KR920007240B1 - Resilient coat for tie of direct-connection type track - Google Patents

Abstract

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Description

Elastic covering material for direct track sleepers

1 is a plan view of an embodiment of the sleeper of the present invention.

2 is a cut along the line A-A of the embodiment of FIG.

3 is a cut along the line B-B of the embodiment of FIG.

4 is a vertical cross-sectional view of the direct sleeper of the present invention temporarily placed on the foundation of the railway.

5 is a vertical cross-sectional view of the direct sleeper of the present invention laid below the railroad track.

6 is a perspective view of a mold fixed on a concrete sleeper in accordance with the present invention.

7 is a view taken along the line A-A of the embodiment of FIG.

8 is a flow chart showing the steps of manufacturing a direct sleeper in accordance with the present invention.

9 is an enlarged cut of the mold portion around the deaerator.

The present invention relates to sleepers for railway tracks. More specifically, the present invention is a direct type sleeper elastic consisting of a concrete sleeper for supporting a rail, which is bottom-coated with a layer of microcellular polyurethane-based elastomer attached to the concrete sleeper to form an integrated body. It relates to a coating material. The above-mentioned direct sleepers are easy to maintain, at the same time low in vibration and noise of the railway, and can be laid very accurately and easily.

Recently, the known gravel sleeper tracks tend to be replaced by easy-to-maintain direct tracks, such as the use of track slabs, because labor savings are chiefly required. However, in this direct track system, the concrete slab is directly laid on the solid subgrade without gravel and gravel-carpet, which has the drawback of increasing railway vibration and noise compared to the gravel-carpeted elastic gravel track. Can be.

Therefore, it is necessary to develop a new system that is easy to maintain and has low vibration and noise of the railway. In order to meet this demand, so-called "elastic coated sleepers", ie larger concrete sleepers (i.e. reduced track slab size) have been proposed in which the bottom and sides of the sleepers are covered with elastomeric material, thus providing So-called direct-elastic sleeper systems are being investigated in view of the fact that laying sleepers using grout (eg synthetic resins, grouting concrete, etc.) reduces vibration transmission and noise.

In the past, an elastomeric material for elastically coated sleepers was mixed with a crushed rubber obtained from used car tires and a polyurethane-based adhesive, filled in a mold, compressed with a compressor, and then aged under heating to use the product. Proposed. However, the manufacture of such elastic materials requires not only large equipment and a lot of labor (production efficiency: one product per mold), but also the incomplete adhesion of the elastic cladding to the concrete sleepers and in some cases peeling off. It may be. Furthermore, even when a known elastic-coated sleeper is laid and buried on the concrete roadbed and then fixed in place with grouting concrete, free deformation is suppressed because the elastic material is almost completely fixed to the concrete. Therefore, the spring constant increases, the dustproof effect decreases, and the property of using the elastic coating material is lost.

Therefore, in the system for embedding and fixing the sleepers on and inside the concrete subgrade using grouting concrete (direct rail) in order to reduce vibration and noise, the dust-proof coating is very limited by the grouting concrete, and free deformation is also suppressed. For this reason, there is still a need for a dust-proof coating material that exhibits sufficient vibration reduction and noise reduction even under conditions in which the spring constant does not increase and is strongly adhered to the sleeper and free deformation is limited.

The properties required for direct tie-down elastic-coated materials that can be used on railroad tracks in which multi-car trains run at high speeds are more stringent. For example, the following characteristic classes are required.

Compression permanent rate: 15% or less

Spring constant: 0.2 ~ 2ton / cm / 100㎠

Tensile Strength: More than 5kgf / ㎠

Tensile Elongation: 100% or more

Water resistance (tensile strength change rate): within ± 20%

(Tensile elongation change rate): within ± 20%

Alkali resistance (tensile strength change rate): within ± 20%

(Tensile elongation change rate): within ± 20%

Fatigue Resistance: Less than 1.0㎜ of fatigue

The material must simultaneously satisfy the above conditions.

Moreover, elastic or elastomeric coatings must be strongly bonded to concrete sleepers and never peel off due to repeated compression by intermittent train passages.

The inventors of the present invention are elastomeric polymer materials that fully satisfy these requirements, and have a polyhydric alcohol having an average number of functional groups of 2.5 to 3.5 and a number average molecular weight of about 4,500 to 8,500, an organic polyisocyanate, a chain-extending agent, and a urethane. Invented and proposed a micro-cellulose urethane-based elastomer having a bulk density of 0.3 to 0.9 g / cm 3 prepared from a foaming stock solution of a urethane-based elastomer composed of a polymerization catalyst and a blowing agent. At this time, the stock solution contains a chain extender having a concentration of 0.2 × 10 ^{−3 to} 1.0 × 10 ⁻³ mol / g per weight unit of urethane-based elastomer (Japanese Patent Publication No. 130754/1980).

Microcellular urethane-based elastomers satisfying the above-mentioned grades have been proposed in the past and were actually used in straight sections of high-speed railway tracks. However, it is only logical that it is desirable to further reduce the bulk density by reducing the bulk density even when such an elastic polymerized wood material composed of a microcellular urethane-based elastomer is used. Low bulk density necessarily reduces the spring constant. Furthermore, in the curved sections of railway tracks, the tracks are particularly high in centrifugal force, so that the elastomeric material is very compressed, creating a space between the elastomeric coating material and the grouting concrete, where water and dust accumulate. Therefore, it is not enough to simply increase the foaming degree of the aforementioned microcell urethane-based elastomer in order to reduce the bulk density. For example, if the spring constant can be maintained at about 1.0 tf / cm / 100 cm while maintaining the bulk density of the microcellulose urethane-based elastomer at 0.7 g / cm 3 or less, there is a problem in that the compression set is increased.

In this state, it is an object of the present invention to provide a direct sleeper made of a micro-cellular polyurethane-based elastomer in which the elastomeric hardwood material does not significantly increase the compression set even in spite of its low bulk density.

Still another object of the present invention is to provide a direct sleeper that can accurately and easily lay a direct railroad track by drilling through holes for bolts vertically penetrating the direct sleeper including an elastomeric coating material. .

Still other objects and advantages of the present invention are apparent from the following description.

