Modified polyurethane resin for synthetic leather and production process thereof

Abstract

The invention relates to the technical field of synthetic leather, and discloses a modified polyurethane resin for synthetic leather and a production process thereof, the modified polyurethane resin comprises the following raw materials: polytetrahydrofuran ether glycol, hexamethylene diisocyanate, a modified rubber component, a catalyst, a small molecule chain extender, a flame retardant additive, triethylamine and deionized water, according to the modified rubber component, a rigid ring is introduced into the structure of epichlorohydrin rubber and participates in the preparation process of the polyurethane resin, so that the mechanical property of the modified polyurethane resin is effectively improved; according to the flame-retardant additive, an organic nitrogen-phosphorus flame retardant is grafted on the surface of layered serpentine powder, so that an inorganic-organic composite flame retardant is formed in the resin, the flame retardance of the modified polyurethane resin is remarkably enhanced, and the service life of a polyurethane synthetic leather product is prolonged.

Description

Technical Field

[0001] The invention relates to the technical field of synthetic leather, and in particular to a modified polyurethane resin for synthetic leather and a production process thereof. Background Art

[0002] In recent years, with the development of science and technology and the improvement of living standards, people's demand for daily products has gradually increased. Leather products, as a common daily product, have huge market potential. However, with the growth of population and the enhancement of animal protection awareness, natural leather products can no longer meet the growing market demand. In order to solve this problem, synthetic leather came into being. Because of its beautiful appearance, low cost and many choices, it has become the best choice to replace natural leather.

[0003] Synthetic leather is usually based on non-woven fabric as the substrate, and then the surface of the substrate is coated with synthetic resins such as polyurethane resin and polyvinyl chloride resin. Among them, polyurethane synthetic leather is widely used in automotive interior, luggage, home furnishings, shoes and clothing due to its good comfort, weather resistance, durability, easy processing and other characteristics. With the development of modern industry, higher requirements are placed on the functionality of polyurethane resin. Compared with ordinary polyurethane resin, polyurethane resin used for synthetic leather needs to have excellent mechanical properties, because during the use of polyurethane synthetic leather products, it may be subject to collision or impact of various external forces. If the mechanical properties of polyurethane resin are not good, it is difficult to effectively resist these external forces, and deformation, breakage and other problems are prone to occur. In addition, ordinary polyurethane resin is a combustible material that will ignite when exposed to fire, burns quickly, and is accompanied by the generation of a large amount of toxic smoke, causing great safety hazards. Therefore, it is of great practical significance to prepare a polyurethane resin with excellent mechanical properties and flame retardant properties.

[0004] The patent with announcement number CN105131227B discloses a UV-curable flame-retardant polyurethane for synthetic leather and a preparation method thereof. The invention achieves good flame retardant effect by "hanging" phosphorus (nitrogen) flame retardant components on the side chains of polyurethane macromolecular chains, and both the chain extender and the end capping agent contain flame retardant components such as phosphorus and nitrogen, so that the prepared polyurethane resin has excellent flame retardant properties. Therefore, the polyurethane resin can be modified by preparing additives with excellent mechanical properties and flame retardant properties to obtain high-performance polyurethane resin. Summary of the invention

[0005] In order to solve the problems mentioned in the background technology, the object of the present invention is to provide a modified polyurethane resin for synthetic leather and a production process thereof.

[0006] The purpose of the present invention can be achieved through the following technical solutions:

[0007] A modified polyurethane resin for synthetic leather comprises the following raw materials in parts by weight: 30-50 parts of polytetramethylene ether glycol, 20-40 parts of hexamethylene diisocyanate, 4-8 parts of modified rubber components, 0.5-1.5 parts of catalysts, 3-5 parts of small molecule chain extenders, 3-7 parts of flame retardant additives, 1-2 parts of triethylamine, and 40-60 parts of deionized water.

[0008] Furthermore, the preparation method of the modified rubber component comprises the following steps:

[0009] Step I: add chloroether rubber to the toluene solution, stir mechanically to obtain a uniform mixture, then add dimethylaminoisopropanol, raise the temperature to 60-70°C, stir for 5-7h, and then remove the solvent by rotary evaporation to obtain an intermediate material;

[0010] Step II: Add the intermediate material and dimethyl sulfoxide solution into a reaction kettle protected by inert gas, stir evenly, then add bicyclo[2.2.2]oct-7-ene-2,3,5,6-tetracarboxylic dianhydride, after the addition is complete, mechanically stir at room temperature for 4 to 6 hours, evaporate and remove the solvent, and obtain the modified rubber component.

