Polyurethane composition, polyurethane microporous foaming foam as well as preparation method and application of polyurethane microporous foaming foam

Abstract

The invention provides a polyurethane composition, polyurethane microporous foaming foam as well as a preparation method and application of the polyurethane microporous foaming foam. The polyurethane composition comprises a component A and a component B, wherein the component A comprises 100 parts of a polyol compound, 1-3 parts of a chain extender, 1.003-10 parts of an auxiliary agent and 0.03-5 parts of a catalyst; the component B is prepared from 14 to 26 parts of isocyanate; the polyol compound comprises a polymer polyol, a polyether polyol, a polyol containing phosphorus and nitrogen, and a polyol containing boron; the polyurethane composition provided by the invention avoids the release of toxic and harmful gases during combustion, has good environmental protection performance, and has the advantages of uniform dispersion, high flame retardant property, strong durability, small addition amount of the flame retardant, high flame retardant property, high flame retardancy, high flame retardant property, high flame retardancy, high flame retardancy, high flame retardancy, high flame retardancy, high flame retardancy, high flame retardancy, high flame retardancy, high flame retardancy, high flame retardancy, high flame retardancy, high flame retardancy, high flame retardancy, high flame retardancy, high flame retardancy, high flame retardancy, high flame retardancy, high flame retardancy, high flame retardancy and high flame retardancy, and the like. The flame retardant property and the overall stability of the polyurethane foam material are improved.

Description

Technical Field

[0001] The present invention relates to the technical field of polyurethane microporous foam cotton, in particular to a polyurethane composition, polyurethane microporous foam cotton and a preparation method and application thereof. Background Art

[0002] Polyurethane (PU), a polymer material with diverse product forms and excellent performance, is widely used in numerous fields, including energy, automotive, and sporting goods. PU is primarily an organic polymer synthesized through addition polymerization of polyols and isocyanates. Because the raw materials used to make PU are primarily derived from fossil resources, it is highly ignitable, burns rapidly, and is difficult to extinguish. The combustion process also releases toxic and harmful gases, making firefighting and escape difficult, severely limiting PU's application.

[0003] To improve the flame retardancy of polyurethane foam, a common method currently used is to incorporate large amounts of inorganic flame retardants during the preparation of polyurethane foam to slow the combustion reaction. These inorganic flame retardants primarily include magnesium hydroxide, aluminum hydroxide, and expandable graphite. However, even with these large amounts of inorganic flame retardants, the flame retardancy of polyurethane foam is limited. Furthermore, due to the poor compatibility of these inorganic flame retardants with the polymer and their tendency to migrate and precipitate from the matrix, the mechanical properties of the polyurethane foam material are reduced, the cell structure is damaged, and thermal insulation performance is compromised. Furthermore, during the continued use of polyurethane products, the various inorganic flame retardants in the polymer matrix become unstable, unevenly dispersed, and prone to migration, seriously affecting the flame retardancy and overall stability of the polyurethane foam material. Summary of the Invention

[0004] Aiming at the problems that the addition of inorganic flame retardants to existing polyurethane foam materials has the characteristics of large addition amount, poor compatibility, destruction of the foam pore structure, and influence on the flame retardancy and thermal insulation properties of the foam, the present invention provides a polyurethane composition, a polyurethane microporous foam, and a preparation method and application thereof.

[0005] In a first aspect, the present invention provides a polyurethane composition comprising component A and component B; The component A includes 100 parts of polyol compound, 1 to 3 parts of chain extender, 1.003 to 10 parts of auxiliary agent, and 0.03 to 5 parts of catalyst; The B component includes 14 to 26 parts of isocyanate; The polyol compounds include polymer polyols, polyether polyols, phosphorus-nitrogen-containing polyols and boron-containing polyols; The mass ratio of the polymer polyol, polyether polyol, phosphorus-nitrogen-containing polyol and boron-containing polyol is (35-45): (35-45): (4-10): (4-10).

[0006] Preferably, the hydroxyl value of the polymer polyol is 54.0-58.0 mgKOH / g; The hydroxyl value of the polyether polyol is 20.0-70.0 mgKOH / g.

[0007] Preferably, the molar equivalent ratio of the isocyanate group in the isocyanate to the hydroxyl group in the polyol compound is (0.9-1.3):1.

[0008] Preferably, the 1.003-10 parts of auxiliary agents include 1-5 parts of foaming agent and 0.03-5 parts of foam stabilizer; The isocyanate comprises 7-13 parts of toluene diisocyanate and 7-13 parts of isophorone diisocyanate; The catalyst includes at least one of a tertiary amine catalyst and an organometallic compound catalyst; The chain extender includes at least one of an alcohol chain extender and an amine chain extender; The foaming agent includes at least one of water, carbon dioxide, and hydrohaloolefins; The foam stabilizer includes at least one of silicone compounds such as organopolysiloxane, organopolysiloxane-polyoxyalkylene copolymer, polyalkenylsiloxane with polyoxyalkylene side chains, silicone-grease copolymer, anionic surfactants such as sodium dodecylbenzenesulfonate and sodium lauryl sulfate, polyether siloxane, and phenolic compounds.

[0009] In a second aspect, the present application provides a polyurethane microporous foam cotton prepared from the polyurethane composition described above.

[0010] In a third aspect, the present application provides a method for preparing the above-mentioned polyurethane microporous foam cotton, comprising the following steps: Mix components A and B at 0~10℃ and 1MPa~10MPa to form a prepolymer; The prepolymer is coated on the surface of a substrate and cured to obtain the polyurethane microporous foam cotton; the curing temperature is 80-130°C.

[0011] Preferably, the method for preparing the phosphorus-nitrogen polyol comprises the following steps: Under a protective atmosphere, 5-hydroxymethylfurfural, an alcohol amine, and a first organic solvent are uniformly mixed and subjected to a first reaction to obtain a first mixed solution; 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide and a second organic solvent are mixed evenly and then added to the first mixed solution, mixed evenly and subjected to a second reaction. After the second reaction is completed, a first post-treatment is performed to obtain the phosphorus-nitrogen-containing polyol.

[0012] Preferably, the molar ratio of the alcoholamine, the 5-hydroxymethylfurfural and the 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide is 1:(0.9-1):(0.8-1); The reaction temperature of the first reaction is 75~95°C, and the reaction time of the first reaction is 4~12h; The reaction temperature of the second reaction is 75-95° C., and the reaction time of the second reaction is 10-24 h; The first organic solvent and the second organic solvent both include alcohol solvents.

