Preparation method and application of underwater low-frequency sound absorption rubber material based on multiple hydrogen-bond interaction

Abstract

The invention relates to the technical field of underwater sound absorption materials, in particular to a preparation method and application of an underwater low-frequency sound absorption rubber material based on multiple hydrogen-bond interaction. The preparation method comprises the following steps: firstly, carrying out epoxidation and in-chain hydroxylation modification on styrene-butadiene rubber, then preparing a UPy-NCO modifier through a reaction of UPy and diisocyanate, and finally, introducing multiple hydrogen bonds into the styrene-butadiene rubber through a reaction of the UPy-NCO modifier and hydroxylated styrene-butadiene rubber. The UPy-NCO modifier is used as a hydrogen bond cross-linking site to form a hydrogen bond cross-linking network, so that the underwater sound absorption performance of the styrene-butadiene rubber, especially the absorption of low-frequency sound waves, is obviously improved. The highest sound absorption coefficient in the frequency range of 0.4 KHz to 3 KHz can reach 0.7 or above, the highest sound absorption coefficient in the frequency range of 3 kHz to 7.0 kHz can reach 0.9 or above, and the overall average sound absorption coefficient is increased by 124% compared with that of unmodified rubber.

Description

Technical Field

[0001] The present invention relates to the technical field of underwater sound absorption materials, and in particular, to a preparation method and application of an underwater low-frequency sound absorption rubber material based on multiple hydrogen bond interactions. Background Art

[0002] Underwater sound absorption materials play a crucial role in the underwater acoustic environment. They can effectively absorb sound waves propagating in water and convert sound energy into other forms of energy, thereby significantly reducing the underwater noise level. In the military field, it is of great significance for the stealth protection of submarines, which can reduce the probability of underwater targets being detected by sonar and improve the concealment of underwater equipment such as submarines; in the civilian aspect, for anechoic tanks, it can optimize the working environment of underwater acoustic equipment and improve its performance.

[0003] Currently, common underwater sound absorption materials include rubber-based materials, polyurethane materials, metal matrix composites, etc. Among them, rubber-based materials have become one of the main application materials in underwater sound absorption materials due to their unique viscoelastic properties, low cost, variety of varieties, and easy processing and forming.

[0004] However, with the continuous improvement of the requirements for underwater stealth performance of modern naval equipment and the need for a quieter underwater operation environment for ocean engineering equipment, higher requirements are put forward for the sound absorption performance of underwater sound absorption materials in the low-frequency band. Low-frequency sound waves have the characteristics of long wavelengths and small energy attenuation, and traditional rubber-based materials are difficult to effectively absorb, unable to meet the requirements of today's complex underwater acoustic environment. Therefore, the research and development of underwater sound absorption materials with good sound absorption performance in the low-frequency band has become an urgent problem to be solved in the current underwater acoustic materials field.

[0005] The sound absorption performance of traditional rubber materials mainly depends on their molecular chain structure, but it is difficult to achieve a high sound absorption coefficient only by the inherent properties of rubber, especially in the low-frequency band. To further improve the low-frequency sound absorption performance of rubber, other mechanisms need to be introduced, but the performance improvement is limited to a certain extent by the basic sound absorption level of the raw rubber. Currently reported methods, such as blending and structural design, will lead to a decline in the mechanical properties of the material, structural collapse, and an increase in processing difficulty.

