A rail transit welding sealant and its preparation method

Abstract

This application discloses a rail transit welding sealant and its preparation method. The sealant comprises the following raw materials in parts by weight: 80-120 parts of silane-modified polymer, 60-100 parts of plasticizer, 150-210 parts of modified filler, 2-10 parts of thixotropic agent, 0.5-3 parts of UV stabilizer, 0.5-3 parts of light stabilizer, 0.5-3 parts of heat stabilizer, 3-6 parts of dehydrating agent, 3-6 parts of silane coupling agent, 3-7 parts of curing agent, and 6-12 parts of silane oligomer, wherein the silane oligomer is an epoxy-amino silane oligomer. The silane-modified polymer forms a cross-linked network structure with flexible polymer long chains connected by siloxane-silicon bonds as cross-linking points. The silane oligomer can increase the cross-linking density of the sealant, and the silanol groups contained therein and the active groups in the silane oligomer can form chemical bonds with the substrate, enhancing the adhesion strength with various substrates.

Description

Technical Field

[0001] This application relates to the field of track sealants, and in particular to a track transportation calcined welding sealant and its preparation method. Background Technology

[0002] To meet the requirements of railway speed increase and heavy load, rail transit often considers lightweight design and adopts a design that reduces the thickness of some steel plates; however, due to the reduction in steel plate thickness, corrosion is prone to occur in stress-bearing parts, welded parts, and parts with liquid residue, so it is necessary to replace them.

[0003] Replacing welding with adhesive bonding in replacement work can reduce labor intensity and improve repair efficiency. Simultaneously, the use of sealant for localized sealing can significantly slow down the occurrence and development of corrosion. However, commercially available welding sealants exhibit significant differences in adhesion to different substrates. Different types of welding sealant formulations are required to achieve the standard bonding performance for bonding different materials. Summary of the Invention

[0004] To address the issue of inconsistent adhesive performance of calcined welding sealant on different substrates, this application provides a calcined welding sealant for rail transit and its preparation method. The calcined welding sealant in this application maintains good adhesion to different substrates.

[0005] Firstly, this application provides a rail transit section sealant, comprising the following raw material components in parts by weight:

[0006] 80-120 parts of silane-modified polymer;

[0007] Plasticizer 60-100 parts;

[0008] 150-210 parts of modified filler;

[0009] Thixotropic agent 2-10 parts;

[0010] UV protectant 0.5–3 parts;

[0011] Light stabilizer 0.5–3 parts;

[0012] Heat stabilizer 0.5–3 parts;

[0013] 3-6 parts of dehydrating agent;

[0014] 3-6 parts of silane coupling agent;

[0015] 3-7 parts of curing agent;

[0016] 6-12 parts of silane oligomers;

[0017] The silane oligomer is an epoxy-amino silane oligomer.

[0018] Preferably, the silane-modified polymer includes one or a combination of several of silane-modified polyethers and silane-modified polyurethanes.

[0019] Preferably, the silane-modified polymers include SAX350, SAX400, SAX750, S888E, S3430E, STP-E15, STP-E35, and SPUR+. * 1015, SPUR+ * 1050, SPUR+ * One or more of 3030.

[0020] Preferably, the plasticizer includes one or a combination of several of diisononyl phthalate, diisooctyl phthalate, diisodecyl phthalate, and polypropylene glycol.

[0021] Preferably, the UV stabilizer comprises one or a combination of several of 2-(2'-hydroxy-5'-methylphenyl)benzotriazole, 2-(2'-hydroxy-3'-tert-butyl-5'-methylphenyl)-5-chlorobenzotriazole, and 2-(2'-hydroxy-3',5'-di-tert-butylphenyl)-5-chlorobenzotriazole.

[0022] Preferably, the thixotropic agent includes one or a combination of several of polyamide wax, hydrogenated castor oil, and silica.

[0023] Preferably, the light stabilizer comprises one or a combination of several of the following: bis-2,2,6,6-tetramethylpiperidinol sebacate, bis(1,2,2,6,6-pentamethylpiperidinol) sebacate, a polymer of succinic acid and 4-hydroxy-2,2,6,6-tetramethyl-1-piperidinol, and a mixture of bis(1,2,2,6,6-pentamethyl-4-piperidinol) sebacate and 1-methyl-8-(1,2,2,6,6-pentamethyl-4-piperidinol) sebacate.

[0024] Preferably, the heat stabilizer includes one or a combination of several of β-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate, ethylene bis(oxyvinyl)bis[3-(5-tert-butyl-4-hydroxy-m-tolyl)propionate], and tris(2,4-di-tert-butylphenyl) phosphite.

[0025] Preferably, the dehydrating agent comprises one or a combination of vinyltrimethoxysilane and vinyltriethoxysilane.

[0026] Preferably, the silane coupling agent includes one or a combination of several of γ-aminopropyltrimethoxysilane, γ-aminopropyltriethoxysilane, N-β-(aminoethyl)-γ-aminopropyltrimethoxysilane, γ-mercaptopropyltrimethoxysilane, γ-ureapropyltrimethoxysilane, γ-ureapropyltrihexyloxysilane, γ-methacryloyloxypropyltrimethoxysilane, and γ-glycidyl ether propyltrimethoxysilane.

