A bio-based intumescent waterborne fire-retardant coating with strong adhesion and a preparation method thereof

Abstract

The application discloses a kind of biological base intumescent water-based fire-retardant coating with strong adhesion and preparation method thereof, the coating is made of the following weight parts of raw materials: deionized water 100-300 parts, gluconate 10-40 parts, chitosan salt 10-30 parts, phytic acid 40-45 parts, anti-aging agent 1-2 parts, anti-freezing and thawing aid 0.3-0.4 parts.The fire-retardant coating of the application is suitable for a variety of substrates, solves the problem of short service life of coating caused by weak bonding force between coating and substrate;The fire-retardant coating has high fire-retardant efficiency, and the coating thickness of about 200 μm can effectively flame-retard polypropylene, vertical combustion passes UL-94 V-0 level, limiting oxygen index (LOI) is 46.1%, the coating rapidly expands about 100 times after fire, the carbon layer is honeycomb-shaped inside, the carbon layer surface is continuous and dense, and the condensed phase fire-retardant effect is remarkable;The preparation method of the coating is simple, the coating is highly transparent and smooth, has the advantages of easy processing, energy saving and emission reduction, wide application, etc.

Description

Technical Field

[0001] This invention relates to a transparent bio-based intumescent waterborne flame retardant coating with strong adhesion properties and its preparation method, as well as the application of the flame retardant coating on substrates such as plastics, wood, rigid polyurethane foam, and wallpaper, belonging to the field of environmentally friendly waterborne intumescent flame retardant coating preparation technology. Background Technology

[0002] Many combustible and flammable materials release a large amount of heat and produce dense smoke and toxic gases during combustion. Fires caused by these materials pose a serious threat to human life and property every year. Although traditional flame retardant technologies have achieved some success, the increasing demands for flame retardant performance, such as high flame retardant efficiency, flame retardant durability, low heat release, less smoke, and low emissions of toxic gases, as well as the requirement that improving flame retardant performance should not affect or even worsen the inherent properties of flammable materials, have led to more and more challenges in the application of flame retardant technology.

[0003] Flame-retardant coatings are functional materials that typically achieve flame-retardant or fire-resistant properties by adding flame retardants to film-forming agents that lack flame-retardant properties. They are widely used for flame retardant wood and fireproofing steel plates. Flame-retardant coatings are easy to apply, using various methods such as roller coating, dip coating, brush coating, and spray coating. The flame-retardant coating serves both decorative and protective purposes for the substrate, while also reducing the impact of flames on the substrate. Water-based coatings, due to their absence of organic solvents, have become a new type of environmentally friendly coating. The film-forming agents are mainly water-based organic resins (water-based polyurethane, water-based acrylate, water-based epoxy resin, etc.), and adding flame retardants creates water-based flame-retardant coatings. In recent years, bio-based materials have received considerable attention due to their green, environmentally friendly, and renewable advantages, making bio-based coatings a key element in the coating industry for carbon reduction and emission reduction.

[0004] Chinese patent CN112662235A discloses "A water-based bio-based flame-retardant luminescent coating and its preparation method and application." This method prepares a water-based bio-based flame-retardant luminescent coating, which is applied to the preparation of flame-retardant wood. The coating is directly brushed onto the wood surface and dried at room temperature for more than 12 hours. However, the bonding strength between the coating and the substrate is unknown, and it lacks light transmittance. After drying, the coating appears milky white under natural light and glows in the dark, making it unsuitable for certain materials that require the preservation of their inherent properties. Chinese patent CN112175435A discloses "A flame-retardant and antibacterial coating for aluminum alloy doors and windows and its preparation method." This method involves spraying 2-3 layers of the flame-retardant and antibacterial coating onto the surface of aluminum alloy doors and windows. After the coating has cured and formed a film on the surface, a flame-retardant and antibacterial coating is formed. However, this flame-retardant and antibacterial coating requires a wide variety of materials and involves cumbersome preparation steps. Chinese patent CN116239931A discloses "Preparation of a waterborne epoxy intumescent fire-retardant coating based on phytochemical-complexed copper ions (h-BN)". This invention uses melamine (MEL), pentaerythritol (PER), and ammonium polyphosphate (APP) in its coating preparation process, thus relying on non-renewable resources. Furthermore, the coating preparation steps are cumbersome, requiring 7 days of curing at room temperature and 3 days of baking at 40°C after application, resulting in a long curing time and harsh curing conditions. Chinese patent CN202211697762.2 discloses "Preparation method of a bio-based intumescent flame retardant for interior wall coatings", but the resulting bio-based intumescent flame retardant requires the addition of a film-forming agent before use.

