A polyurethane elastomer for sealing the rubber of an ultra-high pressure fracturing pump and a method for preparing the same

Abstract

The application provides a polyurethane elastomer for sealing rubber of an ultra-high pressure fracturing pump and a preparation method thereof, and belongs to the technical field of high polymer functional materials and sealing technology of ultra-high pressure equipment for oil and shale gas exploitation. The polyurethane elastomer is obtained by reaction of a first component and a second component; the first component is a prepolymer obtained by reaction of a symmetric aromatic diisocyanate and polycaprolactone polyol. The application forms a highly ordered hard segment microcrystalline region by the symmetric aromatic diisocyanate and polycaprolactone polyol, so that the material has very low thermal mechanical loss, and the internal temperature rise rate is significantly reduced under ultra-high frequency alternating impact. At the same time, the dynamic reversible covalent crosslinking network is activated when the local micro area temperature crosses the activation energy threshold, the molecular chain segment topological reconstruction is realized through ester exchange bond exchange reaction, the stress concentration is safely distributed to the whole network, and thus the main chain rupture is avoided, and the edge gnawing block phenomenon of the sealing rubber is eliminated.

Description

Technical Field

[0001] This invention relates to a polyurethane elastomer for sealing rubber of ultra-high pressure fracturing pumps and its preparation method, belonging to the field of polymer functional materials and sealing technology of ultra-high pressure equipment for oil and shale gas extraction. Background Technology

[0002] Currently, the sealing rubber used in the hydraulic end valve assembly system of fracturing pumps for oil shale gas extraction generally adopts conventional aromatic isocyanate and polyol prepolymers, which are cured and molded under the action of glycol chain extenders. Among them, the MDI-PTMEG / BDO system, formed by 4,4'-diphenylmethane diisocyanate (MDI) and polytetrahydrofuran ether polyol (PTMEG) or conventional polyester polyol under the chain extension of 1,4-butanediol (BDO), is the mainstream technical route for mid-to-high-end products in the industry.

[0003] However, the aforementioned existing technologies suffer from the following failure defects when faced with ultra-high pressure of 140 MPa and ultra-high frequency alternating impact of 130 times per minute: a coupled failure of "adiabatic shear heating" and irreversible tearing occurs under extreme high-frequency shear. Due to the asymmetric and non-planar spatial configuration of MDI molecules, the microphase separation of the hard segments after curing is incomplete, resulting in a high thermomechanical loss factor (tanδ) of the material. Under ultra-high frequency impact, the high-frequency mechanical energy cannot be rapidly dissipated in the form of elastic rebound, but instead, adiabatic heat accumulation occurs inside the rubber, with the local temperature instantly soaring to over 120°C. The high temperature causes a large number of hydrogen bonds in the hard segments to dissociate, and the permanently locked covalent cross-linked network used in the existing technology prevents the highly concentrated stress from being released through chain segment slippage, ultimately leading to irreversible main chain breakage at the edge of the rubber, manifested on-site as "gnawing" cracks and large-scale detachment.

[0004] Secondly, although traditional polyether polyols (PTMEG) are resistant to hydrolysis, their molecular chains are loosely packed, making them weak in resisting micro-cutting by quartz sand and strong acid (HCl) penetration. While conventional polyester polyols have slightly better tear resistance, under the synergistic effect of 28% hydrochloric acid and local high temperature, the ester groups are very prone to catalytic hydrolysis, which leads to rapid softening of the rubber and overpressure extrusion deformation.

[0005] Existing technologies tend to address ultra-high pressure by unidirectionally increasing the hardness of the rubber seal, but this leads to brittleness and a significant decrease in flexibility, making it unable to effectively absorb impact energy at the moment the valve body closes. The rubber seal is not only prone to breakage but also cannot form an adaptive compensation mechanism with the metal valve seat. High-pressure mortar stagnation in the gaps results in secondary "water jet leakage," accelerating the overall erosion and scrapping of the valve seat. Therefore, this paper proposes a polyurethane elastomer for the sealing rubber seal of ultra-high pressure fracturing pumps and its preparation method. Summary of the Invention

[0006] In view of this, the present invention provides a polyurethane elastomer for sealing rubber of ultra-high pressure fracturing pump and its preparation method, so as to solve or alleviate the technical problems of eliminating thermal shear heating and irreversible tearing of sealing rubber under ultra-high pressure and ultra-high frequency alternating impact conditions in the prior art, and at least provides a beneficial option.

