DK159621B - PROCEDURE FOR MANUFACTURING MINERAL FIBERS USING CENTRIFUGATION - Google Patents

Description

DK 159621B

BACKGROUND OF THE INVENTION 1. Field of the Invention This invention relates to a process for the preparation of mineral fibers in which the material is fed to a centrifugal body whose peripheral wall is formed with holes from which the material is ejected from the centrifugal body and forms filaments which are transported and drawn by a gas stream. with a high temperature, which coats the circumferential wall of the centrifugal body, in a transverse direction of projection of the filaments.

According to this technique, the conveyed fibers are transported by the gas stream to a receiving means, usually constituted by a gas-permeable conveyor belt, on which the fibers are deposited to form a layer or mat.

When the final product is to be coherent, the fibers are applied to a binder during their transport to the receiving means. The layer of binder applied fiber is then fed to a heat treatment chamber for polymerization of the binder, whereupon the layer 20 is cut and formed to obtain the final product.

This technique for producing fibers, in which the drawing is due to both the spin and the tensile effect caused by the hot gas flow, has many advantages. In particular, it enables, under satisfactory 25 economic conditions, to obtain insulating products which have the best properties at a reasonable price. The arrangement of holes providing the primary filaments ensures to a certain extent a good uniformity in the production of the primary fibers. The achievement of uniform primary 30: fibers is a necessary condition for obtaining perfect final fibers. The additional drawing by means of the hot gas stream allows a relatively large amount of material to be obtained through the individual holes. As a result, each centrifugal body has a high production capacity, which contributes to lowering the unit price.

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However, these reasons, rather diagrammatically stated, are insufficient to fully explain the benefits of this method. However, they do provide an opportunity to emphasize in which processes of the same kind as in the present invention differ from the seemingly closely related methods, which, however, differ greatly in their mode of action and their results.

For example, methods are known in which the drawing takes place solely by centrifugation, ie. without circulating gas flow or possibly with circulating gas flow, however, which does not contribute to pulling the fibers. The advantage of these methods should be to save energy consumption corresponding to the generation of a high temperature and high speed draft gas stream. However, the savings achieved by this result in a significantly reduced production capacity of the centrifuge body, which is why the total production price is not reduced.

As has just been mentioned, the production of fibers and down there the manufacture of fiber products impose stringent requirements regarding both the quality and the production price. As will be discussed in more detail later in the description, these requirements are associated with many aspects. As far as quality is concerned, first and foremost the products' insulation properties, but the 25 mechanical properties also play a very important role. As far as costs are concerned, the spread is even greater and one must take into account the cost, labor, raw materials, energy consumption, etc.

The prior art also discloses methods for making fibers and insulating products with better properties than those usually obtained by the more common methods, but the teachings of the prior art correspond to embodiments which are not very convenient in terms of production price. either because the performance is too low or the energy consumption too large, or because expensive fiber material compositions have to be used.

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The measures previously proposed in methods of this kind to which the invention relates are very different, although one is limited to those which relate only to the actual manufacture of the fibers and disregard all that pertains to the subsequent treatments to which the fibers are subjected to obtain the final product.

DK Patent No. 154,496 (cf. also FR Patent No. 2,443,436) discloses measures that are particularly related to the nature of fibrous material, measures that serve to achieve better temperature control, and the transport of the material in the centrifugal body, and special measures relating to the centrifugal body itself, etc.

15 of Other Prior Publications, such as French Patent No. 1,382,917, aim to improve the conditions for the discharge of the primary fibers in the draw gas stream.

These two examples represent only a very small portion of the particularly extensive literature in the field. They show how diverse the measures can be to improve practices of this kind.

Although the intended purpose, namely the improvement of quality and price, is in all cases quite clear, 25 things are different in terms of the technical means to be used to achieve this result.

The invention provides means enabling the methods of mineral fiber preparation described above to be improved. In particular, the invention aims at improving the production capacity of the same quality or of the quality with the same production capacity.

The invention further provides new operating conditions for centrifugation plants in order to achieve the stated results.

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The invention also aims to obtain insulating products which are manufactured in accordance with these new measures and which have the appropriate insulating and mechanical properties, without the production price being too high.

To this end, a method of the kind initially described according to the invention is characterized in that the circumferential speed of the centrifugal body at the holes from which the filaments emit is at least 10 50 m / s.

The reasons for using a high peripheral speed to improve the quality of the products have not been fully established. The result can also, in a sense, be considered quite surprising. It is known that the pulling of the material filaments from the holes at the circumferential surface of the centrifugal body is an intricate phenomenon which includes the movement of the centrifugal body and the movement of the gas stream which brings the fibers with it. The simultaneity of these two effects has as a consequence that one cannot determine with certainty what role they both have in the course of the draw and what their effect is.

Nevertheless, if one wishes to analyze the phenomenon, one can reasonably assume that the fiber is obtained by what may be called a mechanical pull in which one end of the filament is held by the centrifugal body while its other end is held by the frictional forces exerted by the surrounding air. Under this assumption, the relative motion of the two "ends" of the fiber results from a combination of the rotational motion of the centrifuge body and the movement of the gas stream.

