A foam stabilizer capable of improving surface defects of polyurethane foam, and a preparation method and application thereof

Abstract

This invention discloses a foam leveling agent that can improve surface defects in polyurethane foam, its preparation method, and its application. The foam leveling agent has the structural expression of Formula I, where m and n represent the degree of polymerization of each chain segment; specifically, m = 15-40, n = 1-20; or m = 60-90, n = 15-40. R has the structural expression of Formula II, where x and y represent the degree of polymerization of each unit, specifically x = 2-50, y = 2-50. This invention, by designing the chain segment ratio in the polyether-modified silicone oil foam leveling agent, can maintain the foaming system in a microphase compatible state, maximizing its compatibility threshold with the foaming composition, thereby significantly improving surface defects in polyurethane foam while maintaining certain foam strength and thermal conductivity.

Description

Technical Field

[0001] This invention relates to a polyurethane foam leveling agent, and more particularly to a leveling agent that can improve surface defects of polyurethane foam, its preparation method, and its application. Background Technology

[0002] Polyurethane is an important synthetic material widely used in various products, such as thermal insulation materials for buildings, automobiles, and home appliances. However, during the foaming process of polyurethane, surface defects such as pores and depressions often occur due to the formation and growth of bubbles, which can affect the appearance and performance of the product.

[0003] In the building materials industry, surface defects in rigid polyurethane foam can reduce the product's insulation performance and may cause structural problems. Furthermore, in decorative building components, surface defects can also affect the overall aesthetics. In the home appliance industry, with the increasing popularity of high-end, non-built-in refrigerators, the market has increasingly higher requirements for the surface defects of polyurethane foam. Lower surface defects allow for thinner and lighter internal panels in refrigerators, and due to insulation requirements, the thermal conductivity of the polyurethane foam cannot be significantly reduced while improving surface defects.

[0004] To address this issue, researchers typically add foam stabilizers during the foaming process to control bubble formation and growth, thereby reducing surface defects. However, this still falls short of meeting the application requirements of specific fields.

[0005] Patent CN110317344A discloses a composition for rigid polyurethane foam. The silicone surfactant, prepared by introducing a nonionic surfactant and a bio-ester plasticizer, improves the thermal conductivity of rigid polyurethane foam, but fails to address the surface defects of the polyurethane foam. Patent CN109096494B describes a silicone surfactant for rigid polyurethane foam and its preparation method. This solves the compatibility problem caused by using vegetable oil-based polyols instead of petroleum-based polyols in the production of rigid polyurethane foam, improving the surface defects of the foam. However, the overall strength and thermal conductivity of the foam are significantly lacking.

[0006] Therefore, a new solution is needed to further improve the problem of numerous surface defects in polyurethane foam while maintaining a certain level of foam strength and thermal conductivity. Summary of the Invention

[0007] To address the above technical problems, this invention proposes a foam leveling agent that can improve surface defects in polyurethane foam, its preparation method, and its application.

[0008] To achieve the above objectives, the technical solution adopted by the present invention is as follows:

[0009] As a first aspect of the present invention, a foam leveling agent that can improve surface defects of polyurethane foam is provided, having the following structural expression: Formula I:

[0010]

[0011] In Formula I, m and n represent the degree of polymerization of each chain segment; where m = 15-40, preferably 25-35, for example, 20, 25, 30, 35, etc., and n = 1-20, preferably 5-10, for example, 2, 3, 5, 8, 10, 12, 15, 17, 19, etc.; or m = 60-90, preferably 75-85, for example, 65, 70, 75, 80, etc., and n = 15-40, preferably 20-30, for example, 20, 25, 30, 35, etc.

[0012] R has the following structure expression:

[0013]

[0014] In Formula II, x and y represent the degree of aggregation of each unit. x = 2-50, preferably 9-14, for example, 5, 10, 15, 20, 25, 30, 35, 40, 45, etc., and y = 2-50, preferably 3-8, for example, 5, 10, 15, 20, 25, 30, 35, 40, 45, etc.

