CN1009731B - Process for the production of mineral fibre mats from a molten material - Google Patents

Abstract

The present invention relates to a production technology of mineral fiber boards. In the considered technology, when passing through a centrifugal machine whose circumferential wall is drilled with holes, molten materials are sprayed out of the centrifugal machine from the holes to become single fiber. A stream of air current which comes from the circumference of the centrifugal machine blows up the single fiber and make the single fiber spread. The stream of air current which presents annular originally forms conical air current on the whole when the air current reaches to the opening of the centrifugal machine. According to the present invention, fiber particulates are added by the stream of air current whose direction is perpendicular to the moving direction of the air current which blows up the newly generated fibre and blow in from the contracted region of the air current.

Description

Process for the production of mineral fibre mats from a molten material

The invention relates to the production technology of mineral fibre felt.

The manufacture method of the most widely used industrial mineral fibre felt comprises: the fused material is sprayed from whizzer perforate on every side and the formation fiber, and molten material ejects with ultimate fibre by these eyelets from whizzer.One hot gas flow carries ultimate fibre and fiber is attenuated to blow along the circumferential wall of whizzer at a high speed.

The production method of this fibrefelt had had a large amount of achievements to deliver.Up-to-date should mention french patent application No.2443436 and european patent application No.0091866.

Supervene the limit portion of a considerable number of byproduct, particularly fibrefelt with the production of fibrefelt, will fitly cut burr for reaching width dimensions and guaranteeing that the felt limit is straight.In addition, remove the product of all sub-standard requirements from the production line everywhere.The byproduct of all these fibers may account for output 10% or more.As previously mentioned, these byproducts can be discarded, and also can transform to be used.

In the technology of above-mentioned producd fibers, have at least a part of this byproduct in fiber production process, to be mixed again traditionally.For this purpose, byproduct is earlier with milling or the method for ramming reduces to become particulate or little with its size.The fibrous nits that obtains is like this delivered to air-flow in the container of fiber-forming, here mixes with different abundant degree with the fiber that just formed, and mixing is that the fiber collecting in above-mentioned new generation carried out in the past at collector.

Say the production of fibrefelt more back.Be necessary to describe in detail the condition that the fiber that leaves whizzer forms a fibrefelt after treatment.

A large amount of eyelets is all arranged on the perisporium of each whizzer.The air-flow of being close to whizzer blows the whole fibers that generated that carry and constitutes the thin curtain of a kind of annular, and this thin curtain has the very form of rule, and stretches to the collecting conveyor direction.

Transport unit can see through gas, and it allows gas by keeping fiber here, gas be inhaled into be located at below the transport unit, keep in the chest of vacuum in a suitable manner.

Fiber between whizzer and collecting conveyor by the time sprayed a layer binder, bonding interfixes in the felt that binding agent for good and all in the end forms fiber.The operation of fiber coating generally includes one thermal treatment so that binding agent is fixed, and thermal treatment is to carry out after the fiber on collecting conveyor of interweaving is formed felt.

When the desired output of the equipment of industrial product was very high, many whizzers in a row were arranged in and help to form felt on the same transport unit.

Mixing under the situation of fibrous nits, mixing normally of particulate carried out between whizzer in succession.Mix fibrous nits between the device of two new fibers of generation, can reach sufficient mixing, so that particulate is diffused in the final made felt equably.

In order to obtain the performance of moulding felt, particulate is scatter in the felt body.Generally speaking, particularly the resistive properties role is the same with the new fiber that produces even fibrous nits is for the fibrefelt performance, and the existence of these particulates still can make its performance be improved substantially, for example physical strength and product appearance.

Generally can say so, everyly realize that this improved local product can improve at large.Under any circumstance, this improved degree can be very not big, unless the quantity of particulate surpasses certain limit.If particulate is distributed in the fibrefelt equably, just might add a large amount of particulates and danger that going beyond the limit does not appear in certain point in the felt body.

Experience shows that the traditional method that adds particulate in the mobile fiber does not reach diffusion profile fully uniformly.The trend that particulate has a kind of stratiform to pile up is concentrated on newly-generated corpus fibrosum more or less.

Analysis to the fibrefelt composition will show that each whizzer forms the fiber laydown layer of oneself.In this case, particulate can be preferentially attached between these two formed layer of fibers of whizzer from middle the spraying into of two whizzers.