The direction followed by the filaments exiting the centrifugal body seems to prove that such a composite motion is really evident in the course of the drawing. The projection of the filament web on the plane tangent to the centrifuge body forms a certain

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5 angle with the direction of flow of the gas (usually parallel to the axis of the centrifuge body) and it is found that this angle depends on the relationship between the peripheral velocity of the centrifuge body and the gas flow velocity.

Under normal operating conditions, the angle is relatively small, since the gas velocity is much greater than the circumferential velocity of the centrifuge body. This seems to prove the essential function of the gas flow in the drawing of the fibers.

In the foregoing, only the projection of the fiber evolution in the plane tangent to the centrifugal body has been taken into account. It has been shown by experiments that the filaments also slightly distant from the circumferential surface, 15 which is why the above-mentioned comments regarding the projection also apply to the real trajectory of the fiber.

From these considerations purely geometric considerations, which will be analyzed in more detail later, should have led to the conclusion that in order to improve the drawing of the fibers from the conventional operating conditions, an increase in gas velocity was the best solution.

However, when the other conditions remain unchanged, it is found that if you noticeably increase the gas velocity in an attempt to obtain very fine fibers, you will obtain products of substantially inferior quality with very uniform, brittle and short fibers, and that the insulating blanket made with these fibers has poor mechanical properties and to a lesser extent 30 poor thermal properties.

i It has surprisingly been found that a significant improvement is achieved. the quality of the insulating products as the peripheral velocity increases while the other conditions remain otherwise unchanged.

35 While it is desirable to have a high peripheral speed, it is clear for technological reasons that this speed cannot be increased infinitely. In practice it is

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6 is difficult to exceed speeds of the order of 150 m / s, and most often the speed according to the invention will be between 50 and 90 m / s.

In particular, it is the mechanical solidity of the centrifugation bodies used that limits the peripheral velocity. Although periodic replacement of the centrifugal body cannot be avoided, the service life under the operating conditions of the invention must be compatible with the requirements of technical reliability and price 10 as in any industrial utilization.

Under the conventional operating conditions, a replacement of the centrifuge body is usually required after a period of operation of a few hundred hours.

It is important to ensure by the method according to the invention that the service life is not shorter than the life obtained by the prior art methods and that the service life may be substantially longer.

A limitation of the speed of rotation - and thus of the effects to which the centrifugal body is subjected - which does not contradict the conditions defined above, therefore seems highly appropriate for the practice of the invention. With the commonly used materials, it does not seem appropriate to exceed a limit of 8000 rpm.

However, while the speed of rotation is limited to avoid subjecting the centrifugal body to excessive stresses, the centrifugal action must remain sufficient for the fibrous material to be thrown out through the holes of the centrifugal body under satisfactory conditions, especially with respect to performance.

Consequently, the rotation speed should preferably not be less than 800 rpm.

In selecting the rotation speed and the peripheral speed, the questions raised about the solidity of the equipment will in practice result in the highest peripheral velocities usually being associated with the lowest 7

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rotational speeds, and vice versa. This behavior does not necessarily represent an optimization in terms of product manufacturing, but a compromise to obtain a reasonable service life for the plant.

The amount of material delivered by the individual holes in the centrifugal body is an essential factor in a method of this type. It is clear that this quantity directly determines the total production capacity of the centrifuge body. Indirectly, the amount per hole 10 also has an element which has a significant effect on the properties of the fibers provided.

The greater the amount per hole is, the stronger the draw must be when one wants to achieve a constant fineness.

15 Taking into account the production requirements set in practice, the quantity per hole not be quite small.

For a material such as glass or the like, an amount of 0.1 kg per 24 hours is considered a lower limit, below which no longer pay to operate.

20 On the other hand, an excessive amount cannot afford very fine fibers. With the demands made on the quality of the insulation material, the quantity of material should preferably not exceed 3 kg per square meter. Day.

25 A compromise between production capacity and fiber quality means that the quantity per hole should suitably have a value between 0.7 and 1.4 kg per Day.

Under the conditions of the invention, the production capacity of the centrifuge body can reach 30 very high values, without impairing the quality of the fibers or of the final product for this reason. It is clear that it is also possible to keep production at a less high level, especially with a view to further improving the quality.

35 On this point, the advantages of the invention are quite clear.

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The increase in production is a very important economic factor. It has been the subject of numerous prior art proposals: increasing the number of holes in the centrifuge body, increasing the cross-sectional area of the holes 5, increasing the fluidity of the material ....

While these various parameters allow the amount of material passing through the centrifugal body to be changed, these suggestions counterbalance the quality or difficulty of the life of the apparatus.

An increase in the density of the holes in the circumferential surface of the centering body, i.e. of the number of holes per not only causes a weakening of the centrifugation body, but also - in addition to a certain threshold value - turns out to have an adverse effect on the quality of the fiber.

