High-temperature-resistant ms sealant and preparation method thereof

Abstract

The application provides a high-temperature-resistant MS sealant and a preparation method thereof. The MS sealant comprises a branched MS resin, the branched MS resin is a graft copolymer with polyethylene oxide as a main chain and polymethylvinylpropyl ether as a branch, and the graft copolymer is terminated by a silane end-capping agent. The MS sealant prepared by the application has excellent mechanical properties and long-term high-temperature resistance, and can continuously resist 120 DEG C for 21 days without breaking.

Description

Technical Field

[0001] This invention belongs to the field of sealant technology, specifically relating to a high-temperature resistant MS sealant, a method for preparing branched MS resin, the preparation method of the sealant, and its application. Background Technology

[0002] MS sealant (silane-modified polyether sealant) has been widely used in industries such as rail transportation, automotive, and aerospace due to its combination of the excellent weather resistance of silicone sealants and the high adhesion and paintability of polyurethane sealants. With the expansion of application areas and the increasing severity of application environments, higher demands are being placed on the performance of MS sealant, especially its high-temperature resistance. For example, the temperature of car bodies and black sealant strips exposed to sunlight in summer can exceed 70°C, and the temperature is even higher in engine compartments or areas near heat sources. Therefore, researching and improving the performance stability of MS sealant under long-term high-temperature conditions is crucial.

[0003] Currently, the maximum operating temperature of commercially available MS sealants is generally 120℃, but the endurance of MS sealants with different formulations at this temperature varies significantly. Sealants made from conventional linear MS resins may crack after 7 days of aging at 120℃, failing to meet the requirements for long-term high-temperature applications. Therefore, developing a high-temperature resistant MS sealant that can operate stably at 120℃ for extended periods and exhibits excellent performance has significant practical value. Summary of the Invention

[0004] The purpose of this invention is to overcome the shortcomings of existing MS sealants in terms of insufficient long-term high-temperature resistance, and to provide an MS sealant with excellent high-temperature resistance and its preparation method.

[0005] To achieve the above objectives, the present invention provides the following technical solution: In a first aspect, the present invention provides a high-temperature resistant MS sealant, the MS sealant comprising a branched MS resin, the branched MS resin being a graft copolymer with polyethylene oxide as the main chain and polymethyl vinyl propylene ether as the branch chain, and the ends of the graft copolymer being capped with a silane end-capping agent.

[0006] A second aspect of the present invention provides a method for preparing the above-mentioned branched MS resin, comprising the following steps: (1) The modified polyethylene oxide was dissolved in an organic solvent and grafted copolymerized with methyl vinyl propyl ether monomer in the presence of an initiator to obtain polyethylene oxide-g-polymethyl vinyl propyl ether graft copolymer. (2) In the presence of a catalyst, the graft copolymer obtained in step (1) is subjected to a capping reaction with a silane capping agent.

[0007] The present invention has the following beneficial effects: The sealant of this invention has excellent long-term high temperature resistance, and can withstand 120°C for 21 days without cracking, which far exceeds the resistance time of conventional linear MS sealant (which cracks after 7 days).

[0008] The sealant of this invention exhibits excellent adhesion to various substrates such as aluminum alloy, fiberglass, and glass.

[0009] The preparation method of this invention has a reasonable process design and is easy to industrialize. Detailed Implementation

[0010] To make the objectives, technical solutions, and advantages of this invention clearer, the technical solutions of this invention will be described in detail below with reference to specific embodiments. Obviously, the described embodiments are merely some embodiments of this invention, and not all embodiments. Based on the embodiments of this invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this invention.

[0011] In a first aspect, the present invention provides a high-temperature resistant MS sealant comprising a branched MS resin, wherein the branched MS resin is a graft copolymer with polyethylene oxide (PEO) as the main chain and polymethyl vinyl propylene ether (PMVE) as the branch chain (i.e., polyethylene oxide-g-polymethyl vinyl propylene ether, PEO-g-PMVE), and the ends of the graft copolymer are capped with a silane end-capping agent.

