Halogen-free composite flame retardant based on MOFs carrier, low-VOC halogen-free flame-retardant pressure-sensitive adhesive, adhesive tape and preparation method

Abstract

The invention discloses a halogen-free composite flame retardant based on an MOFs carrier, a low-VOC halogen-free flame-retardant pressure-sensitive adhesive, an adhesive tape and a preparation method, and the halogen-free composite flame retardant is prepared by the following steps: mixing an MOFs metal source, an organic ligand and ammonium polyphosphate in a reaction kettle, reacting at 100-140 DEG C for 12-48 hours, and centrifuging, washing and drying after the reaction is finished to obtain the halogen-free composite flame retardant. The MOFs base is used as a flame retardant carrier, so that the adsorption of volatile substances can be effectively improved; after the MOFs and the APP are matched, a phosphate group of the APP is coordinated with the Zr6 cluster to become a part of the MOFs structure, so that the hydrophilic capacity of the surface of the MOFs is improved, the dispersion of the MOFs-based APP in the glue is enhanced, and the influence of the MOFs-based APP on the mechanical property is reduced.

Description

halogen-free composite flame retardants, low-VOC halogen-free flame-retardant pressure-sensitive adhesives and tapes based on MOFs carriers, and their preparation methods. Technical Field

[0001] This invention relates to the field of flame-retardant adhesive materials, and particularly to a halogen-free composite flame retardant based on MOFs carrier, a low-VOC halogen-free flame-retardant pressure-sensitive adhesive, an adhesive tape, and a preparation method thereof. Background Technology

[0002] Traditional flame-retardant tapes often use halogenated flame retardants (such as bromine-based and chlorine-based ones), which release toxic hydrogen halide gases and dioxins when burning, failing to meet environmental protection requirements (such as RoHS and REACH). While halogen-free flame-retardant tapes are environmentally friendly, the large amounts of halogenated agents added lead to decreased mechanical properties, processing difficulties, and relatively low flame-retardant efficiency. Furthermore, the tapes release VOCs (such as residual solvents, plasticizers, and small molecule monomers) during production and use, harming human health (e.g., carcinogenic and teratogenic) and causing environmental pollution.

[0003] With the development of new energy vehicles, the requirements for flame retardancy and VOCs are becoming increasingly stringent. Current technologies lack effective solutions that simultaneously address both flame retardancy and ultra-low VOCs. MOFs, due to their ultra-high specific surface area and designable pore structure, have been used in gas adsorption and catalysis, but their application in adhesives is limited. In existing technologies, MOFs are mostly used as single fillers to enhance mechanical properties or adsorb specific gases such as formaldehyde; there are no reports of MOFs being used as flame retardant carriers to synergistically achieve both flame retardancy and VOC adsorption in adhesive tapes. Summary of the Invention

[0004] The technical problem to be solved by this invention is to address the shortcomings of the prior art by providing a halogen-free composite flame retardant based on MOFs carriers, a low-VOC halogen-free flame-retardant pressure-sensitive adhesive, tape, and its preparation method. This invention utilizes metal-organic framework materials (MOFs) as a flame retardant carrier and a volatile organic compound (VOC) adsorbent to achieve the preparation of a low-VOC release, highly efficient halogen-free flame-retardant pressure-sensitive adhesive tape. This tape is particularly suitable for fields with high environmental protection and fire safety requirements, such as new energy vehicles and electronic appliances.

[0005] To achieve the above objectives, the technical solution adopted by the present invention is as follows: In the first aspect of the present invention, a halogen-free composite flame retardant based on MOFs carrier is provided, which is prepared by the following method: MOFs metal source, organic ligand and ammonium polyphosphate are mixed in a reaction vessel and reacted at 100-140℃ for 12-48h. After the reaction is completed, the mixture is centrifuged, washed and dried to obtain the halogen-free composite flame retardant.

