Organic silicon defoaming agent based on synergistic effect of double prepolymers and preparation method of organic silicon defoaming agent

Abstract

The invention discloses an organic silicon defoaming agent based on a synergistic effect of double prepolymers and a preparation method of the organic silicon defoaming agent, and by combining the advantages and characteristics of a siloxane polyurethane prepolymer and a silicon polyether-polyurethane prepolymer, double improvement of defoaming performance and application adaptability is realized. The novel defoaming agent not only can keep stable defoaming capacity under the conditions of high temperature and high pressure, but also can remarkably shorten the time required for defoaming, and has excellent dispersity and long-term effectiveness. By optimizing the proportion of the components and the preparation process, the defoaming agent greatly reduces the environmental burden in the production and use processes while keeping efficient defoaming, and conforms to the development trend of modern green chemical industry.

Description

Technical Field

[0001] The invention relates to the technical field of chemical additives, and in particular to an organosilicon defoamer suitable for high-solid coatings and UV inks. Background Art

[0002] The present invention relates to an organosilicon defoamer and a preparation method thereof. The defoamer comprises a siloxane polyurethane prepolymer and a silicone polyether-polyurethane prepolymer, and can effectively solve foam problems in the fields of water-based coatings, inks, emulsions, etc.

[0003] Currently, the defoamers available on the market primarily include mineral oil, silicone oil, and polyether defoamers. Mineral oil defoamers are widely used due to their low cost, but they can be prone to demulsification and poor stability. Silicone oil defoamers offer good heat resistance and chemical stability, but are expensive and difficult to disperse completely. Polyether defoamers generally exhibit good compatibility and environmental friendliness, but may not provide adequate defoaming effectiveness in certain environments. Although a variety of defoamers are available, each has limitations. For example, single-ingredient defoamers often only work best in specific applications and perform poorly in a wider range of environments. Furthermore, traditional defoamers can exhibit slow defoaming speeds and poor durability during actual use, which not only affects work efficiency but can also lead to reduced quality in the final product. Furthermore, some traditional defoamers may also pose environmental risks, such as high toxicity and poor biodegradability.

[0004] In order to overcome the above-mentioned defects, the present invention constructs a "hydrophobic core-hydrophilic shell" structure at the molecular level through a step-by-step synthesis of prepolymers + gradient compounding process, thereby breaking through the above-mentioned bottleneck. By combining the advantageous properties of silicone polyurethane prepolymers and silicone polyether-polyurethane prepolymers, a dual improvement in defoaming performance and application adaptability is achieved. This new defoamer can not only maintain a stable defoaming ability under high temperature and high pressure conditions, but also significantly shorten the time required for defoaming, while having excellent dispersibility and long-term effectiveness. By optimizing the proportions of each component and the preparation process, the defoamer not only maintains high-efficiency defoaming, but also greatly reduces the environmental burden during production and use, which is in line with the development trend of modern green chemical industry. In short, the present invention aims to fill the gaps in the prior art and provide a more efficient, economical and environmentally friendly solution for related industries. Summary of the Invention

[0005] By bridging the hydrophobic silicone oil segment with the hydrophilic silicone polyether segment through diisocyanate, a synergistic improvement of rapid foam breaking and long-term foam suppression is achieved. Specifically, the organosilicon defoamer based on the synergistic effect of the dual prepolymer is composed of the following components:

[0006] A. Silicone polyurethane prepolymer

[0007] The siloxane polyurethane prepolymer described herein is prepared from diisocyanate and hydroxy silicone oil. Calculated as 100% by mass, the diisocyanate accounts for 30-50% of the prepolymer, with the balance being hydroxy silicone oil. The diisocyanate is selected from toluene diisocyanate (TDI) or diphenylmethane diisocyanate (MDI). The molecular weight of the low-molecule hydroxy silicone oil is controlled between 2000 and 6000. The siloxane polyurethane prepolymer accounts for 10-40% of the total weight of the final defoamer.

[0008] The specific preparation method of the silicone polyurethane prepolymer is as follows:

[0009] Under nitrogen protection conditions, diisocyanate and small molecule hydroxy silicone oil are added to a reaction container in a certain proportion, the reaction temperature is controlled within the range of 70-110°C, and the reaction is continued for 1-4 hours to generate a siloxane polyurethane prepolymer.