Fiber the transport unit width be distributed in transport unit than broad in (for example width is above 2 meters) also can have problems usually.In order to guarantee fiber full and uniform distribution on whole width, general custom trend towards or increase blow carry fibrous airstream width (for example, has the fibrolaminar effect of broadening from the cross-jet of air-flow), or change the direction (for example, air channel waveringly alternately moves on to the other end with fibre plate from an end of transport unit) of air-flow periodically.

The similar mechanism that is used for newborn fiber can be used to make particulate in the wide lateral dispersion of felt.This need roll up the combination of mechanism in relatively limited space.Therefore people adopt more uncomplicated but also more uppity device of while usually, blow the air-flow that carries particulate as using deflecting plate broadening on the whole width of transport unit.

In the case of best prior art, dispersive lost efficacy and reduced to minimum, but can't control fully.One of main consequence of this situation is to have limited total ratio of the particulate that mixes with these method production mineral felts.

The Application of Technology need be considered from economy.The particulate that is added in the newborn fiber is good in response to distributing with technology, and therefore the quantity of the particulate that reclaims as felt body composition does not have in the quality to felt should increase under the situation of disadvantageous effect.Purpose of the present invention that Here it is.

According to the present invention, introduce fibrous nits and traditional technology antithesis, said particulate is in check, make work as particulate be right after whizzer below locate to pass the annular fibre curtain.

The condition that well-known fibre curtain forms from the whizzer below plays an important role to the production of felt.Especially, traditional target is to prevent that as far as possible especially in order to prevent to form thick fiber strip as far as possible, this will be unfavorable for the fiber uniform distribution in the felt body to blowing any interference of gas of year fiber.The present invention is surprised to find that and is not having significant change near the particulate of being brought in the annular curtain by air-flow on the position of whizzer for the sort of yarn that forms, and particulate is distributed in newly-generated fiber very equably.

The air-flow that enters annular curtain place by the observation particulate can partly be explained above-mentioned phenomenon.So find,, and under certain speed condition (below will explain), blow the air-flow that carries particulate and just explode if air-flow is passing curtain with the enough near place of whizzer.

Do not study the mechanism that causes " blast " in great detail, but this blast makes particulate distribute well in blowing the air-flow that carries fiber.Generally speaking, this zone of whizzer below not only is subjected to along the domination of whizzer unfolded air-flow, but also be subjected to blowing the air-flow that carries fiber the joining of induced air-flow.

The subatmospheric zone of pressure is right after square one-tenth under whizzer, and tendency is with the filament contraction of slices.Outside this zone, originally annular but air-flow that shunk can be spread with as the taper.

According to the present invention, mix particulate and preferably be selected on the position of air-flow curtain contraction.

The particulate that is mixed moves to blowing carrier gas stream till shrinkage strain place of air-flow, and this has just reached particulate is disperseed well.

If it is far below the air-flow shrinking zone to mix the place of particulate, the distribution of particulate just can not spread all over the whole air-flow that carries fiber that blows again.Meanwhile, keep a minor increment being arranged, make flowing of air-flow that fiber attenuates interference-free in the position that fiber attenuates with whizzer.This distance is perhaps very little; Usually be chosen in apart from the places beyond 150 millimeters of the scheming belows, the fiber that is generated is stable, and blows passing of the air-flow that carries particulate and no longer hinder the fiber desired condition that attenuates that makes.

For the ease of mixing, blow the air-flow that the air-flow lateral alignment of carrying particulate attenuates fiber.The propagation direction of these two strands of air-flows is inequality.

Being that vertical direction is angled with normal direction allows, as long as this inclination angle still can make the air-flow that blows year particulate penetrate the circular fiber curtain.

Furtherly, the air-flow of inclination will enter fibre curtain, and can not impact the parts of the contraction place that is positioned at curtain, be meant the device that is used for jet binder especially.

Consider these conditions, blowing the air-flow that carries particulate should become 30 ° at least with vertical direction, at 45 at least better.

Blow the direction of carrying particulate and be positioned at and comprise production line, thereby to comprise on the vertical plane of the direction that conveyer extends be favourable.Different therewith directions (although blow energy that the air-flow that carries particulate produces compare with the air-flow of contraction quite low, we will to this point) may cause that blowing the air-flow that carries fiber produces deviation with delivery direction, thereby the change distribution.Point to respect to the fore-and-aft plane that transmits if blow the air-flow that carries particulate, then lateral distribution departs from as the same with unaffected even blow the air-flow that carries fiber a little.