According to the present invention, the elastic-coated direct sleeper is composed of a line support concrete sleeper and a microcellular polyurethane elastomer coating layer attached to the bottom of the sleeper and covering it to form an integrated body. There are two or more bolt through holes vertically penetrating the coating layer, and the through holes of the sleeper are buried with nuts that fit the bolts, and the microcellular polyurethane elastomer has a urethane bond and has a bulk density of 0.4 to 0.75 g / cm 3 and is made from a foamable stock liquid of a urethane elastomer consisting mainly of:

(a) polyether polyols having an average number of functional groups of 2.5 to 4.5 and an average molecular weight of 2,000 to 8,500;

(b) vinyl monomer graft polyols having an average number of functional groups of 2.5 to 4.0 and a graft ratio of 4 to 20% by weight;

(c) liquid polybutadiene polyols having terminal hydroxyl groups having an average number of functional groups of 2.0 to 3.0 and an average molecular weight of 2,000 to 7,000,

(d) organic polyisocyanates,

(e) chain extenders,

(f) blowing agents and

(g) urethane reaction catalyst

In this configuration, the NCO index ranges from 90 to 110, and the concentration of the chain extender for the total amount of the five components (a), (b), (c), (d) and (e) is 0.3 × 10 ^−3. It is -1.5 * 10 <^-3> mol / g.

Hereinafter, the sleeper of the present invention will be described in more detail with respect to embodiments in the accompanying drawings.

As shown in Figs. 1 to 3, the sleepers of the present invention are basically attached to the lower part of the sleeper, and covered with a microcellular polyurethane-based elastomer coating layer 2 to form an integrated body. It consists of 1 structure.

In the present specification and claims, the surface of the sleeper on which the railroad is placed is designated as "normal", the opposite side is referred to as "bottom", and the other side is designated as "side".

As shown in Figures 2 and 3, coating layer 2 covers the lower part of the entire bottom and sides of the concrete sleeper. In such a case, the height h of the side covering layer is not particularly limited, but may vary greatly depending on the use purpose of the direct sleeper (high speed railway, ordinary railway, subway, etc.). However, the normal height h is preferably 1/20 to 1/1 of the height H of the concrete sleeper, preferably 1/4 to 3/4, still more preferably 1/2 to 3/5. In the case of ordinary concrete sleepers having H of 8 to 30 cm, the height h of the coating is preferably 4 to 18 cm.

The thicknesses w and w 'of the coating layer 2 are not limited but may vary greatly depending on factors such as the use of the direct sleepers.

In general, however, it should be at least 8 mm. The upper limit of the thickness is not limited but generally 50 mm or less is sufficient. Too thick a coating layer is expensive and there is no benefit to justify this increase. Therefore, the thickness of coating layer 2 is generally 10 to 35 mm, and preferably 15 to 30 mm. The thickness of coating layer 2 may be the same at the bottom and side within the aforementioned range, but the thickness w 'of the less loaded side may be less than the thickness w coated at the side of the sleeper. For example, the range of w is 15 to 50 mm, preferably 20 to 30 mm, w 'is 5' 50 mm, preferably 18 to 29 mm, and w-w 'is 1 to 10 mm.

The size of the concrete sleepers coated with this coating layer may vary depending on the use of the sleepers, but is usually 50 to 1,000 cm wide, 200 to 280 cm long, and 10 to 30 cm high.

The most outstanding characteristics of the sleepers of the present invention are the penetration of the two or more bolt through-holes 3, 3 ', 3 "… and the concrete sleeper 1 which vertically penetrates the concrete sleeper 1 and the covering layer 2 of the direct sleeper described above. -To provide a nut 4 for the bolt buried in the hole.

As illustrated in FIG. 4, support bolts 6, 6 ', 6 "in through-holes 3, 3', 3", etc. for fitting each bolt. Tighten your back and pierce your sleepers. These support bolts can be adjusted to determine the three-dimensional position of the sleepers so that the top of the sleepers can be laid with the desired slope and height.

These through-holes can be drilled like 3 and 3 "near both ends of one edge of concrete sleeper 1, as illustrated in Figure 1, and 3 'near both sides of the opposite edge. If not, drill two holes 3 '' 'and 3' 'in the opposite corner to fit the holes 3' and 3 '' instead of the hole 3 'near the center of the opposite edge, as shown by the dashed line in Figure 1. -You can make 4 holes.

The size of the through-holes depends on the thickness of the support bolts to be fitted, but advantageously usually 10 to 40 mm in diameter, preferably 20 to 30 mm is selected.

In the center of the bottom of the bottom of the coating layer 2 composed of microcellular polyurethane-based elastomers, which are less loaded, it is possible to form a settlement as shown in FIGS. 2 and 3, and the microcellular polyurethane-based elastic The flexible synthetic foam 5 which is cheaper than the polymer can be fitted. This avoids the central action causing problems with the strength properties of the sleepers and reduces the consumption of expensive microcellular polyurethane based elastomers. As the synthetic resin foam used for this purpose, a cell form crosslinked with a polyurethane foam having an apparent density of usually 0.01 to 0.1, preferably 0.02 to 0.05 is suitable.

The length of the aforementioned settlement (indicated by t in FIG. 2) is usually in the range of 1/4 to 1/2, preferably 1/4 to 1/3 of the length of the concrete sleeper. The length t can be changed suitably within this range. The depth of settlement (indicated by d in FIG. 2) is in the range of 1/10 to 1/1, preferably 1/2 to 7/10 of the thickness w of the coating layer 2 at the bottom. The settlement is advantageously formed over the entire area of coating layer 2, as shown in FIG.

The direct sleepers of the present invention having the structure described above can be laid under railroad tracks in the manner illustrated in FIGS. 4 and 5 and described below.

That is, the support bolts 6, 6 ', 6 ", etc. are through-holes vertically penetrating the direct sleepers of the present invention, such as those drilled into the concrete sleepers 1 such that their bottom ends protrude to the bottom of the covering layer 2 of the sleepers. Fit with nut 4 on 3, 3 ', 3 ", etc. The bottom end of the bolt is in contact with the concrete creep 7 built on the foundation of the railway track, and each bolt can be adjusted to determine the horizontal and slope of the top of the sleeper 1 (Figure 4).

Then, the rails 8 and 8 'are fixed to the upper end of the concrete body 1 by a known method, and the grout concrete on the foundation and the bottom of the concrete sleeper pour grouting concrete into the space between the coating layer 2 to form a solid phase 9. Before the concrete is completely cleaned, the support bolts 6, 6 ', 6 ", etc. are removed and an elastomeric lid is placed on top of the through-holes 3, 3', 3", etc. (fig. 5).

The sleeper of the present invention, through which the support bolts 6, 6 ", 6", etc. are inserted through the through-holes 3, 3 ', 3 ", etc., which vertically penetrates the sleeper, adjusts the aforementioned bolts to the desired horizontal and The slope can be adjusted, which makes it possible to lay railroad tracks very accurately and easily.

When pouring concrete, care must be taken not to flow into the through-holes so that the concrete sleeper 1 and phase 9 are directly connected. This is because if they are connected directly, the vibration of concrete sleeper 1 is transmitted directly to phase 9, and therefore cannot absorb or cushion in coating layer 2. Therefore, the size of the hole should be at least equal to or only slightly larger than the thickness of the bolt to be inserted at the bottom of the coating layer to prevent the concrete from entering the hole.

