An orbital foamed vibration damping pad and its preparation method

Abstract

The present invention relates to the field of foamed vibration damping pads, and particularly to a track foamed vibration damping pad and a preparation method thereof. Among them, the track foamed vibration damping pad 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 subjecting them to mold closing and vulcanization; the first layer of material is a rubber vulcanized once. By weight, the rubber comprises the following raw materials: 40-50 parts of ethylene propylene diene monomer 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; the third layer of material is a modified PET geotextile. The track foamed vibration damping pad prepared by the present invention has high flatness, uniform foaming, appropriate cell density, good water resistance, good adhesion between layers, is not easy to fall off, and is easy to industrialize.

Description

Technical Field

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

[0002] The track foamed vibration damping pad is arranged at the lower fulcrum of the ladder sleeper and is a track component used to isolate the vibration transmitted from the sleeper to the reinforced concrete roadbed. The vibration damping pad needs to be fixedly combined with the sleeper during the production of the sleeper. At present, the main method adopted in China is to attach a layer of fabric to the vibration damping pad, and the vibration damping pad and the concrete sleeper are fixed together through the fabric. There are mainly two ways to attach the fabric to the vibration damping pad: cold pasting (glue) and hot vulcanization. The main disadvantages of cold pasting are poor anti-aging ability at the bonding place, low pasting strength, uneven pasting, and high cost; hot vulcanization has high bonding strength, strong anti-aging ability, and uniform pasting. However, since the product is made of foamed rubber, the fabric will cause uneven 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 drives the warping of the product, causing serious deformation of the product.

[0003] Patent CN104861314B discloses a microporous rubber pad and a preparation process thereof. The low Mooney EPDM and high Mooney EPDM are mechanically blended to form a uniformly dispersed multiphase structure. The polyethylene glycol mixture is used to neutralize the benzenesulfonic acid formed during the reaction of the blowing agent 4,4-oxybisbenzenesulfonyl hydrazide to increase the foaming ratio. Carbon black with good reinforcing performance and diatomite filler with excellent aging performance and light weight and porosity are used to endow the microporous rubber pad with properties such as high strength, low stiffness, and low temperature dependence. However, this microporous rubber pad is prone to uneven foaming during hot vulcanization with the fabric.

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

[0005] Therefore, there is an urgent need in the market for a track foamed vibration damping pad with uniform foaming, high flatness, and easy industrialization. Summary of the Invention

[0006] Aiming at 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 cell density, good water resistance, easy industrialization, and good adhesion between layers and not easy to fall off.

[0007] 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 foamed track vibration damping pad, which is formed by laminating a first layer of material, a second layer of material and a third layer of material in a sheet form and then subjecting them to mold closing and vulcanization; the first layer of material is a once-vulcanized rubber. By weight, the rubber includes the following raw materials: 40-50 parts of ethylene propylene diene monomer (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 blowing agent; the second layer of material is a non-foamed low Mooney rubber; 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] In this application, the foamed EPDM rubber, non-foamed low Mooney EPDM rubber and geotextile are stacked to separate the foamed EPDM rubber from the geotextile, solving the problems that during vulcanization, the fabric will cause uneven heating of the upper and lower surfaces of the rubber, resulting in uneven foaming, and at the same time, due to the shrinkage of the fabric, the product warps and deforms severely. And by adding a microsphere blowing agent and a modified PET geotextile, the obtained foamed track vibration damping pad has the advantages of high flatness and good adhesion between layers and is not easy to fall off.

