Flame-retardant water-based polyurethane coating, preparation method thereof, and microfiber leather

Abstract

The present invention provides a flame retardant waterborne polyurethane coating, a preparation method thereof and microfiber leather, and the technical field of polyurethane coatings. The present invention synthesizes a waterborne polyurethane macromolecule with flame retardant effect by adding a phosphorus-containing chain extender, that is, component A, and adds water-soluble flame retardants monoammonium phosphate, diammonium phosphate, tributyl ammonium pyrophosphate and tetrasodium pyrophosphate, that is, component B. The phosphorus-containing chain extender and component B synergistically enhance the flame retardant effect of the waterborne polyurethane and ensure that the flame retardant waterborne polyurethane coating has good flexibility and mechanical properties.

Description

Technical Field

[0001] The invention relates to the technical field of polyurethane coatings, and in particular to a flame-retardant water-based polyurethane coating and a preparation method thereof, and microfiber leather. Background Art

[0002] Waterborne polyurethane coatings are increasingly used in coating finishing due to their ease of application, low cost and environmental friendliness. One of the main applications of waterborne polyurethane is as a coating for synthetic leather. In recent years, the requirements for flame retardancy and wearability in the field of synthetic leather have gradually increased. The surface coating of synthetic leather requires both good flexibility and mechanical properties, as well as higher flame retardancy requirements. This puts forward new requirements for the surface coating of synthetic leather.

[0003] There are generally two ways to achieve better flame retardant effect of waterborne polyurethane coatings:

[0004] The first method is to polymerize the flame retardant components into the polyurethane macromolecule. This method has the following advantages: 1. Increase the compatibility of the flame retardant group with the polyurethane matrix; 2. Less impact on the mechanical properties of the polyurethane matrix; 3. Since the flame retardant group is a component of the polyurethane material, its overall performance is better. However, the process of polymerizing the flame retardant components into the polyurethane macromolecule is more complicated and the upper limit of the flame retardant effect is not high.

[0005] The second type: post-adding flame retardants. This method has the advantages of simple process, good flame retardant effect, low cost and wide application range. However, since the flame retardants added post-adding in a large number of existing studies are often insoluble in water, they often cause uneven dispersion in the polyurethane coating and deteriorate the mechanical properties of the polyurethane coating. Summary of the invention

[0006] The purpose of the first aspect of the present invention is to provide a flame retardant waterborne polyurethane coating having flame retardant properties, good flexibility and mechanical properties.

[0007] The second aspect of the present invention aims to provide a method for preparing the flame retardant waterborne polyurethane coating.

[0008] The third aspect of the present invention aims to provide a microfiber leather comprising a flame retardant waterborne polyurethane coating prepared by the above-mentioned preparation method.

[0009] According to the purpose of the first aspect of the present invention, the present invention provides a flame retardant waterborne polyurethane coating, comprising component A and component B;

[0010] The component A comprises polytetramethylene ether glycol, 4,4'-methylenebis(phenyl isocyanate), a phosphorus-containing chain extender, 2,2-dihydroxymethylbutyric acid and triethylenediamine;

[0011] The component B is a mixture of monoammonium phosphate, diammonium phosphate, tributylammonium pyrophosphate and tetrasodium pyrophosphate.

[0012] Optionally, the flame retardant waterborne polyurethane coating is prepared from the following components in parts by weight:

[0013] The component A 20-30%;

[0014] The component B 10-20%;

[0015] Solvent 50-70%.

[0016] Optionally, the component A is prepared from the following components in parts by weight:

[0017]

[0018] Optionally, the component B is prepared from the following components in parts by weight:

[0019] The monoammonium phosphate 30-40%;

[0020] The diammonium phosphate 40-55%;

[0021] The tributylammonium pyrophosphate and tetrasodium pyrophosphate are 15-20%.

[0022] According to the purpose of the second aspect of the present invention, the present invention also provides a method for preparing the flame retardant waterborne polyurethane coating, comprising the following steps:

[0023] Dissolving the component B in a solvent in advance;

[0024] The component A is added and mixed, and after high temperature and high speed shearing, it is cooled to obtain the flame retardant waterborne polyurethane coating.

