A method for preparing a bio-based flame-retardant self-matting waterborne polyurethane and a bio-based flame-retardant matte coating

Abstract

This invention discloses a method for preparing a bio-based flame-retardant self-matting waterborne polyurethane, comprising the following steps: reacting bio-based acid anhydrides and bio-based triols to prepare a carboxyl-containing bio-based hydrophilic chain extender; adding bio-based polyether glycol, vegetable oil polyol, catalyst, bio-based hydrophilic chain extender, bio-based chain extender, and bio-based flame retardant to a reaction vessel and mixing evenly, then adding diisocyanate, and reacting at 60-80℃ for 3-6 hours to obtain an isocyanate-terminated prepolymer; neutralization and emulsification: adding a neutralizing agent to the above prepolymer, emulsifying with water, and then adding a sulfonate-type chain extender and an amine chain extender to carry out a chain extension reaction to obtain a waterborne polyurethane emulsion. This invention also discloses a bio-based flame-retardant matte coating. The bio-based flame-retardant self-matting waterborne polyurethane of this invention has a high bio-based content, low gloss, excellent matte effect, and excellent flame-retardant properties.

Description

Technical Field

[0001] This invention relates to the preparation and application of waterborne polyurethane, and particularly to a method for preparing a bio-based flame-retardant self-matting waterborne polyurethane and a bio-based flame-retardant matte coating. Background Technology

[0002] Waterborne polyurethane possesses excellent physical and mechanical properties and environmental performance, making it a key focus of research and development in the coatings industry. Among them, waterborne self-matte (self-dulling) polyurethane exhibits superior decorative effects and has become a research hotspot. On the other hand, to reduce dependence on petroleum, mitigate the greenhouse effect, and promote the achievement of dual-carbon goals, bio-based materials are rapidly developing. Vegetable oils, due to their ease of availability, processing, chemical properties, and relatively low cost, have become one of the most widely used renewable materials. Furthermore, an increasing number of raw material productions are adopting bio-based routes. On the one hand, bio-based products are more sustainable than fossil-based products; on the other hand, they also mean lower carbon emissions. These bio-based raw materials include, but are not limited to, bio-based oligomeric polyols. Currently, there are many commercially available bio-based polyols, such as bio-based polytetramethylene ether glycol and bio-based polytrimethylene ether glycol; bio-based chain extenders, such as 1,4-butanediol and 1,3-propanediol; bio-based diisocyanates, such as pentamethylene diisocyanate, dimer acid diisocyanate, lysine diisocyanate, and vegetable oil-modified isocyanates. The synthesis of waterborne polyurethane requires the introduction of hydrophilic chain extenders to form self-emulsifying waterborne polyurethane. Existing hydrophilic chain extenders, including dimethylolpropionic acid (DMPA) and dimethylolbutyric acid (DMPO), are not bio-based products, directly resulting in low bio-based content in waterborne polyurethane, making it difficult to meet international environmental regulations for bio-based products. Chinese patent CN 112280459A discloses a flame-retardant vegetable oil-based waterborne polyurethane coating and its preparation method, but only uses castor oil as the source of bio-based carbon content, resulting in a low bio-based content in the product. Chinese patent CN 116284661A prepares bio-based vegetable oil polyols via a thiol-olefin click method, then reacts them with lysine diisocyanate to prepare waterborne polyurethane. However, the hydrophilic chain extender used, dimethylolpropionic acid, is still a petroleum-based chain extender, and the bio-based content of the prepared bio-based polyurethane emulsion needs further improvement. Summary of the Invention

[0003] In order to overcome the above-mentioned shortcomings and deficiencies of the prior art, the purpose of this invention is to provide a method for preparing bio-based flame-retardant self-matting waterborne polyurethane, which has a high bio-based content and is environmentally friendly.

[0004] Another objective of this invention is to provide a bio-based flame-retardant matte coating with high bio-based content and environmental friendliness, and the prepared coating has the advantages of flame retardant function and low gloss.

[0005] The purpose of the present invention is achieved through the following technical solutions:

[0006] A method for preparing a bio-based flame-retardant, self-matting waterborne polyurethane includes the following steps:

[0007] (1) Preparation of bio-based hydrophilic chain extender: Bio-based acid anhydride and bio-based triol are mixed at a molar ratio of 1:0.9-1.1, organic solvent is added, and the mixture is reacted at 80-90℃ for 2-3 hours. The organic solvent is removed by rotary evaporation to obtain the bio-based hydrophilic chain extender.