[0027] Preferably, the curing agent includes one or more of bis(acetylacetonate) dibutyltin and dibutyltin laurate.

[0028] By adopting the above technical solution, the silane-modified polymer is end-capped with siloxane groups. After room temperature and humidity curing, it forms a cross-linked network structure with siloxane bonds as cross-linking points and flexible polymer long chains connected together. This can effectively prevent the formation of surface cracks in the sealant after long-term outdoor use. At the same time, the siloxane groups can be hydrolyzed into silanol groups under moisture, which can undergo condensation reaction with hydroxyl groups on the surface of various material substrates to form a siloxane structure. This structure has good wettability with various substrates, thus producing good adhesion to the substrate.

[0029] Preferably, the raw materials for the silane oligomer include an epoxy silane compound and an amino silane compound in a molar ratio of (0.4 to 0.6):1.

[0030] Preferably, the epoxy silane compound includes one or more of γ-glycidoxypropyltrimethoxysilane (3-glycidoxypropyltrimethoxysilane), γ-glycidoxypropyltriethoxysilane, 3-(2,3-epoxypropoxy)propylmethyldiethoxysilane, and 3-(2,3-epoxypropoxy)propyltrimethoxysilane; the amino silane compound includes one or more of 3-aminopropyltrimethoxysilane, γ-aminopropyltriethoxysilane, γ-aminoethylaminopropyltrimethoxysilane, γ-aminoethylaminopropylmethyldiethoxysilane, γ-aminoethylaminopropyltriethoxysilane, and γ-aminoethylaminopropylmethyldiethoxysilane.

[0031] Preferably, the polymer of the silane oligomer is 5 to 10.

[0032] The sealant also contains silane oligomers, which are polymerized from aminosilane and epoxysilane compounds. These oligomers contain regularly arranged amino groups that can bond with the active groups in the silane-modified polymer, increasing the crosslinking density of the sealant. This prevents small molecules such as plasticizers and heat stabilizers from precipitating out during use, increasing the sealant's structural stability and extending its service life. Simultaneously, the amino groups can connect with active groups on the substrate surface, enhancing the adhesion strength between the sealant and the substrate. The oligomers also contain hydrophobic epoxy groups, which effectively inhibit chain breakage and interfacial separation caused by water molecules entering the sealant gaps during outdoor use.

[0033] Preferably, the preparation process of the silane oligomer is as follows: an epoxy silane compound and an amino silane compound are added to a solvent, mixed evenly at 30-40°C, a catalyst is added and the pH of the solution is adjusted to 3-4, 55-65 wt% methanol aqueous solution is added dropwise, the temperature is raised to 80-90°C, the reaction is carried out for 6-12 hours, and then the silane oligomer is obtained by vacuum distillation.

[0034] Preferably, the solvent includes one or a combination of methanol and ethanol.

[0035] Preferably, the catalyst is an acid catalyst, including one or more of hydrochloric acid and nitric acid.

[0036] Preferably, the ratio of solvent mass to the total mass of epoxy silane compound and amino silane compound is (0.4-0.6):1; the catalyst mass is 2%-4% of the total mass of epoxy silane compound and amino silane compound.

[0037] Preferably, the methanol-deionized water mixture has a methanol mass fraction of 55-65% and a mixture mass of 20-40% of the total mass of the epoxy silane compound and amino silane compound.

[0038] By employing the above technical solution, the hydrolysis rate of silane compounds is relatively stable under acidic conditions, resulting in stable products. The silane compounds gradually hydrolyze in the solvent to form silanol groups, which then condense to yield epoxy-aminosilane oligomers.

[0039] Preferably, the modified filler is stearic acid modified calcium carbonate; the stearic acid modified calcium carbonate is prepared by wet modification of modified stearic acid and calcium carbonate in a mass ratio of (2-4):100.

[0040] Preferably, the bulk density of calcium carbonate is 0.8–1.3 g / cm³. 3 .

[0041] The preferred wet modification process for stearic acid-modified calcium carbonate is as follows:

[0042] Calcium carbonate and deionized water are mixed evenly to prepare a calcium carbonate slurry with a mass fraction of 8-12%. Modified stearic acid, weighed at 2-4% of the mass of calcium carbonate, is dissolved in anhydrous ethanol to prepare a modifier alcohol solution with a mass fraction of 20-30%. The modifier alcohol solution is added to the calcium carbonate slurry and stirred at 60-90℃ for 80-90 minutes. After the reaction is completed, the mixture is cooled to room temperature, filtered, washed, and dried to obtain stearic acid modified calcium carbonate.