[0025] Optionally, the component A is prepared according to the following steps:

[0026] The polytetrahydrofuran ether diol and the triethylene diamine are mixed, refluxed and condensed in a nitrogen environment, and stirred at a temperature of 75-80° C. for 10-20 minutes;

[0027] Add the 4,4'-methylenebis(phenyl isocyanate) and react for 1.5-2h;

[0028] Add the phosphorus-containing chain extender and react for 1-2 hours;

[0029] After cooling to 65-70° C., adding the 2,2-dihydroxymethylbutyric acid and reacting for 1-2 hours;

[0030] After cooling to 40-45° C., the triethylenediamine is added to react for 30-45 minutes to obtain the component A.

[0031] 7. The preparation method according to claim 6, characterized in that the phosphorus-containing chain extender is prepared according to the following steps:

[0032] Dissolve p-hydroxybenzaldehyde and 3-aminopropanol in anhydrous ethanol and pour into the first container;

[0033] Place the first container in an oil bath and react at 60-65° C. for 2-3 hours;

[0034] After cooling to room temperature, adsorption, filtration and washing are performed, and then drying is performed under vacuum at 50-55°C for 12-24h to obtain a crystalline solid;

[0035] The crystalline solid and 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide are mixed and poured into a second container, anhydrous ethanol is added, and the mixture is stirred and reacted at 60-65° C. for 6-8 hours;

[0036] After cooling to room temperature, the mixture is filtered and washed with anhydrous ethanol, and then dried in a vacuum drying oven to a constant weight to obtain the phosphorus-containing chain extender.

[0037] Optionally, the weight proportion of the p-hydroxybenzaldehyde is 28-30%, the weight proportion of the 3-aminopropanol is 17-19%, and the weight proportion of the 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide is 51-55%.

[0038] Optionally, in the step of adding component A for mixing, cooling after high temperature and high speed shearing to obtain the flame retardant waterborne polyurethane coating, the shear rate is greater than 10000 r / min, the shear temperature is 80-90°C, and the shear time is 0.5-2h.

[0039] According to the purpose of the second aspect of the present invention, the present invention also provides a microfiber leather, comprising a flame retardant water-based polyurethane coating prepared by the above-mentioned preparation method.

[0040] The present invention synthesizes a waterborne polyurethane macromolecule with flame retardant effect by adding a phosphorus-containing chain extender, that is, component A, and adds water-soluble flame retardants such as monoammonium phosphate, diammonium phosphate, tributyl ammonium pyrophosphate and tetrasodium pyrophosphate, that is, component B. The phosphorus-containing chain extender and component B synergistically enhance the flame retardant effect of the waterborne polyurethane and ensure that the flame retardant waterborne polyurethane coating has good flexibility and mechanical properties.

[0041] Furthermore, since monoammonium phosphate, diammonium phosphate, tributyl ammonium pyrophosphate and tetrasodium pyrophosphate can be completely dissolved, the uniformity of dispersion of the flame retardant material during the coating process of the flame retardant waterborne polyurethane coating can be ensured. After the solvent evaporates, the flame retardant material can be evenly distributed throughout the coating, thereby greatly improving the flame retardant properties of the coating.

[0042] Based on the following detailed description of specific embodiments of the present invention in conjunction with the accompanying drawings, those skilled in the art will become more aware of the above and other objects, advantages and features of the present invention. BRIEF DESCRIPTION OF THE DRAWINGS

[0043] Hereinafter, some specific embodiments of the present invention will be described in detail in an exemplary and non-limiting manner with reference to the accompanying drawings. The same reference numerals in the accompanying drawings indicate the same or similar components or parts. It should be understood by those skilled in the art that these drawings are not necessarily drawn to scale. In the accompanying drawings:

[0044] Figure 1 is a schematic flow chart of a method for preparing component A according to one embodiment of the present invention;

[0045] Figure 2 is a schematic flow chart of a method for preparing a phosphorus-containing chain extender according to an embodiment of the present invention. DETAILED DESCRIPTION

[0046] Embodiments of the present invention are described in detail below, examples of which are shown in the accompanying drawings, wherein the same or similar reference numerals throughout represent the same or similar elements or elements having the same or similar functions. The embodiments described below with reference to the accompanying drawings are exemplary and are intended to be used to explain the present invention, and should not be construed as limiting the present invention.