It can be assumed that the primary fibers, if they are initially too close to each other, hit each other and adhere together before their drawing is completed. This may explain why the fibers made under these conditions are less uniform, coarser and shorter.

You encounter a problem of the same kind when - still with a view to increasing production capacity - you increase the cross-sectional area of the holes while maintaining the same values for the viscosity of the fibrous material, in which case thicker primary fibers are obtained and it is difficult to obtain a satisfactory draw, even if it affects the circulating draw gas flow.

An increase in the viscosity of a given material, i.e. an increase in the temperature of the material leads to other difficulties. The operating temperature is usually at the limit that the centrifuge body alloy can withstand. Often, the nature of the fibrous material will even be chosen taking into account this type of limitation.

From these considerations, it is impossible to increase the temperature unless the centrifuging body is used.

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turns precious metals, which raises further difficulties in terms of both price and mechanical properties.

Fluidity can be increased if materials are used, the nature of which is suitable for this, but these materials have the disadvantage that they are considerably more expensive.

According to the known literature, the methods whose aim is to achieve a quality improvement are reversed to a reduction of production.

Although the contradiction between quality and quantity exists, the invention allows for a significantly better result. If one is aiming for a good quality production - it will be explained later in description 15, how it is assessed - that can be compared to the quality previously obtained with a method of this kind, one can easily achieve a production of more than 12 tonnes of fiber material per 24 hours a day centrifugation body.

20 In practice, according to the invention, it seems appropriate to keep production at a level higher than 17 tonnes per year. 24/7 and a production capacity of 20-25 tonnes or more can easily be achieved while maintaining excellent product quality.

25 It is noteworthy that these results are achieved without the need for the above modifications.

It is not necessary to change the density of the holes or their dimensions. Thus, the primary fibers provided can in general be compared with the fibers obtained by the similar prior art methods, and as the drawing process has been improved as previously mentioned, the product quality is also better.

The drawing of the fibers in the gas stream is carried out by means of a generator whose circumferential exit opening 35 is in the immediate vicinity of the centrifugation apparatus.

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body. The gas stream has a certain width to ensure that the filaments projected from the centrifugal body remain within this gas stream and are thus kept under conditions suitable for drawing.

5 The width of the gas flow at the outlet orifice, of course, depends on the exact geometric design of the fiber plant. For a given arrangement, the useful variations are relatively narrow since, in order to limit the energy consumption, one tries to limit the width 10 of the gas flow as much as possible.

In the conventional embodiments, the gas flow initially has a width of the order of 0.3-2 cm.

Under these conditions, the pressure in the emitted gas has values which can range from 100-1000 mm water column 15 for an outlet width less than 2 cm and preferably 200-600 mm water column when the width is initially less than 1.5 cm.

In the previous analysis of the respective effects of the peripheral velocity, the amount of material and the pressure 20 in the draw gas flow, it has been stated several times that these various parameters are in practice based on the quality and price of the products produced. Relationships without exact physical significance between these various parameters can be established to account for the most convenient operating conditions of the invention.

In addition to these operating parameters, it is also important in these relationships to introduce an expression of the quality of the product manufactured. In this way, these relationships allow to clearly distinguish between the conditions of practice of the invention and those of the prior art.

According to the invention, the peripheral velocity v in m / sec. of the holes in the centrifuge body, the amount of material q in kg per their per. 24 hours from each hole in the centrifugal body and the outlet pressure p in mm of water column for the draw gas flow over a transmission length of

J

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at least 5 mm and not more than 12 mm are suitably chosen such that the ratio q.v / p is between 0.07 and 0.5, preferably between 0.075 and 0.2.

To clearly emphasize the peculiarities of the invention, it is appropriate to introduce a parameter relating to the fineness of the fibers. As will be explained later, fineness is not the only criterion for defining the product, but it is chosen because it is probably the most accessible parameter that best defines the quality of the draw made.

The fineness of the fibers is usually defined by "micronial" (F).

This size is measured as follows: A sample of usually 5 g of the product is placed in a chamber which, under given conditions, in particular the pressure, is flowed through a gas stream. The sample forms for the gas flow an obstacle that seeks to slow the passage of gas. The gas flow rate is measured with a flow meter whose values are recorded under normal conditions. The finer the fibers are for the same 20 sample weight, the lower the amount of gas flow.

The most common micronare values for insulating products range from 2 to 6 for a sample of 5 g. Products with a micronary number less than or equal to 3 at a sample weight of 5 g are considered to be very fine 25 products . They usually have a better insulation capacity per unit. product mass unit.

According to the invention, the ratio q.v / p.F is conveniently greater than 0.035, with q, v, p and F (for 5 g) being expressed by the units listed above.

Preferably, the ratio is greater than 0.040.

If one works under given conditions of pressure, the invention can also be characterized by a simplified ratio q.v / F. According to the invention, this ratio is conveniently greater than 17, preferably 35 greater than 18.