[0011] Furthermore, in step I, the number average molecular weight of the chloroether rubber is 5000 to 15000.

[0012] Furthermore, in step II, the inert gas is any one of argon, neon or helium.

[0013] Furthermore, the catalyst is any one of dibutyltin dilaurate, stannous octoate or dimorpholinyl diethyl ether; and the small molecule chain extender is any one of ethylene glycol, 1,4-butanediol or 1,3-propylene glycol.

[0014] Furthermore, the method for preparing the flame retardant additive comprises the following steps:

[0015] Add layered serpentine powder to N,N-dimethylformamide solution, ultrasonicate to form a uniform dispersion, add 2,3-pyridinedicarboxylic anhydride to the dispersion under continuous nitrogen conditions, increase the temperature to 70-90°C, keep stirring for 3-7 hours, then add flame retardant FRC-2 and esterification catalyst to the mixed system, increase the temperature of the mixed system to 90-110°C under stirring conditions, keep warm for 4-8 hours, wait for the material to cool naturally, centrifuge to separate the solid material, wash the solid material, and vacuum dry to obtain a flame retardant additive.

[0016] Furthermore, the average particle size of the layered serpentine powder is 5 μm.

[0017] Furthermore, the mass ratio of the layered serpentine powder to 2,3-pyridinedicarboxylic anhydride is 1:0.1-0.4.

[0018] Furthermore, the esterification catalyst is any one of p-toluenesulfonic acid, aminosulfonic acid or trifluoromethanesulfonic acid.

[0019] A production process of modified polyurethane resin for synthetic leather comprises the following steps:

[0020] Step 1: Add polytetrahydrofuran ether diol, hexamethylene diisocyanate and modified rubber component into a reaction kettle, stir and mix evenly, add a catalyst under the protection of a nitrogen atmosphere, turn on the heating, wait for the system temperature to reach 70-90°C, stir at a constant temperature for 1-3h, then add a small molecule chain extender, continue stirring for 1-2h, and obtain a polyurethane prepolymer;

[0021] Step 2: Add flame retardant additives, triethylamine and deionized water to the polyurethane prepolymer, stir at high speed, and defoam naturally to obtain a modified polyurethane resin.

[0022] Beneficial effects of the present invention:

[0023] (1) The present invention adds a modified rubber component and a flame retardant additive during the preparation of the polyurethane resin, so that the prepared modified polyurethane resin has excellent mechanical properties and flame retardant properties, which is beneficial to prolonging the service life of the polyurethane synthetic leather products and has greater practical promotion value.

[0024] (2) The present invention prepares a modified rubber component to modify the mechanical properties of the polyurethane resin. On the one hand, since the structure of the modified rubber component contains a carboxyl group generated by a ring-opening reaction, it can participate in the preparation process of the polyurethane resin, so that the density of the modified polyurethane resin is effectively improved, thereby enhancing the mechanical properties of the modified polyurethane resin. On the other hand, the chloroether rubber in the structure of the modified rubber component has a good toughening effect, which can hinder the expansion of cracks when subjected to external forces, thereby improving the toughness of the modified polyurethane resin. In addition, the rigid ring in the structure of the modified rubber component can stably exist in the polyurethane resin, so that the modified polyurethane resin has higher strength and stability, thereby showing more excellent mechanical properties, and avoiding deformation, breakage and other problems of polyurethane synthetic leather products due to collision or impact by various external forces.

[0025] (3) The flame retardant additive prepared by the present invention is a layered serpentine powder with a nitrogen-phosphorus flame retardant grafted on the surface. Since the layered serpentine powder is connected to each other by chemical bonds, the layered serpentine powder can be evenly dispersed in the polyurethane resin, avoiding the negative impact caused by the agglomeration of the layered serpentine powder. The presence of the layered serpentine powder can form a stable physical barrier layer in the resin, effectively isolating oxygen and heat, and preventing further combustion, thereby enhancing the flame retardant properties of the modified polyurethane resin and further improving the mechanical properties of the modified polyurethane resin. In addition, the layered serpentine powder can form an inorganic-organic composite flame retardant with the organic nitrogen-phosphorus flame retardant grafted on the surface, so that a small amount of flame retardant additive can be added to give the modified polyurethane resin excellent flame retardant properties. After testing, the limited oxygen index of the modified polyurethane resin obtained can reach up to 31.9%, showing good flame retardant properties, thereby ensuring the safety of polyurethane synthetic leather products.

