Foam stabilizer capable of improving surface defects of polyurethane foam as well as preparation method and application of foam stabilizer

Abstract

The invention discloses a foam stabilizer capable of improving surface defects of polyurethane foam as well as a preparation method and application of the foam stabilizer. The foam stabilizer has a structural expression of a formula I. In the formula I, m and n represent the polymerization degree of each chain link; wherein m is equal to 15-40, and n is equal to 1-20; or m is equal to 60-90, and n is equal to 15-40; r has a structural expression as shown in a formula II, in the formula II, x and y represent the degree of polymerization of each unit, x is equal to 2-50, and y is equal to 2-50; by designing the proportion of chain segments in the polyether modified silicone oil foam stabilizer, a foaming system can be maintained in a micro-phase compatible state, and the compatibility threshold value between the foaming system and a foaming combined material is increased to the greatest extent, so that the surface defects of polyurethane foam are remarkably improved, and meanwhile, certain foam strength and thermal conductivity are maintained. # imgabs0 #

Description

Technical Field

[0001] The invention relates to a polyurethane foam leveling agent, in particular to a leveling agent capable of improving surface defects of polyurethane foam and a preparation method and application thereof. Background Art

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

[0003] In the field of building materials, surface defects of polyurethane rigid foam will reduce the thermal insulation effect of the product and may cause structural problems; and in decorative building components, defects on the foam surface will also affect the overall appearance. In the field of home appliances, with the gradual promotion of high-end zero-embedded refrigerators, the market has higher and higher requirements for surface defects of polyurethane foam. Lower surface defects can make the internal panels of refrigerators thinner and lighter. Due to the need for thermal insulation, the thermal conductivity of polyurethane foam cannot be significantly reduced while improving surface defects.

[0004] To solve this problem, researchers usually add foaming agents during the foaming process to control the formation and growth of bubbles, thereby reducing surface defects, but this still cannot meet the application requirements in special fields.

[0005] Patent CN110317344A provides a composition for rigid polyurethane foam. The organic silicon surfactant prepared by introducing nonionic surfactant and bio-ester plasticizer can improve the thermal conductivity of rigid polyurethane foam, but fails to solve the problem of surface defects of polyurethane foam. Patent CN109096494B describes an organic silicon surfactant for rigid polyurethane foam and its preparation method, which solves the compatibility problem caused by using vegetable oil polyols instead of petroleum polyols in the production process of rigid polyurethane foam, improves the surface defects of foam, but the overall strength and thermal conductivity of foam are greatly lacking.

[0006] Therefore, it is necessary to propose a new solution to further improve the problem of many surface defects of polyurethane foam while maintaining a certain foam strength and thermal conductivity. Summary of the invention

[0007] In order to solve the above technical problems, the present invention proposes a foam leveling agent capable of improving surface defects of polyurethane foam, and a preparation method and application thereof.

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

[0009] As a first aspect of the present invention, a foam leveling agent capable of improving surface defects of polyurethane foam is first provided, which has the following structural expression of formula I:

[0010]

[0011] In formula I, m and n represent the degree of polymerization of each link; wherein m=15-40, preferably 25-35, for example, 20, 25, 30, 35, etc., 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., n=15-40, preferably 20-30, for example, 20, 25, 30, 35, etc.;

[0012] R has the following structural expression:

[0013]

[0014] In formula II, x and y represent the degree of polymerization of each unit, wherein 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] The present invention designs the segment ratio in the polyether modified silicone oil foam leveler, which can maintain the foaming system in a micro-phase compatible state, maximize the compatibility threshold between it and the foaming composite material, thereby significantly improving the surface defects of the polyurethane foam, while maintaining a certain foam strength and thermal conductivity. It has outstanding applications in the fields of building materials / home appliances and the like that have high requirements on the foam surface appearance.

[0016] As a second aspect of the present invention, there is also provided a method for preparing a foam leveling agent capable of improving surface defects of polyurethane foam, comprising the following steps:

[0017] A. Using strong acid as catalyst, octamethylcyclotetrasiloxane, polydimethylhydrogensiloxane and hexamethyldisiloxane are mixed and reacted to obtain side hydrogen-containing silicone oil;

[0018] B. Using a platinum complex as a catalyst, a hydrogenated silicone oil and an allyl polyether are subjected to a hydrosilylation reaction to obtain the foam leveling agent;

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

[0020] The molar ratio of EO and 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 of the present 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, preferably 1000-2000 ppm, of the total mass of octamethylcyclotetrasiloxane, polydimethylhydrogensiloxane and hexamethyldisiloxane.

