JPH0422170B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to an elastic covering for a direct-coupled elastic sleeper made of a low-foam urethane elastomer having certain urethane bonds. More specifically, a railway track that can exhibit excellent vibration isolation, vibration damping, vibration absorption, and/or vibration damping effects even under conditions of high load and restrained deformation on railway tracks on which long trains run at ultrahigh speeds. This invention relates to an elastic covering material for a direct-coupled elastic sleeper. In recent years, as railways have become faster, concrete sleepers or slabs are being used instead of the conventional ballasted tracks from the viewpoint of train running stability, ease of security maintenance, and shortening of construction time. Direct-coupled tracks, which are constructed directly on solid roadbed surfaces, are often used. Among them, from the perspective of reducing vibration and noise, in the method of embedding and fixing sleepers with concrete on the concrete roadbed surface (directly attached type sleepers), the vibration isolating material used in the middle is firmly held by the filled concrete. Since the vibration isolating material is restrained and free deformation is prevented, this vibration isolating material has an excellent bond that firmly adheres to concrete sleepers even when such free deformation is restrained, without increasing the spring constant. It is necessary to use an elastic material that exhibits the effect of reducing vibration transmission and suppressing noise generation. In particular, in the case of railway tracks where long trains run at extremely high speeds, the physical properties required for the elastic sheathing of elastic sleepers are even more severe, and according to current specifications, the elastic sheathing Required physical properties include, for example, compression set: 15% or less Spring constant: 0.2 to 2 ton/cm・100cm ² Tensile strength: 5 Kgf/cm ² or more Tensile elongation: 100% or more Water resistance (rate of change in tensile strength): ± Within 20% (Tensile elongation change rate): Within ±20% Fatigue resistance: Settling amount is 1.0 mm or less, and it is required to use a material that satisfies all of these physical property requirements at the same time. . Moreover, one of the important requirements is that the elastic covering material firmly adheres to the concrete sleepers and the filled concrete and does not peel off even under repeated compression caused by intermittent train running. The present inventors have previously developed an elastic coating material that satisfies these requirements with an average number of functional groups of 2.5 to 3.5.
and a polyhydric alcohol with a number average molecular weight of about 4,500 to about 8,500, an organic polyisocyanate, a chain extender,
It consists of a urethanization catalyst and a blowing agent, and a chain extender of 0.2% per unit weight of the urethane elastomer.
The bulk density produced from a urethane elastomer foam stock solution containing a concentration of ×10 ^-3 to 1.0 × 10 ^-3 mol/g is
We discovered that a low foaming urethane elastomer with a foam density of 0.3 to 0.9 g/cm ³ was suitable and proposed it (Japanese Patent Application Laid-Open No. 1983-1999).
(See Publication No. 130754). The low-foam urethane elastomer proposed earlier satisfies the above specifications and is actually applied to straight sections of high-speed railway tracks. It goes without saying that even in the case of an elastic covering material made of such a low-foaming urethane elastomer, it is preferable from an economic point of view to lower the bulk density to reduce the amount of raw materials used. However, there is a drawback that lowering the bulk density lowers the spring constant. However, especially in curved sections of high-speed railway tracks, large centrifugal forces are applied, and the elastic covering material is greatly compressed. As a result, a void is created between the elastic covering material and the filled concrete, and there is a risk that moisture and dust may enter there. Therefore, it is not possible to use the low-foam urethane elastomer simply by increasing its foaming degree and lowering its bulk density. I can't. For example, the bulk density of the low foam urethane elastomer is 0.7.
g/ ^cm3 or less, and at the same time the spring constant is 1.0tf/cm・
If you try to maintain it at around 100cm ² , there is a problem that the compression set will increase. Therefore, the present inventors conducted intensive research in search of a foamed urethane elastomer whose compression set does not substantially increase even when the bulk density is lowered, and as a result, the present invention was completed. According to the present invention, (a) a polyether polyol having an average number of functional groups of 2.5 to 4.5 and a number average molecular weight of 2000 to 8500; (b) a polyether polyol having an average number of functional groups of 2.5 to 4.0 and a grafting rate of 4 to 4. consisting essentially of 20% by weight vinyl monomer grafted polyol, (c) organic polyisocyanate, (d) chain extender, (e) blowing agent, and (f) urethanization catalyst, with an NCO index of 90 to 110.
