A cold-resistant polyether-type polyurethane sealing material and its preparation method

Abstract

This invention provides an extremely cold-resistant polyether-based polyurethane sealing material and its preparation method, belonging to the technical field of polyurethane sealing materials. The sealing material is prepared from PMEG-type polyether polyol, isocyanate component, chain extender, crosslinking agent, interface-modified low-temperature resistant component, catalyst, and antioxidant. The NCO / OH reaction index of the polyurethane elastomer is 0.95–1.12, and the mass fraction of isocyanate groups in the prepolymer is 3.5%–8.5%. In preparation, the PMEG-type polyether polyol is vacuum dehydrated and reacted with the isocyanate component to form a prepolymer. Then, the interface-modified low-temperature resistant component is added for dispersion, followed by the addition of the chain extender, crosslinking agent, catalyst, and antioxidant. The mixture is then mixed, degassed, cured, and post-cured to obtain the sealing material. This invention improves the problem of elasticity loss, brittleness, and fracture of polyurethane sealing materials in environments ranging from -50°C to -60°C by synergistically controlling the soft segment structure, interface-modified component, and crosslinking density.

Description

Technical Field

[0001] This invention relates to the field of polyurethane sealing materials technology, and in particular to an extremely cold-resistant polyether-type polyurethane sealing material and its preparation method. Background Technology

[0002] Polyurethane elastomers possess wear resistance, elastic recovery, and processability, and are commonly used in sealing products such as sealing rings, gaskets, oil seals, dust rings, and hydraulic seals. For hydraulic equipment, engineering equipment, outdoor machinery, and equipment operating in cryogenic conditions in extremely cold northern regions, seals not only need to withstand conventional compression, friction, and media contact, but also need to maintain elastic recovery capability in extremely low-temperature environments to maintain the contact pressure between the seal and mating parts.

[0003] Most existing polyurethane sealing materials use general-purpose polyurethane systems. Low-end systems typically use polyurethane materials formed from TDI and polyether polyols, while mid-to-high-end systems typically use polyurethane materials formed from MDI and polyether polyols. These materials can maintain a certain level of usability at around -45°C, but when the ambient temperature drops to -50°C to -60°C, the movement of soft segments in the polyurethane material is significantly restricted. The hydrogen bonding between hard segments and the local intermolecular forces have a greater impact on the material's rigidity, making the material prone to decreased elasticity, brittleness, crack propagation, and even fracture.

[0004] For seals, after the material loses its elasticity at low temperatures, the sealing lip or sealing contact surface can no longer maintain a proper fit with the mating parts; after the material becomes brittle, leakage channels can easily form at the sealing interface. Therefore, existing general-purpose polyurethane sealing materials cannot maintain stable sealing performance for long periods under extremely cold conditions of -50℃ to -60℃, limiting their application in hydraulic seals and engineering equipment seals in extremely cold regions. To address this, a cold-resistant polyether-based polyurethane sealing material and its preparation method are proposed. Summary of the Invention

[0005] In view of this, the present invention provides an extremely cold-resistant polyether-type polyurethane sealing material and a preparation method thereof, in order to solve or alleviate the technical problems existing in the prior art, and at least provide a beneficial alternative.

[0006] The technical solution of this invention is achieved as follows: A cold-resistant polyether-type polyurethane sealing material, comprising a polyurethane elastomer formed by the reaction of a polyether polyol component, an isocyanate component, and a curing component, wherein the polyether polyol component includes a PMEG-type polyether polyol, the curing component includes a chain extender and a crosslinking agent, and the polyurethane elastomer contains an interface-modified low-temperature resistant component; by weight, the polyurethane elastomer is prepared from the following raw materials: 100 parts of PMEG-type polyether polyol, 25-60 parts of isocyanate component, 3-15 parts of chain extender, 0.3-5 parts of crosslinking agent, 1-15 parts of interface-modified low-temperature resistant component, 0.01-0.3 parts of catalyst, and 0.2-2 parts of antioxidant; wherein the NCO / OH reaction index of the polyurethane elastomer is 0.95-1.12, and the mass fraction of isocyanate groups in the prepolymer formed by the reaction of the PMEG-type polyether polyol and the isocyanate component is 3.5%-8.5%.