[0047] This embodiment provides a flame retardant waterborne polyurethane coating, which includes component A and component B, wherein component A includes polytetramethylene ether glycol, 4,4'-methylenebis(phenyl isocyanate), a phosphorus-containing chain extender, 2,2-dihydroxymethylbutyric acid and triethylenediamine. Component B is a mixture of monoammonium phosphate, diammonium phosphate, tributylammonium pyrophosphate and tetrasodium pyrophosphate. Here, the phosphorus-containing chain extender is a phosphorus-containing diol. Component A can be understood as a phosphorus-containing waterborne polyurethane macromolecule, and component B can be understood as a water-soluble phosphate.

[0048] In this embodiment, a waterborne polyurethane macromolecule with flame retardant effect is synthesized by adding a phosphorus-containing chain extender, that is, component A, and water-soluble flame retardants monoammonium phosphate, diammonium phosphate, tributyl ammonium pyrophosphate and tetrasodium pyrophosphate are added, that is, component B. The phosphorus-containing chain extender and component B synergistically enhance the flame retardant effect of the waterborne polyurethane and ensure that the flame retardant waterborne polyurethane coating has good flexibility and mechanical properties.

[0049] Furthermore, since monoammonium phosphate, diammonium phosphate, tributyl ammonium pyrophosphate and tetrasodium pyrophosphate can be completely dissolved, the uniformity of dispersion of the flame retardant material during the coating process of the flame retardant waterborne polyurethane coating can be ensured. After the solvent evaporates, the flame retardant material can be evenly distributed throughout the coating, thereby greatly improving the flame retardant properties of the coating.

[0050] In this embodiment, the flame retardant waterborne polyurethane coating is prepared from the following components by weight: component A 20-30%, component B 10-20%, and solvent 50-70%. Here, the solvent is water. The viscosity of the flame retardant waterborne polyurethane coating is 300-1000 mPa·s.

[0051] In this embodiment, component A is prepared from the following components in parts by weight: 41-45% polytetramethylene ether glycol, 35-37% 4,4'-methylenebis(phenyl isocyanate), 11-13% phosphorus-containing chain extender, 6-10% 2,2-dihydroxymethylbutyric acid, and 1-2% triethylenediamine.

[0052] In this embodiment, component B is prepared from the following components in parts by weight: 30-40% monoammonium phosphate, 40-55% diammonium phosphate, 15-20% tributylammonium pyrophosphate and tetrasodium pyrophosphate.

[0053] This embodiment also provides a method for preparing the flame retardant waterborne polyurethane coating, comprising the following steps:

[0054] Step 1: Dissolve component B in a solvent in advance;

[0055] Step 2: Add component A and mix, and cool after high temperature and high speed shearing to obtain a flame retardant waterborne polyurethane coating.

[0056] In step 2, the shear rate is greater than 10000 r / min, the shear temperature is 80-90° C., and the shear time is 0.5-2 h.

[0057] Figure 1 is a schematic flow chart of a method for preparing component A according to one embodiment of the present invention. Figure 1 As shown, component A is prepared according to the following steps:

[0058] Step S100, mixing polytetrahydrofuran ether glycol and triethylene diamine, reflux condensing in a nitrogen environment, and stirring at a temperature of 75-80° C. for 10-20 minutes;

[0059] Step S200, adding 4,4'-methylenebis(phenyl isocyanate) and reacting for 1.5-2h;

[0060] Step S300, adding a phosphorus-containing chain extender and reacting for 1-2 hours;

[0061] Step S400, after cooling to 65-70°C, adding 2,2-dihydroxymethylbutyric acid and reacting for 1-2h;

[0062] Step S500, after cooling to 40-45°C, triethylenediamine is added to react for 30-40 minutes to obtain component A.

[0063] In step S400, during the reaction of adding 2,2-dihydroxymethylbutyric acid, a proper amount of N,N-dimethylformamide (DMF) is added to adjust the viscosity of the flame retardant waterborne polyurethane coating.

