Track foaming vibration reduction base plate and preparation method thereof

Abstract

The invention relates to the field of foaming vibration reduction base plates, in particular to a track foaming vibration reduction base plate and a preparation method thereof.The track foaming vibration reduction base plate is formed by laminating a first layer of material, a second layer of material and a third layer of material in a sheet shape and then conducting mold closing and vulcanization; the first layer material is one-time vulcanized rubber, and the rubber comprises the following raw materials in parts by weight: 40-50 parts of ethylene propylene diene monomer, 1-3 parts of a vulcanizing agent, 3-5 parts of a vulcanization accelerator, 20-30 parts of carbon black, 5-10 parts of paraffin oil and 1-3 parts of a microsphere foaming agent; the second layer is made of non-foaming low Mooney rubber; and the third layer is made of modified PET geotechnical cloth. The track foaming vibration reduction base plate prepared by the invention is high in flatness, uniform in foaming, proper in foam hole density, good in water resistance, good in cohesiveness between layers, not easy to fall off and easy to industrialize.

Description

Technical Field

[0001] The invention relates to the field of foamed vibration-damping pads, and in particular to a track foamed vibration-damping pad and a preparation method thereof. Background Art

[0002] The rail foam vibration damping pad is set at the lower support point of the trapezoidal sleeper and is used to isolate the rail component from the vibration transmitted from the sleeper to the reinforced concrete roadbed. The vibration damping pad needs to be fixed together with the sleeper during production. The main method currently used in China is to add a layer of fabric to the vibration damping pad and fix the vibration damping pad and the concrete sleeper together through the fabric. There are two main ways to attach the fabric to the vibration damping pad: cold gluing (glue) and hot vulcanization. The main disadvantages of cold gluing are poor anti-aging ability at the bonding point, low bonding strength, uneven bonding, and high cost; hot vulcanization has high bonding strength, strong anti-aging ability, and uniform bonding. However, because the product is made of foam rubber, the fabric will cause inconsistent heating of the upper and lower surfaces of the rubber during vulcanization, resulting in uneven foaming. At the same time, the shrinkage of the fabric will cause the product to warp and cause serious deformation of the product.

[0003] Patent CN104861314B discloses a microporous rubber pad and its preparation process, which adopts low Mooney EPDM and high Mooney EPDM to mechanically blend to form a uniformly dispersed multiphase structure, and uses a polyethylene glycol mixture to neutralize the benzenesulfonic acid formed by the foaming agent 4,4-oxybisbenzenesulfonylhydrazine during the reaction process to increase the foaming ratio, supplemented by carbon black with good reinforcing properties and diatomaceous earth filler with excellent aging properties, light weight and porosity, to give the microporous rubber pad high strength, low stiffness and low temperature dependence. However, this microporous rubber pad is prone to uneven foaming when hot-vulcanized with fabrics.

[0004] Patent CN105885250B discloses a production process and product of EPDM rubber microporous pads. The application replaces the mold compression vulcanization in the prior art with continuous vulcanization in high temperature section, microwave section and oven section, which not only improves the production efficiency of the microporous pads and reduces the input of manpower and material resources, but also improves the strength and anti-collapse performance of the microporous pads, meeting the vibration reduction needs of low-vibration rail foundations in increasingly complex rail transit lines. However, the process is relatively complex and difficult to industrialize.

[0005] Therefore, the market is in urgent need of a track foaming vibration-damping pad that has uniform foaming, high flatness and is easy to industrialize. Summary of the invention

[0006] In view of the problems existing in the prior art, the purpose of the present invention is to obtain a track foamed vibration-damping pad with high flatness, uniform foaming, appropriate pore density, good water resistance, easy industrialization and good adhesion between layers that is not easy to fall off.

[0007] In order to achieve the above object, the technical solution adopted by the present invention is as follows:

[0008] On the one hand, the present invention provides a rail foam vibration-damping pad, which is formed by stacking a first layer of material, a second layer of material and a third layer of material in a sheet shape and then vulcanizing them through mold closing; the first layer of material is a once-vulcanized rubber, and the rubber includes the following raw materials, by weight, 40-50 parts of EPDM rubber, 1-3 parts of a vulcanizing agent, 3-5 parts of a vulcanization accelerator, 20-30 parts of carbon black, 5-10 parts of paraffin oil, and 1-3 parts of a microsphere foaming agent; the second layer of material is a non-foamed low Mooney rubber; and the third layer of material is a modified PET geotextile.