[0012] This invention innovatively synthesizes a branched MS resin with polyethylene oxide as the main chain and polymethyl vinyl propylene ether as the side chain through molecular design. The polymethyl vinyl propylene ether side chain exhibits excellent high-temperature resistance and hydrolysis resistance. At the same time, its large branched structure effectively hinders the thermal motion of the main chain molecules, increasing the glass transition temperature of the resin, thereby giving the final sealant excellent high-temperature resistance.

[0013] In some embodiments, the grafting rate of the graft copolymer is 80%–95%, and can be 81%, 82%, 83%, 84%, 85%, 86%, 87%, 88%, 89%, 90%, 91%, 92%, 93%, 94%, or 95%. A high grafting rate of over 80% can maximize the introduction of flexible branches, significantly improving the notched impact strength and toughness of the sealant, because a large number of branches can effectively absorb and dissipate external impact energy. If the grafting rate is below 80%, the number of branches is insufficient, which not only reduces the toughening effect, but also makes the material brittle at low temperatures, and also poses the risk of poor compatibility between the main and branch chains, easily leading to delamination or unstable mechanical properties. However, the grafting rate should not be too high either, as an excessively high grafting rate will cause too many branches to exacerbate molecular chain entanglement, resulting in excessively high system viscosity, affecting the flowability and operability during production and construction.

[0014] In some embodiments, the graft copolymer has an average degree of polymerization of 15–30, for example, 15, 16, 20, 25, 28, or 30. A degree of polymerization of 15–30 means that each side chain has a moderate length. This short, dense branched structure can act as an internal plasticizer, making the material uniform and compliant. If the degree of polymerization is too low (below 15), the branches are too short, insufficiently weakening the rigidity of the main chain, resulting in limited toughening effect; while if the degree of polymerization is too high (above 30), physical entanglement or even local crystallization can easily occur between long branches, leading to a surge in viscosity and processing difficulties. Simultaneously, the reduced mobility of long branches at low temperatures may actually decrease low-temperature compliance.

[0015] In some embodiments, the graft copolymer has a number-average molecular weight of 15,000–30,000 g / mol and a glass transition temperature (Tg) ≤ -60°C. Conventional MS resins are based on polypropylene ether (PPG) as the main chain, with a Tg typically between -50°C and -60°C; the resin of this invention has a Tg ≤ -60°C, achieving a significant reduction. The lower Tg brings two major performance improvements: firstly, excellent low-temperature performance, allowing the sealant to remain elastic rather than brittle in extremely cold environments such as -60°C, making it suitable for low-temperature conditions such as in frigid regions or cold storage facilities; secondly, better low modulus and high elastic recovery rate, with the molecular chains having greater mobility even at room temperature, enabling them to better follow the displacement of dynamic joints, especially suitable for applications with stringent requirements for displacement control, such as prefabricated buildings.

[0016] In some embodiments, the silane end-capping agent is a trialkoxysilane, wherein the alkyl group has 1-6 carbon atoms, preferably methyltrimethoxysilane.

[0017] In some embodiments, the MS sealant comprises the following components by weight: 100 parts of the branched MS resin; 15-25 parts of plasticizer; 2-3 parts of dehydrating agent; 2-3 parts of coupling agent; and 0.7-1 parts of catalyst.

[0018] In some embodiments, the MS sealant further includes inorganic fillers. The inorganic fillers are selected from, but are not limited to, nano-calcium carbonate, silica powder, and carbon black.

[0019] In some embodiments, the MS sealant further includes powdered fillers: 60-90 parts of nano-calcium carbonate and 2-8 parts of carbon black.

[0020] In some embodiments, the MS sealant may also include powdered filler selected from 60-90 parts of silica powder and 2-8 parts of carbon black.

[0021] There are no particular restrictions on the plasticizers, dehydrating agents, coupling agents, catalysts, and inorganic fillers mentioned above; those commonly used in MS adhesives can be used.