[0064] Figure 2 FIG. 1 is a schematic flow chart of a method for preparing a phosphorus-containing chain extender according to an embodiment of the present invention. Figure 2 As shown, the phosphorus-containing chain extender is prepared according to the following steps:

[0065] Step S310, dissolving p-hydroxybenzaldehyde and 3-aminopropanol in anhydrous ethanol and pouring the mixture into a first container, wherein the first container is a three-necked flask;

[0066] Step S320, placing the first container in an oil bath and reacting at 60-65° C. for 2-3 hours;

[0067] Step S330, after cooling to room temperature, adsorption, filtration and washing are performed, and then drying is performed under vacuum at 50-55° C. for 12-24 hours to obtain a crystalline solid;

[0068] Step S340, mixing the crystalline solid and 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide into a second container, adding anhydrous ethanol, and stirring the mixture at 60-65° C. for 6-8 hours. Here, the second container is a four-necked flask;

[0069] Step S350, after cooling to room temperature, filtering and washing with anhydrous ethanol, and then drying in a vacuum drying oven to constant weight, to obtain a phosphorus-containing chain extender. Here, the phosphorus-containing chain extender is a light yellow crystalline solid, that is, a phosphorus-containing diol.

[0070] In this embodiment, the weight proportion of p-hydroxybenzaldehyde is 28-30%, the weight proportion of 3-aminopropanol is 17-19%, and the weight proportion of 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide is 51-55%.

[0071] This embodiment also provides a microfiber leather, including a flame-retardant water-based polyurethane coating prepared by the above-mentioned preparation method.

[0072] This embodiment uses homemade phosphorus-containing diol as a chain extender to prepare a flame-retardant water-based polyurethane, and adds water-soluble phosphates to water to synergistically enhance the flame retardant effect of the coating and ensure that the coating has good flexibility and mechanical properties. In addition, this embodiment has a simple process, low toxicity, low cost, and a friendly processing environment. The synthesized phosphorus-containing chain extender itself is non-toxic and harmless, no toxic or harmful substances are used in the preparation process, the yield is high, and it can be directly used in the synthesis of water-based flame-retardant polyurethane.

[0073] The following is described in detail through specific embodiments:

[0074] Embodiment 1:

[0075] The preparation method of the flame retardant waterborne polyurethane coating is as follows:

[0076] 10% of component B was pre-dissolved in 60 parts of water, and then 30% of component A was mixed and poured in, and stirred and sheared at 80° C. and 11000 rpm for 2 hours, and a flame-retardant waterborne polyurethane coating was obtained after cooling.

[0077] The preparation method of component A is as follows:

[0078] 41% polytetrahydrofuran ether glycol (PTMEG) and 1% catalyst triethylene diamine were added to a four-necked flask, stirred at 80°C for 10 minutes under nitrogen environment and reflux condensation. Then 35% 4,4'-methylenebis(phenyl isocyanate) was added to react for 1.5 hours, and then 13% phosphorus-containing chain extender was added to react for 1 hour. After cooling to 70°C, 10% 2,2-dihydroxymethylbutyric acid (DMBA) was added to react for 1 hour, and an appropriate amount of N,N-dimethylformamide (DMF) was added to adjust the viscosity. After the reaction was complete, the reaction system was cooled to 45°C, and excess triethylamine was added for neutralization reaction for 30 minutes to obtain component A.

[0079] The preparation method of component B is as follows:

[0080] 30% of monoammonium phosphate, 55% of diammonium phosphate, 15% of tributylammonium pyrophosphate and tetrasodium pyrophosphate were mixed uniformly to obtain component B.

[0081] The preparation method of the phosphorus-containing chain extender is as follows:

[0082] 28% p-hydroxybenzaldehyde and 17% 3-aminopropanol were dissolved in anhydrous ethanol, poured into a three-necked flask, and a stirring paddle and a reflux condenser were installed. The mixture was heated and stirred in an oil bath, and the temperature of the oil bath was set to 60°C for 2 hours. After the reaction was completed, the mixture was cooled to room temperature, and the precipitate was adsorbed and filtered, thoroughly cleaned, and dried in a vacuum oven at 50°C for 12 hours to obtain a dark yellow crystalline solid. The obtained dark yellow crystalline solid and 55% 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide (DOPO) were mixed and poured into a four-necked flask, and sufficient anhydrous ethanol was added, and then the mixture was rapidly stirred at 60°C for 8 hours. After the reaction was completed, the mixture was stirred and cooled to room temperature, filtered, washed with anhydrous ethanol three times, and dried in a vacuum oven to constant weight to obtain a light yellow crystalline solid, which was a phosphorus-containing diol chain extender.

[0083] Embodiment 2:

[0084] The preparation method of the flame retardant waterborne polyurethane coating is as follows:

[0085] 20% of component B was pre-dissolved in 60% of water, and then 20% of component A was mixed and poured in, and stirred and sheared at 90° C. and 12000 rpm for 2 hours, and a flame-retardant waterborne polyurethane coating was obtained after cooling.

