims (5)

PATENT APPLICATIONS 1. The process of forming a fiber. made of thermoplastic material, such as glass, in which the material is in a stretchable state - such as a viscosity of 100 Pa.s and a temperature of 1030 to 116O ° C - to a centrifugal assembly equipped with a mouth at its circumference, the material being discharged through these outlets outside the centrifuge assembly in the form of filaments which are collectively taken and drawn by a high-temperature gas jet directed along the periphery of the centrifuge assembly transversely to the threading direction, and that the flow of fibrous material emanating from the centrifuge assembly is greater than 12 tons of material per day, respectively. 20 tonnes of material per day, characterized in that the flow of msterial to the mouth in the range of 0.1 to 3 kg / day is the circumferential velocity of the centrifugal assembly at the mouth level from which the threads exit, between 50 and 150 m / s. that 800 to 8000 rpm centrifugation takes place and that the high temperature gas spraying occurs at a pressure of 1000 to 10,000 Pa per width of the emission orifice, as a max. 20 mm. Method according to claim 1, characterized in that the circumferential velocity is between 50 and 90 m / s. Method according to one of claims 1 and 2, characterized in that the flow to the mouth is in the range of 0.7 to 1.4 kg / day. A method according to any one of claims 1 to 3, characterized in that the high temperature gas stream flows at a pressure of 2000 to 6000 Pa to a width of the emission nozzle not exceeding 15 mm. -Ί> 9 ~ Method according to any one of claims 1 to 4, characterized in that the rotational speed is in the range of 1200 and 2250 rpm.