Polyurethane composite material as well as preparation method and application thereof

Abstract

The invention discloses a polyurethane composite material which comprises the following components in parts by weight: 100 parts of a polyurethane prepolymer, 2-10 parts of a solid lubricant and 10-40 parts of a curing agent. The invention also discloses a preparation method and application of the polyurethane composite material, and the preparation method comprises the following steps: heating a polyurethane prepolymer, carrying out vacuum defoaming to obtain a bubble-free liquid prepolymer, adding a solid lubricant, stirring, mixing and carrying out vacuum defoaming to obtain a modified polyurethane prepolymer; a liquid curing agent and the modified polyurethane prepolymer are stirred and mixed and then poured into a preheated mold; and putting the mold into a drying oven, carrying out chain extension reaction, and demolding after the reaction is completed, so as to obtain the polyurethane composite material. According to the polyurethane composite material disclosed by the invention, the polytetrafluoroethylene is mixed in the polyurethane prepolymer, so that the formation of a water film is facilitated during working, and the lubricating property, the friction resistance and the wear resistance of the material are improved.

Description

Technical Field

[0001] The present invention relates to the technical field of composite materials, and in particular to a polyurethane composite material and a preparation method and application thereof. Background Art

[0002] Self-lubricating bearings, also known as oil-free bearings or oil-free bearings, refer to bearings that can work normally without the addition of oil or fat lubricants.

[0003] Although existing self-lubricating bearings have high wear resistance and high load-bearing capacity, such as the water-lubricated bearing disclosed in CN103788623B, their flexibility and elasticity are poor. When they work in more complex working conditions such as seawater and inland rivers containing silt, they will suffer greater wear, generate noise and vibration, and cannot ensure the safety of the ship's movement. Summary of the invention

[0004] The main purpose of the present invention is to provide a polyurethane composite material and a preparation method and application thereof, aiming to solve the technical problem that the existing polyurethane composite materials used for water-lubricated bearings have poor wear resistance.

[0005] To achieve the above objectives, in a first aspect, the present invention provides a polyurethane composite material, which is composed of the following raw materials in parts by weight: 100 parts of a polyurethane prepolymer, 2 to 10 parts of a solid lubricant, and 10 to 40 parts of a curing agent.

[0006] Preferably, the polyurethane prepolymer is prepared by reacting polytetramethylene ether glycol and 2,4-toluene diisocyanate in a mass ratio of 60-70:30-40.

[0007] Preferably, the solid lubricant is polytetrafluoroethylene.

[0008] Preferably, the curing agent is 3,3'-dichloro-4,4'-diaminodiphenylmethane.

[0009] In a second aspect, the present invention further provides a method for preparing the polyurethane composite material as described in any one of the first aspects, comprising:

[0010] After the polyurethane prepolymer is heated, vacuum degassing is performed to obtain a bubble-free liquid prepolymer;

[0011] Adding a solid lubricant to the liquid prepolymer, stirring and mixing and subjecting the mixture to vacuum degassing to obtain a modified polyurethane prepolymer;

[0012] The liquid curing agent and the modified polyurethane prepolymer are stirred and mixed, and then poured into a preheated mold;

[0013] The mold is placed in an oven to carry out a chain extension reaction, and demoulding is performed after the chain extension reaction is completed to obtain a polyurethane composite material.

[0014] Preferably, the polyurethane prepolymer is heated and then vacuum degassing is performed to obtain a bubble-free liquid prepolymer, comprising:

[0015] Add the polyurethane prepolymer into the A material tank of the casting machine;

[0016] The polyurethane prepolymer in the material tank A is heated to a preset first melting temperature to obtain a prepolymer to be defoamed; the preset first melting temperature is 70-85° C.;

[0017] The prepolymer to be degassed is vacuum degassed while being stirred for a preset first degassed time to obtain a bubble-free liquid prepolymer; the preset first degassed time is 15 to 30 minutes.