[0086] The preparation method of component A is as follows:

[0087] 42% polytetrahydrofuran ether glycol (PTMEG) and 2% catalyst triethylene diamine were added to a four-necked flask, stirred at 75°C for 20 minutes under nitrogen environment and reflux condensation. Then 36% 4,4'-methylenebis(phenyl isocyanate) was added to react for 2 hours, and then 12% phosphorus-containing chain extender was added to react for 2 hours. After cooling to 65°C, 8% 2,2-dihydroxymethylbutyric acid (DMBA) was added to react for 2 hours, and an appropriate amount of N,N-dimethylformamide (DMF) was added to adjust the viscosity. After the reaction was complete, the reaction system was cooled to 40°C, and excess triethylamine was added for neutralization reaction for 45 minutes to obtain component A.

[0088] The preparation method of component B is as follows:

[0089] 40% of monoammonium phosphate, 40% of diammonium phosphate, 20% of tributylammonium pyrophosphate and tetrasodium pyrophosphate were mixed uniformly to obtain component B.

[0090] The preparation method of the phosphorus-containing chain extender is as follows:

[0091] 29% p-hydroxybenzaldehyde and 18% 3-aminopropanol were dissolved in anhydrous ethanol, poured into a three-necked flask, and a stirring paddle and a reflux condenser were installed. The mixture was heated and stirred in an oil bath, and the temperature of the oil bath was set to 60°C for 3 hours. After the reaction was completed, the mixture was cooled to room temperature, and the precipitate was adsorbed and filtered, thoroughly cleaned, and dried in a vacuum oven at 55°C for 24 hours to obtain a dark yellow crystalline solid. The obtained dark yellow crystalline solid and 53% 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide (DOPO) were mixed and poured into a four-necked flask, and sufficient anhydrous ethanol was added, and then the mixture was rapidly stirred at 65°C for 6 hours. After the reaction was completed, the mixture was stirred and cooled to room temperature, filtered, washed with anhydrous ethanol three times, and dried in a vacuum oven to constant weight to obtain a light yellow crystalline solid, which was a phosphorus-containing diol chain extender.

[0092] Embodiment 3:

[0093] The preparation method of the flame retardant waterborne polyurethane coating is as follows:

[0094] 20% of component B was pre-dissolved in 50% of water, and then 30% of component A was mixed and poured in, and stirred and sheared at 90° C. and 13000 rpm for 0.5 h, and a flame-retardant waterborne polyurethane coating was obtained after cooling.

[0095] The preparation method of component A is as follows:

[0096] 45% polytetrahydrofuran ether glycol (PTMEG) and 1% catalyst triethylene diamine were added to a four-necked flask, stirred at 80°C for 10 minutes under nitrogen atmosphere and reflux condensation. Then 37% 4,4'-methylenebis(phenyl isocyanate) was added to react for 1.5 hours, and then 11% phosphorus-containing chain extender was added to react for 1 hour. After cooling to 70°C, 6% 2,2-dihydroxymethylbutyric acid (DMBA) was added to react for 1 hour, and an appropriate amount of N,N-dimethylformamide (DMF) was added to adjust the viscosity. After the reaction was complete, the reaction system was cooled to 45°C, and excess triethylamine was added for neutralization reaction for 30 minutes to obtain component A.

[0097] The preparation method of component B is as follows:

[0098] 35% of monoammonium phosphate, 50% of diammonium phosphate, 15% of tributylammonium pyrophosphate and tetrasodium pyrophosphate were mixed uniformly to obtain component B.

[0099] The preparation method of the phosphorus-containing chain extender is as follows:

[0100] 30% p-hydroxybenzaldehyde and 19% 3-aminopropanol were dissolved in anhydrous ethanol, poured into a three-necked flask, and a stirring paddle and a reflux condenser were installed. The mixture was heated and stirred in an oil bath, and the temperature of the oil bath was set to 60°C for 2 hours. After the reaction was completed, the mixture was cooled to room temperature, and the precipitate was adsorbed and filtered, thoroughly cleaned, and dried in a vacuum oven at 50°C for 12 hours to obtain a dark yellow crystalline solid. The obtained dark yellow crystalline solid and 51% 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide (DOPO) were mixed and poured into a four-necked flask, and sufficient anhydrous ethanol was added, and then the mixture was rapidly stirred and reacted at 65°C for 6 hours. After the reaction was completed, the mixture was stirred and cooled to room temperature, filtered, washed with anhydrous ethanol three times, and dried in a vacuum oven to constant weight to obtain a light yellow crystalline solid, which was a phosphorus-containing diol chain extender.