[0008] The bio-based acid anhydride is at least one of succinic anhydride, maleic anhydride, and itaconic anhydride; the bio-based triol is at least one of natural glycerol, bio-based trimethylolpropane, trifunctional castor oil polyol, and trifunctional cashew nut polyol.

[0009] (2) Preparation of prepolymer: Bio-based polyether glycol, vegetable oil polyol, bio-based hydrophilic chain extender, bio-based chain extender and bio-based flame retardant are mixed at 40℃~60℃ for 30min~60min, then diisocyanate and catalyst are added and reacted at 60℃~85℃ for 3~6h to obtain isocyanate-terminated prepolymer. During the reaction, organic solvent is added to reduce viscosity.

[0010] The bio-based polyether glycol is at least one of bio-based polytetrahydrofuran glycol and bio-based polytrimethylene ether glycol; the vegetable oil polyol is at least one of castor oil and castor oil polyol; the bio-based chain extender is at least one of bio-based 1,3-propanediol and bio-based 1,4-butanediol; the catalyst is at least one of diethylbismuth and bismuth neodecanoate; the catalyst is at least one of diethylbismuth and bismuth neodecanoate; the bio-based flame retardant is at least one of casein and phytic acid derivatives.

[0011] (3) Emulsion preparation: Cool down to 40℃~50℃, add neutralizing agent to the prepolymer in step (2) and carry out neutralization reaction; add water for high-speed emulsification, then add sulfonate type chain extender aqueous solution and amine chain extender aqueous solution in sequence, emulsify and extend chain for 30~60min, filter and discharge to obtain bio-based flame retardant self-matting waterborne polyurethane emulsion.

[0012] Preferably, the sulfonate chain extender is at least one of sodium 2-[(2-aminoethyl)amino]ethanesulfonate and sodium 3-[(2-aminoethyl)amino]propanesulfonate.

[0013] Preferably, the amine chain extender is at least one selected from ethylenediamine, diethylenetriamine, triethylenetetramine, and tetraethylenepentamine.

[0014] Preferably, the neutralizing agent is a tertiary amine neutralizing agent, and its amount is 70% to 120% of the amount of the bio-based hydrophilic chain extender.

[0015] Preferably, the phytic acid derivative is a product of the reaction between phytic acid and an organic amine; the organic amine is one of triethylamine and tetramethylethylenediamine.

[0016] Preferably, the organic solvent is at least one of acetone and butanone.

[0017] Preferably, the amount of isocyanate in the diisocyanate is 1 to 2.5 times the total amount of the vegetable oil polyol, bio-based polyether glycol, bio-based hydrophilic chain extender, and the hydroxyl groups of the bio-based chain extender.

[0018] Preferably, the amount of the bio-based hydrophilic chain extender is 1.8% to 3.5% of the total mass of the vegetable oil polyol, bio-based polyether diol, bio-based hydrophilic chain extender, bio-based chain extender, sulfonate chain extender, amine chain extender, and diisocyanate.

[0019] Preferably, the amounts of each raw material used in the reaction, by mass, are as follows:

[0020] The emulsion contains 1-15 parts of bio-based polyether glycol, 0.5-8 parts of vegetable oil polyol, 0.5-5 parts of bio-based hydrophilic chain extender, 0.1-1.5 parts of bio-based chain extender, 0.05 parts of organic bismuth catalyst, 8-18 parts of diisocyanate, 1-5 parts of bio-based flame retardant, 0.2-0.5 parts of neutralizer, 0.4-1 parts of sulfonate chain extender, and 0.5-1.2 parts of amine chain extender; the amount of water added is such that the solid content of the emulsion is 20%-35%.

[0021] Preferably, the number average molecular weight of the bio-based polyether diol in step (2) is 1000 g / mol to 2000 g / mol.

[0022] Preferably, the neutralizing agent in step (3) is triethylamine.

[0023] Preferably, the neutralization reaction in step (3) is carried out at 25°C to 50°C for 5 to 10 minutes.

[0024] Preferably, the mixing method in step (2) is stirring, which is carried out at 40℃~60℃ for 15min~30min.

[0025] Preferably, the reaction in step (2) is carried out at 60℃~85℃ for 3h~5h.

[0026] Bio-based flame-retardant matte coating, including the bio-based flame-retardant self-matting waterborne polyurethane prepared by the aforementioned preparation method.

[0027] Preferably, by weight, the bio-based flame-retardant matte coating comprises 85-88 parts of bio-based flame-retardant self-matting waterborne polyurethane emulsion, 0.05-0.15 parts of defoamer, 0.15-0.2 parts of leveling agent, 2-2.5 parts of anti-settling agent, 0.2-1.5 parts of thickener, 3-5 parts of film-forming aid, and 6-7 parts of water.

