AU674922B2

AU674922B2 - Method and apparatus for introducing a substance into a fibre material, particularly into a mineral fibre material

Info

Publication number: AU674922B2
Application number: AU58338/94A
Authority: AU
Inventors: Hans Furtak; Frederic Lankar
Original assignee: Saint Gobain Isover SA France
Current assignee: Saint Gobain Isover SA France
Priority date: 1993-12-21
Filing date: 1993-12-21
Publication date: 1997-01-16
Anticipated expiration: 2013-12-21
Also published as: AU5833894A; JPH08510518A; ZA949049B

Description

Method and Apparatus for Introducing a Substance into a Fibre Material, Particularly into a Mineral Fibre Material

The invention concerns a method for introducing a substance into a fibre material, particularly into a mineral fibre material according to the generic portions of claims 1 and 3, respectively, and an apparatus suited for carrying out the method according to the generic portion of claim 14.

Frequently it will be necessary to introduce substances into a mat or fibre material, such as in particular a mineral fibre material for thermal insulation purposes. The substance may be introduced with regard to va- rious objectives. It may be a substance for the protection of the fibres. It may furthermore be a binding agent, in particular for producing a fibre material for insulation purposes. Although the invention may also be applied for introducing other substances than binding agents, this specification primarily gives an explanation for the case of introducing a binding agent into a mineral fibre material, particularly a fibre material for thermal insulation purposes.

In such a case it is desirable to achieve homogeneous introduction and distribution of the binding agent, namely a homogeneous distribution on points of contact between fibres, i.e. intersections between the mineral fibres constituting the fibre material.

Homogeneous deposition ensures good internal cohesion of the final product and improved mechanical properties, in particular elastic rebound following compression in order to regain the thermal insulating performance of the product.

Various methods disclosed in the prior art allow the introduction of a binding agent. Here it should be noted that the fibre materials are formed from mineral fibres which are usually obtained in a fiberisation process applying either internal or external centrifuging methods.

Fiberisation by means of internal centrifuging methods consists of supplying the material to be fiberised, while in a molten state, into the centre of a spinner or fiberisation rotor comprising a multitude of openings or perforations at its periphery, where filaments are formed. These filaments are subsequently attenuated by a high-velocity gas flow and deposited as solidified fibres on a production conveyor.

In fiberisation by means of external centrifuging methods, the material to be fiberised is supplied, while in a molten state, to the outer periphery of a fiberising wheel from which it detaches itself under the influence of centrifugal forces and forms filaments. Gas streams again contribute to attenuating the filaments which are eventually deposited on a production conveyor as solidified fibres.

In fiberisation by means of internal centrifuging methods, the binding agent is as a general rule sprayed onto the fibres on their trajectory before deposition on the production conveyor.

US-A-2 931 422 discloses such a kind of spraying operation. The binding agent, generally an organic polymer, is atomised by means of a device positioned in the centre of the fibre torus formed underneath the spinner.

One embodiment given as an alternative consists of removing the atomising operation into the range outside of the fibre torus formed underneath the spinner, to thus carry out atomising of the binding agent outside the torus.

One disadvantage of atomising techniques is their taking place in a zone of very high temperature. The high temperature involved brings about the beginning of binding agent polymerisation. This phenomenon is the cause of the fibres clinging to each other, which is not desired at this stage of production as it results in excessively dense fibre materials of inhomogeneous structure. Application of high temperatures furthermore favours conditions for volatilisation of the binding agent.

The teaching of US-A-3 901 675 permits to avoid this disadvantage by cooling down the fibres by applying a cooling agent before binding agent is supplied. This avoids premature polymerisation of the binding agent as well as the risk of volatile binding agent escaping into the atmosphere. Additional use of a cooling agent, however, may complicate the process and increases production costs.

Other disadvantages particular to this atomising technique concern the strands or bunches of fibres formed when the fibres become entangled in the turbulent flows above the production conveyor. It can actually be seen that frequently the binding agent either fails to deposit on the fibres forming such strands, or an excessive application will occur, i.e. an excessive amount of binding agent deposits on the strands. In either case, the results of introducing the binding agent are consequently not satisfactory.

US-A-2 936 479 discloses another manner of introducing the binding agent wherein the latter is continuously introduced between the fibres in a powder form before their deposition on the production conveyor. The results obtained by this process are less favourable with regard to homogeneity and show the same disadvantages as the methods cited above.

The above techniques, on the other hand, imply a loss of the substance, e.g. binding agent, due to incomplete deposition on the fibres.

The loss, in the case of binding agent, amounts to 20% of the atomised binding agent. This constitutes a direct economical disadvantage through loss of the substance.

Furthermore, binding agent which was not adhered by the fibres is evacuated through the perforated production conveyor and therefore contained in the production exhaust gas. The filter systems thus necessitated in order to avoid emission of the substance into the environ¬ ment require additional expenditure. In practical terms, the amount of production exhaust gas to be purified is in the range of 50,000 m^/h per centrifugal machine, such that an increased contamination results in considerable additional costs.

In the case of fiberisation by means of external fiberisation methods, too, the binding agent is generally applied by atomising.

EP-0 059 152 discloses such a process wherein a binding agent is ap¬ plied on the fibres before they arrive at the production conveyor. For this purpose, the binding agent is flung onto the fibres by centrifuging.

The problems encountered here are essentially identical to those occurring in internal centrifuging methods. In particular, considerable losses of binding agent are inevitable here, too.