and the chain extender is within the range of (a), (b),
0.3× based on the total amount of the four components (c) and (d)
The bulk density prepared from a urethane elastomer foam stock solution containing a concentration of 10 ^-3 to 1.5 × 10 ^-3 mol/g is
An elastic covering material for a direct-coupled elastic sleeper is provided which is made of a foamed urethane elastomer having a urethane bond of 0.4 to 0.75 g/cm ³ . The polyether polyol (a) used as one of the polyol components in the preparation of the urethane elastomer of the present invention has an average number of functional groups of 2.5 to 4.5 and a number average molecular weight of 2,000 to 8,500. The average number of functional groups of the polyether polyol used is 2.5
If it is smaller, the permanent compression set of the foamed urethane elastomer obtained therefrom becomes large, and conversely, if the average functionality exceeds 4.5, the obtained elastomer tends to become hard and the elastomer breaks when subjected to vibration compression. The danger increases,
Both are unfavorable. Therefore, the preferred average number of functional groups of the polyether polyol (a) is 2.5 to 4.5, and particularly preferably 2.8 to 4.0. Further, if the number average molecular weight of the polyether polyol (a) is less than 2000, it is difficult to obtain a foamed urethane elastomer with high vibrational energy absorption characteristics,
On the other hand, when it exceeds 8,500, the elastic properties of the resulting urethane elastomer decrease, making it more likely to undergo plastic changes, and in particular, there is a tendency for permanent compressive strain to increase. It is therefore desirable that the polyether polyol used in the present invention generally have a number average molecular weight in the range of 2,000 to 8,500, preferably 3,000 to 6,500. Such polyether polyols (a) include any commonly used polyether polyols in the preparation of urethane elastomers, specifically polyether polyols having 2 to 2 carbon atoms such as glycerin and trimethylolpropane.
Active hydrogen compounds having 6 aliphatic polyhydric alcohols or active hydrogen atoms such as ethylenediamine and diaminodiphenylmethane have 2 to 4 carbon atoms.
Examples include polyether polyols obtained by addition polymerization of lower alkylene oxides such as ethylene oxide and propylene oxide. Such polyether polyols
Typical examples of (a) include copolymer adducts of glycerin/propylene oxide/ethylene oxide (average number of functional groups = 3.0, number average molecular weight 3000); copolymer adducts of propylene glycol/propylene oxide/ethylene oxide (average functional group number = 3.0, number average molecular weight 3000); Number of groups = 2.0, number average molecular weight 4800); copolymer adduct of glycerin/pentaerythritol/propylene oxide/ethylene oxide (average number of functional groups 3.7, average molecular weight
5700) are included. The present invention uses polyether polyol (a) in combination with the polyether polyol (a) as a polyol component for forming a foamed urethane elastomer.
One major feature is the use of a vinyl monomer graft polyol with a grafting ratio of 2.5 to 4.0 and a grafting rate of 4 to 20% by weight. The "vinyl monomer graft polyol" (referred to as graft polyol) (b) used in the present invention is:
Modified polyols produced by in situ radical polymerization of vinyl monomers in the presence of conventional polyols, which are themselves known as polyol components for producing high modulus urethane foams (e.g. Japanese Patent No. 447628
No. 3033841, British Patent No. 874130 and German Patent No. 1077430, No. 1105179, No.
1081917 and 1111394, and JP-A-56-93729). Among such graft polyols, the present invention particularly uses graft polyols with an average functional group number of 2.5.
˜4.0 and a grafting percentage of 4 to 20% by weight is used. The average number of functional groups of the graft polyol used is
If it is smaller than 2.5, the resulting low foam urethane elastomer will have a large permanent compression set, which is not suitable.
Conversely, when it exceeds 4.0, the resulting urethane elastomer tends to become hard. However, the preferable range of the average number of functional groups of the graft polyol is 2.5 to 4.0.
Among them, a range of 2.5 to 3 is optimal. If the grafting rate of the graft polyol is less than 4% by weight, the compression set will be poor, and if it exceeds 20% by weight, the viscosity of the liquid will increase and the moldability will be significantly impaired. Therefore, the grafting rate of the graft polyol is 4 to 20% by weight, especially 5 to 15% by weight.