[0013] In some embodiments, the preparation method of the microsphere blowing agent includes the following steps:

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

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

[0016] The closed-cell foamed rubber has mutually independent pores, and this structure endows the rubber with excellent water resistance. The amount of gas generated by the foaming agent and the diffusion rate of the gas in the rubber compound, as well as the ethyl vulcanization rate, affect the cell structure. Conventional foaming agents start foaming before the rubber is vulcanized, making the vulcanization rate and the foaming rate unable to match, resulting in the phenomenon of open-cell foaming of the rubber. To address this problem, in this application, a silane coupling agent containing an isocyanate group is grafted onto sodium bicarbonate and reacted with a polyurethane prepolymer, achieving the purpose of coating a polyurethane outer shell on the sodium bicarbonate. When this microsphere foaming agent is used in the process of rubber vulcanization, the polyurethane outer shell of the microsphere foaming agent starts to decompose at 170 °C, and the foaming process can be controlled to occur after vulcanization and end before the end of vulcanization, making the foamed rubber have a suitable foaming density and water resistance. Moreover, the shed polyurethane outer shell has good toughness, and its dispersion in the rubber can strengthen the ethylene propylene diene monomer rubber to improve the mechanical properties of the track foaming and vibration damping pad.

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

[0018] By selecting a specific ratio of sodium bicarbonate and 3-isocyanatopropyltrimethoxysilane in this application, the track foaming and vibration damping pad can have good mechanical properties. This may be because a part of 3-isocyanatopropyltrimethoxysilane 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] By selecting a specific ratio of the silane-modified sodium bicarbonate and the polyurethane prepolymer in this application, the track foaming and vibration damping pad can have a suitable foaming density. This may be because a part of the polyurethane prepolymer remains in the system, which can provide a supporting force to stabilize the cell structure formed in the rubber and prevent cell collapse.

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

[0022] B1. Immerse the PET geotextile in 23 - 27 g / L dilute nitric acid at 70 - 90 °C for 20 - 40 min, wash and dry it, then immerse it in an aqueous mixed solution of sodium sulfide and sodium carbonate, and react at 95 - 98 °C for 20 - 40 min. After washing and drying, amino PET geotextile is obtained;

[0023] B2. Immerse the amino PET geotextile obtained in step B1 in a 20 - 30 wt% acrylic acid methanol solution, heat it to 70 - 80 °C and react for 1 - 2 h to obtain the acrylic acid-modified PET geotextile;

[0024] B3. Add trimethylolpropane trimethacrylate, anhydrous methanol, and azobisisobutyronitrile into a reaction vessel, stir for 20 - 30 min to obtain a mixed solution, immerse the acrylic acid - modified PET geotextile obtained in step B2 into the mixed solution, and react at 70 - 80 °C for 1 - 3 h to obtain a modified PET geotextile.

[0025] In this application, through the modified PET geotextile, multiple double bonds are grafted onto the geotextile, enabling it to form a certain cross - link with the low - Mooney ethylene - propylene - diene rubber during the secondary vulcanization process, 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] In this application, by limiting the ratio of the amino - PET geotextile and the 20 - 30 wt% acrylic acid methanol solution, the bonding property of the track foamed vibration - damping pad can be better. This may be because some acrylic acid remains in the system, which is beneficial to increasing the viscosity of the rubber.

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

[0030] In this application, by limiting the ratio of anhydrous methanol and trimethylolpropane trimethacrylate, the bonding effect of the track foamed vibration - damping pad can be better. This may be because the residual trimethylolpropane trimethacrylate plays the role of a vulcanization accelerator between the two layers, improving the vulcanization performance.

[0031] On the other hand, the present invention provides a preparation method of a track foamed vibration - damping pad, comprising the following steps:

[0032] (1) Put ethylene - propylene - diene rubber into a mixer for plasticizing, the plasticizing temperature is 70 - 80 °C, and the plasticizing time is 20 - 25 min to obtain plasticized rubber;

[0033] (2) Add the plasticized rubber obtained in step (1), a vulcanization accelerator, carbon black, and paraffin oil into the mixer for mixing, the mixing temperature is 80 - 110 °C, and the mixing time is 10 - 20 min to obtain a mixed rubber;

[0034] (3) Feed the kneaded rubber obtained in step (2) into an open mill, add a vulcanizing agent and a microsphere blowing agent, mix evenly at 40 - 45 °C, then adjust the roll gap to 0.8 - 1.3 mm, make 3 - 5 triangle packages, and then adjust the roll gap to 5 - 6 mm to take out the sheet. Let the sheet stand for 2 - 15 days, then cut it into rubber strips on a cutting machine, add it into an extruder for extrusion, and obtain the formed rubber after cutting.