[0010] B. Silicone polyether-polyurethane prepolymer

[0011] The silicone polyether-polyurethane prepolymer of the present invention is prepared by reacting diisocyanate with silicone polyether. The silicone polyether is prepared by an addition reaction between a hydrogen-containing polysiloxane and an unsaturated polyether in the presence of a catalyst. The specific preparation method can be found in professional technical literature. The silicone polyether has the following structural formula:

[0012] (CH3)3SiO{(CH3)2SiO) x (CH3GSiO) y}(CH3)3

[0013] Wherein, G is a polyether group, which is represented by the following structural formula:

[0014] -(CH2) z (EO) g (PO) h R

[0015] In the above structural formula, R is -H; the subscripts x, y, z, g, and h represent the degree of polymerization, where x is an integer from 10 to 50; y is an integer from 1 to 10; z is an integer from 2 to 6; g is an integer from 1 to 10; and h is an integer from 1 to 10. The diisocyanate is selected from toluene diisocyanate (TDI) or diphenylmethane diisocyanate (MDI). The diisocyanate reacts with a silicone polyether to form a silicone polyether-polyurethane prepolymer, which accounts for 10-40% of the total defoamer.

[0016] The specific preparation method of the silicone polyether-polyurethane prepolymer is as follows:

[0017] Add diisocyanate and the above-mentioned silicone polyether into a reaction container at an NCO / OH molar ratio of 1:1.2-2, control the reaction temperature at 50-65°C, and react for 1.5-3 hours to generate silicone polyether-polyurethane prepolymer.

[0018] C. Hydrophobic filler

[0019] It is selected from hydrophobic fumed silica and hydrophobic precipitated silica, and can be used alone or in combination, with the dosage accounting for 1-5% of the total mass of the defoamer.

[0020] D. Fatty alcohol polyether

[0021] The fatty alcohol polyether of the present invention is mainly obtained by the addition reaction of fatty alcohol with ethylene oxide (EO) and propylene oxide (PO) under the action of an alkaline catalyst, and can generally be represented by the following structural formula:

[0022] R 1 O(EO) a (PO) b H

[0023] where R 1 The fatty alcohol polyether is a long-chain C10-C22 alkyl group. a and b represent the number of EO and PO groups in a molecule, with a being an integer from 0 to 15 and b being an integer from 1 to 35. The cloud point is 10-20°C. The fatty alcohol polyether can be a random block or a block polyether. The dosage accounts for 40-70% of the total defoamer weight.

[0024] Specific preparation method:

[0025] S1: Place the prepared silicone polyurethane prepolymer and silicone polyether-polyurethane prepolymer in a reaction vessel, add a hydrophobic filler to the mixed system of the above two prepolymers, and disperse the mixed system for 2-4 hours using a high-speed dispersing device to ensure that the hydrophobic filler is evenly distributed in the system.

[0026] S2: Add the fatty alcohol polyether to the mixture containing the prepolymer and the hydrophobic filler, and stir and disperse the mixture for 1-3 hours using a stirring device to ensure that all components are thoroughly mixed. After the mixing is completed, the organosilicon defoamer of the present invention is obtained.

[0027] Beneficial effects:

[0028] (1) Siloxane polyurethane prepolymers are derived from the reaction of diisocyanates (MDI / HDI) and small molecule hydroxyl silicone oils. This combination gives the defoamer excellent heat resistance and chemical stability, while improving its adaptability under extreme conditions.

[0029] (2) Silicone polyether-polyurethane prepolymer is prepared by the reaction of diisocyanate with silicone polyether of a specific structure. The silicone polyether part in its molecular structure provides good compatibility and dispersibility, allowing the defoamer to be better integrated into the target system and reduce the occurrence of side effects.

[0030] (3) In addition, the present invention also adds auxiliary ingredients such as hydrophobic fillers and fatty alcohol polyethers to further enhance the overall performance of the defoamer. DETAILED DESCRIPTION

[0031] Silicone Polyurethane Prepolymer Examples

[0032] Under nitrogen protection, 50 parts of TDI and 50 parts of hydroxy silicone oil with a molecular weight of 3500 were added to a reaction vessel, the reaction temperature was controlled at 100° C., and the reaction was continued for 2.5 hours to generate siloxane polyurethane prepolymer A1.

[0033] Under nitrogen protection, 35 parts of TDI and 65 parts of hydroxy silicone oil with a molecular weight of 2000 were added to a reaction vessel, the reaction temperature was controlled at 110° C., and the reaction was continued for 3.5 hours to generate siloxane polyurethane prepolymer A2.