[0005] The aforementioned flame-retardant coatings are all additive-based. The addition of flame retardants disrupts the continuity of the film-forming phase, leading to reduced coating adhesion and mechanical properties. Adhesion directly affects the stability and longevity of the flame-retardant coating, and also the firmness of the char layer formed in the flame. Therefore, high adhesion is one of the essential properties of flame-retardant coatings. Furthermore, additive-based flame-retardant coatings are generally opaque, limiting their application areas. Therefore, developing a bio-based waterborne flame-retardant coating that combines flame retardancy, strong adhesion, transparency, and antibacterial properties, and is suitable for various substrates, has significant practical implications and application value. This would not only meet the requirements of green environmental protection but also broaden the application scope of flame-retardant coatings. Summary of the Invention

[0006] To address the shortcomings of existing technologies, this invention provides a bio-based intumescent waterborne flame-retardant coating with strong adhesion properties and its preparation method. The resulting coating possesses flame-retardant, strong adhesion, transparency, and antibacterial properties, and is suitable for various substrates. It not only meets the concept of green environmental protection but also broadens the application range of flame-retardant coatings.

[0007] Mechanism of this invention: This invention utilizes a sol-gel method to react gluconate, phytic acid, and chitosan salt at room temperature to form a flame-retardant functional coating. The gluconate and chitosan salt structures contain abundant hydroxyl groups, which, under the strong chelating and dehydrating effects of phytic acid, form a chemically cross-linked structure. Simultaneously, the remaining hydroxyl and amino groups form a physically and chemically cross-linked network structure through hydrogen bonding. The flame-retardant system is also a film-forming system; therefore, this coating does not require the separate addition of film-forming substances and possesses intrinsic flame-retardant characteristics. Compared to additive flame-retardant coatings, the continuous phase of this coating remains intact, the flame-retardant components are more uniformly distributed, and the flame-retardant efficiency is higher.

[0008] The ternary system composed of gluconate, chitosan salt, and phytic acid contains a large number of hydroxyl groups. The resulting coating undergoes hydrogen bonding with the active functional groups on the substrate surface, thus giving the coating strong adhesion. In this ternary system, chitosan salt and gluconate can act as carbon and gas sources in the flame-retardant coating, while phytic acid acts as an acid source, fully meeting the requirements for intumescent flame retardancy. Under high temperature or flame conditions, the flame-retardant coating applied to the protected substrate undergoes vigorous expansion, carbonization, and foaming, forming a non-combustible honeycomb char layer that is tens of times thicker than the original coating. The honeycomb structure is filled with non-combustible gas, producing excellent heat insulation, effectively preventing heat transfer to the substrate, and maintaining a lower temperature for a certain period of time. Secondly, the physical changes such as softening, melting, and expansion of the coating, as well as the chemical reactions such as the decomposition and cross-linking carbonization of phytic acid, chitosan salt, and gluconate in the coating, absorb a large amount of heat, reducing the combustion temperature and flame propagation speed. Thirdly, metal ions can catalyze char formation and stabilize the char layer, further helping the flame-retardant coating achieve excellent flame-retardant performance.

[0009] The flame-retardant coating of this invention is highly transparent, with a light transmittance of over 90%, serving not only an aesthetic purpose but also expanding the application range of flame-retardant coatings. Chitosan salts, metal ions, and phytic acid all possess antibacterial properties, endowing the flame-retardant coating with antibacterial characteristics. Furthermore, this flame-retardant coating is water-based, and the flame retardants are all biomass materials, widely available, and the coating preparation method is simple, green, and energy-saving.

[0010] This invention provides a bio-based intumescent waterborne flame-retardant coating with strong adhesion properties, made from the following raw materials in parts by weight:

[0011] 100-300 parts deionized water

[0012] 10-40 parts of gluconate

[0013] 10-30 parts chitosan salt

[0014] 40-45 parts phytic acid

[0015] 1-2 parts of anti-aging agent

[0016] 0.3-0.4 parts of antifreeze-thaw agent.

[0017] In the above scheme, the gluconate includes, but is not limited to, one of calcium gluconate, sodium gluconate, magnesium gluconate, or a combination thereof (when multiple combinations are used, they are mixed in any proportion).

[0018] In the above scheme, the chitosan salt includes, but is not limited to, one or a combination of chitosan quaternary ammonium salt, chitosan hydrochloride, chitosan lactate, and chitosan nitrate (mixed in any proportion when multiple combinations are used), with a degree of substitution ≥80%.

[0019] In the above scheme, the phytic acid is a 50-70 wt.% phytic acid solution.

[0020] In the above scheme, the anti-aging agent is any one of UV-770, UV-531, and anti-aging agent 1010, in order to improve the anti-aging ability of the coating.

[0021] In the above scheme, the antifreeze-thaw additive is Clariant's environmentally friendly, scrub-resistant, and antifreeze-thaw additive Genapol 2070, which is used to improve the freeze-thaw resistance of the coating.