[0035] (4) Cure the formed rubber obtained in step (3) in a flat vulcanizing machine for the first time. The vulcanization temperature is 165 °C - 175 °C and the vulcanization time is 20 - 30 min to obtain the rubber after the first vulcanization.

[0036] (5) Grind the rubber after the first vulcanization obtained in step (4) using a grinding machine to obtain the ground rubber.

[0037] (6) Calender the non - foaming low Mooney rubber. The calendering specifications are 0.8 - 1.2 mm in thickness and 230 - 250 mm in width. After calendering, cut it to a length of 620 - 660 mm to obtain the calendered rubber.

[0038] (7) Put the ground rubber obtained in step (5), the calendered rubber obtained in step (6), and the modified PET geotextile into the mold cavity in sequence, close the mold and vulcanize. The vulcanization temperature is 165 °C - 175 °C, the vulcanization time is 5 - 7 min, and the pressure is 140 - 160 kg / cm 2 , to obtain the track foamed vibration - damping pad.

[0039] In some embodiments, the thickness of the rubber after the first vulcanization is 25 - 25.5 mm, and the thickness of the ground 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 uses the method of stacking foamed ethylene - propylene - diene monomer (EPDM), low Mooney EPDM and geotextile to separate the foamed EPDM from the geotextile, solving the problems that during vulcanization, the fabric will cause uneven heating of the upper and lower surfaces of the rubber, resulting in uneven foaming, and the shrinkage of the fabric will drive the product to warp and deform severely; and by adding a microsphere blowing agent and a modified PET geotextile, the obtained track foamed vibration - damping pad has the advantages of high flatness and good adhesion between 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 to achieve the purpose of coating a polyurethane shell on sodium bicarbonate. Using this microsphere blowing agent during the rubber vulcanization process can make the foamed rubber have a suitable foaming density and water - resistant performance, and can improve the mechanical properties of the track foamed vibration - damping pad.

[0043] (3) By grafting multiple double bonds onto the PET geotextile, the present invention enables it to form a certain degree of crosslinking with the low Mooney ethylene-propylene-diene monomer (EPDM) rubber during the secondary vulcanization process, enhancing the adhesion strength between the two layers. And by defining the ratio of the acrylic acid-modified PET geotextile and trimethylolpropane trimethacrylate, the bonding effect between the track foamed vibration damping pad and the geotextile can be improved. Detailed implementation manners

[0044] The present invention will be described below in conjunction with specific implementation manners. It should be noted that the following examples are examples of the present invention, only used to illustrate the present invention, and not to limit the present invention. Other combinations and various improvements within the concept of the present invention can be made without departing from the main idea or scope of the present invention.

[0045] In the following examples and comparative examples, except for the microsphere blowing agent and the modified PET geotextile, the other compounds and related reagents used can be purchased from the market. Among them, the ethylene-propylene-diene monomer rubber model is EPDM4045, purchased from Jilin Petrochemical Company, PetroChina; the non-foaming low Mooney ethylene-propylene-diene monomer 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 7.2 wt%, purchased from Wuhan Kemike Biopharmaceutical Technology Co., Ltd.; the thickness of the PET geotextile is 3 mm and the length is 640 mm, purchased from Dezhou Weina Plastic Industry Co., Ltd.

[0046] Preparation Example 1

[0047] The preparation method of microsphere blowing agent - 1 includes the following steps:

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

[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 vessel, react at 35 °C for 1.5 h, and obtain microsphere blowing agent - 1 after drying.

[0050] Preparation Example 2

[0051] The preparation method of microsphere blowing agent - 2 is the same as that of Preparation Example 1 in specific implementation manners, except that the addition amount of 3-isocyanatopropyltrimethoxysilane is 1.5 g.