[0034] Under nitrogen protection, 40 parts of MDI and 60 parts of hydroxy silicone oil with a molecular weight of 6000 were added to a reaction vessel, the reaction temperature was controlled at 70° C., and the reaction was continued for 4.5 hours to generate a siloxane polyurethane prepolymer A3.

[0035] Under nitrogen protection, 45 parts of MDI and 55 parts of hydroxy silicone oil with a molecular weight of 5000 were added to a reaction vessel, the reaction temperature was controlled at 85° C., and the reaction was continued for 1.5 hours to generate a siloxane polyurethane prepolymer A4.

[0036] Under nitrogen protection, 50 parts of monoisocyanate and 50 parts of hydroxy silicone oil with a molecular weight of 3500 were added to a reaction vessel, the reaction temperature was controlled at 100° C., and the reaction was continued for 2.5 hours to generate siloxane polyurethane prepolymer A5.

[0037] Under nitrogen protection, 35 parts of TDI and 65 parts of hydroxy silicone oil with a molecular weight of 10,000 were added to a reaction vessel, the reaction temperature was controlled at 110° C., and the reaction was continued for 3.5 hours to generate siloxane polyurethane prepolymer A6.

[0038] Silicone polyether-polyurethane prepolymer embodiment

[0039] Silicone polyether examples

[0040]

[0041] MDI and the silicon polyether-I were added into the reaction vessel in the proportion of NCO / OH molar ratio of 1:1.2, the reaction temperature was controlled at 65°C, and the reaction time was 2 hours, to generate the silicon polyether-polyurethane prepolymer B1.

[0042] MDI and the silicon polyether-II were added into the reaction vessel in the proportion of NCO / OH molar ratio of 1:1.4, the reaction temperature was controlled at 60°C, and the reaction time was 1.5 hours, to generate the silicon polyether-polyurethane prepolymer B2.

[0043] TDI and the silicon polyether-III were added into the reaction vessel in the proportion of NCO / OH molar ratio of 1:1.8, the reaction temperature was controlled at 65°C, and the reaction time was 2.5 hours, to generate the silicon polyether-polyurethane prepolymer B3.

[0044] TDI and the silicon polyether-IV were added into the reaction vessel in the proportion of NCO / OH molar ratio of 1:2, the reaction temperature was controlled at 50°C, and the reaction time was 3 hours, to generate the silicon polyether-polyurethane prepolymer B4.

[0045] The monoisocyanate and the silicon polyether-I were added into the reaction vessel in the proportion of NCO / OH molar ratio of 1:1.2, the reaction temperature was controlled at 65°C, and the reaction time was 2 hours, to generate the silicon polyether-polyurethane prepolymer B5.

[0046] Fatty alcohol polyether example

[0047]

[0048] Organosilicon defoamer example

[0049] Example 1

[0050] S1: 10 parts of the siloxane polyurethane prepolymer A1 and 30 parts of the silicon polyether-polyurethane prepolymer B1 were placed into a reaction vessel, 3 parts of hydrophobic fumed silica were added into the mixed system of the two prepolymers, and the mixed system was subjected to dispersion treatment for 3 hours through a high-speed dispersion device, so as to ensure that the hydrophobic filler was uniformly distributed in the system.

[0051] S2: 57 parts of the fatty alcohol polyether D1 were added into the mixed system containing the above prepolymers and the hydrophobic filler, and the mixed system was subjected to stirring dispersion for 3 hours through a stirring device, so as to ensure that all the components were fully mixed and uniform. After the mixing was completed, the organosilicon defoamer described in the present application was obtained.

[0052] Example 2

[0053] S1: 30 parts of silicone polyurethane prepolymer A2 and 20 parts of silicone polyether-polyurethane prepolymer B2 are placed in a reaction vessel, and a mixture of 2 parts of hydrophobic fumed silica and hydrophobic precipitated silica is added to the mixed system of the above two prepolymers. The mixed system is dispersed for 4 hours using a high-speed dispersing device to ensure that the hydrophobic filler is evenly distributed in the system.

[0054] S2: Add 48 parts of fatty alcohol polyether D2 to the mixture containing the above prepolymer and hydrophobic filler, and stir and disperse it for 2 hours using a stirring device to ensure that all components are thoroughly mixed. After mixing is completed, the organosilicon defoamer of the present invention is obtained.