[0043] By employing the above technical solution, calcium carbonate, with its numerous hydroxyl groups and strong surface polarity, exhibits poor compatibility with silane-modified polymers, making it difficult to disperse uniformly in the matrix. This results in low interfacial bonding, easily leading to interfacial defects and agglomeration during use, thus degrading material performance. Stearic acid molecules, on the other hand, contain a long-chain alkyl group at one end, exhibiting good compatibility with silane-modified polymers, and an RCOO- group at the other end, which can form chemical bonds with calcium ions on the calcium carbonate surface, creating an active coating layer. This effectively increases the compatibility between calcium carbonate and the polymer, preventing agglomeration of calcium carbonate.

[0044] Preferably, the raw materials for the modified stearic acid include glyceryl monostearate and a dianhydride compound in a molar ratio of 1:(1.5-2.5).

[0045] Preferably, the dianhydride compound includes one or a combination of several of acetic anhydride, propionic anhydride, succinic anhydride, and maleic anhydride.

[0046] The bonding between stearic acid and calcium carbonate is a single-point anchoring process. The single anchoring group in stearic acid, namely the RCOO- group, combines with the polar groups on the surface of calcium carbonate, resulting in a low degree of anchoring. Consequently, the surface modification effect of calcium carbonate is poor, affecting the performance of the sealant. At the same time, the process of stearic acid modifying calcium carbonate is a dynamic process. Some stearic acid fails to anchor with calcium carbonate, and the surface properties of calcium carbonate also have certain differences, all of which reduce the degree of anchoring of stearic acid to calcium carbonate to some extent.

[0047] By adopting the above technical solution, stearic acid, through modification treatment, increases the anchoring groups between it and calcium carbonate. One end of the modified stearic acid molecule contains two RCOO- groups. Modifying calcium carbonate with multiple anchoring points increases the probability of binding between stearic acid and calcium carbonate, increasing the degree of anchoring, thereby improving the surface modification effect of calcium carbonate, reducing calcium carbonate agglomeration, increasing compatibility with the substrate, and thus improving the overall performance of the sealant and its adhesion to the substrate. Furthermore, the modified filler obtained by modifying calcium carbonate with stearic acid can chemically bond with silane oligomers. The partially reacted RCOO- groups on the surface of the modified filler can form a cross-linked structure with the silane oligomers, increasing the cross-linking density of the sealant. This not only improves the sealant's own performance but also effectively prevents the precipitation of small molecules such as plasticizers, UV stabilizers, and heat stabilizers, thus improving the stability of the sealant.

[0048] Preferably, the preparation process of the modified stearic acid is as follows: glyceryl monostearate and dianhydride compound are added to a solvent to prepare a 7-9 wt% mixed solution. After stirring for 10-20 min, a catalyst is added, the solution is heated to 85-95°C, and the reaction is continued under constant temperature for 8-10 h. After washing, drying, and vacuum rotary evaporation, modified stearic acid is obtained.

[0049] Preferably, the solvent is toluene; the catalyst is one or more of sulfuric acid, phosphoric acid, and p-toluenesulfonic acid.

[0050] Preferably, the amount of catalyst added is 0.5% to 1% of the mass of glyceryl monostearate.

[0051] By adopting the above technical solution, glyceryl monostearate and dianhydride compounds undergo esterification under the catalysis of an acid catalyst. One end of the glyceryl monostearate molecule contains two hydroxyl groups, which can react with the anhydride in the dianhydride compound to form an ester group that links the two together. At the same time, the other end of the dianhydride compound forms an RCOO- group, so that the modified stearic acid has two anchoring groups, thereby increasing the degree of anchoring with calcium carbonate.

[0052] Secondly, this application also provides a method for preparing a rail transit welding sealant, comprising the following steps:

[0053] S1: Mix the silane-modified polymer, plasticizer, modified filler, thixotropic agent, UV stabilizer, light stabilizer and heat stabilizer evenly, and then stir under vacuum at a speed of 600-800 rpm for 50-70 min.

[0054] S2: After mixing evenly, heat to 100-120℃ and stir at 300-600 rpm for 100-130 minutes to dehydrate;

[0055] S3: After stirring, cool to 40-50℃, add dehydrating agent, silane oligomer, silane coupling agent and curing agent in sequence, and stir at 240-260 rpm for 20-30 minutes. After stirring, obtain rail transit calcined welding sealant through vacuum dispersion.

[0056] Preferably, the vacuum degree under vacuum conditions is -0.09 to -0.1 MPa.

[0057] In summary, this application has the following beneficial effects:

[0058] 1. The silane-modified polymer used in this application employs siloxane-based end-capping to form a cross-linked network structure. Simultaneously, the siloxane-based end-capping agent hydrolyzes into silanol groups under humid conditions, which can undergo condensation reactions with hydroxyl groups on the surface of various substrates to form a silicon-oxygen-silicon structure. This structure exhibits good wettability with various substrates, resulting in excellent adhesion. Silane oligomers are also added to the sealant. The regularly arranged amino groups within these oligomers can bond with the active groups in the silane-modified polymer, increasing the cross-linking density and improving the sealant's performance. Furthermore, the amino groups can connect with the active groups on the substrate surface, enhancing the bond strength between the sealant and the substrate. The oligomers also contain hydrophobic epoxy groups, which effectively inhibit chain segment breakage caused by water molecules entering the sealant gaps and prevent interfacial separation from the substrate, increasing the structural stability of the sealant and extending its service life.