The invention has the objective to provide a method and a device by which a substance, e.g. a binding agent, may be deposited in a fibre material with good homogeneity, with the risk of wasting part of the substance being concurrently reduced.

In terms of process technology, this objective is attained according to the invention by the characterising features of claims 1 and 3, respectively.

The method according to the invention of depositing a substance or a mixture of substances in a fibre mat, in particular in a mineral fibre material, allows to make the substance penetrate the fibre material or to transport it through the fibre material while in a gaseous form, and to simultaneously de¬ posit the substance on the fibres within the fibre material in a very homoge¬ neously distributed and well controlled manner by condensation.

Due to introduction of the substance into the fibre material while in gaseous form, it is provided in uniform distribution inside the fibre material.

Condensation from this uniform distribution of the gaseous substance ensues in locations where fibres are present, such that maximum ho¬ mogeneity of the precipitation by condensation is ensured.

As the substance, or a corresponding precursor product thereof which eventually is transformed into the substance, is not provided together with large quantities of exhaust gas to be disposed of, recovering the substance or its precursor material to the extent it is not precipitated on the fibres does not pose any problems. In the simplest case, the substance emanating from the fibre material may be redirected to the supply of substance in the condensed state and may again be transformed into the gaseous phase together with it. In this way, losses or waste of the substance may be eliminated altogether.

Condensation on the fibres of the fibre material occurs due to the circumstance that the fibres, which are relatively cooler than the substance, extract enough heat energy from the vapour in the vicinity of the respective fibres to induce precipitation according to the laws of condensation. The heat energy released during condensation in turn heats the fibres. As a result, the temperature difference available for condensation continuously diminishes, whereby less and less condensate may be obtained from the vapour flow until the condensation process ceases when a certain minimum temperature difference is not available any more. Thus the temperature dif¬ ference between the gaseous substance on the one hand and the fibre material on the other hand is instrumental for the amount of condensate that may be precipitated inside a certain volume of a certain fibre material.

If the substance to be introduced is a binding agent, its function is to bond or tack together fibres crossing each other at their points of intersection, or contact, whereas the fibre lengths between such points of contact may remain free of binding agent. In such a case it is accordingly of particular interest to use a binding agent which does not wet the fibre material and consequently forms droplets on its surface, and to preferably deposit the binding agent on the points of contact between the fibres.

This aim is achieved especially well with the present invention. The points of contact between the fibres form material agglomerations having an increased mass/surface ratio and therefore follow the temperature increase of the fibre material caused by condensation with some delay. The points of contact therefore appear to be preferred locations of condensation where, in a given case, a desired accumulation of binding agent occurs.

This process appears to be further supported by the fact that intersections or closely approaching portions of two fibres are preferred positions for a binding agent droplet, also from the viewpoint of minimising surface tension upon contact between both fibre surfaces. For this same reason, spontaneous positioning of binding agent droplets at the intersections between fibres approaching or contacting each other seems to be favoured.

When introducing other substances, e.g. for fibre protection, it may on the contrary be recommendable to use substances for wetting the fibre material which condense to form a film enveloping the fibres and thereby also wet the portions between intersections.

Instead of the vaporised substance to be deposited itself, for example the binding agent, a precursor material may also be utilised if this is recommendable for reasons of process management, or inevitable in case the substance itself does not lend itself for being transformed into a useful vaporous state.

The process may suitably be conducted such that preferably part of the substance is precipitated on the fibres of the fibre material by means of con¬ densation. As a result, a sufficient amount of remaining substance may remain in the vapour stream and be reintroduced into the process after flowing away, in order to guarantee good control or regulation of the process.

If the gaseous substance is at a temperature above its dew point temperature, a temperature drop to the dew point temperature must occur before condensation may start. In such a case, condensation is thus not possible immediately following penetration into the fibre material. Once the gaseous substance has cooled and the fibres located on the entry side of the fibre material have consequently been heated, condensation will also not be possible there due to the lack of a temperature difference with the fibres. It follows that if the substance is at a temperature above the dew point temperature, condensation inside the fibre material is only possible at a distance from the entry surface, such that the substance cannot be deposited in the zone adjacent the entry surface. As far as condensation occurs downstream of the entry surface, there is a danger of deposited sub¬ stance again being removed by a subsequent drying effect since the temperature of the inflowing gas is above the dew point temperature, and hence above the vaporisation temperature of the substance.

In accordance with claim 2, it is therefore preferred that according to one-component, multiple-phase thermodynamics, the temperature of the gaseous substance does not exceed the boiling/dewpoint temperature of the substance when brought into contact with the fibres, i.e. the temperature of the gaseous substance does not exceed the isotherm, pertaining to the existing pressure, between the boiling point and the dew point inside the two-phase area, with preferably close to 100% of the substance initially present in the two-phase area being in the form of vapour, and with the temperature of the fibre material in any event lying below the temperature of the vaporous substance. Thus it is ensured that condensation on the fibres takes place already after the first contact upon entry into the fibre material, without cooling of the gaseous substance to its dew point temperature having to be carried out beforehand.

A minor decrease in the temperature of the vaporous substance, which is at the dew point temperature at the time of entry, below this dew point temperature while flowing through the fibre material (possibly caused by minor pressure reduction due to throttling effects of the fibres) does not pose any problems as long as the temperature of the fibre material remains below that temperature of the vaporous substance which prevails at the location just attained.