In the terms given above, express the ratio q / F. in a sense, the advantages of the method of invention 12

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period. The ratio is the greater as the product is provided in greater quantity and is finer. The parameters v and p can, for their part, be linked to the way the fibers are pulled. In any case, the terms used, as mentioned, are intended only to enable a good characterization of the invention against the prior art methods.

An advantage of the methods of the invention which are employed is that they can be used to make fibers from widely different materials.

Among the useful materials, glass materials of the following nature are preferably used.

- SiO 2 61 - 66 - Na 2 O 12.55 - 16.5 - Al 2 O 3 2.5-5 - K 2 O 0 - 3 15 - CaO 6 - 9 - B 2 O 3 0 - 7.5 - MgO 0 - 5 Fe 2 ° 3 less than 0 , 6

The values given here are expressed in percent by weight for each component. It is to be understood that the exact composition may include traces of various elements.

There are other conditions which are included in the practice of the method of the invention. In particular, they relate to the material (temperature) and the draw gas flow (temperature). These conditions do not differ significantly from the corresponding previously described conditions and therefore do not need to be discussed further here.

The invention is explained in more detail below with reference to the schematic drawing, in which fig. 1 is a perspective view of a centrifugal body and of the path a fiber follows from the circumferential surface of the centrifugal body; FIG. 2 shows the projection of the web for the fiber of FIG. 1 on the plane tangent to the centrifugal body; FIG. 3 is a sectional view through a fibrating apparatus which may be used in the practice of the invention; and FIG. 4, on a larger scale, part of the embodiment of FIG. 3 with the various elements included in the zone in which the fibers are drawn.

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FIG. 1 and 2 are intended to show the respective influences of centrifugation and gas flow on the drawing of the fibers.

FIG. 1 schematically shows a centrifugal body 5, the circumferential surface of which is formed with holes. FIG. 1 also shows the path followed by a fiber F as well as the plane T which tangles the wall of the centrifuge body at the location from which the fiber F exits.

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

Although shown only schematically, the path of the fiber represents. in this figure most of the characteristics that are effectively found.

Thus, it is found that the material removes 15 from the wall of the centrifugal body and that the web, after a short stretch, is bent under the influence of the hot gas stream coating this wall.

Then, the fiber follows approximately the direction corresponding to the resultant of the speed of the centrifuge body 20 and the gas flow rate.

In the plane tangent to the centrifugal body, the projection is shown in FIG. 2, where O represents the hole and where α represents the angle between the projection image and the direction AND in which the gas flow is moving.

25 Under the usual conditions of the speed of the centrifugal body represented by the vector OP, and the gas velocity is the angle α of an order of magnitude of at least a dozen degrees.

On this basis, it can be understood that even a relatively large increase in the speed of the centrifugal body, cf. the dotted line, could not lead to a significant improvement in fiber drawing. The intensity of this draw can be represented by the sum of the vectors AND and OP. An increase in OP only gives a slight variation 35 of the sum because the angle α is small. To improve the draw, on the other hand, it would seem more appropriate to increase the gas velocity. It will later be referred to

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In practice, it is shown that it is quite the opposite to be found and that in order to achieve a better drawing and a higher quality of the fibers, it is appropriate to increase the peripheral velocity of the centrifuge body.

We will now take a closer look at the structure of the plant for the production of the fibers.

The FIG. 3, the centrifugal body 1 itself is arranged horizontally and is supported by an arrangement 4 constituting the shaft of the centrifugal body.

This shaft is mounted in a ball bearing 5. The shaft 4 and the centrifugal body are driven by a motor 6 through transmission means such as transmission frame.

The circulating flow of hot gas starts from a burner 2.

A circular fan ring 3 concentric with the centrifuge body also emits a circular flow of lower temperature air.

An annular element 12 for heating by high-frequency induction surrounds the lower part of the centrifuge body.

In order to avoid stresses and deformations, various elements not shown for isolation or cooling are arranged at appropriate points in the apparatus.

The centrifugal body 1 comprises the following components, cf. also fig. 4:

The hollow shaft 4 is attached to the hub 9 which is firmly connected to a disc-shaped rim 16 carrying a distributor tray 11 and a portion 13 of the centrifugal body 30.

The circumferential wall 7 of the centrifuge body, from which the primary fibers originate, has a fixed connection with this part 13. The circumferential wall has a smaller slope relative to the vertical, so that the gas flow emitted by the burner 2 uniformly covers the entire wall surface.

For strengthening the centrifuge body against deformations, the circumferential wall 7 is firmly connected to a 15

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flange 8.

In FIG. 3 and 4, the holes through which the material is thrown out are shown because they are very fine holes. These holes are evenly distributed in horizontal 5 rows. The holes in two successive rows are offset from each other so that the maximum distance between adjacent holes is provided.

The centrifugal body must be designed to withstand strong mechanical stresses. However, it is convenient to leave its lower parts open. In addition to making it easier to manufacture the centrifuge body, this measure also has the function of avoiding the deformations that could be due to temperature differences between the circumferential wall and the bottom of the centrifuge body.