[0022] In some embodiments, the plasticizer is selected from polyether polyols, preferably polyether polyols with a viscosity of 2000 cp, by weight.

[0023] In some embodiments, the dehydrating agent is selected from trialkoxysilanes, wherein the alkyl group has 1-6 carbon atoms, preferably vinyltriethoxysilane.

[0024] In some embodiments, the coupling agent is selected from aminosilane coupling agents, preferably γ-aminopropyltriethoxysilane, by weight.

[0025] In some embodiments, the catalyst is selected from organotin catalysts, preferably dibutyltin dilaurate, by weight.

[0026] In some embodiments, the tensile strength of the MS sealant is ≥2.0 MPa, for example ≥3.0 MPa, and the elongation at break is ≥200%, for example ≥300%, as determined by using a type II dumbbell specimen at a tensile speed of 500 mm / min, in accordance with GB / T 528 standard.

[0027] In some embodiments, the MS sealant retains ≥80% of its tensile strength after aging at 120°C for 7 days and does not crack after aging at 120°C for 21 days.

[0028] A second aspect of the present invention provides a method for preparing the above-mentioned branched MS resin, comprising the following steps: (1) The modified polyethylene oxide was dissolved in an organic solvent and grafted copolymerized with methyl vinyl propyl ether monomer in the presence of an initiator to obtain polyethylene oxide-g-polymethyl vinyl propyl ether graft copolymer. (2) In the presence of a catalyst, the graft copolymer obtained in step (1) is subjected to a capping reaction with a silane capping agent.

[0029] In some embodiments, the method for preparing the above-mentioned branched MS resin further comprises: Step (1) Graft copolymerization reaction: The modified polyethylene oxide is dissolved in an organic solvent to prepare a solution with a mass fraction of 8% to 12%, and an inert gas is introduced to remove oxygen. Then, in the presence of an initiator, it is graft copolymerized with methyl vinyl propylene ether monomer to obtain PEO-g-PMVE graft copolymer. Step (2) End-capping reaction: After vacuum dehydration of the graft copolymer obtained in step (1), it is subjected to end-capping reaction with silane end-capping agent in the presence of catalyst to obtain the branched MS resin.

[0030] In some embodiments, in step (1), the modified polyethylene oxide is methacrylate-modified polyethylene oxide, wherein the molar ratio of polyethylene oxide monomer to methacrylate is 1:1.

[0031] In some embodiments, in step (1), the mass ratio of the polyethylene oxide to the methyl vinyl propylene ether monomer is 1:2 to 4, for example 1:3, preferably 1:2.

[0032] In some embodiments, in step (1), the initiator is a free radical initiator (non-redox initiator), preferably azobisisobutyronitrile (AIBN), and its amount is 0.5% to 2% of the total weight of polyethylene oxide and methyl vinyl propylene ether monomers; the organic solvent is a mixture of dimethylformamide (DMF) and tetrahydrofuran (THF). In some embodiments, the graft copolymerization reaction temperature is 60–80°C and the reaction time is 6–10 hours.

[0033] In some embodiments, in step (2), the silane end-capping agent is a trialkoxysilane, wherein the alkyl group has 1-6 carbon atoms, preferably methyltrimethoxysilane, and its amount is 1 to 1.5 times the molar amount of the graft copolymer obtained in step (1).

[0034] In some embodiments, in step (2), the catalyst is an organotin catalyst, preferably dibutyltin dilaurate, and its amount is 0.1wt% to 0.2wt% of the weight of the graft copolymer obtained in step (1).

[0035] In some embodiments, in step (2), the end-capping reaction temperature is 75-85°C and the reaction time is 6-8 hours; after step (1) is completed and before step (2) is performed, a step of vacuum dehydration treatment of the grafted copolymer is also included.

[0036] Experimental methods in this invention that do not specify specific conditions are generally performed under conventional conditions or as recommended by the manufacturer. Unless otherwise defined, all technical terms used in this invention have the same meaning as commonly understood by those skilled in the art.

