Patent Application
20090095820
The invention relates to a method for consolidating traffic routes, preferably railroad tracks, roads and unconsolidated routes.
Traffic routes, such as railroad tracks, roads and unconsolidated routes, largely comprise loose particles. Thus, railroad tracks generally have a road bed. Unconsolidated roads and routes generally have loose sand or dust on their surface. It is frequently necessary to fix these particles. In the case of railroad tracks, loose ballast stones may be thrown up and thus lead to problems. Particularly high-speed trains, such as ICE trains throw up the stones present underneath them so that the underbody suffers damage. This is because the track beds in many countries do not lie as deep as in Germany. However, laying them deeper would entail an additional expense.
A further problem is the consolidation of unconsolidated roads and routes. These are generally covered with dust, sand or gravel. When they are driven on, dust may be swirled up or stones thrown up. This leads to pollution of the environment and also to soiling of the vehicles, which in turn can lead to increased wear thereof. Flying stones may also cause injuries to passers-by. In addition, there is considerable stress on the unconsolidated roads. In particular, ruts may form. This is undesired since deep ruts lead to damage to the vehicles and water can collect in the ruts, which leads to damage to the routes.
A further problem is the repair and consolidation of roads. Even consolidated roads are subject to wear, which can lead to loosening of the materials used for road construction. Here, complete repair is frequently expensive and time-consuming.
The prior art discloses a number of possibilities for consolidating such traffic routes. In the area of the consolidation of railroad tracks, the ballast bonding technique is now an established technique. The bonding serves for prevention of ballast being thrown up, for stabilization of the track bed and for securing of the operating tracks during track construction work. In this method, the track ballast is as a rule first applied to the ballast bed. The ballast is then wet with a self-curing adhesive in a spray process. A frequently used adhesive is epoxide but acrylates and polyurethanes are also used.
Thus, WO 2004/079094 describes the consolidation of stone beds, such as railroad embankments, by bonding them with plastics and applying an insert in the interior of the stone beds.
DE 197 29 348 describes a method for the production of a closed, drainable, crushed-rock pavement in track construction. The upper layer of the ballast is covered with a cavity-filling layer of filling material. The filling material can also be applied as a layer up to 10 cm high on the ballast. Filling material used is bulk material having a particle size of from 1 to 16 mm, the particles of which are covered with a plastic film. For example, epoxy resins or polyurethanes are used as adhesives.
DE 198 11 838 describes a method and an apparatus for consolidating ballast beds. A liquid consolidating material is injected into the ballast bed. The consolidating material may likewise be a polyurethane. A similar method is also described in U.S. Pat. No. 4,156,440.
CH 595512 describes a method for the stabilization and vibration damping of railroad tracks, in which a foamable polyurethane mixture is introduced into the track bed, where it cures to give a foam.
The consolidation of loose soils by application of plastics is also known. It is known that loose rock formations can be consolidated with plastics, for example in mining or for the fixing of surfaces. It is possible to use different plastics, for example polyesters, polyacrylates or polyurethanes.
DE 197 03 980 describes the use of biodegradable plastics for consolidating soils. Here, planting of the soil is to be achieved, by means of which said soil is stabilized. For the stabilization of unconsolidated routes, it is required in particular to avoid the decomposition of the plastic layer.
U.S. Pat. No. 3,719,050 describes the stabilization of soils using polyurethane prepolymers. These prepolymers should preferably be water-repellant. The curing takes place by means of water. This results in foaming of the polyurethane, which is disadvantageous for the consolidation of unconsolidated routes. Furthermore, the polyureas forming in the reaction of the prepolymers with water are not hydrophobic, so that they offer no protection from water and may also be decomposed hydrolytically.
It was the object to safely consolidate traffic routes and thus to avoid particles being thrown up. Furthermore, it is intended to reduce the wear on the roadways. The consolidation should be possible by a simple method and should not cause any environmental problems. The traffic routes should furthermore be treated so that attack by water is minimized.
The object could surprisingly be achieved if a hydrophobic polyurethane is present on the surface and/or in the interior of the roadway.
The invention relates to a method for consolidating roadways, wherein at least one plastic, in particular a hydrophobic polyurethane, is applied to the surface and/or in the interior of the roadway.
In many applications, both in the case of tracks and in the case of unconsolidated roads and routes and also in the repair of roads, the application of the hydrophobic polyurethane to the surface of the traffic route is sufficient. The application of the polyurethane can be effected in the simplest case by applying the liquid starting components of the polyurethane by spraying or by pouring to the roadway, where they cure to give the polyurethane. Spraying is preferred since less material is consumed thereby. The spraying can be effected by vehicles or manually.