For the same reason, the concrete that forms the bed should not go beyond the upper edge of the side covering layer 2 of the sleeper, which is directly connected to the concrete sleeper 1 (Figure 5).

In short, it is very important to completely separate concrete sleeper 1 from concrete 9.

One of the outstanding characteristics of the direct sleeper of the present invention is the use of a special microcellular polyurethane foam as the material for the coating layer.

That is, the inventors of the present invention suggest that the microcellular polyurethane-based elastomer is directly coated with a sleeper covering material which can exhibit a dustproof effect at a location between a concrete sleeper and a roadbed as well as grouting concrete used as a solid phase due to a viscoelastic energy loss effect. Found to be very suitable. According to the present invention, the spring constant of a direct sleeper can be reduced by the appropriate selection of a flexible polyurethane-based elastomer equal to or less than the spring constant of the jalja track on a hard roadbed such as a high rise bridge, Noise can also be effectively suppressed. Furthermore, with the use of microcellular polyurethane-based elastomers, the elastomer can be freely deformed even when the elastomeric material is limited to the grouting concrete used in the solid phase, a significant effect of the anti-vibration effect due to the increase in the spring constant. The reduction can be suppressed.

The bulk density range of the microcellular polyurethane-based elastomer used in the present invention is usually 0.4 to 0.75 g / cm 3, preferably 0.55 to 0.7 g / cm 3.

The physical and chemical properties other than the bulk density of the polyurethane-based elastomer can be changed over a wide range by selecting the components. However, when used for the special purpose of dustproof as in the case of the present invention, an optimal component should be selected to have the desired durability and dustproofness. Hereinafter, the composition of the polyurethane-based elastomer suitable for the purpose of the present invention will be described in detail.

The microcellular polyurethane-based elastomers used in the present invention include (a) polyether polyols, (b) polyols grafted with vinyl monomers, (c) liquid polybutadiene polyols, (d) organic polyisocyanates, (e) chain extension And a foamable stock solution of a urethane-based elastomer composed of (f) a blowing agent and (g) a urethanization catalyst.

The polyether polyol, which is one of the polyol components in the preparation of the polyurethane-based elastomer according to the present invention, has an average number of functional groups of 2.5 to 4.5 and an average molecular weight of 2,000 to 8,5000. When the average number of functional groups of the polyether polyols used is 2.5 or less, the compression set of the obtained expandable urethane-based elastomer increases. Conversely, when the average number of functional groups is 4.5 or more, the resulting elastomer tends to cure gradually, increasing the possibility of breaking under vibration pressure. Thus, the preferred number of average functional groups is 2.5 to 4.5, in particular 2.8 to 4.0.

When the average molecular weight of the polyether polyol (a) is 2,000 or less, it is difficult to obtain a foamable polyurethane-based elastomer having excellent dustproofness. On the contrary, when 8,500 or more, the resulting polyurethane-based elastomer has low elasticity and plastic deformation. In particular, there is a strong tendency to increase the permanent compression ratio. Therefore, the average molecular weight of the polyether polyol used in the present invention is preferably 2,000 to 8,500, particularly 3,000-6,500.

Such polyether polyol (a) can be used arbitrarily among those generally used in the production of polyurethane-based elastomers. More specifically, these polyether polyols are C ₂ -C ₄ lower alkylene oxides such as ethylene oxide, propylene oxide and C ₂ -C ₆ aliphatic polyhydric alcohols such as glycerin, trimethylolpropane, or ethylenediamine, diaminodiphenylmethane It is usually obtained by an addition-polymerization reaction with what may be termed an active hydrogen-containing compound having an active hydrogen atom such as the like. Typical examples of such polyether polyols (a) include adducts in which glycerin / propylene oxide / ethylene oxide is interpolymerized (average number of functional groups = 3.0, average molecular weight = 3,000), addition in which propylene glycol / propylene oxide / ethylene oxide is interpolymerized. Water (average number of functional groups = 2.0, average molecular weight = 4,800) and adducts (average number of functional groups = 3.7, average molecular weight = 5,700) hybridized with glycerin / pentaerythritol / propylene oxide / ethylene oxide.

One of the outstanding features of the present invention is a polyol component constituting the expandable polyurethane-based elastomer, which is grafted with a vinyl monomer having an average number of functional groups of 2.5 to 4.0 and a graft ratio of 4 to 20% by weight together with the polyether polyol (a). Polyol (b), liquid polybutadiene polyol (c) and terminal hydroxyl groups having an average number of functional groups of 2.0 to 3.0 and an average molecular weight of 2,000 to 7,000 are used.

"Vinyl monomer grafted polyol" (hereinafter referred to as graft polyol) '(b) is used by the radical polymerization of vinyl monomers in the presence of polyols, usually known as polyol components for producing highly elastic urethane foam. By means of modified polyols prepared (e.g., Japanese Patent 447628, United States Patent No. 3093841, British Patent 874130, German Federal Patent No. 1077430, 1105179, 1081917, and 11111394). , Japanese Patent Laid-Open No. 93729/1981). Of these graft polyols, graft polyols having an average number of functional groups of 2.5 to 4.0 and a graft ratio of 4 to 20% by weight are particularly used in the present invention.

If the average number of functional groups of the graft polyols used is 2.5 or less, the resulting microcellular polyurethane-based elastomers are inadequate because they exhibit a very high compression set. Conversely, in the case of 4.0 or more, the urethane-based elastomer which is a product shows a tendency to harden. The preferred average number of functional groups of the graft polyols is in the range of 2.5 to 3.0. When the graft ratio of the graft polyol is 4% by weight or less, the compression set is deteriorated. When the graft polyol is 20% by weight or more, the viscosity of the liquid is increased and moldability is greatly reduced. Therefore, the graft ratio of the graft polyol is conveniently in the range of 4 to 20% by weight, in particular 5 to 15% by weight. The "graft ratio" of the total vinyl monomers added here means the ratio of vinyl monomer graft polymerized to the polyol to the weight of the polyol mentioned above.

As the polyol serving as the stem of the graft polyol (b), it is advantageous to use an average molecular weight of 2,500 to 8,500, preferably 4,000 to 7,000 and a hydroxyl value of 20 to 67, preferably 24 to 50. For example, polyalkylene ether glycol having an average molecular weight of 4,800 obtained by addition polymerization of ethylene oxide and / or propylene oxide to glycerin can be used.

Examples of vinyl monomers grafted to such polyols include olefins such as styrene, vinyltoluene, 1-butene, 2-hexene, 1,4-hexadiene, 1,3-butadiene and 3-pentene; Vinyl halides such as vinyl chloride and vinylidene chloride; Ethylenically unsaturated carboxylic acids such as acrylic acid and methacrylic acid or derivatives thereof (eg, alkyl esters); Vinyl acetate; Acrylonitrile; Etc. can be mentioned. These can be used individually or in combination of 2 or more types of monomers.