[0015] This invention, by designing the chain segment ratio in the polyether-modified silicone oil foam stabilizer, can maintain the foaming system in a microphase compatible state, maximizing its compatibility threshold with the foaming composition, thereby significantly improving the surface defects of polyurethane foam while maintaining a certain level of foam strength and thermal conductivity. It has outstanding applications in building materials / home appliances and other fields where high requirements are placed on the appearance of the foam surface.

[0016] As a second aspect of the present invention, a method for preparing a foam stabilizer that can improve surface defects of polyurethane foam is also provided, comprising the following steps:

[0017] A. Using a strong acid as a catalyst, octamethylcyclotetrasiloxane is mixed and reacted with polydimethylhydrosiloxane and hexamethyldisiloxane to obtain a side-containing hydrogen silicone oil.

[0018] B. Using a platinum complex as a catalyst, hydrogen-containing silicone oil and allyl polyether undergo a hydrosilylation reaction to obtain the foam stabilizer.

[0019] The mass ratio of octamethylcyclotetrasiloxane to polydimethylhydrosiloxane and hexamethyldisiloxane is (4-14):1:(0.5-2), preferably (6-10):1:(0.8-1.2); or, the mass ratio of octamethylcyclotetrasiloxane to polydimethylhydrosiloxane and hexamethyldisiloxane is (6-24):1:(0.3-2), preferably (16-20):1:(0.4-0.8);

[0020] The molar ratio of EO to PO blocks in the allyl polyether is (2-50):(2-50), preferably (9-14):(3-8); preferably, the number average molecular weight of the allyl polyether is 800-1400, for example, it can be 900, 950, 1000, 1050, 1100, 1150, 1200, 1250, 1300, 1350, etc.

[0021] As some examples of the preparation method in this invention, the strong acid is one or more of concentrated hydrochloric acid, concentrated sulfuric acid, phosphoric acid, and trifluoromethanesulfonic acid;

[0022] Preferably, the amount of the strong acid used is 500-3000 ppm of the total mass of octamethylcyclotetrasiloxane, polydimethylhydrosiloxane, and hexamethyldisiloxane, more preferably 1000-2000 ppm.

[0023] As some examples of the preparation method in this invention, the reaction temperature in step A is 30-100℃, preferably 50-70℃, and the reaction time is 2-10h, preferably 4-6h.

[0024] Preferably, after the reaction in step A is completed, a neutralizing agent is added to the system to neutralize the strong acid; the neutralizing agent is selected from one or more of calcium carbonate, sodium bicarbonate, sodium carbonate, and calcium bicarbonate; preferably calcium carbonate, and the amount used is 10-30 times the mass of the strong acid.

[0025] As some examples of the preparation method in this invention, the mass ratio of the side-containing hydrogen silicone oil to the allyl polyether is 1:(1.5-2.5), preferably 1:(1.8-2.1). The viscosity of the side-containing hydrogen silicone oil is 30-60 cP or 80-120 cP.

[0026] As some examples of the preparation method in this invention, the platinum complex is selected from one or more of divinyltetramethyldisiloxane platinum, tetravinyltetramethyltetrasiloxane platinum, and platinum hexachloride hexahydrate, preferably divinyltetramethyldisiloxane platinum and / or platinum hexachloride hexahydrate.

[0027] Preferably, the amount of the platinum complex, based on the content of metallic platinum, is 1-20 ppm of the total mass of the hydrogen-containing silicone oil and allyl polyether, more preferably 2-5 ppm.

[0028] As some examples of the preparation method in this invention, the reaction temperature in step B is 30-120℃, preferably 80-100℃, and the reaction time is 15-120min, preferably 30-60min.

[0029] In the preparation method provided by the present invention, by adjusting the raw material ratio within a certain range, polyether-modified silicone oil with block content meeting certain requirements can be obtained. When used as a foam stabilizer, it has a significant effect on improving the surface defects of polyurethane foam, especially rigid foam. It also has high foam stabilizing activity, good compatibility, and high emulsification ability, and has high industrial value.