[0037] Preparation Example 1: Preparation of Branched MS Resin 200g of methacrylate-modified polyethylene oxide (PEO number-average molecular weight approximately 20,000 g / mol) was dissolved in a blend of dimethylformamide and tetrahydrofuran, with a PEO monomer:methacrylate molar ratio of 1:1, to prepare a 10% (w / w) solution. The PEO solution was added to a reaction flask, and nitrogen gas was purged for 15 minutes to remove oxygen.

[0038] Add 400g of methyl vinyl propyl ether (MVE) monomer (PEO to MVE mass ratio = 1:2) to the reaction flask and stir until homogeneous. Weigh 4g of azobisisobutyronitrile (AIBN, initiator amount is 0.67 wt% of the total weight of PEO and MVE), dissolve it in a small amount of anhydrous ethanol and add it to the reaction flask.

[0039] With nitrogen gas continuously introduced, place the reaction flask in a constant temperature water bath and heat to 70°C. Stir the reaction for 8 hours under nitrogen protection. Take samples periodically during the reaction and monitor the grafting reaction progress using Fourier Transmission Infrared Spectroscopy (FTIR).

[0040] After the reaction was complete, the reaction flask was cooled to room temperature, and a small amount of hydroquinone was added to terminate the reaction. The reaction mixture was poured into excess methanol to precipitate the graft copolymer. The precipitate was collected by filtration and washed three times with methanol to remove unreacted monomers and homopolymers. The product was dried to constant weight in a vacuum oven at 50°C to obtain a polyethylene oxide-g-polymethyl vinyl propylene ether (PEO-g-PMVE) graft copolymer. 1 According to H NMR analysis, the grafting rate is about 90%, the average degree of polymerization of the branched chain is about 21, the number average molecular weight is about 20,000 g / mol, and the glass transition temperature (DSC measurement) is -66℃.

[0041] The dried PEO-g-PMVE graft copolymer was dehydrated under vacuum at 80°C for 2 hours to remove residual moisture, then dissolved in anhydrous toluene, and heated to 80°C under nitrogen protection. Methyltrimethoxysilane (MTMS) was added at 1.5 times the molar weight of the graft copolymer, followed by dropwise addition of dibutyltin dilaurate (DBTDL, 0.2 wt% of the graft copolymer weight), and the reaction was carried out at 80°C for 6–8 hours.

[0042] After the reaction was complete, the mixture was cooled to room temperature, and a small amount of acetic acid was added to neutralize the catalyst. The solvent and unreacted methyltrimethoxysilane were removed by vacuum distillation to obtain a branched MS resin (PEO-g-PMVE-Si), which is a silane-terminated polyethylene oxide-g-polymethylvinyl propylene ether graft copolymer, for later use.

[0043] Example 1: Preparation of High-Temperature Resistant MS Sealant (MS-1#) Take 200 g (about 100 parts by weight) of the branched MS resin prepared in Preparation Example 1, 50 g (about 25 parts by weight) of polyether polyol plasticizer (viscosity 2000 cp), 150 g (about 75 parts by weight) of nano calcium carbonate, and 5 g (about 2.5 parts by weight) of carbon black, add them to a 2 L planetary mixer, adjust the speed to 50 r / min, and stir for 30 min.

[0044] Under vacuum (≤-0.095 MPa) and nitrogen protection, add 4 g (approximately 2 parts by weight) of vinyltriethoxysilane (dehydrating agent) and 4 g (approximately 2 parts by weight) of γ-aminopropyltriethoxysilane (coupling agent), and stir for 10 min.

[0045] Under vacuum and nitrogen protection, 1.8 g (approximately 0.9 parts by weight) of dibutyltin dilaurate (catalyst) was added, stirred for 10 min, and discharged from the reactor to obtain high-temperature resistant MS sealant, which was designated as sample MS-1#.