[0013] Preferably, the method for preparing the boron-containing polyol comprises the following steps: Under a protective atmosphere, heating glycerol to 90-120° C., adding boric acid, and carrying out a third reaction at a vacuum degree of 0.1-0.5 MPa to obtain the boron-containing polyol; The temperature of the third reaction is 140-160° C., and the time of the third reaction is 3-6 h; The molar ratio of glycerol to boric acid is (2-2.3):1.

[0014] In a fourth aspect, the present application provides an application of the polyurethane microporous foam cotton described above or the polyurethane microporous foam cotton prepared by the preparation method of the polyurethane microporous foam cotton described above in the fields of construction, electronic assembly, and automobile.

[0015] The polyurethane composition provided in this application has the following effects: 1) The polyether polyol contained in it helps to form high-density foam cells, and at the same time, no flame retardant that destroys the foam cell structure is added, which can effectively improve the thermal insulation performance of the polyurethane microcellular foam. The increase in soft chains in the polyol compound is conducive to the formation of foam with uniformly distributed cells. 2) The added phosphorus-nitrogen polyol and boron-containing polyol work together to form a phosphorus-nitrogen-boron synergistic flame retardant system, which improves the flame retardant properties of the polyurethane microcellular foam and avoids the release of toxic and harmful gases during combustion, thus having good environmental performance. At the same time, the boron-containing polyol and phosphorus-nitrogen polyol are stably present in the polymer without destroying the foam cell structure. They have uniform dispersion, high flame retardant properties, strong durability, low flame retardant addition, and no migration. They can also take into account the excellent properties of the polymer matrix itself, improving the flame retardant properties and overall stability of the polyurethane foam material. 3) The carbamate formed by the reaction of the polyol compound and the isocyanate constitutes the hard chain of the polymer, improving the mechanical properties of the polyurethane microcellular foam. DETAILED DESCRIPTION

[0016] In order to make the purpose, technical solutions and advantages of the present invention more clearly understood, the present invention is further described in detail below in conjunction with the embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not intended to limit the present invention.

[0017] In order to illustrate the technical solution of the present invention, specific embodiments are provided below.

[0018] In one embodiment of the present invention, the present application provides a polyurethane composition comprising component A and component B; The component A includes 100 parts of polyol compound, 1 to 3 parts of chain extender, 1.003 to 10 parts of auxiliary agent, and 0.03 to 5 parts of catalyst; The B component includes 14 to 26 parts of isocyanate; The polyol compounds include polymer polyols, polyether polyols, phosphorus-nitrogen-containing polyols and boron-containing polyols; The mass ratio of the polymer polyol, polyether polyol, phosphorus-nitrogen-containing polyol and boron-containing polyol is (35-45): (35-45): (4-10): (4-10).

[0019] The mass ratio of the polymer polyol, polyether polyol, phosphorus-nitrogen-containing polyol and boron-containing polyol is (35-45): (35-45): (4-10): (4-10). By adjusting the ratio of the polyether polyol to the polymer polyol, the content ratio of the soft chain is increased, thereby improving the flexibility of the molecular chain. In addition, the increase in the soft chain is conducive to the uniform distribution of the foam cells, helps to form high-density foam cells, improves the thermal insulation performance of the polyurethane microporous foam cotton material, and thus improves the overall performance of the material. The mass ratio of the polymer polyol, polyether polyol, phosphorus-nitrogen-containing polyol and boron-containing polyol is (35-45): (35-45): (4-10): (4-10), which can also be understood as including 35-45 parts of polymer polyol, 35-45 parts of polyether polyol, 4-10 parts of phosphorus-nitrogen-containing polyol and 4-10 parts of boron-containing polyol in 100 parts of polyol compounds. The number of parts of polyether polyol in 100 parts of polyol compounds can be 35 parts, 37 parts, 39 parts, 40 parts, 41 parts, 42 parts, 43 parts, 45 parts, etc. Similarly, the number of polymer polyols in 100 parts of polyol compounds can be 35 parts, 37 parts, 39 parts, 40 parts, 41 parts, 42 parts, 43 parts, 45 parts, etc.; the number of phosphorus-nitrogen polyols in 100 parts of polyol compounds can be 4 parts, 5 parts, 6 parts, 7 parts, 8 parts, 9 parts, 10 parts, etc., and the number of boron-containing polyols in 100 parts of polyol compounds can be 4 parts, 5 parts, 6 parts, 7 parts, 8 parts, 9 parts, 10 parts, etc.

[0020] The polyol compound and the isocyanate react to form the carbamate which constitutes the hard chain of the polymer and improves the mechanical properties of the polyurethane microporous foam.

[0021] The addition of phosphorus-nitrogen polyols can improve the tensile strength of polyurethane microcellular foam.

[0022] Boron-containing polyols work synergistically with phosphorus-nitrogen-containing polyols. The B element in the flame retardant accelerates the formation of a glassy isolation layer. The NP element has the function of promoting the dehydration of the material into carbon. Boron-containing polyols work synergistically with phosphorus-nitrogen-containing polyols to jointly promote the densification of the carbon layer, forming a phosphorus-nitrogen-boron synergistic flame retardant system, which enhances the integrity and continuity of the carbon layer. All elements show good synergistic thermal insulation and flame retardant effects, thereby enhancing the barrier formed in the condensed phase.

[0023] By adding boron-containing polyols and phosphorus-nitrogen-containing polyols, the polyurethane microporous foam cotton prepared has an improved limiting oxygen index and a flame retardant grade of up to V-0, thereby significantly improving the flame retardant properties of the polyurethane microporous foam cotton, avoiding the release of toxic and harmful gases during combustion, and having good environmental performance; compared with the traditional method of directly adding inorganic flame retardants, the polyurethane microporous foam cotton provided by the present application, by adding boron-containing polyols and phosphorus-nitrogen-containing polyols, forms a phosphorus-nitrogen-boron synergistic flame retardant system, and does not have the problems of poor compatibility of inorganic flame retardants with polymers, easy migration and precipitation from the matrix, which causes the mechanical properties of the polyurethane foam material to deteriorate and the pore structure to be destroyed. The boron-containing polyols and phosphorus-nitrogen-containing polyols with flame retardant effects are stably present in the polymer, and have the characteristics of uniform dispersion, high flame retardant performance, strong durability, small amount of flame retardant addition, no migration, and can also take into account the excellent properties of the polymer matrix itself, thereby improving the flame retardant properties and overall stability of the polyurethane foam material.