A range of % by weight is preferred. The term "grafting ratio" as used herein refers to the ratio of the vinyl monomer graft polymerized to the polyether among the vinyl monomers added, based on the weight of the polyether. The polyol forming the base of such graft polyol (b) has a number average molecular weight of 2,500 to 2,500.
8,500, preferably in the range of 4,000 to 7,000, and a hydroxyl value in the range of 20 to 67, preferably 24 to 42, is advantageously used, for example, by addition polymerizing ethylene oxide and/or propylene oxide to glycerin. Examples include polyalkylene ether glycol with a number average molecular weight of 4,800. On the other hand, examples of vinyl monomers grafted onto these polyols include styrene, vinyltoluene, 1-butene, 2-hexene, 1,4
-Olefins such as hexadiene, 1,3-butadiene, and 3-pentene; Vinyl halides such as vinyl chloride and vinylidene chloride; Elethnic unsaturated carboxylic acids such as acrylic acid and methacrylic acid or derivatives thereof (alkyl esters, etc.); Acetic acid Examples include vinyl, and these can be used alone or in combination of two or more. The grafting of the vinyl monomer to the polyol can be achieved by radical polymerization of the vinyl monomer in the presence of the polyol according to a method known per se. Examples of radical polymerization catalysts that can be used include peroxide-based, azo-based, or redox-based polymerization initiators, metal compound catalysts, and the like. The graft polyol thus obtained generally has a molecular weight of 2500 to 8500,
Preferably, it can have a number average molecular weight of 4,000 to 7,000. Therefore, as a graft polyol particularly preferably used in the present invention, for example, azobisisobutyronitrile is added to polypropylene ether glycol having a number average molecular weight of about 5100 and a functional group number of about 3 using acrylonitrile and styrene as polymerization initiators. Examples include those obtained by graft polymerization in an autoclave at 120°C for 8 hours. By using the vinyl monomer graft polyol according to the present invention, even under high load and restrained deformation conditions such as in direct-coupled elastic sleepers, a high spring constant can be achieved without reducing the tensile strength due to low bulk density. you can get
Moreover, it has been found that a unique effect not seen in conventional elastic bodies can be obtained, in that compression set can be suppressed to a small level. On the other hand, as the organic polyisocyanate (c) to be reacted with the polyol components (a) and (b) described above, any of those commonly used in the production of urethane elastomers can be used, such as 4,
4'-Diphenylmethane diisocyanate (MD
I.), naphthylene diisocyanate, tolylene diisocyanate, hexamethylene diisocyanate, and the like. These organic polyisocyanates can be used alone or as a mixture of two or more. Moreover, the polyisocyanate (c) can also be used as a precursor, ie, a prepolymer or semi-prepolymer, which is precondensed with the above-mentioned polyhydric alcohol. In any case, the amount of the organic polyisocyanate (c) to be used is determined from all active hydrogen-containing components (polyol component, chain extender, etc.) that should react with the isocyanate residue (-NCO) present in the urethane elastomer foaming stock solution. an amount stoichiometrically equal to ±10
%, that is, the NCO index can be made to fall within the range of 90 to 110. The chain extender (d) used to form the urethane elastomer in the present invention reacts with the organic polyisocyanate (c) to form hard segments mainly composed of hydrogen bonds through urethane bonds, urea bonds, etc. It is an important factor governing the elastic properties of the resulting urethane elastomer, and in the present invention, a substantially difunctional active hydrogen compound with a relatively low molecular weight is advantageous as the chain extender. used for. Examples of such chain extenders (d) include diols having 2 to 10 carbon atoms such as ethylene glycol, propylene glycol, propanediol, butanediol, hydroquinone, hydroxyethylquinone ether; methylene bis-(o- amines such as dichloroaniline), quadrol, ethylenediamine, and triethanolamine, each of which may be used alone or in combination with two
More than one species can be used in combination. According to the research of the present inventors, the above chain extender (d)
When used in combination with the above polyol components (a) and (b), the amount of the above bifunctional chain extender (d) is