[0009] Preferably, the vulcanizing agent is S-80.

[0010] Preferably, the vulcanization accelerator is CZ.

[0011] Preferably, the paraffin oil is No. 10 white oil.

[0012] This application uses foamed EPDM rubber, non-foamed low Mooney EPDM rubber and geotextile to separate the foamed EPDM rubber from the geotextile, which solves the problem that the fabric will cause the upper and lower sides of the rubber to be heated inconsistently during vulcanization, resulting in uneven foaming, and the product will be seriously warped and deformed due to fabric shrinkage. And by adding microsphere foaming agent and modified PET geotextile, the obtained track foam vibration damping pad has the advantages of high flatness and good adhesion between layers, which is not easy to fall off.

[0013] In some embodiments, the method for preparing the microsphere foaming agent comprises the following steps:

[0014] A1. Add sodium bicarbonate, 3-isocyanatepropyltrimethoxysilane and acetone into a reaction vessel, heat to 30-40° C., react for 20-30 min, and dry to obtain silane-modified sodium bicarbonate;

[0015] A2. Add the silane-modified sodium bicarbonate, catalyst 1, acetone and polyurethane prepolymer obtained in step A1 into a reaction container, react at 30-40° C. for 1-2 hours, and obtain a microsphere foaming agent after drying.

[0016] Closed-cell foamed rubber has mutually independent pores, and this structure makes the rubber have excellent water resistance. The amount of gas generated by the foaming agent and the diffusion rate of the gas in the rubber affect the pore structure. Conventional foaming agents begin to foam before the rubber is vulcanized, so that the vulcanization rate and the foaming rate cannot match, resulting in the phenomenon of open-cell foaming in the rubber. In response to this problem, the present application grafts a silane coupling agent containing an isocyanate group on sodium bicarbonate and reacts it with a polyurethane prepolymer, thereby achieving the purpose of coating a polyurethane shell on sodium bicarbonate. The microsphere foaming agent is used in the process of rubber vulcanization. The polyurethane shell of the microsphere foaming agent begins to decompose at 170°C, and the foaming process can be controlled to occur after vulcanization and end before the end of vulcanization, so that the foamed rubber has a suitable foaming density and water resistance. In addition, the detached polyurethane shell has good toughness, and its dispersion in the rubber can enhance the EPDM rubber to improve the mechanical properties of the track foaming vibration damping pad.

[0017] In some embodiments, the mass ratio of the sodium bicarbonate to 3-isocyanatepropyltrimethoxysilane is 1:(0.2-0.3).

[0018] The present application can make the rail foam vibration damping pad have better mechanical properties by selecting a specific ratio of sodium bicarbonate and 3-isocyanatepropyltrimethoxysilane. This may be because some 3-isocyanatepropyltrimethoxysilane remains in the system, which can promote the dispersion of carbon black.

[0019] In some embodiments, the mass ratio of the silane-modified sodium bicarbonate to the polyurethane prepolymer in step A2 is 1:(1-1.2).

[0020] The present application can make the rail foam vibration damping pad have a suitable foaming density by selecting a specific ratio of silane-modified sodium bicarbonate and polyurethane prepolymer. This may be because some polyurethane prepolymer remains in the system, which can provide supporting force to stabilize the pore structure formed in the rubber and prevent the pores from collapsing.

[0021] In some embodiments, the method for preparing the modified PET geotextile comprises the following steps:

[0022] B1. Soak the PET geotextile in 23-27g / L dilute nitric acid at 70-90°C for 20-40min, wash and dry it, soak it in a mixed aqueous solution of sodium sulfide and sodium carbonate, react at 95-98°C for 20-40min, wash and dry it to obtain amino PET geotextile;

[0023] B2, soaking the amino PET geotextile obtained in step B1 in a 20-30wt% acrylic acid methanol solution, heating to 70-80°C for reaction for 1-2h to obtain an acrylic acid-modified PET geotextile;

[0024] B3, trimethylolpropane trimethacrylate, anhydrous methanol and azobisisobutyronitrile are added into a reaction vessel, stirred for 20-30 minutes to obtain a mixed solution, the acrylic acid-modified PET geotextile obtained in step B2 is immersed in the mixed solution, reacted at 70-80° C. for 1-3 hours, and the modified PET geotextile is obtained.