[0052] Preparation Example 3

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

[0054] Preparation Example 4

[0055] Preparation method of modified PET geotextile - 1, comprising the following steps:

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

[0057] B2. Immerse the amino PET geotextile obtained in step B1 in 25 wt% acrylic acid methanol solution with an immersion ratio of 1:4.5, and heat to 75 °C to react for 1.5 h to obtain acrylic acid - modified PET geotextile;

[0058] B3. Add trimethylolpropane trimethacrylate, anhydrous methanol and azobisisobutyronitrile into the reaction vessel, stir for 25 min to obtain a mixed solution, and the mass ratio of the three is 0.07:1:0.001. 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 h to obtain modified PET geotextile.

[0059] Preparation Example 5

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

[0061] Preparation Example 6

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

[0063] Example 1

[0064] An orbital foaming damping pad is formed by laminating a first - layer material, a second - layer material and a third - layer material in a sheet form and then subjecting them to mold - closing vulcanization. The first - layer material is rubber after primary vulcanization. By weight, the rubber includes the following raw materials: 45 parts of ethylene - propylene - diene monomer 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 material is non - foaming low - Mooney rubber. The third - layer material is modified PET geotextile - 1.

[0065] The preparation method of the track foaming vibration damping pad in this embodiment includes the following steps:

[0066] (1) Put ethylene propylene diene monomer rubber into a mixer for plasticizing. The plasticizing temperature is 75 °C and the plasticizing time is 23 min to obtain the plasticized rubber.

[0067] (2) Add the plasticized rubber obtained in step (1), CZ, N550, and No. 10 white oil into the mixer for mixing. The mixing temperature is 95 °C and the mixing time is 15 min to obtain the mixed rubber.

[0068] (3) Put the mixed rubber obtained in step (2) into an open mill, add S-80 and microsphere blowing agent-1, mix evenly at 43 °C, then adjust the roll gap to 1 mm, make 4 triangle bales, and then adjust the roll gap to 5 mm to take out the sheet. Let the sheet stand for 10 days, then cut it into rubber strips on a cutting machine, add it into an extruder for extrusion, and obtain the formed rubber after cutting.

[0069] (4) Carry out primary vulcanization on the formed rubber obtained in step (3) in a flat vulcanizer. The vulcanization temperature is 170 °C and the vulcanization time is 25 min to obtain the primary vulcanized rubber with a thickness of 25.3 mm.

[0070] (5) Grind the primary vulcanized rubber obtained in step (4) with a grinding machine to obtain the ground rubber with a thickness of 24.7 mm and a length of 650 mm.

[0071] (6) Calender the non-foaming low Mooney rubber. The calendering specification is 1 mm and the width is 240 mm. After calendering, cut the length to 640 mm to obtain the calendered rubber.

[0072] (7) Put the ground 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 min, and the pressure is 150 kg / cm 2 to obtain the track foaming vibration damping pad.

[0073] Example 2

[0074] A track foaming vibration damping pad 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 subjecting them to mold closing and vulcanization. The first layer of material is the primary vulcanized rubber. By weight, the rubber includes the following raw materials: 40 parts of ethylene propylene diene monomer 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 blowing agent-1. The second layer of material is non-foaming low Mooney rubber. The third layer of material is modified PET geotextile-1.

[0075] The preparation method of the track foaming vibration damping pad in this embodiment comprises the following steps:

[0076] (1) Put ethylene propylene diene monomer rubber into a kneader for plasticizing. The plasticizing temperature is 70 °C and the plasticizing time is 25 min to obtain the plasticized rubber.

[0077] (2) Add the plasticized rubber obtained in step (1), CZ, N550 carbon black, and No. 10 white oil into the kneader for mixing. The mixing temperature is 80 °C and the mixing time is 20 min to obtain the mixed rubber.

[0078] (3) Put the mixed rubber obtained in step (2) into an open mill, add S-80 and microsphere blowing agent-1, mix evenly at 40 °C, then adjust the roll gap to 0.8 mm, make three triangle wraps, then adjust the roll gap to 5 mm to take out the sheet. After the sheet is parked for 2 days, cut it into rubber strips on a cutting machine, add it into an extruder for extrusion, and obtain the formed rubber after cutting.