[0006] The 2-amino-4-hydroxy-6-methylpyrimidine (UPy) unit can form multiple hydrogen bonds after reacting with diisocyanate. The binding strength of hydrogen bonds is weaker than that of chemical bonds. Therefore, under the excitation of sound waves, non-covalent hydrogen bonds are preferentially broken to dissipate energy. At the same time, the side chains released after breaking are more likely to move due to the reduced degree of restriction, resulting in viscous absorption. Currently, there is no relevant research and report on introducing UPy units into the styrene-butadiene rubber system to enhance the low-frequency sound absorption performance at home and abroad. Summary of the Invention

[0007] The object of the present invention is to provide a rubber material and a preparation method thereof for enhancing the underwater low-frequency acoustic wave absorption performance by constructing multiple hydrogen bonds. First, styrene-butadiene rubber is epoxidized and hydroxylated in the chain; then, a UPy-NCO modifier is prepared by reacting UPy with diisocyanate; finally, the UPy-NCO modifier reacts with hydroxylated styrene-butadiene rubber to introduce multiple hydrogen bonds into the styrene-butadiene rubber. The UPy-NCO modifier forms a hydrogen bond crosslinking network as a hydrogen bond crosslinking site. Compared with the unmodified underwater sound-absorbing rubber, the introduction of multiple hydrogen bonds provides a new way for the rubber material to dissipate acoustic wave energy, realizing good absorption of low-frequency acoustic waves by the rubber matrix without acoustic fillers. And the introduction of UPy units can be achieved under mild conditions, and at the same time, the mechanical properties of the acoustic rubber can be enhanced. The underwater acoustic rubber material based on multiple hydrogen bonds prepared by the method of the present invention can be used as an underwater low-frequency sound-absorbing material in the fields of marine scientific research, national defense equipment manufacturing, etc.

[0008] In order to achieve the above object, the technical solution of the present invention is as follows:

[0009] On the one hand, the present invention provides a preparation method of an underwater low-frequency sound-absorbing rubber material based on multiple hydrogen bond interactions, and the method comprises the following steps:

[0010] (a) Dissolve a mixture of styrene-butadiene rubber (SBR) and peroxyacid in dichloromethane for reaction, and the obtained product is purified by precipitation with ethanol to obtain epoxidized styrene-butadiene rubber;

[0011] (b) Dissolve a mixture of the epoxidized styrene-butadiene rubber obtained in step (a), deionized water and a Lewis acid catalyst in tetrahydrofuran for reaction, and the obtained product is purified by precipitation with ethanol to obtain hydroxylated styrene-butadiene rubber;

[0012] (c) Add vacuum-dried 2-amino-4-hydroxy-6-methylpyrimidine (UPy) powder to dry diisocyanate (NCO) for reaction, filter and wash the product with n-pentane, and then vacuum-dry to obtain a UPy-NCO modifier;

[0013] (d) Dissolve the hydroxylated styrene-butadiene rubber obtained in step (b) in dry toluene, add the UPy-NCO modifier obtained in step (c), fully stir and dissolve, then add a dibutyltin dilaurate catalyst, and react under the protection of an inert gas. After the reaction is completed, precipitate and wash with ethanol, and then vacuum-dry to obtain styrene-butadiene rubber grafted with UPy groups;

[0014] (e) Adopt a two-stage mixing method on a two-roll open mill. First, conduct a first-stage mixing of the styrene-butadiene rubber grafted with UPy groups obtained in step (d) with carbon black, stearic acid, and zinc oxide to obtain a first-stage mixed rubber. Let it stand, and then add sulfur and a promoter to the first-stage mixed rubber for a second-stage mixing to obtain a mixed rubber;

[0015] (f) Vulcanize the mixed rubber to obtain the described rubber material.

[0016] In the above technical solution, further, in step (a), the molar ratio of the peroxy acid to the butadiene unit in the styrene-butadiene rubber is selected from 0.1 - 0.15:1;

[0017] The reaction temperature is 30 - 40 °C, and the reaction time is 1.5 - 2.5 h;

[0018] The peroxy acid includes one of performic acid, peracetic acid, perpropionic acid, peroxymaleic acid, perbenzoic acid, 3-chloroperbenzoic acid, pertrifluoroacetic acid, m-nitroperbenzoic acid, p-nitroperbenzoic acid.