[0046] Example 2: Preparation of high-temperature resistant MS sealant (MS-2#) Take 200 g (100 parts by weight) of the branched MS resin prepared in Preparation Example 1, 40 g (20 parts by weight) of polyether polyol plasticizer (viscosity 2000 cp), 180 g (90 parts by weight) of silica powder, and 16 g (8 parts by weight) of carbon black, add them to a 2 L planetary mixer, adjust the speed to 50 r / min, and stir for 30 min.

[0047] Under vacuum and nitrogen protection, add 6 g (3 parts by weight) of vinyltriethoxysilane (dehydrating agent) and 6 g (3 parts by weight) of γ-aminopropyltriethoxysilane (coupling agent), and stir for 10 min. Under vacuum and nitrogen protection, add 2 g (1 part by weight) of dibutyltin dilaurate (catalyst), stir for 10 min, and remove from the reactor, labeled MS-2#.

[0048] Comparative Example 1: Ordinary linear MS sealant (MS-3# comparison) MS sealant, designated MS-3#, was prepared using commercially available linear STP resin (number average molecular weight approximately 30,000 g / mol) as the main resin, following the same formulation and process as in Example 1.

[0049] Comparative Example 2: Ordinary linear MS sealant (MS-4# comparison) MS sealant, designated MS-4#, was prepared using commercially available linear STP resin (number average molecular weight approximately 30,000 g / mol) as the main resin, following the same formulation and process as in Example 2.

[0050] Performance testing The sealants prepared in Examples 1-2 and Comparative Examples 1-2 were subjected to performance tests according to the following methods: (1) Tensile strength and elongation at break: According to GB / T 528 standard, type II dumbbell specimens were used for testing at a tensile speed of 500 mm / min.

[0051] (2) High temperature resistance: The sample was placed in a 120℃ oven and aged for 1 day, 3 days, 7 days, 14 days and 21 days respectively. The condition of the sample was observed and the tensile strength after aging was tested. The tensile strength retention rate was calculated.

[0052] (3) Adhesion performance: According to DVS 1618 "Elastic thick film bonding of rail locomotives and vehicles", peel test specimens were prepared and the adhesion state of the sealant to specific profiles such as aluminum alloy, fiberglass, and glass under different conditions was tested according to the conditions in the table below, so as to determine the adhesion performance of the sealant.

[0053]

[0054] The test results are shown in Tables 1-3 below: Table 1. Initial tensile properties of sealants in Examples 1-2 and Comparative Examples 1-2 under standard experimental conditions.

[0055] Table 2. Performance test results of Examples 1-2 and Comparative Examples 1-2 after aging at 120℃ for different times. 120℃*1d

[0056] 120℃*3d

[0057] 120℃*7d

[0058] 120℃*14d

[0059] 120℃*21d

[0060] Table 3. Bonding performance test results of Examples 1-2

[0061] As shown in Tables 1-3, the sealant (MS-2#) prepared using the branched MS resin of this invention exhibits an initial tensile strength of 5.1 MPa and an elongation at break of 417%, demonstrating excellent comprehensive mechanical properties. In the 120℃ high-temperature aging test, MS-2# retained 81% of its tensile strength after 7 days of aging, 59% after 14 days, and showed no signs of cracking after 21 days. In contrast, the control samples (MS-3# and MS-4#) using ordinary linear STP resin completely cracked after 7 days of aging, making further testing impossible. This clearly demonstrates that by introducing polymethyl vinyl propylene ether branches to modify the MS resin, this invention fundamentally improves the long-term high-temperature resistance of the sealant, extending its temperature resistance by more than three times compared to ordinary MS sealants.

[0062] As shown in Table 3, the sealant prepared using the branched MS resin of this invention exhibits good adhesive performance. The branched resin structure does not affect the adhesive function of the sealant and meets the adhesive requirements of the DVS 1618 standard in the rail transit field.

[0063] The present application has been described above with reference to preferred embodiments; however, these embodiments are merely exemplary and illustrative. Various substitutions and modifications can be made to the present application based on these embodiments, all of which fall within the protection scope of the present application.