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

[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 the present invention, the mass ratio of the side hydrogen-containing silicone oil to the allyl polyether is 1:(1.5-2.5), preferably 1:(1.8-2.1). The viscosity of the side hydrogen-containing silicone oil is 30-60 cP or 80-120 cP.

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

[0027] Preferably, the amount of the platinum complex used is 1-20 ppm, preferably 2-5 ppm, based on the total mass of the hydrogenated silicone oil and the allyl polyether, calculated on the basis of the content of metal platinum.

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

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

[0030] As the third aspect of the present invention, there is also provided a foaming agent as described above that can improve the surface defects of polyurethane foam, or a foaming agent as described above that can improve the surface defects of polyurethane foam prepared by the method described above, and its application in the field of polyurethane foaming, especially in the preparation of building materials / household appliances polyurethane foam insulation materials with improved surface defects.

[0031] Compared with the prior art, the present invention has the following beneficial effects:

[0032] The polyether modified silicone oil foaming agent provided by the present invention has strong foam stabilizing ability, good compatibility, high emulsifying ability, and significant improvement effect on foam surface defects in the polyurethane foaming system, and can be used in the field of polyurethane foaming home appliances and building materials, which is more in line with the development needs of the market. In addition, the preparation method provided by the present invention is simple and easy to operate, and is suitable for industrial large-scale production. DETAILED DESCRIPTION

[0033] The present invention is further described below by means of specific examples. The examples described in the present invention are only used to illustrate the present invention and do not limit the scope of the present invention.

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

[0035] Octamethylcyclotetrasiloxane: Dow Corning

[0036] Hexamethyldisiloxane: Bengbu Hengyu

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

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

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

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

[0041] Platinum complex A: divinyltetramethyldisiloxane platinum, Yunnan Guiyan

[0042] Platinum complex B: Hexachloroplatinic acid hexahydrate, Yunnan Guiyan

[0043] [Example 1]

[0044] In a reactor equipped with a stirrer and a thermometer, 60 parts of octamethylcyclotetrasiloxane, 10 parts of polydimethylhydrogensiloxane, 8 parts of hexamethyldisiloxane, and 0.08 parts of trifluoromethanesulfonic acid were added in order by weight, and the reaction was balanced at 60°C for 5 hours. After the reaction was completed, 0.8 parts of calcium carbonate was added to neutralize the trifluoromethanesulfonic acid in the system, and then filtered to obtain a clear and transparent oily liquid, namely, the side hydrogen-containing silicone oil (I). It was determined that the viscosity of the side hydrogen-containing silicone oil (I) was 38cp, the volatile matter was less than 13%, and the Si-H content was 1883ppm.

[0045] Into a reactor equipped with mechanical stirring and a nitrogen pipeline, 85 parts of side hydrogenated silicone oil (I) and 150 parts of allyl polyether ZS-950 were added in sequence, and under the action of 5 ppm of platinum complex A relative to the total mass of the raw materials, the reaction temperature was controlled to 100°C, and a hydrosilylation 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 of octamethylcyclotetrasiloxane, 10 parts of polydimethylhydrogensiloxane and 10 parts of hexamethyldisiloxane, and 0.2 parts of trifluoromethanesulfonic acid were added in order by weight, and the reaction was balanced at 60°C for 4 hours. After the reaction was completed, 4 parts of calcium carbonate were added to neutralize the trifluoromethanesulfonic acid in the system to obtain side hydrogen-containing silicone oil (II). The side hydrogen-containing silicone oil (II) had a viscosity of 61cp, a volatile matter of <13%, and a Si-H content of 2036ppm.

[0048] Into a reactor equipped with mechanical stirring and a nitrogen pipeline, 95 parts of side hydrogenated silicone oil (II) and 200 parts of allyl polyether ZS-1000 were added in sequence, and under the action of 7 ppm of platinum complex A relative to the total mass of the raw materials, the reaction temperature was controlled to 90°C, and a hydrosilylation reaction was carried out for 1.5 hours 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 of octamethylcyclotetrasiloxane, 10 parts of polydimethylhydrogensiloxane, 12 parts of hexamethyldisiloxane, and 0.15 parts of trifluoromethanesulfonic acid were added in order by weight, and the reaction was balanced at 60°C for 4 hours. After the reaction was completed, 1.5 parts of calcium carbonate was added to neutralize the trifluoromethanesulfonic acid in the system to obtain end-side hydrogenated silicone oil (III). The viscosity of the end-side hydrogenated silicone oil (III) was measured to be 45cp, the volatile matter was less than 13%, and the Si-H content was 1994ppm.