[0025] The present application modifies the PET geotextile and grafts multiple double bonds on the geotextile so that it can form certain crosslinks with the low Mooney EPDM rubber during the secondary vulcanization process, thereby enhancing the adhesion strength between the two layers.

[0026] In some embodiments, the mass concentration of sodium sulfide in the mixed aqueous solution is 38-40 g / L, and the mass concentration of sodium carbonate in the mixed aqueous solution is 18-22 g / L.

[0027] In some embodiments, the impregnation ratio of the amino PET geotextile and the 20-30 wt % acrylic acid methanol solution in step B2 is 1:(4-5).

[0028] The present application can improve the adhesion of the track foam vibration-damping pad by limiting the ratio of amino PET geotextile and 20-30wt% acrylic acid methanol solution. This may be because some residual acrylic acid in the system is beneficial to improving the viscosity of the rubber.

[0029] In some embodiments, the mass ratio of anhydrous methanol to trimethylolpropane trimethacrylate in step B3 is 1:(0.05-0.1).

[0030] The present application can achieve better bonding effect of the rail foam vibration damping pad by limiting the ratio of anhydrous methanol and trimethylolpropane trimethacrylate. This may be because the residual trimethylolpropane trimethacrylate plays the role of a vulcanizing agent between the two layers, thereby improving the vulcanization performance.

[0031] Another aspect of the present invention provides a method for preparing a track foaming vibration-damping pad, comprising the following steps:

[0032] (1) placing EPDM rubber in an internal mixer for plasticizing at a temperature of 70-80° C. for a plasticizing time of 20-25 min to obtain plasticized rubber;

[0033] (2) adding the plasticized rubber, vulcanization accelerator, carbon black and paraffin oil obtained in step (1) into an internal mixer for mixing at a mixing temperature of 80-110° C. for a mixing time of 10-20 min to obtain a rubber mixture;

[0034] (3) putting the rubber mix obtained in step (2) into an open mixer, adding a vulcanizing agent and a microsphere foaming agent, and mixing at 40-45° C., adjusting the roller distance to 0.8-1.3 mm, making triangle packages 3-5 times, and then adjusting the roller distance to 5-6 mm to produce sheets, and after the sheets are parked for 2-15 days, they are put into a cutting machine to cut into rubber strips, which are added to an extruder for extrusion, and the molded rubber is obtained after cutting;

[0035] (4) subjecting the molded rubber obtained in step (3) to primary vulcanization in a flat vulcanizer at a vulcanization temperature of 165° C. to 175° C. and a vulcanization time of 20 to 30 min to obtain a primary vulcanized rubber;

[0036] (5) grinding the once-vulcanized rubber obtained in step (4) using a grinder to obtain a grinded rubber;

[0037] (6) calendering the non-foamed low Mooney rubber, wherein the calendering specification is 0.8-1.2 mm, the width is 230-250 mm, and the cutting length after calendering is 620-660 mm to obtain a calendered rubber;

[0038] (7) The polished rubber obtained in step (5), the calendered rubber obtained in step (6), and the modified PET geotextile are sequentially placed in the mold cavity, and the mold is closed for vulcanization. The vulcanization temperature is 165°C-175°C, the vulcanization time is 5-7 minutes, and the pressure is 140-160kg / cm 2 , and obtain the track foaming vibration damping pad.

[0039] In some embodiments, the thickness of the once-vulcanized rubber is 25-25.5 mm, and the thickness of the polished rubber is 24.5-25 mm.

[0040] Compared with the prior art, the present invention has the following beneficial effects:

[0041] (1) The present invention separates the foamed EPDM rubber from the geotextile by stacking the foamed EPDM rubber, the low Mooney EPDM rubber and the geotextile, thereby solving the problem that the fabric will cause the upper and lower surfaces of the rubber to be heated inconsistently during vulcanization, resulting in uneven foaming and serious warping and deformation of the product due to fabric shrinkage; and by adding microsphere foaming agent and modified PET geotextile, the obtained track foam vibration damping pad has the advantages of high flatness and good adhesion between the layers, and is not easy to fall off.

[0042] (2) The present invention grafts a silane coupling agent containing an isocyanate group onto sodium bicarbonate and reacts it with a polyurethane prepolymer, thereby achieving the purpose of coating the sodium bicarbonate with a polyurethane shell. The use of the microsphere foaming agent during the rubber vulcanization process can make the foamed rubber have a suitable foaming density and water resistance, and can improve the mechanical properties of the track foaming vibration damping pad.