In a particular embodiment of the method according to the invention, in particular in the case of thicker layers of loose particles, the plastic is introduced into the layer. This embodiment is preferably used in the case of tracks.
This can take place, for example, by wetting of the particles, in the case of tracks by a wetting of the ballast, with the liquid starting components of the plastic in a mixer and application of the wetted particles to the traffic route, where the starting components cure to give the polyurethane.
The loose stones are preferably ballast, as usually used for the production of track beds. The size of the ballast stones depends on the loading of the tracks. Usually, the size of the ballast stones is from about 30 to 70 mm. They preferably consist of hard rock, such as basalt.
In principle, all types of mixers with which substantially complete wetting of the ballast stones with the liquid starting components of the plastic is possible can be used as mixers for mixing the ballast stones with the starting components of the plastic. Mixers which consist of an open container, for example a drum, which is preferably provided with internals, have proven particularly suitable. For mixing, either the drum can be rotated or the internals moved.
Such mixers are known and are used, for example, in the building industry for the production of concrete mixes.
For application of the mixture to the surface to be consolidated, it may be advantageous to mount the mixer on a vehicle, for example a tractor, a frontloader or a truck or a railway vehicle. In this embodiment of the method according to the invention, the mixture can be transported in each case to the location where it is to be applied. After emptying of the mixer, the mixture can, if required, be distributed manually, for example by means of rakes, for achieving the desired structure.
In an embodiment of the method according to the invention, the mixing of the stones with the liquid starting components of the plastic is effected continuously. For this purpose, the stones and the liquid starting components of the plastic are introduced continuously into the mixer and the wetted stones are discharged continuously. In this procedure, it must be ensured that the starting materials remain in the mixer until sufficient wetting of the stones can take place. Expediently, such a mixing apparatus can be moved along the track bed to be consolidated at such a speed that the stones wetted with the liquid components of the plastic are discharged from the mixer in the amount required. It is also possible to operate the continuous mixing apparatus in a stationary manner and to transport the wetted stones discharged from the mixer to the desired location.
In a further embodiment of the continuous development of the method according to the invention, the mixer may be a rotating drum into which stones are continuously introduced. This drum is equipped with nozzles which distribute the starting components of the plastic continuously over the stones. Here, the rotation of the drum ensures thorough mixing of the plastic and the stones. Plastic/stone composites are then discharged continuously through an opening at the end of the drum. The rotating drum may be horizontal but also inclined at different angles to promote the discharge.
In a further embodiment of the continuous method, the stones are transported continuously onto a conveyer belt which passes through a tunnel. This has openings via which the starting materials of the plastic are continuously discharged onto the stones. At the end of the conveyer belt, the wetted stones fall onto the track or into an open drum which discharges the composite onto the track at an adjustable delivery speed.
Preferably, the entire ballast bed is consolidated with the plastic. It is also possible to consolidate only the upper layer of the ballast bed, preferably up to 20 cm, with the plastic. In this embodiment, too, either the ballast bed can be deposited initially without plastic and then the liquid starting components of the plastic can be applied or first only a part of the ballast bed can be deposited and a layer of stones mixed with the liquid starting components of the plastic can then be applied, as described above.
Plastics which may be used are polyurethanes, epoxy resins, unsaturated polyester resins, acrylates and methacrylates.
In a preferred embodiment of the invention, hydrophobic, substantially compact polyurethanes are used as plastics.
Regarding the preferably used hydrophobic polyurethanes, the following may be stated.
Components of the hydrophobic polyurethanes are understood very generally as meaning compounds having free isocyanate groups and compounds having groups which are reactive with isocyanate groups. Groups which are reactive with isocyanate groups are generally hydroxyl groups or amino groups. Hydroxyl groups are preferred since the amino groups are very reactive and the reaction mixture therefore has to be rapidly processed. The products formed by reaction of these components are referred to below generally as polyurethanes.
When applying the components for the hydrophobic polyurethanes, it is not necessary for the top layer of the unconsolidated road or the stones of the track bed to be present in the dry state. Surprisingly, good adhesion between the polyurethane and the stones is also obtainable when wet stones are present. The curing of the hydrophobic polyurethane can even take place under water, since even puddles on the unconsolidated roads do not substantially impair the application of the polyurethane.
In principle, all polyisocyanates, mixtures and prepolymers which are liquid at room temperature and have at least two isocyanate groups may be used as polyisocyanates.
Aromatic polyisocyanates are preferably used, particularly preferably isomers of tolylene diisocyanate (TDI) and of diphenylmethane diisocyanate (MDI), in particular mixtures of MDI and polyphenylenepolymethylene polyisocyanates (crude MDI). The polyisocyanates may also be modified, for example by the incorporation of isocyanurate groups and in particular by the incorporation of urethane groups. The last-mentioned compounds are prepared by reacting polyisocyanates with less than the stoichiometric amount of compounds having two active hydrogen atoms and are usually referred to as NCO prepolymers. Their NCO content is generally in the range of from 2 to 29% by weight.