[0022] This invention provides a method for preparing the above-mentioned bio-based intumescent waterborne flame-retardant coating with strong adhesion properties, comprising the following steps:

[0023] (1) Add deionized water and gluconate to a beaker and stir in a water bath at 50-80℃ until completely dissolved;

[0024] (2) After the solution is cooled to room temperature, chitosan salt is slowly added and stirred at 100-200 rpm for 1-1.5 h at room temperature to disperse it evenly;

[0025] (3) Slowly add phytic acid solution and stir at 100-200 rpm for 30-60 min at room temperature;

[0026] (4) Add anti-aging agent and anti-freeze-thaw agent, and stir at 100 rpm for 20 min; after mixing evenly, a bio-based intumescent water-based flame retardant coating with strong adhesion is obtained.

[0027] This invention provides the application of the above-mentioned bio-based intumescent waterborne flame retardant coating with strong adhesion properties.

[0028] The bio-based intumescent waterborne flame retardant coating with strong adhesion provided by this invention has applications including, but not limited to, substrates such as plastics, wood, wallpaper, rigid polyurethane foam, and steel.

[0029] When the bio-based intumescent waterborne flame retardant coating with strong adhesion provided by this invention is applied to plastics or other substrates with low surface polarity, the substrate surface needs to be simply pretreated, including any one of the following methods: flame burning, sanding, and adhesion treatment agent treatment.

[0030] The bio-based intumescent waterborne flame-retardant coating with strong adhesion provided by this invention is suitable for application methods including: scraping, brushing, dipping, or roller coating. The coating should be dried at 15–35°C for 18–24 hours. Multiple coats are recommended when the dried coating thickness exceeds 200 μm.

[0031] When the bio-based intumescent waterborne flame-retardant coating with strong adhesion provided by this invention is applied to steel plate fireproofing, it is necessary to pre-coat the steel plate surface with any one of acrylic emulsion, silicone resin or wood wax oil as a primer with a thickness of about 50~150 μm. After the primer dries, the flame-retardant coating of this invention is coated on the steel plate surface with the primer as a topcoat. The flame-retardant coating thickness should be ≥1500 μm, and it is applied in 4-6 coats.

[0032] The bio-based intumescent waterborne flame-retardant coating with strong adhesion provided by this invention meets the requirements of adhesives due to its strong adhesion and can also be used as a flame-retardant adhesive for bonding various materials.

[0033] The beneficial effects of this invention are:

[0034] (1) The flame-retardant coating of the present invention is applicable to a variety of substrates. Even polyolefin materials with very low surface energy can be coated with a strong interface bond by performing simple surface treatment (flame burning method, grinding method and adhesion treatment), which solves the problem of low service life of coating due to weak bonding between coating and substrate and expands the application range of coating.

[0035] (2) The flame retardant coating of the present invention has high flame retardant efficiency. The coating thickness of about 200 μm can effectively retard polypropylene. It passes the UL-94 V-0 level in vertical combustion with an LOI of 46.1%. After being exposed to fire, the coating expands rapidly by about 100 times. The interior of the char layer is honeycomb-shaped, and the surface of the char layer is continuous and dense, with significant flame retardant effect of condensed phase.

[0036] (3) The flame-retardant coating preparation method of the present invention is simple, the coating is highly transparent and smooth, and has the advantages of convenient processing, energy saving and emission reduction, and wide application.

[0037] (4) The flame-retardant coating of the present invention is a water-based coating, and the raw materials are gluconate, chitosan salt and phytic acid, which belong to biomass renewable resources and have the advantages of being green and environmentally friendly; and have good antibacterial properties. Attached Figure Description

[0038] Figure 1The data are cone calorimetry test data for Examples 1 and 2.

[0039] Figure 2 The back temperature data are for the steel plate and polypropylene plate with flame-retardant coating in Example 3.

[0040] Figure 3 The data shows the light transmittance of the flame-retardant coating in Example 3.

[0041] Figure 4 This is a comparison of the coating adhesion data of the flame-retardant coating in Example 3, the commercially available acrylic emulsion, and the flame-retardant acrylic coating in Comparative Example 2. Detailed Implementation

[0042] The present invention will be further illustrated by the following embodiments, but is not limited to the following embodiments. Example 1

[0043] The preparation method of a bio-based intumescent waterborne flame retardant coating with strong adhesion properties described in this example includes the following steps (in parts by mass):

[0044] (1) Add 120 parts of deionized water and 28 parts of calcium gluconate to a beaker and stir in a water bath at 60°C until completely dissolved;

[0045] (2) After the solution is cooled to room temperature, slowly add 12 parts of chitosan quaternary ammonium salt and stir at 100 rpm for 1.5 h at room temperature to disperse it evenly.