[0026] Of course, any product implementing the present invention does not necessarily need to achieve all of the advantages described above at the same time. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the accompanying drawings required for describing the embodiments will be briefly introduced below. Obviously, the accompanying drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other accompanying drawings can be obtained based on these accompanying drawings without paying creative work.

[0028] Figure 1 This is an infrared spectrum test chart of the modified rubber component prepared in the present invention.

[0029] Figure 2 This is an infrared spectrum test chart of the flame retardant additive prepared by the present invention. DETAILED DESCRIPTION

[0030] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0031] The modified rubber components and flame retardant additives in the examples and comparative examples of the present invention are prepared by the following method:

[0032] 1. Preparation of modified rubber components

[0033] Step I: add 6 g of chloroether rubber with a number average molecular weight of 9000 to the toluene solution, stir mechanically to make it uniform, then add 1 g of dimethylaminoisopropanol, after the addition is completed, raise the temperature to 65° C., stir for 6 hours, and then remove the solvent by rotary evaporation to obtain an intermediate material;

[0034] Step II: Add 6 g of the intermediate material and dimethyl sulfoxide solution into an argon-protected reactor, stir evenly, then add 1.2 g of bicyclo[2.2.2]oct-7-ene-2,3,5,6-tetracarboxylic dianhydride. After the addition is complete, mechanically stir at room temperature for 5 hours, evaporate and remove the solvent, and obtain a modified rubber component.

[0035] Technical principle: In step I, the halogen functional group in the epichlorohydrin rubber structure can undergo a quaternary ammonium reaction with the tertiary amine group in the dimethylaminoisopropanol structure, thereby introducing a hydroxyl group into the epichlorohydrin rubber structure to obtain an intermediate material; in step II, the hydroxyl group in the intermediate material structure and the anhydride group in the bicyclo[2.2.2]oct-7-ene-2,3,5,6-tetracarboxylic dianhydride structure undergo a ring-opening esterification reaction to obtain a modified rubber component.

[0036] The modified rubber components were analyzed by infrared spectroscopy using a FTIR-850 Fourier transform infrared spectrometer (Tianjin Gangdong Technology Development Co., Ltd.). Figure 1 As shown by Figure 1 It can be seen that 1041cm -1 The absorption peak of ether bond COC appears at 1370 cm -1 The absorption peak of CN in quaternary ammonium salt appears at 1759 cm -1 The absorption peak of the ester group C=O appears at 1725 cm -1 The absorption peak of the carboxyl group C=O appears at 3030cm -1 The absorption peak of CH in the carbon-carbon double bond appears at .

[0037] 2. Preparation of flame retardant additives

[0038] 5 g of layered serpentine powder with an average particle size of 5 μm was added to an N,N-dimethylformamide solution, and ultrasonicated to form a uniform dispersion. Under continuous nitrogen conditions, 1.2 g of 2,3-pyridinedicarboxylic anhydride was added to the dispersion, the temperature was raised to 80°C, and the mixture was stirred for 5 hours. Then, 1.4 g of flame retardant FRC-2 and 0.1 g of p-toluenesulfonic acid were added to the mixed system, and the temperature of the mixed system was raised to 100°C under stirring conditions, and the mixture was kept warm for 6 hours. After the material was naturally cooled, the solid material was separated by centrifugation, the solid material was washed, and vacuum dried to obtain a flame retardant additive.

[0039] Technical principle: The anhydride group in the 2,3-pyridinedicarboxylic acid anhydride structure is highly active and can undergo a ring-opening esterification reaction with the hydroxyl groups on the surface of the layered serpentine powder, thereby introducing carboxyl groups on the surface of the layered serpentine powder. p-Toluenesulfonic acid is used as an esterification catalyst to catalyze the reaction between the carboxyl groups on the surface of the layered serpentine powder and the hydroxyl groups in the structure of the flame retardant FRC-2, thereby chemically connecting the flame retardant FRC-2 to the surface of the layered serpentine powder to obtain a flame retardant additive.