A disadvantage of the use of aromatic polyisocyanates is the insufficient color stability of the polyurethanes prepared therefrom. In general, substantial yellowing of the polyurethanes occurs in the course of time. In the case of applications of the method according to the invention in which high color stability is important, the use of aliphatic polyisocyanates is therefore preferred. Preferred members are hexamethylene diisocyanate (HDI) and isophorone diisocyanate (IPDI). Owing to the high volatility of the aliphatic polyisocyanates, these are generally used in the form of their reaction products, in particular as biurets, allophanates or isocyanurates.
In general, polyfunctional alcohols, so-called polyols, or, less preferably, polyfunctional amines are used as compounds having at least two hydrogen atoms reactive with isocyanate groups.
The hydrophobicity of the polyurethanes used can be brought about in particular by addition of components having hydroxyl functions and customary in fat chemistry to at least one of the starting components of the polyurethane system, preferably to the polyol component.
A number of components having hydroxyl functions and customary in fat chemistry are known and can be used. Examples are castor oil, oils modified with hydroxyl groups, such as grapeseed oil, black cumin oil, pumpkin seed oil, borage seed oil, soybean oil, wheatgerm oil, rapeseed oil, sunflower oil, peanut oil, apricot kernel oil, pistachio oil, almond oil, olive oil, macadamia nut oil, avocado oil, sea buckthorn oil, sesame oil, hazelnut oil, evening primrose oil, wild rose oil, hemp oil, thistle oil, walnut oil, fatty acid esters modified with hydroxyl groups and based on myristoleic acid, palmitoleic acid, oleic acid, vaccenic acid, petroselenic acid, gadoleic acid, erucic acid, nervonic acid, linoleic acid, linolenic acid, stearidonic acid, arachidonic acid, timnodonic acid, clupanodonic acid or cervonic acid. Castor oil and the reaction products thereof with alkylene oxides or ketone/formaldehyde resins are preferably used here. The last-mentioned compounds are sold, for example by Bayer AG under the name Desmophen® 1150.
A further preferably used group of polyols customary in fat chemistry can be obtained by ring opening of epoxidized fatty acid esters with simultaneous reaction with alcohols and, if appropriate, subsequent further transesterification reactions. The incorporation of hydroxyl groups into oils and fats is effected in the main by epoxidation of the olefinic double bond present in these products, followed by the reaction of the resulting epoxide groups with a monohydric or polyhydric alcohol. The epoxide ring becomes a hydroxyl group or, in the case of polyfunctional alcohols, a structure having a larger number of OH groups. Since oils and fats are generally glyceryl esters, parallel transesterification reactions also take place during the abovementioned reactions. The compounds thus obtained preferably have a molecular weight in the range of from 500 to 1500 g/mol. Such products are available, for example from Henkel.
In a particularly preferred embodiment of the method according to the invention, the compact polyurethane used is one which can be prepared by reacting polyisocyanates with compounds having at least two hydrogen atoms reactive with isocyanate groups, wherein the compounds having at least two reactive hydrogen atoms comprise at least one polyol customary in fat chemistry and at least one aromatic hydrocarbon resin modified with phenol, in particular an indene-coumarone resin. These polyurethanes and their components have such a high hydrophobicity that they can in principle cure even under water.
Preferably indene-coumarone resins modified with phenol, particularly preferably industrial mixtures of aromatic hydrocarbon resins, are used as aromatic hydrocarbon resins modified with phenol and having a terminal phenol group, in particular those which comprise, as substantial constituent, compounds of the general formula (I)
where n is from 2 to 28. Such products are commercially available and are offered, for example by Rutgers VFT AG under the trade name NOVARES®.
The aromatic hydrocarbon resins modified with phenol, in particular the indene-coumarone resins modified with phenol, generally have an OH content of from 0.5 to 5.0% by weight.
The polyol customary in fat chemistry and the aromatic hydrocarbon resin modified with phenol, in particular the indene-coumarone resin, are preferably used in a weight ratio of from 100:1 to 100:50.
Together with said compounds, it is possible to use further compounds having at least two active hydrogen atoms. Owing to their high stability to hydrolysis, polyether alcohols are preferred. These are prepared by customary and known processes, generally by an addition reaction of alkylene oxides with H-functional initiator substances. The concomitantly used polyether alcohols preferably have a functionality of at least 3 and a hydroxyl number of at least 400 mg KOH/g, preferably at least 600 mg KOH/g, in particular in the range of from 400 to 1000 mg KOH/g. They are prepared in a customary manner by reacting at least trifunctional initiator substances with alkylene oxides. Alcohols having at least 3 hydroxyl groups in the molecule, for example glycerol, trimethylolpropane, pentaerythritol, sorbitol or sucrose can preferably be used as initiator substances. A preferably used alkylene oxide is propylene oxide.