[0046] (3) Slowly add 28 parts of 50 wt.% phytic acid solution and stir at 100 rpm for 40 min at room temperature;

[0047] (4) Add 1 part of anti-aging agent 1010 and 0.3 parts of Genapol 2070, and stir at 100 rpm for 20 min. After mixing evenly, a bio-based intumescent waterborne flame retardant coating with strong adhesion properties is obtained.

[0048] Application 1: The flame-retardant coating of Example 1 was applied to the polypropylene surface treated with an adhesion promoter by scraping. The coating was dried at 18°C ​​for 20 h to obtain flame-retardant polypropylene. The thickness of the coating on one side after drying was 200 μm. It was used for limiting oxygen index (LOI) and vertical burning test (UL-94).

[0049] Application 2: An acrylic emulsion was applied to the surface of a steel plate as a primer using a scraping method, with a thickness of 50 μm. After the primer dried, the flame-retardant coating of Example 1 was applied to the primer-coated steel plate surface as a topcoat. The coating thickness on one side was 1500 μm after drying, and it was applied in 5 coats. After drying, a fireproof steel plate was obtained and used for back temperature testing. The flame-retardant coating of Example 1 was applied to the surface of a flame-burned polypropylene using a scraping method. The coating was dried at 18°C ​​for 20 h. The coating thickness on one side was 1500 μm after drying, and it was applied in 5 coats. The flame-retardant polypropylene obtained after drying was used for back temperature testing. Example 2

[0050] The preparation method of a bio-based intumescent waterborne flame retardant coating with strong adhesion properties described in this example includes the following steps (in parts by mass):

[0051] (1) Add 140 parts of deionized water and 21 parts of sodium gluconate to a beaker and stir in a water bath at 60°C until completely dissolved;

[0052] (2) After the solution is cooled to room temperature, slowly add 18 parts of chitosan quaternary ammonium salt and stir at 100 rpm for 1.5 h at room temperature to disperse it evenly.

[0053] (3) Slowly add 26 parts of 50 wt.% phytic acid solution and stir at 100 rpm for 40 min at room temperature;

[0054] (4) Add 1.5 parts UV-770 and 0.3 parts Genapol 2070, and stir at 100 rpm for 20 min. After mixing evenly, a bio-based intumescent waterborne flame retardant coating with strong adhesion is obtained.

[0055] Application 1: The flame-retardant coating of Example 2 was applied to the surface of polypropylene that had been sanded by brushing. The coating was dried at 25°C for 18 h to obtain flame-retardant polypropylene. The coating thickness on one side after drying was 200 μm. It was used for limiting oxygen index (LOI) and vertical burning test (UL-94).

[0056] Application 2: An acrylic emulsion was applied to the surface of a steel plate as a primer by brushing, with a thickness of 80 μm. After the primer dried, the flame-retardant coating of Example 2 was applied as a topcoat to the steel plate surface with the primer. The coating thickness on one side was 1500 μm after drying, and it was applied in 4 coats. After drying, a fireproof steel plate was obtained and used for back temperature testing. The flame-retardant coating of Example 2 was applied to the surface of a polypropylene that had been burned by a flame by brushing. The coating was dried at 25°C for 18 h. The coating thickness on one side was 1500 μm after drying, and it was applied in 4 coats. The flame-retardant polypropylene obtained after drying was used for back temperature testing. Example 3

[0057] The preparation method of a bio-based intumescent waterborne flame retardant coating with strong adhesion properties described in this example includes the following steps (in parts by mass):

[0058] (1) Add 160 parts of deionized water and 18 parts of magnesium gluconate to a beaker and stir in a water bath at 70°C until completely dissolved;

[0059] (2) After the solution is cooled to room temperature, slowly add 20 parts of chitosan lactate and stir at 200 rpm for 1 h at room temperature to disperse it evenly.

[0060] (3) Slowly add 20 parts of 70 wt.% phytic acid solution and stir at 200 rpm for 30 min at room temperature;

[0061] (4) Add 1.8 parts of UV-770 and 0.3 parts of Genapol 2070, and stir at 100 rpm for 20 min. After mixing evenly, a bio-based intumescent waterborne flame retardant coating with strong adhesion properties is obtained.

[0062] Application 1: The flame-retardant coating of Example 3 was applied to the flame-burned polypropylene surface by scraping. The coating was dried at 28°C for 15 h to obtain flame-retardant polypropylene. The thickness of the coating on one side after drying was 200 μm. It was used for limiting oxygen index (LOI) and vertical burning test (UL-94).

[0063] Application 2: An acrylic emulsion was applied to the surface of a steel plate as a primer using a scraping method, with a thickness of 100 μm. After the primer dried, the flame-retardant coating of Example 3 was applied to the steel plate surface as a topcoat. The coating thickness on one side was 1500 μm after drying, and it was applied in 4 coats. After drying, a fireproof steel plate was obtained and used for back temperature testing. The flame-retardant coating of Example 3 was applied to the surface of a polypropylene that had been burned by a flame using a scraping method. The coating was dried at 28°C for 15 h. The coating thickness on one side was 1500 μm after drying, and it was applied in 4 coats. The flame-retardant polypropylene obtained after drying was used for back temperature testing.