[0018] Preferably, the solid lubricant is polytetrafluoroethylene; the solid lubricant is added to the liquid prepolymer, and the mixture is stirred and mixed and subjected to vacuum degassing treatment to obtain a modified polyurethane prepolymer, comprising:

[0019] After adding polytetrafluoroethylene to the liquid prepolymer, stirring and mixing at a preset first stirring speed, and continuing vacuum degassing for a preset second degassing time, to obtain a modified polyurethane prepolymer; wherein the preset first stirring speed is 30 to 50 rpm; and the preset second degassing time is 10 to 15 minutes.

[0020] Preferably, the step of mixing the liquid curing agent with the modified polyurethane prepolymer and then pouring the mixture into a preheated mold comprises:

[0021] Add the curing agent into the B material tank of the pouring machine;

[0022] The curing agent in the B material tank is heated to a preset second melting temperature to obtain a liquid curing agent; the preset second melting temperature is 105-110° C.;

[0023] The modified polyurethane prepolymer in the A material tank and the liquid curing agent in the B material tank are sucked into the gun head of the casting machine, mixed and stirred, and then poured into a mold preheated to a preset heating temperature; the preset heating temperature is 100-150°C.

[0024] Preferably, the step of placing the mold in an oven to carry out a chain extension reaction, and demoulding after the chain extension reaction is completed to obtain a polyurethane composite material comprises:

[0025] The cast mold is placed in an oven to perform a chain extension reaction at a preset reaction time and a preset reaction temperature; wherein the preset reaction time is 8 to 12 hours and the preset reaction temperature is 90 to 110° C.;

[0026] After the chain extension reaction is completed, demoulding is performed to obtain a polyurethane composite material.

[0027] In a third aspect, the present invention further provides a use of the polyurethane composite material as described in any one of the first aspects in a water-lubricated bearing.

[0028] The above-mentioned polyurethane composite material and its preparation method and application, the polyurethane composite material is obtained by mixing polytetrafluoroethylene into the polyurethane raw material, which is beneficial to the formation of water film during operation, so that the lubrication performance of the material is greatly improved, and at the same time the friction resistance and wear resistance of the material are improved. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] Figure 1 A schematic diagram of a polyurethane composite material and a preparation method thereof in one embodiment;

[0030] Figure 2 A schematic diagram of the structure of a water-lubricated bearing in one embodiment Figure 1 ;

[0031] Figure 3 A schematic diagram of the structure of a water-lubricated bearing in one embodiment Figure 2 ;

[0032] Figure 4 A schematic diagram of the structure of a water-lubricated bearing in one embodiment Figure 3 . DETAILED DESCRIPTION

[0033] In order to make the purpose, technical solution and advantages of the present invention more clearly understood, the present invention is further described in detail below in conjunction with the accompanying drawings and implementation methods. It should be understood that the specific implementation methods described herein are only used to explain the present invention and are not used to limit the present invention.

[0034] In one embodiment, the present invention provides a polyurethane composite material for water-lubricated bearings, wherein the polyurethane composite material is composed of the following raw materials in parts by weight: 100 parts of a polyurethane prepolymer, 2 to 10 parts of a solid lubricant, and 10 to 40 parts of a curing agent.

[0035] Furthermore, the polyurethane prepolymer is prepared by reacting polytetrahydrofuran ether glycol and 2,4-toluene diisocyanate in a mass ratio of 60-70:30-40. The solid lubricant is polytetrafluoroethylene. The curing agent is 3,3'-dichloro-4,4'-diaminodiphenylmethane.