[0007] The PMEG-type polyether polyol has a number average molecular weight of 1000-3000, a water content of no more than 0.03 wt%, and a mass percentage of no less than 70% in the polyether polyol component. By using PMEG-type polyether polyol as the main source of soft segments and controlling its molecular weight and water content, the polyurethane soft segments retain the basis for chain segment mobility even in extremely cold environments, reducing the risk of elasticity loss caused by restricted soft segment movement at low temperatures.

[0008] The isocyanate component is selected from at least one of diphenylmethane diisocyanate, liquefied diphenylmethane diisocyanate, isophorone diisocyanate, and hydrogenated diphenylmethane diisocyanate. By selecting the above isocyanate component, a polyurethane prepolymer suitable for use in sealing materials can be formed with PMEG-type polyether polyols, and a reaction basis can be provided for subsequent chain extension and crosslinking reactions.

[0009] The interface-modified low-temperature resistant component is obtained by treating low-temperature resistant matrix particles with an interface modifier. The low-temperature resistant matrix particles are selected from at least one of nano-silica, silicone rubber micropowder, and polytetrafluoroethylene micropowder. The interface modifier is selected from at least one of silane coupling agents, hydroxyl-containing polyether modifiers, and polyether-modified siloxanes. The average particle size of the interface-modified low-temperature resistant component is 20 nm to 20 μm, and the mass ratio of the low-temperature resistant matrix particles to the interface modifier is 100:(1 to 12). By modifying the interface of the low-temperature resistant matrix particles, their dispersion state and interfacial compatibility in polyurethane elastomers can be improved, low-temperature stress concentration caused by particle agglomeration can be reduced, and local intermolecular forces in the polyurethane system can be adjusted.

[0010] The chain extender is selected from at least one of 1,4-butanediol, ethylene glycol, diethylene glycol, and hydroquinone dihydroxyethyl ether; the crosslinking agent is selected from at least one of trimethylolpropane, glycerol, and triisopropanolamine. By using the chain extender and crosslinking agent in combination, and by controlling the NCO / OH reaction index and the mass fraction of isocyanate groups in the prepolymer, a moderately crosslinked network is formed in the polyurethane elastomer. This avoids low-temperature embrittlement caused by excessive crosslinking density, and also avoids a decrease in material strength and dimensional stability caused by insufficient crosslinking density.

[0011] The catalyst is selected from at least one of organobismuth catalysts, organozinc catalysts, and tertiary amine catalysts; the antioxidant is selected from at least one of hindered phenolic antioxidants and phosphite antioxidants. The reaction is regulated by the catalyst, and the risk of oxidative aging of the material during processing and use is reduced by the antioxidant.

[0012] The extremely cold-resistant polyether-type polyurethane sealing material is used to prepare sealing rings, gaskets, oil seals, dust rings, or hydraulic seals.

[0013] This invention also provides a method for preparing an extremely cold-resistant polyether-type polyurethane sealing material, comprising the following steps: S1. The PMEG type polyether polyol is vacuum dehydrated to obtain the dehydrated polyether polyol. S2. Under nitrogen protection, the dehydrated polyether polyol is mixed and reacted with the isocyanate component to obtain a prepolymer with an isocyanate group mass fraction of 3.5% to 8.5%. S3. Add the interface-modified low-temperature resistant component to the prepolymer and disperse it, so that the interface-modified low-temperature resistant component is dispersed in the prepolymer; S4. Add chain extender, crosslinking agent, catalyst and antioxidant to the system obtained in step S3, mix and then perform vacuum degassing to obtain the mixture to be shaped. S5. The mixture to be formed is injected into the mold and cured, and then post-curing treatment is performed to obtain an extremely cold-resistant polyether polyurethane sealing material.

[0014] In the preparation method, in step S1, the vacuum dehydration temperature is 100-120℃, the vacuum gauge pressure is -0.08MPa to -0.10MPa, and the dehydration time is 1-3h; in step S2, the reaction temperature is 70-85℃, and the reaction time is 1.5-3h; in step S3, the dispersion method is at least one of mechanical stirring dispersion and ultrasonic dispersion; in step S5, the curing temperature is 80-110℃, the curing time is 4-16h, the post-curing temperature is 80-110℃, and the post-curing time is 6-24h.

[0015] The embodiments of the present invention have the following advantages due to the adoption of the above technical solutions: I. This invention uses PMEG-type polyether polyol as the main source of soft segments and controls the mass fraction of isocyanate groups in the prepolymer to give the polyurethane elastomer a soft segment structure suitable for extremely cold sealing conditions, thereby improving the problem of easy loss of elasticity of existing general-purpose polyurethane materials at -50℃ to -60℃.