If, according to claim 3, a polynary gaseous mixture is used for the pur- pose of introducing the gaseous substance (which in the following should al¬ ways be understood to encompass a possible precursor substance and/or a mixture of a plurality of individual substances), this may bring about advanta¬ ges in terms of process management. Maintaining a defined flow, for instance, is easier and safer in spite of decreasing volume by simultaneous condensation if a transport gas is used which, being an inert gas, remains unaffected by the condensation processes. Uniform distribution of the condensate at a greater distance from the entry surface is also facilitated by the flow of inert gas.

If the polynary gaseous mixture is at a temperature above its dew point temperature for the prevailing pressure and concentration, then a temperature drop to the dew point temperature must occur before condensation becomes possible. In such a case, condensation is thus not possible immediately following penetration into the fibre material. In order to lower the temperature of the gaseous mixture to the corresponding dew point temperature, heat must be extracted from the gaseous mixture. This is possible only if there is a temperature difference with the cooler fibres, however it means that the fibres positioned on the entry side of the fibre material are heated to the temperature of the gaseous mixture. Consequently, condensation will also not be possible there due to the lack of a temperature difference with the fibres and of any components having a temperature below the dew point temperature. It follows that in the case of a temperature of the gaseous mixture above the dew point temperature, condensation inside the fibre material is only possible at a distance from the entry surface of the gas, such that the substance cannot be deposited in the zone adjacent the entry surface. As far as condensation occurs downstream of the entry surface, there is a danger of deposited substance again being removed by a subsequent drying effect since the temperature of the in¬ flowing polynary gaseous mixture is above the dew point temperature, and hence above the vaporisation temperature of the substance.

According to claim 4, it is therefore preferred that in accordance with multiple-component, multiple-phase thermodynamics, the temperature of the polynary gaseous mixture does not exceed the initial dew point temperature of the polynary mixture in accordance with the composition of the mixture and with the pressure, present upon initial entry into the fibre material. In any case, the temperature of the fibre material should remain below the dew point temperature corresponding to the composition of the polynary gaseous mixture upon exit from the fibre material.

In a particularly preferred manner, the temperature of the polynary gaseous mixture according to claim 5 is in close vicinity of the initial dew point temperature of the polynary mixture. Hereby it is possible for the transport gas to carry into the fibre material a large amount of substance, as a large quantity of the substance is soluble in the transport gas in the vicinity of the initial dew point temperature. Moreover, this yields a maximum tem¬ perature difference between the temperature of the fibre material and the temperature of the polynary gaseous mixture without overheating the latter, and thus a maximum amount of substance that may be deposited.

In accordance with claim 6, the transport gas is saturated with the vapour of the substance, thus containing the maximum possible quantity of substance in the gaseous form at the given temperature or concentration.

According to claim 7, the transport gas, in a particularly preferred manner, is air. As air may be referred to as an inert gas inasmuch as it will not condense under the conditions in question, the use of air as a transport gas is inexpensive and quite considerably simplifies the process management.

In accordance with claim 8, the flow of the gaseous substance, or of the polynary gaseous mixture, is achieved by forced circulation or flow. In this manner, in contrast to naturally, thermally induced flow customarily presenting flow velocities around 1 mm/sec, well defined and reproducible flow characteristics may be achieved and maintained. According to need, higher flow velocities of 0.3 to 0.5 m/sec. may furthermore be used without problems, preferably however not in excess of 1 m/sec.

In accordance with claim 9, the precursor material used is a monomer which is polymerised in the course of deposition or after deposition in the fibre material. This is advantageous particularly in the case of using the substance as a binding agent, as the binding agent as a rule is an organic composition of high molecular weight incapable of being transformed into a useful gaseous phase. In this manner, use of the invention is thus available for deposition of the binding agent by means of the method according to the invention, even though the binding agent itself is not suited for treatment by the process of the invention.

In accordance with claim 10, deposition of the substance in the fibre material is carried out while the latter is still present on the production conveyor. This means that introduction of the gas must be carried out on a fibre material moved past the location of treatment, before curing is achieved e.g. in the curing oven. Here care should be taken to correlate the length of the treatment zone with the movement velocity of the fibre material and the flow velocity of the gas in such a way that the entire height or thickness of the fibre material may be penetrated, with condensate formed before the fibre material leaves the treatment zone where it is exposed to the gas flow. Where insufficient production speeds result from low gas velocities and/or large product thicknesses, this may be counteracted by extending the length of the treatment zone.

Mineral wool material intended for producing shaped articles, such as pipe sections, may also be treated on the production conveyor in this manner, must however be given the desired shape before the binding agent is cured, which, as a rule, is not possible on the production conveyor. In many cases, the continuous production process of fabricating shaped articles is accordingly interrupted before the curing oven; the wool material is transported to a different facility for producing the shaped articles and correspondingly processed there. This may be done with raw material al¬ ready provided with binding agent - even in the case of long periods of time passing before curing.

In such a case, however, it is preferred according to claim 11 to take the raw material to the facility of its further processing without binding agent, and only there provide it with binding agent. This may be done according to the invention in that the raw material parts intended for production of the shaped articles are exposed to the gas flow while at rest, with the substance being condensed. On the one hand, this yields the advantage of low fibre temperatures prevailing due to a long delay after fibre production, such that a low fibre temperature and thus a large difference with the gas temperature may be generated without any additional expense. On the other hand, there results an advantage because of the easier process management of a flow through the fibre material while at rest. If necessary, therefore, a very large amount of substance may in this manner be introduced into the fibre material intended for producing shaped articles.