[0028] The principle of this invention is as follows:

[0029] This invention utilizes the reaction of bio-based triols and bio-based acid anhydrides to generate bio-based dihydroxycarboxylic acids, which serve as hydrophilic chain extenders in polyurethane synthesis. These extenders react with bio-based diols and diisocyanates to prepare bio-based polyurethane prepolymers. Through emulsification and post-chain extension techniques, a waterborne polyurethane with a multi-level particle size distribution is prepared. When combined with bio-based complexin, the multi-level latex particles form a matte or even non-glossy coating during film formation. The synthesis process uses bio-based raw materials as much as possible to prepare a highly bio-based self-matting waterborne polyurethane with good flame retardancy.

[0030] Compared with the prior art, the present invention has the following advantages and beneficial effects:

[0031] (1) The bio-based flame-retardant self-matting waterborne polyurethane prepared by the present invention has a high bio-based content: The present invention improves the bio-based content of waterborne polyurethane by replacing the traditional petroleum-based internal emulsifiers dimethylolpropionic acid and dimethylolbutyric acid with bio-based internal emulsifiers. The bio-based carbon content of the bio-based hydrophilic chain extender can reach up to 100%. The bio-based carbon content of the polyurethane emulsion prepared with the bio-based hydrophilic chain extender of the present invention is about 10% higher than that of the polyurethane emulsion prepared with the petroleum-based hydrophilic chain extender, and the bio-based carbon content is as high as 92%. The added flame retardant is also bio-based, which further improves the bio-based content of the product.

[0032] (2) The bio-based flame-retardant self-matting waterborne polyurethane prepared by the present invention has good self-matting effect: The present invention prepares waterborne polyurethane with multi-level particle size distribution by stepwise hydrophilic chain extension. By controlling the molecular structure, addition amount and addition process of the hydrophilic chain extender, the multi-level distribution of waterborne polyurethane particle size is controlled to prepare self-matting waterborne polyurethane. No physical addition of any matting agent is required, which avoids the problems of increased coating brittleness and poor emulsion stability of waterborne polyurethane.

[0033] (3) The bio-based flame-retardant self-matting waterborne polyurethane prepared by the present invention has good flame-retardant effect: The present invention imparts flame-retardant properties to the coating film by adding reactive phosphorus-containing flame retardant, and the coating film has good flame-retardant properties.

[0034] (4) The preparation method of the bio-based flame-retardant self-matting waterborne polyurethane of the present invention uses a combination of vegetable oil polyester polyol and polyether polyol to combine the advantages of polyester polyol and polyether polyol. By changing the molar ratio of the two polyols, the bio-based content and gloss of the emulsion can be easily adjusted, while reducing the cost. At the same time, the introduction of castor oil increases the crosslinking density of the system and improves the mechanical properties, water resistance and solvent resistance of the coating film. Attached Figure Description

[0035] Figure 1 This is a particle size distribution diagram of the bio-based self-masking waterborne polyurethane of Example 1 of the present invention.

[0036] Figure 2 The infrared spectrum of the bio-based self-numbing aqueous polyurethane film of Example 1 of the present invention is shown.

[0037] Figure 3 This is a SEM image of the bio-based self-masking waterborne polyurethane of Example 1 of the present invention.

[0038] Figure 4 These are comparative images of the appearance of Embodiment 1, Comparative Example 1, and a blank glass plate of the present invention. Detailed Implementation

[0039] The present invention will be further described in detail below with reference to the embodiments, but the implementation of the present invention is not limited thereto.

[0040] The bio-based content was calculated according to the definition in GB / T 39514-2020.

[0041] The test methods involved in the embodiments are described as follows:

[0042] Solid content: The solid content of the emulsion was determined according to GB1725-79;

[0043] Emulsion particle size: Particle size was measured using a Malvern Zetasizer Nano ZS90 nanoparticle size potential analyzer (UK).

[0044] Preparation method of coating film: In accordance with the general preparation method of paint film in GB / T1727-1992, the prepared coating is applied to wood, tinplate and glass plate by roller coating. The film thickness is (100±5)um. Then it is completely dried at room temperature for 48h before use.

[0045] Coating gloss: The coating gloss was determined according to GB / T 9754-2007.

[0046] Limiting oxygen index of coating: The limiting oxygen index of coating is determined according to GB / T 2406.2-2009.

[0047] Flame retardant performance indicators of coating: The flame retardant performance indicators of coating are determined according to GB / T 2408-1996.