[0059] 2. The modified filler added in this application is stearic acid-modified calcium carbonate. The modified calcium carbonate has good compatibility with silane-modified polymers, improving the performance of the sealant. Stearic acid, through modification, contains multiple anchoring groups that can combine with the polar groups on the surface of calcium carbonate, increasing the anchoring degree, reducing calcium carbonate agglomeration, and increasing compatibility with the substrate, thus better enhancing the substrate material. Simultaneously, the multi-anchored modified calcium carbonate can crosslink with silane oligomers, increasing the crosslinking density, effectively inhibiting the precipitation of small molecules, increasing the stability of the sealant, and extending its service life. Detailed Implementation

[0060] Preparation examples of silane oligomers

[0061] Preparation Example 1-1: A silane oligomer was prepared according to the following method:

[0062] Take 1 mol of 3-aminopropyltrimethoxysilane (360 g) and 0.5 mol of 3-(2,3-epoxypropoxy)propyltrimethoxysilane (240 g) and add them to 300 g of methanol. Mix them evenly at 35 °C, add 18 g of hydrochloric acid and adjust the pH of the solution to 4. Add 180 g of 60 wt% methanol aqueous solution dropwise, raise the temperature to 85 °C, react for 10 h, and then obtain the silane oligomer by vacuum distillation.

[0063] Preparation Example 1-2, a silane oligomer, differs from Preparation Example 1-1 only in that the amount of 3-(2,3-epoxypropoxy)propyltrimethoxysilane added is 0.4 mol.

[0064] Preparation Examples 1-3, a silane oligomer, differs from Preparation Example 1-1 only in that the amount of 3-(2,3-epoxypropoxy)propyltrimethoxysilane added is 0.6 mol.

[0065] Preparation Examples 1-4, a silane oligomer, differ from Preparation Example 1-1 in that the amount of methanol added is 360g, the amount of hydrochloric acid added is 24g, and the amount of 60wt% methanol aqueous solution added is 240g.

[0066] Preparation Examples 1-5, a silane oligomer, differ from Preparation Example 1-1 in that the amount of methanol added is 240g, the amount of hydrochloric acid added is 12g, and the amount of 60wt% methanol aqueous solution added is 120g.

[0067] Preparation Examples 1-6: A silane oligomer, differing from Preparation Example 1-1 only in that the amount of 3-(2,3-epoxypropoxy)propyltrimethoxysilane added is 0.3 mol.

[0068] Preparation Examples 1-7: A silane oligomer, differing from Preparation Example 1-1 only in that the amount of 3-(2,3-epoxypropoxy)propyltrimethoxysilane added is 0.7 mol.

[0069] Preparation Examples 1-8: A silane oligomer, differing from Preparation Example 1-1 only in that 3-(2,3-epoxypropoxy)propyltrimethoxysilane is replaced with 0.5 mol of 3-aminopropyltrimethoxysilane.

[0070] Preparation Examples 1-9: A silane oligomer, differing from Preparation Example 1-1 only in that 1 mol of 3-(2,3-epoxypropoxy)propyltrimethoxysilane is used instead of 3-aminopropyltrimethoxysilane.

[0071] Preparation example of modified stearic acid

[0072] Preparation Example 2-1: A modified stearic acid was prepared according to the following method:

[0073] 36g of glyceryl monostearate and 20g of succinic anhydride were added to 700g of toluene to prepare an 8wt% mixed solution. After stirring for 15min, 0.3g of sulfuric acid was added, and the solution temperature was raised to 90℃. Stirring was continued at a constant temperature for 8h. The solution was then washed with deionized water, and the oil phase was collected. The oil phase was dried in anhydrous magnesium sulfate for 24h and then filtered to obtain the solid. The oil phase was collected and the toluene was removed by vacuum rotary evaporation at 50℃ to obtain modified stearic acid.

[0074] Preparation Example 2-2, a modified stearic acid, differs from Preparation Example 2-1 only in that the amount of succinic anhydride added is 15g.

[0075] Preparation Example 2-3 is a modified stearic acid, which differs from Preparation Example 2-1 only in that the amount of succinic anhydride added is 25g.

[0076] Preparation example of stearic acid modified calcium carbonate

[0077] Preparation Example 3-1: A stearic acid-modified calcium carbonate was prepared according to the following method:

[0078] Take 1 kg of calcium carbonate (particle size 1-3 μm) and mix it with deionized water to prepare a 10 wt% calcium carbonate slurry. Take 30 g of the modified stearic acid prepared in Preparation Example 2-1 and mix it with anhydrous ethanol to prepare a 25 wt% modifier alcohol solution. Add the obtained modifier alcohol solution to the calcium carbonate slurry and stir the reaction at 70 °C for 80 min. After the reaction is completed, cool it to room temperature, and then filter, wash and dry to obtain stearic acid modified calcium carbonate.