In accordance with claim 12, it may be advantageous to reverse the sense of flow penetrating into the fibre material, if possible repeatably. Hereby both large surfaces of the fibre material may be exposed to fresh vapour and thus wetted rapidly and intensely by condensation. Contrary to a flow in only one direction, whereby initially drastically reduced amounts of vapour or a considerably impoverished gas mixture reach the area of the opposite surface of the fibre material until the heating of upstream fibre material suppresses condensation there, further improved homogenisation of the deposition of substance over the height or thickness of the fibre material may be achieved hereby whenever necessary. Furthermore accelerated penetration may be achieved in that the gaseous substance, i.e. the vapour, need not be passed over the entire height or thickness of the fibre material from one side in order to also deposit the substance in the region of the opposite surface, but relatively short surges of vapour from both sides may be sufficient. This is particularly true if the substance to be deposited, in accordance with its characteristics, should be concentrated especially at or close to the large surfaces while the same concentration thereof is not required in the centre of the fibre material.

According to claim 13, an additional treatment is provided between at least single ones of these reversions. Hereby the fibre material, which was inevitably heated during condensation of the substance, may advantageously be re-cooled in order to maintain a maximum possible temperature difference between the vaporous substance, or polynary gaseous mixture, and the fibre material.

In terms of apparatus technology, this objective is attained by the cha¬ racterising features of claim 14. Accordingly, a binary gaseous air/substance mixture is produced in sa¬ turated condition in a first device, this mixture subsequently being directed to the fibre material and introduced into it in another device.

Subclaims 15 to 19 deal with advantageous improvements of the apparatus of the invention.

Further details, features and advantages of the invention are given in the following explanation of an embodiment by making reference to the drawing, wherein:

Fig. 1 shows a schematically simplified representation of an installation illustrating the process sequence in the production of a polynary gaseous mixture and its introduction into the fibre material from one side thereof, and in recovering the substance downstream of the fibre material;

Fig. 2 in a representation similar to Fig. 1 shows the introduction of a polynary gaseous mixture into the fibre material from both sides, as well as recovering the substance from both sides downstream of the fibre material;

Fig. 3 in a representation similar to Fig. 1 and 2 shows an installation comprising an additional treatment device between two treatment stations;

Fig. 4 a Pv diagramme illustrating PvT behaviour of a pure substance; and

Fig. 5 a phase balance diagramme describing the Tx(y) behaviour of a two-component, two-phase mixture.

In the exemplary case illustrated in Figs. 1 to 3, a binding agent in the form of a monomer as a precursor material is to be introduced into a mineral fibre material and to be condensed on the fibres of the fibre material. A vessel 1 has a lower portion 1 a containing a liquid monomer 2 which passes, by means of a pump 3 located downstream of the vessel 1 , through a subsequent heat exchanger 4.

The heat exchanger 4 is provided with an inlet 5 at its downstream end in the sense of flow of the monomer 2, and at its upstream end with an outlet 6 for a heat transferring fluid 7 which arrives from a steam boiler 7a, or is heated by a heating device 7a.

Downstream of the heat exchanger 4 in the sense of flow of the monomer 2, a Venturi ejector 8 is provided whose outlet region 8a opens into a conduit 9 leading to an upper portion 1 b of vessel 1. Furthermore a suction conduit 10 for sucking in air 11 opens to the outlet region 8a of the Venturi ejector 8 at the point of lowest pressure and thus of the strongest suction effect. *

Vessel 1 , pump 3, heat exchanger 4, Venturi ejector 8 and conduit 9 form a first circuit A for the monomer 2.

A separator 12 is arranged in an upper outlet 13 of vessel 1 , whereby a gaseous mixture 14 leaves vessel 1. The gaseous mixture 14 is air 11 saturated with monomer vapour.

Downstream of separator 12, the upper outlet 13 of vessel 1 opens into a conduit 15 conveying the gaseous mixture 14 to a treatment station 16 for a fibre material 17 with a velocity defined by the pump 3 for circulation of the monomer.

The treatment station 16 essentially consists of an inlet 18 for the gase- ous mixture 14 supplied through conduit 15, a support 19 for fibre material 17, and an exhaust 20 which is provided with an outer thermal insulation 21. The support 19 comprises a support surface 19a on which fibre material 17 rests, and through which the gaseous mixture 14 can flow, and a gas- impermeable surface 19b surrounding support surface 19a in order to prevent short-circuit flow of the gas by circumvention of the fibre material. The gaseous mixture 14 crosses through the fibre material 17 due to forced flow or circulation, and upon contact with the fibres during its passage the gaseous monomer 2 condenses as a result of the temperature difference between the gaseous mixture 14 and the fibre material 17.

Upon leaving the fibre material 17, the gaseous mixture impoverished in monomer vapour is recovered in the exhaust 20 and conveyed to vessel 1 through a conduit 22. The thermal insulation 21 minimises heat losses in the exhaust 20 in order to prevent condensation of the gaseous monomer 2 on the inside of the exhaust 20 and thus prevent liquid monomer 2 from dripping onto the fibre material 17. Preferably, conduit 22 is inclined downward in the sense of the flow and connects exhaust 20 with suction conduit 10.