[0006] Preferably, the metal source of the MOFs is zirconium nitrate hexahydrate, and the organic ligand is 2-aminoterephthalic acid.

[0007] Preferably, the molar ratio of MOF metal source: organic ligand: ammonium polyphosphate is (0.5-2):(0.5-2):(0.15-0.6).

[0008] Preferably, the molar ratio of MOF metal source: organic ligand: ammonium polyphosphate is 1:1:0.3, or 1:1:0.4, or 1:1:0.5. Preferably, the halogen-free composite flame retardant based on the MOF support is prepared by the following method: MOF metal source, organic ligand, and ammonium polyphosphate are mixed in a reaction vessel and reacted at 100-140℃ for 12-48 h. After the reaction, the mixture is centrifuged, the precipitate is washed with DMF, then added to methanol and stirred for 12-48 h. After centrifugation, the precipitate is collected and vacuum dried at 100-140℃ for 15-60 min to obtain the halogen-free composite flame retardant.

[0009] In a second aspect, the present invention provides a low-VOC halogen-free flame-retardant pressure-sensitive adhesive comprising the following raw material components by weight: 100 parts acrylic adhesive, 10-20 parts tackifying resin, 20-50 parts diluent, 0.5-1.2 parts curing agent, and 30-70 parts of the halogen-free composite flame retardant as described above.

[0010] Preferably, the tackifying resin is a mixture of esterified rosin and terpene phenol resin in a mass ratio of 1:(1-8).

[0011] Preferably, the curing agent is an isocyanate-based curing agent.

[0012] Preferably, the diluent is any one or a combination of toluene, acetone and ethyl acetate.

[0013] In a third aspect, the present invention provides a low-VOC halogen-free flame-retardant pressure-sensitive adhesive tape, which is prepared by the following method: uniformly coating the low-VOC halogen-free flame-retardant pressure-sensitive adhesive as described above onto release paper, baking, curing to form an adhesive layer, and bonding the adhesive layer to both sides of cotton paper to obtain the low-VOC halogen-free flame-retardant pressure-sensitive adhesive tape.

[0014] The beneficial effects of this invention are: This invention provides a halogen-free composite flame retardant based on MOFs carriers, as well as a low-VOC halogen-free flame retardant pressure-sensitive adhesive and tape based on the flame retardant. This invention can meet the bonding requirements of low VOC and flame retardant performance, and can efficiently meet the growing demand for health and environmental protection, ultimately achieving the ultimate balance between safety and environmental protection, and has broad market application prospects.

[0015] In this invention, MOFs are used as flame retardant carriers, which can effectively increase the adsorption of volatile substances. When MOFs are combined with APP, the phosphate groups of APP coordinate with the Zr6 cluster and become part of the MOFs structure. This improves the hydrophilicity of the MOFs surface, strengthens the dispersion of MOFs-APP in the adhesive, and reduces its impact on mechanical properties.

[0016] This invention prepares a flame retardant with high adsorption capacity by combining MOFs and flame retardants, combining their synergistic flame retardant effects with the high adsorption physical properties of MOFs themselves, and achieving the effects of low VOC release and high efficiency halogen-free flame retardancy. Attached Figure Description

[0017] Figure 1 is a scanning electron microscope (SEM) image of APP; Figure 2 is a scanning electron microscope (SEM) image of the halogen-free composite flame retardant prepared in Example 1. Detailed Implementation

[0018] The present invention will be further described in detail below with reference to embodiments, so that those skilled in the art can implement it based on the description.

[0019] It should be understood that terms such as “having,” “comprising,” and “including” as used herein do not exclude the presence or addition of one or more other elements or combinations thereof.

[0020] Unless otherwise specified, the experimental methods used in the following examples are conventional methods. Unless otherwise specified, the materials and reagents used in the following examples are commercially available. For examples where specific conditions are not specified, conventional conditions or conditions recommended by the manufacturer are followed. For reagents or instruments whose manufacturers are not specified, they are all commercially available products.