[0036] In this embodiment, the polyurethane prepolymer is prepared by reacting 60 to 70 parts of polytetrahydrofuran ether diol and 30 to 40 parts of 2,4-toluene diisocyanate by weight at a temperature of 65 to 75°C for 2 to 3 hours. Polytetrahydrofuran ether diol can be selected from polytetrahydrofuran ether diol produced by Jining Huakai Resin Co., Ltd., 2,4-toluene diisocyanate can be selected from 2,4-toluene diisocyanate produced by Shandong Jinyueyuan New Materials Co., Ltd., polytetrafluoroethylene (PTFE) can be selected from polytetrafluoroethylene with a grade of AP-210 produced by Daikin, Japan, and 3,3'-dichloro-4,4'-diaminodiphenylmethane (MOCA) can be selected from 3,3'-dichloro-4,4'-diaminodiphenylmethane produced by Master Ba (Shanghai) Biomedical Technology Co., Ltd.

[0037] In summary, the polyurethane composite material of this embodiment, by mixing polytetrafluoroethylene into the polyurethane raw material, is conducive to the formation of a water film during operation, so that the lubrication performance of the material is greatly improved, and the friction resistance and wear resistance of the material are improved. Tests have proved that the above-mentioned polyurethane composite material has a homogeneous microstructure, a hardness of ShoreD 55-65, a compression elastic modulus of more than 600MPa, a dry friction coefficient of ≤0.20, and a friction coefficient (water) of ≤0.25 when the linear speed is 0.05m / s in a water environment. When the linear speed is >0.5m / s, the friction coefficient (water) is ≤0.03, which can meet the use requirements of a radial load of 5-70MPa.

[0038] refer to Figure 1 In another embodiment, the present invention further provides a method for preparing a polyurethane composite material, wherein the polyurethane composite material is the polyurethane composite material in the above embodiment, and the method specifically comprises the following steps:

[0039] Step S10, heating the polyurethane prepolymer and then performing vacuum degassing to obtain a bubble-free liquid prepolymer.

[0040] Before step S10, 100 parts of polyurethane prepolymer, 2 to 10 parts of solid lubricant and 10 to 40 parts of curing agent are weighed respectively; then the symmetrically taken polyurethane prepolymer is heated to melt and vacuum degassed. Compared with degassed with a degassing agent, the problem that the degassing agent cannot completely eliminate tiny bubbles can be avoided, the degassing effect is improved, and the cost is saved at the same time.

[0041] Preferably, the step S10 specifically includes the following steps:

[0042] Step S101, adding polyurethane prepolymer into a material tank A of a casting machine;

[0043] Step S102, heating the polyurethane prepolymer in the A material tank to a preset first melting temperature to obtain a prepolymer to be defoamed; the preset first melting temperature is 70-85° C.;

[0044] Step S103, vacuum degassing the prepolymer to be degassed while stirring for a preset first degassing time to obtain a bubble-free liquid prepolymer; the preset first degassing time is 15 to 30 minutes.

[0045] That is, after cleaning and drying the A material tank of the casting machine, the weighed polyurethane prepolymer is added to the A material tank of the casting machine. Then, the heating device configured for the A material tank is started to heat and melt the polyurethane prepolymer in the A material tank, so that its temperature gradually rises to between 70°C and 85°C, and a polyurethane prepolymer completely transformed into a liquid state is obtained, i.e., the prepolymer to be degassed. Among them, the casting machine is a polyurethane casting machine; the heating device configured for the A material tank adopts electric heating.

[0046] Next, turn on the pouring machine's stirring device and vacuum device. The vacuum device quickly reduces the air pressure in the A material tank to a vacuum range of -0.08MPa to -0.095MPa. At the same time, the stirring device (such as a stirring paddle) begins to slowly and evenly stir the polyurethane prepolymer. Under the synergistic effect of the vacuum environment and stirring, the bubbles inside the polyurethane prepolymer will expand rapidly under the pressure difference between the inside and outside, and continue to move to the surface, and finally escape the polyurethane prepolymer. The entire degassing process will last for 15 to 30 minutes. After the degassing is completed, a bubble-free liquid prepolymer can be obtained.