[0043] (3) The present invention grafts multiple double bonds on the PET geotextile so that it can form a certain cross-linking with the low Mooney EPDM rubber during the secondary vulcanization process, thereby enhancing the adhesion strength between the two layers. And by limiting the ratio of acrylic modified PET geotextile and trimethylolpropane trimethacrylate, the bonding effect of the track foaming vibration damping pad and the geotextile can be improved. DETAILED DESCRIPTION

[0044] The present invention will be described below in conjunction with specific embodiments. It should be noted that the following embodiments are examples of the present invention and are only used to illustrate the present invention, but not to limit the present invention. Other combinations and various modifications within the concept of the present invention may be performed without departing from the spirit or scope of the present invention.

[0045] In the following embodiments and comparative examples, except for the microsphere foaming agent and modified PET geotextile, the other compounds and related reagents used can be purchased from the market. Among them, the EPDM rubber model is EPDM4045, purchased from China Petroleum Jilin Petrochemical Company; the non-foamed low Mooney EPDM rubber is purchased from Ningbo Shunou Plastic Co., Ltd.; S-80, CZ, and N550 carbon black are all purchased from Guangzhou Lida Rubber Raw Material Trading Co., Ltd.; the NCO content of the polyurethane prepolymer is 7.2wt%, purchased from Wuhan Kmik Biomedical Technology Co., Ltd.; the PET geotextile has a thickness of 3mm and a length of 640mm purchased from Dezhou Weiner Plastic Co., Ltd.

[0046] Preparation Example 1

[0047] The preparation method of microsphere foaming agent-1 comprises the following steps:

[0048] A1. Add 10 g of sodium bicarbonate, 2.5 g of 3-isocyanatepropyltrimethoxysilane and 20 g of acetone into a reaction container, heat to 35° C. and react for 25 h. After drying, obtain silane-modified sodium bicarbonate;

[0049] A2. Add 10 g of the silane-modified sodium bicarbonate obtained in step A1, 0.01 g of DY-20, 10 g of acetone and 11 g of polyurethane prepolymer into a reaction container, react at 35° C. for 1.5 h, and obtain microsphere foaming agent-1 after drying.

[0050] Preparation Example 2

[0051] The preparation method of microsphere foaming agent-2 is the same as that of Preparation Example 1, except that the added amount of 3-isocyanatepropyltrimethoxysilane is 1.5 g.

[0052] Preparation Example 3

[0053] The preparation method of microsphere foaming agent-2 is the same as that of Preparation Example 1, except that the added amount of polyurethane prepolymer is 9g.

[0054] Preparation Example 4

[0055] The preparation method of modified PET geotextile-1 comprises the following steps:

[0056] B1. Immerse the PET geotextile in 25 g / L dilute nitric acid at 80°C for 30 min at an immersion ratio of 1:2, wash and dry, and then immerse it in a mixed aqueous solution of 39 g / L sodium sulfide and 20 g / L sodium carbonate at an immersion ratio of 1:2, react at 96°C for 30 min, wash and dry to obtain amino PET geotextile;

[0057] B2, soaking the amino PET geotextile obtained in step B1 in a 25wt% acrylic acid methanol solution at an immersion ratio of 1:4.5, heating to 75°C for reaction for 1.5h to obtain an acrylic acid-modified PET geotextile;

[0058] B3. Add trimethylolpropane trimethacrylate, anhydrous methanol and azobisisobutyronitrile into a reaction vessel and stir for 25 minutes to obtain a mixed solution, the mass ratio of the three is 0.07:1:0.001, and immerse the acrylic acid-modified PET geotextile obtained in step B2 in the mixed solution with an immersion ratio of 1:2, and react at 75°C for 2 hours to obtain a modified PET geotextile.

[0059] Preparation Example 5

[0060] The preparation method of modified PET geotextile-2 is the same as that of Preparation Example 4, except that the impregnation ratio of the amino PET geotextile and the 25wt% acrylic acid methanol solution is 1:3.5.

[0061] Preparation Example 6

[0062] The preparation method of modified PET geotextile-3 is the same as that of Preparation Example 4, except that the mass ratio of anhydrous methanol to trimethylolpropane trimethacrylate is 1:0.04 g.