The present invention is described in more details with reference to the accompanying drawings.

Figure 1 shows that the synoptic diagram of producing and collecting the mineral fibre felt production line of fiber; Particulate adding method shown in the figure is a traditional method,

Figure 2 shows that an embodiment who adds particulate by the present invention,

Fig. 3 a mixes the sectional drawing of particulate for observing traditional method, and the distribution of visible granular is bad,

Fig. 3 b is similar to Fig. 3 a, just is to add the product sectional drawing that particulate is produced by condition of the present invention.

Fig. 1 represents to be used for three whizzers 1,2,3 of producd fibers, constitutes the part of production line.This several means is that the top of closed collecting chamber 4 is arranged in delegation at one basically.They be installed in the transport unit 5 that constitutes the collecting chamber bottom above.Transport unit 5 is gas-pervious.

According to the size of collecting chamber 4, one or more box 6 be directly installed on transport unit below.Make pressure in the box 6 keep below normal atmosphere in the collecting chamber 4 with an air extractor (not showing on the figure).This vacuum makes the air-flow that blows year fiber pass transport unit 5 and is drained, and fiber is stayed on the transport unit 5.

Each whizzer 1,2,3 produces an annular fibre curtain 7, is transported on the collecting conveyor by the air-flow that fiber is attenuated.After shrinking, blow the air-flow that carries fiber and enlarge the formation taper at 8 places, position.

In Fig. 1, each several part is expression in proportion, but reflected as far as possible exactly fiber from the whizzer to the transport unit the path of process.

According to economic and principle easily, between each whizzer as far as possible from more closely, like this, trample factually, as shown in Figure 1, each fibre stream of dispersing out from adjacent whizzer has the trend of converging before arriving transport unit.

Usually the various devices of installing on the path of fiber process are not shown on this figure, can be used to improve the device of the distribution of fiber on the transport unit width such as the nozzle of injection water and binding agent and other.These devices are installed in the position of fibre curtain shrinking zone 8 or usually in its downstream.

Only show three whizzers among Fig. 1, and the quantity of whizzer is very many on a large scale industry production line, nearly 10 or even 12.It will be appreciated that hereinafter the present invention can be applicable to any amount of whizzer, even be used for an independent whizzer, traditional particulate method of mixing then necessarily requires to use under the occasion of several whizzers.

Be retained in the fiber on the transport unit 5 owing to fall weave in mutually.Fiber layer thickness on transport unit constantly increases from the end to end of production line, and this is to form owing to piling up continuously from the fiber of each whizzer.In the outlet of collecting chamber 4, pile up the various finished product felts that are treated as of layer of fibers 9 processes that form.Especially make the binding agent composition generation polymerization that sprays on the fiber and make the felt typing through one thermal treatment.In addition, the banded felt of successive is cut into the size of requirement.

As previously mentioned, limit portion is cut off usually, after being shredded or pulverizing, directly is incorporated in the collecting chamber again with particulate or fine grain form then.

To collecting chamber 4, particulate delivers by air-flow from place that particulate is made.

Mix the place of particulate normally between two whizzers toward collecting chamber.The tracheae 10,11 that conveying is mixed with the air-flow of particulate is dispersed into newly-generated fiber a fluid stream haply with these particulates and spreads on the direction.

As mentioned above, on the path of the air-flow process that is mixed with particulate, can establish a liner, if necessary, change air-flow and make Particle Distribution on the whole width of transport unit.This layout does not have shown in Figure 1.

We will be understood that, the ideal distribution that is collected in particulate in the fiber 9 on the transport unit is that requirement is blown the air-flow that carries particulate and mixed equably with newly-generated fiber a fluid stream.Both having made is to have carried out certain mixing in fiber laydown before transport unit, and the common deficiency of such mixing is so that product reaches even fully.

This traditional layout, promptly production line is limited to three whizzers and two particulates mix a little, and its product is shown in Fig. 3 a.The cross section of felt thickness has a series of tangible levels.Particulate between two middle layers 12 and 13 (for mapping conveniently increases the weight of to draw) in fact exists with higher ratio.