[0007] The technical solution of this invention is implemented as follows: a polyurethane elastomer for sealing rubber of an ultra-high pressure fracturing pump, wherein the polyurethane elastomer is obtained by reacting a first component and a second component; the first component is a prepolymer of symmetrical aromatic diisocyanate and polycaprolactone polyol, wherein the mass fraction of isocyanate groups in the prepolymer is 5.0%-6.5%, wherein the mass fraction of unreacted symmetrical aromatic diisocyanate monomer is ≤0.1%; the second component contains hydroquinone dihydroxyethyl ether as the main chain extender and transesterification catalyst, wherein the ratio of the first component to the second component is 1.02-1.04 based on the isocyanate index, and the polyurethane elastomer has a dynamically reversible covalent crosslinked network.

[0008] More preferably, the symmetrical aromatic diisocyanate is 1,5-naphthalene diisocyanate or terephthalene diisocyanate, and the mass ratio of the 1,5-naphthalene diisocyanate to polycaprolactone polyol is 29.5:100 to 31.0:100.

[0009] More preferably, the mass ratio of the terephthalic diisocyanate to the polycaprolactone polyol is 22.5:100.

[0010] More preferably, the polycaprolactone polyol has a molecular weight of 2000.

[0011] More preferably, the second component further includes the micro-crosslinking agent trimethylolpropane, wherein the mass fraction of the second component is 96.9%-98.1% of the main chain extender, 1%-3% of the micro-crosslinking agent, and 0.05%-0.20% of the transesterification catalyst.

[0012] More preferably, the transesterification catalyst is selected from at least one of zinc acetylacetonate, stannous octoate, and triethylenediamine complexes.

[0013] In addition, the present invention also provides a method for preparing a polyurethane elastomer for sealing rubber of an ultra-high pressure fracturing pump, comprising the following steps: Step 1: Synthesis of low-free prepolymer. Symmetrical aromatic diisocyanate and purified dehydrated polycaprolactone polyol are added to a reaction vessel and prepolymerized at 80℃-90℃. After the reaction, the monomer is removed by thin-film evaporation at 160℃ and a vacuum degree of less than 10 Pa. The mass fraction of unreacted symmetric aromatic diisocyanate monomer is controlled to be ≤0.1%, and the first component with a mass fraction of isocyanate group of 5.0%-6.5% is obtained. Step 2, the second component preparation: the dried and conditioned hydroquinone dihydroxyethyl ether is heated and melted and maintained at 110°C, the transesterification catalyst is added, and the mixture is fully dissolved and complexed under shear stirring to obtain the second component; Step 3: Vacuum dynamic casting. The first component and the second component are introduced into the two-component casting machine at a ratio of isocyanate index of 1.02-1.04. They are dynamically mixed in the vacuum mixing chamber and the air bubbles are removed. The mixture is then poured into the preheated mold. Step 4: Segmented vulcanization. In the first stage, the mold is cured at 110℃-115℃ for 30 minutes. In the second stage, the mold is vulcanized in a vulcanization oven at 110℃±2℃ for 24 hours to complete the development of hard segment microcrystals and uniformly distribute the dynamic covalent network. After the vulcanization is completed, the mold is slowly cooled to room temperature along with the vulcanization oven.

[0014] More preferably, in step two, 1%-3% by mass of trimethylolpropane is added as a micro-crosslinking agent, and 0.05%-0.20% by mass of an ester exchange catalyst is uniformly mixed. The ester exchange catalyst is selected from at least one of zinc acetylacetonate, stannous octoate, and triethylenediamine complexes, wherein the mass fraction of hydroquinone dihydroxyethyl ether is 96.9%-98.1%.

[0015] The embodiments of the present invention have the following advantages due to the adoption of the above technical solutions: This invention utilizes highly ordered hard-segment microcrystalline regions formed by symmetrical aromatic diisocyanates and polycaprolactone polyols to achieve extremely low thermomechanical losses in the material, significantly reducing the internal temperature rise rate under ultra-high frequency alternating impact. Simultaneously, the dynamic reversible covalent cross-linked network is activated when the temperature in local microregions exceeds the activation energy threshold, achieving molecular chain topological reconstruction through ester exchange bond reactions. This safely distributes stress concentration throughout the entire network, preventing main chain breakage, significantly increasing the service life of the rubber, and eliminating the gnaw-like chipping phenomenon at the edges of the sealing rubber.