[0048] Example 1:

[0049] (1) Preparation of a bio-based flame-retardant self-matting waterborne polyurethane emulsion, the raw material components and dosages are shown in Table 1 below by mass.

[0050] Table 1

[0051]

[0052]

[0053] The preparation process includes the following steps:

[0054] 1) Preparation of bio-based hydrophilic chain extender: Bio-based succinic anhydride and natural glycerol were mixed at a molar ratio of 1:0.9, and an appropriate amount of tetrahydrofuran was added. The mixture was reacted at 80-90℃ for 2-3 hours. The tetrahydrofuran was removed by rotary evaporation to obtain the bio-based hydrophilic chain extender.

[0055] 2) Preparation of prepolymer: Bio-based polytetramethylene ether glycol (Mw=1000), castor oil, bio-based hydrophilic chain extender of this embodiment, bio-based 1,4-butanediol, and casein were added to a four-necked flask equipped with a condenser and a stirrer. The mixture was kept at 50℃~65℃ for 30 min, then isophorone diisocyanate and bismuth 2-ethylhexanoate were added. The mixture was kept at 80℃ for 1 h, and then reacted at 80℃ for 2~4 h. During the reaction, an appropriate amount of acetone was added to adjust the viscosity. The reaction was stopped when the NCO mass percentage of the prepolymer reached the theoretical value.

[0056] 3) Preparation of emulsion: Cool to 50℃, add triethylamine (to neutralize 95% molar fraction of carboxyl groups) for 5-15 min, add water and emulsify by shearing at 1300 rpm-1500 rpm, then add sodium 2-[(2-aminoethyl)amino]ethanesulfonate aqueous solution and ethylenediamine aqueous solution in sequence for chain extension and emulsify and disperse at 1300 rpm-1500 rpm for 30-60 min, filter and discharge, and remove acetone by rotary evaporation.

[0057] (2) The properties of flame-retardant bio-based self-matting waterborne polyurethane emulsion are shown in Table 2.

[0058] Table 2

[0059]

[0060] (3) Preparation of bio-based flame-retardant matte coatings: The formulation and composition of bio-based flame-retardant matte waterborne polyurethane wood coatings, by mass parts:

[0061] Table 3

[0062]

[0063] Preparation method: Bio-based flame retardant matte waterborne polyurethane emulsion, defoamer, leveling agent, wetting agent, anti-settling agent and thickener were added to a high-speed shear disperser in sequence and dispersed at 1200-1400 rpm for 10-15 min. Then film-forming aid was added and dispersed at 800 rpm for 10-15 min. The mixture was then filtered through a 200-mesh filter cloth. (4) Performance of bio-based flame retardant matte coating: The performance of the coating was tested and compared with advanced foreign emulsions such as Dutch PD802 emulsion and domestic advanced emulsions such as Carpoly MG063. The results are listed in Table 4.

[0064] Table 4

[0065]

[0066] The particle size distribution diagram of the self-matte waterborne polyurethane in Example 1 is shown below. Figure 1 As shown. By Figure 1 This indicates that the self-matting waterborne polyurethane emulsion of Example 1 has a wide particle size distribution, belonging to a multi-level particle size distribution, ensuring the self-matting effect of the coating film. The infrared spectrum of the self-matting waterborne polyurethane of Example 1 is as follows: Figure 2 As shown. Figure 2 At 3300cm -1 The NH vibration peak is at 1694 cm⁻¹. -1 The peak at 1558 cm⁻¹ is the stretching vibration peak of C=O. Due to the inductive effect, the NH group linked to C=O is an electron-donating group, causing the absorption peak to shift towards lower wavenumbers. These two absorption peaks are mainly formed by the reaction of isocyanate with hydroxyl and amino groups. -1 The nearby absorption peaks are due to the stretching of the urea group (CN). + The NH vibration peak is at 1457 cm⁻¹. -1 The COO is nearby. - The stretching vibration peaks indicate that the hydrophilic carboxylate-type chain extender was successfully introduced into the latex film. In summary, the infrared spectrum demonstrates the successful synthesis of the polymer molecule as intended in the experimental design.