Although layer separates fully with layer is unlikely, it is uneven distributing, and this cause specific makes the quantity of particulate be restricted, and the amount of the particulate that mixes in any part of felt must not surpass certain particulate loading boundary.

Should note; although appropriate means for example guider can obtain the lateral distribution of satisfied particulate; but to improving the distribution of particulate on the felt thickness direction is helpless; be easy to find out that resulting distribution is owing to lack fiber/particulate blended consistence on the transport unit traffic direction.The mainly newly-generated fiber of the material that pile up in certain zone (under whizzer), and then be another zone height that wherein ratio of particulate is suitable again (particulate mix a little under), be the quite low zone of another particulate ratio successively, like that.

For obtaining good distribution, solution of the present invention is illustrated according to Fig. 2.

The building mortion of fiber is more detailed than Fig. 1 among this figure.The sketch 14 that mainly comprises a cover motor unit component among the figure is by tubular shaft 15 of belt transmission.The whizzer 16 that is contained in these root tubular shaft 15 1 ends is made of the cylinder that an outer wall is installed with a large amount of eyelets.

The mineral substance of fusing is directed into till the vertical axis of axle 15.Flow through the mould of the mineral material of fusing in whizzer 16.Mineral material is collected by a jar that is installed on axle 15 axial lines, is transported to the circumferential wall of whizzer again from jar, and comes out with the loss of filament shape the eyelet from wall.

In order to make fiber-forming, adopt the whole bag of tricks to keep the material of whizzer and fusing all in suitable temperature.Therefore, be favourable with inductive method heating whizzer (perhaps heat its underpart at least, be subjected to rapid cooling) because of its underpart contacts with ambient air.An inductance loop 17 has been shown among Fig. 2.

The filament of stretching from whizzer blows by annular steam and carries.This annular steam is pyritous preferably.Annular steam is made of the combustion exhaust that a ring nozzle 18 ejects.

In the mechanism of this form, the air-flow that additional gas injection stream big envelope commonly used attenuates fiber.For example these gas injection streams can be launched from encircling 19.Ring 19 is connected with the gas of certain pressure and a round is housed consistent with the direction that the air-flow that fiber is attenuated is propagated haply by the gas injection flow path direction.

The fiber of being taken out of by the air-flow that fiber is attenuated forms a curtain 20, and the characteristic front of curtain had been done description.

With fiber blow be loaded onto collection device air-flow in most of the cases by around air-flow, being arranged to annular shower nozzle 21 cooling of spraying water.The quantity of shower nozzle is abundant and abut against together to guarantee that fiber obtains even processing.

In addition, spraying a kind of binding agent around the shower nozzle 22 that blows the air-flow that carries fiber on fiber can be bonded together securely with the fiber of weave in the felt that guarantees formation subsequently.

Merit attention, in traditional fibrous nits mixed mode this bonding, particulate was directly sprayed binding agent.Result's these particulates in felt can not adhere on the newly-generated fiber like that securely.This is a factor that weakens last felt material mechanical property greatly.Particularly, be present in the blending in of fibers body, needn't prevent that applicable to these felt materials the compression ratio that these felt materials return to its original thickness from will reduce if so be difficult for the adherent particulate.

According to technology of the present invention, the vantage point that mixes particulate be located at the fibre curtain contraction place or herein on, as shown in Figure 2.So just the particulate that mixes advantageously is limited in the upstream of jet binder, fiber grain also is coated with binding agent as a result, thereby has increased the clinging power with newly-generated fiber.

Particulate is blown to carry by air-flow from a pipeline 23 and is transported to fibre curtain, and Fig. 2 only shows the end of pipeline.

Blowing the air communication of carrying particulate crosses tracheae 23 and laterally enters the path that fibre curtain is carried out.

Blowing make fiber air-flow that attenuates and the various characteristics (speed, intensity or the impulse force of saying so better) that blows the air-flow that carries particulate that carry fiber is defined as allowing the latter pass the former.

Blow the air-flow that carries particulate and penetrate and be accompanied by a kind of " blast " in the air-flow that fiber is attenuated, this blast projects particulate to spread all in the whole air-flow that blows year fiber.The mechanism that this diffusion form takes place is unclear fully as yet at present, just know because aforementioned region is very strong vortex position, blow passing of year particulate flow and only can increase the weight of the vortex disturbance and promote two bursts of air-flows mixing and promotion particulate in these mixed airflows, to scatter.