In the illustrated plant, the material to be converted into fibers moves as follows: An uninterrupted jet of molten material flows downward through the hollow shaft 4 and collects at the bottom of the tray 11. As the tray 20 is in rotation, the material is fed to the tray 11 circumferential surface, in which many holes are provided, from which the material, under the influence of centrifugal force, is thrown out to the inside of the centrifugal body 11 s circumferential surface 7, where the material forms an even layer.

Under the influence of centrifugal force, the material is passed through the holes in the circumferential wall 7 and thrown out in the form of thin rays in the flue gas, which pulls the material forward to form fibers. The gas stream exits from burner 2 "nozzle 15. The circumferential blower 3 30 provides a gas layer that surrounds the draw gas stream and controls it so that there can be no fibers hitting the induction ring 12.

The distributor tray 11 has a significant role in the drawing process, forming a first stock which makes the material supply more even, so that it is possible in particular to distribute the material in a very uniform manner over the entire inner surface of the circumferential body 16

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wall 7.

A detailed description of the distributor tray can be found in the aforementioned French Patent Specification No. 2,443,436, which emphasizes certain important characteristics of good function 5 of the plant. This concerns in particular the dimension of the holes in the circumferential surface of the tray, from which the material is projected towards the inside of the circumferential wall 7, as well as the spatial structure of the tray and in particular the arrangement of the holes in the tray in relation to the centrifuging body. Further information on this may conveniently be found in the aforementioned patent.

In addition to the aforementioned characteristics, the centrifuge body for practicing the invention differs from the prior art systems in substantially larger dimensions. Conveniently, the diameter of the centrifugal body to the circumferential wall may be 500 mm or more, for example up to 1000 mm, while the centrifugal bodies used so far usually do not have a diameter of more than 400 mm.

This increase in the diameter of the centrifugal body plays a significant role for many of the characteristics of a method of this kind. Thus, an increase in the circumferential length of the centrifuge body, without changing the height of the circumferential wall, increases the available space for the holes. Without changing their distribution, especially without changing their number per day. Thus, a larger number of holes can be made available, thus increasing production capacity. The increased production thus obtained does not change the measures which determine the quality of the fibers, and the better drawing due to the peripheral velocity relative to the drawing due to the gas flow even allows to achieve in accordance with the invention an improvement in quality.

Although it is preferable to use centrifugal bodies with a diameter larger than the usual diameter.

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17 meter values, the use of centrifugal bodies having a diameter of approx. 200, 300 or 400 mm under the conditions of the invention confer certain advantages.

In particular, the operation at peripheral speeds of more than 50 m / s allows 5, independently of the dimensions of the centrifuge body, to obtain an improvement in the quality of the insulation products produced.

In the conventional centrifuge bodies, the increase of the peripheral speed involves an increase of the rotational speed which can reach up to 8000 rpm or more. As mentioned earlier, there are practical reasons why the speed of rotation is limited. The boundary is determined by the strength of the centrifuge body against the force effects that occur during operation. For very large diameter centrifuge bodies according to the invention, the rotational speed is preferably between 1000 and 2250 rpm.

For a good operation of the system, it is of the utmost importance that the drawing conditions are exactly the same at all points of the circumferential surface of the centrifuge body.

In this regard, it is necessary that the very hot gas flow is very uniform.

In the more common embodiments, the gas flow is provided by several combustion chambers evenly distributed around the centrifugal body.

A chamber of this kind is shown at 14 in FIG. 3. From the chamber 14, the combustion gas is fed to a location near the circumferential surface of the centrifuge body, and it exits through a circular nozzle 15 common to all 30 combustion chambers 14.

When the centrifugal body or the draft gas generator, respectively, do not have too large dimensions, it is not very difficult to obtain a uniform gas flow. The gas flow has substantially the same properties over the entire extent of the nozzle 15. This is more difficult to achieve in the case of larger dimensions, for example in accordance with the invention.

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In order to obtain a uniform blowout at the exit from the burner, it is advisable to use a single combustion chamber surrounding the centrifugal body. This single annular combustion chamber 5 provides a better distribution of pressure and gas flow over the entire width of the nozzle 15.

At this point of description and before looking at examples of exercise and the products obtained, it is necessary to clarify the sizes that characterize the products in order to better understand the nature of the improvements achieved by for the invention.

In this regard, one will deal mainly with insulation products formed by a felt or a mat of fibers. These products alone represent a significant portion of all the possible uses of mineral fibers. However, this should not preclude the use of the invention in the manufacture of products for other purposes.

20 As mentioned earlier, there are in the main case two properties one wishes to achieve, namely insulating property and mechanical properties. The latter relate to quite specific aspects of the insulation products.

In particular, the product must be suitable for handling and for the treatment required for high volume and low density products.

For a given product, the insulating ability is defined by the thermal resistance R, which expresses the product's ability to resist heat exchange when there are different temperatures on one side and the other side of the product, respectively. This size depends not only on the characteristics of the fibers and their distribution in the product, but also on the thickness of the product.