[0047] It can be understood that in this embodiment, through steps S101 to S103, the polyurethane prepolymer is added into the casting machine material tank for heating, melting and vacuum degassing, and the quality stability of the liquid prepolymer is higher than that of the manual operation.

[0048] Step S20, adding a solid lubricant into the liquid prepolymer, stirring and mixing and performing vacuum degassing treatment to obtain a modified polyurethane prepolymer.

[0049] Preferably, the solid lubricant is polytetrafluoroethylene. In this case, step S20 specifically includes the following steps:

[0050] After adding polytetrafluoroethylene to the liquid prepolymer, stirring and mixing at a preset first stirring speed, and continuing vacuum degassing for a preset second degassing time, to obtain a modified polyurethane prepolymer; wherein the preset first stirring speed is 30 to 50 rpm; and the preset second degassing time is 10 to 15 minutes.

[0051] That is, the weighed polytetrafluoroethylene is added to the bubble-free liquid prepolymer obtained in step S10, and then slowly stirred at a stirring speed of 30 to 50 rpm to uniformly disperse the solid lubricant in the liquid prepolymer. While slowly stirring, the bubbles are continuously removed by vacuum for 10 to 15 minutes to obtain a modified polyurethane prepolymer.

[0052] It is understandable that the stirring speed during vacuum degassing in step S10 of this embodiment is the same as the stirring speed in step S20. Slow stirring can avoid the generation of bubbles, thereby improving the quality of the modified polyurethane prepolymer.

[0053] Step S30, stirring and mixing the liquid curing agent and the modified polyurethane prepolymer, and then pouring them into a preheated mold.

[0054] That is, after the weighed curing agent is heated and melted, it is quickly stirred and mixed with the modified polyurethane prepolymer obtained in step S30, and poured into a preheated mold to facilitate subsequent molding.

[0055] Preferably, the step S30 specifically includes the following steps:

[0056] Step S301, adding a curing agent into a material tank B of a casting machine;

[0057] Step S302, heating the curing agent in the B material tank to a preset second melting temperature to obtain a liquid curing agent; the preset second melting temperature is 105-110° C.;

[0058] Step S303, sucking the modified polyurethane prepolymer in the A material tank and the liquid curing agent in the B material tank into the gun head of the casting machine, mixing and stirring, and then pouring into a mold preheated to a preset heating temperature; the preset heating temperature is 100-150°C.

[0059] First, after cleaning and drying the B material tank of the pouring machine, add the weighed curing agent into the B material tank of the pouring machine. Then start the heating device set in the B material tank of the pouring machine to heat and melt the curing agent in the B material tank, gradually raising the temperature to between 105 and 110°C to obtain a curing agent that is completely converted into a liquid state. Among them, the heating device set in the B material tank adopts electric heating.

[0060] Next, start the pumping device of the pouring machine, extract the modified polyurethane prepolymer from the A material tank and the liquid curing agent from the B material tank according to the preset ratio, and transport the two materials to the cavity of the pouring machine gun head, and then start the stirring device configured in the cavity to quickly stir the two materials at a speed of 2200-2500rpm, so that the two materials are mixed evenly in a very short time (generally not more than 5 seconds) to form a pouring material. Among them, the stirring device configured in the cavity is a stirring blade that can rotate at high speed. It should be noted that since the components of the polyurethane composite material are added to each material tank according to the weighed weight, in this case, the set ratio is 1:1.

[0061] While the material is being heated and melted, the mold is preheated to 100-150° C. by a preheating device (eg, a hot air circulation oven). When the casting material is obtained, the casting material is immediately poured into the preheated mold by a pouring machine gun head.

[0062] It can be understood that, in this embodiment, through the above steps S301 to S303, it can ensure that the modified polyurethane prepolymer and the curing agent are mixed evenly, and at the same time, it can ensure the consistency, accuracy and efficiency of the entire casting process.