[0016] 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

[0017] 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.

[0018] Figure 1 This is a schematic diagram of the chemical topology reconstruction of the dynamic covalent network of the present invention under high-frequency adiabatic shearing conditions.

[0019] Figure 2 This is a graph showing the thermomechanical loss and self-generated heat characteristics of the polyurethane elastomer of the present invention under ultra-high frequency impact. Detailed Implementation

[0020] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to the accompanying drawings and embodiments. However, it should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the scope of the invention. Furthermore, descriptions of well-known structures and technologies are omitted in the following description to avoid unnecessarily obscuring the concept of the invention.

[0021] The embodiments of the present invention will now be described in detail with reference to the accompanying drawings.

[0022] like Figures 1-2 As shown, this embodiment of the invention provides a polyurethane elastomer for sealing rubber of an ultra-high pressure fracturing pump. The polyurethane elastomer is obtained by reacting a first component and a second component. The first component is a prepolymer of a symmetrical aromatic diisocyanate and a polycaprolactone polyol, wherein the mass fraction of isocyanate groups in the prepolymer is 5.0%-6.5%, and the mass fraction of unreacted symmetrical aromatic diisocyanate monomers is ≤0.1%. The second component contains a main chain extender, hydroquinone dihydroxyethyl ether, and a transesterification catalyst. The ratio of the first component to the second component is 1.02-1.04 based on the isocyanate index. The polyurethane elastomer has a dynamically reversible covalent crosslinked network. The symmetrical aromatic diisocyanate is 1,5-naphthalene diisocyanate or terephthalene diisocyanate, and the mass ratio of the 1,5-naphthalene diisocyanate to the polycaprolactone polyol is 29.5:100 to 31.0:100. The mass ratio of terephthalic diisocyanate to polycaprolactone polyol is 22.5:100. The molecular weight of the polycaprolactone polyol is 2000. The second component further includes a micro-crosslinking agent, trimethylolpropane, wherein the mass fraction of the second component is 96.9%-98.1% of the main chain extender, 1%-3% of the micro-crosslinking agent, and 0.05%-0.20% of the transesterification catalyst. The transesterification catalyst is selected from at least one of zinc acetylacetonate, stannous octoate, and triethylenediamine complexes.

[0023] The main skeleton of the polyurethane elastomer sealant in this invention is composed of an aromatic diisocyanate prepolymer with a highly symmetrical geometric structure that readily forms a highly ordered hard segment phase. Preferably, it is selected from 1,5-naphthalene diisocyanate (NDI) or terephthalic diisocyanate (PPDI).

[0024] Unlike the asymmetric, non-planar spatial configuration of conventional MDI systems, NDI and PPDI molecular structures possess perfect conjugated aromatic bicyclic or monocyclic symmetry. This extremely high spatial geometric regularity allows for extremely thorough microphase separation in the cured hard segment microregions, forming a highly ordered microcrystalline hard segment physical cross-linking network. This network endows the material with extremely high thermodynamic stability, resulting in a dynamic loss factor tan δ ≤ 0.03 at 100°C. When subjected to a high-frequency variable load impact of 130 SPM, the elastomer can instantly return most of the mechanical energy in the form of "fully elastic rebound," successfully reducing the basic internal heat rise rate to ≤ 0.3 ℃ / min, thus fundamentally disrupting the thermodynamic conditions for adiabatic shear failure.

[0025] In the elastomeric chemical network, a specific proportion of dynamic covalent crosslinks capable of topological reconstruction under specific pressures and temperatures are implanted. This invention introduces polycaprolactone polyol (PCL) and combines it with a micro-dispersed transesterification catalytic system (such as zinc acetylacetonate, stannous octoate, or triethylenediamine complexes) at a mass fraction of 0.05% - 0.2%.

[0026] Traditional cross-linked networks (such as ordinary thermosetting rubber) have a permanently fixed network topology, and only main chain breakage (chipping) can occur under stress concentration. This invention introduces a dynamic reversible covalent bond (Vitrimer) network. When the local micro-region temperature at the root or edge of the rubber exceeds the network activation energy (Tν, approximately 60°C-80°C) due to adiabatic shear at 140 MPa, the catalytic system instantaneously activates ester exchange or bond exchange chemical reactions.