[0030] As a third aspect of the invention, the application of a foam leveling agent for improving surface defects of polyurethane foam as described above, or a foam leveling agent for improving surface defects of polyurethane foam prepared by the method described above, in the field of polyurethane foaming, especially in the preparation of polyurethane foam insulation materials for building materials / home appliances with improved surface defects.

[0031] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0032] The polyether-modified silicone oil foam stabilizer provided by this invention exhibits strong foam stabilizing ability, good compatibility, and high emulsifying ability in polyurethane foaming systems. It significantly improves surface defects in foams and can be used in polyurethane foamed home appliances and building materials, better meeting market demands. Furthermore, the preparation method provided by this invention is simple and easy to operate, suitable for large-scale industrial production. Detailed Implementation

[0033] The present invention will be further illustrated below with specific embodiments. These embodiments are merely illustrative and do not limit the scope of the invention.

[0034] Unless otherwise specified, the raw materials and reagents used in the following embodiments of the present invention can be obtained from general commercial sources. The main raw material information is as follows:

[0035] Octamethylcyclotetrasiloxane: Dow Corning

[0036] Hexamethyldisiloxane: Bengbu Hengyu

[0037] Polydimethylsiloxane: Dow Corning DC1107, viscosity 20 cP

[0038] Allyl polyether ZS-950: Nanjing Zhongrui, viscosity: 80 cP

[0039] Allyl polyether ZS-1000: Nanjing Zhongrui, viscosity: 100 cP

[0040] Allyl polyether ZS-1300: Nanjing Zhongrui, viscosity: 110 cP

[0041] Platinum Complex A: Divinyltetramethyldisiloxaneplatinum, Yunnan Guizhou Research Institute

[0042] Platinum complex B: Platinum hexachloride hexahydrate, Yunnan Guizhou Research Institute

[0043]

Example 1

[0044] In a reactor equipped with a stirrer and a thermometer, 60 parts by weight of octamethylcyclotetrasiloxane, 10 parts by weight of polydimethylhydrosiloxane, 8 parts by weight of hexamethyldisiloxane, and 0.08 parts by weight of trifluoromethanesulfonic acid were added sequentially. The mixture was allowed to equilibrate at 60°C for 5 hours. After the reaction was complete, 0.8 parts by weight of calcium carbonate were added to neutralize the trifluoromethanesulfonic acid in the system. The mixture was then filtered to obtain a clear, transparent, oily liquid, namely, side-containing hydrosilicone oil (I). The viscosity of side-containing hydrosilicone oil (I) was measured to be 38 cp, the volatile matter content was <13%, and the Si-H content was 1883 ppm.

[0045] 85 parts of side-containing hydrogen silicone oil (Ⅰ) and 150 parts of allyl polyether ZS-950 were added sequentially to a reactor equipped with mechanical stirring and nitrogen pipeline. Under the action of 5 ppm platinum complex A relative to the total mass of raw materials, the reaction temperature was controlled at 100℃ to carry out a hydrosilylation reaction. The reaction was carried out for 1 hour to obtain polyether modified silicone oil (Ⅰ) (m:n=26:5,x:y=9:5).

[0046]

Example 2

[0047] In a reactor equipped with a stirrer and a thermometer, 80 parts by weight of octamethylcyclotetrasiloxane, 10 parts by weight of polydimethylhydrosiloxane, 10 parts by weight of hexamethyldisiloxane, and 0.2 parts by weight of trifluoromethanesulfonic acid were added sequentially. The mixture was allowed to equilibrate at 60°C for 4 hours. After the reaction was complete, 4 parts by weight of calcium carbonate were added to neutralize the trifluoromethanesulfonic acid in the system, yielding side-containing hydrogen silicone oil (II). The viscosity of side-containing hydrogen silicone oil (II) was measured to be 61 cp, the volatile matter content was <13%, and the Si-H content was 2036 ppm.

[0048] 95 parts of side-containing hydrogen silicone oil (II) and 200 parts of allyl polyether ZS-1000 were added sequentially to a reactor equipped with mechanical stirring and nitrogen pipeline. Under the action of platinum complex A at 7 ppm relative to the total mass of raw materials, the reaction temperature was controlled at 90℃ to carry out a hydrosilylation reaction for 1.5 h to obtain polyether modified silicone oil (II) (m:n=30:10, x:y=12:8).