[0016] Second, this invention introduces an interface-modified low-temperature resistant component into a polyurethane elastomer. Through interface modification, the compatibility between the low-temperature resistant matrix particles and the polyurethane matrix is ​​improved, reducing the risk of crack propagation caused by particle agglomeration or local stress concentration at low temperatures.

[0017] Third, this invention controls the crosslinking density by using chain extenders, crosslinking agents, NCO / OH reaction index, and the mass fraction of prepolymer isocyanate groups, so that the material can maintain the mechanical support required for the seal while reducing the tendency to become embrittled in extremely cold environments.

[0018] IV. The preparation method of this invention forms a continuous process through vacuum dehydration, prepolymerization reaction, dispersion of interface-modified components, chain extension and crosslinking, defoaming and curing, and post-curing treatment. This is beneficial for the dispersion of interface-modified low-temperature resistant components in the polyurethane system and the formation of the polyurethane elastomer crosslinking network, and is suitable for the preparation of extremely cold-resistant polyurethane sealing materials.

[0019] The above overview is for illustrative purposes only and is not intended to be limiting in any way. In addition to the illustrative aspects, embodiments, and features described above, further aspects, embodiments, and features of the invention will become readily apparent from the accompanying drawings and the following detailed description. Attached Figure Description

[0020] To more clearly illustrate the technical solutions in the embodiments of this application or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0021] Figure 1 This is a flowchart illustrating the preparation process of the extremely cold-resistant polyether-type polyurethane sealing material of the present invention. Detailed Implementation

[0022] In the following description, only certain exemplary embodiments are briefly described. As those skilled in the art will recognize, the described embodiments can be modified in various ways without departing from the spirit or scope of the invention. Therefore, the drawings and description are considered to be exemplary in nature and not restrictive.

[0023] The embodiments of the present invention will now be described in detail with reference to the accompanying drawings.

[0024] This invention provides an extremely cold-resistant polyether-type polyurethane sealing material, which is prepared by prepolymerization, dispersion, chain extension and crosslinking, curing, and post-curing treatment of PMEG-type polyether polyol, isocyanate component, chain extender, crosslinking agent, interface-modified low-temperature resistant component, catalyst, and antioxidant. The PMEG-type polyether polyol serves as the main source of soft segments in the polyurethane elastomer; the interface-modified low-temperature resistant component is dispersed in the polyurethane elastomer to improve the interfacial compatibility between the low-temperature resistant matrix particles and the polyurethane matrix; and the chain extender and crosslinking agent are used to adjust the hard segment structure and crosslinking density of the polyurethane elastomer.

[0025] In this invention, the NCO / OH reaction index refers to the ratio of the molar number of isocyanate groups to the molar number of hydroxyl groups in the system. By controlling the NCO / OH reaction index to 0.95–1.12 and controlling the mass fraction of isocyanate groups in the prepolymer to 3.5%–8.5%, the polyurethane elastomer forms a cross-linked network suitable for use as a sealing material, reducing low-temperature embrittlement caused by excessive cross-linking density and insufficient mechanical support caused by insufficient cross-linking density.

[0026] The PMEG-type polyether polyol in this invention has a number-average molecular weight of 1000-3000, a water content of no more than 0.03 wt%, and a mass percentage of PMEG-type polyether polyol in the polyether polyol component of no less than 70%. The isocyanate component can be selected from at least one of diphenylmethane diisocyanate, liquefied diphenylmethane diisocyanate, isophorone diisocyanate, and hydrogenated diphenylmethane diisocyanate. The chain extender can be selected from at least one of 1,4-butanediol, ethylene glycol, diethylene glycol, and hydroquinone dihydroxyethyl ether. The crosslinking agent can be selected from at least one of trimethylolpropane, glycerol, and triisopropanolamine. The catalyst can be selected from at least one of organobismuth catalysts, organozinc catalysts, and tertiary amine catalysts. The antioxidant can be selected from at least one of hindered phenolic antioxidants and phosphite antioxidants.

[0027] This embodiment provides an interface-modified low-temperature resistant component, which is obtained by treating low-temperature resistant matrix particles with an interface modifier.