[0027] Chemical topology network switching principle formula:

[0028] At the cross-linking points of the linear network, through reversible covalent breakage and recombination, the molecular chain segments achieve dynamic sliding of the microscopic topological network without any decrease in hardness (maintained at 95A-97A) and macroscopic stiffness. This "force dissipation through sliding" mechanism safely relaxes and distributes the local ultimate stress, which would have been enough to break the main chain, throughout the entire rubber body network, eliminating the initial cracking source.

[0029] like Figure 1 As shown, the left side is the room temperature state, showing the regular rectangular microcrystalline region composed of NDI hard segments and the linear polyol soft segments connecting the crystal regions. The right side is the state after activation by 140MPa ultimate shear force and local high temperature (>80 °C). The originally fixed pentagram crosslinking points underwent reversible breakage and recombined with adjacent chain segments.

[0030] To prevent the dynamic reversible covalent network from over-rheologically exacerbating under high pressure, which could lead to plastic "cold flow" (i.e., the rubber sheet overflowing and breaking from the metal-metal mating gap), a multifunctional polyol (such as trimethylolpropane, TMP) with a mass fraction of 1% - 3% was introduced into the system as a three-dimensional micro-crosslinking agent, along with hydroquinone dihydroxyethyl ether (HQEE) as the main chain extender.

[0031] The trifunctionality of TMP forms a non-dynamic, stable three-dimensional "anchor point" that intertwines with the permanently hard segment network locked in the NDI / PPDI crystal region. Even if the dynamic covalent bonds experience localized thermal slip relaxation stress, the rigid mesh formed by TMP firmly restricts the overall deformation, strictly controlling the material's 70℃ x 22h compressive permanent deformation to ≤12%, thus ensuring the geometric integrity of the sealing surface under extremely high back pressure.

[0032] In addition, the present invention also provides a method for preparing a polyurethane elastomer for sealing rubber of an ultra-high pressure fracturing pump, comprising the following steps: Step 1: Synthesis of low-free prepolymer. Symmetrical aromatic diisocyanate and purified dehydrated polycaprolactone polyol are added to a reaction vessel and prepolymerized at 80℃-90℃. After the reaction, the monomer is removed by thin-film evaporation at 160℃ and a vacuum degree of less than 10 Pa. The mass fraction of unreacted symmetric aromatic diisocyanate monomer is controlled to be ≤0.1%, and the first component with a mass fraction of isocyanate group of 5.0%-6.5% is obtained. Step two, the second component preparation: The dried and conditioned hydroquinone dihydroxyethyl ether is heated and melted, maintained at 110°C. An ester exchange catalyst is added, and the mixture is fully dissolved and complexed under shear stirring to obtain the second component. In step two, 1%-3% (by mass) of trimethylolpropane is added as a micro-crosslinking agent, and 0.05%-0.20% (by mass) of an ester exchange catalyst is uniformly mixed. The ester exchange catalyst is selected from at least one of zinc acetylacetonate, stannous octoate, and triethylenediamine complexes, wherein the mass fraction of hydroquinone dihydroxyethyl ether is 96.9%-98.1%. Step 3: Vacuum dynamic casting. The first component and the second component are introduced into the two-component casting machine at a ratio of isocyanate index of 1.02-1.04. They are dynamically mixed in the vacuum mixing chamber and the air bubbles are removed. The mixture is then poured into the preheated mold. Step 4: Segmented vulcanization. In the first stage, the mold is cured at 110℃-115℃ for 30 minutes. In the second stage, the mold is vulcanized in a vulcanization oven at 110℃±2℃ for 24 hours to complete the development of hard segment microcrystals and uniformly distribute the dynamic covalent network. After the vulcanization is completed, the mold is slowly cooled to room temperature along with the vulcanization oven.

[0033] In Example 1, 1,5-naphthalene diisocyanate (NDI) was selected as the hard segment core. NDI and purified dehydrated polycaprolactone polyol (PCL, molecular weight 2000) were added to a reactor and prepolymerized at 80°C - 90°C.