[0063] Example 1

[0064] A track foam vibration-damping pad is formed by laminating, vulcanizing and vulcanizing a first layer of material, a second layer of material and a third layer of material in a sheet form; the first layer of material is a once-vulcanized rubber, which comprises the following raw materials in parts by weight: 45 parts of EPDM rubber, 2 parts of S-80, 4 parts of CZ, 25 parts of N550 carbon black, 7 parts of No. 10 white oil, and 2 parts of microsphere foaming agent-1; the second layer of material is a non-foamed low Mooney rubber; and the third layer of material is a modified PET geotextile-1.

[0065] The method for preparing the track foaming vibration-damping pad of this embodiment comprises the following steps:

[0066] (1) placing EPDM rubber in an internal mixer for plasticizing at a temperature of 75° C. for a plasticizing time of 23 min to obtain plasticized rubber;

[0067] (2) adding the rubber, CZ, N550 and No. 10 white oil obtained in step (1) into an internal mixer for mixing at a mixing temperature of 95° C. for 15 min to obtain a rubber mixture;

[0068] (3) putting the mixed rubber obtained in step (2) into an open mixer, adding S-80 and microsphere foaming agent-1, and mixing at 43° C., adjusting the roller distance to 1 mm, making triangle packages 4 times, and then adjusting the roller distance to 5 mm to produce sheets. After the sheets are parked for 10 days, they are put into a cutting machine to cut into rubber strips, which are added to an extruder for extrusion, and the molded rubber is obtained after cutting;

[0069] (4) subjecting the molded rubber obtained in step (3) to primary vulcanization in a flat vulcanizer at a vulcanization temperature of 170° C. and a vulcanization time of 25 min to obtain a primary vulcanized rubber having a thickness of 25.3 mm;

[0070] (5) grinding the primary vulcanized rubber obtained in step (4) using a grinder to obtain a ground rubber having a thickness of 24.7 mm and a length of 650 mm;

[0071] (6) calendering the non-foamed low Mooney rubber, with a calendering specification of 1 mm and a width of 240 mm, and cutting the length after calendering to 640 mm to obtain a calendered rubber;

[0072] (7) Put the polished rubber obtained in step (5), the calendered rubber obtained in step (6), and the modified PET geotextile-1 into the mold cavity, close the mold and vulcanize, the vulcanization temperature is 170°C, the vulcanization time is 6 minutes, and the pressure is 150kg / cm 2 , and obtain the track foaming vibration damping pad.

[0073] Example 2

[0074] A rail foam vibration-damping pad is formed by laminating, vulcanizing and vulcanizing a first layer of material, a second layer of material and a third layer of material in a sheet form; the first layer of material is a once-vulcanized rubber, which comprises the following raw materials, by weight: 40 parts of EPDM rubber, 1 part of S-80, 3 parts of CZ, 20 parts of N550 carbon black, 5 parts of No. 10 white oil, and 1 part of microsphere foaming agent-1; the second layer of material is a non-foamed low Mooney rubber; and the third layer of material is a modified PET geotextile-1.

[0075] The method for preparing the track foaming vibration-damping pad of this embodiment comprises the following steps:

[0076] (1) placing EPDM rubber in an internal mixer for plasticizing at a temperature of 70° C. for a plasticizing time of 25 min to obtain plasticized rubber;

[0077] (2) adding the rubber, CZ, N550 carbon black and No. 10 white oil obtained in step (1) into an internal mixer for mixing at a mixing temperature of 80° C. for 20 min to obtain a mixed rubber;

[0078] (3) putting the mixed rubber obtained in step (2) into an open mixer, adding S-80 and microsphere foaming agent-1, mixing at 40° C., adjusting the roller distance to 0.8 mm, making triangle packages 3 times, and then adjusting the roller distance to 5 mm to produce sheets. After the sheets are parked for 2 days, they are put into a cutting machine to cut into rubber strips, which are added to an extruder for extrusion, and the molded rubber is obtained after cutting;

[0079] (4) subjecting the molded rubber obtained in step (3) to primary vulcanization in a flat vulcanizer at a vulcanization temperature of 165° C. and a vulcanization time of 30 min to obtain a primary vulcanized rubber having a thickness of 25 mm;

[0080] (5) grinding the primary vulcanized rubber obtained in step (4) using a grinder to obtain a grinded rubber having a thickness of 24.5 mm and a length of 630 mm;

[0081] (6) calendering the non-foamed low Mooney rubber, with a calendering specification of 0.8 mm and a width of 230 mm, and cutting the length after calendering to 620 mm to obtain a calendered rubber;

[0082] (7) Place the polished rubber obtained in step (5), the calendered rubber obtained in step (6), and the modified PET geotextile-1 into the mold cavity, close the mold and vulcanize at a vulcanization temperature of 165° C., a vulcanization time of 7 min, and a pressure of 140 kg / cm 2 , and obtain the track foaming vibration damping pad.