Upstream of the opening of conduit 22 into suction conduit 10 there is located a throttle device^' 23 in conduit 10. Throttle device 23 limits the intake and supply of air 11 to Venturi ejector 8 and thus serves to maintain a high degree of vacuum as desired in suction conduit 10.

Vessel 1 , separator 12, conduit 15, treatment station 16 with fibre material 17 on support 19, exhaust 20, conduit 22 and suction conduit 10 form a second circuit B for the gaseous mixture 14.

In order to support the effect exerted by pump 3 on the gaseous mixture 14, an additional ventilator may optionally be provided in conduit 15 or conduit 22, as it is shown in the drawing for conduit 22.

Fig. 4 shows a Pv-diagramme illustrating PvT behaviour of a pure sub¬ stance. The specific volume v and the system pressure P are plotted on the X-axis and the Y-axis, respectively. The dashed lines show isotherms T and Ten with status points A, B, C, D, and E being entered on one of these isotherms. Initially an isothermal compression of a gaseous substance, starting out from status point A, is being regarded. In point B, the two-phase area of gas and liquid is reached at dew line V, wherein the substance is present in liquid and vaporous forms. This two-phase area of gas and liquid is passed through at constant pressure. At point C, the system has entirely been transformed into the liquid state and reached the boiling line IV. By means of further isothermal compression, the two-phase area of liquid and solid body, referred to as a melting area, is reached in point D on the solidification line II. With the substance being present in liquid and solid forms, the melting area is also passed through at constant pressure until the system finally is entirely transformed into the solid state at point E on the melt line I. The boiling line and the dew line V meet in the critical point II associated with critical pressure P_Cr, critical specific volume v_cr, and the critical temperature T_Cr of the substance. The triple line VI separates the two-phase area of gas and liquid wherein the substance is present in liquid and vaporous forms, from the two-phase area of liquid and solid body wherein the substance is present in vaporous and solid forms.

If such a substance is to be introduced into the fibre material 17 in vapour form, the vapour should have conditions corresponding to status point B of Fig. 4, i.e. dew point conditions. In this way it is ensured that any cooling effect on the vapour will lead to instantaneous precipitation of condensate, with condensate precipitation continuing as long as the cooling effect continues. Also, any re-drying effect is avoided which otherwise would cause danger of precipitated condensate to be vapourised again upon contact with vapour at a temperature still above dew point temperature.

Fig. 5 shows a phase balance diagramme describing the Tx(y) behaviour of a two-component, two-phase mixture. The concentration x of one of the substances and the temperature T of the mixture are plotted on the X-axis and on the Y-axis, respectively. The diagramme is separated into three areas by the dew line VII and the boiling line VIII. In the area above dew line VII, the mixed constituents are both present in vaporous form. In the area between the dew line VII and the boiling line VIII, the constituents of the mixture may be present individually or as mixture in vaporous and liquid forms. In the area below the boiling line VIII, the mixed constituents are both present in liquid form.

The dew line VII, in accordance with temperature T and concentration x, describes a curve along which the gaseous mixture starts to condensate. Boiling line VIII accordingly describes, in accordance with temperature T and concentration x, a curve along which the liquid mixture begins to boil. Thus, if e.g. by temperature drop through withdrawal of heat, a gaseous mixture of a concentration x reaches point v on dew line VII, condensate of higher concentration x*ι corresponding to the isothermal point l_ι on boiling line VIII will precipitate, while simultaneously the remaining gaseous mixture will be reduced in concentration and, in view of simultaneous extraction of heat by the condensation, will follow dew line VII to finally reach point v' on dew line VII corresponding to a lower temperature T. At this temperature the condensate will have lower concentration x corresponding to point L on boiling line VIII, correspoding to the intitial concentration of gaseous mixture, and spontaneous condensation will stop with the remaining concentration of the gaseous mixture corresponding to x'.

In operation, the device according to the invention on the one hand serves to produce a binary gaseous mixture, namely air saturated with a monomer vapour, and on the other hand to transport the gaseous mixture to the fibre material 17, introduce it into the fibre material 17, and condense the monomer 2 on the fibres of fibre material 17, as well as to recover those con¬ densable constituents of the gaseous mixture which have not been condensed on the fibres of fibre material 17.

Through inlet 5, heat exchanger 4 is supplied with heat transferring fluid 7 such as hot water. The monomer 2, which is present at the entrance of heat exchanger 4 in a liquid state, is heated to a high temperature by its passage through heat exchanger 4, however not high enough to cause phase transition.

The heated, liquid monomer 2 leaves heat exchanger 4 and flows to the Venturi ejector 8 where it is atomised into minute droplets which evaporate and saturate the air 11 sucked in through suction conduit 10.

The separator 12 is arranged at the upper outlet 13 of vessel 1 and permits separation of unevaporated or condensed droplets into vessel 1. In this way, a gaseous mixture 14 without a liquid content is obtained. In the example given, this gaseous mixture 14 is air 11 saturated with monomer vapour.

The gaseous mixture 14 is subsequently transported through conduit 15 to processing station 16. This is effected at a velocity defined by pump 3 for the circulation of the monomer 2.

To this end, pump 3 in circuit A generates a vacuum in suction conduit

10 by means of the Venturi ejector 8 and causes a sufficient amount of air 11 to be induced. Suitable throttling of the air intake by throttle device 23 in suction conduit 10 causes the vacuum within suction conduit 10 to support circulation of the gaseous mixture 14 in circuit B.