[0063] Step S40, placing the mold in an oven to perform a chain extension reaction, and demoulding after the chain extension reaction is completed to obtain a polyurethane composite material.

[0064] Preferably, the step S40 specifically includes the following steps:

[0065] The poured mold is placed in an oven to perform a chain extension reaction at a preset reaction time and a preset reaction temperature; after the chain extension reaction is completed, the mold is removed to obtain a polyurethane composite material, wherein the preset reaction time is 8 to 12 hours and the preset reaction temperature is 90 to 110°C.

[0066] That is, the poured mold is placed in an oven, the temperature of the oven is set to 90-110°C, and the time is set to 8-12 hours, so that the material in the mold undergoes a chain extension reaction. After the chain extension reaction is completed, the mold is allowed to cool naturally to room temperature in the oven before demolding. Compared with adding a chain extender for a chain extension reaction, this embodiment places the poured mold in an oven for subsequent reactions. The overall material in the mold is heated relatively uniformly, which is conducive to forming a polyurethane composite material with uniform structure and stable performance. At the same time, it avoids the introduction of impurities by the chain extender, thereby improving the quality stability of the polyurethane composite material.

[0067] The preparation method of the polyurethane composite material is to obtain the polyurethane composite material through the above steps S10 to S40, which is conducive to the formation of a water film during use, so that the lubrication performance of the material is greatly improved, and the friction resistance and wear resistance of the material are also improved.

[0068] refer to Figures 2 to 4 In another embodiment, the present invention further provides an application of a polyurethane composite material in a water-lubricated bearing, wherein the polyurethane composite material is the polyurethane composite material in the above-mentioned embodiment.

[0069] The water-lubricated bearing of this embodiment is molded by integral casting to obtain a bearing body of required thickness, and a water groove is formed in the bearing body by mechanical processing, such as Figure 2 As shown. As a preference. Different water tank structures can be selected according to the actual bearing speed and water flow rate. For bearings with lower speed and smaller water flow rate, the water tank structure is straight, such as Figure 2 For bearings with higher speed and larger water flow, the water tank structure is semicircular, such as Figure 3 shown.

[0070] The above-mentioned water-lubricated bearings can exhibit excellent self-lubricating and wear-resistant properties when the bearings are in a water-deficient environment, and have the functions of preventing noise and bearing bite, and can be widely used in rotating or swinging sliding parts such as underwater propeller motor drives, propeller stern bearings, rudder bearings and water pumps.

[0071] Below, the present invention will illustrate one or more embodiments through the following examples.These examples are not intended to limit the purpose of the present invention and / or the scope of one or more embodiments.

[0072] Embodiment 1:

[0073] A polyurethane composite material is composed of the following raw materials in parts by weight: 100 parts of polyurethane prepolymer, different parts by weight of solid lubricant and 20 parts of curing agent. The polyurethane prepolymer is prepared by reacting polytetrahydrofuran polyol and 2,4-toluene diisocyanate in a mass ratio of 70:30, the solid lubricant is polytetrafluoroethylene, and the curing agent is 3,3'-dichloro-4,4'-diaminodiphenylmethane.

[0074] The preparation method of the polyurethane composite material comprises the following steps:

[0075] Step a, heating 100 parts of polyurethane prepolymer to 85° C., and performing vacuum degassing for 30 minutes while stirring to obtain a bubble-free liquid prepolymer;

[0076] Step b, adding different weight portions of solid lubricant to the liquid prepolymer, stirring and mixing at a stirring speed of 40 rpm, and continuing vacuum degassing for 15 minutes to obtain a modified polyurethane prepolymer;

[0077] Step c, heating 20 parts of the curing agent to 110° C. to obtain a liquid curing agent, then quickly stirring and mixing the liquid curing agent and the modified polyurethane prepolymer, and injecting the mixture into a mold at 120° C.;

[0078] Step d, placing the cast mold into an oven, performing a chain extension reaction at 110° C. for 12 hours, and demoulding after the chain extension reaction is completed to obtain a polyurethane composite material.