[0064] Application 3: Apply the flame-retardant coating of Example 3 (coating thickness of about 200 μm) evenly to both ends of the polyurethane foam. After placing it at room temperature for 6 hours, bond the coating surfaces that are not completely dry together. Place it at room temperature for 12 hours to obtain the bonded polyurethane foam. Example 4

[0065] The preparation method of a bio-based intumescent waterborne flame retardant coating with strong adhesion properties described in this example includes the following steps (in parts by mass):

[0066] (1) Add 180 parts of deionized water and 14 parts of sodium gluconate to a beaker and stir in an 80°C water bath until completely dissolved;

[0067] (2) After the solution is cooled to room temperature, slowly add 24 parts of chitosan hydrochloride and stir at 150 rpm for 1.2 h at room temperature to disperse it evenly.

[0068] (3) Slowly add 16 parts of 50 wt.% phytic acid solution and stir at 150 rpm for 35 min at room temperature;

[0069] (4) Add 2 parts of UV-resistant 531 and 0.4 parts of Genapol 2070, and stir at 100 rpm for 20 min. After mixing evenly, a bio-based intumescent waterborne flame retardant coating with strong adhesion properties is obtained.

[0070] Application 1: The flame-retardant coating of Example 4 was applied to the surface of polypropylene that had been burned by a flame by dip coating. The coating was dried at 30°C for 12 h to obtain flame-retardant polypropylene. The thickness of the coating on one side after it was completely dry was 200 μm. It was used for limiting oxygen index (LOI) and vertical burning test (UL-94).

[0071] Application 2: An acrylic emulsion was applied to the surface of a steel plate as a primer by dip coating, with a thickness of 70 μm. After the primer dried, the flame-retardant coating of Example 4 was applied as a topcoat to the primer-coated steel plate surface. The coating thickness on one side was 1500 μm after drying, and it was applied in 4 coats. After drying, a fireproof steel plate was obtained and used for back temperature testing. The flame-retardant coating of Example 4 was applied to the surface of a flame-burned polypropylene by dip coating. The coating was dried at 30°C for 12 h. The coating thickness on one side was 1500 μm after drying, and it was applied in 4 coats. The flame-retardant polypropylene obtained after drying was used for back temperature testing. Example 5

[0072] The preparation method of a bio-based intumescent waterborne flame retardant coating with strong adhesion properties described in this example includes the following steps (in parts by mass):

[0073] (1) Add 240 parts of deionized water and 14 parts of sodium gluconate to a beaker and stir in a water bath at 50°C until completely dissolved;

[0074] (2) After the solution is cooled to room temperature, slowly add 28 parts of chitosan hydrochloride and stir at 200 rpm for 1 h at room temperature to disperse it evenly.

[0075] (3) Slowly add 14 parts of 70 wt.% phytic acid solution and stir at 200 rpm for 20 min at room temperature;

[0076] (4) Add 0.2 parts of dimethylsiloxane, 2 parts of anti-aging agent 1010 and 0.4 parts of Genapol 2070, and stir at 100 rpm for 30 min. After mixing evenly, a bio-based intumescent waterborne flame retardant coating with strong adhesion is obtained.

[0077] Application 1: The flame-retardant coating of Example 5 was applied to the surface of polypropylene that had been burned by a flame by roller coating. The coating was dried at 35°C for 10 h to obtain flame-retardant polypropylene. The thickness of the coating on one side after it was completely dry was 200 μm. It was used for limiting oxygen index (LOI) and vertical burning test (UL-94).

[0078] Application 2: An acrylic emulsion was coated onto a steel plate surface as a primer using a roller coating method, with a thickness of 60 μm. After the primer dried, the flame-retardant coating of Example 5 was coated onto the primer-coated steel plate surface as a topcoat. The coating thickness on one side was 1500 μm after drying, and it was applied in 6 coats. After drying, a fireproof steel plate was obtained and used for back temperature testing. The flame-retardant coating of Example 4 was coated onto a flame-burned polypropylene surface using a roller coating method. The coating was dried at 35°C for 10 h. The coating thickness on one side was 1500 μm after drying, and it was applied in 6 coats. The flame-retardant polypropylene obtained after drying was used for back temperature testing. Example 6

[0079] The preparation method of a bio-based intumescent waterborne flame retardant coating with strong adhesion properties described in this example includes the following steps (in parts by mass):

[0080] (1) Add 200 parts of deionized water and 12 parts of magnesium gluconate to a beaker and stir in a water bath at 70°C until completely dissolved;

[0081] (2) After the solution is cooled to room temperature, slowly add 26 parts of chitosan lactate and stir at 200 rpm for 1 h at room temperature to disperse it evenly.