[0028] Nano-silica and silicone rubber powder were mixed at a mass ratio of 1:2 to obtain low-temperature resistant matrix particles. These particles were then dried at 100°C for 2 hours to reduce the water content adsorbed on the particle surface. The dried particles were then added to a mixing apparatus along with a silane coupling agent and a polyether-modified siloxane as interface modifiers, with a mass ratio of low-temperature resistant matrix particles to interface modifiers of 100:6. The system was stirred at 60°C for 1.5 hours to allow the interface modifiers to contact the surface of the low-temperature resistant matrix particles and form a modified interface. After treatment, the resulting material was dried, ground, and sieved to obtain the interface-modified low-temperature resistant component.

[0029] The average particle size of the obtained interface-modified low-temperature resistant component is 0.5–10 μm. When used for subsequent polyurethane prepolymer dispersion, this component can reduce the agglomeration of low-temperature resistant matrix particles in the polyurethane system and reduce local stress concentration caused by filler agglomeration at low temperatures.

[0030] In other embodiments, the low-temperature resistant matrix particles may also be at least one of nano-silica, silicone rubber micro powder, and polytetrafluoroethylene micro powder; the interface modifier may also be at least one of silane coupling agent, hydroxyl-containing polyether modifier, and polyether-modified siloxane; the average particle size of the interface-modified low-temperature resistant component may be controlled to be 20 nm to 20 μm.

[0031] like Figure 1 As shown, the extremely cold-resistant polyether-type polyurethane sealing material of the present invention is prepared by the following method: S1. Add PMEG type polyether polyol to a reaction vessel and dehydrate it under vacuum for 1 to 3 hours at 100 to 120°C and a vacuum gauge pressure of -0.08 MPa to -0.10 MPa to obtain dehydrated PMEG type polyether polyol.

[0032] S2. Adjust the temperature of the reactor to 70-85℃, and under nitrogen protection, mix and react the dehydrated PMEG type polyether polyol with the isocyanate component for 1.5-3 hours to obtain the prepolymer; wherein the mass fraction of isocyanate groups in the prepolymer is controlled to be 3.5%-8.5%.

[0033] S3. Add the interface-modified low-temperature resistant component to the prepolymer and disperse it by at least one of mechanical stirring and ultrasonic dispersion to disperse the interface-modified low-temperature resistant component in the prepolymer.

[0034] S4. Add chain extender, crosslinking agent, catalyst and antioxidant to the system obtained in step S3, mix evenly and then perform vacuum degassing to obtain the mixture to be shaped; wherein, the NCO / OH reaction index is controlled to be 0.95 to 1.12.

[0035] S5. Inject the mixture to be molded into the preheated mold and cure it at 80-110℃ for 4-16 hours. After demolding, it is post-cured at 80-110℃ for 6-24 hours to obtain an extremely cold-resistant polyether polyurethane sealing material.

[0036] Through the above preparation process, a prepolymer containing a certain amount of isocyanate groups is first formed, and then the interface-modified low-temperature resistant component is dispersed in the prepolymer. Subsequently, chain extension, crosslinking and curing are carried out, which is beneficial to the distribution of the interface-modified low-temperature resistant component in the polyurethane system and to the formation of a polyurethane elastomer network suitable for extremely cold sealing conditions. Example

[0037] This embodiment provides an extremely cold-resistant polyether-type polyurethane sealing material, the raw materials of which, by weight, include: 100 parts PMEG type polyether polyol, 38 parts liquefied diphenylmethane diisocyanate, 7 parts 1,4-butanediol, 1.2 parts trimethylolpropane, 6 parts interface-modified low-temperature resistant component, 0.05 parts organic bismuth catalyst and 0.5 parts hindered phenolic antioxidant.

[0038] The PMEG-type polyether polyol has a number average molecular weight of 2000 and a water content of no more than 0.03 wt%. The interface-modified low-temperature resistant component is the interface-modified low-temperature resistant component obtained in the above preparation example.

[0039] The preparation method of this embodiment includes the following steps: S1. Add PMEG type polyether polyol to the reactor and dehydrate it for 2 hours at 110℃ and vacuum gauge pressure -0.09MPa to obtain dehydrated PMEG type polyether polyol.

[0040] S2. Adjust the reactor temperature to 75℃, add liquefied diphenylmethane diisocyanate under nitrogen protection, and maintain the reaction temperature for 2 hours to obtain the prepolymer. The mass fraction of isocyanate groups in the prepolymer was measured to be 5.6%.