[0067] Figure 3The image shown is a scanning electron microscope (SEM) image of the coating film in Example 1. It clearly shows numerous protruding microspheres on the coating surface, with most of these microspheres having a particle size of 1-2 μm and a relatively wide particle size distribution. During the polyurethane emulsion film formation process, as water evaporates, the latex particles gradually approach, fuse tightly, and then diffuse to form a continuous film. In this process, larger latex particles float to the surface, resulting in a certain surface roughness. When light shines on the coating surface, diffuse reflection occurs, creating a matte surface and reducing glare. Therefore, SEM analysis confirms that the prepared coating surface has a rough physical structure, consistent with the self-masking mechanism. Figure 4 Example 1 shows the coating appearance of the self-matting waterborne polyurethane. This demonstrates that the self-matting waterborne polyurethane of this patent has a high bio-based carbon content, is environmentally friendly, and exhibits excellent matting effects without the addition of any matting medium.

[0068] Dimethylolpropionic acid (DMPA) and dimethylolbutyric acid (DMPO) are the most widely used petroleum-based internal emulsifiers in the synthesis of anionic waterborne polyurethanes. Few studies have attempted to replace these internal emulsifiers with bio-based materials. These two internal emulsifiers have low solubility, and their high melting points result in high homogenization temperatures and prolonged reaction times. Furthermore, the production of these two internal emulsifiers relies on fossil fuels, which is unsustainable. CN 112280459 B discloses a flame-retardant vegetable oil-based waterborne polyurethane coating and its preparation method, which only uses castor oil as the source of bio-based carbon content. In contrast, this invention uses bio-based raw materials, including self-made bio-based hydrophilic monomers, to synthesize a flame-retardant waterborne polyurethane emulsion with high bio-based content, while also exhibiting good flame-retardant and matting effects. CN116284661 A prepares bio-based vegetable oil polyols via a thiol-based click method, and then reacts them with lysine diisocyanate, etc., to prepare waterborne polyurethane. However, the hydrophilic chain extender used is still a petroleum-based chain extender, and the bio-based content of the prepared bio-based polyurethane emulsion needs further improvement.

[0069] Compared to patent CN114853975A, this invention employs a one-step synthesis method for flame-retardant, self-matte waterborne polyurethane, featuring a simple process, rapid reaction, low energy consumption, and ease of large-scale application. The hydrophilic chain extender prepared by this invention is more environmentally friendly and economical. The use of plant oil polyols, including trifunctional castor oil polyols, reduces costs. From a molecular structure perspective, the plant oil fragments in the hydrophilic chain extender improve the biodegradability and water resistance of the polyurethane. The bio-based hydrophilic chain extender can achieve a bio-based carbon content of up to 100%, and the polyurethane emulsion prepared with this bio-based hydrophilic chain extender has approximately 10% higher bio-based carbon content than that prepared with petroleum-based hydrophilic chain extenders, reaching as high as 92%. Compared to patent CN115819704A, this invention utilizes a blend of plant oil polyester polyols and polyether polyols, combining the advantages of both. By changing the molar ratio of the two polyols, the bio-based content and gloss of the emulsion can be easily adjusted, while simultaneously reducing costs. Castor oil and other substances are introduced during the synthesis of polyurethane prepolymers to prepare polyurethanes with multi-branched or hyperbranched structures, thereby controlling the appropriate balance between branching and film formation and improving crosslinking density and chemical resistance.

[0070] Example 2

[0071] (1) Preparation of a bio-based flame-retardant self-matting waterborne polyurethane emulsion, the raw material components and dosages are shown in Table 5 below by mass.

[0072] Table 5

[0073]

[0074] The preparation process includes the following steps:

[0075] 1) Preparation of bio-based hydrophilic chain extender: Bio-based maleic anhydride and bio-based trimethylolpropane were mixed at a molar ratio of 1:1.1, and an appropriate amount of tetrahydrofuran and polymerization inhibitor were added. The mixture was reacted at 80-90℃ for 2-3 hours. The tetrahydrofuran was removed by rotary evaporation to obtain the bio-based hydrophilic chain extender.

[0076] 2) Preparation of prepolymer: Polytrimethylene ether glycol (Mw=1000), castor oil, the bio-based hydrophilic chain extender of this embodiment, 1,3-propanediol, and phytic acid (triethylamine) were added to a four-necked flask equipped with a condenser and a stirrer. The mixture was kept at 50℃~65℃ for 30 min, then pentamethylene diisocyanate and bismuth neodecanoate were added. The mixture was kept at 80℃ for 1 h, and then reacted at 80℃ for 2~4 h. During the reaction, an appropriate amount of butanone was added to adjust the viscosity. The reaction was stopped when the NCO mass percentage of the prepolymer reached the theoretical value.