[0021] In a first aspect, this invention provides a halogen-free composite flame retardant based on MOFs (Metal-Organic Facility) supports, which is prepared by the following method: MOFs metal source, organic ligand, and ammonium polyphosphate are mixed in a reaction vessel and reacted at 100-140°C for 12-48 hours. After the reaction, the mixture is centrifuged, washed, and dried to obtain the halogen-free composite flame retardant. This flame retardant has adsorption properties, enabling it to adsorb VOCs during the use of adhesive tape, thereby reducing the harmful effects of VOCs on the environment.

[0022] In a preferred embodiment, the metal source of the MOFs is zirconium nitrate hexahydrate, and the organic ligand is 2-aminoterephthalic acid.

[0023] In a preferred embodiment, the molar ratio of MOF metal source: organic ligand: ammonium polyphosphate is (0.5-2):(0.5-2):(0.15-0.6).

[0024] In a preferred embodiment, the molar ratio of MOF metal source: organic ligand: ammonium polyphosphate is 1:1:0.3, or 1:1:0.4, or 1:1:0.5. In a preferred embodiment, the halogen-free composite flame retardant based on MOF support is prepared by the following method: MOF metal source, organic ligand, and ammonium polyphosphate are mixed in a reaction vessel and reacted at 100-140℃ for 12-48h. After the reaction is completed, the mixture is centrifuged, the precipitate is washed with DMF, and then added to methanol and stirred for 12-48h. After centrifugation, the precipitate is collected and vacuum dried at 100-140℃ for 15-60min to obtain the halogen-free composite flame retardant.

[0025] In a second aspect, the present invention provides a low-VOC halogen-free flame-retardant pressure-sensitive adhesive comprising the following raw material components by weight: 100 parts acrylic adhesive, 10-20 parts tackifying resin, 20-50 parts diluent, 0.5-1.2 parts curing agent, and 30-70 parts of the above-mentioned halogen-free composite flame retardant.

[0026] In a preferred embodiment, the tackifying resin is a mixture of esterified rosin and terpene phenol resin in a mass ratio of 1:(1-8). The softening point of the esterified rosin is 90-130°C, and the softening point of the terpene phenol resin is 130-160°C.

[0027] In a preferred embodiment, the curing agent is an isocyanate-based curing agent.

[0028] In a preferred embodiment, the diluent is any one or a combination of toluene, acetone and ethyl acetate.

[0029] In a first aspect, the present invention provides a low-VOC halogen-free flame-retardant pressure-sensitive adhesive tape, which is prepared by the following method: the low-VOC halogen-free flame-retardant pressure-sensitive adhesive is uniformly coated on release paper, baked, and cured to form an adhesive layer, and the adhesive layer is adhered to both sides of cotton paper to obtain the low-VOC halogen-free flame-retardant pressure-sensitive adhesive tape.

[0030] In a preferred embodiment, an adhesive layer with a thickness of 40-50 μm is coated on both sides of the cotton paper.

[0031] In a preferred embodiment, the release force of the release paper is 7-20 gf / in at room temperature for 24 hours and 10-30 gf / in after aging at 70°C for 20 hours.

[0032] In a preferred embodiment, the cotton paper is 14g cotton paper.

[0033] In a preferred embodiment, the baking process is carried out using a 7-section oven, wherein the oven temperatures are set as follows: 60-80℃, 80-100℃, 100-120℃, 120-140℃, 120-140℃, 120-140℃, 90-110℃, the coating speed is 10-50m / min, and the baking time is 33-168s.

[0034] The development of new energy vehicles has placed more functional demands on adhesive tapes and similar bonding components. Adhesive tapes face greater challenges in terms of VOC and fire safety, requiring the abandonment of traditional halogenated flame retardants and non-environmentally friendly materials, and the adoption of new halogen-free flame retardants and low VOCs, while retaining high adhesion and high weather resistance.