[0079] Preparation Example 3-2 is a stearic acid modified calcium carbonate, which differs from Preparation Example 3-1 only in that the amount of modified stearic acid added in Preparation Example 2-2 is 40g.

[0080] Preparation Example 3-3 is a stearic acid modified calcium carbonate, which differs from Preparation Example 3-1 only in that the amount of modified stearic acid added in Preparation Example 2-3 is 20g.

[0081] Preparation Example 3-4 is a stearic acid modified calcium carbonate, which differs from Preparation Example 3-1 only in that the amount of modified stearic acid added in Preparation Example 2-1 is 15g.

[0082] Preparation Example 3-5 is a stearic acid modified calcium carbonate, which differs from Preparation Example 3-1 only in that the amount of modified stearic acid added in Preparation Example 2-1 is 45g.

[0083] Preparation Examples 3-6: A stearic acid modified calcium carbonate, which differs from Preparation Example 3-1 only in that an equal amount of stearic acid is used to replace the modified stearic acid prepared in Preparation Example 2-1.

[0084] Example

[0085] Example 1: A rail transit welding sealant, prepared according to the following method:

[0086] Take 1000g of silane-modified polyether (model S3430E), 800g of polypropylene glycol (average molecular weight 3000), 1800g of stearic acid-modified calcium carbonate prepared in Preparation Example 3-1, 60g of polyamide wax, 20g of 2-(2'-hydroxy-5'-methylphenyl)benzotriazole, 15g of bis-2,2,6,6-tetramethylpiperidinol sebacate, and 20g of antioxidant 1076 and put them into a double planetary mixer. After evacuating to a vacuum degree of 980mbar, stir at 800rpm for 60min.

[0087] After mixing evenly, heat to 100°C and continue stirring at 500 rpm for 120 minutes to dehydrate;

[0088] After stirring, the temperature was lowered to 40°C, and 45g of vinyltrimethoxysilane, 90g of the silane oligomer prepared in Preparation Example 1-1, 45g of γ-aminopropyltriethoxysilane and 50g of dibutyltin dilaurate were added in sequence. The mixture was stirred at 250 rpm for 30 min. After all the mixture was added and mixed, it was dispersed under vacuum to obtain the rail transit calcined welding sealant.

[0089] Example 2, a rail transit welding sealant, differs from Example 1 only in that it uses an equal amount of silane-modified polyurethane (model SPUR+). * 1050) Replace silane-modified polyether.

[0090] Examples 3 to 18 describe a rail transit welding sealant, which differs from Example 1 only in the proportions of the raw materials used, as shown in Table 1.

[0091] Table 1. Formulations for Examples 1, 3 to 18

[0092]

[0093]

[0094] In this example, Examples 3 and 4 used the silane oligomers prepared in Examples 1-2; Examples 5 and 6 used stearic acid modified calcium carbonate prepared in Examples 3-2; Examples 7 and 8 used the silane oligomers prepared in Examples 1-3; Examples 9 and 10 used stearic acid modified calcium carbonate prepared in Examples 3-3; Examples 11 and 12 used the silane oligomers prepared in Examples 1-4; and Examples 13 and 14 used the silane oligomers prepared in Examples 1-5.

[0095] Example 19, a rail transit welding sealant, differs from Example 1 only in that an equal amount of the silane oligomers prepared in Examples 1-6 are used to replace the silane oligomers prepared in Examples 1-1.

[0096] Example 20, a rail transit welding sealant, differs from Example 1 only in that an equal amount of the silane oligomers prepared in Examples 1-7 are used to replace the silane oligomers prepared in Examples 1-1.

[0097] Example 21, a rail transit welding sealant, differs from Example 1 only in that an equal amount of stearic acid modified calcium carbonate prepared in Example 3-4 is used to replace the stearic acid modified calcium carbonate prepared in Example 3-1.

[0098] Example 22, a rail transit welding sealant, differs from Example 1 only in that an equal amount of stearic acid modified calcium carbonate prepared in Preparation Examples 3-5 is used to replace the stearic acid modified calcium carbonate prepared in Preparation Example 3-1.

[0099] Example 23, a rail transit welding sealant, differs from Example 1 only in that an equal amount of stearic acid modified calcium carbonate prepared in Examples 3-6 is used to replace the stearic acid modified calcium carbonate prepared in Example 3-1.

[0100] Comparative Example

[0101] Comparative Example 1, a rail transit welding sealant, differs from Example 2 only in that an equal amount of polyurethane adhesive is used instead of silane-modified polyurethane.

[0102] Comparative Example 2, a rail transit welding sealant, differs from Example 1 only in that an equal amount of the silane oligomers prepared in Examples 1-8 are used to replace the silane oligomers prepared in Examples 1-1.

[0103] Comparative Example 3, a rail transit welding sealant, differs from Example 1 only in that an equal amount of the silane oligomers prepared in Examples 1-9 are used to replace the silane oligomers prepared in Examples 1-1.

[0104] Comparative Example 4, a rail transit welding sealant, differs from Example 1 only in that an equal amount of unmodified calcium carbonate is used to replace the stearic acid-modified calcium carbonate prepared in Preparation Example 3-1.