Usually, being used for blowing the air-flow that carries particulate will flow with certain speed, and purpose is to prevent to form " tamper " in tracheae.The path that particulate passes through is in fact usually quite long and will pass through some turnings, if the impellent of particulate operation is big inadequately, these factors just cause irregular operating troubles easily.

Here point out that the distance of particulate process can surpass 100 meters, especially if with the particulate of cutting edge and making, cut edge and operate, grind and cut edge and pass back to collecting chamber and can carry out continuously in the end of production line easily, production line is extensible quite long usually.

Can prevent to form tamper or cause size usually in the gas velocity on the heavy edge of 10 to 20 millimeters particulate in 15 to 30 meter per second scopes, with better at 20 to 25 meter per seconds.

Blow the air-flow that carries fiber and don't pass completely through particulate flow I in order to make air-flow intermingling satisfactorily, just mean the air-flow that blows year particulate fully to penetrate _pWith the ratio of the impulse force of fibrous airstream If be favourable in the scope of 1/30-1/5, preferably about 1/10.

The impulse force definition expression formula of air-flow is as follows:

I＝ ·V ²·S

Wherein:

Quality (kilogram/the rice of expression air-flow unit volume ³)

V represents the speed (meter per second) of air-flow

S represents sectional area (rice ²)

Blowing the size of the tracheae 23 that carries particulate will decide according to the situation of particulate.The cross-sectional area of tracheae should make particulate unblocked.Here point out, for the mean sizes size in the particulate of 15-20 millimeter and speed under the situation of 20 meter per seconds, diameter of section is got 80 millimeter and is advisable.

Diameter is too small can to increase the danger of blocking, unless increase the speed of air-flow simultaneously.Similarly, diameter is crossed conference because keep conveying finely divided required speed to cause that airshed strengthens.Latter event causes increasing energy expenditure again less than technological improvement.In addition, with respect to blowing the air-flow that carries fiber, excessive air-flow is easily upset the balance of relevant impulse force defined above.

Be noted that since diameter in 80 millimeter owing to transport with pressurized air, the air strength of blowing year particulate is more many greatly than the requirement of accurate calculation.

Reach the condition of the particulate that mixes heavy body, the content that also just equals particulate in every cubic metre air-flow reaches 0.25 kilogram, and this remains a very little numerical value.

Leave the problem of tracheae desired size and do not talk, such transported pneumatically is easy to transmit the bigger material amount that contains, and its order of magnitude reaches 1 kilogram/meter ³Perhaps higher.

As an application example of the present invention, mixing in the manner described above of fibrous nits carried out on the production line that the fiber-forming device is housed, as shown in Figure 2.

Each whizzer is produced 20 tons of glass fibre every day.This heat-insulating material is by superfine fibrous (per 5 gram micronaire values are 3.0).

Find by experience, the fiber influence of the fine felt wood property particulate that can be mixed more is just responsive more.Therefore, in order to obtain comprehensive conclusion, select to test to mixing the most responsive product of particulate.

At first, product that is to say that under best operational condition, the total amount of adding is no more than 4% of institute's felt at the most with the side cut of recycling crushing under the condition of routine.This first the test in, particulate adds between two whizzers, as shown in Figure 1.

The weight per unit area of made fibrefelt is 850 gram/rice ³, unit weight is 9.48 kilograms/meter ³, thickness is 140 millimeters before compression and storage.

The felt material compresses with 4/1 compression ratio, and this ratio means that the thickness of felt material compression is no more than 35 millimeters.Measure afterwards its caliper recovery amount through compressing like this and storing 60 days.

Still adopt traditional method to mix fibrous nits, find when the comminution goods ratio of adding other source increases, all the other conditions are constant, and the recovery of thickness significantly disappears after storing, this proof resistance to compression pression disappearance (elasticity is poor).

Here point out, when the particulate that mixes recycling (ground is cut edge and the particulate in other source) accounts for felt body total amount ratio and reaches 10%, reclaim the goods of cutting edge and compare thickness and reduce 7-8% with only containing.When the ratio of particulate is 14%, reduce to reach 12%.

The examination and test of products shows that shown in Fig. 3 a, the distribution of particulate on the thickness of product is very uneven.