[0079] The friction performance test was carried out on the polyurethane composite material in Example 1, and the test method was as follows: the polyurethane composite material obtained by demolding was mechanically processed to obtain a test cylindrical material with a diameter of 10 mm and a height of 20 mm; then an MPV-50 fatigue friction and wear testing machine was used to carry out a friction test on the test cylindrical material. The test method and test parameters of the friction test were set according to the application scenario of the water-lubricated bearing. Taking the water-lubricated bearing used for the stern of a ship as an example, the test method of the friction test was a unidirectional measurement, the test speed was 200 r / min, the test load was 900 N, the lubricating medium was distilled water, and the test time was 2 h.

[0080] The friction test results of the polyurethane composite material of Example 1 are shown in Table 1.

[0081] Table 1

[0082]

[0083] After a 2-hour friction test, PTFE has a great influence on the friction performance of polyurethane composite materials. The friction coefficient of the material with 2 parts of PTFE is 0.05.

[0084] Embodiment 2:

[0085] A polyurethane composite material is composed of the following raw materials in parts by weight: 100 parts of polyurethane prepolymer, 2 parts of solid lubricant and curing agent in different parts by weight.

[0086] The polyurethane composite material in the above-mentioned Example 2 has similar preparation methods, friction performance test methods and friction test conditions as those in Example 1. The difference between Example 2 and Example 1 is that the content of polytetrafluoroethylene used is determined to be 2 parts according to Example 1, and the proportion of MOCA used is different. The friction test results of the polyurethane composite material in Example 2 refer to Table 2.

[0087] Table 2

[0088]

[0089] After a 2-hour friction test, MOCA has a great influence on the friction performance of the polyurethane composite material. The friction coefficient of the material with 22 parts of MOCA is 0.06.

[0090] Example 3

[0091] A polyurethane composite material is composed of the following raw materials in parts by weight: 100 parts of polyurethane prepolymer, 2 parts of solid lubricant and 22 parts of curing agent.

[0092] The polyurethane composite material in the above-mentioned Example 3, the preparation method of the polyurethane composite material and the friction performance test method are similar to those in Example 1. The difference between Example 3 and Example 1 is that: the content of polytetrafluoroethylene used has been determined to be 2 parts according to Example 1, the content of MOCA used has been determined to be 22 parts according to Example 2, and the friction test conditions have been changed. The changed friction test conditions are: the test is carried out on a CBZ-1 friction and wear tester, the grinding test piece is a tin bronze disk, the test speed is 450r / min and 250r / min, the test pressure is 0.7MPa, 1.05MPa, 1.4MPa and 1.75MPa respectively, and a group of materials without polytetrafluoroethylene are added as a comparison, the lubricating medium is distilled water, and the test time is 2 hours.

[0093] The friction test results of the polyurethane composite material in the above Example 3 are shown in Table 3.

[0094] Table 3

[0095]

[0096] After two hours of friction test, it can be seen from Table 3 that the friction coefficient of the polyurethane composite material at high speed is significantly higher than that at low speed. In addition, the friction coefficient of the material is less affected by the load and has good working stability. At the same time, the material can effectively reduce the friction coefficient of the material under most working conditions, reflecting more excellent friction performance.

[0097] It should be noted that, in this article, the term "includes", "comprising" or any other variation thereof is intended to cover non-exclusive inclusion, so that a product or method including a series of elements includes not only those elements, but also other elements not explicitly listed, or also includes elements inherent to such product or method. In the absence of more restrictions, an element defined by the sentence "comprising a ..." does not exclude the presence of other identical elements in the product or method including the element.

[0098] The above are only preferred embodiments of the present invention, and are not intended to limit the patent scope of the present invention. Any equivalent structure or equivalent process transformation made using the contents of the present invention specification and drawings, or directly or indirectly applied in other related technical fields, are also included in the patent protection scope of the present invention.