[0079] (4) Carry out primary vulcanization on the formed rubber obtained in step (3) in a flat vulcanizer. The vulcanization temperature is 165 °C and the vulcanization time is 30 min to obtain the primary vulcanized rubber with a thickness of 25 mm.

[0080] (5) Grind the primary vulcanized rubber obtained in step (4) with a grinding machine to obtain the ground rubber with a thickness of 24.5 mm and a length of 630 mm.

[0081] (6) Calender the non-foaming low Mooney rubber. The calendering specification is 0.8 mm and the width is 230 mm. After calendering, cut the length to 620 mm to obtain the calendered rubber.

[0082] (7) Put the ground rubber obtained in step (5), the calendered rubber obtained in step (6), and modified PET geotextile-1 into the mold cavity, close the mold for vulcanization. The vulcanization temperature is 165 °C, the vulcanization time is 7 min, and the pressure is 140 kg / cm 2 to obtain the track foaming vibration damping pad.

[0083] Example 3

[0084] A track foaming vibration damping pad is formed by laminating a first layer of material, a second layer of material, and a third layer of material in a sheet form and then subjecting them to mold closing and vulcanization. The first layer of material is the primary vulcanized rubber. By weight, the rubber includes the following raw materials: 50 parts of ethylene propylene diene monomer 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 blowing agent-1. The second layer of material is non-foaming low Mooney rubber. The third layer of material is modified PET geotextile-1.

[0085] The preparation method of the track foamed vibration damping pad in this embodiment includes the following steps:

[0086] (1) Put ethylene propylene diene monomer rubber into an internal mixer for plasticizing. The plasticizing temperature is 80°C and the plasticizing time is 20 min to obtain the plasticized rubber;

[0087] (2) Add the plasticized rubber obtained in step (1), CZ, N550 carbon black, and No. 10 white oil into the internal mixer for mixing. The mixing temperature is 110°C and the mixing time is 10 min to obtain the mixed rubber;

[0088] (3) Put the mixed rubber obtained in step (2) into an open mill, add S-80 and microsphere blowing agent-1, mix evenly at 45°C, then adjust the roll gap to 1.3 mm, make 5 triangular wraps, and then adjust the roll gap to 6 mm to take out the sheet. After the sheet is parked for 15 days, cut it into rubber strips on a cutting machine, add it into an extruder for extrusion, and obtain the formed rubber after cutting;

[0089] (4) Carry out primary vulcanization on the formed rubber obtained in step (3) in a flat vulcanizer. The vulcanization temperature is 175°C and the vulcanization time is 20 min to obtain the primary vulcanized rubber with a thickness of 25.5 mm;

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

[0091] (6) Calender the non-foaming low Mooney rubber. The calendering specification is 1.2 mm and the width is 250 mm. After calendering, cut the length to 660 mm to obtain the calendered rubber;

[0092] (7) Put the ground 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 175°C, the vulcanization time is 5 min, and the pressure is 160 kg / cm 2 to obtain the track foamed vibration damping pad.

[0093] Example 4

[0094] A track foamed vibration damping pad and its preparation method. The specific implementation method is the same as that of Example 1, except that microsphere blowing agent-1 is replaced with microsphere blowing agent-2 in equal amount.

[0095] Example 5

[0096] A track foamed vibration damping pad and its preparation method. The specific implementation method is the same as that of Example 1, except that microsphere blowing agent-1 is replaced with microsphere blowing agent-3 in equal amount.

[0097] Example 6

[0098] An orbital foamed vibration damping pad and its preparation method. The specific implementation is the same as that of Example 1, except that the modified PET geotextile-1 is replaced with the modified PET geotextile-2 in equal amounts.

[0099] Example 7

[0100] An orbital foamed vibration damping pad and its preparation method. The specific implementation is the same as that of Example 1, except that the modified PET geotextile-1 is replaced with the modified PET geotextile-3 in equal amounts.

[0101] Comparative Example 1

[0102] An orbital foamed vibration damping pad and its preparation method. The specific implementation is the same as that of Example 1, except that the microsphere foaming agent-1 is replaced with sodium bicarbonate in equal amounts.