The thicker a product, the greater its 35 thermal resistance. Therefore, to compare the thermal resistance of different products, it is necessary to specify the thickness of the products. We must

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19 later see that the issue of thickness has close connection with the mechanical properties of the products. In the literature, reference is sometimes made to the thermal conductivity, which size disregards the product dimensions.

5 It is about a measure of the actual insulating ability. In practice, however, the thermal resistance is most often used to characterize the products. It is therefore this size that is used in the examples given later.

10 Despite the numerous studies done on this topic, it is not possible at this time to establish a complete correlation between the thermal resistance, or thermal conductivity, and the measurable sizes that relate to the structure of the product. However, some considerations allow the production to be oriented in dependence on the intended result.

A greater amount of fiber per thus, the unit of space allows to increase the insulation capacity, but this increase is accompanied by a greater cost. It is therefore appropriate, as far as possible, to have a given thermal resistance with as few fibers as possible. A comparison of the fiber quantities.pr. area unit for different products with the same thermal resistance gives a measure of the respective properties of the products. In that case, the quality of the product varies inversely with the amount of fiber.

It is also found that the fineness of the fibers is an important factor in characterizing the insulation properties. For the same amount of fiber, the more insulating the product, the finer the fibers.

30 The mechanical sizes useful for assessing the product are generally related to the manner in which the product is packaged.

In the case of very bulky products, it is appropriate to package the products in a compressed state, but it is necessary, however, that the compressed product, when released from its packaging, recover a certain volume so that it is as good as possible.

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20 regains its insulation properties.

After being compressed, the fiber mat will again get a certain thickness different from the thickness before the compression operation and from the thickness in the compressed state. It is desirable that the thickness, after removing the product from its packaging, be as large as possible, so as to obtain a product having good thermal resistance.

For a product removed from the packaging which has quite certain properties and in which the thickness is particularly guaranteed, it is important that the product in the compressed state takes up as little volume as possible. This guaranteed return to thickness is also expressed by the acceptable compression ratio.

15 It is difficult to establish a close relationship between the mechanical properties and the insulation properties of a product, even if one tries to analyze one in relation to the structure, the fiber dimensions, etc., but experience only shows that the improvement-20 gene of the insulation properties is compatible with the improvement of the compression ratio.

Examples of practice of the invention are given below.

1) Saroma equation experiments.

These comparative experiments have been carried out to highlight the advantages obtained in relation to the prior art operating conditions when carried out in accordance with the invention.

A difficulty in setting up these comparison experiments is - as mentioned earlier - due to the many factors that may influence the quality of the final product.

As far as possible, these efforts aim to have such conditions for exercise that the 35 parameters that are sensitive to different influences are kept at the same level.

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The following table sets out the various characteristics and results obtained for the manufactured product. The first three tests are carried out under operating conditions which are not in accordance with the invention.

I II III IV

- peripheral velocity v (m / s) 38 38 38 56.5 - amount of g per hole (kg / day) 1.1 1.30 1.16 1.1 - pressure p (mm VS) 758 1020 650 470 10 - qv / p 0.055 0.048 0.068 0.13 - micronearity for 5 g (F) 3 3 4.5 3 - qv / pF 0.0184 0.016 0.015 0.043 - qv / F 13.9 16.4 9.79 20.7 - Total amount (T / day) from the centrifuge body 9 18 18 18 - Amount of fiber for R = 2 (g / m 2) 945 1080 1215 945 - compression ratio 4 2 4 4 - tensile strength (g / g) 250 150 250 250

The quality of the products produced is defined in this table in particular by the amount of fiber required to obtain a given thermal resistance for a given thickness as well. As a reference, the value of 2 m 2 ° K / W measured at 297 ° K for a thickness of 90 mm, which corresponds to an insulating product according to the standards, has been chosen.

The compression ratio is the ratio of the guaranteed nominal thickness after a three-month compressed state storage to the thickness of the compressed product.

30 Tensile strength is measured according to the standard ASTM C 686-71 T.

The following conclusions can be drawn from the following table:

For example, if comparing Experiment XV in accordance with the invention with Experiment II, one can observe that with the same product fineness and the same total amount from the centrifuge body,

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22 proceed in accordance with the invention in part obtains a better quality product (the amount of fiber is smaller), a significantly better compression ratio and a better tensile strength.

5 The improvement in the amount of fiber found allows the same amount of fiber material to be increased by about * 10%. The improvement of the compression ratio provides a significant improvement in terms of transport and storage costs.

If, as for Examples I and IV, if the operating conditions are set to have the same product characteristics, it is found that the performance of the centrifuge body in accordance with the invention is very substantially greater, which means that the process 15 is clearly more economical.

Another way of comparing the invention with the prior art methods is to establish such conditions that the performance and mechanical properties are the same. In that case, cf. Examples III and IV, if you proceed in accordance with the invention, it is found that there is a substantial reduction in the micro near number, proving that the fibers produced are finer, which explains , why for the same thermal resistance a smaller amount of fiber is obtained. area-25 unit.

Regardless of how one considers the method according to the invention, it must be noted that it ensures a significant improvement over the prior art methods, which is confirmed by the subsequent experimental results under different operating conditions.