[0101] Comparative Example 1:

[0102] The preparation method of the flame retardant waterborne polyurethane coating is as follows:

[0103] 30% of component A was poured into 50% of water, stirred and sheared at 90°C and 13000 rpm for 0.5 h, and then cooled to obtain a polyurethane coating. In Comparative Example 1, component B in Examples 1-3 was not added.

[0104] The preparation method of the phosphorus-containing chain extender is as follows:

[0105] 30% p-hydroxybenzaldehyde and 19% 3-aminopropanol were dissolved in anhydrous ethanol, poured into a three-necked flask, and a stirring paddle and a reflux condenser were installed. The mixture was heated and stirred in an oil bath, and the temperature of the oil bath was set to 60°C for 2 hours. After the reaction was completed, the mixture was cooled to room temperature, and the precipitate was adsorbed and filtered, thoroughly cleaned, and dried in a vacuum oven at 50°C for 12 hours to obtain a dark yellow crystalline solid. The obtained dark yellow crystalline solid and 51% 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide (DOPO) were mixed and poured into a four-necked flask, and sufficient anhydrous ethanol was added, and then the mixture was rapidly stirred at 80°C for 6 hours. After the reaction was completed, the mixture was stirred and cooled to room temperature, filtered, washed with anhydrous ethanol three times, and dried in a vacuum oven to constant weight to obtain a light yellow crystalline solid, which was a phosphorus-containing diol chain extender.

[0106] The preparation method of component A is as follows:

[0107] 45% polytetrahydrofuran ether glycol (PTMEG) and 1% catalyst triethylene diamine were added to a four-necked flask, stirred at 80°C for 10 minutes under nitrogen atmosphere and reflux condensation. Then 37% 4,4'-methylenebis(phenyl isocyanate) was added to react for 1.5 hours, and then 11% phosphorus-containing chain extender was added to react for 1 hour. After cooling to 70°C, 6% 2,2-dihydroxymethylbutyric acid (DMBA) was added to react for 1 hour, and an appropriate amount of N,N-dimethylformamide (DMF) was added to adjust the viscosity. After the reaction was complete, the reaction system was cooled to 45°C, and excess triethylamine was added for neutralization reaction for 30 minutes to obtain component A.

[0108] Comparative Example 2:

[0109] The preparation method of the flame retardant waterborne polyurethane coating is as follows:

[0110] 20% of component B was pre-dissolved in 50% of water, and then 30% of component A was mixed and poured in, and stirred and sheared at 90° C. and 13000 rpm for 0.5 h, and a flame-retardant waterborne polyurethane coating was obtained after cooling.

[0111] The preparation method of component A is as follows:

[0112] 45% polytetrahydrofuran ether glycol (PTMEG) and 1% catalyst triethylenediamine were added to a four-necked flask, stirred at 80°C for 10 minutes under nitrogen environment and reflux condensation. Then 37% 4,4'-methylenebis(phenyl isocyanate) was added to react for 1.5 hours, and then 11% chain extender 1,4-butanediol was added to react for 1 hour. After cooling to 70°C, 6% 2,2-dihydroxymethylbutyric acid (DMBA) was added to react for 1 hour, and an appropriate amount of N,N-dimethylformamide (DMF) was added to adjust the viscosity. After the reaction was complete, the reaction system was cooled to 45°C, and excess triethylamine was added for neutralization reaction for 30 minutes to obtain component A. Comparative Example 2 uses a commonly used chain extender, and does not use the phosphorus-containing chain extender in Examples 1-3.

[0113] The preparation method of component B is as follows:

[0114] 35% of magnesium hydroxide, 50% of aluminum hydroxide, 15% of tributylammonium pyrophosphate and tetrasodium pyrophosphate were uniformly mixed to obtain component B.

[0115] Comparative Example 3

[0116] The preparation method of the flame retardant waterborne polyurethane coating is as follows:

[0117] 10% powder flame retardant was pre-dispersed in 60% water, and then 30% component A was mixed and poured in, and stirred and sheared at 80°C and 11000 rpm for 2 hours, and then cooled to obtain a flame retardant waterborne polyurethane coating. In Comparative Example 3, a commonly used powder flame retardant was used, and component B in Examples 1-3 was not used.