[0103] Comparative Example 2

[0104] An orbital foamed vibration damping pad and its preparation method. The specific implementation is the same as that of Example 1, except that the modified PET geotextile-1 is replaced with PET geotextile in equal amounts.

[0105] Performance test

[0106] 1. Specimen preparation

[0107] The once-vulcanized rubber obtained from Examples 1-5 and Comparative Example 1 is 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) Test the tensile length, elongation at break, compression set, static stiffness, and water resistance of the foamed rubber layer in accordance with GB / T 38695—2020 "Technical Conditions for Ballastless Tracks in Urban Rail Transit";

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

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

[0112] Table 1

[0113]

[0114] As can be seen from the data in Table 1, the foamed rubber layer of the track foaming vibration damping pad in Examples 1-3 of the present invention has good mechanical properties, good water resistance, high stiffness and appropriate cell density. From the comparison between Example 4 and Example 1, it can be seen that by changing the ratio of 3-isocyanatopropyltrimethoxysilane, the remaining part of 3-isocyanatopropyltrimethoxysilane in the system is not sufficient to promote the dispersion of carbon black, resulting in a decrease in the mechanical properties and stiffness of the foamed rubber layer, and the cells are easy to merge and collapse, causing 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 sufficient to provide the supporting force to stabilize the cell structure formed in the rubber, resulting in a smaller cell density and an increase in compression set of the foamed rubber layer; from the comparison between Comparative Example 1 and Example 1, it can be seen that when directly using sodium bicarbonate as the foaming agent, the rubber shows an open-cell foaming phenomenon, resulting in poor mechanical properties and water resistance of the foamed rubber layer and a lower cell density.

[0115] After 3 million times of fatigue on the track foaming vibration damping pads obtained in Examples 1-3, 6, 7 and Comparative Example 2 according to the TJ / GW 103-2013 standard, observe whether there is any phenomenon of being pierced by ballast, tearing of the pad, and delamination, and judge the service performance of the track foaming vibration damping pad.

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

[0117] Table 2

[0118] Group Whether there is a phenomenon of being pierced by ballast, tearing of the tie plate, or delamination Example 1 No Example 2 No Example 3 No Example 6 Slight delamination Example 7 Slight delamination Comparative Example 2 Delamination

[0119] As can be seen from the data in Table 2, the track foaming vibration damping pads in Examples 1-3 of the present invention have good service performance. From the comparison between Example 6 and Example 1, it can be seen that by changing the ratio of the 25wt% methyl acrylate solution, the remaining part of acrylic acid in the system is not conducive to increasing the viscosity of the rubber, resulting in poor adhesion between the second layer and the third layer of the track foaming vibration damping pad and slight delamination; from the comparison between Example 7 and Example 1, it can be seen that by changing the ratio of trimethylolpropane trimethacrylate, the remaining trimethylolpropane trimethacrylate is not sufficient to play the role of a co-curing agent between the two layers, resulting in poor adhesion between the second layer and the third layer of the track foaming vibration damping pad and slight delamination; from the comparison between Comparative Example 2 and Example 1, it can be seen that when directly using PET geotextile, the service performance of the track foaming vibration damping pad is poor.

[0120] The above embodiments are only for illustrating the technical concept and features of the present invention, and the purpose is to enable those who are familiar with this technology to understand the content of the present invention and implement it. It should not be used to limit the protection scope of the present invention. Any equivalent changes or modifications made according to the spirit and essence of the present invention should be covered within the protection scope of the present invention.