[0040] The flame retardant additives were analyzed by infrared spectroscopy using a FTIR-850 Fourier transform infrared spectrometer (Tianjin Gangdong Technology Development Co., Ltd.). Figure 2 As shown by Figure 2 It can be seen that 1750cm -1 The absorption peak of the ester group C=O appears at 1605cm -1 The absorption peak of C=N appears at 1410cm -1 The absorption peak of CN appears at 3309cm -1 The absorption peak of NH in amide appears at 1654 cm -1 The absorption peak of C=O in amide appears at 1060cm -1 The absorption peak of POC appears at 1280 cm -1 The absorption peak of P=O appears at

[0041] Example 1

[0042] Preparation of modified polyurethane resin

[0043] Step 1: Add 30g of polytetramethylene ether glycol, 20g of hexamethylene diisocyanate and 4g of modified rubber component into a reaction kettle, stir and mix evenly, add 0.5g of dibutyltin dilaurate under nitrogen atmosphere protection, turn on heating after the addition, and stir at a constant temperature for 1h after the system temperature reaches 70°C, then add 3g of 1,3-propylene glycol, and continue stirring for 1h to obtain a polyurethane prepolymer;

[0044] Step 2: Add 3 g of flame retardant additive, 1 g of triethylamine and 40 g of deionized water to the polyurethane prepolymer, stir and mix at a stirring rate of 400 r / min for 4 hours, and obtain a modified polyurethane resin after natural defoaming.

[0045] Example 2

[0046] Preparation of modified polyurethane resin

[0047] Step 1: Add 40g of polytetramethylene ether glycol, 30g of hexamethylene diisocyanate and 6g of modified rubber component into a reaction kettle, stir and mix evenly, add 1g of dibutyltin dilaurate under the protection of nitrogen atmosphere, turn on heating after the addition, and stir at a constant temperature for 2h after the system temperature reaches 80°C, then add 4g of 1,3-propylene glycol, and continue stirring for 1.5h to obtain a polyurethane prepolymer;

[0048] Step 2: Add 5 g of flame retardant additive, 1.5 g of triethylamine and 50 g of deionized water to the polyurethane prepolymer, stir and mix at a stirring rate of 500 r / min for 5 hours, and obtain a modified polyurethane resin after natural defoaming.

[0049] Example 3

[0050] Preparation of modified polyurethane resin

[0051] Step 1: Add 50g of polytetramethylene ether glycol, 40g of hexamethylene diisocyanate and 8g of modified rubber component into a reaction kettle, stir and mix evenly, add 1.5g of dibutyltin dilaurate under nitrogen atmosphere protection, turn on heating after the addition, and stir at a constant temperature for 3h after the system temperature reaches 90°C, then add 5g of 1,3-propylene glycol, and continue stirring for 2h to obtain a polyurethane prepolymer;

[0052] Step 2: Add 7 g of flame retardant additive, 2 g of triethylamine and 60 g of deionized water to the polyurethane prepolymer, stir and mix at a stirring rate of 600 r / min for 6 hours, and obtain a modified polyurethane resin after natural defoaming.

[0053] Comparative Example 1

[0054] Preparation of modified polyurethane resin

[0055] Step 1: Add 40g of polytetramethylene ether glycol, 30g of hexamethylene diisocyanate and 6g of modified rubber component into a reaction kettle, stir and mix evenly, add 1g of dibutyltin dilaurate under the protection of nitrogen atmosphere, turn on heating after the addition, and stir at a constant temperature for 2h after the system temperature reaches 80°C, then add 4g of 1,3-propylene glycol, and continue stirring for 1.5h to obtain a polyurethane prepolymer;

[0056] Step 2: Add 1.5 g of triethylamine and 50 g of deionized water to the polyurethane prepolymer, stir and mix at a stirring rate of 500 r / min for 5 hours, and obtain a modified polyurethane resin after natural defoaming.