[0049]

Example 3

[0050] In a reactor equipped with a stirrer and a thermometer, 100 parts by weight of octamethylcyclotetrasiloxane, 10 parts by weight of polydimethylhydrosiloxane, 12 parts by weight of hexamethyldisiloxane, and 0.15 parts by weight of trifluoromethanesulfonic acid were added sequentially, and the mixture was allowed to equilibrate at 60°C for 4 hours. After the reaction was complete, 1.5 parts by weight of calcium carbonate were added to neutralize the trifluoromethanesulfonic acid in the system, yielding end-side hydrogen-containing silicone oil (III). The viscosity of end-side hydrogen-containing silicone oil (III) was determined to be 45 cp, with a volatile content of <13% and a Si-H content of 1994 ppm.

[0051] 100 parts of hydrogen-containing silicone oil (III) and 190 parts of allyl polyether ZS-1000 were added sequentially to a reactor equipped with mechanical stirring and nitrogen pipeline. Under the action of 10 ppm platinum complex B relative to the total mass of raw materials, the reaction temperature was controlled at 90℃ to carry out a hydrosilylation reaction. The reaction was carried out for 1 hour to obtain polyether modified silicone oil (III) (m:n=28:7,x:y=14:5).

[0052]

Example 4

[0053] In a reactor equipped with a stirrer and a thermometer, 160 parts by weight of octamethylcyclotetrasiloxane, 10 parts by weight of polydimethylhydrosiloxane, 4 parts by weight of hexamethyldisiloxane, and 0.2 parts by weight of trifluoromethanesulfonic acid were added sequentially. The mixture was allowed to equilibrate at 60°C for 4 hours. After the reaction was complete, 4 parts by weight of calcium carbonate were added to neutralize the trifluoromethanesulfonic acid in the system, yielding end-side hydrogen-containing silicone oil (Ⅳ). The viscosity of end-side hydrogen-containing silicone oil (Ⅳ) was measured to be 95 cp, the volatile matter content was <13%, and the Si-H content was 1753 ppm.

[0054] 100 parts of side-containing hydrogen silicone oil (Ⅳ) and 200 parts of allyl polyether ZS-950 were added sequentially to a reactor equipped with mechanical stirring and nitrogen pipeline. Under the action of 5 ppm platinum complex B relative to the total mass of raw materials, the reaction temperature was controlled at 100℃ to carry out a hydrosilylation reaction. The reaction was carried out for 1 hour to obtain polyether modified silicone oil (Ⅳ) (m:n=75:20,x:y=9:5).

[0055]

Example 5

[0056] In a reactor equipped with a stirrer and a thermometer, 180 parts by weight of octamethylcyclotetrasiloxane, 10 parts by weight of polydimethylhydrosiloxane, 6 parts by weight of hexamethyldisiloxane, and 0.3 parts by weight of trifluoromethanesulfonic acid were added sequentially. The mixture was allowed to equilibrate at 60°C for 4 hours. After the reaction was complete, 6 parts by weight of calcium carbonate were added to neutralize the trifluoromethanesulfonic acid in the system, yielding end-side hydrogen-containing silicone oil (V). The viscosity of end-side hydrogen-containing silicone oil (V) was measured to be 112 cp, with a volatile content of <13% and a Si-H content of 2235 ppm.

[0057] 90 parts of side-containing hydrogen silicone oil (V) and 210 parts of allyl polyether ZS-1200 were added sequentially to a reactor equipped with mechanical stirring and nitrogen pipeline. Under the action of 5 ppm platinum complex B relative to the total mass of raw materials, the reaction temperature was controlled at 100℃ to carry out a hydrosilylation reaction. The reaction was carried out for 1 hour to obtain polyether modified silicone oil (V) (m:n=85:30, x:y=12:8).