[0024] The polyurethane composition provided in this application has the following effects: 1) The polyether polyol contained in the composition helps form high-density foam cells, and at the same time, no inorganic flame retardants that destroy the foam cell structure are added, which can effectively improve the thermal insulation performance of the polyurethane microcellular foam. The increase in soft chains in the polyol compound is conducive to the formation of foam with uniformly distributed cells. 2) The added phosphorus-nitrogen polyol and boron-containing polyol synergistically form a phosphorus-nitrogen-boron synergistic flame retardant system, which improves the flame retardancy of the polyurethane microcellular foam and avoids the release of toxic and harmful gases during combustion, thus having good environmental performance. At the same time, the boron-containing polyol and phosphorus-nitrogen polyol are stably present in the polymer without destroying the foam cell structure. The composition has uniform dispersion, high flame retardancy, strong durability, low flame retardant addition, and no migration. It also takes into account the excellent properties of the polymer matrix itself, improving the flame retardancy and overall stability of the polyurethane foam material. 3) The carbamate formed by the reaction of the polyol compound and the isocyanate constitutes the hard chain of the polymer, improving the mechanical properties of the polyurethane microcellular foam.

[0025] In some embodiments, the 1.003-10 parts of auxiliary agent include 1-5 parts of foaming agent and 0.03-5 parts of foam stabilizer; The foaming agent includes at least one of water, carbon dioxide, and hydrohaloolefins; The foam stabilizer includes at least one of silicone compounds such as organopolysiloxane, organopolysiloxane-polyoxyalkylene copolymer, polyalkenylsiloxane with polyoxyalkylene side chains, silicone-grease copolymer, anionic surfactants such as sodium dodecylbenzenesulfonate and sodium lauryl sulfate, polyether siloxane, and phenolic compounds.

[0026] The foaming agent promotes foaming, and the amount of the foaming agent can be 1 part, 2 parts, 3 parts, 4 parts, 5 parts, etc. The amount of the foam stabilizer can be 0.03 parts, 0.1 parts, 1 part, 2 parts, 3 parts, 4 parts, 5 parts, etc. The foam stabilizer promotes stable foaming.

[0027] In some embodiments, the isocyanate comprises 7-13 parts toluene diisocyanate and 7-13 parts isophorone diisocyanate. This facilitates the reaction between the isocyanate and the polyol compound, resulting in a polyurethane microporous foam with uniform pore distribution and a high-density cell structure, thereby improving the thermal insulation, mechanical properties, and flame retardancy of the polyurethane material.

[0028] In some embodiments, in the isocyanate, the molar ratio of the toluene diisocyanate to the isophorone diisocyanate is (0.8-1.5):1.

[0029] Specifically, controlling the mass ratio of toluene diisocyanate to isophorone diisocyanate within the range of (0.8-1.5):1 further facilitates the reaction between the isocyanate and the polyol compound, resulting in a polyurethane microporous foam with uniform pore distribution and a high-density cell structure, resulting in a polyurethane material with improved thermal insulation, mechanical, and flame retardancy. Specifically, the molar ratio of toluene diisocyanate to isophorone diisocyanate in the isocyanate can be 0.8:1, 0.9:1, 1:1, 1.2:1, 1.3:1, 1.5:1, or the like.

[0030] In some embodiments, the catalyst includes at least one of a tertiary amine catalyst and an organometallic compound catalyst.

[0031] The tertiary amine catalyst includes at least one of triethylenediamine, bis(dimethylaminoethyl) ether, N,N-dimethylcyclohexylamine, tetramethylbutanediamine, and dimethylethanolamine; The organometallic compound catalyst includes at least one of stannous octoate, dibutyltin dilaurate, and zinc isooctanoate.

[0032] In some embodiments, the chain extender includes at least one of an alcohol chain extender and an amine chain extender.

[0033] The molecular weight of the alcohol chain extender is 80-450, and the functionality is 2-5.

[0034] The alcohol chain extender includes at least one of 1,4-butanediol, diethylene glycol, ethylene glycol, trimethylolpropane, pentaerythritol, and low molecular weight polyether polyol.

[0035] The functionality of amine chain extenders is 3 to 4.

[0036] The amine chain extender includes at least one of diethyltoluenediamine, triethanolamine, diethanolamine, and ethanolamine.

[0037] In some embodiments, the polymer polyol has a hydroxyl value of 54.0 to 58.0 mgKOH / g; The hydroxyl value of the polyether polyol is 20.0-70.0 mgKOH / g.

[0038] Specifically, the hydroxyl value of the polymer polyol and the hydroxyl value of the polyether polyol are limited to the above range, the content of the soft chain in the polyol is controlled, the content ratio of the soft chain is increased, the flexibility of the molecular chain is improved, and the polyurethane foam is given flexibility and elasticity; at the same time, the increase in soft chains is conducive to the formation of uniform distribution of bubbles, which helps to form high-density bubbles, improves the thermal insulation performance of the material, and thus improves the overall performance of the material.

[0039] In some embodiments, the polymer polyol has a hydroxyl value of 54.0-58.0 mgKOH / g, a viscosity of 400-650 mPa·s at 25° C., an acid value ≤0.05 mgKOH / g, a moisture content ≤0.05%, a pH value of 5.5-7.5, and a color APHA of ≤30.

[0040] In some embodiments, the polyether polyol includes polypropylene glycol with a hydroxyl value of 26-30 mgKOH / g.

[0041] In some embodiments, the molar equivalent ratio of the isocyanate group in the isocyanate to the hydroxyl group in the polyol compound is (0.9-1.3):1.

[0042] Specifically, the synthesis of polyurethane mainly relies on the reaction between -NCO in isocyanate and -OH in polyol compounds. Controlling the molar equivalent ratio of -NCO and -OH in the range of (0.9 to 1.3):1 determines the number of urethane bonds, forms an ideal cross-linked network structure, improves the degree of cross-linking of polyurethane, forms a polyurethane material with uniform pore distribution and high-density foam structure, and improves the thermal insulation and mechanical properties of polyurethane.