[0019] In the above technical solution, further, in step (b), the molar ratio of the epoxy group, deionized water, and Lewis acid catalyst in the epoxidized styrene-butadiene rubber is 0.8 - 1.2:13 - 17:0.4 - 0.6;

[0020] The reaction temperature is 20 - 30 °C, and the reaction time is 2.5 - 3.5 h;

[0021] The Lewis acid catalyst includes one of boron trifluoride, aluminum trichloride, titanium trichloride, zirconium trichloride, zirconium tetrachloride, chromium trichloride.

[0022] In the above technical solution, further, in step (c), the mass ratio of 2-amino-4-hydroxy-6-methylpyrimidine to the diisocyanate is 0.8 - 1.2:9 - 12;

[0023] The diisocyanate includes one of toluene diisocyanate, isophorone diisocyanate, diphenylmethane diisocyanate, dicyclohexylmethane diisocyanate, hexamethylene diisocyanate, L-lysine diisocyanate;

[0024] The reaction temperature is 95 - 105 °C, and the reaction time is 35 - 40 h.

[0025] In the above technical solution, further, after mixing 2-amino-4-hydroxy-6-methylpyrimidine and the diisocyanate, evacuate to a vacuum at 20 - 90 °C until no liquid bubbles are generated on the liquid surface.

[0026] In the above technical solution, further, in step (d), the molar ratio of the UPy-NCO modifier to the butadiene unit in the hydroxylated styrene-butadiene rubber is 0.5-3:80-120;

[0027] The reaction temperature is 50-60 °C, and the reaction time is 20-30 h;

[0028] The inert gas is one of argon and nitrogen;

[0029] The vacuum drying temperature is 30-50 °C.

[0030] In the above technical solution, further, in step (d), the mass of the dibutyltin dilaurate catalyst is 0.05% of the mass of the hydroxylated styrene-butadiene rubber.

[0031] In the above technical solution, further, in step (e), the conditions for the first-stage mixing are: the mixing time is 10-100 min, the number of thin passes is 2-10 times, preferably 3-6 times;

[0032] The standing time is 12-24 h;

[0033] The conditions for the second-stage mixing are: the mixing time is 10-100 min, and the number of thin passes is 2-10 times.

[0034] In the above technical solution, further, in step (f), the vulcanization conditions are: the temperature is 140-170 °C, preferably 150-160 °C, the pressure is first pre-pressed at 3-10 MPa, preferably 7-9 MPa for 1-30 min, and then increased to 6-15 MPa, preferably 11-13 MPa for 3-100 min.

[0035] On the other hand, the present invention provides an application of a rubber material prepared by the above preparation method as an underwater sound absorption material.

[0036] The beneficial effects of the present invention are:

[0037] In the present invention, the styrene-butadiene rubber is epoxidized and modified by hydroxylation in the chain, then, the UPy-NCO modifier is prepared by reacting UPy with diisocyanate, and finally, the UPy-NCO modifier reacts with the hydroxylated styrene-butadiene rubber to introduce multiple hydrogen bonds into the styrene-butadiene rubber. Compared with the unmodified underwater sound absorption rubber, the introduction of multiple hydrogen bonds provides a new way for the rubber material to dissipate acoustic energy, realizes the good absorption of low-frequency sound waves by the rubber matrix without acoustic fillers, and the highest sound absorption coefficient can reach above 0.7 in the frequency range of 0.4 KHz to 3 KHz, and above 0.9 in the range of 3 kHz to 7.0 kHz. The overall average sound absorption coefficient is increased by 124% compared with the unmodified rubber.

[0038] The present invention can be applied to anechoic tanks, sonar tiles for submarines, sonar domes, etc., and has broad application prospects in the fields of marine scientific research, national defense equipment manufacturing, etc. BRIEF DESCRIPTION OF THE DRAWINGS

[0039] Figure 1 1H NMR spectrum of the rubber material prepared in Example 1;

[0040] Figure 2 Absorption coefficient curve of the rubber material prepared in Example 1. DETAILED DESCRIPTION OF THE INVENTION

[0041] The following non-limiting examples can enable those of ordinary skill in the art to more comprehensively understand the present invention, but do not limit the present invention in any way.