[0083] Example 3

[0084] A track foam vibration-damping pad is formed by laminating, vulcanizing and vulcanizing a first layer of material, a second layer of material and a third layer of material in a sheet form; the first layer of material is a once-vulcanized rubber, which comprises the following raw materials in parts by weight: 50 parts of EPDM rubber, 3 parts of S-80, 5 parts of CZ, 30 parts of N550 carbon black, 10 parts of No. 10 white oil, and 3 parts of microsphere foaming agent-1; the second layer of material is a non-foamed low Mooney rubber; and the third layer of material is a modified PET geotextile-1.

[0085] The method for preparing the track foaming vibration-damping pad of this embodiment comprises the following steps:

[0086] (1) placing EPDM rubber in an internal mixer for plasticizing at a temperature of 80° C. for a plasticizing time of 20 min to obtain plasticized rubber;

[0087] (2) adding the rubber, CZ, N550 carbon black and No. 10 white oil obtained in step (1) into an internal mixer for mixing at a mixing temperature of 110° C. for 10 min to obtain a rubber mixture;

[0088] (3) putting the mixed rubber obtained in step (2) into an open mixer, adding S-80 and microsphere foaming agent-1, mixing at 45° C., adjusting the roller distance to 1.3 mm, making triangle packages 5 times, and then adjusting the roller distance to 6 mm to produce sheets. After the sheets are parked for 15 days, they are put into a cutting machine to cut into rubber strips, which are added to an extruder for extrusion, and the molded rubber is obtained after cutting;

[0089] (4) subjecting the molded rubber obtained in step (3) to primary vulcanization in a flat vulcanizer at a vulcanization temperature of 175° C. and a vulcanization time of 20 min to obtain a primary vulcanized rubber having a thickness of 25.5 mm;

[0090] (5) grinding the primary vulcanized rubber obtained in step (4) using a grinder to obtain a ground rubber having a thickness of 25 mm and a length of 670 mm;

[0091] (6) calendering the non-foamed low Mooney rubber, with a calendering specification of 1.2 mm and a width of 250 mm, and cutting the rubber to a length of 660 mm after calendering to obtain a calendered rubber;

[0092] (7) Place the polished rubber obtained in step (5), the calendered rubber obtained in step (6), and the modified PET geotextile-1 into the mold cavity, close the mold and vulcanize at a vulcanization temperature of 175°C, a vulcanization time of 5 minutes, and a pressure of 160 kg / cm 2 , and obtain the track foaming vibration damping pad.

[0093] Example 4

[0094] A rail foam vibration-damping pad and a preparation method thereof. The specific implementation method is the same as that of Example 1, except that an equal amount of microsphere foaming agent-1 is replaced by microsphere foaming agent-2.

[0095] Example 5

[0096] A rail foam vibration-damping pad and a preparation method thereof. The specific implementation method is the same as that of Example 1, except that an equal amount of microsphere foaming agent-1 is replaced by microsphere foaming agent-3.

[0097] Example 6

[0098] A track foamed vibration-damping pad and a preparation method thereof. The specific implementation method is the same as that of Example 1, except that the modified PET geotextile-1 is replaced by modified PET geotextile-2 in equal amounts.

[0099] Example 7

[0100] A track foamed vibration-damping pad and a preparation method thereof. The specific implementation method is the same as that of Example 1, except that the modified PET geotextile-1 is replaced by modified PET geotextile-3 in equal amounts.

[0101] Comparative Example 1

[0102] A track foaming vibration-damping pad and a preparation method thereof. The specific implementation method is the same as that of Example 1, except that an equal amount of microsphere foaming agent-1 is replaced by sodium bicarbonate.

[0103] Comparative Example 2

[0104] A track foamed vibration-damping pad and a preparation method thereof. The specific implementation method is the same as that of Example 1, except that the modified PET geotextile-1 is replaced by PET geotextile in equal amounts.

[0105] Performance Testing

[0106] 1. Sample preparation

[0107] The rubber obtained by primary vulcanization in Examples 1-5 and Comparative Example 1 was subjected to secondary vulcanization at a vulcanization temperature of 175°C, a vulcanization time of 5 min, and a pressure of 160 kg / cm 2 , to obtain a foamed rubber layer.