[0041] S3. Add the interface-modified low-temperature resistant component to the prepolymer, mechanically stir at 70°C for 30 min, and then ultrasonically disperse for 15 min to disperse the interface-modified low-temperature resistant component in the prepolymer.

[0042] S4. Add 1,4-butanediol, trimethylolpropane, organic bismuth catalyst and hindered phenolic antioxidant to the system obtained in step S3, stir evenly and then perform vacuum degassing to obtain the mixture to be formed; wherein, the NCO / OH reaction index is controlled to be 1.03.

[0043] S5. Inject the mixture to be formed into a sealing mold preheated to 90°C, cure at 90°C for 10 hours, and after demolding, cure at 100°C for 12 hours to obtain an extremely cold-resistant polyether polyurethane sealing material. Example

[0044] This embodiment provides an extremely cold-resistant polyether-type polyurethane sealing material, the raw materials of which, by weight, include: The composition includes 100 parts PMEG-type polyether polyol, 42 parts compound isocyanate component, 6 parts 1,4-butanediol, 0.8 parts glycerol, 8 parts interface-modified low-temperature resistant component, 0.08 parts organic zinc catalyst, 0.4 parts hindered phenolic antioxidant and 0.3 parts phosphite antioxidant.

[0045] The compound isocyanate component is obtained by mixing diphenylmethane diisocyanate and hydrogenated diphenylmethane diisocyanate at a mass ratio of 3:1. The interface-modified low-temperature resistant component is obtained by treating silicone rubber micropowder and polytetrafluoroethylene micropowder with a hydroxyl-containing polyether modifier. The mass ratio of silicone rubber micropowder to polytetrafluoroethylene micropowder is 2:1, and the mass ratio of low-temperature resistant matrix particles to hydroxyl-containing polyether modifier is 100:8.

[0046] The preparation method of this embodiment includes the following steps: S1. Add PMEG type polyether polyol to the reactor and dehydrate it for 2 hours at 115℃ and vacuum gauge pressure -0.09MPa to obtain dehydrated PMEG type polyether polyol.

[0047] S2. Adjust the reactor temperature to 80℃, add the compound isocyanate component under nitrogen protection, and maintain the reaction temperature for 2.5h to obtain the prepolymer. The mass fraction of isocyanate groups in the prepolymer was measured to be 6.1%.

[0048] S3. Add the interface-modified low-temperature resistant component to the prepolymer and mechanically stir at 75°C for 40 minutes to disperse the interface-modified low-temperature resistant component in the prepolymer.

[0049] S4. Add 1,4-butanediol, glycerol, organozinc catalyst, hindered phenolic antioxidant and phosphite antioxidant to the system obtained in step S3, stir evenly and then perform vacuum degassing to obtain the mixture to be shaped; wherein, the NCO / OH reaction index is controlled to be 1.05.

[0050] S5. Inject the mixture to be formed into a sealing mold preheated to 100°C, cure at 100°C for 8 hours, and after demolding, cure at 100°C for 10 hours to obtain an extremely cold-resistant polyether polyurethane sealing material. Example

[0051] This embodiment provides an extremely cold-resistant polyether-type polyurethane sealing material, the raw materials of which, by weight, include: 100 parts PMEG type polyether polyol, 35 parts liquefied diphenylmethane diisocyanate, 5 parts diethylene glycol, 0.6 parts trimethylolpropane, 4 parts interface-modified low-temperature resistant component, 0.04 parts tertiary amine catalyst, 0.03 parts organic bismuth catalyst and 0.6 parts hindered phenolic antioxidant.

[0052] The interface-modified low-temperature resistant component is obtained by treating nano-silica with a silane coupling agent and a polyether-modified siloxane, with a mass ratio of nano-silica to modifier of 100:5.

[0053] The preparation method of this embodiment includes the following steps: S1. Add PMEG type polyether polyol to the reactor and dehydrate it for 3 hours at 105℃ and vacuum gauge pressure -0.08MPa to obtain dehydrated PMEG type polyether polyol.

[0054] S2. Adjust the reactor temperature to 72℃, add liquefied diphenylmethane diisocyanate under nitrogen protection, and maintain the reaction temperature for 2 hours to obtain the prepolymer. The mass fraction of isocyanate groups in the prepolymer was measured to be 4.8%.

[0055] S3. Add the interface-modified low-temperature resistant component to the prepolymer, mechanically stir at 70°C for 30 min, and then ultrasonically disperse for 10 min to disperse the interface-modified low-temperature resistant component in the prepolymer.