[0043] In some embodiments, in the polyol compound, the mass ratio of the phosphorus-nitrogen-containing polyol to the boron-containing polyol is (0.4-2.5):1.

[0044] Controlling the mass ratio of the phosphorus-nitrogen polyol to the boron-containing polyol within the above range is beneficial to the synergistic effect of the phosphorus-nitrogen polyol and the boron-containing polyol, and improving the flame retardant properties of the polyurethane microporous foam.

[0045] In some preferred embodiments, the mass ratio of the phosphorus-nitrogen-containing polyol to the boron-containing polyol is 1:1.

[0046] In a second aspect, the present application provides a polyurethane microporous foam cotton prepared from the polyurethane composition described above.

[0047] The polyurethane microporous foam cotton provided in the present application has the following effects: it has a structure with uniformly distributed foam cells and high-density foam cells, and has good flame retardant properties, thermal insulation properties and mechanical properties.

[0048] In a third aspect, the present application provides a method for preparing the above-mentioned polyurethane microporous foam cotton, comprising the following steps: Mix components A and B at 0~10℃ and 1MPa~10MPa to form a prepolymer; The prepolymer is coated on the surface of a substrate and cured to obtain the polyurethane microporous foam cotton; the curing temperature is 80-130°C.

[0049] The preparation method of the polyurethane microporous foam cotton provided in the present application is to first mix component A and component B evenly to form a prepolymer, and then coat the prepolymer on the surface of a substrate to solidify and form it to obtain the polyurethane microporous foam cotton. The preparation method is simple, and the obtained polyurethane microporous foam cotton has good thermal insulation performance, high flame retardancy, and good mechanical properties. At the same time, the polyurethane foam has the characteristics of uniform pore distribution and high pore density.

[0050] The curing temperature may be in the range of 80-90°C, 90-100°C, 100-115°C, 115-125°C, or 125-130°C.

[0051] In some embodiments, the curing time is 5s to 20s.

[0052] In some embodiments, the method for preparing the phosphorus-nitrogen polyol comprises the following steps: Under a protective atmosphere, 5-hydroxymethylfurfural, an alcohol amine, and a first organic solvent are uniformly mixed and subjected to a first reaction to obtain a first mixed solution; 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide and a second organic solvent are mixed evenly and then added to the first mixed solution, mixed evenly and subjected to a second reaction. After the second reaction is completed, a first post-treatment is performed to obtain the phosphorus-nitrogen-containing polyol.

[0053] The abbreviation of 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide is DOPO.

[0054] Specifically, 5-hydroxymethylfurfural, alcoholamine and a first organic solvent are mixed evenly, and then a first reaction is carried out to obtain a first mixed solution, wherein the first reaction can be a first reflux reaction. The reaction principle of 5-hydroxymethylfurfural and alcoholamine is that the aldehyde group in 5-hydroxymethylfurfural reacts with the amine group in the alcoholamine to generate compound 1, which is a compound shown in Formula 1. Compound 1 then undergoes a second reaction with 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide to generate compound 2, which is a compound shown in Formula 2. It should be noted that the second reaction can be a reflux reaction, and compound 2 is the product phosphorus-nitrogen polyol.

[0055] , .

[0056] The reaction equation of 5-hydroxymethylfurfural and ethanolamine is as follows: ; The reaction equation of compound 1 with 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide is as follows: .

[0057] 5-Hydroxymethylfurfural contains a furan ring, an oxygen-containing five-membered heterocyclic structure with similar rigidity and aromaticity to a benzene ring, but with higher polarity. Introducing the furan ring into polyurethane enhances molecular chain rigidity, increasing the tensile strength of the polyurethane microporous foam. Combined with the soft segment of the polyether polyol, this ring promotes polymerization and microphase separation, resulting in a polyurethane microporous foam with both excellent tensile strength and improved compressive strength.

[0058] In some embodiments, the molar ratio of the alcoholamine, the 5-hydroxymethylfurfural, and DOPO is 1:(0.9-1):(0.8-1).

[0059] Specifically, 5-hydroxymethylfurfural, ethanolamine and DOPO are used as reactants, and the molar ratio of ethanolamine, 5-hydroxymethylfurfural and DOPO is controlled in the range of 1: (0.9-1): (0.8-1). The obtained phosphorus-nitrogen polyol has strong hydroxyl reactivity.

[0060] In some embodiments, the reaction temperature of the first reaction is 75-95° C., and the reaction time of the first reaction is 4-12 h; The reaction temperature of the second reaction is 75-95° C., and the reaction time of the second reaction is 10-24 h; The first organic solvent and the second organic solvent both include alcohol solvents.

[0061] Specifically, the first reaction temperature is 75-95°C, and the reaction time of the first reaction is within the range of 4-12 hours, which facilitates the reaction of 5-hydroxymethylfurfural with alcoholamine to produce compound 1. If the first reaction temperature is lower than 75-95°C, 5-hydroxymethylfurfural and alcoholamine do not react. If the first reaction temperature is higher than 75-95°C, side reactions and by-products increase.

[0062] The second reaction temperature is 75-95°C, and the reaction time is 10-24 hours, which helps compound 1 react with 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide to form a phosphorus-nitrogen polyol. If the second reaction temperature is lower than 75-95°C, compound 1 and 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide will not react. If the second reaction temperature is higher than 75-95°C, side reactions and the amount of by-products will increase.

[0063] The first reaction temperature can be 75°C, 75°C, 80°C, 82°C, 85°C, 86°C, 88°C, 90°C, 92°C, 95°C, etc.; the first reaction time can be 4h, 5h, 6h, 7h, 8h, 9h, 10h, 11h, 12h, etc.

[0064] The temperature of the second reaction can be 75°C, 75°C, 80°C, 82°C, 85°C, 86°C, 88°C, 90°C, 92°C, 95°C, etc.; the time of the second reaction can be 10h, 12h, 13h, 15h, 16h, 20h, 22h, 23h, 24h, etc.

[0065] In some preferred embodiments, the first organic solvent includes ethanol, propanol, butanol, isopropanol, etc. The second organic solvent includes ethanol, propanol, butanol, isopropanol, etc.