Claims

1. An MS sealant, characterized in that, The MS sealant comprises a branched MS resin, which is a graft copolymer with polyethylene oxide as the main chain and polymethyl vinyl propylene ether as the branch chain, and the ends of the graft copolymer are capped with a silane end-capping agent.

2. The MS sealant according to claim 1, characterized in that, The graft copolymer has a grafting rate of 80% to 95% and an average degree of polymerization of the branched chains of 15 to 30.

3. The MS sealant according to claim 1, characterized in that, The number-average molecular weight of the graft copolymer is 15,000 to 30,000 g / mol, and the glass transition temperature is ≤ -60℃.

4. The MS sealant according to claim 1, characterized in that, The silane end-capping agent is a trialkoxysilane, wherein the alkyl group has 1-6 carbon atoms, preferably methyltrimethoxysilane.

5. The MS sealant according to claim 1, characterized in that, By weight, it contains the following components: 100 parts of the branched MS resin; Plasticizer 15-25 parts; 2-3 parts of dehydrating agent; 2-3 parts coupling agent; Catalyst 0.7 to 1 part.

6. The MS sealant according to claim 5, characterized in that, By weight, The plasticizer is selected from polyether polyols, preferably polyether polyols with a viscosity value of 2000 cp; The dehydrating agent is selected from trialkoxysilane, wherein the alkyl group has 1-6 carbon atoms, preferably vinyltriethoxysilane; The coupling agent is selected from aminosilane coupling agents, preferably γ-aminopropyltriethoxysilane; The catalyst is selected from organotin catalysts, preferably dibutyltin dilaurate.

7. The MS sealant according to claim 5, characterized in that, The MS sealant retains ≥80% of its tensile strength after aging at 120℃ for 7 days and does not crack after aging at 120℃ for 21 days.

8. A method for preparing a branched MS resin for MS sealant, characterized in that, Includes the following steps: (1) The modified polyethylene oxide was dissolved in an organic solvent and grafted copolymerized with methyl vinyl propyl ether monomer in the presence of an initiator to obtain polyethylene oxide-g-polymethyl vinyl propyl ether graft copolymer. (2) In the presence of a catalyst, the graft copolymer obtained in step (1) is subjected to a capping reaction with a silane capping agent.

9. The method according to claim 8, characterized in that, In step (1), the modified polyethylene oxide is methacrylate-modified polyethylene oxide, wherein the molar ratio of polyethylene oxide monomer to methacrylate is 1:

1.

10. The method according to claim 8, characterized in that, In step (1), the mass ratio of the polyethylene oxide to the methyl vinyl propylene ether monomer is 1:2 to 4, preferably 1:

2.

11. The method according to claim 8, characterized in that, In step (1), the initiator is a non-redox initiator, preferably azobisisobutyronitrile, and its amount is 0.5% to 2% of the total weight of polyethylene oxide and methyl vinyl propylene ether monomer; the organic solvent is a mixed solvent of dimethylformamide and tetrahydrofuran.

12. The method according to claim 8, characterized in that, The reaction temperature in step (1) is 60~80℃ and the reaction time is 6~10 hours.

13. The method according to claim 8, characterized in that, In step (2), the silane end-capping agent is a trialkoxysilane, wherein the alkyl group has 1-6 carbon atoms, preferably methyltrimethoxysilane, and its amount is 1 to 1.5 times the molar amount of the graft copolymer obtained in step (1).

14. The method according to claim 8, characterized in that, In step (2), the catalyst is an organotin catalyst, preferably dibutyltin dilaurate, and its amount is 0.1wt% to 0.2wt% of the weight of the graft copolymer obtained in step (1).

15. The method according to claim 8, characterized in that, In step (2), the end-capping reaction temperature is 75-85°C and the reaction time is 6-8 hours; after step (1) is completed and before step (2) is performed, the step of vacuum dehydration treatment of the graft copolymer is also included.

Images