[0108] 2. Performance test:

[0109] (1) The tensile length, elongation at break, compression set, static stiffness and water resistance of the foam rubber layer are tested in accordance with GB / T 38695-2020 Technical Specifications for Ballastless Tracks of Urban Rail Transit;

[0110] (2) Density: Use a density tester to test the density of the foam rubber layer.

[0111] The test results are shown in Table 1.

[0112] Table 1

[0113]

[0114] It can be seen from the data in Table 1 that the foamed rubber layer of the rail foamed vibration damping pad in Examples 1-3 of the present invention has good mechanical properties, good water resistance, high stiffness and more suitable cell density. From the comparison between Example 4 and Example 1, it can be seen that by changing the ratio of 3-isocyanate propyltrimethoxysilane, the remaining part of 3-isocyanate propyltrimethoxysilane in the system is not enough to promote the dispersion of carbon black, thereby reducing the mechanical properties and stiffness of the foamed rubber layer, and making the cells easy to merge and collapse, resulting in a decrease in cell density; from the comparison between Example 5 and Example 1, it can be seen that by changing the ratio of the polyurethane prepolymer, the remaining polyurethane prepolymer in the system is not enough to provide support force to stabilize the cell structure formed in the rubber, so that the cell density of the foamed rubber layer is small and the compression permanent deformation is increased; from the comparison between Comparative Example 1 and Example 1, it can be seen that by directly using sodium bicarbonate as a foaming agent, the rubber undergoes open-cell foaming, resulting in poor mechanical properties and water resistance of the foamed rubber layer and a low cell density.

[0115] The rail foam vibration damping pads obtained in Examples 1-3, 6, 7 and Comparative Example 2 were fatigued for 3 million times according to the TJ / GW 103-2013 standard, and the puncture by ballast, tearing of the pads and delamination were observed to determine the performance of the rail foam vibration damping pads.

[0116] The test results are shown in Table 2.

[0117] Table 2

[0118] Group Whether there is puncture by ballast, tearing of pads, or delamination Example 1 no Example 2 no Example 3 no Example 6 Slight delamination Example 7 Slightly delaminated Comparative Example 2 Layering

[0119] It can be seen from the data in Table 2 that the rail foaming vibration-damping pads in Examples 1-3 of the present invention have good performance. From the comparison between Example 6 and Example 1, it can be seen that changing the ratio of 25wt% acrylic acid methanol solution, the residual part of acrylic acid in the system is not conducive to improving the viscosity of the rubber, thereby making the adhesion between the second and third layers of the rail foaming vibration-damping pad poor, and a slight stratification phenomenon occurs; from the comparison between Example 7 and Example 1, it can be seen that changing the ratio of trimethylolpropane trimethacrylate, the residual trimethylolpropane trimethacrylate is not enough to play the role of a vulcanizing agent between the two layers, thereby making the adhesion between the second and third layers of the rail foaming vibration-damping pad poor, and a slight stratification phenomenon occurs; from the comparison between Comparative Example 2 and Example 1, it can be seen that directly using PET geotextile, the performance of the rail foaming vibration-damping pad is poor.

[0120] The above implementation modes are only for illustrating the technical concept and features of the present invention, and their purpose is to enable people familiar with this technology to understand the content of the present invention and implement it, and they cannot be used to limit the protection scope of the present invention. Any equivalent changes or modifications made according to the spirit of the present invention should be included in the protection scope of the present invention.

Claims

1. A track foaming vibration damping pad, characterized in that: The rail foam vibration damping pad is formed by stacking a first layer of material, a second layer of material and a third layer of material in a sheet shape and then vulcanizing them through mold closing; the first layer of material is a once-vulcanized rubber, and the rubber includes the following raw materials, by weight, 40-50 parts of EPDM rubber, 1-3 parts of vulcanizing agent, 3-5 parts of vulcanization accelerator, 20-30 parts of carbon black, 5-10 parts of paraffin oil, and 1-3 parts of microsphere foaming agent; the second layer of material is a non-foamed low Mooney rubber; and the third layer of material is a modified PET geotextile.

2. The rail foam vibration damping pad according to claim 1, characterized in that: The preparation method of the microsphere foaming agent comprises the following steps: A1. Add sodium bicarbonate, 3-isocyanatepropyltrimethoxysilane and acetone into a reaction vessel, heat to 30-40° C., react for 20-30 min, and dry to obtain silane-modified sodium bicarbonate; A2. Add the silane-modified sodium bicarbonate, catalyst 1, acetone and polyurethane prepolymer obtained in step A1 into a reaction container, react at 30-40° C. for 1-2 hours, and obtain a microsphere foaming agent after drying.