Based on the total amount of the four components (a), (b), (c) and (d)
It has been found suitable to use concentrations in the range 0.3×10 ^-3 mol/g to 1.5×10 ^-3 mol/g. If the concentration is lower than this, the chain lengthening effect will not be sufficient, so the strength of the resulting foamed urethane elastomer will generally tend to be low;
At concentrations higher than 10 ^-3 mol/g, the number of hydrogen bonds increases more than necessary, which improves the strength of the resulting urethane elastomer, but tends to result in an extremely hard elastomer, resulting in compression set and repeated compression. It is less desirable for applications such as those in the present invention which are subject to stress. Thus, a preferred concentration range for the chain extender (d) is from 0.5×10 ^-3 mol/g to 1.2×10 ^-3 mol/g. In addition, as the urethanization catalyst (f), those commonly used in urethanization reactions, such as tertiary amine compounds, organometallic compounds, etc., can be used, such as triethylenediamine, diazabicycloundecene, N- methylmorpholine,
N,N-dimethylethanolamine; tin octylate, dibutyltin laurate, and the like. The amount of catalyst used is not critical and can vary over a wide range depending on the desired reaction rate, but it is necessary to adjust the amount as appropriate depending on the amount of foaming of the urethane elastomer and atmospheric conditions (temperature, humidity, etc.) It is. However, adjusting the amount of catalyst used is a common practice in the industry, and it is easy to select the appropriate amount. Furthermore, in the present invention, a foamed urethane elastomer is molded, and the blowing agent (e) used for producing this foam is a conventional blowing agent, such as water or a halogenated hydrocarbon (e.g., trichlorofluorocarbon). Methane, methylene chloride), etc. The foaming degree of the urethane elastomer desired in the present invention is not strictly limited, but unlike ordinary urethane foam, it is important that the foaming degree is relatively low, and generally expressed in bulk density is 0.4 It is advantageous to range from 0.75 g/cm ³ to 0.55 to 0.7 g/cm ³ , and the amount of the blowing agent (e) used and/or the amount of foaming depends on the bulk density of the resulting urethane elastomer. can be adjusted so that it falls within the above range. In addition to the above-mentioned components, the urethane elastomer foaming stock solution according to the present invention contains, if necessary, a foam stabilizer (e.g., silicone surfactant, etc.), a pigment (e.g., carbon black, etc.), as usual.
etc. can also be added. The components of the urethane elastomer foaming stock solution described above are thoroughly mixed immediately before use according to a conventional method, and then poured into a formwork attached to a concrete sleeper using the method described in JP-A-55-130754. By doing so, an elastic sleeper having an elastic covering material can be manufactured. Next, the present invention will be further explained with reference to Examples and Comparative Examples. The physical properties in Examples and Comparative Examples were measured by the methods described below. (1) Bulk density: JIS Z 8807 “Measurement method from volume”
According to. (2) Compression set: According to JIS K 6301 "10. Compression set test". (Temperature 70℃, 30% compression, 22
(3) Spring constant: Conforms to JIS K 6385 "5. Static spring constant test". (Using a 10cm x 10cm x 2.5cm sample, pressurize up to 425Kg, and
(4) Tensile strength and tensile elongation: Measured using a dumbbell No. 1 test piece according to JIS K 6301 "3. Tensile test method". (5) Water resistance: Using the same No. 1 dumbbell test piece used in the tensile strength test, the test piece was immersed in distilled water or ion-exchanged water.
After soaking for 96 hours, wipe it gently and immediately perform a tensile strength test to determine the rate of change from the value before aging. (6) Fatigue resistance: SRIS (Japan Rubber Association Standards)
According to 3502. (Test conditions are precompression amount 5mm width 4
Example 1 and ² , Comparative Examples 1 to 3 Prepare liquids A and B with the composition shown below in a stirrer. After mixing at a rotational speed of 6000 rpm, the mixture was immediately poured into a mold of an appropriate size, left at room temperature for 2 hours, and then demolded to obtain a foamed urethane elastomer. The physical properties of this urethane elastomer were measured by the method described above.