[0055] Example 3

[0056] S1: Place 15 parts of silicone polyurethane prepolymer A3 and 10 parts of silicone polyether-polyurethane prepolymer B3 in a reaction vessel, add 5 parts of hydrophobic precipitated silica to the mixed system of the above two prepolymers, and disperse the mixed system for 2 hours using a high-speed dispersing device to ensure that the hydrophobic filler is evenly distributed in the system.

[0057] S2: Add 70 parts of fatty alcohol polyether D3 to the mixture containing the above prepolymer and hydrophobic filler, and stir and disperse for 2.5 hours using a stirring device to ensure that all components are thoroughly mixed. After mixing, the organosilicon defoamer of the present invention is obtained.

[0058] Example 4

[0059] S1: 40 parts of silicone polyurethane prepolymer A4 and 15 parts of silicone polyether-polyurethane prepolymer B4 are placed in a reaction vessel, and a mixture of 4 parts of hydrophobic fumed silica and hydrophobic precipitated silica is added to the mixed system of the above two prepolymers. The mixed system is dispersed for 2.5 hours using a high-speed dispersing device to ensure that the hydrophobic filler is evenly distributed in the system.

[0060] S2: Add 41 parts of fatty alcohol polyether D4 to the mixture containing the above prepolymer and hydrophobic filler, and stir and disperse it for 3 hours using a stirring device to ensure that all components are fully mixed. After mixing is completed, the organosilicon defoamer of the present invention is obtained.

[0061] Example 5

[0062] S1: 30 parts of silicone polyurethane prepolymer A1 and 25 parts of silicone polyether-polyurethane prepolymer B1 are placed in a reaction vessel, 5 parts of hydrophobic precipitated silica are added to the mixed system of the above two prepolymers, and the mixed system is dispersed for 3 hours using a high-speed dispersing device to ensure that the hydrophobic filler is evenly distributed in the system.

[0063] S2: Add 40 parts of fatty alcohol polyether D5 to the mixture containing the above prepolymer and hydrophobic filler, and stir and disperse it for 2 hours using a stirring device to ensure that all components are fully mixed. After mixing is completed, the organosilicon defoamer of the present invention is obtained.

[0064] Example 6

[0065] S1: 14 parts of silicone polyurethane prepolymer A2 and 19 parts of silicone polyether-polyurethane prepolymer B2 are placed in a reaction vessel, and a mixture of 2 parts of hydrophobic fumed silica and hydrophobic precipitated silica is added to the mixed system of the above two prepolymers. The mixed system is dispersed for 4 hours using a high-speed dispersing device to ensure that the hydrophobic filler is evenly distributed in the system.

[0066] S2: Add 65 parts of fatty alcohol polyether D6 to the mixture containing the above prepolymer and hydrophobic filler, and stir and disperse it using a stirring device for 1 hour to ensure that all components are thoroughly mixed. After mixing is completed, the organosilicon defoamer of the present invention is obtained.

[0067] Example 7

[0068] S1: Place 10 parts of silicone polyurethane prepolymer A3 and 40 parts of silicone polyether-polyurethane prepolymer B3 in a reaction vessel, add 1 part of hydrophobic fumed silica to the mixed system of the above two prepolymers, and disperse the mixed system for 2 hours using a high-speed dispersing device to ensure that the hydrophobic filler is evenly distributed in the system.

[0069] S2: Add 49 parts of fatty alcohol polyether D7 to the mixture containing the above prepolymer and hydrophobic filler, and stir and disperse it using a stirring device for 1.5 hours to ensure that all components are thoroughly mixed. After mixing is completed, the silicone defoamer of the present invention is obtained.

[0070] Example 8

[0071] S1: Place 25 parts of silicone polyurethane prepolymer A4 and 15 parts of silicone polyether-polyurethane prepolymer B4 in a reaction vessel, add 2 parts of hydrophobic precipitated silica to the mixed system of the above two prepolymers, and disperse the mixed system for 3 hours using a high-speed dispersing device to ensure that the hydrophobic filler is evenly distributed in the system.

[0072] S2: Add 58 parts of fatty alcohol polyether D8 to the mixture containing the above prepolymer and hydrophobic filler, and stir and disperse for 2.5 hours using a stirring device to ensure that all components are thoroughly mixed. After mixing, the organosilicon defoamer of the present invention is obtained.

[0073] Comparative Example 1

[0074] S1: 40 parts of silicone polyether-polyurethane prepolymer B1 was placed in a reaction vessel, 3 parts of hydrophobic fumed silica was added into the mixed system of the above two prepolymers, and the mixed system was dispersed by high-speed dispersion equipment for 3 hours to ensure that the hydrophobic filler was uniformly distributed in the system.