[0058]

Example 6

[0059] In a reactor equipped with a stirrer and a thermometer, 200 parts by weight of octamethylcyclotetrasiloxane, 10 parts by weight of polydimethylhydrosiloxane, 8 parts by weight of hexamethyldisiloxane, and 0.3 parts by weight of trifluoromethanesulfonic acid were added sequentially. The mixture was allowed to equilibrate at 60°C for 5 hours. After the reaction was complete, 6 parts by weight of calcium carbonate were added to neutralize the trifluoromethanesulfonic acid in the system, yielding end-side hydrogen-containing silicone oil (VI). The viscosity of end-side hydrogen-containing silicone oil (VI) was measured to be 104 cp, with a volatile content of <13% and a Si-H content of 2058 ppm.

[0060] 85 parts of side-containing hydrogen silicone oil (VI) and 175 parts of allyl polyether ZS-1000 were added sequentially to a reactor equipped with mechanical stirring and nitrogen pipeline. Under the action of 5 ppm platinum complex A relative to the total mass of raw materials, the reaction temperature was controlled at 100℃ to carry out a hydrosilylation reaction. The reaction was carried out for 1 hour to obtain polyether modified silicone oil (VI) (m:n=80:26,x:y=14:5).

[0061] Comparative Example 1

[0062] Following the basic principle of Example 1, 50 parts by weight of octamethylcyclotetrasiloxane, 10 parts by weight of polydimethylhydrosiloxane, 12 parts by weight of hexamethyldisiloxane, and 0.08 parts by weight of trifluoromethanesulfonic acid were added sequentially to a reactor equipped with a stirrer and a thermometer. The mixture was then allowed to equilibrate at 60°C for 5 hours. After the reaction was complete, 0.8 parts by weight of calcium carbonate were added to neutralize the trifluoromethanesulfonic acid in the system. The mixture was then filtered to obtain a clear, transparent, oily liquid, namely, side-containing hydrosilicone oil (x). The viscosity of side-containing hydrosilicone oil (x) was measured to be 25 cp, the volatile matter content was <13%, and the Si-H content was 1752 ppm.

[0063] 90 parts of hydrogen-containing silicone oil (x) and 200 parts of allyl polyether ZS-950 were added sequentially to a reactor equipped with mechanical stirring and nitrogen pipeline. Under the action of 5 ppm platinum complex A relative to the total mass of raw materials, the reaction temperature was controlled at 100℃ to carry out a hydrosilylation reaction. The reaction was carried out for 1 hour to obtain polyether modified silicone oil (X) (m:n=18:4, x:y=9:5).

[0064] Comparative Example 2

[0065] Following the basic principle of Example 6, 230 parts by weight of octamethylcyclotetrasiloxane, 10 parts by weight of polydimethylhydrosiloxane, 8 parts by weight of hexamethyldisiloxane, and 0.3 parts by weight of trifluoromethanesulfonic acid were added sequentially to a reactor equipped with a stirrer and a thermometer. The mixture was then allowed to equilibrate at 60°C for 5 hours. After the reaction was complete, 6 parts by weight of calcium carbonate were added to neutralize the trifluoromethanesulfonic acid in the system, yielding end-side hydrogen-containing silicone oil (y). The viscosity of the end-side hydrogen-containing silicone oil (y) was measured to be 120 cp, with a volatile content of <13% and a Si-H content of 2227 ppm.

[0066] 85 parts of side-containing hydrogen silicone oil (y) and 195 parts of allyl polyether ZS-1000 were added sequentially to a reactor equipped with mechanical stirring and nitrogen pipeline. Under the action of 5 ppm platinum complex A relative to the total mass of raw materials, the reaction temperature was controlled at 100℃ to carry out a hydrosilylation reaction. The reaction was carried out for 1 hour to obtain polyether modified silicone oil (Y) (m:n=95:32, x:y=14:5).