The results are shown below. Example 1 Composition of liquid A: parts by weight Polyether polyol (I) (copolymer adduct of glycerin/propylene oxide/ethylene oxide; average number of functional groups 3; average molecular weight 3000) 40 Polyether polyol () (glycerin/pentaerythritol/propylene Oxide/ethylene oxide copolymer adduct; average number of functional groups
3.7; average molecular weight 5700) 50 Graft polyol (glycerin/propylene oxide/ethylene oxide copolymer adduct average molecular weight 5100) is graft-polymerized with acrylonitrile and styrene in the presence of azobisisobutyronitrile (polymerization initiator). Polymer polyol obtained; average number of functional groups 3; grafting rate 10%; average molecular weight 6000) 10 Ethylene glycol 7 Water 0.53 Triethylenediamine 0.7 Liquid B composition: NCO Index polyisocyanate/polyol prepolymer (4,4'-diphenyl Isocyanate-terminated precursor condensate of methane diisocyanate and glycerin/propylene oxide/ethylene oxide copolymer adduct with average molecular weight 6500 (average functional group number 3; free NCO content = 16% by weight) 100 Physical bulk density: 0.63g /cm ³ Spring constant: 0.98tf/cm・100cm ² Compression set: 7.0% Tensile strength: 13.0Kg/cm ² Tensile elongation: 120% Water resistance Tensile strength change rate: -8.9% Tensile elongation change rate: - 10.3% Fatigue resistance: Settling amount 0.26 mm Example 2 A liquid composition: Part by weight Polyether polyol () (copolymer adduct of glycerin/pentaerythritol/propylene oxide/ethylene oxide; average number of functional groups
3.7; average molecular weight 5700) 90 Graft polyol (glycerin/propylene oxide/ethylene oxide copolymer adduct (average molecular weight 5100), acrylonitrile and styrene are graft-polymerized in the presence of azobisisobutyronitrile (polymerization initiator) (Average functional group number: 3; Grafting rate: 10%; Average molecular weight: 6000) 10 Ethylene glycol 5.7 Water 0.48 Triethylenediamine 0.7 B liquid composition: NCO Index polyisocyanate/polyol prepolymer (4,4'-diphthalate) Isocyanate-terminated precursor condensate of enylmethane diisocyanate and glycerin/propylene oxide/ethylene oxide copolymer adduct with an average molecular weight of 6500; free NCO content = 16% by weight) 100 Physical properties Bulk density: 0.63 g/cm ³ Spring constant: 0.98 tf/cm・100cm ² Compression set: 6.8% Tensile strength: 14.5Kg/cm ² Tensile elongation: 130% Water resistance Tensile strength change rate: -6.5% Tensile elongation change rate: -8.2% Fatigue resistance: To Comparative example 1 Composition of liquid A: parts by weight Polyether polyol (copolymer adduct of glycerin/propylene oxide/ethylene oxide;
Average functional group number 3; average molecular weight 6500) 100 Ethylene glycol 9.7 Water 0.58 Triethylene diamine 0.7 B liquid composition: NCO Index polyisocyanate/polyol prepolymer (isocyanate terminal of 4,4'-diphenylmethane diisocyanate and the above polyether polyol) Precursor condensate; free NCO content = 16% by weight) 100 Physical properties Bulk density: 0.63g/cm ³ Spring constant: 0.98tf/cm・100cm ² Compression set: 34% Tensile strength: 22.3Kg/cm ² Tensile elongation :78% Water resistance Tensile strength change rate: -18.8% Tensile elongation change rate: -25.0% Fatigue resistance: Settling amount 1.5 mm Comparative example 2 Composition of liquid A: Part by weight polyether polyol (I) (glycerin/propylene Copolymerization adduct of oxide/ethylene oxide; average functional group number 3; average molecular weight 3000) 50 Polyether polyol () (copolymerization adduct of glycerin/pentaerythritol/propylene oxide/ethylene oxide; average functional group number
3.7; average molecular weight 5700) 50 Ethylene glycol 6.1 Water 0.51 Triethylene diamine 0.7 B liquid composition: NCO Index polyisocyanate/polyol prepolymer (copolymer adduct of 4,4'-diphenylmethane diisocyanate and glycerin/propylene oxide/ethylene oxide) Isocyanate-terminated precursor condensate with (average molecular weight 6500); free NCO content = 16