[0042] Unless otherwise specified, the materials used in the embodiments of the present invention can be obtained through commercial channels or prepared by conventional methods well-known to those skilled in the art.

[0043] Example 1

[0044] (a) A mixture of styrene-butadiene rubber (SBR) and 3-chloroperbenzoic acid (m-CPBA) was dissolved in dichloromethane. The feed molar ratio was m-CPBA: butadiene (Bd) unit in styrene-butadiene rubber = 0.1:1. The reaction was carried out at 40 °C for 2 h. The obtained product was concentrated under reduced pressure and purified by precipitation with ethanol multiple times to obtain epoxidized styrene-butadiene rubber (ESBR);

[0045] (b) A mixture of ESBR, deionized water and zirconium tetrachloride (ZrCl4) was dissolved in tetrahydrofuran (THF). The feed molar ratio was epoxy group in epoxidized styrene-butadiene rubber: H2O: ZrCl4 = 1:15:0.5. The reaction was carried out at 25 °C for 3 h. The obtained product was concentrated under reduced pressure and purified by ethanol multiple times to obtain hydroxylated styrene-butadiene rubber (SBR-OH);

[0046] (c) 2-Amino-4-hydroxy-6-methylpyrimidine (UPy) was ground into powder by a mortar, placed in an open glass petri dish, and vacuum dried at 40 °C for 24 h. According to the mass ratio of UPy to diisocyanate of 1:10, UPy and hexamethylene diisocyanate were weighed and placed in a flask. The flask was evacuated at 60 °C until no liquid bubbles were generated on the liquid surface, and the reaction was carried out at 100 °C for 36 h. The product was filtered and washed with n-pentane to remove unreacted hexamethylene diisocyanate, and a white solid powder UPy-NCO modifier was obtained after vacuum drying;

[0047] (d) Dissolve 60 g of SBR-OH in dry toluene, add the solid powder UPy-NCO modifier, and the molar ratio of the UPy-NCO modifier to the Bd unit in SBR-OH is 1:100. After fully stirring and dissolving, add 30 mg of dibutyltin dilaurate catalyst, and react for 24 h under argon protection at 60 °C. After the reaction, precipitate with ethanol, wash, and vacuum dry at 40 °C to obtain styrene-butadiene rubber (SBR-UPy) grafted with UPy groups in the SBR chain;

[0048] (e) Adopt a two-stage mixing method on a two-roll mill. Mix 60 g of SBR-UPy raw rubber, 30 g of carbon black, 0.6 g of stearic acid, and 1.8 g of zinc oxide on the two-roll mill for the first-stage mixing. The mixing time is 20 min, and the number of thin passes is 6 times to obtain the first-stage mixed rubber. Let it stand for 12 h, and then carry out the second-stage mixing on the two-roll mill. Add 1.05 g of sulfur and 0.6 g of accelerator in the first-stage mixing. The mixing time is 10 min, and the number of thin passes is 5 times to obtain the fully mixed rubber;

[0049] (f) Take 4 g of the mixed rubber and test the vulcanization curve in a rotorless vulcanization instrument. The temperature range is 160 °C to determine the vulcanization process. Place 75 g of the mixed rubber into the mold on a flat vulcanizer. Pre-press at a temperature of 160 °C and a pressure of 8 MPa for 1 min, and then increase the pressure to 12 MPa for 3 min to obtain the rubber material.

[0050] Fabrication and testing of acoustic test samples: Bond the rubber material obtained in Example 1 to a circular steel backing, and then test the underwater sound absorption performance using an underwater standing wave tube acoustic system. The test sound wave frequency range is 0.4 - 7.0 kHz. Among them, the sound absorption data in the 0.4 - 4.0 kHz frequency band is measured by the standing wave method, and the 4.0 - 7.0 kHz frequency band is measured by the pulse method.