[0067] <Stiff Foaming Methods and Testing Methods>

[0068] Materials preparation:

[0069] 90g polyether polyol (Wanhua Chemical, F3156D)

[0070] 2g PC-8 (N,N-dimethylcyclohexylamine, Aladdin)

[0071] 1.5g T12 (Dibutyltin dilaurate, Aladdin)

[0072] 1g polyether modified silicone oil

[0073] 0.5g water

[0074] 14g cyclopentane (Aladdin)

[0075] 130g PM-200 (Wanhua Chemical)

[0076] Mix all the above materials except PM-200 evenly (3000r / min, 30s), stir thoroughly, then add PM-200 and continue stirring (3000r / min, 10s). Finally, pour the mixture into a fixed mold (60cm*40cm*20cm) to allow it to foam and grow on its own. After foaming, let it stand and cool to room temperature before taking it out for subsequent testing.

[0077] The main testing methods involved in this invention include:

[0078] 1. Foam density testing shall be conducted in accordance with GB / T 10807-2006B;

[0079] 2. Surface defect test: After foaming with the above formula in a stainless steel mold with fixed dimensions of 60cm*40cm*20cm, count the number of defects with a diameter of more than 2cm*2cm on the front and back of the foam respectively, and take the average value.

[0080] 3. Cyclopentane compatibility: After mixing all raw materials except TDI and cyclopentane in the above formula evenly, gradually add cyclopentane (1g is 1 part). When the system becomes slightly turbid, the number of parts of cyclopentane added at this time is the cyclopentane compatibility.

[0081] 4. Thermal conductivity: GB-T 17794-2021

[0082] 4. Compressive strength: GB-T 6669-2008

[0083] 5. Liquidity: GB-T 40244-2021

[0084] The foam properties prepared by this invention using different polyether-modified silicone oils are shown in Tables 1 and 2.

[0085] Table 1

[0086]

[0087]

[0088] Table 2

[0089] Ⅳ Ⅴ Ⅵ Y <![CDATA[Foam density (kg / m 3 )]]> 26.35 26.88 27.15 26.95 Surface defect count 12.65 12.95 13.51 15.52 Cyclopentane compatibility 25 24 24 20 <![CDATA[Thermal conductivity (mW.K -1 .m -1 )]]> 19.55 19.51 19.48 19.41 Compressive strength / kPa 183 182 182 181 Liquidity / s 24 / 33 / 43 / 55 24 / 34 / 42 / 55 24 / 35 / 44 / 55 24 / 33 / 42 / 54

[0090] The above description is only a preferred embodiment of the present invention. It should be noted that those skilled in the art can make several improvements and additions without departing from the method of the present invention, and these improvements and additions should also be considered within the scope of protection of the present invention.

Claims

1. A foam leveling agent for improving surface defects in polyurethane foam, characterized in that, It has the following structure expression: Equation I In Formula I, m and n represent the degree of polymerization of each chain segment; where m = 25-40, n = 5-20; or m = 60-90, n = 15-40; R has the following structure expression: Formula II In Equation II, x and y represent the degree of aggregation of each unit, where x = 2-50 and y = 2-50.

2. A foam leveling agent according to claim 1 for improving surface defects in polyurethane foam, characterized in that, In Formula I, m = 25-35, n = 5-10; or m = 75-85, n = 20-30.

3. A foam leveling agent according to claim 1 for improving surface defects in polyurethane foam, characterized in that, In Equation II, x and y represent the degree of aggregation of each unit, where x = 9-14 and y = 3-8.

4. A method for preparing a foam stabilizer according to claim 1, characterized in that, Includes the following steps: A. Using a strong acid as a catalyst, octamethylcyclotetrasiloxane is mixed and reacted with polydimethylhydrosiloxane and hexamethyldisiloxane to obtain a side-containing hydrogen silicone oil. B. Using a platinum complex as a catalyst, hydrogen-containing silicone oil and allyl polyether undergo a hydrosilylation reaction to obtain the foam stabilizer. The mass ratio of octamethylcyclotetrasiloxane to polydimethylhydrosiloxane and hexamethyldisiloxane is (4-14):1:(0.5-2); or, the mass ratio of octamethylcyclotetrasiloxane to polydimethylhydrosiloxane and hexamethyldisiloxane is (6-24):1:(0.3-2). The molar ratio of EO and PO blocks in the allyl polyether is (2-50):(2-50).