[0066] In some preferred embodiments, the alcoholamine includes ethanolamine, isopropanolamine, and n-propanolamine.

[0067] In some preferred embodiments, the first organic solvent is anhydrous ethanol.

[0068] In some embodiments, performing a first post-treatment after the second reaction to obtain the phosphorus-nitrogen polyol comprises the following steps: obtaining a second mixed solution after the second reaction, filtering the second mixed solution to obtain a solid product, and washing and drying the solid product to obtain the phosphorus-nitrogen polyol.

[0069] Specifically, the second mixed solution is first cooled to 20-40° C., and then filtered to obtain a solid product. The solid product is washed at least once with a detergent, and then dried to obtain the phosphorus-nitrogen polyol. The detergent includes an alcohol solvent, and the detergent is preferably ethanol.

[0070] In some embodiments, the method for preparing the boron-containing polyol comprises the following steps: Under a protective atmosphere, glycerol is heated to 90-120° C., boric acid is added, and a third reaction is carried out at a vacuum degree of 0.1-0.5 MPa. After the third reaction is completed, the boron-containing polyol is obtained.

[0071] Specifically, when preparing boron-containing polyols, boric acid and glycerol are used as reactants. The boron-containing polyols prepared can cooperate with phosphorus-nitrogen polyols. The B element accelerates the formation of a glassy isolation layer, the NP element has the function of promoting the dehydration of the material into carbon, and the furan ring and the boron compound jointly promote the densification of the carbon layer. All elements show good synergistic heat insulation and flame retardant effects, forming a phosphorus-nitrogen-boron synergistic flame retardant system, which enhances the integrity and continuity of the carbon layer, thereby enhancing the barrier formed in the condensed phase and improving the flame retardancy of the polyurethane microporous foam.

[0072] In the process of preparing polyurethane microporous foam cotton, if phosphorus-containing polyol is added alone without adding phosphorus-nitrogen polyol, the limiting oxygen index LOI of the obtained polyurethane microporous foam cotton is expected to reach 20-30%. The polyurethane microporous foam cotton provided in this application is added with phosphorus-containing polyol and phosphorus-nitrogen polyol at the same time, and the limiting oxygen index LOI is ≥30%, UL-94 V-0 grade, and the heat release rate is significantly reduced.

[0073] In some embodiments, the temperature of the third reaction is 140-160° C., and the time of the third reaction is 3-6 h; The molar ratio of glycerol to boric acid is (2-2.3):1.

[0074] Specifically, the third reaction temperature is within the range of 140-160°C, and the third reaction time is within the range of 3-6 hours, which facilitates the reaction of boric acid and glycerol to form a boron-containing polyol. If the reaction temperature is below 140°C, the reaction is incomplete and the reaction rate is slow. If the reaction temperature is above 160°C, side reactions and byproducts increase. The fourth reaction temperature can be 140°C, 142°C, 145°C, 147°C, 149°C, 150°C, 155°C, 158°C, 160°C, etc.

[0075] The molar ratio of glycerol to boric acid is (2~2.3):1, with 1 mol of boric acid, which is conducive to the complete reaction of boric acid and reduces costs.

[0076] Glycerol and boric acid undergo a third reaction to obtain a colorless, transparent, viscous product, which is a boron-containing polyol.

[0077] The reaction equation of glycerol and boric acid is as follows: .

[0078] In some embodiments, the protective atmosphere refers to an atmosphere of a protective gas, and the protective gas includes nitrogen and a rare gas.

[0079] In some preferred embodiments, the shielding gas is nitrogen.

[0080] In a fourth aspect, the present application provides an application of the polyurethane microporous foam cotton described above or the polyurethane microporous foam cotton prepared by the preparation method of the polyurethane microporous foam cotton described above in the fields of construction, electronic assembly, and automobile.

[0081] The polyurethane microporous foam provided in this application, or the polyurethane microporous foam prepared by the preparation method thereof, has high resilience, good mechanical properties, high flame retardancy, and good thermal insulation. It can be used in the construction field as a thermal insulation material; in the electronic assembly field as a sealing material, cushioning material, sound-absorbing material, and thermal insulation material; and in the automotive field as a cushioning material and thermal insulation material.

[0082] The present invention is further described below with reference to the following examples.

[0083] Example 1 S1: Preparation of phosphorus-nitrogen polyols, the preparation steps are as follows: In a four-necked flask, 206 g of 5-hydroxymethylfurfural (molecular weight 126.11 g / mol, calculated as 1.63 mol) and 100 g of ethanolamine (molecular weight 61.08 g / mol, calculated as 1.63 mol) were dissolved in anhydrous ethanol (200 mL). The atmosphere was then replaced with nitrogen and, under a nitrogen atmosphere, stirred and heated to 80°C for a first reflux reaction of 6 h. Subsequently, a mixed solution 1 consisting of anhydrous ethanol and DOPO (353 g of DOPO (molecular weight 216.17 g / mol, calculated as 1.63 mol)) (300 mL) was added, and a second reflux reaction was continued at 80°C for 12 h. After the second reflux reaction, a first mixed solution was obtained. The first mixed solution was cooled to room temperature and filtered to obtain a filtrate, which was then dried to yield the phosphorus-nitrogen polyol.

[0084] The DOPO is 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide, purchased from Shanghai Aladdin Biochemical Technology Co., Ltd. The molar ratio of ethanolamine, 5-hydroxymethylfurfural, and DOPO is 1:1:1.

[0085] S2: Preparation of boron-containing polyols, the preparation steps are as follows: In a four-necked flask, 100 g of glycerol (molecular weight 92.094 g / mol, calculated as 1.09 mol) was added. The atmosphere was replaced with nitrogen and heated to 110°C with stirring under a nitrogen atmosphere. 33.50 g of boric acid (molecular weight 61.83 g / mol, calculated as 0.54 mol) was then added dropwise. The vacuum was adjusted to 0.1 MPa, and the temperature was raised to 150°C with stirring for a third reaction. The third reaction lasted for 3 hours, yielding a colorless, transparent, viscous liquid product, a boron-containing polyol. The molar ratio of glycerol to boric acid was 2:1.

[0086] S3: Obtain component A Component A: 100 parts of polyol compound, 2.5 parts of foaming agent, 3 parts of chain extender, 1 part of catalyst, and 3 parts of foam stabilizer.