[0118] The preparation method of component A is as follows:

[0119] 41% polytetrahydrofuran ether glycol (PTMEG) and 1% catalyst triethylene diamine were added to a four-necked flask, stirred at 80°C for 10 minutes under nitrogen environment and reflux condensation. Then 35% 4,4'-methylenebis(phenyl isocyanate) was added to react for 1.5 hours, and then 13% phosphorus-containing chain extender was added to react for 1 hour. After cooling to 70°C, 10% 2,2-dihydroxymethylbutyric acid (DMBA) was added to react for 1 hour, and an appropriate amount of N,N-dimethylformamide (DMF) was added to adjust the viscosity. After the reaction was complete, the reaction system was cooled to 45°C, and excess triethylamine was added for neutralization reaction for 30 minutes to obtain component A.

[0120] The preparation method of powder flame retardant is as follows:

[0121] Mix 50% magnesium hydroxide and 50% aluminum hydroxide evenly.

[0122] The preparation method of the phosphorus-containing chain extender is as follows:

[0123] 28% p-hydroxybenzaldehyde and 17% 3-aminopropanol were dissolved in anhydrous ethanol, poured into a three-necked flask, and a stirring paddle and a reflux condenser were installed. The mixture was heated and stirred in an oil bath, and the temperature of the oil bath was set to 60°C for 2 hours. After the reaction was completed, the mixture was cooled to room temperature, and the precipitate was adsorbed and filtered, thoroughly cleaned, and dried in a 50°C vacuum oven for 12 hours to obtain a dark yellow crystalline solid. The obtained dark yellow crystalline solid and 55% 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide (DOPO) were mixed and poured into a four-necked flask, and sufficient anhydrous ethanol was added, and then the mixture was rapidly stirred at 80°C for 6 hours. After the reaction was completed, the mixture was stirred and cooled to room temperature, filtered, washed with anhydrous ethanol three times, and dried in a vacuum oven to constant weight to obtain a light yellow crystalline solid, which was a phosphorus-containing diol chain extender.

[0124] Test Characterization:

[0125] The test results of Examples 1-3 and Comparative Examples 1-3 are as follows:

[0126]

[0127] As can be seen from the above table, if component B is not added or component B is replaced by a commonly used powder flame retardant, the flame retardant effect will be reduced, and the flexibility and mechanical properties of the polyurethane coating will be reduced. Replacing the phosphorus-containing chain extender with a commonly used chain extender will also reduce the flame retardant effect and the flexibility and mechanical properties of the polyurethane coating. In other words, replacing either component B or the phosphorus-containing chain extender in the present invention will result in a reduction in the flame retardant effect, flexibility and mechanical properties of the polyurethane coating.

[0128] Test method:

[0129] The prepared polyurethane coating is applied to the surface of synthetic leather and formed into coated fabric after drying.

[0130] Vertical combustion performance test of coated fabrics

[0131] Referring to GB / T5455-2014 “Determination of damage length, smoldering and afterflaming time of flame retardant textiles by vertical method”, cut a 300mm×90mm sample fabric and fix it in the vertical combustion tester with a sample clamp. Ignite and burn. After the afterflaming and smoldering are over, record the damage length. Repeat 3 times and take the average value as the final result.

[0132] Coated fabric limiting oxygen index test

[0133] According to GB / T 5454-1997 "Textile Combustion Performance Test Oxygen Index Method", the measurement is carried out using a fully automatic oxygen index tester (Nanjing Yulei Instrument Equipment Co., Ltd. JL-JF-5 model). Specifically, a 150mm×60mm sample is cut and fixed in the combustion column with a sample clamp. After setting the oxygen concentration, the ignition test is started. The oxygen concentration (c(O2)) of the sample is recorded when the afterburning and smoldering time reaches 2min or more, or when the damaged length reaches 40mm and the sample is extinguished. Repeat 3 times, and then calculate the limiting oxygen index (LOI) according to the formula in the standard. Repeat 3 times and take the average value as the final result.