The grafting of the vinyl monomer or monomer to the polyol can be accomplished by radical polymerization in a known manner in the presence of the polyol. Examples of useful radical polymerization catalysts include peroxide-type, azu-type or redox-type polymerization initiators or metal compound catalysts and the like. The graft polyols thus obtained usually have an average molecular weight of 2,500 to 8,500, preferably 4,000 to 7,000.

Particularly preferred graft polyols in the present invention are acrylonitrile and styrene and polypropylene ether glycol having an average molecular weight of 5,100 and an average number of functional groups of 3, using azobisisobutylonitrile as a polymerization initiator in a high pressure brush at 120 ° C. And one obtained by graft polymerization for 8 hours.

"Liquidpoly butadiene polyol" (c) refers to liquid butadiene homopolymers or copolymers having terminally reactive hydroxyl groups, especially allyl-type primary hydroxyl groups, and are known (see, for example, US Pat. Nos. 3,342,66 and 3674743). . These are hydrogen peroxide which is a polymerization catalyst for 1,3-butadiene alone or C ₂ -C ₁₂ ethylenically unsaturated monomers such as styrene, acrylonitrile, vinyl acetate, etc. in amounts not exceeding 75% by weight of 1,3-butadiene and total monomers. It can be prepared by radical addition polymerization under.

According to the invention, in particular liquid polybutadiene polyols having an average number of functional groups of 2.0 to 3.0 and an average molecular weight of 2,000 to 7,000 are used. When the number of functional groups in the liquid polybutadiene polyols used is 2.0 or less, high spring constant products are difficult to obtain. Moreover, such products tend to have greater compression set. In addition, the mixing property when the polymer polyol (a) and the graft polyol (b) are mixed and used is impaired, and the moldability is also significantly reduced. Conversely, when the number of functional groups exceeds 3.0, the product lacks elasticity, breaks well, water resistance and alkali resistance do not improve, and fatigue resistance is significantly reduced.

It is convenient that the average number of functional groups of the liquid polybutadiene polyol (c) is 2.0 to 3.0, in particular 2.1 to 2.8. In addition, when the average molecular weight of the liquid polybutadiene polyol is 2,000 or less, the rate of change of strength and elongation used as a standard of water resistance and alkali resistance is significantly increased, and fatigue resistance and compression set are significantly decreased. Formability decreases. On the other hand, when it exceeds 7,000, the viscosity of the liquid rises too much, and the miscibility with the polyisocyanate (d) is impaired. Therefore, the resulting elastomer not only exhibits low tensile strength, but also does not have a high spring constant, and exhibits low free bubble-forming ability. Therefore, liquid polybutadiene polyols having an average molecular weight of 2,000 to 7,000, preferably 2,400 to 5,000, are suitable.

Furthermore, liquid polybutadiene polyols (c) having a hydroxyl content of 0.5 to 1.0 milliequivalents / g and an iodine value of 400 to 500 are preferred.

Particularly preferred liquid polybutadiene polyols are, for example, hydroxyl-terminated butadiene homopolymers (e.g. poly bd R-45HT manufactured by ARCO Chemicals) having an average number of functional groups of 2.2 to 2.4 and an average molecular weight of about 2,800, and an average number of functional groups of 2.2 to 2.4 A hydroxyl-terminated butadiene / styrene copolymer of 2.4 and an average molecular weight of about 3,500 (e.g., poly bd CS-15 by ARCO Chemicals), and a hydroxyl- having an average molecular weight of 2.5 to 2.8 and an average molecular weight of about 4450 Terminal butadiene / acrylonitrile copolymers (e.g., poly bd CN-15 from ARCo Chemicals).

The mixing ratios of the three types of polyol components (a), (b) and (c) described above can be varied in a wide range depending on the physical properties required for the finally produced urethane elastomer. Usually, it is convenient to select the mixing ratio of the following ranges based on the total amount of the three components (a), (b) and (c).

Further, the weight mixing ratio of the graft polyol (b) to the polybutadiene polyol (c), that is, (b) / (c) is usually 1 / 0.5 to 1 / 1.5, preferably 1 / 0.8 to 1 / 1.2. The weight mixing ratio of the polyether polyol (a) to the polybutadiene polyol (c), namely (a) / (c), is 3/1 to 15/1, preferably 4/1 to 10/1.

According to the present invention, urethane elastomers obtained by the combined use of vinyl monomer-grafted polyols (b) and liquid polybutadiene polyols (c) exhibit new effects not obtainable with conventional elastomers. That is, it has a high spring constant, does not show a decrease in tensile strength due to a decrease in bulk density even under limited deformation conditions such as the use of high loads and direct-type sleepers, moreover, its compressive permanent rate is small, and the water resistance and alkali resistance tests The rate of change of intensity and elongation shown at is small.

Graft polymer (b) and liquid polybutadiene to obtain low strength and elongation rate of change, good vibration absorption and moderate spring constant and elongation in high quality independent bubbles, water resistance and alkali resistance tests, which are characteristic of the present invention. Preferred blending of the polyol (c) is a graft polyol having a graft ratio of 10 to 15%, an average molecular weight of 5,000 to 7,000, and an average number of functional groups of 3.0 to 3.8, a liquid having an average molecular weight of 2,500 to 4,800 and an average number of functional groups of 2.2 to 2.8. The polybutadiene polyol is mixed so that the mixing ratio of (b) to (c) is from 1: 0.5 to 1: 1.5, preferably from 1: 1.0 to 1: 1.2. Furthermore, the best synergy can be obtained when the liquid polybutadiene polyol is mixed in an amount of 3 to 30% by weight based on the total weight of the three types of polyol components (a), (b) and (c).

As the organic polyisocyanate (d) reacting with the polyol components (a), (b) and (c), those generally used in the production of urethane elastomers may be used. For example, polyisocyanates such as 4,4'-diphenylmethane diisocyanate (M.D.I.), naphthylene diisocyanate, tolylene diisocyanate and hexamethylene diisocyanate may be used alone or in combination. In addition, the polyisocyanate (d) may be used in the form of a precursor obtained by condensation with the aforementioned polyhydric alcohol, that is, in the form of a prepolymer or a se-prepolymer.

In addition, the amount of organic polyisocyanate (d) is within the stoichiometric range equivalent to the total active hydrogen-containing component (polyol component, chain extender, etc.) reacted with the isocyanate residue (-NCO) present in the effervescent stock solution of the urethane elastomer. 10%, that is, in the range of 90 to 110, preferably 95 to 105 in terms of NCO index.