At the treatment station 16, the gaseous mixture 14 flows past inlet 18 and reaches fibre material 17 through support surface 19a of support 19, and then penetrates into fibre material 17 because of the forced circulation. The gaseous monomer condenses during the passage through fibre material 17 upon contact with the fibres which are at a temperature below the temperature of the gaseous mixture 14 and also below the dew point temperature of the monomer 2 as well as below the dew point temperature of the gaseous mixture 14.

After leaving fibre material 17, the gaseous mixture 14 impoverished in monomer vapour is sucked into exhaust 20 and conveyed back to be recovered by being admixed, through conduit 22, to the air 11 - induced through suction conduit 10. A suitable design of conduit 22 safeguards against any tendency of monomer condensed there to flow back to fibre material 17, but ensures its flow to vessel 1.

When admixing the impoverished gaseous mixture 14 to the cold air

11 , the resulting cooled gaseous mixture may be excessively saturated with the vapour of monomer 2 at such low temperature. This brings about condensation of parts of monomer 2 which are then recovered in vessel 1 like condensate flowing out of conduit 22. Atomisation and evaporation at outlet 8a of Venturi ejector 8 may be controlled to result in a temperature increase based on heat induction from the heat energy of monomer 2 present at Venturi ejector 8. Hereby circuit B is supplied with heat which raises the temperature of the gaseous mixture 14 so produced to or above its dew point temperature. If necessary, the energy balance may be influenced by pre-heating the air 11.

The apparatus accordingly permits introduction of monomer 2 into fibre material 17 without any losses of input constituents, as vapour of monomer 2 not condensed inside fibre material 17 is fully recovered. Heated, liquid monomer 2 inside the circuit A which failed to evaporate upon passage through the Venturi ejector 8, and monomer 2 condensed downstream of fibre material 17 are recovered in vessel 1 by means of separator 12 and supplied for renewed heating in heat exchanger 4.

The condensed portion of the monomer constantly withdraws gas or vo¬ lume from circuit B, which volume is compensated by the aspired volume of air 11. The induced air 11 in turn forms fresh gaseous mixture 14 together with fresh monomer 2 evaporated at Venturi ejector 8.

As regards production of a gaseous mixture 14 saturated with the monomer vapour at a predetermined temperature, knowledge of all relevant data of the components used is necessary.

If the operational parameters of Venturi ejector 8 are known as well as the flow rates of air 11 and liquid monomer 2, initial data concerning air 11 and monomer 2, plus densities, input and output temperatures, specific heats, vapour tensions and evaporation temperatures, furthermore the heat transport capacity of the heat transport fluid 7 inside heat exchanger 4, then it is possible, by applying the laws of thermodynamics, to determine the input temperature of the heated, liquid monomer 2 into the Venturi ejector 8, which is necessary to saturate the air 11 with the vapour of the monomer 2 at a selected temperature.

Where necessary in a given case, an additional temperature adjustment may be carried out in a manner which is not represented, however conventional, e.g. through a heat exchanger in the upper portion 1 b of vessel 1 or somewhere along conduit 15. In this way it is possible in any individual case to adjust the temperature of the gas mixture 14 such that it will present a desired temperature, such as particularly the temperature corresponding to its dew point temperature, in the region of inlet 18.

The support 19 for the fibre material 17 may consist of a production conveyor of the production facility for fibre material 17, which then is in uniform, uninterrupted movement in a direction perpendicular to the plane of drawing. The support 19 may, however, also be stationary, or at rest, such as in order to treat pieces of raw material for shaped articles.

As described above, Fig. 1 represents introduction into a stationary fibre material in circuit B.^' With respect to circuit A, Figs. 2 and 3 correspond to the representation in Fig. 1 , while with respect to circuit B different embodiments are shown. To facilitate the understanding, the same reference numerals as in Fig. 1 are used in Fig. 2 and 3 for identical or equivalent items.

In Fig. 2, the fibre material 17 in the form of an endless web passes through a treatment housing 30 containing two foraminous conveyors 31 supporting the web of fibre material 17 during its travel within housing 30. Between the flights of conveyors 31 is arranged a treatment casing 32 containing two successive treatment chambers 33 and 34. Treatment chambers 33 and 34 take up the traveling web of fibre material 17 in a substantially gastight manner so as to avoid excessive exchange of gases between inside and outside of the treatment chambers 33 and 34; this substantially gastight seal is supported by a corresponding sealing arrangement also of the lateral walls of treatment housing 30, as can be seen from the drawings.

Conduit 15a branched off from conduit 15 and conduit 22a branched off from conduit 22 open into first treatment chamber 33 so as to introduce the polynary gaseous mixture from conduit 15 to the lower side of the web of fibre material 17, and to exhaust the gas emanating from the upper side of the fibre material 17 into conduit 22, respectively. Conduit 15b branched off from conduit 15 and conduit 22b branched off from conduit 22 open into second treatment chamber 34 so as to introduce the polynary gaseous mixture from conduit 15 to the upper side of the web of fibre material 17, and to exhaust the gas emanating from the lower side of the fibre material 17 into conduit 22, respectively. The direction of gas flow through the fibre material 17 in treatment chambers 33 and 34 is shown by arrows 35 and 36, respectively.

The arrangement of Fig. 2 allows to effect alternating flow through the fibre material 17 in both directions so as to achieve the advantages, like improved homogenisation, associated therewith.