[0087] Among them, 100 parts of polyol compounds are composed of 40 parts of polymer polyol, 40 parts of polyether polyol, 10 parts of phosphorus-nitrogen-containing polyol and 10 parts of boron-containing polyol.

[0088] The polymer polyol was purchased from Chengdu Zealandia Technology Co., Ltd., Wanhua Chemical, with the brand name LEP-5631D and a hydroxyl value of 55.5 mgKOH / g. The polyether polyol was purchased from Nantong Yixun Chemical Co., Ltd., with the product name polypropylene glycol PPG-4000 and a hydroxyl value of 28 mgKOH / g. The phosphorus-nitrogen-containing polyol was prepared in step S1 above. The boron-containing polyol was prepared in step S2 above.

[0089] The blowing agent is selected from water.

[0090] The chain extender was purchased from Xinjiang Guotai Xinhua Chemical Co., Ltd. with the brand name BDO, and the product was 1,4-butanediol.

[0091] The catalyst consists of 0.5 parts of stannous octoate and 0.5 parts of aliphatic tertiary amine, wherein the stannous octoate is purchased from Nanjing Chemical Reagent Co., Ltd., and the aliphatic tertiary amine is purchased from Evonik Japan Co., Ltd., with the brand name DABCO33LSI.

[0092] The foam stabilizer was purchased from Dow Corning Company under the brand name SZ-1136, and the product is organic silicone.

[0093] S4: Obtaining component B Component B: 10.5 parts of toluene diisocyanate (TDI), 10.5 parts of isophorone diisocyanate (IPDI).

[0094] Among them, toluene diisocyanate was purchased from Wanhua Chemical Company with the brand name WANNATE®TDI-80; isophorone diisocyanate was purchased from industrially pure Guangdong Haoyi Chemical Technology Co., Ltd.

[0095] S5: Prepare polyurethane microporous foam cotton, the steps are as follows: S51: Component A obtained in step S3 and component B obtained in step S4 are placed in a container, and stirred at 0°C to 10°C and 1 MPa to 10 MPa for 5 to 15 minutes until they are uniformly stirred to form a prepolymer.

[0096] S52: The prepolymer obtained in step S51 is conveyed via a pipeline to a coating machine, and the prepolymer is coated on a substrate by the coating machine. The prepolymer is preheated during the process of conveying the prepolymer via the pipeline to the coating machine. The substrate coated with the prepolymer is placed in a curing oven for curing and forming to form a polyurethane microporous foam. The substrate is PET.

[0097] When the substrate coated with the prepolymer is placed in a curing oven for curing and molding, the curing and molding temperature is 80° C. to 130° C., and the curing time is 5 seconds to 20 seconds.

[0098] Examples 2 to 16 and Comparative Examples 1 to 3 Examples 2-16 and Comparative Examples 1-3 follow most of the same steps as Example 1, except that the content of the polymer polyol, polyether polyol, phosphorus-nitrogen-containing polyol, and boron-containing polyol in Component A varies; and the content of TDI and IPDI in Component B varies, as shown in Table 1. The molar equivalent ratio of isocyanate groups to hydroxyl groups in Example 10 is 1:1.3, the molar equivalent ratio of isocyanate groups to hydroxyl groups in Example 11 is 1:0.9, and the molar equivalent ratio of isocyanate groups to hydroxyl groups in Example 12 is 1:0.8.

[0099] Example 17 Most of the steps in Example 17 are the same as those in Example 1, except that in step S1, when preparing phosphorus-nitrogen polyol in Example 17, the first reflux reaction temperature is 100°C, and the second reflux reaction temperature is 100°C. The rest is the same as in Example 1.

[0100] Example 18 Most of the steps in Example 18 are the same as those in Example 1, except that in step S1, when preparing phosphorus-nitrogen polyols in Example 18, the first reflux reaction temperature is 95°C, and the second reflux reaction temperature is 95°C. The rest is the same as in Example 1.

[0101] Example 19 Most of the steps in Example 19 are the same as those in Example 1, except that in step S1, when preparing phosphorus-nitrogen polyols in Example 19, the first reflux reaction temperature is 75°C, and the second reflux reaction temperature is 75°C. The rest is the same as in Example 1.

[0102] Example 20 Most of the steps in Example 20 are the same as those in Example 1, except that in step S1, when preparing the phosphorus-nitrogen polyol in Example 20, the mass of 5-hydroxymethylfurfural added is 186 g, the mass of DOPO in the mixed solution 1 is 284 g, and the molar ratio of ethanolamine, 5-hydroxymethylfurfural and DOPO is 1:0.9:0.8.

[0103] Example 21 Most of the steps in Example 21 are the same as those in Example 1, except that in step S2, the temperature of the third reaction in preparing the boron-containing polyol is 170° C., and the rest are the same as in Example 1.

[0104] Comparative Example 4~Comparative Example 5 Comparative Examples 4 and 5 are similar to Example 1 in most of the steps, except that the content of polymer polyol, polyether polyol, phosphorus-nitrogen-containing polyol, and boron-containing polyol in component A in Table 1 is different; the content of TDI and IPDI in component B is different. In addition, component A in Comparative Examples 4 and 5 also includes DOPO, with 40 parts of DOPO in Comparative Example 4 and 20 parts of DOPO in Comparative Example 5. The rest is the same as Example 1.

[0105] Table 1 Performance Testing The polyurethane microporous foamed cottons prepared in the above-mentioned embodiments and comparative examples were used as samples to conduct the following tests.

[0106] 1) Resilience: The sample's resilience was measured at room temperature using a universal tensile testing machine. According to ASTM D-412, the sample was stretched at a speed of 50 mm / min for five cycles, and the deformation recovery rate R (%) was calculated using the following formula: R= Where R represents the deformation recovery rate, L0 represents the original length of the polyurethane microporous foam, L1 represents the length after the external force is applied, and L2 represents the length after the external force is removed. Enter the R value in Table 2. The R value is the rebound rate.

[0107] 2) Tensile strength According to the GB / T6344-2008 test standard, the polyurethane microporous foam cotton is cut into dumbbell-shaped specimens using a slicer (take the "1" type dumbbell specimen in the standard), the distance between the upper and lower clamps is set to 62.5mm, the sample is placed between the upper and lower clamps of the tensile testing machine, and the tensile rate is adjusted to 500mm / min. The number of samples should meet the requirement that at least 5 are broken within the gauge length, and at least 5 specimens are required.