[0105] Comparative Example 5, a rail transit welding sealant, differs from Example 1 only in that the amount of silane oligomer added in Preparation Example 1-1 is 50g.

[0106] Comparative Example 6, a rail transit welding sealant, differs from Example 1 only in that the amount of silane oligomer added in Preparation Example 1-1 is 140g.

[0107] Comparative Example 7, a rail transit welding sealant, differs from Example 1 only in that the silane oligomers prepared in Preparation Example 1-1 are not added.

[0108] Performance testing

[0109] 1. Tensile Adhesion Test: The adhesion of the sealants in Examples 1-23 and Comparative Examples 1-7 was tested according to GB / T 13477.8-2017 "Test Methods for Building Sealing Materials - Part 8: Determination of Tensile Adhesion". Aluminum plates were selected as the bonding substrate. The tensile adhesion of the sealants was tested at (23±2)℃ to obtain the secant tensile modulus. The test results are shown in Table 2.

[0110] 2. Adhesion Tests on Different Substrates: The peel adhesion of the sealants in Examples 1-23 and Comparative Examples 1-7 on different substrate surfaces was tested according to GB / T 13477.18-2017 "Test Methods for Building Sealing Materials - Part 18: Determination of Peel Adhesion". The selected substrates included fiberglass, stainless steel, carbon steel, alumina, and carbon fiber sheets. The peel strength of the sealants and the failure modes of the specimens (adhesive failure (AF) and / or cohesive failure (CF)) were tested. The test results are shown in Table 3.

[0111] 3. Weathering Resistance Test: The weathering resistance of Examples 1-23 and Comparative Examples 1-7 sealants was tested according to GB / T 14522-2008 "Artificial Climate Aging Test Method for Plastics, Coatings and Rubber Materials for Mechanical Industry Products - Fluorescent Ultraviolet Lamp". The test conditions were as described in Exposure Cycle Type 2 in Appendix C of the standard, with an aging time of 2000 hours. The presence or absence of cracking, chalking, or blackening was recorded. The test results are shown in Table 4.

[0112] 4. Precipitation Test: The sample was coated onto the surface of an aluminum alloy plate with a thickness of 2±0.5 mm. The sample was cured according to the curing standards in GB / T 13477-2017. After curing, the sample was placed in the same environment and left to stand for 28 days. The precipitation on the sample surface was compared, and divided into 5 levels: no precipitation (Level 1), slight precipitation (Level 2), precipitation (Level 3), significant precipitation (Level 4), and severe precipitation (Level 5). The test results are shown in Table 5.

[0113] Table 2 Results of Tensile Adhesion Test

[0114]

[0115]

[0116] Table 3. Adhesion test results for different substrates

[0117]

[0118]

[0119] Table 4 Results of Aging Resistance Test

[0120]

[0121]

[0122] Note: × indicates no obvious cracking, no obvious powdering, and no blackening; √ indicates obvious cracking, powdering, and blackening.

[0123] Table 5. Results of the precipitation experiment

[0124]

[0125] Based on Tables 2, 3, 4, and 5, and in conjunction with Examples 1 and 2, it can be seen that Example 2 shows no significant change in tensile modulus compared to Example 1, and no significant difference in peel strength with different substrates compared to Example 1. The failure mode is cohesive failure in both examples. No obvious cracking or powdering was observed in the aging test, and no blackening occurred. No precipitation was observed in the precipitation test. This indicates that Example 2 shows no significant change in tensile properties, adhesion, weather resistance, and low precipitation compared to Example 1. The reason for this may be that Example 2 changed the type of polymer in the silane-modified polymer compared to Example 1, replacing polyether with polyurethane. This suggests that silane-modified polyurethane and polyether have similar effects on the sealant's performance.

[0126] Combining Example 2 and Comparative Example 1, it can be seen that Comparative Example 1 shows a significant decrease in tensile modulus and peel strength to various substrates compared to Example 2. The failure mode in both examples is adhesive failure, with obvious cracking and powdering during aging. Comparative Example 1 also exhibits severe exudation. This indicates that Comparative Example 1 shows a significant decrease in tensile properties, adhesion, weather resistance, and low exudation compared to Example 2. The reason for this may be that in Comparative Example 1, polyurethane adhesive replaced silane-modified polyurethane, resulting in a lack of silanol groups during curing. On the one hand, the cross-linked network structure of siloxane and silicon cannot be formed, significantly reducing the sealant's performance and making it easier for small molecules to precipitate onto the sealant surface. On the other hand, it cannot form a chemical bond with the hydroxyl groups on the substrate surface, significantly reducing adhesion to the substrate.