[0077] 3) Preparation of emulsion: Cool to 50℃, add triethylamine (to neutralize 90% molar fraction of carboxyl groups) for 5-15 min, add water and emulsify by shearing at 1300 rpm-1500 rpm, then add sodium 3-[(2-aminoethyl)amino]propanesulfonate and triethylenetetramine aqueous solution sequentially for chain extension and emulsify and disperse at 1300 rpm-1500 rpm for 30-60 min, filter and discharge, and remove butanone by rotary evaporation.

[0078] (2) The properties of flame-retardant bio-based self-matting waterborne polyurethane emulsion are shown in Table 6.

[0079] Table 6

[0080]

[0081] (3) Preparation of bio-based flame-retardant matte coatings: The formulation and composition of bio-based flame-retardant matte waterborne polyurethane wood coatings, by mass parts:

[0082] Table 7

[0083]

[0084]

[0085] Preparation method: Flame-retardant matte waterborne polyurethane emulsion, defoamer, leveling agent, anti-settling agent and thickener are added to a high-speed shear disperser in sequence and dispersed at 1200-1400 rpm for 10-15 minutes. Then, film-forming aid is added and dispersed at 800 rpm for 10-15 minutes. The mixture is then filtered through a 200-mesh filter cloth.

[0086] (4) Performance of bio-based flame-retardant matte coatings: The performance of the coatings was tested and compared with advanced foreign emulsions such as Dutch PD802 emulsion and domestic advanced emulsions such as Carpoly MG063. The results are listed in Table 8.

[0087]

[0088] Example 3:

[0089] (1) Preparation of a bio-based flame-retardant self-matting waterborne polyurethane emulsion, the raw material components and dosages are shown in Table 9 below by mass.

[0090] Table 9

[0091]

[0092] The preparation process includes the following steps:

[0093] 1) Preparation of bio-based hydrophilic chain extender: Bio-based itaconic anhydride and trifunctional castor oil polyol were mixed at a molar ratio of 1:1, and an appropriate amount of tetrahydrofuran and polymerization inhibitor were added. The mixture was reacted at 80-90℃ for 2-3 hours. The tetrahydrofuran was removed by rotary evaporation to obtain the bio-based hydrophilic chain extender.

[0094] 2) Preparation of prepolymer: Castor oil, the bio-based hydrophilic chain extender of this embodiment, 1,4-butanediol, and phytic acid (tetramethylethylenediamine) were added to a four-necked flask equipped with a condenser and a stirrer. The mixture was kept at 50℃~65℃ for 30 min, then dimer diisocyanate and bismuth neodecanoate were added. The mixture was kept at 80℃ for 1 h, and then reacted at 80℃ for 2~4 h. During the reaction, an appropriate amount of butanone was added to adjust the viscosity. The reaction was stopped when the NCO mass percentage of the prepolymer reached the theoretical value.

[0095] 3) Preparation of emulsion: Cool to 40℃, add triethylamine (to neutralize 80% molar fraction of carboxyl groups) for 5-15 min, add water and shear emulsify at 1300 rpm-1500 rpm, then add sodium ethylenediamine ethanesulfonate and diethylenetriamine aqueous solution sequentially for chain extension and emulsify and disperse at 1300 rpm-1500 rpm for 30-60 min, filter and discharge, and remove methyl ethyl ketone by rotary evaporation.

[0096] (2) The properties of flame-retardant bio-based self-matting waterborne polyurethane emulsion are shown in Table 10.

[0097] Table 10

[0098]

[0099] (3) Preparation of bio-based flame-retardant matte coatings: The formulation and composition of bio-based flame-retardant matte waterborne polyurethane wood coatings, by mass parts:

[0100] Table 11

[0101]

[0102]

[0103] Preparation method: Flame-retardant matte waterborne polyurethane emulsion, defoamer, leveling agent, anti-settling agent and thickener are added to a high-speed shear disperser in sequence and dispersed at 1200-1400 rpm for 10-15 minutes. Then, film-forming aid is added and dispersed at 800 rpm for 10-15 minutes. The mixture is then filtered through a 200-mesh filter cloth.

[0104] (4) Performance of bio-based flame retardant matte coating: The performance of the coating was tested and compared with advanced foreign emulsions such as Dutch PD802 emulsion and domestic advanced emulsions such as Carpoly MG063. The results are listed in Table 12.

[0105] Table 12

[0106]

[0107] Example 4:

[0108] (1) Preparation of a bio-based flame-retardant self-matting waterborne polyurethane emulsion, the raw material components and dosages are shown in Table 13 below by mass.