2) Trials with variation of different parameters.

Various other parameters have been changed within the framework of the conditions according to the invention depending on the intended product qualities.

35 These experiments have yielded the following results;

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V VI VII VIII IX

- peripheral velocity v (m / s) 56.5 56.5 75 56.5 71 - quantity q per hole (kg / day) 1 0.9 0.7 1.25 1 - pressure p (frame VS) 160 325 270 440 300 5 - qv / p 0.35 0.15 0.19 0.16 0.24 - micronary number for 5 g (P) 4 3 3 4 3 - qv / pF 0.088 0.052 0.064 0.078 0.078 -qv / P 14.12 16.95 17.5 17.65 23.6 - total amount (T / day) from 10 centrifugal member 18 18 18 25 20 - fiber amount for R = 2 (g / m2) 1080 945 915 1140 865 - compression ratio 4 4 3 4 - tensile strength (g / g) 300 250 - 250 250 15 Example V is performed by the method of the invention for the preparation of a product comparable to the product of Example IV.

You have exactly the same mechanical properties. The micro near number has changed from 3 to 4, which means that the fibers are not as fine. As a result, you get a slightly higher value for the amount of fiber per day. unit area.

The type of production in accordance with Example V is interesting, although the products have a slightly higher value for the amount of fiber per day. area unit than in Example IV.

While the same conditions for the centrifugation have been maintained, the change in fiber fineness is due to differences in the operation of the burner giving off the hot draft gas. The energy consumption for operating the burner in accordance with Example V is substantially reduced compared to Example IV, which can usefully offset the observed increase in the amount of fiber per unit. unit area.

Although an exact comparison is not possible, as long as the mieronary number is not exactly the same in the two cases, by extrapolation it can be concluded that for a micronary number of 4.5, the amount of fiber will correspond to Example V be less 24

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than, for example, III. This confirms what is evident from a comparison between Examples II and IV, namely that the quality of the insulation products made in accordance with the invention is better than the quality of the products made in accordance with the prior art methods. although this difference is more pronounced for the finest products.

Example VI corresponds to an exercise, as in Example IV, but at the same peripheral speed and at a reduced rotational speed. The products have the same properties except for experimental-based approaches.

From these considerations, Example VII is also interesting. The influence of the peripheral velocity on the insulating properties of the products produced is also clearly seen in the value of the amount of fiber per minute. unit area.

Example VIII corresponds to an experiment with a production of 25 tonnes per liter. 24 hours, which does not constitute a limit to the method of the invention, but clearly separates the invention from the previous embodiments when good quality fibers are desired. Micronar number and fiber amount per area units are relatively low, although slightly larger than in Example V.

The noticeable production improvement achieved offsets this small increase in the amount of fiber per month.

25 unit of area needed to achieve the required insulation properties.

Example IX relates to another embodiment of the invention characterized by both a high peripheral speed and a relatively low rotational speed. These 30 conditions of practice allow excellent mechanical and insulating properties (the fiber quantity per unit area is particularly low) to achieve great performance from the centrifugal body.

3) Experiments with constant q.v / p ratio.

35 These experiments were performed with a 300 mm diameter centrifuge body with 11,500 holes.

The amount of material per hole is kept constant at the same time 25

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with the tangential velocity and pressure of the burner increasing in approximately the same ratio, so that the ratio q.v / p is kept substantially constant.

The following table gives the results for 5 six operating conditions.

X XI XII XIII

peripheral velocity v 68 76 85 100 quantity q per, hole (kg / day) 1111 pressure p (mm VS) 410 460 510 600 10 qv / p 0.165 0.165 0.166 0.166 micron number for 5 g (F) 4.0 3.5 3.0 2.5 qv / pF 0.041 0.047 0.055 0.068 qv / F 17 21.7 28.3 40 total amount (T / day) from the centrifuge body 11.5 11.5 11.5 11.5

This table shows that in accordance with the invention, by setting the variables v and p with the same unit performance within certain limits, it is possible to make the fibers finer by simultaneously increasing the peripheral speed and pressure in the burner, ie. gas velocity. This leads to a significant reduction of the micro-near number and thus of the fiber usefulness per capita. unit area.

One can also obtain as low a micronary number as 2 with a relatively large amount of material.

25 A similar experiment, this time without changing the pressure in the burner, shows that in order to obtain a very small micronar number, it is necessary to have a significant reduction in the output per annum. unit and thus of the total amount of material produced by the plant.

30 35 26

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In this series of experiments, the same centrifuge body is used.

XIV XV XVI XVII XVIII

peripheral velocity v 63 72 81 90 108 5 q q. hole (kg / day) 1.3 1.14 1.0 0.9 0.76 pressure p (mm VS) 410 410 410 410 410 gv / p 0.20 0.20 0.20 0.20 0.20 micronearity for 5 g (F) 4.5 4.0 .3.5 3.1 2.7 qv / pF 0.044 0.050 0.056 0.063 0.074 10 qv / F 18.2 20.5 23.1 26.1 30 , 4 total amount (T / day) from the centrifuge body 15 13 11.5 10.3 8.8

However, the two previous operations in which to improve the insulation properties of the product either simultaneously increase the peripheral velocity and pressure or decrease the amount of material, do not lead to completely equivalent results.