[0051] Into a reactor equipped with mechanical stirring and a nitrogen pipeline, 100 parts of hydrogenated silicone oil (III) and 190 parts of allyl polyether ZS-1000 were added in sequence, and under the action of 10 ppm of platinum complex B relative to the total mass of the raw materials, the reaction temperature was controlled to 90°C, and a hydrosilylation 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 of octamethylcyclotetrasiloxane, 10 parts of polydimethylhydrogensiloxane, 4 parts of hexamethyldisiloxane, and 0.2 parts of trifluoromethanesulfonic acid were added in order by weight, and the reaction was balanced at 60°C for 4 hours. After the reaction was completed, 4 parts of calcium carbonate were added to neutralize the trifluoromethanesulfonic acid in the system to obtain end-side hydrogenated silicone oil (IV). The viscosity of the end-side hydrogenated silicone oil (IV) was measured to be 95cp, the volatile matter was less than 13%, and the Si-H content was 1753ppm.

[0054] Into a reactor equipped with mechanical stirring and a nitrogen pipeline, 100 parts of side hydrogenated silicone oil (IV) and 200 parts of allyl polyether ZS-950 were added in sequence, and under the action of 5 ppm of platinum complex B relative to the total mass of the raw materials, the reaction temperature was controlled to 100°C, and a hydrosilylation 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 of octamethylcyclotetrasiloxane, 10 parts of polydimethylhydrogensiloxane, 6 parts of hexamethyldisiloxane, and 0.3 parts of trifluoromethanesulfonic acid were added in order by weight, and the reaction was balanced at 60°C for 4 hours. After the reaction was completed, 6 parts of calcium carbonate were added to neutralize the trifluoromethanesulfonic acid in the system to obtain the end-side hydrogenated silicone oil (V). The viscosity of the end-side hydrogenated silicone oil (V) was measured to be 112cp, the volatile matter was less than 13%, and the Si-H content was 2235ppm.

[0057] Into a reactor equipped with mechanical stirring and a nitrogen pipeline, 90 parts of side hydrogenated silicone oil (V) and 210 parts of allyl polyether ZS-1200 were added in sequence, and under the action of 5 ppm of platinum complex B relative to the total mass of the raw materials, the reaction temperature was controlled to 100°C, and a hydrosilylation 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 of octamethylcyclotetrasiloxane, 10 parts of polydimethylhydrogensiloxane, 8 parts of hexamethyldisiloxane, and 0.3 parts of trifluoromethanesulfonic acid were added in order by weight, and the reaction was balanced at 60°C for 5 hours. After the reaction was completed, 6 parts of calcium carbonate were added to neutralize the trifluoromethanesulfonic acid in the system to obtain end-side hydrogenated silicone oil (VI). The viscosity of the end-side hydrogenated silicone oil (VI) was measured to be 104cp, the volatile matter was less than 13%, and the Si-H content was 2058ppm.

[0060] Into a reactor equipped with mechanical stirring and a nitrogen pipeline, 85 parts of side hydrogenated silicone oil (VI) and 175 parts of allyl polyether ZS-1000 were added in sequence, and under the action of 5 ppm platinum complex A relative to the total mass of the raw materials, the reaction temperature was controlled to 100°C, and a hydrosilylation 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] Basically referring to Example 1, in a reactor with a stirrer and a thermometer, 50 parts of octamethylcyclotetrasiloxane, 10 parts of polydimethylhydrogensiloxane and 12 parts of hexamethyldisiloxane, and 0.08 parts of trifluoromethanesulfonic acid were added in order by weight, and the reaction was balanced at 60° C. for 5 hours. After the reaction was completed, 0.8 parts of calcium carbonate was added to neutralize the trifluoromethanesulfonic acid in the system, and then filtered to obtain a clear and transparent oily liquid, i.e., the side hydrogen-containing silicone oil (x). It was determined that the viscosity of the side hydrogen-containing silicone oil (x) was 25cp, the volatile matter was less than 13%, and the Si-H content was 1752ppm.

[0063] Into a reactor equipped with mechanical stirring and a nitrogen pipeline, 90 parts of side hydrogenated silicone oil (x) and 200 parts of allyl polyether ZS-950 were added in sequence, and under the action of 5 ppm of platinum complex A relative to the total mass of the raw materials, the reaction temperature was controlled to 100°C, and a hydrosilylation 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] Basically referring to Example 6, in a reactor equipped with a stirrer and a thermometer, 230 parts of octamethylcyclotetrasiloxane, 10 parts of polydimethylhydrogensiloxane and 8 parts of hexamethyldisiloxane, and 0.3 parts of trifluoromethanesulfonic acid were added in order by weight, and the equilibrium reaction was carried out at 60° C. for 5 hours. After the reaction was completed, 6 parts of calcium carbonate were added to neutralize the trifluoromethanesulfonic acid in the system to obtain the end-side hydrogenated silicone oil (y). It was determined that the viscosity of the end-side hydrogenated silicone oil (y) was 120cp, the volatile matter was less than 13%, and the Si-H content was 2227ppm.