[0035] The low-VOC halogen-free flame-retardant pressure-sensitive tape of the present invention has low VOC, high adhesion, no adhesive residue after peeling, good temperature resistance and good flame retardant properties, and can be widely used in automotive interiors, new energy power battery packs and other scenarios that require both low VOC and flame retardancy.

[0036] The above is the general concept of the present invention. Based on this, detailed embodiments and comparative examples are provided below to further illustrate the present invention.

[0037] The main raw materials in the following examples and comparative examples are described below: Zirconium nitrate hexahydrate: Zr(NO3)4·6H2O, produced by Shandong Desheng New Material Co., Ltd.; 2-aminoterephthalic acid (NH2-BDC), produced by Suzhou Kaifa New Material Technology Co., Ltd.; APP (ammonium polyphosphate), produced by Shandong Kemike New Material Co., Ltd.; DMF, produced by Shandong Haofa Chemical Co., Ltd.; methanol, produced by Shandong Longyu Chemical Co., Ltd.; acrylic adhesive, PS-8280 provided by Kunshan Shimei Fine Chemical Co., Ltd.; isocyanate curing agent, specifically L-75 from Youmai Chemical (Shanghai) Co., Ltd. or L-75 from Shanghai Deyin Chemical Co., Ltd.; tackifying resin is a mixture of esterified rosin and terpene phenol resin in a mass ratio of 1:4.

[0038] Example 1: A halogen-free composite flame retardant based on MOFs carrier was prepared by the following method: Zr(NO3)4·6H2O:NH2-BDC:APP (ammonium polyphosphate) were mixed in a molar ratio of 1:1:0.3 and reacted in a hydrothermal reactor at 120°C for 24 hours; the mixture in the reactor was transferred to a polytetrafluoroethylene centrifuge tube and centrifuged at 10,000 rpm for 10 minutes to separate the lower precipitate (MOFs complex); the precipitate was washed with DMF three times and then magnetically stirred with anhydrous methanol for 24 hours, and the lower precipitate was collected by centrifugation again; the precipitate was dried in a vacuum drying oven at 120°C for 30 minutes to obtain the halogen-free composite flame retardant.

[0039] Figure 1 and Figure 2 are scanning electron microscope images of APP and the halogen-free composite flame retardant prepared in this example, respectively. The APP shown in Figure 1 has different sizes, irregular shapes and smooth surfaces. In Figure 2, due to the encapsulation and coverage of Zr-MOFs, the surface of APP becomes extremely rough, which also shows that APP and Zr-MOFs have been successfully compounded.

[0040] A low-VOC halogen-free flame-retardant pressure-sensitive adhesive tape is prepared by the following method: S1. According to the mass parts, 100 parts of acrylic adhesive, 15 parts of tackifying resin, 50 parts of diluent, 0.9 parts of isocyanate curing agent, and 50 parts of halogen-free composite flame retardant are mixed evenly to obtain flame-retardant pressure-sensitive adhesive.

[0041] S2. Using a comma-shaped scraper, a layer of flame-retardant pressure-sensitive adhesive is coated onto the release paper. After baking in a multi-section oven, a 45μm thick adhesive layer is formed. The multi-section oven consists of 7 sections, with the oven temperatures set as follows: 70℃, 90℃, 110℃, 125℃, 125℃, 125℃, 110℃. The coating speed is 25m / min, and the baking time is 67s. The two adhesive layers are then bonded to both sides of 14g cotton paper to obtain the finished product.

[0042] Example 2: A halogen-free composite flame retardant based on MOFs carrier was prepared by the following method: Zr(NO3)4·6H2O:NH2-BDC:APP (ammonium polyphosphate) were mixed in a molar ratio of 1:1:0.4 and reacted in a hydrothermal reactor at 120°C for 24 hours; the mixture in the reactor was transferred to a polytetrafluoroethylene centrifuge tube and centrifuged at 10,000 rpm for 10 minutes to separate the lower precipitate (MOFs complex); the precipitate was washed with DMF three times and then magnetically stirred with anhydrous methanol for 24 hours, and the lower precipitate was collected by centrifugation again; the precipitate was dried in a vacuum drying oven at 120°C for 30 minutes to obtain the halogen-free composite flame retardant.