[0057] Comparative Example 2

[0058] Preparation of modified polyurethane resin

[0059] Step 1: Add 40g of polytetramethylene glycol and 30g of hexamethylene diisocyanate into a reaction kettle, stir and mix evenly, add 1g of dibutyltin dilaurate under the protection of nitrogen atmosphere, turn on the heating after the addition, and stir at a constant temperature for 2h after the system temperature reaches 80°C, then add 4g of 1,3-propylene glycol, and continue stirring for 1.5h to obtain a polyurethane prepolymer;

[0060] Step 2: Add 5 g of flame retardant additive, 1.5 g of triethylamine and 50 g of deionized water to the polyurethane prepolymer, stir and mix at a stirring rate of 500 r / min for 5 hours, and obtain a modified polyurethane resin after natural defoaming.

[0061] Comparative Example 3

[0062] Preparation of modified polyurethane resin

[0063] Step 1: Add 40g of polytetramethylene ether glycol, 30g of hexamethylene diisocyanate and 6g of modified rubber component into a reaction kettle, stir and mix evenly, add 1g of dibutyltin dilaurate under the protection of nitrogen atmosphere, turn on heating after the addition, and stir at a constant temperature for 2h after the system temperature reaches 80°C, then add 4g of 1,3-propylene glycol, and continue stirring for 1.5h to obtain a polyurethane prepolymer;

[0064] Step 2: Add 4 g of layered serpentine powder, 1 g of flame retardant FRC-2, 1.5 g of triethylamine, and 50 g of deionized water to the polyurethane prepolymer, stir and mix at a stirring rate of 500 r / min for 5 hours, and obtain a modified polyurethane resin after natural defoaming.

[0065] Comparative Example 4

[0066] Preparation of modified polyurethane resin

[0067] Step 1: Add 40g of polytetramethylene glycol and 30g of hexamethylene diisocyanate into a reaction kettle, stir and mix evenly, add 1g of dibutyltin dilaurate under the protection of nitrogen atmosphere, turn on the heating after the addition, and stir at a constant temperature for 2h after the system temperature reaches 80°C, then add 4g of 1,3-propylene glycol, and continue stirring for 1.5h to obtain a polyurethane prepolymer;

[0068] Step 2: Add 1.5 g of triethylamine and 50 g of deionized water to the polyurethane prepolymer, stir and mix at a stirring rate of 500 r / min for 5 hours, and obtain a modified polyurethane resin after natural defoaming.

[0069] Performance testing:

[0070] The modified polyurethane resins prepared in Examples 1 to 3 and Comparative Examples 1 to 4 were uniformly coated on a steel plate that met the specifications, and cured at 80°C for 2 hours to prepare samples. The samples were tested for tensile properties and elongation at break according to GB / T 1040.1-2018 "Determination of tensile properties of plastics Part 1: General Principles"; the samples were tested for combustion properties according to GB / T 2406.2-2009 "Determination of combustion behavior of plastics by oxygen index method Part 2: Room temperature test". The specific test results are shown in Table 1:

[0071] Table 1 - Performance Test Tensile strength (MPa) Elongation at break (%) Limiting oxygen index (%) Example 1 45.8 475 31.5 Example 2 46.2 480 31.9 Example 3 45.5 470 31.3 Comparative Example 1 39.6 460 25.7 Comparative Example 2 31.7 410 29.6 Comparative Example 3 42.1 465 27.4 Comparative Example 4 25.4 390 23.2

[0072] From the test results in Table 1, it can be seen that the modified polyurethane resins prepared in Examples 1 to 3 all have excellent mechanical properties and flame retardant properties; the modified polyurethane resin prepared in Comparative Example 1 does not add flame retardant additives, and compared with the examples, the limiting oxygen index of the sample decreases significantly, and the flame retardant performance of the modified polyurethane resin is poor; the modified polyurethane resin prepared in Comparative Example 2 does not add modified rubber components, and the tensile strength and elongation at break of the sample decrease significantly, and the mechanical properties of the modified polyurethane resin are not as good as those of the examples; the modified polyurethane resin prepared in Comparative Example 3 Modified rubber components, layered serpentine powder and flame retardant FRC-2 were added to the modified polyurethane resin. The mechanical properties of the sample were good, but the flame retardant properties were average. It is speculated that this may be because the layered serpentine powder was not organically modified, and it was difficult to disperse evenly in the matrix, resulting in agglomeration. In addition, the small molecule flame retardant FRC-2 may have migrated in the matrix, resulting in a decrease in the flame retardant properties of the modified polyurethane resin. The modified polyurethane resin prepared in Comparative Example 4 did not contain modified rubber components and flame retardant additives, so the mechanical properties and flame retardant properties of the sample were the worst.