[0051] Figure 1 This is the proton nuclear magnetic resonance spectrum of the rubber material prepared in this example, showing that multiple hydrogen bonds have been successfully introduced into the styrene-butadiene rubber.

[0052] Example 2

[0053] Prepare and test according to Example 1, with the difference that the molar ratio of the UPy-NCO modifier to the Bd unit in SBR-OH is different. The molar ratio of the UPy-NCO modifier to the Bd unit in SBR-OH is 0.5:100.

[0054] Through testing, the maximum sound absorption coefficient of the sample can reach above 0.5 in the frequency range of 0.4 - 3.0 kHz, and above 0.9 in the range of 3.0 - 7.0 kHz. The overall average sound absorption coefficient is 0.58.

[0055] Example 3

[0056] Preparation and testing were carried out according to Example 1, except that the molar ratio of the UPy-NCO modifier to the Bd unit in SBR-OH was different, and the molar ratio of the UPy-NCO modifier to the Bd unit in SBR-OH was 2:100.

[0057] Through testing, the maximum sound absorption coefficient of the sample can reach above 0.3 in the frequency range of 0.4 - 3.0 kHz, above 0.85 in the range of 3.0 - 7.0 kHz, and the overall average sound absorption coefficient is 0.46.

[0058] Example 4

[0059] Preparation and testing were carried out according to Example 1, except that the molar ratio of the UPy-NCO modifier to the Bd unit in SBR-OH was different, and the molar ratio of the UPy-NCO modifier to the Bd unit in SBR-OH was 3:100.

[0060] Through testing, the maximum sound absorption coefficient of the sample can reach above 0.3 in the frequency range of 0.4 - 3.0 kHz, above 0.7 in the range of 3.0 - 7.0 kHz, and the overall average sound absorption coefficient is 0.44.

[0061] Example 5

[0062] Preparation and testing were carried out according to Example 1, except that the type of diisocyanate was different, and the added diisocyanate was isophorone diisocyanate.

[0063] Through testing, the maximum sound absorption coefficient of the sample can reach above 0.7 in the frequency range of 0.4 - 3.0 kHz, above 0.9 in the range of 3.0 - 7.0 kHz, and the overall average sound absorption coefficient is 0.61.

[0064] Comparative Example 1

[0065] (a) A mixture of styrene-butadiene rubber (SBR) and 3-chloroperbenzoic acid (m-CPBA) was dissolved in dichloromethane, and the feed molar ratio was m-CPBA: butadiene (Bd) unit in styrene-butadiene rubber = 0.1:1. The reaction was carried out at 40 °C for 2 h. The obtained product was concentrated under reduced pressure and purified by precipitation with ethanol multiple times to obtain epoxidized styrene-butadiene rubber (ESBR);

[0066] (b) A mixture of ESBR, deionized water and zirconium tetrachloride (ZrCl4) was dissolved in THF, and the feed molar ratio was epoxy group in epoxidized styrene-butadiene rubber: H2O: ZrCl4 = 1:15:0.5. The reaction was carried out at 25 °C for 3 h. The obtained product was concentrated under reduced pressure and purified with ethanol multiple times to obtain hydroxylated styrene-butadiene rubber (SBR-OH);

[0067] (c) Using a two-stage mixing method on a two-roll mill, 60 g of SBR-OH, 30 g of carbon black, 0.6 g of stearic acid, and 1.8 g of zinc oxide were subjected to the first-stage mixing on a two-roll mill for 20 min with 6 passes of thin-slicing to obtain the first-stage mixed rubber. After standing for 12 h, the second-stage mixing was carried out on a two-roll mill. 1.05 g of sulfur and 0.6 g of accelerator were added during the first-stage mixing, and the mixing time was 10 min with 5 passes of thin-slicing to obtain the completely mixed rubber.