[0043] A low-VOC halogen-free flame-retardant pressure-sensitive adhesive tape is prepared by the following method: S1. According to the mass parts, 100 parts of acrylic adhesive, 15 parts of tackifying resin, 50 parts of diluent, 0.9 parts of isocyanate curing agent, and 50 parts of halogen-free composite flame retardant are mixed evenly to obtain flame-retardant pressure-sensitive adhesive.

[0044] S2. Using a comma-shaped scraper, a layer of flame-retardant pressure-sensitive adhesive is coated onto the release paper. After baking in a multi-section oven, a 45μm thick adhesive layer is formed. The multi-section oven consists of 7 sections, with the oven temperatures set as follows: 70℃, 90℃, 110℃, 125℃, 125℃, 125℃, 110℃. The coating speed is 25m / min, and the baking time is 67s. The two adhesive layers are then bonded to both sides of 14g cotton paper to obtain the finished product.

[0045] Example 3: A halogen-free composite flame retardant based on MOFs carrier was prepared by the following method: Zr(NO3)4·6H2O:NH2-BDC:APP (ammonium polyphosphate) were mixed in a molar ratio of 1:1:0.5 and reacted in a hydrothermal reactor at 120°C for 24 hours; the mixture in the reactor was transferred to a polytetrafluoroethylene centrifuge tube and centrifuged at 10,000 rpm for 10 minutes to separate the lower precipitate (MOFs complex); the precipitate was washed with DMF three times and then magnetically stirred with anhydrous methanol for 24 hours, and the lower precipitate was collected by centrifugation again; the precipitate was dried in a vacuum drying oven at 120°C for 30 minutes to obtain the halogen-free composite flame retardant.

[0046] A low-VOC halogen-free flame-retardant pressure-sensitive adhesive tape is prepared by the following method: S1. According to the mass parts, 100 parts of acrylic adhesive, 15 parts of tackifying resin, 50 parts of diluent, 0.9 parts of isocyanate curing agent, and 50 parts of halogen-free composite flame retardant are mixed evenly to obtain flame-retardant pressure-sensitive adhesive.

[0047] S2. Using a comma-shaped scraper, a layer of flame-retardant pressure-sensitive adhesive is coated onto the release paper. After baking in a multi-section oven, a 45μm thick adhesive layer is formed. The multi-section oven consists of 7 sections, with the oven temperatures set as follows: 70℃, 90℃, 110℃, 125℃, 125℃, 125℃, 110℃, coating speed of 25m / min, and baking time of 67s. The two adhesive layers are then bonded to both sides of 14g cotton paper to obtain the finished product.

[0048] Comparative Example 1: A pressure-sensitive adhesive tape is prepared by the following method: S1. According to the mass parts, 100 parts of acrylic adhesive, 15 parts of tackifying resin, 50 parts of diluent, 0.9 parts of isocyanate curing agent, and 50 parts of zirconium nitrate hexahydrate are mixed evenly to obtain a pressure-sensitive adhesive.

[0049] S2. Using a comma-shaped scraper, a layer of pressure-sensitive adhesive is coated onto the release paper. After baking in a multi-section oven, a 45μm thick adhesive layer is formed. The multi-section oven consists of 7 sections, with the oven temperatures set as follows: 70℃, 90℃, 110℃, 125℃, 125℃, 125℃, 110℃. The coating speed is 25m / min, and the baking time is 67s. The two adhesive layers are then bonded to both sides of 14g cotton paper to obtain the finished product.