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

[0067] <Rigid Foaming Method and Test Method>

[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 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 mixed liquid into a fixed mold (60cm*40cm*20cm) to foam and grow on its own, let it stand and cool to room temperature after foaming, and take it out for subsequent testing.

[0077] The main testing methods involved in the present invention are:

[0078] 1. Foam density test adopts GB / T 10807-2006B;

[0079] 2. Surface defect test: After foaming using the above formula in a stainless steel mold with a fixed size 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 and take the average value.

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

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

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

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

[0084] The properties of the foams prepared by 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 Number of surface defects 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 Compression 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 is only a preferred embodiment of the present invention. It should be pointed out that ordinary technicians in this field can make several improvements and supplements without departing from the method of the present invention. These improvements and supplements should also be regarded as the scope of protection of the present invention.

Claims

1. A foam leveling agent capable of improving surface defects of polyurethane foam, characterized in that: It has the following structural expression: In formula I, m and n represent the degree of polymerization of each chain segment; wherein m = 15-40, preferably 25-35, n = 1-20, preferably 5-10; or m = 60-90, preferably 75-85, n = 15-40, preferably 20-30; R has the following structural expression: In formula II, x and y represent the degree of polymerization of each unit, wherein x=2-50, preferably 9-14, and y=2-50, preferably 3-8.

2. A method for preparing a foam leveling agent capable of improving surface defects of polyurethane foam, characterized in that: The following steps are involved: A. Using strong acid as catalyst, octamethylcyclotetrasiloxane, polydimethylhydrogensiloxane and hexamethyldisiloxane are mixed and reacted to obtain side hydrogen-containing silicone oil; B. Using a platinum complex as a catalyst, a hydrogenated silicone oil and an allyl polyether are subjected to a hydrosilylation reaction to obtain the foam leveling agent; The mass ratio of octamethylcyclotetrasiloxane to polydimethylhydrogensiloxane and hexamethyldisiloxane is (4-14):1:(0.5-2), preferably (6-10):1:(0.8-1.2); or, the mass ratio of octamethylcyclotetrasiloxane to polydimethylhydrogensiloxane and hexamethyldisiloxane is (6-24):1:(0.3-2), preferably (16-20):1:(0.4-0.8); 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.

3. The method for preparing a foam leveling agent capable of improving surface defects of polyurethane foam according to claim 2, characterized in that: The strong acid is one or more of concentrated hydrochloric acid, concentrated sulfuric acid, phosphoric acid, and trifluoromethanesulfonic acid; Preferably, the amount of the strong acid used is 500-3000 ppm, preferably 1000-2000 ppm, of the total mass of octamethylcyclotetrasiloxane, polydimethylhydrogensiloxane and hexamethyldisiloxane.

4. The method for preparing a foam leveling agent capable of improving surface defects of polyurethane foam according to claim 2 or 3, characterized in that: In step A, the reaction temperature is 30-100° C., preferably 50-70° C., and the reaction time is 2-10 h, preferably 4-6 h.

5. The method for preparing a foam leveling agent capable of improving surface defects of polyurethane foam according to any one of claims 2 to 4, characterized in that: The mass ratio of the side hydrogen-containing silicone oil to the allyl polyether is 1:(1.5-2.5), preferably 1:(1.8-2.1).

6. The method for preparing a foam leveling agent capable of improving surface defects of polyurethane foam according to any one of claims 2 to 5, characterized in that: The platinum complex is selected from one or more of divinyltetramethyldisiloxane platinum, tetravinyltetramethyltetrasiloxane platinum, hexachloroplatinic acid hexahydrate, preferably divinyltetramethyldisiloxane platinum and / or hexachloroplatinic acid hexahydrate; Preferably, the amount of the platinum complex used is 1-20 ppm, preferably 2-5 ppm, based on the total mass of the hydrogenated silicone oil and the allyl polyether, calculated on the basis of the content of metal platinum.

7. The method for preparing a foam leveling agent capable of improving surface defects of polyurethane foam according to any one of claims 2 to 6, characterized in that: In step B, the reaction temperature is 30-120° C., preferably 80-100° C., and the reaction time is 15-120 min, preferably 30-60 min.

8. Use of the foam leveling agent capable of improving surface defects of polyurethane foam as claimed in claim 1 or the foam leveling agent capable of improving surface defects of polyurethane foam prepared by the method according to any one of claims 2 to 7 in the field of polyurethane foaming.

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