[0073] The above contents are merely examples and explanations of the concept of the present invention. The technicians in this technical field may make various modifications or additions to the specific embodiments described or replace them in a similar manner. As long as they do not deviate from the concept of the invention or exceed the scope defined by the claims, they should all fall within the protection scope of the present invention.

Claims

1. A modified polyurethane resin for synthetic leather, characterized in that: The invention comprises the following raw materials in parts by weight: 30 to 50 parts of polytetramethylene ether glycol, 20 to 40 parts of hexamethylene diisocyanate, 4 to 8 parts of modified rubber components, 0.5 to 1.5 parts of catalysts, 3 to 5 parts of small molecule chain extenders, 3 to 7 parts of flame retardant additives, 1 to 2 parts of triethylamine and 40 to 60 parts of deionized water.

2. The modified polyurethane resin for synthetic leather according to claim 1, characterized in that: The preparation method of the modified rubber component comprises the following steps: Step I: adding chloroether rubber and dimethylaminoisopropyl alcohol to a toluene solution, mechanically stirring the solution, heat-treating the solution at 60 to 70° C. for 5 to 7 hours, discharging the solution, and obtaining an intermediate material; Step II: Under the protection of inert gas, add the intermediate material and bicyclo[2.2.2]oct-7-ene-2,3,5,6-tetracarboxylic dianhydride to the dimethyl sulfoxide solution, stir at room temperature for 4 to 6 hours, remove the solvent, and obtain the modified rubber component.

3. The modified polyurethane resin for synthetic leather according to claim 2, characterized in that: In step I, the number average molecular weight of the chloroether rubber is 5000 to 15000.

4. The modified polyurethane resin for synthetic leather according to claim 2, characterized in that: In step II, the inert gas is any one of argon, neon or helium.

5. The modified polyurethane resin for synthetic leather according to claim 1, characterized in that: The catalyst is any one of dibutyltin dilaurate, stannous octoate or dimorpholinyl diethyl ether; the small molecule chain extender is any one of ethylene glycol, 1,4-butanediol or 1,3-propylene glycol.

6. The modified polyurethane resin for synthetic leather according to claim 1, characterized in that: The preparation method of the flame retardant additive comprises the following steps: Under continuous nitrogen conditions, layered serpentine powder and 2,3-pyridinedicarboxylic anhydride are ultrasonically dispersed in N,N-dimethylformamide solution, treated at 70-90°C for 3-7h, and then flame retardant FRC-2 and esterification catalyst are added, the temperature is increased to 90-110°C, stirred for 4-8h, and the solid material is separated by centrifugation to obtain a flame retardant additive.

7. The modified polyurethane resin for synthetic leather according to claim 6, characterized in that: The average particle size of the layered serpentine powder is 5 μm.

8. The modified polyurethane resin for synthetic leather according to claim 6, characterized in that: The mass ratio of the layered serpentine powder to 2,3-pyridinedicarboxylic anhydride is 1:0.1-0.

4.

9. The modified polyurethane resin for synthetic leather according to claim 6, characterized in that: The esterification catalyst is any one of p-toluenesulfonic acid, aminosulfonic acid or trifluoromethanesulfonic acid.

10. A process for producing a modified polyurethane resin for synthetic leather as claimed in claim 1, characterized in that: The following steps are involved: Step 1: Add polytetrahydrofuran ether diol, hexamethylene diisocyanate and modified rubber component into a reaction kettle, stir and mix evenly, add a catalyst under the protection of a nitrogen atmosphere, turn on the heating, wait for the system temperature to reach 70-90°C, stir at a constant temperature for 1-3h, then add a small molecule chain extender, continue stirring for 1-2h, and obtain a polyurethane prepolymer; Step 2: Add flame retardant additives, triethylamine and deionized water to the polyurethane prepolymer, stir at high speed, and defoam naturally to obtain a modified polyurethane resin.

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