[0108] 3) Elongation at break According to the GB / T6344-2008 test standard, the polyurethane microporous foam cotton is cut into dumbbell-shaped specimens using a slicer (take the "1" type dumbbell specimen in the standard), the distance between the upper and lower clamps is set to 62.5mm, the sample is placed between the upper and lower clamps of the tensile testing machine, and the tensile rate is adjusted to 500mm / min. The number of samples should meet the requirement that at least 5 are broken within the gauge length, and at least 5 specimens are required.

[0109] 4) Permanent compression set According to the test standard of ASTM D3574, the polyurethane microporous foam was cut into 50×50mm, stacked to a thickness of about 10mm (multi-layer sample stacking test is allowed), and compressed to 70% using a compression jig. The sample was placed at room temperature (25-30℃) and maintained for 24 hours. After the test, the sample was allowed to recover for 30 minutes before the sample thickness was tested and the compression residual deformation value was calculated.

[0110] 5) Limiting Oxygen Index Test (LOI) According to the standard ASTM D2863-97, the synthesized polyurethane samples were tested using a limiting oxygen index tester. The sample size was 100 mm × 10 mm × 4 mm. All samples were tested at least five times, and the average value was taken.

[0111] 6) UL-94 vertical burning test (UL-94) According to the standard ASTM D3801-2010, the corresponding test was carried out on a vertical combustion test machine with a sample size of 130 mm × 13 mm × 3 mm.

[0112] 7) Thermal conductivity According to the standard GB / T10295-2008, the thermal conductivity test sample size is 200mm×200mm×25mm, the upper plate temperature of the instrument is 2℃, the lower plate temperature is 18℃, the average temperature is 10℃, and the temperature difference is 16℃.

[0113] The above test results are shown in Table 2.

[0114] Table 2 As can be seen from Table 1, compared with Examples 1-3 and Comparative Examples 6-7, the content of polymer polyol or polyether polyol in the polyol compound is relatively small, and the obtained polyurethane has low tensile strength, large permanent compression deformation, low rebound rate, high thermal conductivity, and poor thermal insulation effect. This indicates that when the mass ratio of the polymer polyol, polyether polyol, phosphorus-nitrogen-containing polyol and boron-containing polyol in the polyol compound is within the range of (35-45): (35-45): (4-10): (4-10), it is conducive to the formation of polyurethane microporous foam cotton with uniform pore distribution and high-density pore structure, which has good mechanical properties and thermal insulation effect.

[0115] Comparing Example 1 with Comparative Examples 1, 2, and 3, in Comparative Example 3, no phosphorus-nitrogen polyol and boron-containing polyol were added, and the resulting polyurethane microporous foam had an extremely low limiting oxygen index and poor flame retardancy; in Comparative Example 1, phosphorus-nitrogen polyol was added, and although the polyurethane microporous foam obtained in Comparative Example 1 had good mechanical properties and thermal insulation properties, it had a low limiting oxygen index and a UL-94 combustion rating of V-1; in Comparative Example 2, boron-containing polyol was added, and the resulting polyurethane microporous foam had low tensile strength, a low limiting oxygen index, and a UL-94 combustion rating of V-1, indicating that the addition of phosphorus-nitrogen polyol and boron-containing polyol to the polyol compound is effective. The mass ratio of the polymer polyol, polyether polyol, phosphorus-nitrogen polyol and boron-containing polyol is (35~45): (35~45): (4~10): (4~10). The phosphorus-nitrogen polyol and the boron-containing polyol have a synergistic effect to form a phosphorus-nitrogen-boron synergistic flame retardant system, thereby improving the flame retardant properties of the polyurethane microporous foam cotton. At the same time, the boron-containing polyol and the phosphorus-nitrogen polyol are stably present in the polymer without destroying the pore structure. They have uniform dispersion, high flame retardant properties, strong durability, a small amount of flame retardant added, and no migration. In addition, they can also take into account the excellent properties of the polymer matrix itself, thereby improving the mechanical properties of the polyurethane microporous foam cotton.

[0116] Comparing Example 1 with Comparative Examples 4 and 5, no phosphorus-nitrogen-containing polyol and boron-containing polyol were added to Comparative Examples 4 and 5, but DOPO was added. The obtained polyurethane had low mechanical properties, low limiting oxygen index, high flame retardancy, and poor thermal insulation performance.

[0117] Comparing Examples 6-8 with Comparative Example 9 and Comparative Example 8, too much phosphorus-nitrogen polyol was added to the polyol compound, and too much boron-containing polyol was added. Due to the high molar content of the added hydroxyl group, in order to ensure that the molar equivalent ratio of -NCO to -OH remained unchanged at 1.1, the corresponding number of isocyanates added was high, and the obtained polyurethane had a low elongation at break, a high compression deformation rate, and a low rebound rate, indicating that too much phosphorus-nitrogen polyol and boron-containing polyol added would increase the mechanical properties of the polyurethane microporous foam cotton and make it easier to break; in Comparative Example 9, too few phosphorus-nitrogen polyol and boron-containing polyol were added to the polyol compound, and the obtained polyurethane microporous foam cotton had a low limiting oxygen index and a low flame retardant grade. It is described that phosphorus-nitrogen-containing polyol and boron-containing polyol are added simultaneously to the polyol compound, and the mass ratio of the polymer polyol, polyether polyol, phosphorus-nitrogen-containing polyol and boron-containing polyol is (35~45):(35~45):(4~10):(4~10). The obtained polyurethane microporous foam cotton has good flame retardant properties.

[0118] Comparing Examples 9-10 with Example 11 and Comparative Example 10, the molar ratio of the isocyanate group to the hydroxyl group in Example 11 is less than the range of (0.9~1.3):1, and the tensile strength and the rebound rate are low; the molar ratio of the isocyanate group to the hydroxyl group in Comparative Example 10 is greater than the range of (0.9~1.3):1, and the number of isocyanate parts in the polyurethane is greater than 14~26 parts, and the obtained polyurethane has low tensile strength, high permanent compression deformation, low elongation at break, low rebound rate, and high thermal conductivity, indicating that the molar ratio of the isocyanate group to the hydroxyl group is within the range of (0.9~1.3):1, which is helpful to obtain a polyurethane microporous foam with high tensile strength, low permanent compression deformation, high rebound rate, high elongation at break, and good thermal insulation performance.