[0109] Table 13

[0110]

[0111]

[0112] The preparation process includes the following steps:

[0113] 1) Preparation of bio-based hydrophilic chain extender: Bio-based succinic anhydride and trifunctional cashew nut polyol were mixed at a molar ratio of 1:1, and an appropriate amount of tetrahydrofuran and polymerization inhibitor were added. The mixture was reacted at 80-90℃ for 2-3 hours. The tetrahydrofuran was removed by rotary evaporation to obtain the bio-based hydrophilic chain extender.

[0114] 2) Preparation of the prepolymer: Castor oil, the bio-based hydrophilic chain extender of this embodiment, 1,4-butanediol, and casein were added to a four-necked flask equipped with a condenser and a stirrer. The mixture was kept at 50℃~65℃ for 30 min, followed by the addition of lysine diisocyanate and bismuth neodecanoate. The reaction was maintained at 1 h, and then at 80℃ for 2~4 h. During the reaction, an appropriate amount of acetone was added to adjust the viscosity. The reaction was stopped when the NCO mass percentage of the prepolymer reached the theoretical value. 3) Preparation of the emulsion: The temperature was lowered to 50℃, and triethylamine (to neutralize 110% molar fraction of carboxyl groups) was added for neutralization for 5~15 min. Water was added and sheared at 1300 rpm~1500 rpm for emulsification. Then, sodium ethylenediamine ethanesulfonate and diethylenetriamine aqueous solution were added sequentially for chain extension and emulsified and dispersed at 1300 rpm~1500 rpm for 30~60 min. The mixture was filtered and discharged, and acetone was removed by rotary evaporation.

[0115] (2) The properties of flame-retardant bio-based self-matting waterborne polyurethane emulsion are shown in Table 14.

[0116] Table 14

[0117]

[0118]

[0119] (3) Preparation of bio-based flame-retardant matte coatings: The formulation and composition of bio-based flame-retardant matte waterborne polyurethane wood coatings, by mass parts:

[0120] Table 15

[0121]

[0122] Preparation method: Flame-retardant matte waterborne polyurethane emulsion, defoamer, leveling agent, wetting agent, anti-settling agent and thickener are added to a high-speed shear disperser in sequence and dispersed at 1200-1400 rpm for 10-15 min. Then film-forming aid is added and dispersed at 800 rpm for 10-15 min. The mixture is then filtered through a 200-mesh filter cloth. (4) Performance of bio-based flame-retardant matte coating: The performance of the coating is tested and compared with advanced foreign emulsions such as Dutch PD802 emulsion and domestic advanced emulsions such as Carpoly MG063. The results are listed in Table 16.

[0123] Table 16

[0124]

[0125]

[0126] Comparative Example 1: A bio-based flame-retardant matte waterborne polyurethane wood coating was prepared by compounding Dow's acrylic emulsion RN1100V with Dutch PD802 emulsion, which has a 30% bio-based content.

[0127] Formulation and composition of bio-based flame-retardant matte waterborne polyurethane wood coatings, by weight:

[0128] Table 17

[0129]

[0130] Comparative Example 2: Bio-based flame-retardant matte waterborne polyurethane wood coating was prepared by compounding DSM acrylic emulsion SP8405 with Dutch PD802 emulsion, which has a bio-based content of 48%.

[0131] Formulation and composition of bio-based flame-retardant matte waterborne polyurethane wood coatings, by weight:

[0132] Table 18

[0133]

[0134] Comparative Example 3: A bio-based flame-retardant matte waterborne polyurethane wood coating was prepared by compounding DSM acrylic emulsion SP8405 with Carpoly MG063 emulsion, which has a bio-based content of 48%.

[0135] Formulation and composition of bio-based flame-retardant matte waterborne polyurethane wood coatings, by weight:

[0136] Table 19

[0137]

[0138]

[0139] Performance summary table of Examples 1-4 and Comparative Examples 1-3

[0140] Table 20

[0141]

[0142] Note:

[0143] Gloss: The self-matte waterborne polyurethane sample was coated onto a glass plate, dried into a film, and then tested.

[0144] As shown in Table 20, the self-matting waterborne polyurethanes of Examples 1-4 not only have excellent matting effects without the addition of any matting medium, but also have high bio-based content and are green and environmentally friendly.

[0145] The above embodiments are preferred embodiments of the present invention, but the embodiments of the present invention are not limited to the embodiments described above. Any changes, modifications, substitutions, combinations, or simplifications made without departing from the spirit and principle of the present invention shall be considered equivalent substitutions and shall be included within the protection scope of the present invention.