[0056] S4. Diethylene glycol, trimethylolpropane, tertiary amine catalyst, organobismuth catalyst and hindered phenolic antioxidant are added to the system obtained in step S3. After stirring evenly, vacuum degassing is performed to obtain the mixture to be shaped. The NCO / OH reaction index is controlled to be 0.98.

[0057] S5. Inject the mixture to be formed into a sealing mold preheated to 85°C, cure at 85°C for 12 hours, and after demolding, cure at 90°C for 16 hours to obtain an extremely cold-resistant polyether polyurethane sealing material.

[0058] Comparative Example 1 This comparative example uses a general MDI + polyether system to prepare polyurethane sealing materials. By weight, the raw materials include: The composition includes 100 parts of ordinary polyether polyol, 40 parts of diphenylmethane diisocyanate, 8 parts of 1,4-butanediol, 0.05 parts of organic bismuth catalyst, and 0.5 parts of hindered phenolic antioxidant.

[0059] This comparative example does not use PMEG-type polyether polyols as the main soft segment source, does not add interface-modified low-temperature resistant components, and does not synergistically control the mass fraction of prepolymer isocyanate groups and the NCO / OH reaction index as defined in this invention.

[0060] In the preparation process, ordinary polyether polyol is dehydrated and then prepolymerized with diphenylmethane diisocyanate. Then, 1,4-butanediol, organic bismuth catalyst and hindered phenolic antioxidant are added. After degassing, curing and post-curing treatment, the polyurethane sealing material of Comparative Example 1 is obtained.

[0061] Comparative Example 2 This comparative example uses PMEG-type polyether polyol to prepare polyurethane sealing material. By mass, the raw materials include: 100 parts PMEG type polyether polyol, 38 parts liquefied diphenylmethane diisocyanate, 7 parts 1,4-butanediol, 1.2 parts trimethylolpropane, 0.05 parts organic bismuth catalyst and 0.5 parts hindered phenolic antioxidant.

[0062] The difference between this comparative example and Example 1 is that no interface-modified low-temperature resistant component is added.

[0063] During preparation, the polyurethane sealing material of Comparative Example 2 was obtained by prepolymerization, chain extension crosslinking, degassing, curing and post-curing treatment according to the preparation conditions of Example 1.

[0064] Test Example 1: Tensile Properties Test at -60℃ Standard tensile specimens were prepared from the materials obtained in Examples 1-3 and Comparative Examples 1-2, respectively. Before testing, each specimen was placed in a -60°C environment for 4 hours, and then tensile properties were tested under low temperature conditions or immediately after removal. The tensile strength and elongation at break were recorded. Five specimens were tested for each group of samples, and the average value was taken.

[0065] The test results are shown in Table 1.

[0066] Table 1. Results of tensile properties at -60℃ Comparative Example 1 22.4 185 The fracture surface is relatively clean, with some areas showing whitening. Comparative Example 2 25.1 218 The fracture surface is partially white. Example 1 27.0 241 The fracture surface is relatively uniform. Example 2 27.6 246 The fracture surface is relatively uniform. Example 3 26.8 239 The fracture surface is relatively uniform. As shown in Table 1, compared with Comparative Example 1, the tensile strength and elongation at break of Examples 1-3 were all improved at -60℃. Comparative Example 2, using PMEG-type polyether polyol, showed improvement compared to Comparative Example 1, but since it did not include interface-modified low-temperature resistant components, its low-temperature elongation at break was still lower than that of Examples 1-3. This indicates that the combined effect of PMEG-type polyether polyol, interface-modified low-temperature resistant components, and crosslinking density control is beneficial for improving the low-temperature toughness of polyurethane sealing materials at -60℃.

[0067] Test Example 2: Observation of bending and impact at -60℃ The materials obtained in Examples 1-3 and Comparative Examples 1-2 were cut into specimens of the same size. After the specimens were kept in an environment of -60°C for 4 hours, they were observed by bending at 180° and then by low-temperature impact after the same low-temperature treatment. The surface cracks, fractures and elasticity loss of the specimens were recorded.

[0068] The test results are shown in Table 2.