[0068] (d) 4 g of the mixed rubber was taken to test the vulcanization curve in a rotorless vulcanization instrument at a temperature range of 160 °C to determine the vulcanization process. 75 g of the mixed rubber was placed into a mold on a flat vulcanizing machine and pre-pressed at 160 °C and 8 MPa for 1 min, then the pressure was increased to 12 MPa for 3 min to obtain the rubber material.

[0069] Through testing, the maximum sound absorption coefficient of the sample can reach above 0.3 in the frequency range of 0.4 - 3.0 kHz, above 0.6 in the range of 3.0 - 7.0 kHz, and the overall average sound absorption coefficient is 0.31.

[0070] Comparative Example 2

[0071] (a) Using a two-stage mixing method on a two-roll mill, 60 g of styrene-butadiene rubber (SBR), 30 g of carbon black, 0.6 g of stearic acid, and 1.8 g of zinc oxide were subjected to the first-stage mixing on a two-roll mill for 20 min with 6 passes of thin-slicing to obtain the first-stage mixed rubber. After standing for 12 h, the second-stage mixing was carried out on a two-roll mill. 1.05 g of sulfur and 0.6 g of accelerator were added during the first-stage mixing, and the mixing time was 10 min with 5 passes of thin-slicing to obtain the completely mixed rubber.

[0072] (b) 4 g of the mixed rubber was taken to test the vulcanization curve in a rotorless vulcanization instrument at a temperature range of 160 °C to determine the vulcanization process. 75 g of the mixed rubber was placed into a mold on a flat vulcanizing machine and pre-pressed at 160 °C and 8 MPa for 1 min, then the pressure was increased to 12 MPa for 3 min to obtain the rubber material.

[0073] Through testing, the maximum sound absorption coefficient of the sample reaches above 0.2 in the frequency range of 0.4 - 3.0 kHz, above 0.6 in the range of 3.0 - 7.0 kHz, and the overall average sound absorption coefficient is 0.29, with a very low sound absorption coefficient.

[0074] Multiple hydrogen bonds were successfully introduced into styrene-butadiene rubber in Example 1. The test results showed that the maximum sound absorption coefficient could reach above 0.7 in the frequency range of 0.4 - 3.0 kHz, and above 0.9 in the range of 3.0 - 7.0 kHz. The overall average sound absorption coefficient increased by 109% compared with Comparative Example 1 and by 124% compared with Comparative Example 2. This indicates that the multiple hydrogen bond effect enhances the underwater low-frequency sound absorption performance of styrene-butadiene rubber. The main reason is the relatively low bond energy of hydrogen bonds. When the molecular chain is affected by sound waves, the hydrogen bonds break preferentially to dissipate part of the sound energy, and at the same time, the side chains formed after the hydrogen bond breakage also increase the sound energy dissipation.

[0075] Thus, it can be seen that the sound absorption performance of the styrene-butadiene rubber material after introducing multiple hydrogen bonds has been significantly improved, especially in the low-frequency region.

[0076] The embodiments of the present invention have been described in detail above. However, the present invention is not limited to the specific details in the above embodiments. Within the scope of the technical concept of the present invention, various simple modifications can be made to the technical solutions of the present invention, and these simple modifications all belong to the protection scope of the present invention.

[0077] In addition, any combination can be made between various different embodiments of the present invention as long as it does not violate the idea of the present invention, and it should also be regarded as the content disclosed by the present invention.