The chain extender (e) used in the formation of the polyurethane elastomer in the present invention reacts with the organopolyisocyanate (d) to form a hard branch which is originally hydrogen-bonded by a urethane bond or urea bond. Therefore, chain extenders are an important factor in controlling the elasticity characteristic of polyurethane elastomer products. According to the invention, relatively low molecular weight actually difunctional active hydrogen-containing compounds are advantageously used as chain extenders. Examples of such chain extenders (e) include C ₂ -C ₁₀ diols, such as ethylene glycol, propylene glycol, propanediol, butanediol, hydroquinone and hydroxyethylquinone ether, and methylenebis (O-chloroaniline), querol, Amines such as ethylene diamine and triethanol amine. These can be used individually or in combination.

According to the study of the inventors, when the chain extender (e) is used in combination with the above-described polyol components (a), (b) and (c), the five components (a), (b), (c), (d) ) and (e) it has been found that the total amount is to use a 0.3 × 10 ^-3 mol /g~1.5×10 ^-3 claim chain extender of moles / g concentration (e) on the basis of fitness. At lower temperatures the chain extension effect is insufficient and the resulting foamed polyurethane elastomers generally tend to have low strength. Also at concentrations higher than 1.5 × 10 ⁻³ mol / g, the hydrogen-to-hydrogen bonds increase too much and the resulting elastomeric polymer has an improved strength but very hard. This property is rather undesirable for use in the present invention where the product is exposed to compression set and subjected to repeated compressive forces. A preferred concentration range of the chain extender is 0.5 × 10 ^-3 mol /g~1.2×10 ^-3 mol / g.

As the urethane-forming catalyst (g), those generally used in the urethane-forming reaction, for example, tertiary amine compounds, organometallic compounds and the like can be used. Specific examples include triethylene diamine, diazabicycloundecene, n-methyl morpholine, N, N-dimethylethanolamine; Tin octylate and dibutyl tin laurate. The amount of catalyst is not limited and may be varied in a wide range depending on the reaction rate required. However, it is necessary to appropriately control the degree of foaming of the urethane elastomer and the ambient conditions (temperature, humidity, etc.). Since the adjustment of the amount of catalyst is a conventional general technique, selection of an appropriate amount is easy.

According to the invention, foamed polyurethane elastomers are used. Known blowing agents such as water and halogenated hydrocarbons (e.g. trichlorofluoromethane, methylene chloride, etc.) may be used as blowing agents (f) used in the preparation of the foams. Although the degree of foaming of the urethane polymer required in the present invention is not particularly limited, it is important that the product has a relatively low foam as compared to conventional urethane foams. Usually, the degree of foaming expressed in bulk density is advantageously 0.4 to 0.75 g / cm 3, preferably 0.55 to 0.7 g / cm 3. The amount and / or degree of foaming of the blowing agent (f) can be adjusted by making the bulk density of the resulting urethane elastomer to a value within the above range.

In addition to the above, the expandable stock solution of the urethane elastomer according to the present invention may be used if necessary, such as foam stabilizers (e.g. silicone surface active agents), pigments (e.g. carbon black, titanium oxide, etc.), dyes (e.g. indanthrene dyes), other fillers ( Eg mineral tar, glass fiber, asbestos fiber, nylon fiber, vinyl chloride fiber, polyester fiber, acrylic fiber, inorganic or organic staple fiber such as natural or synthetic rubber powder; silicon sand, etc.).

In the microcellular polyurethane elastomer used as the dustproof agent in the present invention, the spring constant per unit area is about 0.2 ton / cm / 100 cm 2 or more, especially 0.7 ton / cm / 100 cm 2 to 2 ton / cm / 100 cm 2 desirable. The spring constant within the above range can be obtained by appropriately selecting the composition and bulk density of the microcellular polyurethane elastomer having a thickness of 5 to 100 mm used for the dustproof layer.

Microcellular polyurethane elastomeric coating materials have a good effect when molded into foam sleepers and foamed and finally attached to them. Alternatively, the dust-proofing effect can be effectively exhibited by molding into a concrete sleeper and attaching it to the sleeper. That is, the coating layer may be attached to the lower part of the concrete sleeper with an adhesive, or may form a box-shaped polyurethane elastomer molding agent to insert the concrete sleeper.

However, according to the present invention, the most preferred embodiment of forming the coating layer is to inject a stock solution for polyurethane elastomer around the lower part of the concrete sleeper into a box of a constant size and foam the liquid to integrate and foam the sleeper It was found that the former consisted of attaching and covering the latter.

And, according to another aspect of the present invention, the concrete sleeper is fixed to the mold such that the bottom and at least the lower sides of the two sides are completely wrapped in the mold in which some space remains from the bottom and the side walls, and the poly After injecting the foaming stock solution of the urethane elastomer, the stock solution is foamed and cured to form a direct sleeper coated with a microcellular polyurethane elastomer that is firmly attached to the lower part of the sleeper. A method is provided.

According to the present invention described above it is possible to easily make a direct sleeper using an atmospheric injection type simple mold, and the molded article can be demolded from the mold after about 2 hours from the injection takes only about 1 minute. Therefore, the production efficiency is dramatically increased. In addition, according to the integrated molding method, the concrete sleeper and the polyurethane elastomer coating material are strongly bonded to each other, so that the use of an adhesive primer is unnecessary and peeling hardly occurs.

According to the method of the present invention, the above-mentioned components of the polyurethane elastomer foam stock solution are conventionally mixed well just before injection and injected into the integrated molding mold of the direct sleeper. The mold is fixed to the concrete sleeper in such a way that the bottom and at least the underside (near the bottom) of the sleeper are essentially completely enclosed by the mold, leaving a slight gap, to enable the integrated molding of the direct sleeper. One embodiment of the mixing device is shown in FIGS. 6 and 7. The box-shaped mold 13 attaches to the concrete sleeper 1 as shown in FIGS. 6 and 7 so that the bottom 11 and the underside 12 of the sleeper 1 are essentially completely enclosed. In this case there is a space s of width w and w 'between the bottom 11 of the sleeper 1 and the inner bottom of the mold and between the side 12 of the sleeper 1 and the relative inner side of the mold, respectively, where w and w' Corresponds to the required thickness of the coating layer. Mold 13 should essentially completely wrap the concrete sleeper 1 so as to fundamentally prevent the leakage of the polyurethane elastomer stock solution to be injected into the space s. In the mold, a projection is formed at a position corresponding to the through holes 3, 3 ', 3 "... of the concrete sleeper so as to form the through holes in the coating layer as well.

The height h in which the mold 13 wraps the side 12 of the concrete body 1 is given to the height h of the covering layer which covers the side 12 of the sleeper 1.