[0069] Table 2. Results of bending and impact tests at -60℃ Comparative Example 1 Obvious cracks appeared Local fracture Slow recovery, with potential for bullet loss. Comparative Example 2 Fine cracks appeared Incompletely broken, surface is whitish Slow recovery Example 1 No obvious cracks were observed. No obvious fracture was observed. It can be restored to near its original state. Example 2 No obvious cracks were observed. No obvious fracture was observed. It can be restored to a state close to its original state. Example 3 No obvious cracks were observed. No obvious fracture was observed. It can be restored to near its original state. As shown in Table 2, Comparative Example 1 developed cracks or localized fractures after bending and impact at -60℃, indicating that the general-purpose MDI+polyether system is prone to embrittlement under extremely cold conditions. Comparative Example 2, due to the use of PMEG-type polyether polyol, showed some reduction in low-temperature embrittlement, but fine cracks still appeared. Examples 1-3 showed no obvious cracks or fractures under the same low-temperature treatment conditions, indicating that the addition of interface-modified low-temperature resistant components and control of crosslinking density are beneficial in reducing the risk of low-temperature embrittlement of the material.

[0070] Test Example 3: Low-Temperature Compression Permanent Deformation Test The materials obtained in Examples 1-3 and Comparative Examples 1-2 were used to prepare compression set specimens. The specimens were compressed by 25% and kept at -40°C for 24 hours. Then, the compression was released and the specimens were allowed to recover at room temperature for 30 minutes. The compression set rate was then measured.

[0071] The test results are as follows: The low-temperature compression set rate of Comparative Example 1 was 42.5%; the low-temperature compression set rate of Comparative Example 2 was 35.8%; the low-temperature compression set rate of Example 1 was 28.6%; the low-temperature compression set rate of Example 2 was 27.9%; and the low-temperature compression set rate of Example 3 was 29.3%.

[0072] The above results indicate that, compared with Comparative Examples 1 and 2, Examples 1-3 exhibit lower compression set after low-temperature compression. For sealing materials, a lower low-temperature compression set is beneficial for maintaining sealing contact pressure after low-temperature compression, thereby mitigating the problem of reduced sealing performance caused by elasticity loss under extremely cold conditions.

[0073] As can be seen from Test Examples 1 to 3, Comparative Example 1, which uses a general polyether and MDI system, exhibits low low-temperature elongation at break, bending cracking, and impact fracture at -60℃, which is consistent with the problem of existing general polyurethane sealing materials easily losing elasticity and becoming brittle under extremely cold conditions.

[0074] Comparative Example 2, using PMEG-type polyether polyol, showed improved low-temperature tensile properties and resistance to cracking compared to Comparative Example 1, indicating that PMEG-type polyether polyol, as the main source of soft segments, can provide a basis for low-temperature segment activity. However, Comparative Example 2, without the addition of interface-modified low-temperature resistant components, still exhibited fine cracks after low-temperature bending, indicating that simply using PMEG-type polyether polyol is insufficient to adequately improve the problems of localized stress concentration and crack propagation at low temperatures.

[0075] Examples 1-3 involve adding interface-modified low-temperature resistant components to PMEG-type polyether polyols and controlling the mass fraction of isocyanate groups and the NCO / OH reaction index in the prepolymer to create a synergistic relationship between the soft segment structure, interfacial dispersion state, and crosslinking density of the polyurethane elastomer. As a result, the material maintains a high elongation at break at -60°C, shows no obvious cracks or fractures after low-temperature bending and impact, and exhibits a low low-temperature compression set.

[0076] Therefore, the extreme cold-resistant polyether-type polyurethane sealing material provided in this embodiment of the invention can improve the problems of existing general-purpose polyurethane sealing materials being prone to loss of elasticity, brittleness and breakage in extremely cold environments of -50℃ to -60℃, and is suitable for the preparation of sealing rings, gaskets, oil seals, dust rings or hydraulic seals.

[0077] The above description is merely a specific embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any person skilled in the art can easily conceive of various variations or substitutions within the technical scope disclosed in the present invention, and these should all be included within the scope of protection of the present invention. Therefore, the scope of protection of the present invention should be determined by the scope of the claims.