[0075] S2: 57 parts of fatty alcohol polyether D1 was added into the mixed system containing the above prepolymers and hydrophobic fillers, and stirred and dispersed by stirring equipment for 3 hours to ensure that all components were fully mixed and uniform. After mixing, the silicone defoamer of the present application was obtained.

[0076] Comparative Example 2

[0077] S1: 50 parts of silicone polyurethane prepolymer A2 was placed in a reaction vessel, 2 parts of a mixture of hydrophobic fumed silica and hydrophobic precipitated silica was added into the mixed system of the above two prepolymers, and the mixed system was dispersed by high-speed dispersion equipment for 4 hours to ensure that the hydrophobic filler was uniformly distributed in the system.

[0078] S2: 48 parts of fatty alcohol polyether D2 was added into the mixed system containing the above prepolymers and hydrophobic fillers, and stirred and dispersed by stirring equipment for 2 hours to ensure that all components were fully mixed and uniform. After mixing, the silicone defoamer of the present application was obtained.

[0079] Comparative Example 3

[0080] S1: 15 parts of silicone polyurethane prepolymer A5 and 10 parts of silicone polyether-polyurethane prepolymer B3 were placed in a reaction vessel, 5 parts of hydrophobic precipitated silica was added into the mixed system of the above two prepolymers, and the mixed system was dispersed by high-speed dispersion equipment for 2 hours to ensure that the hydrophobic filler was uniformly distributed in the system.

[0081] S2: 70 parts of fatty alcohol polyether D3 was added into the mixed system containing the above prepolymers and hydrophobic fillers, and stirred and dispersed by stirring equipment for 2.5 hours to ensure that all components were fully mixed and uniform. After mixing, the silicone defoamer of the present application was obtained.

[0082] Comparative Example 4

[0083] S1: 40 parts of silicone polyurethane prepolymer A6 and 15 parts of silicone polyether-polyurethane prepolymer B4 were placed in a reaction vessel, 4 parts of a mixture of hydrophobic fumed silica and hydrophobic precipitated silica was added into the mixed system of the above two prepolymers, and the mixed system was dispersed by high-speed dispersion equipment for 2.5 hours to ensure that the hydrophobic filler was uniformly distributed in the system.

[0084] S2: Add 41 parts of fatty alcohol polyether D4 to the mixture containing the above prepolymer and hydrophobic filler, and stir and disperse it for 3 hours using a stirring device to ensure that all components are fully mixed. After mixing is completed, the organosilicon defoamer of the present invention is obtained.

[0085] Comparative Example 5

[0086] S1: 30 parts of silicone polyurethane prepolymer A1 and 25 parts of silicone polyether-polyurethane prepolymer B5 are placed in a reaction vessel. 5 parts of hydrophobic precipitated silica are added to the mixture of the two prepolymers. The mixture is dispersed for 3 hours using a high-speed dispersing device to ensure that the hydrophobic filler is evenly distributed in the system.

[0087] S2: Add 40 parts of fatty alcohol polyether D5 to the mixture containing the above prepolymer and hydrophobic filler, and stir and disperse it for 2 hours using a stirring device to ensure that all components are fully mixed. After mixing is completed, the organosilicon defoamer of the present invention is obtained.

[0088] Performance testing:

[0089] (1) Anti-foaming performance test:

[0090] Air blowing test method: In a 500ml graduated cylinder, put 110g of homemade test ink sample, of which the defoamer addition amount is 3.5‰, put it into the air blowing device, adjust the flow rate to 1L / min, turn on the air blowing to continuously blow air into the cylinder, and record the change pattern of foam volume V with time t; fix the air blowing time and compare the foam height.

[0091] The test results are as follows:

[0092] Unit: ml

[0093]

[0094] (2) Compatibility test

[0095] High-speed dispersion method: Add 85g of green ink and 0.3g of the defoamer to be tested into the cup and use a laboratory high-speed dispersion

[0096] Use a machine to disperse the ink at a high speed of 1000 rpm for 5 minutes, then use a dropper to absorb an appropriate amount of ink and drop it onto the color wheel. Then coat the black and white cardboard. Observe the state of the coating and express it with a grade. The higher the grade, the better the compatibility.