[0034] Key control points: After the reaction, continuous molecular distillation to remove monomers is performed using a thin-film evaporator at 160 °C and a vacuum degree < 10 Pa. Preferably, the mass fraction of free NDI monomers in the prepolymer is controlled to ≤0.08%. Low free monomer control ensures extremely uniform molecular chain growth in subsequent reactions, completely eliminating premature fatigue fracture sources caused by excessively wide molecular weight distribution. The isocyanate group content (NCO%) of the final first component is adjusted to maintain at 5.9%.

[0035] The dried and conditioned main chain extender, hydroquinone dihydroxyethyl ether (HQEE), was heated and melted, maintaining the temperature at 110°C. 1.8% (w / w) of trimethylolpropane (TMP) was added as a micro-crosslinking agent, and 0.1% (w / w) of finely ground, high-purity zinc acetylacetonate was uniformly mixed in. Under high-speed shear stirring, the mixture was allowed to fully complex and dissolve, constructing a triggering mother liquor (second component) for dynamic reversible bond exchange.

[0036] The first and second components were introduced into a high-pressure two-component casting machine at a stoichiometric ratio (controlling the isocyanate index INCO = 1.02 - 1.04); based on the dynamic rebound requirement of controlling the isocyanate index (ISO Index) at 1.02 - 1.04, stoichiometric calculations were performed according to the hydroxyl equivalents of the first component (5.9% NCO) and the second component. Total mixing ratio: For every 100 g of the first component prepolymer, 13.2 g of the second component mother liquor (containing approximately 12.95 g of HQEE, approximately 0.24 g of TMP, and approximately 0.013 g of zinc acetylacetonate) is required. Instantaneous high-viscosity dynamic mixing is performed in a vacuum mixing chamber, while simultaneously removing air bubbles online through vacuuming. The mixture is then precisely poured into a sealed mold encased in a preheated valve body.

[0037] One-stage curing (in-mold hardening): The mold is kept at 110°C - 115°C and pressed for curing for 30 minutes. Due to the fast and extremely regular reaction rate of low free NDI, the material is quickly demolded after it exhibits the initial product hardness.

[0038] Two-stage post-vulcanization (hard segment microcrystal development): The valve body assembly after demolding is immediately placed in a constant temperature vulcanization oven and subjected to a post-vulcanization process of continuous baking at 110 ℃ ± 2 ℃ for 24 hours.

[0039] Under a high-temperature constant temperature for 24 hours, the polyurethane hard segment molecular chains receive sufficient kinetic energy for spatial rearrangement, promoting the perfect development of a high-density, ordered microcrystalline structure in the NDI hard segment microregions (achieving complete microphase separation), while the dynamic covalent network achieves a uniform topological distribution throughout the entire framework. After curing, the chamber is slowly cooled to room temperature.

[0040] The following table shows Example 1 and Comparative Examples 1 and 2.

[0041] Tests showed that the sealing rubber prepared in Example 1 had a mechanical loss tangent of 0.028 at 100°C, an internal temperature rise rate of no more than 0.28°C / min under 130 alternating impacts per minute, a tear strength retention rate of 68% after immersion in 28% hydrochloric acid at 70°C for 72 hours, and a service life of more than 65 segments under 140MPa conditions. Its performance was superior to that of Comparative Example 1 and Comparative Example 2.

[0042] In Example 2, the NDI in the first component of Example 1 was replaced with terephthalic diisocyanate (PPDI), and the NCO% of the first component prepolymer was controlled to be 5.5%. At this time, the mass ratio of PPDI to PCL was adjusted to 22.5:100, and the remaining operating steps were the same as in Example 1.

[0043] The cured elastomer has a hardness of 94A and a tan δ of 0.032 at 100°C, exhibiting the same low heat generation and high resilience characteristics.

[0044] In Example 3, the mass fraction of zinc acetylacetone in the second component was reduced to 0.05%. The remaining operating steps were the same as in Example 1. In this case, the network topology bond exchange rate was slowed down, which is suitable for medium-low stroke fracturing conditions of 70-90 SPM.

[0045] Example 4: The mass fraction of zinc acetylacetone in the second component was increased to 0.20%. The remaining operating steps were the same as in Example 1. The micro-network rheological slip velocity is extremely fast, making it more suitable for the extreme high-frequency, high-shear impact environment of 130 SPM.

[0046] In Example 5, the mass fraction of TMP in the second component was increased to 3.0% (corresponding to a reduction in HQEE dosage to 96.9%), and the remaining operation steps were the same as in Example 1. The macroscopic hardness of the cured polyurethane was increased to 98A, and the compression set (70℃ x 22h) was reduced to 8%.