[0082] (3) Slowly add 16 parts of 70 wt.% phytic acid solution and stir at 200 rpm for 30 min at room temperature;

[0083] (4) Add 1.8 parts of UV-770 and 0.3 parts of Genapol 2070, and stir at 100 rpm for 20 min. After mixing evenly, a bio-based intumescent waterborne flame retardant coating with strong adhesion properties is obtained.

[0084] Application: The flame-retardant coating of Example 6 was applied to the surface of wood, polyurethane foam and wallpaper by scraping. The coating was dried at 20°C for 18 h to obtain flame-retardant wood, flame-retardant polyurethane foam and flame-retardant wallpaper. The thickness of the coating on one side after drying was 200 μm, which was used for vertical burning test (UL-94).

[0085] Comparative Example 1

[0086] This example provides a method for preparing a flame-retardant acrylic coating, including the following steps (by mass): 40 parts of acrylic emulsion and 5.5 parts of ammonium polyphosphate are added to a beaker, and the mixture is stirred at 200 rpm for 1 h at room temperature to disperse it evenly and obtain the flame-retardant acrylic coating.

[0087] The flame-retardant acrylic coating of Comparative Example 1 was applied to polypropylene by scraping and dried at 20°C for 18 h. The coating thickness after drying was 500 μm, which was used for light transmittance, UL-94 and LOI tests.

[0088] Comparative Example 2

[0089] The flame-retardant acrylic coating of Comparative Example 1 was applied to polypropylene by scraping and dried at 20°C for 18 h. The coating thickness after drying was 200 μm, which was used for light transmittance and UL-94 testing.

[0090] Performance testing: The products obtained in Examples 1-6 and the products obtained in Comparative Examples 1-2 were subjected to the following tests.

[0091] The UL-94 rating of the polypropylene composite material with flame-retardant coating was tested using a plastic horizontal / vertical burning tester, according to GB / T 2408-2008. The limiting oxygen index of the polypropylene composite material with flame-retardant coating was tested using a ZR-01 intelligent oxygen index meter, according to GB / T 38301-2019. The transmittance of the flame-retardant coating was tested using a Cary 100 UV-Vis spectrophotometer. The flame-retardant performance test results and transmittance of Examples 1-5 and the comparative example are shown in Table 1. In Table 1, the coating of the comparative example is a milky white opaque coating. When the coating thickness is 200 μm, the UL-94 test result is NR, which cannot meet the flame-retardant requirements. Only when the coating thickness is greater than or equal to 500 μm can it pass the UL-94 V-0 rating. However, the flame-retardant coatings of Examples 1-5 can pass the UL-94 V-0 rating even when the thickness is only 200 μm. More notably, the limiting oxygen index (LOI) of the flame-retardant polypropylene coated with the coating of this invention all exceeded 40%, with the LIOI of the flame-retardant polypropylene in Example 3 reaching as high as 46.1%, a value far exceeding the 18.0% LIOI of polypropylene. This indicates that the flame-retardant coating of this invention not only has high light transmittance (the light transmittance of Example 3 is as shown in the figure), but also... Figure 3Furthermore, it can impart excellent flame retardancy to polypropylene even with a very thin coating. In Example 3, during a constant-temperature muffle furnace experiment at 550°C, the coating expanded to approximately 100 times its original volume, and the char layer was dense and continuous, demonstrating the significant condensed-phase flame retardant effect of the flame retardant coating of this invention.

[0092] Table 1 Flame retardant performance test results and light transmittance

[0093]

[0094] The flame retardant properties of polypropylene composites with flame-retardant coatings were tested using a cone calorimeter according to ISO 5660-1. The cone calorimeter test results for Examples 1 and 2 are shown in Table 2 and... Figure 1 From Table 2 and Figure 1 The peak heat release rate (PHRR) and total heat release rate (THR) of polypropylene are 823.5 kW / m³. 2 and 114.4 MJ / m 2 In Example 1, the PHRR and THR values ​​of the flame-retardant polypropylene were 298.9 kW / m³. 2 and 76.4 MJ / m 2 The heat release was significantly reduced by 63.7% and 33.2%, respectively, indicating that the flame-retardant coating of the present invention has a stronger ability to reduce heat release. The ignition time (TTI) of polypropylene was only 34 s, while the TTI of Example 1 was increased to 525 s. The char residue of polypropylene was 7%, while the char residue of the flame-retardant polypropylene in Example 1 was 15.89%, indicating the formation of high char residue. Meanwhile, the fire spread rate was estimated by detecting the fire growth rate index (FIGRA) and fire performance index (FPI). The FIGRA of polypropylene was 5.00 kW / m³. 2 s, FPI is 0.04 m 2 The figure for flame-retardant polypropylene in Example 1 is 0.42 kW / (m²), while the figure for flame-retardant polypropylene in Example 1 is 0.42 kW / (m²). 2 / s), FPI is 1.76 m 2 The efficiency was ·s / kW, which is 3.2 times higher than that of PP. The total smoke production (TSP) was also evaluated. The TSP of the flame-retardant polypropylene in Example 1 was 7.98 m³ / kW. 2 The content of each component is reduced by 40.5% compared to polypropylene. The results of cone calorimetry further demonstrate that the flame-retardant coating of this invention has excellent flame retardancy.