[0097] Coating grade classification:

[0098]

[0099] The test results are as follows:

[0100]

Claims

1. An organosilicon defoamer based on the synergistic effect of dual prepolymers, characterized in that: The defoamer comprises the following components: A. Silicone polyurethane prepolymer: The dosage accounts for 10-40% of the total amount of the final defoamer; B. Silicone polyether-polyurethane prepolymer: the dosage accounts for 10-40% of the total defoamer; C. Hydrophobic filler: The dosage accounts for 1-5% of the total mass of the defoamer; D. Fatty alcohol polyether: The dosage accounts for 40-70% of the total mass of the defoamer; The preparation method of the organosilicon defoamer based on the synergistic effect of the dual prepolymers is as follows: S1: placing the prepared silicone polyurethane prepolymer and silicone polyether-polyurethane prepolymer in a reaction vessel, adding a hydrophobic filler to the mixed system of the above two prepolymers, and dispersing the mixed system for 2-4 hours using a high-speed dispersing device to ensure that the hydrophobic filler is evenly distributed in the system; S2: Adding the fatty alcohol polyether to the mixed system containing the above-mentioned prepolymer and the hydrophobic filler, stirring and dispersing the mixture for 1-3 hours by a stirring device to ensure that all the components are fully mixed; after the mixing is completed, the organosilicon defoamer of the present invention is obtained.

2. According to claim 1, an organosilicon defoamer based on the synergistic effect of dual prepolymers, characterized in that: The siloxane polyurethane prepolymer is prepared from diisocyanate and hydroxy silicone oil. Calculated by mass, the diisocyanate accounts for 30-50% of the prepolymer mass, and the balance is hydroxy silicone oil. The molecular weight of the small molecule hydroxy silicone oil is controlled between 2000 and 6000.

3. According to claim 1, an organosilicon defoamer based on the synergistic effect of dual prepolymers, characterized in that: The specific preparation method of the siloxane polyurethane prepolymer is as follows: under nitrogen protection conditions, diisocyanate and small molecule hydroxyl silicone oil are added into a reaction container in a certain proportion, the reaction temperature is controlled within the range of 70-110°C, and the reaction is continued for 1-4 hours to generate the siloxane polyurethane prepolymer.

4. According to claim 1, an organosilicon defoamer based on the synergistic effect of dual prepolymers, characterized in that: The silicone polyether-polyurethane prepolymer is prepared by reacting diisocyanate with silicone polyether. The silicone polyether is prepared by an addition reaction between hydrogen-containing polysiloxane and unsaturated polyether in the presence of a catalyst. The specific preparation method can be found in professional technical literature. The structural formula of the silicone polyether is represented by the following general formula: (CH3)3SiO{(CH3)2SiO) x (CH3GSiO) y }(CH3)3 Wherein, G is a polyether group, which is represented by the following general structural formula: -(CH2) z (IS) g (PO) h R In the above structural formula, R is -H; the subscripts x, y, z, g, and h represent the degree of polymerization, where x is an integer of 10 to 50; y is an integer of 1 to 10; z is an integer of 2 to 6; g is an integer of 1 to 10; and h is an integer of 1 to 10.

5. According to claim 1, an organosilicon defoamer based on the synergistic effect of dual prepolymers, characterized in that: The specific preparation method of the silicone polyether-polyurethane prepolymer is to add diisocyanate and the above-mentioned silicone polyether into a reaction container at an NCO / OH molar ratio of 1:1.2-2, control the reaction temperature at 50-65°C, and react for 1.5-3 hours to generate a silicone polyether-polyurethane prepolymer.

6. According to claim 1, an organosilicon defoamer based on the synergistic effect of dual prepolymers, characterized in that: The diisocyanate is selected from toluene diisocyanate (TDI) or diphenylmethane diisocyanate (MDI).

7. According to claim 1, an organosilicon defoamer based on the synergistic effect of dual prepolymers, characterized in that: The hydrophobic fumed silica and hydrophobic precipitated silica can be used alone or in combination.

8. According to claim 1, an organosilicon defoamer based on the synergistic effect of dual prepolymers, characterized in that: The fatty alcohol polyether is mainly obtained by adding fatty alcohol to ethylene oxide (EO) and propylene oxide (PO) under the action of a base catalyst, and can generally be represented by the following structural formula: R 1 O(EO) a (PO) b H where R 1 It is a long-chain alkyl group of C10 to C22, a and b represent the number of EO and PO in one molecule, a is an integer of 0 to 15, b is an integer of 1 to 35, and the cloud point is 10 to 20°C; the fatty alcohol polyether can be a random block or a block polyether.

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