Further customary constituents may be added to the reaction mixture, for example catalysts and customary assistants and additives. In particular, drying agents, for example zeolites, should be added to the reaction mixture in order to avoid the accumulation of water in the components and hence foaming of the polyurethanes. These substances are preferably added to the compounds having at least two hydrogen atoms reactive with isocyanate groups. This mixture is frequently referred to in the industry as polyol component. For improving the long-term stability of the composites, it is furthermore advantageous to add compositions for preventing attack by microorganisms. The addition of UV stabilizers is also advantageous, in order to avoid embrittlement of the moldings.
The polyurethanes used can in principle be prepared without the presence of catalysts. For improving the curing, catalysts may be concomitantly used. Catalysts chosen should preferably be those which result in as long a reaction time as possible for the reaction mixture to remain liquid for a long time. It is possible in principle, as described, also to work entirely without a catalyst.
The combination of the polyisocyanates with the compounds having at least two hydrogen atoms reactive with isocyanate groups should be effected in a ratio such that a stoichiometric excess of isocyanate groups, preferably of at least 5%, in particular in the range of from 5 to 60%, is present.
The preferably used hydrophobic polyurethanes are distinguished by particularly good processability. Thus, these polyurethanes exhibit particularly good adhesion, in particular to moist substrates, such as wet rock, in particular granite ballast. The curing of the polyurethanes takes place in virtually compact form despite the presence of water. The compact polyurethanes used exhibit completely compact curing even in the case of thin layers.
The preferably used polyurethanes are therefore outstandingly suitable for consolidating traffic routes. The bond between rock or sand and polyurethane is very strong. Furthermore, particularly with the use of very hydrophobic polyurethanes, there is virtually no hydrolytic degradation of the polyurethanes and hence very long stability of the traffic routes consolidated by the method according to the invention.
For carrying out the method according to the invention, the polyisocyanates are preferably mixed with the compounds having at least two active hydrogen atoms and this mixture is mixed with the stones. In principle, it should also be possible to add both starting components of the polyurethane separately to the stones and to mix them together with these. In this case, however non uniform mixing and hence inadequate mechanical properties of the polyurethane may result.
The mixing of the starting components of the polyurethane can be effected in a known manner. In the simplest case, the components can be introduced in the desired ratio into a vessel, for example a bucket, mixed by simple stirring and then mixed with the stones in the mixing apparatus. It is also possible to mix the starting components of the polyurethane in a mixing member customary in polyurethane chemistry, for example a mixing head, and to bring this mixture into contact with the stones.
The consolidation of traffic routes with the hydrophobic polyurethanes has a number of advantages.
The consolidation has a longer life, requires less repair work and leads to higher traffic safety than other plastics for this intended use. Owing to their hydrophobicity, frost damage is substantially suppressed, and there is also no noticeable hydrolytic degradation. Rain water runs off from the traffic routes consolidated by the method according to the invention.
The polyurethanes cause no ecological problems, and in principle therefore not only road surfacings but also forest paths can be consolidated with these polyurethanes. If appropriate, unconsolidated roads or runways, for example take off and landing runways for aircraft, could also be coated by the method according to the invention. There, the throwing up of dust can lead to damage to the engines.
The consolidation of ballast beds with the hydrophobic polyurethanes leads to time and cost savings in train journeys since the trains can travel at regular speed without leading to damage.
The method is substantially more economical than laying the track bed lower, since the adhesive can be applied directly with the ballast stones.
In contrast to the plastics used to date, the hydrophobic system can also be processed in the rain and on a moist surface. This results in a not inconsiderable economic advantage since waiting times during wet weather are dispensed with.
In spite of the hardness of the bond, the water permeability of ballast beds treated according to the invention is fully retained because the stones are bonded at points. Even in heavy rainfall, this eliminates the risk of washing out. Washing out and frost damage are thus effectively prevented; in particular, washing out in the case of a hydrophobic PU system is even less than in the case of a non-hydrophobic plastic.
With the described mixing of the stones with the liquid starting components of the plastic, there is the advantage of a single process step, which in turn increases the cost-efficiency of the method.
| Number | Date | Country | Kind |
|---|---|---|---|
| 06111178.7 | Mar 2006 | EP | regional |
| Filing Document | Filing Date | Country | Kind | 371c Date |
|---|---|---|---|---|
| PCT/EP2007/052214 | 3/9/2007 | WO | 00 | 9/12/2008 |