Experience has shown that the felt felt has significantly better mechanical properties than in the case of products which - as previously mentioned - are manufactured at a low pressure in the burner.

These differences can be attributed to a better quality of the fiber produced due to a relatively modest draw with the gas flow relative to the draw due to the rotational movement of the centrifuge body.

In the preceding examples, by comparison, some of the differences with respect to the products produced are highlighted, and in this connection it has been stated that these differences are reflected in the production price. It is difficult to accurately assess the economic advantage afforded by the industrial exploitation of the invention. Taking into account the various factors such as energy, product, material, the improvement can be expected to be approx. 10% or more of the unit price, depending on the conditions chosen.

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During these experiments analyzes were made to try to determine what properties the fibers produced in accordance with the invention exhibit in relation to the previously obtained fibers in order to be able to account for the improvements found, in particular in assessing the fineness of the fibers. for the purpose of determining the micronary number. Apart from this indirect analysis, it is difficult to determine the characteristics of the fibers, in particular their length.

However, there are several things which may lead one to believe that the operating conditions of the invention allow the production of longer fibers. For example, it is the improved tensile strength. It is also the ability of the products to withstand greater compression.

It is furthermore the thickness of the fiber mat in the receiving chamber before being introduced into the binder for heat treating the binder. If you proceed in accordance with the invention, an increased thickness which can reach 25% or more is found, while the other 20 parameters, in particular the amount of material, remain unchanged. All these aspects can in some way be associated with an increase in fiber length.

In addition, during continuous operation tests for more than 200 hours, it has also been found that the wear on the centrifugal body was not of such a nature that the centrifugal body was required to be replaced.

These are just a few examples of the many peculiarities noted in the practice of the method of the invention.

They provide an opportunity to assess the nature of the improvements according to the invention as well as the type of benefits it provides to the user.

The manufacture of a fiber mat for insulating purposes has been investigated because it is a particularly characteristic example of utilization of methods of fiber production, partly because of the quantities produced and partly because of the quality sought for the fibers of such mat.

Claims (16)

A process for producing mineral fibers in which the material is extensibly fed to a centrifugal body whose circumferential wall is formed with holes from which the material is ejected from the centrifugal body to form filaments which are transported and drawn by a high temperature gas stream which coats the circumferential wall. on the centrifugal body, in a 10-way transverse direction of filament, characterized in that the circumferential velocity of the centrifugal body at the holes from which the filaments exit is at least 50 m / s. Method according to claim 1, characterized in that the peripheral velocity is not more than 150 m / s. Method according to claim 1, characterized in that the peripheral speed is between 50 and 90 m / s. 20 0.4. Process according to any one of claims 1-3, characterized in that the amount of material g in kg per kg. 24 hours from each hole and the outlet pressure in mm water column for the hot gas stream having a width greater than 5 mm and less than 12 mm is chosen such that the ratio qv / p is kept within the range 0.07-0.5, where v is the peripheral velocity in meters per meter. second. Process according to claim 4, characterized in that the ratio g.v / p is kept within the range 0.075-0.2. Process according to any one of the preceding claims, characterized in that the quantity of material per hole is between 0.1 and 3 kg / day. Process according to any one of claims 1-5, characterized in that the quantity of material per hole 35 is between 0.7 and 1.4 kg / day. 29 DK 159621 B Process according to any one of the preceding claims, characterized in that the hot gas stream is discharged at a pressure of 100-1000 mm water column from a discharge opening with a width of not more than 20 mm. Method according to any one of claims 1-7, characterized in that the hot gas stream is discharged at a pressure of 200-600 mm water column from a discharge opening with a width of not more than 15 mm. Method according to any one of the preceding 10, characterized in that the rotational speed of the centrifuge body is between 800 and 8000 rpm. Method according to any one of claims 1-9, characterized in that the rotational speed is between 1200 and 2250 rpm. Process according to claim 1, characterized in that the ratio q.v / F, where q represents the amount of material per unit weight. hole in kg / day, v is the peripheral velocity in m / s, and F is the micronar number of the 20 fibers produced, is greater than 17. Process according to claim 12, characterized in that the quantity of material q per hole is between 0.1 and 3 kg / day. Process according to claim 1, characterized in that the ratio q.v / p.F, where q is the amount of material per unit weight. hole is in kg / day, v is the peripheral velocity in m / s, p is the outlet pressure in mm of water column for the gas flow with a discharge width not less than 5 mm and not greater than 12 mm, is greater than 0.035. Method according to claim 14, characterized in that the quantity of material per hole is between 0.1 and 4 kg / day and the outlet pressure for the hot gas flow is between 200 and 600 mm water column. Method according to claim 14 or 15, characterized in that the ratio q.v / p.F is greater than 0.040.