In Fig. 3, two treatment housings 30 are successively arranged along the way of travel of the web of fibre material 17, with an additional and special treatment housing 24 in between. In special treatment housing 24 any desired special treatment may be effected, including an intermediate cooling treatment between treatment housings 30 so as to avoid continued warming up of the fibre material 17 while passing through successive treatment housings 30. The arrangement within special treatment housing 24 is similar to the arrangement within treatment housings 30, as can be seen in Fig. 3. As schematically illustrated in Fig. 3, cooling gas conduits 37 open above and below the web of fibre material 17 so as to effect alternating throughflow of cooling gas according to arrows 38 and 39 through the fibre material 17.

The following is a presentation of the results of experiments, which were carried out on a stationary mineral fibre material 17 in order to facilitate interpretation of the results. Example 1 :

Deposition of the DCPOEMA (dicyclo-pentenyloxy-ethylmethacrylate) in its vaporous phase inside a fibrous material already containing ammonium persulfate as a catalyst. Cross-linking is then achieved by applying heat.

The primary fibre material was produced on an experimental pilot line and the ammonium persulfate, a water soluble solid, was sprayed on the fibres in traditional manner in aqueous solution by means of a spray crown, in a ratio of 1.5%.

The fibre material was subsequently cut to sample size (750 * 750 mm) and penetrated by two-component air/monomer mixture on the statically operating pilot installation, with the vaporous DCPOEMA monomer impregnating the fibre material by condensating on the fibres according to the invention. As the normal boiling point of the monomer is very high (350°C at 1 atm), saturating the air at 100°C (measured immediately before entry into the fibre material) with the vaporous monomer requires approx. 20 minutes.

The weight per unit area (gsm) of the fibre material lies between 500 and 600 g/nrι2 in all of the tests.

RESULTS

No. Introduction Mean dew point temperature Amount of condensate polymer¬ period during the test ised after introduction

(min.) CO (loss on ignition) (%)

1 2 98 9

2 5 103 23

3 5 100 18

4 10 106 34

5 10 110 40

The amount of condensate polymerised after introduction is evaluated in the following manner: The impregnated fibre material is kept inside the oven at 150°C for 15 minutes in order to allow cross-linking of the monomer.

The loss on ignition at 550°C is then measured on the finished product in the usual manner.

It is obvious that the deposited amount increases with the passage of time and with the dew point temperature.

The finished product presents a blackish colouring together with favourable cohesion and resilience.

Example 2:

A TMPTMA / Catalyst two-component mixture was introduced in vaporous phase into a fibre mateπal consisting of raw fibres, and subsequently the monomer was cross-linked by irradiation with an ultra¬ violet lamp.

TMPTMA is a tri-functional, methacrylic monomer (trimethylolpropane- trimethacrylate) also having a very high boiling point, namely 370°C.

The trade name of the catalyst is IRGACURE 369 (CIBA GEIGY). The chemical denomination is 2-beπzyl 2 dimethylamino 1-(4 morpholinophenyl)- butanone 1.

The catalyst, a solid substance, was dissolved in the monomer and the mixture deposited in vaporous phase inside the fibre material.

Here it should be noted that other than in the extensive method of pro¬ ducing mixture applied in the apparatus of Figs. 1 to 3, an air flow which was already sufficiently pre-heated is mixed with the hot, vaporous monomer in the upper section of a vessel. Thus pre-heating the air may be arranged more easily, and mixing the heated air with the vaporous monomer may correspondingly be realised with more ease. The monomer was introduced into the samples of a cylindrical fibre material (0: 9 cm) in vaporous phase at 90X (50 l/min.). This takes into account the experience that on the one hand, in-vessel polymerisation of the monomer may start already at temperatures above 90X, but that on the other hand, however, it is difficult to induce transition of the monomer into the vapour phase at temperatures below 90X. Consequently, at the selected temperature of 90X of the vaporous mixture it is still possible to satisfactorily generate the mixture from vaporous monomer and pre-heated air.

RESULTS:

Test Transport Introduction Introduction Amount of introduced con¬ gas period (min.) temperature densate (weighed before and CO after impregnation)

6 nitrogen 5 90°C 13.8

7 11.8

8 10.2

10 13.3

18 air 7.6

Introduction of the monomer with this experimental setup was carried out by means of two different transport gases, namely air and nitrogen. This provided an opportunity of examining whether air as a transport gas may inhibit polymerisation of the monomer under unfavourable conditions (pressure, temperature, mixing ratio) if polymerisation of the monomer is to be carried out by irradiation after its introduction. The study actually shows, however, that introduction by means of air as the transport gas may be carried out without eventually inhibiting polymerisation.

Use of an inert gas, i.e. nitrogen, may under certain circumstances be preferable in view of polymerisation of the monomer by irradiation after its introduction. Example 3:

In this example, lubricant Priplast 3018 (di-2-ethylhexyl-azelate) was tested. This material has an acid number of 0.5 mgKOH/g, an hydroxyl number of 3 mgKOH/g and a water content of 0.1 %. Furthermore, this material may be used down to a temperature minimum of -60 X, has a dynamic viscosity at 25 X of 16 mPa.s and of 3 mPa.s at 90 X, an ignition temperature above 210 X, a relativ densitiy 25/25 X of 0.92, and a refraction index N25/D of 1.448.

In the test with lubricant Priplast 3018 as the substance to be introduced which is to coat the fibre surfaces in order to finish them after condensation, the following results were obtained.