Claims

1. A preparation method of an underwater low-frequency sound-absorbing rubber material based on multiple hydrogen bond interactions, characterized in that, The method comprises the following steps: (a) dissolving a mixture of styrene-butadiene rubber and peroxyacid in dichloromethane to react, and purifying the obtained product through ethanol precipitation to obtain epoxidized styrene-butadiene rubber; (b) dissolving the mixture of the epoxidized styrene-butadiene rubber obtained in step (a), deionized water and a Lewis acid catalyst in tetrahydrofuran for reaction, and purifying the obtained product by ethanol precipitation to obtain hydroxylated styrene-butadiene rubber; (c) adding the vacuum-dried 2-amino-4-hydroxy-6-methylpyrimidine powder to dry diisocyanate for reaction, filtering and washing the product with n-pentane, and then vacuum-drying to obtain a UPy-NCO modifier; (d) dissolving the hydroxylated styrene-butadiene rubber obtained in step (b) in dry toluene, adding the UPy-NCO modifier obtained in step (c), stirring thoroughly to dissolve, and then adding dibutyltin dilaurate as a catalyst, reacting under inert gas protection, and after completion of the reaction, precipitating with ethanol, washing, and then vacuum drying to obtain styrene-butadiene rubber grafted with UPy groups; (e) using a two-stage mixing method on a two-roll mill, firstly mixing the UPy-grafted styrene-butadiene rubber obtained in step (d) with carbon black, stearic acid, and zinc oxide in a first stage to obtain a first-stage rubber mix, and then allowing the first-stage rubber mix to stand. Subsequently, sulfur and an accelerator are added to the first-stage rubber mix, and mixing is performed in a second stage to obtain a rubber mix; (f) vulcanizing the rubber mix to obtain the rubber material.

2. The preparation method according to claim 1, characterized in that, In step (a), the molar ratio of the peroxy acid to the butadiene unit in the styrene-butadiene rubber is selected from 0.1 to 0.15:1; The reaction temperature is 30-40°C and the reaction time is 1.5-2.5h; The peroxy acid includes one of peroxyformic acid, peroxyacetic acid, peroxypropionic acid, peroxymaleic acid, peroxybenzoic acid, 3-chloroperoxybenzoic acid, peroxytrifluoroacetic acid, m-nitroperoxybenzoic acid, and p-nitroperoxybenzoic acid.

3. The preparation method according to claim 1, characterized in that In step (b), the molar ratio of epoxy group in the epoxidized styrene-butadiene rubber, deionized water, and Lewis acid catalyst is 0.8-1.2:13-17:0.4-0.6; The reaction temperature is 20-30°C and the reaction time is 2.5-3.5h; The Lewis acid catalyst includes one of boron trifluoride, aluminum trichloride, titanium trichloride, zirconium trichloride, zirconium tetrachloride, and chromium trichloride.

4. The preparation method according to claim 1, wherein, In step (c), the mass ratio of 2-amino-4-hydroxy-6-methylpyrimidine to diisocyanate is 0.8-1.2:9-12; The diisocyanate includes one of toluene diisocyanate, isophorone diisocyanate, diphenylmethane diisocyanate, dicyclohexylmethane diisocyanate, hexamethylene diisocyanate, and L-lysine diisocyanate; The reaction temperature is 95-105° C., and the reaction time is 35-40 hours.

5. The preparation method according to claim 1, characterized in that In step (d), the molar ratio of the UPy-NCO modifier to the butadiene unit in the hydroxylated styrene-butadiene rubber is 0.5-3:80-120; The reaction temperature is 50-60°C and the reaction time is 20-30h; The inert gas is one of argon and nitrogen; The vacuum drying temperature is 30-50°C.

6. The preparation method according to claim 1, wherein, In step (d), the mass of the dibutyltin dilaurate catalyst is 0.05% of the mass of the hydroxylated styrene-butadiene rubber.

7. The preparation method according to claim 1, wherein In step (e), the conditions for the first-stage mixing are: the mixing time is 10 - 100 min, and the number of thin passes is 2 - 10 times; The standing time is 12 - 24 h; The conditions for the second-stage mixing are: the mixing time is 10 - 100 min, and the number of thin passes is 2 - 10 times.

8. The preparation method according to claim 1, characterized in that In step (f), the vulcanization conditions are: the temperature is 140 - 170 °C, the pressure is first pre-pressed at 3 - 10 MPa for 1 - 30 min, then increased to 6 - 15 MPa for 3 - 100 min.

9. Application of a rubber material prepared by the preparation method according to any one of claims 1 - 8 as an underwater sound-absorbing material.

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