[0095] Table 2. Cone Calorimetry Results

[0096]

[0097] The back temperature of steel plates and polypropylene plates with flame-retardant coatings was tested using a handheld thermal imager. The back temperature test results for Examples 1-5 are shown in Table 3, and the back temperature test results for Example 3 are shown in Table 4. Figure 2 As shown in Table 3, the stable back temperature of the fireproof steel plate of the present invention is below 250℃ within 30 minutes, indicating that the flame-retardant coating of the present invention can reduce the back temperature of the steel plate and improve the stability of the steel structure at high temperatures when used for fireproofing. In addition, the back temperature of the flame-retardant polypropylene in Examples 1-5 was also tested, and the temperature was stable at around 220℃, further demonstrating that the flame-retardant coating of the present invention has good heat insulation and fireproof performance.

[0098] Table 3 Back temperature test results

[0099]

[0100] According to GB / T 4893.4-2013, the adhesion of flame-retardant coatings was tested. A cross-cut tester (OU4000) was used to make five horizontal and five vertical cuts on the composite film, forming 16 small squares of 1cm × 1cm. 3M cross-cut test tape was then used to firmly adhere the coating, and the damage was quickly removed to determine its hardness level. According to GB / T 6739-1996, the hardness of the coating was tested using a coating pencil hardness tester (QHQ-A). The sample was placed horizontally on the test bench, and the installed pencil hardness tester was gently placed on the coating surface at a 45° angle. Starting with the hardest pencil, the tester was pushed horizontally for 10 cm at a speed of 5–10 cm / min, observing for scratches. Each pencil level was tested five times. If the sample was scratched in two out of five attempts, a softer pencil was selected. This process continued until a pencil that could scratch the sample in at most one out of five attempts was found. This pencil number represents the pencil hardness of the sample. The results of the cross-cut adhesion test and hardness test of the coatings in Examples 1-5 are shown in Table 4. In Table 4, the flame-retardant coatings obtained in Examples 1-5 were subjected to a cross-cut adhesion test on the pretreated polypropylene substrate, and all achieved a 5B rating. The hardness test reached 3H, indicating that the coating of the present invention can firmly adhere to the polypropylene surface, and the hardness of the coating meets the requirements of the paint film hardness.

[0101] Table 4 Results of Cross-cut Cord Test and Hardness Test for Coating

[0102]

[0103] According to GB / T5210-2006, pull-out adhesion tests were conducted on various coatings: A CMT4204 universal testing machine was used to measure the adhesion between different coatings and polypropylene via a pull-out test at a stretching rate of 5 mm / min. The adhesion measured by the pull-out test refers to the force required to break the adhesion between the coating and the substrate when a uniform and perpendicular force is applied above the adhesive surface at a specified speed. The adhesion test results of the flame-retardant coating prepared in Example 3, the acrylic emulsion (commercially available, purchased from Luyuan Chemical), and the flame-retardant acrylic coating prepared in Comparative Example 2 with the flame-burned polypropylene are as follows: Figure 4 . Figure 4 The results show that, compared to acrylic emulsion coatings and flame-retardant acrylic coatings, the flame-retardant coating of the present invention achieves an adhesion strength of 1.7 MPa on polypropylene, which is stronger than that of acrylic emulsion coatings and flame-retardant acrylic coatings. This demonstrates that the coating of the present invention has a much stronger adhesion than ordinary coatings.

[0104] The results of the vertical burning test (UL-94) of different materials in Example 6 are shown in Table 5. As can be seen from Table 5, the flame-retardant coating of the present invention can pass the UL-94 V-0 rating when applied to different substrate surfaces, indicating that the coating of the present invention has wide applicability.

