DE2235078A1 - Insulating sheeting with asbestos fibres - using air stream feed for fibres and combining with resin stream - Google Patents

Abstract

Designed to provide an insulating sheeting for construction applications, the asbestos fibres are delivered in an airstream, in a measured volume, to combine with the stream of resin in a reciprocating spray unit to be sprayed at 60 degrees at a carrier surface to give a number of stripes with overlapping edges which can be built up into an impregnated felting. The resin is a phenol/formaldehyde, an unsaturated polyester or silicone, starch or gelatine, a latex of natural and/or synthetic rubber, a bitumen or a solution of sodium silicate in water or a cement sludge. The purpose is to build up an even distribution of asbestos and resin, without the disadvantages of impregnating a felting.

Description

Process for Making Bonded Felts The invention relates to the production of bonded felts from asbestos fibers, such as resin-impregnated felts.

It has been known for many years to make insulation covers made from asbestos cement Form on walls or other surfaces by introducing a stream of asbestos fibers and cement is sprayed together with a water jet in such a way that the Mix currents before impinging on the surface. After drying, it works Cement as a binding agent and keeps the separated asbestos fibers permanently on the wall or other surface.

It is also well known to manufacture resin-bonded glass fiber felts according to a A process that enables the separation of the glass fibers, which together with - a - resin binder are sprayed on, comprises.

Although these two ways of working have been known for many years, includes the production of resin-bonded asbestos felts is still two separate main stages, namely the Making a felt from carded prepared respectively.

processed asbestos fibers and the impregnation of the felt with resin, usually in a bath of the # resin solution.

According to the present invention, for the production of a felt, containing essentially bound asbestos fibers, a spray of droplets a liquid binder and a jet of asbestos fibers with gas as the carrier medium sprayed as separate streams such that the streams intersect and mix before they hit a receiving surface as the only stream, where they are in be deposited in a controlled manner in order to form a uniform layer that is then removed from the receiving surface.

The liquid binder can be a solution, suspension or dispersion of a synthetic resin, such as a phenol / formaldehyde condensate, an unsaturated one Polyester, or a silicone, a liquid preparation of a natural polymer material such as starch or gelatin, an elastomer preparation, such as a solution or a Natural and / or synthetic rubber latex, bitumen-based preparation, an inorganic preparation such as an aqueous solution of sodium silicate or a cement slurry.

It may be necessary to add heat to ensure that The binder remains in liquid form at least until the streams mix and are placed on the receiving surface. This heat can be applied directly to the binder and / or the gas stream carrying the asbestos fibers.

The fibers are sprayed at the most uniform speed possible, to create a practically even and even coverage. The sprayed Streams of liquid binder and asbestos fibers are preferably oblique to the receiving surface directed, which supports the control of the filing, for example by reducing displacements or displacements due to deflection and the Fibers also give a certain amount of mast in terms of alignment. An angle of practicality 60 has been found to be particularly satisfactory.

Because the liquid binder and the asbestos fibers are mixed before If they are deposited on the receiving surface, the impregnation begins the asbestos fibers with the binder before the felt is formed. Of course it takes Impregnation on after the fiber layer has been deposited and for as long as the distribution Since the 5i ## 'rs in the vazeln is even, a good one is evenly impregnated Formed felt. When a resin preparation is used as a binder, it preferably contains a sufficient amount of resin solids for a quick and good impregnation of asbestos fibers along with a reasonably short drying time. In general, solutions containing between 10 and 60% resin solids can may be used, although this will of course vary with the type of resin used.

The asbestos fibers are sprayed with a spray gun at a steady speed, preferably fed in an air stream from a fiber feeding machine, the one Includes funnel containing processed asbestos fibers and facilities for continuous supply of a predetermined amount of fibers at a constant speed from a funnel to a air turbine. Preferably only one is proportionate small but controlled amount of fibers held in the hopper.

The fiber flow is preferably from the turbine to the spray gun promoted by means of a flexible hose, which is arranged so that he Only minimally disturbs fiber flow.