Claims

1. An orbital foamed vibration damping pad, characterized in that, The track foaming vibration damping pad 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 subjecting them to die molding and vulcanization; the first layer of material is a rubber vulcanized once. By weight, the rubber includes the following raw materials: 40-50 parts of ethylene propylene diene monomer 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-foaming low Mooney rubber; the third layer of material is a modified PET geotextile; The preparation method of the microsphere foaming agent comprises the following steps: A1. Add sodium bicarbonate, 3-isocyanatopropyltrimethoxysilane and acetone into a reaction vessel, heat up to 30-40 °C and react for 20-30 min, and obtain silane-modified sodium bicarbonate after drying; A2. Add the silane-modified sodium bicarbonate, catalyst, acetone and polyurethane prepolymer obtained in step A1 into a reaction vessel, react at 30-40 °C for 1-2 h, and obtain the microsphere foaming agent after drying; The mass ratio of the sodium bicarbonate to the 3-isocyanatopropyltrimethoxysilane is 1:(0.2-0.3); In step A2, the mass ratio of the silane-modified sodium bicarbonate to the polyurethane prepolymer is 1:(1-1.2); The preparation method of the modified PET geotextile comprises the following steps: B1. Immerse the PET geotextile in a 23-27 g / L dilute nitric acid solution at 70-90 °C for 20-40 min, wash and dry it, then immerse it in a mixed aqueous solution of sodium sulfide and sodium carbonate, react at 95-98 °C for 20-40 min, wash and dry it to obtain amino-PET geotextile; B2. Immerse the amino-PET geotextile obtained in step B1 in a 20-30 wt% acrylic acid methanol solution, heat to 70-80 °C and react for 1-2 h to obtain acrylic acid-modified PET geotextile; B3. Add trimethylolpropane trimethacrylate, anhydrous methanol and azobisisobutyronitrile into a reaction vessel, stir for 20-30 min to obtain a mixed solution, immerse the acrylic acid-modified PET geotextile obtained in step B2 in the mixed solution, and react at 70-80 °C for 1-3 h to obtain the modified PET geotextile; In step B2, the impregnation ratio of the amino-PET geotextile to the 20-30 wt% acrylic acid methanol solution is 1:(4-5); In step B3, the mass ratio of the anhydrous methanol to the trimethylolpropane trimethacrylate is 1:(0.05-0.1).

2. The track foamed vibration damping pad according to claim 1, 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.

3. A method for preparing the track foamed vibration damping pad according to any one of claims 1-2, characterized in that, Comprises the following steps: (1) Put the ethylene propylene diene monomer rubber into a mixer for plasticizing, the plasticizing temperature is 70-80 °C, and the plasticizing time is 20-25 min to obtain the plasticized rubber; (2) Add the plasticized rubber, vulcanization accelerator, carbon black and paraffin oil obtained in step (1) into the mixer for mixing at the same time, the mixing temperature is 80-110 °C, and the mixing time is 10-20 min to obtain the mixed rubber; (3) Put the kneaded rubber obtained in step (2) into an open mill, add a vulcanizing agent and a microsphere blowing agent, mix evenly at 40 - 45 °C, then adjust the roll gap to 0.8 - 1.3 mm, make 3 - 5 triangle wraps, and then adjust the roll gap to 5 - 6 mm to take out the sheet. Let the sheet stand for 2 - 15 days, then put it on a cutting machine to cut into rubber strips, add them into an extruder for extrusion, and obtain the formed rubber after cutting. (4) Vulcanize the formed rubber obtained in step (3) in a flat vulcanizer. The vulcanization temperature is 165 °C - 175 °C and the vulcanization time is 20 - 30 min to obtain the once-vulcanized rubber. (5) Grind the once-vulcanized rubber obtained in step (4) using a grinding machine to obtain the ground rubber. (6) Calender the non-foaming low Mooney rubber. The calendering specifications are 0.8 - 1.2 mm in thickness and 230 - 250 mm in width. After calendering, cut the length to 620 - 660 mm to obtain the calendered rubber. (7) Put the ground rubber obtained in step (5), the calendered rubber obtained in step (6), and the modified PET geotextile into the mold cavity in sequence, close the mold and vulcanize. The vulcanization temperature is 165 °C - 175 °C, the vulcanization time is 5 - 7 min, and the pressure is 140 - 160 kg / cm² to obtain the track foaming vibration damping pad.

4. The preparation method of the track foamed vibration damping pad according to claim 3, characterized in that, The thickness of the once-vulcanized rubber is 25 - 25.5 mm, and the thickness of the ground rubber is 24.5 - 25 mm.

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