[0105] Table 5 UL-94 Tests of Different Matrix Materials in Example 6

[0106]

[0107] The antibacterial properties of the flame-retardant coating were tested using a solid agar plate assay. Experimental procedure: *E. coli* DH5α was cultured in LB medium at 220 rpm and 37°C until the OD600 reached approximately 0.6, a concentration of 10⁸ CFU / mL. The bacterial culture was mixed with melted solid medium at a volume ratio of 1:1000. 10 mL of the mixed medium was poured into each 90 mm diameter petri dish and allowed to solidify. The test samples were then added, and the mixture was incubated at 37°C for 24 hours before photographing. The antibacterial test results of the flame-retardant coating in Example 4 are shown in Table 6. As shown in Table 6, the number of colonies on the blank plate was significantly higher than that on the plate treated with the flame-retardant coating in Example 4, with antibacterial rates exceeding 80%, indicating that the flame-retardant coating of this invention possesses antibacterial properties.

[0108] Table 6 Antibacterial Test of Flame Retardant Coating in Example 4

[0109]

[0110] The flame-retardant coating of the present invention was used as an adhesive and its performance was tested: The flame-retardant coating prepared in Example 3 (with a coating thickness of approximately 200 μm) was uniformly applied to both ends of a polyurethane foam. After being left at room temperature for 6 hours, the partially dried coating surfaces were bonded together. After being left at room temperature for 12 hours, the bonded polyurethane foam was obtained. The bonded polyurethane foam could withstand a force of at least 5 N on its vertical surface, indicating that the flame-retardant coating of the present invention, when used as an adhesive for polyurethane foam, can withstand a certain weight of pulling force without separating the substrate, thus meeting the requirements for use as an adhesive.

Claims

1. A bio-based intumescent waterborne flame-retardant coating with strong adhesion properties, characterized in that... Made from the following parts by weight of raw materials: 100-300 parts deionized water 10-40 parts of gluconate 10-30 parts chitosan salt 40-45 parts phytic acid 1-2 parts of anti-aging agent 0.3-0.4 parts of antifreeze-thaw aid.

2. The bio-based intumescent waterborne flame-retardant coating with strong adhesion properties according to claim 1, characterized in that: The gluconate includes one of calcium gluconate, sodium gluconate, magnesium gluconate, or a combination thereof.

3. The bio-based intumescent waterborne flame-retardant coating with strong adhesion properties according to claim 1, characterized in that: The chitosan salts include one or a combination of chitosan quaternary ammonium salt, chitosan hydrochloride, chitosan lactate, and chitosan nitrate, with a degree of substitution ≥80%.

4. The bio-based intumescent waterborne flame-retardant coating with strong adhesion properties according to claim 1, characterized in that: The phytic acid is a 50-70 wt.% phytic acid solution.

5. The bio-based intumescent waterborne flame-retardant coating with strong adhesion properties according to claim 1, characterized in that: The anti-aging agent is any one of UV-770, UV-531, and anti-aging agent 1010; the anti-freeze-thaw aid is Clariant's environmentally friendly, washable, and anti-freeze-thaw aid Genapol 2070.

6. A method for preparing a bio-based intumescent waterborne flame-retardant coating with strong adhesion properties as described in any one of claims 1 to 5, characterized in that... Includes the following steps: (1) Add deionized water and gluconate to a beaker and stir in a water bath at 50-80℃ until completely dissolved; (2) After the solution is cooled to room temperature, chitosan salt is slowly added and stirred at 100-200 rpm for 1-1.5 h at room temperature to disperse it evenly; (3) Slowly add phytic acid solution and stir at 100-200 rpm for 30-60 min at room temperature; (4) Add anti-aging agent and anti-freeze-thaw agent, and stir at 100 rpm for 20 min; after mixing evenly, a bio-based intumescent water-based flame retardant coating with strong adhesion is obtained.

7. A method of using the bio-based intumescent waterborne flame-retardant coating with strong adhesion properties as described in any one of claims 1 to 5, characterized in that: The coating method on the substrate surface is: scraping, brushing, dipping or rolling; the coating is dried at 15~35℃ for 18~24 h, and multiple coatings are required when the coating thickness exceeds 200 μm after drying.

8. The method of use according to claim 7, characterized in that: The substrate includes plastic, wood, wallpaper, rigid polyurethane foam, or steel. When the substrate is plastic or a substrate with low surface polarity, a simple pretreatment of the substrate surface is required, including one of the following methods: flame burning, sanding, and adhesion treatment agent treatment.

9. The application of a bio-based intumescent waterborne flame-retardant coating with strong adhesion as described in any one of claims 1 to 5 in the fireproofing of steel plates, characterized in that: When flame-retardant coatings are applied to steel plates for fire prevention, an acrylic emulsion, silicone resin, or wood wax oil should be pre-coated on the surface of the steel plate as a primer with a thickness of 50-150 μm. After the primer dries, the flame-retardant coating of the present invention is applied as a topcoat on the steel plate surface coated with the primer. The flame-retardant coating thickness is ≥1500 μm and is applied in 4-6 coats.

10. The application of a bio-based intumescent waterborne flame-retardant coating with strong adhesion properties as described in any one of claims 1 to 5 in a flame-retardant adhesive.

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