The felt layer can be placed on the receiving surface by means of a number formed by strips running across or along the Sprayed web with neither strip slightly overlapping the previous strip in order to achieve the To further increase evenness. This can be done by either the Spray gun is guided relative to the base in the transverse direction or vice versa. Instead of building up a layer of the required thickness in one go, by appropriately adjusted the speed at which the strips are sprayed is preferably obtained the required thickness by a number of Layers are sprayed on top of each other so that a layered felt is created. The deposited layer or layers can be attached are, for example by rolling, before a subsequent layer is deposited.

After the final formation of the mat of binder-coated asbestos fibers If desired, the mat can then be rolled over on the receiving surface to further solidify them and create a smooth surface appearance. The recording The surface can be, for example, plucked or fine wire mesh.

The mat produced is removed from the recording surface and can then be further processed if necessary.

According to the method for producing felts according to the invention resin-bonded felts can be more economical than with conventional working methods not only because of the reduction in work steps but also because shorter fibers can be used than with previous working methods. at known working methods, the prepared fibers must first be carded, while the present method may use fibers that are too short or too brittle are to be carded with the normal machine park.

The method of the invention permits the manufacture of asbestos felts whose properties are so preserved that they the £ # requirements are sufficient for special purposes, for example for applications in vacuum forming or when molding under low pressure.

A preferred method of forming a bonded felt by means of Spray jets according to the invention and a device for carrying out the method is described with reference to the accompanying drawing. The following mean: FIG. 1 a schematic view of the device assembled ready for spraying and is connected; Figure 2 is a schematic longitudinal section through the fiber feed machine the device; Figure 3 is a schematic view of the spray gun, partially in Longitudinal section; Figure 4 shows the spray gun mounted on a cart for use in an automatic spray process; FIG. 5 is a side view of the FIGS Spray gun placed on the carriage shown in FIG. 4.

As shown in FIG. 1, the device comprises a spray gun 1 with a central, axially extending tube 2, the rear End with a flexible hose connection 3mQt the outlet 4 of an asbestos fiber feeding machine 5 is connected. This machine 5 is arranged so that it processed or Prepared asbestos fibers are drawn into a stream of air and these fibers with more evenly Speed along the hose connection 3 of the spray gun 1 supplies. These Fibers are guided by the air flow through the central tube 2 and from the front The end of the tube 2 is ejected at a constant speed.

The spray gun 1, also shown in Fig. 3, is of the type as described in UK patent 764,456 is, when applied to the asbestos cement spray process.

Around the outlet end of the central tube 2 is an annular nozzle head 6, which is provided with a number of nozzle openings 7 which are spaced around the Front surface are arranged.

A pair of connectors 8 and 9 are attached to the rear of the head 6 for supply lines 10 and 11 coming from a three-way control valve 12 that is placed on the outside of the central tube 2. The supply lines 10 and 11 are arranged so that the head 6 liquid binder under pressure and compressed air to atomize the binder through the nozzle openings 7. The nozzle openings 7 are arranged in such a way that the atomized binder streams emanating from them are directed so that they intersect the axis of the central tube 2 and thus mix with the asbestos fibers emerging from the pipe. The distance from the pipe outlet, at which this mixing takes place depends on the construction of the nozzles 7 and the Head 6. However, it has been shown that good results are obtained when this distance is approximately ap cia.

In addition to the two outlet supply lines 10 and 11, the control valve has 12 a further outlet line 13 for the supply of compressed air to the fiber feed machine 5. The control valve 12 has two inlet lines 14 and 15, each with taps 16 and 17 are provided. The line 14 comes from a pressure vessel 18, the one Contains supply of liquid binder for the spraying process. The supply line 15 comes from a source of compressed air (not shown), and upstream from the tap 17 is a branch line 19, which is arranged so that it the vessel 18 is pressurized and which is controlled by a further cock 20. Like in old times mentioned, the control valve 12 is a three-way valve and is operated by a cock 12a actuated. In one position of the tap, atomizing air is supplied from line 15 guided along the line 11 to the head 6, while the feed machine 5 air to Spray gun tube 2 leads. In a second position, the head 6 is next to the line 11 supplied air also supplied binding agent via line 10. In the third Position air is also supplied via line 13 of the machine 5, where a pneumatic clutch (not shown) is operated to start the machine, which then feeds asbestos fibers to the gun and thus begins the full spraying process.