Claims

1. A method for preparing a bio-based flame-retardant, self-matting waterborne polyurethane, characterized in that, Includes the following steps: (1) Preparation of bio-based hydrophilic chain extender: Bio-based acid anhydride and bio-based triol are mixed at a molar ratio of 1:0.9~1.1, organic solvent is added, and the mixture is reacted at 80~90℃ for 2~3h. The organic solvent is removed by rotary evaporation to obtain bio-based dihydroxycarboxylic acid, i.e. bio-based hydrophilic chain extender. The bio-based acid anhydride is at least one of succinic anhydride, maleic anhydride, and itaconic anhydride; the bio-based triol is at least one of natural glycerol, bio-based trimethylolpropane, trifunctional castor oil polyol, and trifunctional cashew nut polyol. (2) Preparation of prepolymer: Bio-based polyether glycol, vegetable oil polyol, bio-based hydrophilic chain extender, bio-based chain extender and bio-based flame retardant are mixed at 40℃~60℃ for 30min~60min, then diisocyanate and catalyst are added and reacted at 60℃~85℃ for 3~6h to obtain isocyanate-terminated prepolymer. During the reaction, organic solvent is added to reduce viscosity. The bio-based polyether glycol is at least one of bio-based polytetrahydrofuran glycol and bio-based polytrimethylene ether glycol; the vegetable oil polyol is at least one of castor oil and castor oil polyol; the bio-based chain extender is at least one of bio-based 1,3-propanediol and bio-based 1,4-butanediol; the catalyst is bismuth neodecanoate; and the bio-based flame retardant is at least one of casein and phytic acid derivatives. (3) Emulsion preparation: Cool down to 40℃~50℃, add neutralizing agent to the prepolymer in step (2) and carry out neutralization reaction; add water for high-speed emulsification, then add sulfonate type chain extender aqueous solution and amine chain extender aqueous solution in sequence, emulsify and extend chain for 30~60min, filter and discharge to obtain bio-based flame retardant self-matting waterborne polyurethane emulsion with multi-level particle size distribution; The amount of the bio-based hydrophilic chain extender used is 1.8% to 3.5% of the total mass of the plant oil polyol, bio-based polyether diol, bio-based hydrophilic chain extender, bio-based chain extender, sulfonate chain extender, amine chain extender, and diisocyanate.

2. The preparation method of bio-based flame-retardant self-matting waterborne polyurethane according to claim 1, characterized in that, The sulfonate-type chain extender is sodium 2-[(2-aminoethyl)amino]ethanesulfonate.

3. The preparation method of bio-based flame-retardant self-matting waterborne polyurethane according to claim 1, characterized in that, The amine chain extender is at least one of ethylenediamine, diethylenetriamine, triethylenetetramine, and tetraethylenepentamine.

4. The preparation method of bio-based flame-retardant self-matting waterborne polyurethane according to claim 1, characterized in that, The neutralizing agent is a tertiary amine neutralizing agent, and its amount is 70% to 120% of the amount of the bio-based hydrophilic chain extender.

5. The preparation method of bio-based flame-retardant self-matting waterborne polyurethane according to claim 1, characterized in that, The phytic acid derivative is a product of the reaction between phytic acid and an organic amine; the organic amine is one of triethylamine and tetramethylethylenediamine.

6. The preparation method of bio-based flame-retardant self-matting waterborne polyurethane according to claim 1, characterized in that, The organic solvent is at least one of acetone and butanone.

7. The preparation method of bio-based flame-retardant self-matting waterborne polyurethane according to claim 1, characterized in that, The amount of isocyanate in the diisocyanate is 1 to 2.5 times the total amount of the hydroxyl groups in the vegetable oil polyol, bio-based polyether glycol, bio-based hydrophilic chain extender, and bio-based chain extender.

8. The preparation method of bio-based flame-retardant self-matting waterborne polyurethane according to claim 1, characterized in that, The amounts of each raw material used in the reaction, by mass, are as follows: The emulsion contains 1-15 parts of bio-based polyether glycol, 0.5-8 parts of vegetable oil polyol, 0.5-5 parts of bio-based hydrophilic chain extender, 0.1-1.5 parts of bio-based chain extender, 0.05 parts of organic bismuth catalyst, 8-18 parts of diisocyanate, 1-5 parts of bio-based flame retardant, 0.2-0.5 parts of neutralizer, 0.4-1 parts of sulfonate chain extender, and 0.5-1.2 parts of amine chain extender; the amount of water added is such that the solid content of the emulsion is 20%-35%.

9. A bio-based flame-retardant matte coating, characterized in that, The bio-based flame-retardant self-matting waterborne polyurethane prepared by the method described in any one of claims 1 to 8 includes the bio-based flame-retardant self-matting waterborne polyurethane.

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