[0047] 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 polyurethane elastomer for sealing rubber of an ultra-high pressure fracturing pump, characterized in that, The polyurethane elastomer is obtained by reacting a first component and a second component; the first component is a prepolymer of a symmetrical aromatic diisocyanate and a polycaprolactone polyol, wherein the mass fraction of isocyanate groups in the prepolymer is 5.0%-6.5%, and the mass fraction of unreacted symmetrical aromatic diisocyanate monomers is ≤0.1%; the second component contains the main chain extender hydroquinone dihydroxyethyl ether and a transesterification catalyst, and the ratio of the first component to the second component is 1.02-1.04 based on the isocyanate index; the polyurethane elastomer has a dynamically reversible covalent crosslinked network.

2. The polyurethane elastomer for sealing rubber of an ultra-high pressure fracturing pump according to claim 1, characterized in that: The symmetrical aromatic diisocyanate is 1,5-naphthalene diisocyanate or terephthalene diisocyanate, and the mass ratio of the 1,5-naphthalene diisocyanate to polycaprolactone polyol is from 29.5:100 to 31.0:

100.

3. The polyurethane elastomer for sealing rubber of an ultra-high pressure fracturing pump according to claim 2, characterized in that: The mass ratio of terephthalic diisocyanate to polycaprolactone polyol is 22.5:

100.

4. The polyurethane elastomer for sealing rubber of an ultra-high pressure fracturing pump according to claim 1, characterized in that: The molecular weight of the polycaprolactone polyol is 2000.

5. The polyurethane elastomer for sealing rubber of an ultra-high pressure fracturing pump according to claim 1, characterized in that: The second component also includes the micro-crosslinking agent trimethylolpropane, wherein the mass fraction of the second component is 96.9%-98.1% of the main chain extender, 1%-3% of the micro-crosslinking agent, and 0.05%-0.20% of the transesterification catalyst.

6. The polyurethane elastomer for sealing rubber of an ultra-high pressure fracturing pump according to claim 5, characterized in that: The transesterification catalyst is selected from at least one of zinc acetylacetonate, stannous octoate, and triethylenediamine complexes.

7. A method for preparing a polyurethane elastomer for sealing rubber of an ultra-high pressure fracturing pump as described in any one of claims 1-6, characterized in that, Includes the following steps: Step 1: Synthesis of low-free prepolymer. Symmetrical aromatic diisocyanate and purified dehydrated polycaprolactone polyol are added to a reaction vessel and prepolymerized at 80℃-90℃. After the reaction, the monomer is removed by thin-film evaporation at 160℃ and a vacuum degree of less than 10 Pa. The mass fraction of unreacted symmetric aromatic diisocyanate monomer is controlled to be ≤0.1%, and the first component with a mass fraction of isocyanate group of 5.0%-6.5% is obtained. Step 2, the second component preparation: the dried and conditioned hydroquinone dihydroxyethyl ether is heated and melted and maintained at 110°C, the transesterification catalyst is added, and the mixture is fully dissolved and complexed under shear stirring to obtain the second component; Step 3: Vacuum dynamic casting. The first component and the second component are introduced into the two-component casting machine at a ratio of isocyanate index of 1.02-1.

04. They are dynamically mixed in the vacuum mixing chamber and the air bubbles are removed. The mixture is then poured into the preheated mold. Step 4: Segmented vulcanization. In the first stage, the mold is cured at 110℃-115℃ for 30 minutes. In the second stage, the mold is vulcanized in a vulcanization oven at 110℃±2℃ for 24 hours to complete the development of hard segment microcrystals and uniformly distribute the dynamic covalent network. After the vulcanization is completed, the mold is slowly cooled to room temperature along with the vulcanization oven.

8. The method for preparing a polyurethane elastomer for sealing rubber of an ultra-high pressure fracturing pump according to claim 7, characterized in that: In step two, 1%-3% by mass of trimethylolpropane is added as a micro-crosslinking agent, and 0.05%-0.20% by mass of transesterification catalyst is uniformly mixed. The transesterification catalyst is selected from at least one of zinc acetylacetonate, stannous octoate, and triethylenediamine complexes, wherein the mass fraction of hydroquinone dihydroxyethyl ether is 96.9%-98.1%.

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