5. The method for preparing a foam stabilizer to improve surface defects of polyurethane foam according to claim 4, characterized in that, The mass ratio of octamethylcyclotetrasiloxane to polydimethylhydrosiloxane and hexamethyldisiloxane is (6-10):1:(0.8-1.2); or the mass ratio of octamethylcyclotetrasiloxane to polydimethylhydrosiloxane and hexamethyldisiloxane is (16-20):1:(0.4-0.8).

6. The method for preparing a foam stabilizer to improve surface defects of polyurethane foam according to claim 4, characterized in that, The molar ratio of EO and PO blocks in the allyl polyether is (9-14):(3-8).

7. The method for preparing a foam stabilizer to improve surface defects of polyurethane foam according to claim 4, characterized in that, The number average molecular weight of the allyl polyether is 800-1400.

8. The method for preparing a foam leveling agent that can improve surface defects of polyurethane foam according to claim 4, characterized in that, The strong acid is one or more of concentrated hydrochloric acid, concentrated sulfuric acid, phosphoric acid, and trifluoromethanesulfonic acid.

9. The method for preparing a foam leveling agent that can improve surface defects of polyurethane foam according to claim 8, characterized in that, The amount of the strong acid used is 500-3000 ppm of the total mass of octamethylcyclotetrasiloxane, polydimethylhydrosiloxane, and hexamethyldisiloxane.

10. The method for preparing a foam stabilizer for improving surface defects of polyurethane foam according to claim 9, characterized in that, The amount of the strong acid used is 1000-2000 ppm of the total mass of octamethylcyclotetrasiloxane, polydimethylhydrosiloxane, and hexamethyldisiloxane.

11. The method for preparing a foam stabilizer for improving surface defects of polyurethane foam according to any one of claims 4-10, characterized in that, In step A, the reaction temperature is 30-100℃ and the reaction time is 2-10h.

12. The method for preparing a foam stabilizer for improving surface defects of polyurethane foam according to claim 11, characterized in that, In step A, the reaction temperature is 50-70℃ and the reaction time is 4-6 hours.

13. The method for preparing a foam stabilizer for improving surface defects of polyurethane foam according to any one of claims 4-10, characterized in that, The mass ratio of the hydrogen-containing silicone oil to the allyl polyether is 1:(1.5-2.5).

14. The method for preparing a foam stabilizer for improving surface defects of polyurethane foam according to claim 13, characterized in that, The mass ratio of the hydrogen-containing silicone oil to the allyl polyether is 1:(1.8-2.1).

15. The method for preparing a foam stabilizer for improving surface defects of polyurethane foam according to any one of claims 4-10, characterized in that, The platinum complex is selected from one or more of divinyltetramethyldisiloxane platinum, tetravinyltetramethyltetrasiloxane platinum, and platinum hexahydrate.

16. The method for preparing a foam stabilizer for improving surface defects of polyurethane foam according to claim 15, characterized in that, The platinum complex is selected from divinyltetramethyldisiloxane platinum and / or platinum hexachloride hexahydrate.

17. The method for preparing a foam stabilizer for improving surface defects of polyurethane foam according to claim 15, characterized in that, The amount of the platinum complex, based on the content of metallic platinum, is 1-20 ppm of the total mass of the hydrogen-containing silicone oil and allyl polyether.

18. The method for preparing a foam stabilizer for improving surface defects of polyurethane foam according to claim 17, characterized in that, The amount of the platinum complex, based on the content of metallic platinum, is 2-5 ppm of the total mass of the hydrogen-containing silicone oil and allyl polyether.

19. A method for preparing a foam stabilizer for improving surface defects of polyurethane foam according to any one of claims 4-10, characterized in that, In step B, the reaction temperature is 30-120℃ and the reaction time is 15-120 min.

20. The method for preparing a foam stabilizer for improving surface defects of polyurethane foam according to claim 19, characterized in that, In step B, the reaction temperature is 80-100℃ and the reaction time is 30-60 min.

21. The application of a foam leveling agent for improving surface defects of polyurethane foam as described in any one of claims 1-3, or a foam leveling agent for improving surface defects of polyurethane foam prepared by the method described in any one of claims 4-20, in the field of polyurethane foaming.

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