Claims

1. A cold-resistant polyether-type polyurethane sealing material, comprising a polyurethane elastomer formed by reacting a polyether polyol component, an isocyanate component, and a curing component, characterized in that, The polyether polyol component includes PMEG type polyether polyol, the curing component includes chain extender and crosslinking agent, and the polyurethane elastomer contains an interface-modified low-temperature resistant component. The polyurethane elastomer, by weight, is prepared from the following raw materials: 100 parts of PMEG-type polyether polyol, 25-60 parts of isocyanate component, 3-15 parts of chain extender, 0.3-5 parts of crosslinking agent, 1-15 parts of interface-modified low-temperature resistant component, 0.01-0.3 parts of catalyst, and 0.2-2 parts of antioxidant; wherein, the NCO / OH reaction index of the polyurethane elastomer is 0.95-1.12, and the mass fraction of isocyanate groups in the prepolymer formed by the reaction of the PMEG-type polyether polyol and the isocyanate component is 3.5%-8.5%.

2. The extremely cold-resistant polyether-type polyurethane sealing material according to claim 1, characterized in that, The PMEG type polyether polyol has a number average molecular weight of 1000-3000, a water content of no more than 0.03wt%, and the mass percentage of the PMEG type polyether polyol in the polyether polyol component is no less than 70%.

3. The extremely cold-resistant polyether-type polyurethane sealing material according to claim 1, characterized in that, The isocyanate component is selected from at least one of diphenylmethane diisocyanate, liquefied diphenylmethane diisocyanate, isophorone diisocyanate, and hydrogenated diphenylmethane diisocyanate.

4. The extremely cold-resistant polyether-type polyurethane sealing material according to claim 1, characterized in that, The interface-modified low-temperature resistant component is obtained by treating low-temperature resistant matrix particles with an interface modifier. The low-temperature resistant matrix particles are selected from at least one of nano-silica, silicone rubber micro powder, and polytetrafluoroethylene micro powder. The interface modifier is selected from at least one of silane coupling agent, hydroxyl-containing polyether modifier, and polyether-modified siloxane.

5. The extremely cold-resistant polyether-type polyurethane sealing material according to claim 4, characterized in that, The average particle size of the interface-modified low-temperature resistant component is 20 nm to 20 μm, and the mass ratio of the low-temperature resistant matrix particles to the interface modifier is 100:(1 to 12).

6. The extremely cold-resistant polyether-type polyurethane sealing material according to claim 1, characterized in that, The chain extender is selected from at least one of 1,4-butanediol, ethylene glycol, diethylene glycol, and hydroquinone dihydroxyethyl ether; the crosslinking agent is selected from at least one of trimethylolpropane, glycerol, and triisopropanolamine.

7. The extremely cold-resistant polyether-type polyurethane sealing material according to claim 1, characterized in that, The catalyst is selected from at least one of organobismuth catalysts, organozinc catalysts, and tertiary amine catalysts; the antioxidant is selected from at least one of hindered phenolic antioxidants and phosphite antioxidants.

8. The extremely cold-resistant polyether-type polyurethane sealing material according to claim 1, characterized in that, The extremely cold-resistant polyether-type polyurethane sealing material is used to prepare sealing rings, gaskets, oil seals, dust rings, or hydraulic seals.

9. A method for preparing an extremely cold-resistant polyether-type polyurethane sealing material according to any one of claims 1-8, characterized in that, Includes the following steps: S1. The PMEG type polyether polyol is vacuum dehydrated to obtain the dehydrated polyether polyol. S2. Under nitrogen protection, the dehydrated polyether polyol is mixed and reacted with the isocyanate component to obtain a prepolymer with an isocyanate group mass fraction of 3.5% to 8.5%. S3. Add the interface-modified low-temperature resistant component to the prepolymer and disperse it, so that the interface-modified low-temperature resistant component is dispersed in the prepolymer; S4. Add chain extender, crosslinking agent, catalyst and antioxidant to the system obtained in step S3, mix and then perform vacuum degassing to obtain the mixture to be shaped. S5. The mixture to be formed is injected into the mold and cured, and then post-curing treatment is performed to obtain an extremely cold-resistant polyether polyurethane sealing material.

10. The method for preparing the extremely cold-resistant polyether-type polyurethane sealing material according to claim 9, characterized in that, In step S1, the vacuum dehydration temperature is 100–120℃, the vacuum gauge pressure is -0.08MPa to -0.10MPa, and the dehydration time is 1–3h; in step S2, the reaction temperature is 70–85℃, and the reaction time is 1.5–3h; in step S3, the dispersion method is at least one of mechanical stirring dispersion and ultrasonic dispersion; in step S5, the curing temperature is 80–110℃, the curing time is 4–16h, the post-curing temperature is 80–110℃, and the post-curing time is 6–24h.

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