Claims

1. A polyurethane composite material, characterized in that: The polyurethane composite material is composed of the following raw materials in parts by weight: 100 parts of polyurethane prepolymer, 2 to 10 parts of solid lubricant and 10 to 40 parts of curing agent.

2. The polyurethane composite material according to claim 1, characterized in that: The polyurethane prepolymer is prepared by reacting polytetramethylene ether diol and 2,4-toluene diisocyanate in a mass ratio of 60-70:30-40.

3. The polyurethane composite material according to claim 1, characterized in that: The solid lubricant is polytetrafluoroethylene.

4. The polyurethane composite material according to claim 1, characterized in that: The curing agent is 3,3'-dichloro-4,4'-diaminodiphenylmethane.

5. A method for preparing the polyurethane composite material according to any one of claims 1 to 4, characterized in that: include: After the polyurethane prepolymer is heated, vacuum degassing is performed to obtain a bubble-free liquid prepolymer; Adding a solid lubricant to the liquid prepolymer, stirring and mixing and subjecting the mixture to vacuum degassing to obtain a modified polyurethane prepolymer; The liquid curing agent and the modified polyurethane prepolymer are stirred and mixed, and then poured into a preheated mold; The mold is placed in an oven to carry out a chain extension reaction, and demoulding is performed after the chain extension reaction is completed to obtain a polyurethane composite material.

6. The method for preparing the polyurethane composite material according to claim 5, characterized in that: The polyurethane prepolymer is heated and then vacuum degassed to obtain a bubble-free liquid prepolymer, comprising: Add the polyurethane prepolymer into the A material tank of the casting machine; The polyurethane prepolymer in the material tank A is heated to a preset first melting temperature to obtain a prepolymer to be defoamed; the preset first melting temperature is 70-85° C.; The prepolymer to be degassed is vacuum degassed while being stirred for a preset first degassed time to obtain a bubble-free liquid prepolymer; the preset first degassed time is 15 to 30 minutes.

7. The method for preparing the polyurethane composite material according to claim 5, characterized in that: The solid lubricant is polytetrafluoroethylene; The solid lubricant is added to the liquid prepolymer, and the mixture is stirred and mixed and subjected to vacuum degassing treatment to obtain a modified polyurethane prepolymer, comprising: After adding polytetrafluoroethylene to the liquid prepolymer, stirring and mixing at a preset first stirring speed, and continuing vacuum degassing for a preset second degassing time, to obtain a modified polyurethane prepolymer; wherein the preset first stirring speed is 30 to 50 rpm; and the preset second degassing time is 10 to 15 minutes.

8. The method for preparing the polyurethane composite material according to claim 6, characterized in that: The step of mixing the liquid curing agent with the modified polyurethane prepolymer and then pouring the mixture into a preheated mold comprises: Add the curing agent into the B material tank of the pouring machine; The curing agent in the B material tank is heated to a preset second melting temperature to obtain a liquid curing agent; the preset second melting temperature is 105-110° C.; The modified polyurethane prepolymer in the A material tank and the liquid curing agent in the B material tank are sucked into the gun head of the casting machine, mixed and stirred, and then poured into a mold preheated to a preset heating temperature; the preset heating temperature is 100-150°C.

9. The method for preparing the polyurethane composite material according to claim 5, characterized in that: The step of placing the mold in an oven to perform a chain extension reaction, and demoulding after the chain extension reaction is completed to obtain a polyurethane composite material comprises: The cast mold is placed in an oven to perform a chain extension reaction at a preset reaction time and a preset reaction temperature; wherein the preset reaction time is 8 to 12 hours and the preset reaction temperature is 90 to 110° C.; After the chain extension reaction is completed, demoulding is performed to obtain a polyurethane composite material.

10. Use of the polyurethane composite material according to any one of claims 1 to 4 in a water-lubricated bearing.

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