The binding agent output from the nozzle head 6 fluctuates depending on the number of times of the pressure applied to the pressure vessel 18, but an increase in the pressure of the Spray air or the viscosity of the liquid binder in the vessel 18 causes one Reduction of the binding agent output from the nozzle head 6. By adjusting this The desired output amount of binder from the head 6 can be obtained by factors will.

The fiber feeding machine 5 is a modification of that shown in the above-mentioned asbestos cement spraying process and comprises a support frame 21 as a sheath 'which accommodates a funnel 22 for receiving' processed asbestos fibers, which are fed to the funnel 22 through an opening 23, the bottom of the funnel 22 is formed by a pinned conveyor belt 24 which is so arranged is that it rolls around a pair of rollers continuously at a constant speed 25 and 26 moved, one of which is driven. The conveyor belt with pins 24 picks up processed asbestos fibers from hopper 22 and has a tendency to remove them to show around with you. A cover plate 27 is spaced over a fixed distance the conveyor belt provided with pins (Xratzförderer) and causes a Limiting the amount of asbestos fibers that can be removed from the scraper conveyor 24 from the hopper 22 is conveyed away. Immediately after the cover plate 27 is a rotating one Control brush 28, which further limits the amount of asbestos fibers from the scraper conveyor 24 m # led are picked up by the control brush 28 will. A stripping comb 29 attached to the frame 21 and in engagement with the control brush 28 is, removes most of the carried by the brush 28 excess fibers so that they fall back into the funnel 22.

However, in order to ensure that no fibers come from the brush 28 behind the stripping comb 29 and deposited again on the scraper conveyor 24 a scratch plate 30 is arranged to be in the surface of the control brush 28 engages downstream of the comb 29 and thus all remaining fibers from the Brush 28 can be removed from her. An air nozzle 31 is arranged to be blows a stream of air over the scraper plate 30, so that removed fibers from the Brush 28 blown away to an outlet 32 for excess fibers to be blown off where the fibers are returned to hopper 22.

In this way a controlled amount of asbestos fibers is removed from the scraper conveyor 24 led behind the control brush 28. A stripping roller 33 is then arranged so that it strips the hsbest fibers from the scraper conveyor 24 so that they enter the inlet 34 of a turbine mixer 35, which draws the fibers into an air supply, coming from the supply line 13.

The asbestos fibers carried along are carried out by the turbine mixer 35 the outlet 4 is blown into the hose 3 leading to the spray gun 1.

In operation, the spray gun 1 is on a carriage or slide 36 mounted overlying a receiving surface 37 which is arranged so that she runs under the sledge.

The gun 1 is arranged so that its axis makes an angle of about 60 ° to the plane of the receiving surface 37 and in such a way that the head 6 is sufficiently far from the receiving surface 37 to allow the binder spray and the asbestos stream before hitting the receiving surface 37 Mix. Although the carriage or carriage 36 has a number of the same or similar Can carry spray guns 1 at constant speed is shown in the figures 4 and 5, a single pistol 1 is placed on the slide 36, and this carriage is arranged so that it is transverse to the receiving surface 27 with constant speed by means of a chain drive 38 runs. At the end of each Passage actuates the carriage 36 a limit switch 39, which is a pneumatic Ratchet mechanism 40 triggers the recording whether erfläche 37 by a predetermined Amount to move forward, and the carriage 36 is then returned.

This means that an asbestos fiber cover impregnated with binder is built up on the receiving surface in a number of strips, the so The coating obtained is more uniform than the spraying would be controlled by hand. Even so, it is preferable to have a number of passes across the receiving surface 37 so that a layered or laminated felt is built up.

In this way of working, particularly good results are achieved with a 1.2m wide receiving area, which can be reached at a speed of 1.2m per minute if the fiber feeding machine 5 is set up so that it a steady flow of 300g per minute (= 200g / m² per minute) gives away. However, feed rates between 100 g and 5 kg per minute can be used will.