[0050] Comparative Example 2: A pressure-sensitive adhesive tape was prepared by the following method: S1. 100 parts by weight of acrylic adhesive, 15 parts by weight of tackifying resin, 50 parts by weight of diluent, 0.9 parts by weight of isocyanate curing agent, and 50 parts by weight of APP were mixed evenly to obtain a pressure-sensitive adhesive.

[0051] S2. Using a comma-shaped scraper, a layer of pressure-sensitive adhesive is coated onto the release paper. After baking in a multi-section oven, a 45μm thick adhesive layer is formed. The multi-section oven consists of 7 sections, with the oven temperatures set as follows: 70℃, 90℃, 110℃, 125℃, 125℃, 125℃, 110℃. The coating speed is 25m / min, and the baking time is 67s. The two adhesive layers are then bonded to both sides of 14g cotton paper to obtain the finished product.

[0052] Comparative Example 3: A halogen-free composite flame retardant based on MOFs was prepared by the following method: Zr(NO3)4·6H2O:NH2-BDC:APP = 1:1:0.2 were mixed in a hydrothermal reactor at 120°C for 24 hours; the mixture in the reactor was transferred to a polytetrafluoroethylene centrifuge tube and centrifuged at 10,000 rpm for 10 minutes to separate the lower precipitate (MOFs composite); the precipitate was washed with DMF three times and then magnetically stirred with anhydrous methanol for 24 hours, followed by centrifugation to collect the lower precipitate; the precipitate was dried in a vacuum drying oven at 120°C for 30 minutes to obtain the halogen-free composite flame retardant.

[0053] A low-VOC halogen-free flame-retardant pressure-sensitive adhesive tape is prepared by the following method: S1. According to the mass parts, 100 parts of acrylic adhesive, 15 parts of tackifying resin, 50 parts of diluent, 0.9 parts of isocyanate curing agent, and 50 parts of halogen-free composite flame retardant are mixed evenly to obtain flame-retardant pressure-sensitive adhesive.

[0054] S2. Using a comma-shaped scraper, a layer of flame-retardant pressure-sensitive adhesive is coated onto the release paper. After baking in a multi-section oven, a 45μm thick adhesive layer is formed. The multi-section oven consists of 7 sections, with the oven temperatures set as follows: 70℃, 90℃, 110℃, 125℃, 125℃, 125℃, 110℃, coating speed of 25m / min, and baking time of 67s. The two adhesive layers are then bonded to both sides of 14g cotton paper to obtain the finished product.

[0055] The performance tests were performed on the pressure-sensitive tape prepared in the example as follows: (1) The 180° peel force performance test was performed in accordance with the GB / T 2792-2014 standard for peel force test of pressure-sensitive tape.

[0056] (2) The holding force performance was tested in accordance with GB / T 4851-2014 pressure-sensitive tape holding force test standard.

[0057] (3) VOC testing was conducted in accordance with VDA 278 standard for testing volatile organic compounds and atomization of automotive non-metallic materials.

[0058] (4) A flammability test shall be conducted in accordance with the UL-94 safety standard for flammability of plastic materials used in equipment and appliance components.

[0059] (5) The odor test results were conducted in accordance with the MS-300 odor test standard and are shown in Table 1 below: Table 1 The test results show that using MOFs as a flame retardant carrier can effectively increase the adsorption of volatile substances. In Comparative Example 1, the direct addition of MOFs-based metal source (zirconium nitrate hexahydrate) resulted in a large amount of agglomeration due to the hydrophilicity of its groups, leading to a significant decrease in the mechanical properties of the tape. However, in Examples 1-3, when MOFs were combined with APP, the phosphate groups of APP coordinated with the Zr6 clusters, becoming part of the MOFs structure. This improved the hydrophilicity of the MOFs surface, enhanced the dispersion of MOFs-APP in the adhesive, and reduced its impact on mechanical properties.