[0134] Coating film breaking strength and elongation test

[0135] The flame-retardant waterborne polyurethane coating was poured into a 10cm*10cm PTFE mold and dried at 40°C for 72 hours to form a film. Afterwards, the film was cut into dumbbell-shaped specimens with a gauge length of 16mm. The samples were tensile tested using a universal testing machine at room temperature, and their breaking strength and breaking elongation were recorded.

[0136] At this point, those skilled in the art should recognize that, although multiple exemplary embodiments of the present invention have been shown and described in detail herein, many other variations or modifications that conform to the principles of the present invention can still be directly determined or derived based on the content disclosed in the present invention without departing from the spirit and scope of the present invention. Therefore, the scope of the present invention should be understood and recognized as covering all these other variations or modifications.

Claims

1. A flame retardant waterborne polyurethane coating for microfiber leather, characterized in that: Comprising component A and component B; The component A comprises polytetramethylene ether glycol, 4,4'-methylenebis(phenyl isocyanate), a phosphorus-containing chain extender, 2,2-dihydroxymethylbutyric acid and triethylenediamine; The component B is a mixture of monoammonium phosphate, diammonium phosphate, tributylammonium pyrophosphate and tetrasodium pyrophosphate; The flame retardant waterborne polyurethane coating is prepared from the following percentages of components by weight: The component A 20-30%; The component B 10-20%; Solvent 50-70%; The component B is prepared from the following percentages of components by weight: The monoammonium phosphate 30-40%; The diammonium phosphate 40-55%; The tributylammonium pyrophosphate and tetrasodium pyrophosphate 15-20%; The phosphorus-containing chain extender is prepared according to the following steps: Dissolve p-hydroxybenzaldehyde and 3-aminopropanol in anhydrous ethanol and pour into the first container; Place the first container in an oil bath and react at 60-65° C. for 2-3 hours; After cooling to room temperature, adsorption, filtration and washing are performed, and then drying is performed under vacuum at 50-55°C for 12-24h to obtain a crystalline solid; The crystalline solid and 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide are mixed and poured into a second container, anhydrous ethanol is added, and the mixture is stirred and reacted at 60-65° C. for 6-8 hours; After cooling to room temperature, the mixture is filtered and washed with anhydrous ethanol, and then dried in a vacuum drying oven to a constant weight to obtain the phosphorus-containing chain extender.

2. The flame retardant waterborne polyurethane coating according to claim 1, characterized in that: The component A is prepared from the following percentages of components by weight: The polytetramethylene glycol ether 41-45%; 4,4'-methylenebis(phenyl isocyanate) 35-37%; The phosphorus-containing chain extender is 11-13%; 6-10% of the 2,2-dihydroxymethylbutyric acid; The triethylenediamine is 1-2%.

3. A method for preparing a flame retardant waterborne polyurethane coating as claimed in any one of claims 1 to 2, characterized in that: The steps include: Dissolving the component B in a solvent in advance; Adding the component A and mixing, cooling after high temperature and high speed shearing, to obtain the flame retardant waterborne polyurethane coating; In the step of adding the component A for mixing, cooling after high temperature and high speed shearing to obtain the flame retardant waterborne polyurethane coating, the shear rate is greater than 10000 r / min and the shear temperature is 80-90°C.

4. The preparation method according to claim 3, characterized in that: The component A is prepared according to the following steps: The polytetrahydrofuran ether diol and the triethylene diamine are mixed, refluxed and condensed in a nitrogen environment, and stirred at a temperature of 75-80° C. for 10-20 minutes; Add the 4,4'-methylenebis(phenyl isocyanate) and react for 1.5-2h; Add the phosphorus-containing chain extender and react for 1-2 hours; After cooling to 65-70° C., adding the 2,2-dihydroxymethylbutyric acid and reacting for 1-2 hours; After cooling to 40-45° C., the triethylenediamine is added to react for 30-45 minutes to obtain the component A.

5. The preparation method according to claim 4, characterized in that: The weight percentage of the p-hydroxybenzaldehyde is 28-30%, the weight percentage of the 3-aminopropanol is 17-19%, and the weight percentage of the 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide is 51-55%.

6. The preparation method according to claim 4, characterized in that: In the step of adding the component A, mixing, cooling after high temperature and high speed shearing to obtain the flame retardant waterborne polyurethane coating, the shearing time is 0.5-2h.

7. A microfiber leather, characterized in that: The invention comprises a flame retardant waterborne polyurethane coating prepared by the preparation method according to any one of claims 3 to 6.

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