The preferred speed is the amount of asbestos fibers in the hopper 22 of the fiber feeding machine 5 at any given time preferably about 500 g, and is essentially maintained at that amount by adding 100 g of prepared or processed asbestos fibers are introduced every 20 seconds.

A particulate material can be incorporated into the felt, by placing it in the stream of sprayed asbestos fibers included or by depositing it directly on the impregnated fiber that is on the receiving surface is deposited, optionally between two successive @ ends Layers of deposited asbestos fibers0 Examples of particulate material that that can be introduced into the asbestos felt are graphite, silicate, polytetrafluoroethylene and / or metal powder.

Although the fiber feeding machine 5 is arranged to pass through the outlet 4 grains at a constant speed, i.e. at a more even rate Close, is to prevent turbulence before the fiber flow delivers the spray gun 1 reached that part of the hose 5, which the iiittelrohr 2 of the spray gun 1 is adjacent, aligned with the axis of the central tube 2, so that a possible turbulence in the flow of fibers is prevented, the felts thus produced are removed from the receiving surface 37 and then any other required Undergone treatments.

A commonly used binder is a solution of a water-soluble one Phenolic resin, which contains between 30 and 40% resin solids, felts made using made of this resin solution are dried in air at 900 C for a time which is determined by the thickness of the mat and the nature of the resin used. It is usually between 60 and 160 minutes.

A typical felt1 made from chrysotile asbestos and a phenol-formaldehyde resole contains 55% w / w Asbestos, 38% w / w Resin, along with water. This material was press hardened for the production of insulation panels.

Another felt made according to the invention was made by spraying on chrysotile asbestos fibers and a commercially available sodium silicate solution generated. The product was then dried to give a sheet material the 45% w / w Asbestos, 45XXo w / w Sodium silicate and residual and bound Contained water and that can be molded into satisfactory heat-resistant sheets could.

Claims (10)

P a t e n t a n s @ @ @ 1. Ver @ @@@@ @ur a felt @@ which is essentially bound asbestos fibers contains, in that it is a spray jet of droplets a liquid binder and a spray jet of airborne asbestos fibers sprayed as separate streams in such a direction that the streams intersect and mix before they are the only stream that hits a recording surface, where they are deposited in a controlled manner to form an even layer which is then removed from the recording surface 0 2. procedure according to claim 1, characterized in that the flow of liquid Binder and the stream of asbestos fibers directed obliquely towards the receiving surface are. 30 The method according to claim 1 or 2, characterized in that it is 1 c h n e t that heat is supplied and thus ensures that the binder at least remains liquid until the currents mix and hit the receiving surface are filed. 4e method according to one of the preceding claims, characterized g ek It is noted that the felt cover on the receiving surface is in a Number of strips is deposited, which is sprayed along or across the receiving surface with each strip slightly overlapping the previous strip. 50 The method according to claim 4, characterized in that that the strips are sprayed from a spray gun or from guns that on a sled or cart is or are arranged transversely is dragged across the receiving surface or the carriage by a predetermined one Extent is switched forward at the end of each transverse run, and the slide then withdrawn over the pad to spray the next strip. 6. The method according to a # m of the preceding claims, characterized g e It is not noted that the mat can be formed by spraying a number of Coating is built up. 70 The method according to any one of the preceding claims, characterized in that does not indicate that additional particulate material is used during manufacture is fed to the felt. 8o The method according to claim 7, characterized in that the additional particulate material included in the stream of asbestos fibers which is sprayed onto the receiving surface. 90 The method according to claim 7, characterized in that that the additional particulate material is applied directly to the impregnated fiber is deposited, which is deposited on the receiving surface, preferably between successive layers of the deposited asbestos fibers. 10. The method according to any one of the preceding claims, characterized in that the receiving surface is a web or a sheet-like material on the Underlay and either allow a particularly easy separation of the deposited fiber felt or remain directly on the asbestos felt during further processing. 11o Bound felt made of asbestos fibers, produced according to the process according to one of the preceding claims.