[0127] Combining Example 1 and Comparative Example 2, it can be seen that the tensile modulus and peel strength to various substrates of Comparative Example 2 are lower than those of Example 1. Slight exudation is observed, and significant cracking and powdering occur during the aging process. This indicates that the tensile properties, adhesion, and low exudation of Comparative Example 2 are lower than those of Example 1, and the weather resistance of the sealant is significantly reduced. The reason for this may be that the silane oligomer in Comparative Example 2 does not contain epoxy groups. Epoxy groups can provide active crosslinking points, increase the crosslinking density of the sealant, and improve its performance. Most importantly, epoxy groups are hydrophobic groups, which can effectively block water molecules from entering the sealant and the pores between the sealant and the substrate. Without the effect of epoxy groups, the aging performance of the sealant will decrease during the aging test.

[0128] Combining Example 1 and Comparative Example 3, it can be seen that the tensile modulus and peel strength to various substrates of Comparative Example 3 are significantly lower than those of Example 1. The failure mode in Comparative Example 3 is adhesive failure, with significant exudation, indicating that the tensile properties, adhesion, and low exudation of Comparative Example 3 are significantly lower than those of Example 1. This may be because the silane oligomer added in Comparative Example 3 does not contain amino groups. The lack of amino groups reduces the crosslinking density of the sealant, resulting in decreased sealant performance and increased exudation of small molecules. Furthermore, it reduces the adhesive strength between the sealant and the substrate, leading to decreased adhesion.

[0129] Combining Example 1 and Comparative Example 4, it can be seen that Comparative Example 4 shows a significant decrease in tensile modulus and peel strength to various substrates compared to Example 1. The failure mode is partly adhesive failure with the precipitation of small molecules. Significant cracking and powdering are observed during aging, indicating that Comparative Example 4 exhibits a significant decrease in tensile properties, adhesion, low precipitation, and weather resistance compared to Example 1. This may be because the filler in Comparative Example 4 was not modified; specifically, the calcium carbonate was not modified with stearic acid. This filler is prone to agglomeration during sealant preparation, has poor compatibility with silane-modified polymers, and provides poor performance enhancement to the silane-modified polymers, resulting in low-performance sealant with poor adhesion. Furthermore, the lack of modification prevents cross-linking with silane oligomers, leading to decreased cross-linking density and increased precipitation of small molecules.

[0130] Based on Examples 1, 5, and 6, it can be seen that the tensile modulus and peel strength to various substrates of Comparative Examples 5 and 6 decreased compared to Example 1, with slight precipitation of small molecules. Comparative Example 5 exhibited significant cracking during aging, indicating that the tensile properties and adhesion of Comparative Examples 5 and 6 decreased compared to Example 1, and the weather resistance of Comparative Example 5 also decreased significantly. This may be because the reduced amount of silane oligomers in Comparative Example 5 led to a decrease in the crosslinking density of the sealant, slight precipitation of small molecules, reduced binding between amino groups and the substrate, and decreased water-transporting capacity of the epoxy groups, thus reducing the sealant's performance and weather resistance. In Comparative Example 6, the increased amount of silane oligomers made it easier for the oligomers to undergo condensation polymerization, reducing crosslinking and sealing with the silane oligomers, resulting in a decrease in sealant performance.

[0131] Combining Example 1 and Comparative Example 7, it can be seen that Comparative Example 7 shows a significant decrease in tensile modulus and peel strength to various substrates compared to Example 1. The failure mode is adhesive failure, with more small molecule substances precipitating out. Significant cracking and powdering are observed during aging, indicating that Comparative Example 7 exhibits a significant decrease in tensile properties, adhesion, low precipitate activity, and weather resistance compared to Example 1. This may be because Comparative Example 7 did not contain silane oligomers, resulting in a significant decrease in the crosslinking density within the sealant, making it difficult to suppress the precipitation of small molecules, thus reducing the sealant's performance and its adhesion to the substrate.

[0132] Combining Examples 1 and 3-18, it can be seen that the tensile modulus of Examples 3-18 is not significantly different from that of Example 1, and the peel strength with different substrates is not significantly different from that of Example 1. The failure mode is cohesive failure in all examples, and there is no obvious cracking, powdering, or blackening in the aging test. This indicates that the tensile properties, adhesion, and weather resistance of Examples 3-18 are not significantly different from those of Example 1. The reason for this may be that Examples 3-18 only changed the ratio of sealant raw materials within the required range, indicating that changing the raw material ratio within the required range has no significant impact on the performance of the sealant.

[0133] Based on Examples 1, 19, and 20, it can be seen that the tensile modulus and peel strength to various substrates of Examples 19 and 20 are slightly lower than those of Example 1, and small molecule substances are slightly precipitated, indicating that the tensile properties and adhesion of Examples 19 and 20 are slightly lower than those of Example 1. This may be because the epoxy group content is reduced in Example 19, resulting in fewer reactive sites for crosslinking with the silane-modified polymer, a lower crosslinking density, and thus a decrease in performance; while the epoxy group content is increased in Example 20. During the preparation of silane oligomers, excessively high epoxy group concentration leads to a relatively lower degree of hydrolysis of the silane compound, an increase in the number of silanols, which can trigger polycondensation. This results in a decrease in the content of active groups in the obtained silane oligomer, leading to a decrease in the degree of crosslinking with the silane-modified polymer and a reduction in the performance of the sealant.