[0060] In Comparative Example 2, although the amount of flame retardant APP added was higher than that in Examples 1-3, the metal oxide (ZrO2) generated by the pyrolysis of MOFs in Examples 1-3 catalyzed the dehydration of the polymer matrix into carbon, which synergistically promoted the formation of the expanded carbon layer with APP. In addition, its efficient adsorption capacity adsorbed the cracked free radicals and combustible gases, reducing the release of combustibles and providing a strong guarantee for flame retardancy. Ultimately, the flame retardant performance of Examples 1-3 was stronger than that of Comparative Example 2.

[0061] In Comparative Example 3, the proportion of APP in the halogen-free composite flame retardant decreased. Although VOC decreased, the flame retardant performance also decreased to some extent.

[0062] Although the embodiments of the present invention have been disclosed above, they are not limited to the applications listed in the specification and embodiments. They can be applied to various fields suitable for the present invention. For those skilled in the art, other modifications can be easily made. Therefore, without departing from the general concept defined by the claims and their equivalents, the present invention is not limited to the specific details.

Claims

1. A halogen-free composite flame retardant based on MOFs carrier, characterized in that, It is prepared by the following method: MOF metal source, organic ligand and ammonium polyphosphate are mixed in a reaction vessel and reacted at 100-140℃ for 12-48h. After the reaction is completed, the mixture is centrifuged, washed and dried to obtain the halogen-free composite flame retardant.

2. The halogen-free composite flame retardant based on MOFs carrier according to claim 1, characterized in that, The metal source of the MOFs is zirconium nitrate hexahydrate, and the organic ligand is 2-aminoterephthalic acid.

3. The halogen-free composite flame retardant based on MOFs carrier according to claim 2, characterized in that, The molar ratio of MOF metal source: organic ligand: ammonium polyphosphate is (0.5-2):(0.5-2):(0.15-0.6).

4. The halogen-free composite flame retardant based on MOFs carrier according to claim 3, characterized in that, The molar ratio of MOF metal source: organic ligand: ammonium polyphosphate is 1:1:0.3, or 1:1:0.4, or 1:1:0.

5.

5. The halogen-free composite flame retardant based on MOFs carrier according to claim 1, characterized in that, It is prepared by the following method: MOF metal source, organic ligand and ammonium polyphosphate are mixed in a reaction vessel and reacted at 100-140℃ for 12-48h. After the reaction is completed, the mixture is centrifuged, the precipitate is washed with DMF, and then added to methanol and stirred for 12-48h. After centrifugation, the precipitate is collected and vacuum dried at 100-140℃ for 15-60min to obtain the halogen-free composite flame retardant.

6. A low-VOC, halogen-free, flame-retardant pressure-sensitive adhesive, characterized in that, It comprises the following raw material components by weight: 100 parts acrylic adhesive, 10-20 parts tackifying resin, 20-50 parts diluent, 0.5-1.2 parts curing agent, and 30-70 parts halogen-free composite flame retardant as described in any one of claims 1-4.

7. The low-VOC halogen-free flame-retardant pressure-sensitive adhesive according to claim 6, characterized in that, The tackifying resin is a mixture of esterified rosin and terpene phenol resin in a mass ratio of 1:(1-8).

8. The low-VOC halogen-free flame-retardant pressure-sensitive adhesive according to claim 6, characterized in that, The curing agent is an isocyanate-based curing agent.

9. The low-VOC halogen-free flame-retardant pressure-sensitive adhesive according to claim 6, characterized in that, The diluent is any one or a combination of toluene, acetone and ethyl acetate.

10. A low-VOC, halogen-free, flame-retardant pressure-sensitive adhesive tape, characterized in that, It is prepared by the following method: the low VOC halogen-free flame-retardant pressure-sensitive adhesive described in any one of claims 6-9 is uniformly coated on release paper, baked, and cured to form an adhesive layer, and the adhesive layer is adhered to both sides of the cotton paper to obtain the low VOC halogen-free flame-retardant pressure-sensitive tape.

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