RESULTS

Test gsm Introduction Fibre tempe¬ Temperature of intro¬ Amount of introduc (g/m²) period rature (°C) duction into the fibre condensate (min.) material (°C) (weight %)

1 759 2x5 25 108 X- 111 1.4

2 826 2x5 25 114X-116X 1.3

3 846 2x5 25 115X-116X 0.8

4 855 2x5 25 117X-119X 0.8

5 886 2x5 25 117X-119X 0.7

6 821 2x2 25 116 X- 117 0.7

7 870 2x2 25 115X-116 0.25

8 924 2x2 25 114X-113X 0.33

9 805 2x2 25 114X-113X 0.75

The fibre material at rest with a mean weight per unit area (gsm) of approx. 850 g/m-2 was at a temperature of 25 X before introduction and penetrated by the mixture flow during 2 x 5, or 2 * 2 minutes. It is clearly recognisable that during an introduction period of 2 * 5 minutes at a mean introduction temperature of 116 X, or during an introduction period of 2 * 2 minutes at a mean introduction temperature of 114 X, an average of approx. 1 %, or 0.5 % of lubricant may be condensated. Here it is also evident that the introduceable amount may be increased with the passage of time and with the dew point temperature.

When scrutinizing the fibres under the microscope, a thin oil film may be perceived on the fibre surfaces. It is thus possible to intentionally coat fibres by application of the method according to the invention for the purpose of finishing or improving various physical or thermal properties.

Claims

1. A method for depositing a substance, or a mixture of substances, on fibres of a fibrous material, in particular of a mineral fibre material, wherein each substance, or a precursor material thereof, in gaseous state at a temperature above the temperature of the fibrous material is made to penetrate into the fibrous material, and preferably part of which is deposited on the fibres by condensation.

2. The method of claim 1 , wherein the gaseous substance, when bringing it into contact with the fibres of the fibrous material, is held at a temperature not exceeding the boiling temperature of the substance.

3. A method for depositing a substance, or a mixture of substances, on fibres of a fibrous material, in particular of a mineral wool material, wherein each substance, or a precursor material thereof, is mixed with a transport gas having a substantially lower dew point temperature than the substance, so as to form a polynary gaseous mixture, and wherein said polynary gaseous mixture is made to penetrate into the fibrous material, with the fibrous material being held at a temperature below the dew point temperature of said gaseous mixture, at least part of which is deposited on the fibers by condensation.

4. The method of claim 3, wherein the polynary gaseous mixture, when bringing it into contact with the fibres of the fibrous material, is held at a temperature not exceeding the initial dew point temperature of the mixture.

5. The method of claim 3 or 4, wherein the temperature of the polynary gaseous mixture is selected in close vicinity to the initial dew point temperature of the mixture.

6. The method of any one of claims 3 to 5, wherein the transport gas is saturated with the vapour of the substance.

7. The method of any one of claims 3 to 6, wherein air is used as trans¬ port gas.

8. The method of any one of claims 1 to 7, wherein the flow of the gase- ous substance, or of the polynary gaseous mixture, is effected by forced circulation or flow.

9. The method of any one of claims 1 to 8, wherein a monomeric gaseous precursor of the substance is polymerised, in the course of or after its deposition in the fibrous material, under the influence of a factor like heat, a catalytic substance, a radiation, another monomeric substance, or a gas.

10. The method of any one of claims 1 to 9, wherein the deposition is effected after the fibres forming the fibrous material have been received on a production conveyor, and while the fibrous material is still on the production conveyor.

11. The method of any one of claims 1 to 9, wherein in case of producing shaped articles like pipe sections the deposition is effected after the fibrous material has been removed from the production conveyor.

12. The method of any one of claims 1 to 11 , wherein the direction of the gas flow through the fibrous material is, possibly repeatedly, reversed after a predetermined period of flow in one direction.

13. The method of any one of claims 1 to 12, wherein between at least indi¬ vidual ones of the reversals there is provided additional treatment like cooling treatment.

14. An apparatus for the deposition of a substance on fibres of a mineral fibre material (17), wherein there is provided production equipment (circuit A) for a binary air/substance gas mixture with air as a transport gas saturated with vapour of a substance to be deposited, or of a pre- cursor thereof, at a given temperature, and equipment (circuit B) for directing the binary air/substance gas mixture to penetrate into said fibrous mateπal (17).

15. ^"The apparatus of claim 14, wherein said production equipment (circuit A) comprises

a heat exchanger (4) for heating the substance in its liquid state,

a pump (3) for pressurising the heated liquid substance towards the entrance section of a Venturi ejector (8), and

air (11) intake means (conduit 10) opening into the vacuum zone of said Venturi ejector (8) to form the binary air/substance gas mixture.

16. The apparatus of claims 14 or 15, wherein said equipment (circuit B) for directing comprises means to create a pressure differential across the fibrous material so as to cause the binary air/substance gas mixture to penetrate into said fibrous material (17) at a predetermined flow rate.

17. The apparatus of claim 16, wherein said means to create a pressure differential across said fibrous material (17) comprise a vacuum means in downstream direction behind said fibrous material (17).

18. The apparatus of claims 16 and 17, wherein said vacuum means com- prise said Venturi ejector (8).

19. The apparatus of any one of claims 14 to 18, wherein a filter means (12) is provided upstream of said fibrous material (17) so as to hold back any liquid substance above a certain particle size from being entrained with the binary air/substance mixture.