[0134] Based on Examples 1, 21, and 22, it can be seen that the tensile modulus and peel strength from various substrates in Examples 21 and 22 are slightly lower than those in Example 1, indicating a slight decrease in tensile properties and adhesion compared to Example 1. This may be because Example 21 reduced the amount of stearic acid-modified calcium carbonate, decreasing its reinforcing effect on the sealant and thus lowering its overall performance; while Example 22 increased the amount of stearic acid-modified calcium carbonate, increasing the likelihood of calcium carbonate agglomeration, leading to a slight decrease in the sealant's performance.

[0135] Combining Examples 1 and 23, it can be seen that the tensile modulus and peel strength to various substrates of Example 23 are lower than those of Example 1, indicating that the tensile properties and adhesion of Example 23 are lower than those of Example 1, and small molecule substances are precipitated. This may be because the stearic acid in the stearic acid-modified calcium carbonate of Example 23 was not modified; the bond between stearic acid and calcium carbonate is a single-anchored bond with a low degree of anchoring, resulting in poor surface modification of calcium carbonate and affecting the performance of the sealant. Simultaneously, the single-anchored modified calcium carbonate is difficult to crosslink with silane oligomers, leading to a decrease in the crosslinking density of the sealant and making it easier for small molecule substances to precipitate.

[0136] This specific embodiment is merely an explanation of this application and is not intended to limit it. After reading this specification, those skilled in the art can make modifications to this embodiment without contributing any inventive step, but such modifications are protected by patent law as long as they fall within the scope of the claims of this application.

Claims

1. A rail transit welding sealant, characterized in that, The raw material composition includes the following parts by weight: 80-120 parts of silane-modified polymer; Plasticizer 60-100 parts; 150-210 parts of modified filler; Thixotropic agent 2-10 parts; UV protectant 0.5–3 parts; Light stabilizer 0.5–3 parts; Heat stabilizer 0.5–3 parts; 3-6 parts of dehydrating agent; 3-6 parts of silane coupling agent; 3-7 parts of curing agent; 6-12 parts of silane oligomers; The silane oligomer is an epoxy-amino silane oligomer; The raw materials for the silane oligomer include epoxy silane compounds and amino silane compounds in a molar ratio of (0.4-0.6):1; The modified filler is stearic acid modified calcium carbonate; the stearic acid modified calcium carbonate is prepared by wet modification of modified stearic acid and calcium carbonate in a mass ratio of (2-4):100, and the raw materials of the modified stearic acid include glyceryl monostearate and dianhydride compound in a molar ratio of 1:(1.5-2.5).

2. The rail transit welding sealant according to claim 1, characterized in that, The silane-modified polymer includes one or a combination of several of silane-modified polyethers and silane-modified polyurethanes.

3. The rail transit welding sealant according to claim 1, characterized in that, The plasticizer includes one or a combination of several of diisononyl phthalate, diisooctyl phthalate, diisodecyl phthalate, and polypropylene glycol.

4. The rail transit welding sealant according to claim 1, characterized in that, The UV stabilizer includes one or a combination of several of 2-(2'-hydroxy-5'-methylphenyl)benzotriazole, 2-(2'-hydroxy-3'-tert-butyl-5'-methylphenyl)-5-chlorobenzotriazole, and 2-(2'-hydroxy-3',5'-di-tert-butylphenyl)-5-chlorobenzotriazole.

5. The rail transit welding sealant according to claim 1, characterized in that, The preparation process of the silane oligomer is as follows: an epoxy silane compound and an amino silane compound are added to a solvent, mixed evenly at 30-40°C, a catalyst is added and the pH of the solution is adjusted to 3-4, 55-65 wt% methanol aqueous solution is added dropwise, the temperature is raised to 80-90°C, the reaction is carried out for 6-12 hours, and then the silane oligomer is obtained by vacuum distillation.

6. The rail transit welding sealant according to claim 1, characterized in that, The preparation process of the modified stearic acid is as follows: Glyceryl monostearate and dianhydride compound are added to a solvent to prepare a 7-9 wt% mixed solution. After stirring for 10-20 min, a catalyst is added, the solution is heated to 85-95℃, and the reaction is continued to be stirred at a constant temperature for 8-10 h. After washing, drying, and vacuum rotary evaporation, the modified stearic acid is obtained.

7. A method for preparing a rail transit welding sealant according to any one of claims 1 to 6, characterized in that, It is prepared by the following steps: S1: Mix the silane-modified polymer, plasticizer, modified filler, thixotropic agent, UV stabilizer, light stabilizer and heat stabilizer evenly, and then stir under vacuum at a speed of 600-800 rpm for 50-70 min. S2: After mixing evenly, heat to 100-120℃ and stir at 300-600 rpm for 100-130 minutes to dehydrate; S3: After stirring, cool to 40-50℃, add dehydrating agent, silane oligomer, silane coupling agent and curing agent in sequence, and stir at 240-260 rpm for 20-30 minutes. After stirring, obtain rail transit calcined welding sealant through vacuum dispersion.

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