After preparing the mold as described above, the foamable liquid of the raw polyurethane elastomer is injected into the space s through the inlet 14 provided at the appropriate position of the mold 13. According to the present inventors, the combination of the concrete sleeper and the mold 13 has the side with the inlet 14 as the lower side and the side with the mold 15 as the side with the inlet 14 as normal, and the bottom 11 is essentially vertical. Inflation is most advantageous when in a standing position.

8 is a flowchart showing the operation of injecting the raw foamable liquid of the polyurethane elastomer into the mold 13. The concrete sleeper 1 on which the mold 13 is placed is placed such that its bottom 11 is almost vertical as described above, and the stock solution is injected through the hole 14 located in the lower part of the mold 13. As the injection proceeds, air in the space s is released through the deaerator 15.

The foamable liquid solution of this polyurethane elastomer is, for example, liquid A composed of polyether polyol, graft polyol, liquid polybutadiene polyol, chain extender, blowing agent, urethanization catalyst and foam stabilizer, and liquid B composed of organic polyisocyanate. In the tanks 20 and 20 ', respectively, from which they can be made by mixing the two liquids well by feeding them to the two-liquid mixer 22 via measuring pumps 21 and 21', respectively. This liquid mixture is led to inlet 14 through conduit 23 with terminal valve 24.

Typical compositions of liquids A and B commonly used in the present invention are as follows.

Composition weight part of liquid A

Polyether Polyol 100

(Glycerine / propylene oxide / ethylene

Oxide hybridized adduct

Average number of functional groups: 3 to 4

Average molecular weight: 2,000-7,000).

Graft Polyols 10-40

[Azobisisobutyronitrile (polymerization initiator)

Acrylonitrile and styrene in the presence of glycerin /

Propylene Oxide / Ethylene Oxide Hybrid Polymerized

By graft polymerization to an adduct (average molecular weight = 5100)

Made polymer polyols;

Average number of functional groups = 3

Graft Ratio = 10%

Average molecular weight = 6000]

Liquid hydroxyl-terminated

Polybutadiene polyol 5-20

Ethylene Glycol 5-15

Water 1.0-1.5

Triethylene diamine 0.5-2.0

Composition NCO Index of Liquid B

Polyisocyanate Polyol Propolymer 90-110

[Example: glycerin / propylene oxide /

4,4'- with ethylene oxide hybridized adduct

Isocyanate- of diphenylmethane diisocyanate

Terminal precursor precondensation product

(Average molecular weight = 6500, average number of functional groups = 3);

Free NCO content = 16% by weight]

Injection of the foamed stock solution into the mold is usually 1-100 kg / min; Preferably it is made into the speed | rate of 30-60 kg / min. The injection amount ranges from 1/3 to 9/10 of the total volume of said space in the mold, depending on the degree of foaming desired. The foamable stock solution of the injected polyurethane elastomer is also foamed and cured. Foaming and curing usually proceed at room temperature, but if necessary, by heating up to about 70 ° C. Foaming and curing are usually completed within 1 to 2 hours and the mold is demolded from the concrete sleepers.

Thus a direct sleeper coated with a microcellular polyurethane elastomer can be obtained. Cells of microcellular polyurethane elastomeric sheaths molded integrally with concrete sleepers are usually free-standing bubbles. Preferred physical properties of the elastomer are as follows:

(1) Bulk density: 0.4 to 0.75 g / cm 3, preferably 0.55 to 0.7 g / cm 3

(2) Compression permanent rate: 15% or less, preferably 5% or less

(3) Spring constant: 0.2 ton / cm / 100 cm 2 or more, preferably 0.7 to 2 ton / cm / 100 cm 2

(4) Tensile strength: 5.0 kg / cm 2 or more, preferably 10 kg / cm 2 or more.

(5) Tensile elongation: 100% or more

(6) water resistance: tensile strength change rate within ± 20%, preferably ± 10%; Change in tensile elongation within ± 20%, preferably ± 10%;

(7) alkali resistance: tensile strength change rate within ± 20%, preferably ± 10%; Change in tensile elongation within ± 20%, preferably ± 10%;

(8) Fatigue resistance: fatigue amount 1.0 mm or less, preferably 0.2 mm or less

(9) Independent bubble formation rate: 90% or more, preferably 99-100%

As described above, the direct-type sleepers prepared according to the present invention are the microcellular polyurethane elastomers attached to the lower parts of the sleepers 1 by the concrete sleepers 1 and the total molding as shown in FIGS. 1 to 3. It consists of the cladding material 2.

는 약 1∼3㎜이고, 실린더형 부분의 길이

는 약 0.3∼2㎜가 좋다.According to the study of the present inventors, it has been found that the direct sleepers can be easily demoulded from the mold when each of the degassing 15 of the mold 13 has a cross section of an inverted truncated cone extending outward as shown in FIG. The true angle α of the inner wall of each degassing apparatus is usually 30 to 60 °, in particular about 45 °. Inner diameter of outgassing 15 of mold 13

Is about 1 to 3 mm and the length of the cylindrical part

Is preferably about 0.3 to 2 mm.

As described above, the direct sleeper of the present invention shows an excellent translational effect and dramatically reduces vibration and noise when used as a sleeper of a high-speed train track, thereby reducing environmental pollution due to noise and vibration around the track.

In addition, the direct-type sleepers of the present invention can be laid with high precision and easy operation at the time of laying the track, greatly reducing labor costs and working time.

In addition, according to a preferred embodiment of the method of the present invention, the microcellular polyurethane elastomeric coating material foams and molds in aggregate with the concrete sleeper, thus demonstrating a strong adhesion of the coating to the concrete sleeper. This high adhesion is indeed a great practical advantage, since vibration dampers are usually needed to accurately transmit vibrations, block vibrations, and absorb vibrations.

Furthermore, according to the present invention, the direct-type sleepers (elastic-coated sleepers) can be easily manufactured using a relatively simple device, and thus manufacturing cost and energy consumption can be reduced. This direct sleeper and its manufacturing method will be described in more detail with reference to the following working examples.

EXAMPLE

인 탈기구 15를 갖는 주형 13에 400㎜×2,000㎜×200㎜ 콘크리트 침목체 1을 고정한다. 피복층의 두께(w, w')는 25㎜이다. 제6도에는 보이지 않지만, 제2도에 보인바와 같은 피복층의 바닥면 중앙부에 폭 300㎜ 및 깊이 15㎜의 침하 또는 홈을 형성하기에 적합한 부분에서 주형에 격벽을 설치하였다. 제8도에 보인 장치를 사용하여 하기 규정한 조성의 액체 A 및 B를 혼합기 22에서 회전속도 6,000rpm으로 혼합하고, 이 혼합물을 주형의 하부의 공간에 주입하였다. 이것을 실온에서 2시간동안 방치하여 침목을 주형으로부터 분리하였다. 생성된 직결형 침목을 구성하는 폴리우레탄 탄성 중합체 피복의 물리적 특성 및 액체 A 및 B의 조성을 하기에 보였다.In the same way as in Figure 6,

A 400 mm × 2,000 mm × 200 mm concrete sleeper 1 is fixed to a mold 13 having a drawer 15. The thickness (w, w ') of a coating layer is 25 mm. Although not shown in FIG. 6, the partition wall was provided in the mold at a portion suitable for forming a settlement or groove 300 mm wide and 15 mm deep in the center of the bottom surface of the coating layer as shown in FIG. Using the apparatus shown in FIG. 8, liquids A and B of the composition stipulated below were mixed in mixer 22 at a rotational speed of 6,000 rpm and the mixture was injected into the space below the mold. It was left at room temperature for 2 hours to separate the sleepers from the mold. The physical properties of the polyurethane elastomeric coatings and the composition of liquids A and B which constitute the resulting direct sleepers are shown below.