[0119] Comparing Examples 12-13 and 16 with Examples 14-15, in Examples 14-15, even though the molar equivalent ratio of isocyanate group to hydroxyl group is in the range of (0.9-1.3):1, the toluene diisocyanate is not in the range of 7-13 parts, and the overall mechanical properties of the obtained polyurethane microporous foam are poor.

[0120] Comparing Examples 1, 18, and 19 with Example 17, when preparing phosphorus-nitrogen polyols, the temperature of the first reaction is higher than 75~95°C, and the temperature of the second reaction is higher than 75~95°C. The reaction temperature is too high, there are many side reactions, the impurity content is high, flame retardant path defects, lattice defects, and the resulting polyurethane microporous foam has a low limiting oxygen index and poor flame retardant properties. This indicates that when the temperature of the first reaction is in the range of 75~95°C and the temperature of the second reaction is in the range of 75~95°C, there are fewer side reactions, and the generated phosphorus-nitrogen polyols have fewer impurities, which can work together with the boron-containing polyols to effectively improve the flame retardant properties of the polyurethane microporous foam.

[0121] Comparing Example 1 and Example 21, when preparing the boron-containing polyol, the temperature of the third reaction is higher than 140~160°C, the reaction temperature is too high, there are many side reactions, the impurity content is high, flame retardant path defects, lattice defects, and the resulting polyurethane microporous foam cotton has a low limiting oxygen index and poor flame retardant properties; this indicates that when the temperature of the third reaction is within the range of 140~160°C, the generated boron-containing polyol has few impurities, and can synergize with the phosphorus-nitrogen polyol to effectively improve the flame retardant properties of the polyurethane microporous foam cotton.

[0122] The above embodiments are intended only to illustrate the technical solutions of the present invention and are not intended to limit them. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they may still modify the technical solutions described in the aforementioned embodiments or replace some of the technical features therein with equivalents. However, such modifications or replacements do not deviate from the spirit and scope of the technical solutions of the various embodiments of the present invention and are intended to be included within the scope of protection of the present invention.

Claims

1. A polyurethane composition, characterized in that It includes component A and component B; The component A includes 100 parts of polyol compound, 1 to 3 parts of chain extender, 1.003 to 10 parts of auxiliary agent, and 0.03 to 5 parts of catalyst; The B component includes 14 to 26 parts of isocyanate; The polyol compounds include polymer polyols, polyether polyols, phosphorus-nitrogen-containing polyols and boron-containing polyols; The mass ratio of the polymer polyol, polyether polyol, phosphorus-nitrogen-containing polyol and boron-containing polyol is (35-45): (35-45): (4-10): (4-10).

2. The polyurethane composition according to claim 1, characterized in that The hydroxyl value of the polymer polyol is 54.0 to 58.0 mgKOH / g; The hydroxyl value of the polyether polyol is 20.0-70.0 mgKOH / g.

3. The polyurethane composition according to claim 1, characterized in that The molar equivalent ratio of the isocyanate group in the isocyanate to the hydroxyl group in the polyol compound is (0.9-1.3):

1.

4. The polyurethane composition according to claim 1, characterized in that The auxiliary agent includes 1-5 parts of foaming agent and 0.03-5 parts of foam stabilizer; The isocyanate comprises 7-13 parts of toluene diisocyanate and 7-13 parts of isophorone diisocyanate; The catalyst includes at least one of a tertiary amine catalyst and an organometallic compound catalyst; The chain extender includes at least one of an alcohol chain extender and an amine chain extender; The foaming agent includes at least one of water, carbon dioxide, and hydrohaloolefins; The foam stabilizer includes at least one of silicone compounds such as organopolysiloxane, organopolysiloxane-polyoxyalkylene copolymer, polyalkenylsiloxane with polyoxyalkylene side chains, silicone-grease copolymer, anionic surfactants such as sodium dodecylbenzenesulfonate and sodium lauryl sulfate, polyether siloxane, and phenolic compounds.

5. A polyurethane microporous foam cotton, characterized in that: The polyurethane composition is prepared from the polyurethane composition according to any one of claims 1 to 4.

6. The method for preparing the polyurethane microporous foamed cotton according to claim 5, wherein: The following steps are involved: Mix components A and B at 0~10℃ and 1MPa~10MPa to form a prepolymer; The prepolymer is coated on the surface of a substrate and cured to obtain the polyurethane microporous foam cotton; the curing temperature is 80-130°C.

7. The method for preparing the polyurethane microporous foamed cotton according to claim 6, characterized in that: The preparation method of the phosphorus-nitrogen polyol comprises the following steps: Under a protective atmosphere, 5-hydroxymethylfurfural, an alcohol amine, and a first organic solvent are uniformly mixed and subjected to a first reaction to obtain a first mixed solution; 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide and a second organic solvent are mixed evenly and then added to the first mixed solution, mixed evenly and subjected to a second reaction. After the second reaction is completed, a first post-treatment is performed to obtain the phosphorus-nitrogen-containing polyol.

8. The method for preparing the polyurethane microporous foamed cotton according to claim 7, characterized in that: The molar ratio of the alcoholamine, the 5-hydroxymethylfurfural and the 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide is 1:(0.9-1):(0.8-1); The reaction temperature of the first reaction is 75~95°C, and the reaction time of the first reaction is 4~12h; The reaction temperature of the second reaction is 75-95° C., and the reaction time of the second reaction is 10-24 h; The first organic solvent and the second organic solvent both include alcohol solvents.

9. The method for preparing the polyurethane microporous foamed cotton according to claim 6, wherein: The preparation method of the boron-containing polyol comprises the following steps: Under a protective atmosphere, heating glycerol to 90-120° C., adding boric acid, and carrying out a third reaction at a vacuum degree of 0.1-0.5 MPa to obtain the boron-containing polyol; The temperature of the third reaction is 140-160°C, and the time of the third reaction is 3-6 hours; The molar ratio of glycerol to boric acid is (2-2.3):

1.

10. Application of the polyurethane microporous foamed cotton according to claim 5 or the polyurethane microporous foamed cotton prepared by the preparation method of any one of claims 6 to 9 in the fields of construction, electronic assembly and automobile.

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