3. The rail foam vibration damping pad according to claim 2, characterized in that: The mass ratio of the sodium bicarbonate to 3-isocyanatepropyltrimethoxysilane is 1:(0.2-0.3).

4. The rail foam vibration damping pad according to claim 2, characterized in that: The mass ratio of the silane-modified sodium bicarbonate to the polyurethane prepolymer in step A2 is 1:(1-1.2).

5. The rail foam vibration damping pad according to claim 1, characterized in that: The preparation method of the modified PET geotextile comprises the following steps: B1. Soak the PET geotextile in 23-27g / L dilute nitric acid at 70-90°C for 20-40min, wash and dry it, soak it in a mixed aqueous solution of sodium sulfide and sodium carbonate, react at 95-98°C for 20-40min, wash and dry it to obtain amino PET geotextile; B2, soaking the amino PET geotextile obtained in step B1 in a 20-30wt% acrylic acid methanol solution, heating to 70-80°C for reaction for 1-2h to obtain an acrylic acid-modified PET geotextile; B3, trimethylolpropane trimethacrylate, anhydrous methanol and azobisisobutyronitrile are added into a reaction vessel, stirred for 20-30 minutes to obtain a mixed solution, the acrylic acid-modified PET geotextile obtained in step B2 is immersed in the mixed solution, reacted at 70-80° C. for 1-3 hours, and the modified PET geotextile is obtained.

6. The rail foam vibration damping pad according to claim 5, characterized in that: The mass concentration of the sodium sulfide in the mixed aqueous solution is 38-40 g / L, and the mass concentration of the sodium carbonate in the mixed aqueous solution is 18-22 g / L.

7. The rail foam vibration damping pad according to claim 5, characterized in that: The impregnation ratio of the amino PET geotextile and the 20-30wt% acrylic acid methanol solution in step B2 is 1:(4-5).

8. The rail foam vibration damping pad according to claim 6, characterized in that: The mass ratio of anhydrous methanol to trimethylolpropane trimethacrylate in step B3 is 1:(0.05-0.1).

9. A method for preparing the track foaming vibration-damping pad according to any one of claims 1 to 8, characterized in that: The following steps are involved: (1) placing EPDM rubber in an internal mixer for plasticizing at a temperature of 70-80° C. for a plasticizing time of 20-25 min to obtain plasticized rubber; (2) adding the plasticized rubber, vulcanization accelerator, carbon black and paraffin oil obtained in step (1) into an internal mixer for mixing at a mixing temperature of 80-110° C. for a mixing time of 10-20 min to obtain a rubber mixture; (3) putting the rubber mix obtained in step (2) into an open mixer, adding a vulcanizing agent and a microsphere foaming agent, and mixing at 40-45° C., adjusting the roller distance to 0.8-1.3 mm, making triangle packages 3-5 times, and then adjusting the roller distance to 5-6 mm to produce sheets, and after the sheets are parked for 2-15 days, they are put into a cutting machine to cut into rubber strips, which are added to an extruder for extrusion, and the molded rubber is obtained after cutting; (4) subjecting the molded rubber obtained in step (3) to primary vulcanization in a flat vulcanizer at a vulcanization temperature of 165° C. to 175° C. and a vulcanization time of 20 to 30 min to obtain a primary vulcanized rubber; (5) grinding the once-vulcanized rubber obtained in step (4) using a grinder to obtain a grinded rubber; (6) calendering the non-foamed low Mooney rubber, wherein the calendering specification is 0.8-1.2 mm, the width is 230-250 mm, and the cutting length after calendering is 620-660 mm to obtain a calendered rubber; (7) The polished rubber obtained in step (5), the calendered rubber obtained in step (6), and the modified PET geotextile are sequentially placed in the mold cavity, and the mold is closed for vulcanization. The vulcanization temperature is 165°C-175°C, the vulcanization time is 5-7 minutes, and the pressure is 140-160kg / cm 2 , and obtain the track foaming vibration damping pad.

10. The method for preparing the track foaming vibration-damping pad according to claim 9, characterized in that: The thickness of the rubber after primary vulcanization is 25-25.5 mm, and the thickness of the rubber after polishing is 24.5-25 mm.

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