Physical properties were measured by the following method.

(1) Bulk density: measured according to JIS Z 8807 "Capacitance measuring method".

(2) Compression permanent rate: Measured according to JIS K 6301 "10, Compression permanent rate test".

(3) Spring constant: Measured according to JIS K 6385 "5, Static Spring Constant Test" (Spring constant of 425 kg to 10 cm x 10 cm x 2.5 cm sample and between 100 and 400 kg on the load removal curve. Is measured).

(4) Tensile strength and tensile elongation: Dumbbell test piece No. 1 measured according to JIS K 6301 "3, tensile test method".

(5) Water resistance: The same test specimen No. 1 as used for tensile strength test is immersed in distilled or ion-exchanged water for 96 hours and gently wiped to perform tensile test strength test immediately. The rate of change from the value before aging is measured.

(6) Alkali resistance: The same test method as above is used except that the immersion liquid is 1% aqueous solution (caustic / caustic soda = 1: 1) and the immersion temperature is 50 ° C.

(7) Fatigue resistance: measured according to SRIS (Standard Evaluation of Japan Rubber Association) 3502 (Test conditions: Voltage measurement 5mm, Vibration width 4mm, Vibration period 5Hz, Repeat 1 × 10 ⁶ , and test specimen size 50 × 50 25 mm).

(8) Independent foamability: measured according to ASTM D2856-70A.

Example 1

Composition weight part of liquid A

Polyether Polyol (I) 35

(Glycerine / propylene oxide / ethylene

Oxide hybridized adduct

Average number of functional groups = 3,

Average molecular weight = 3000)

Polyether Polyols 40

(Glycerine / pentaerythritol / propylene

Oxide / Ethylene Oxide Hybrid Polymerized Additives

Average number of functional groups = 3.7

Average molecular weight = 5,700)

Graft Polyols (II) 15

Azobis isobutyronitrile (polymerization initiator)

Acrylonitrile and styrene in the presence of glycerin /

Propylene Oxide / Ethylene Oxide Hybrid Polymerized Additives

Polymer obtained by graft polymerization on (Average molecular weight = 5100)

Polyol

Average number of functional groups = 3

Graft Ratio = 10%

Average molecular weight = 6000]

Hydroxyl-terminated Liquid Polybutadiene Polyol 15

(Average number of functional groups = 2.5

Average molecular weight = 2750)

Ethylene Glycol 7

Water 0.53

Triethylene Diamine 0.7

Composition NCO Index of Liquid B

Polyisocyanate / Polyol Free Polymer 100

[4,4'-diphenylmethane diisocyanate and average

Glycerine / propylene oxide / with molecular weight 6500

Isocyanates-Hybrid Polymeric Additives of Ethylene Oxide

Terminal precursor condensation products

(Average number of functional groups = 3,

Average molecular weight = 6500)

Free NCO content = 16% by weight

Physical properties:

Bulk Density: 0.63g / cm3

Spring constant: 1.5tf / cm / 100㎠

Compression permanent rate: 2.0%

Tensile Strength: 13.0㎏ / ㎠

Tensile Elongation: 145%

Water resistance

Tensile Strength Change Rate: -0.9%

Tensile Elongation Change Rate: -0.3%

Alkali resistance

Tensile Strength Change Rate: -0.3%

Tensile Elongation Change: -0.2%

Fatigue Resistance: Fatigue 0.26㎜

Independent bubbleability: Independent bubble formation rate 100%

Example 2

Composition weight part of liquid A

Polyether Polyols (II) 52

(Glycerine / pentaerythritol / propylene

Oxide / ethylene oxide hybrid polymerization adduct

Average number of functional groups = 3.7

Average molecular weight = 5700)

Graft Polyols 15

[Azobisisobutyronitrile (polymerization initiator)

Acrylonitrile and styrene in the presence of glycerin /

Propylene Oxide / Ethylene Oxide Hybrid Polymerization

Graft polymerization to adduct (average molecular weight = 5100)

Polymer obtained);

Average number of functional groups = 3

Graft Ratio = 10%

Average molecular weight = 6000]

Hydroxyl-terminated Liquid Polybutadiene Homopolyol 12

(Average number of functional groups = 2.3

Average molecular weight = 4700

Hydroxyl content = 0.5

Millie equivalent / g

Iodine Value = 450)

Ethylene Glycol 5.7

Water 0.48

Triethylene Diamine 0.7

Composition NCO Index of Liquid B

Polyisocyanate / Polyol Prepolymer

[4,4'-diphenylmethane diisocyanate and

Glycerine / Propylene Oxide / Ethylene Oxide

Iso of hybrid polymerization adduct (average molecular weight = 6500)

Cyanate-terminated precursor condensation product

Free NCO content = 16% by weight]

Physical properties

Bulk Density: 0.69g / cm3

Spring constant: 0.98tf / cm / 100㎠

Compression permanent rate: 3.8%

Tensile Strength: 1.49㎏ / ㎠

Tensile Elongation: 210%

Water resistance

Tensile Strength Change Rate: -3.7%

Tensile Elongation Change Rate: -4.3%

Alkali Resistance:

Tensile Strength Change Rate: -2.2%

Tensile Elongation Change: -4.1%

Fatigue Resistance: Fatigue 0.16㎜

Independent bubbleability: Independent bubble formation rate 99.9%

The direct sleepers prepared in Example 1 were placed on test lines as shown in FIGS. 10a and 10b and the effects were measured as follows.

Before starting commercial operation, a part of the conventional gravel track was removed from the test track installed in Tohoku Shinkansen, and the direct sleepers of Example 1 were laid at 160 m in length. For the test, the Shinkansen train ran at a speed of 200-210 km / h.

As shown in FIG. 10B, the vibration and noise of the train traveling on the track were measured at two points V ₁ and V ₂ (vibration) and three points A, B and C (noise), respectively. The vibration was measured by a barium titanate accelerometer. The noise was measured with a normal sound level meter.