The quality of felt material that has been appreciated that this bad distribution influence, the high more influence of the ratio of particulate in the felt material is just serious more., show on performance and obviously do not improve by the fibrous felt material of new life with mix the cut edge felt material of (its total amount be plate body 4%) of ground again by more fully.Particularly the amount of recovery to thickness has no significant effect.

The test of under condition of the present invention the particulate of different ratios being carried out obtains on the thickness Particle Distribution product quite uniformly, shown in Fig. 3 b.

In Fig. 3 a and Fig. 3 b, the distribution of particulate 24 shows as the form that can see.In fact, when the fibrous nits that mixes is during by similar above-mentioned explained hereafter, cut edge or waste product no matter particulate derives from, the difference between fiber and the particulate is imperceptible.Its difference has only the testing fiber structure just can find out.In fact, the fiber that constitutes these microgranular textures has been coated with binding agent earlier, so just can cause that color has slight variation (used tackiness agent can make fading of fiber).

The change of Particle Distribution is reflected on the caliper recovery amount, particularly when the content of particulate is high.This is with to adopt traditional particulate to mix mode gained result on the contrary, the amount of recovery of thickness in fact for content meet or exceed felt material amount 10% with unaffected.

The felt material of fine-fibered (per 5 gram micronaire values are 3.0) mixed 4% the particulate that gets by side cut with 7% by others come but the identical particulate of character, caliper recovery amount very little (about 4%) as a result.

When making the goods of the traditional method that is equivalent to extremely to be widely used in thermal insulation material with the fiber of not too thin (per 5 gram micronaire values 3.5 or even more preferably 4.0), in fact the little decrease of this caliper recovery amount is difficult to aware, for these products, the ratio of particulate can meet or exceed 15%.

From these results, proved that manufacturing proposed by the invention contains particulate at high proportion and keeps satisfied performance and the felt wood property can not had the possibility of dysgenic mineral fibre felt.Furthermore, for intention is as the product of thermal insulation material basically, the present invention points out emphatically the particulate ratio of mixing according to the present invention can not have materially affect to the heat conductivity of made felt up to 15%.

Claims (9)

1, a kind of method of operating mine fibres felt is to form fiber by the material that melts by foraminous whizzer on the circumference, molten material these eyelets by whizzer eject and become ultimate fibre, one air-flow that comes out along the whizzer circumference blows ultimate fibre and carries and it is attenuated, the original ringwise gas of this strand flows to and shrinks the air-flow that has formed taper below the whizzer, blow the fiber that carries by air-flow and be blown to a collecting conveyor and collection there, transporting in the process between from the whizzer to the transport unit will be sprayed a kind of tackiness agent on fiber, simultaneously, fibrous nits also is impregnated in, fall on the transport unit with the fiber of new generation, fibrous nits mixes mutually with the new fiber that produces, the fibrous nits that mixes is blown by air-flow and carries, the direction that it is characterized in that this air-flow is inequality with the direction of blowing the air-flow that carries the new fiber that produces, and and one air-flow of back at whizzer and blow between the air-flow punctured position that carries fiber a bit on converge, the above-mentioned fibrous nits that is impregnated in is the side cut from the fibrefelt of being produced on the production line.

2, in accordance with the method for claim 1, it is characterized in that the flow direction and the vertical line that blow the air-flow that carries particulate intersect at least 30 ° of angles, that is to say, intersect at least 30 ° of angles with the flow direction that blows the air-flow that carries fiber.

3, according to claim 1 or 2 described methods, it is consistent with the transport unit length direction to it is characterized in that blowing the air flow line that carries particulate.

4,, it is characterized in that blowing the gas velocity of year particulate in 15-20 meter per second scope according to the described method of above-mentioned every claim.

5, according to the described method of above-mentioned every claim, it is characterized in that blowing the air-flow that carries particulate and blow impulse force between the air-flow that carries fiber than Ip/If in the 1/30-1/5 scope.

6, in accordance with the method for claim 5, it is characterized in that ratio I p/If is 1/10.

7,, it is characterized in that the admixture particulate is to carry out in the section front of fiber coating tackiness agent in the air-flow that carries fiber toward blowing according to the described method of above-mentioned every claim.

8, according to above-mentioned every in the described method of any one claim, the ratio of contained fibrous nits is equal to or greater than 10% in the fibrefelt that it is characterized in that being produced.

9, according to above-mentioned every in the fibrefelt produced of the described method of any one claim.

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