Weight%) 100 Properties Bulk density: 0.63 g/cm ³ Spring constant: 0.97 Kgf/cm・100 cm ² Compression set: 17% Tensile strength: 11.5 Kg/cm ² Tensile elongation: 120% Water resistance Tensile strength change rate : -9.0% Tensile elongation change rate: -10.1% Fatigue resistance: Settling amount 0.35 mm Comparative example 3 A liquid composition: Part by weight Polyether polyol (copolymer adduct of glycerin/propylene oxide/ethylene oxide;
Average functional group number 3; average molecular weight 6500) 100 Ethylene glycol 3.0 Water 0.35 Triethylene diamine 0.20 B liquid composition: NCO Index polyisocyanate/polyol prepolymer (isocyanate terminal of 4,4'-diphenylmethane diisocyanate and the above polyether polyol) Precursor condensate; free NCO content = 16% by weight) 100 Physical properties Bulk density: 0.76g/cm ³ Spring constant: 0.98tf/cm・100cm ² Compression set: 6.9% Tensile strength: 8.3Kg/cm ² Tensile elongation : 130% Water resistance Tensile strength change rate: -11% Tensile elongation change rate: -9% Fatigue resistance: Settling amount 0.25 mm Reference example 1 Manufacture of direct-connected elastic sleepers Concrete with dimensions of 400 mm x 2000 mm x 200 mm Block 1 as shown in Figure 1,
It was set in a mold 2 with a degassing hole 3 of 1.5 mmφ, and the coating thickness (w, w' in FIG. 2) and height (h in FIG. 2) were set to 25 mm and 150 mm, respectively. Then,
Using the apparatus shown in FIG. 3, liquids A and B having the compositions shown in Example 1 were stirred at a rotating speed
The mixture was mixed at 6000 rpm and injected from the lower part 4 of the mold. After being left at room temperature for 2 hours, the mold was removed to obtain a direct-coupled elastic sleeper. This prototype sleeper was compressed using an Amsler compression tester, and the amount of strain in the elastic covering material was measured. For comparison, solutions A and B having the composition shown in Comparative Example 3 were used.
A direct-coupled elastic sleeper was prototyped in the same manner using liquid, and the amount of strain was measured. The results are shown in the graph of FIG. In the figure, the curve -○- is that of this reference example, and the curve -x- is that of comparative example 3. As is clear from this result, the elastic sleeper prototyped using the covering material of the present invention has a low bulk density (0.03 g/cm ³ ), but the covering material of Comparative Example 3 has a low bulk density (0.03 g/cm 3 ). It is possible to achieve a load-strain amount that is almost the same as that of the elastic sleeper prototyped using a material with a density of 0.78 g/cm ³ ), and exhibits an excellent vibration-proofing effect. Reference example 2 Measurement of vibration damping effect As shown in the experimental setup in Figure 5, anti-vibration rubber C (100 mm x 100 mm x 25 mm) is placed on concrete ground G.
Slab concrete b (3800mm×1000mm
A sample piece d (100 mm
mm x 50 mm), and then place slab concrete a of the same size as above on top of it. Next, the height is set at the center of the concrete slab a .
A passenger car tire is dropped from a distance of 1.2 mm, and the vibration damping state is measured using vibration pickups A and B attached to concrete slabs a and b . The results are shown in FIG. For comparison, FIG. 6 also shows the measurement results when a conventional slab rubber plate and concrete block were used in place of the sample d . In FIG. 6, each curve has the following meaning.

[Front] Board
concrete

Claims (1)

[Scope of Claims] 1 (a) A polyether polyol having an average number of functional groups of 2.5 to 4.5 and a number average molecular weight of 2000 to 3500, (b) A polyether polyol having an average number of functional groups of 2.5 to 4.0 and a grafting rate of 4 to 20. consisting essentially of a vinyl monomer graft polyol in weight percent, (c) an organic polyisocyanate, (d) a chain extender, (e) a blowing agent, and (f) a urethanization catalyst, having an NCO index of 90 to 110.
and the chain extender is within the range of (a), (b),
0.3× based on the total amount of the four components (c) and (d)
The bulk density prepared from a urethane elastomer foam stock solution containing a concentration of 10 ^-3 to 1.5 × 10 ^-3 mol/g is
An elastic covering material for a direct-coupled elastic sleeper made of a foamed urethane elastomer having urethane bonds of 0.4 to 0.75 g/cm ³ .