The vibration- and noise-reducing effects of the test track placed on the direct sleepers of Example 1 as compared to the conventional gravel track are as follows:

The vibration at the point V ₁ (acceleration of the rail) is almost the same as that of the elastic gravel track with the gravel bedside, but the vibration at the point V ₂ (acceleration of the bottom slab of the elevated structure) is reduced by 7 dB. Compared to the elastic gravel track with gravel bedside, the noise is reduced by 7dB (A) at point A (0.3m below the floor slab) and by 5dB (A) at point B (5.0m below the floor slab), At point C (1.2 m above ground, below the elevated structure), it was reduced by 4 dB (A).

Claims (23)

An elastic covering material for a direct sleeper composed of a microcellular polyurethane elastomer that adheres to a concrete sleeper and a lower part of the sleeper to form a total body, wherein the microcellular polyurethane elastomer has a urethane bond and its volume An elastic coating material having a density of 0.4 to 0.75 g / cm 3 and made mainly from an expandable stock solution of a urethane elastomer composed of: (a) polyether polyols having an average number of functional groups of 2.5 to 4.5 and an average molecular weight of 2,000 to 8,500; (b) vinyl monomer-grafted polyols having an average number of functional groups of 2.5 to 4.5 and a graft ratio of 4 to 20% by weight, (c) liquid polybutadiene polyols having hydroxyl end group (s) and having an average number of functional groups of 2.0 to 3.0 and an average molecular weight of 2,000 to 7,000, (d) organic polyisocyanates, (e) chain extenders, (f) blowing agents, and (g) urethanization catalyst In the above configuration, the NCO index is in the range of 90 to 110, and the concentration of the chain extender with respect to the total amount of the five components (a), (b), (c), (d) and (e) is 0.3 × 10 ⁻³ to 1.5 × 10 ⁻³ mol / g. The elastic coating material according to claim 1, wherein the average number of functional groups of the polyether polyol (a) is 2.8 to 4.0 and the average molecular weight is 3,000 to 6,500. The polyether polyol (a) is a glycerin / propylene oxide / ethylene oxide hybrid polymerization adduct (average number of functional groups = 3.0. Average molecular weight = 3,000), propylene glycol / propylene oxide / ethylene oxide hybrid polymerization adduct. (Average number of functional groups = 2.0, average molecular weight = 4,800), and glycerin / pentaerythritol / propylene oxide / ethylene oxide hybrid polymerization adduct (average number of functional groups = 3.7, average molecular weight = 5700) clothing material. The elastic coating material according to claim 1, wherein the vinyl monomer-grafted polyol (b) has an average number of functional groups of 3.0 to 3.8 and a graft ratio of 5 to 17% by weight. The vinyl monomer-grafted polyol (b) of claim 1 has an average molecular weight of 2,500 to 8,500 and a hydroxyl value of 20 to 67, and styrene, vinyl toluene, 1-butene, 2-hexene, 1,4-hexa. Polyols grafted with at least one vinyl monomer selected from the group consisting of dienes, 1,3-butadiene, 3-pentene, vinyl chloride, vinylidene chloride, acrylic acid or methacrylic acid, alkyl esters thereof, vinyl acetate and acrylonitrile Elastic covering material. The elastic coating material according to claim 1, wherein the vinyl monomer-grafted polyol (b) has an average molecular weight of 4,000 to 7,000. The elastic coating of claim 1, wherein the vinyl monomer-grafted polyol (b) is a polypropylene ether glycol having an average molecular weight of about 5,100, an average number of functional groups of about 3, and grafted acrylonitrile and styrene. The elastic coating material according to claim 1, wherein the average number of functional groups of the liquid polybutadiene polyol (c) is 2.1 to 2.8 and the average molecular weight is 2400 to 5000. The elastic coating material according to claim 1, wherein the hydroxyl content of the liquid polybutadiene polyol (c) is 0.5 to 1.0 milliequivalents / g. The method of claim 1, wherein the liquid poly butadiene polyol (c) is a hydroxyl-terminated butadiene homopolymer having an average number of functional groups of 2.2 to 2.4 and an average molecular weight of about 2800, a hydroxyl number of 2.2 to 2.4 and an average molecular weight of about 3500 An elastic coating material selected from the group consisting of terminal butadiene / styrene interpolymers and hydroxyl-terminal butadiene / acrylonitrile interpolymers having an average number of functional groups of 2.5 to 2.8 and an average molecular weight of about 4500. The polyether polyol (a) is 15 to 95% by weight, and the vinyl monomer-grafted polyol (b) is 1 to 60% by weight based on the total weight of the polyol components (a), (b) and (c). %, And 1 to 50% by weight of the liquid polybutadiene polyol (c) is used. The elastic coating material according to claim 1, wherein the organopolyisocyanate (d) is selected from the group consisting of 4,4'-diphenylmethane diisocyanate, naphthylene diisocyanate, tolylene diisocyanate and hexamethylene diisocyanate. The chain extender (e) of claim 1, wherein the chain extender (e) is ethylene glycol, propylene glycol, propane diol, butane diol, hydroquinone, hydroxy ethyl quinone ether, methylene bis- (o-dichloroaniline), querol, ethylene diamine and triethanol Elastic coating material selected from the group consisting of amines. The concentration of the chain extender (e) contained in the expandable stock solution is 0.5 × 10 ^{−3, based} on the total amount of the five components (a), (b), (c), (d) and (e). An elastic coating material which is mol / g-1.2 * 10 <^-3> mol / g. The elastic coating material according to claim 1, wherein the bulk density of the microcellular polyurethane elastomer is 0.55 to 0.7 g / cm 3. The elastic coating material according to claim 1, wherein the compressive permanentity of the microcellular polyurethane elastomer is 15% or less. The elastic coating material according to claim 1, wherein the spring constant of the microcellular polyurethane elastomer is 0.2 ton / cm / 100 cm 2 or more. The elastic coating material according to claim 1, wherein the microcellular polyurethane elastomer has a tensile strength of 5.0 kg / cm 2 or more and a tensile elongation of 100% or more. The elastic coating material of Claim 1 whose thickness of a coating layer is 8 mm or more. The elastic coating material according to claim 1, wherein there is a settlement portion at the center of the bottom of the coating layer, and the settlement portion is filled with soft synthetic resin foam. The elastic coating material according to claim 20, wherein the synthetic resin foam is an independent bubble, a crosslinked polyethylene foam. The process according to claim 1, wherein a foaming stock solution of polyurethane elastomer is injected from the lower side into the mold surrounding the lower part of the sleeper and the foaming and curing of the liquid is carried out and the coating layer is adhered to the lower part of the concrete sleeper. Elastic covering material. 21. The resilient cladding according to claim 20, wherein the length of the settlement portion is 1/4 to 1/2 of that of the concrete sleeper.

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