Halogen-free flame-retardant modified two-component polyurethane adhesive and preparation method thereof

Abstract

This application relates to the field of polyurethane materials technology, and more specifically, to a halogen-free flame-retardant modified two-component polyurethane adhesive and its preparation method. The adhesive comprises a curing agent component A and a main agent component B. Component A includes a flame-retardant polyurethane prepolymer, isocyanate monomers, and auxiliary agents. Component B includes hydroxyl polyphosphate ester, polyether polyol, vegetable oil polyol, catalyst, and auxiliary agents. The hydroxyl polyphosphate ester is a self-made long-chain phosphorus-containing polyol with a phosphate ester backbone and hydroxyl-terminated ends. It can not only replace part of the polyether polyol in the reaction with isocyanate to obtain a phosphorus-doped flame-retardant prepolymer, but also participate in the curing reaction after the mixture of components A and B, further increasing the phosphorus content in the polyurethane and thus further improving the flame-retardant performance. Therefore, the adhesive of this invention simultaneously possesses excellent flame-retardant properties, mechanical properties, and weather resistance.

Description

Technical Field

[0001] This application relates to the field of polyurethane materials technology, and more specifically, to a halogen-free flame-retardant modified two-component polyurethane adhesive and its preparation method. Background Technology

[0002] Currently, adhesives used in electrical components mainly fall into three categories: polyurethane, epoxy resin, and silicone. Compared to the latter two, polyurethane is widely used due to its excellent mechanical properties, good toughness, moderate adhesion, high elasticity, ease of casting, and room temperature curing. Many application areas, such as new energy vehicles, electronics, and construction and decoration, have increasingly stringent fire safety requirements, and they have also put forward specific requirements for the adhesives used, generally using FV-0 (UL-94) as an important flame retardant performance indicator. However, polyurethane materials themselves do not possess flame retardant capabilities; their structure contains a large number of carbon-hydrogen bonds, making them flammable materials. When exposed to an open flame, they burn rapidly, releasing heat, smoke, and toxic gases, threatening user safety. Therefore, how to improve the flame retardant properties of polyurethane adhesives is receiving increasing attention.

[0003] Flame retardants are an important component of polyurethane adhesive formulations. Based on their bonding method with the polyurethane matrix, they can be divided into additive flame retardants and reactive flame retardants. Additive flame retardants are added to the adhesive through physical blending, which is simple to process and low in cost, but they are prone to migration and precipitation, leading to a decrease in flame retardant performance and potentially causing degradation of the adhesive's bonding, mechanical, and electrical properties. Conversely, reactive flame retardants are chemically bonded to the polymer molecular chain. The strong binding force prevents the flame retardant from migrating, resulting in a long-lasting flame retardant effect.

[0004] Chinese patent document CN106221654A discloses a method for preparing a flame-retardant two-component polyurethane adhesive. In the preparation of the isocyanate-based component, flame-retardant elements are introduced into the polyurethane prepolymer by introducing a polyol containing flame-retardant groups and a reactive flame retardant. Simultaneously, the aforementioned two components are also added to the polyol component, achieving the inventor's designed co-flame-retardant modification of the soft and hard segments, resulting in a polyurethane adhesive with good flame-retardant properties. The mechanical properties can be improved by adjusting the formulation. However, this patent extensively uses halogen-containing substances such as polyepoxychloropropane and dibromoneopentyl glycol as flame-retardant element donors, which release toxic and corrosive fumes during combustion, posing environmental and health risks, and its use may be restricted.

[0005] Chinese patent document CN111808570A describes a method for preparing a two-component polyurethane adhesive. In the preparation of component B, polyether polyol, dimerized polyester polyol with side groups, and isocyanate are first polymerized, then reacted with a phosphorus-containing polyol to synthesize a phosphorus-containing flame-retardant functional prepolymer. This prepolymer, combined with the flame-retardant polyol in component A, is cured to obtain a polyurethane with excellent flame-retardant properties and good durability. However, to achieve an FV-0 flame retardancy rating, it is necessary to increase the amount of phosphorus-containing polyol in the prepolymer synthesis and the flame-retardant polyol in component A. But according to the test data of this patent, this significantly reduces the elongation at break of the material, affecting its mechanical properties.

[0006] Similarly, Chinese patent document CN110184016A uses isocyanate to react with diol and hydroxyl phosphorus flame retardant in sequence to prepare polyurethane prepolymer with certain flame retardant properties. However, this patent still requires a large amount of additive phosphate flame retardant in components A and B, which will affect the durability of the material.

[0007] In summary, although reactive flame retardants have many advantages, their application is technically challenging, and there are relatively few commercially available, high-performance reactive flame retardants. Phosphorus-based flame retardants are gradually replacing halogen-based flame retardants due to their low toxicity and low smoke levels; however, a large amount of phosphorus is required to achieve the desired flame retardant performance. Reactive flame retardants are mostly small molecules containing hydroxyl and flame-retardant groups. They replace some polyols in the reaction with isocyanates. Excessive use of reactive flame retardants reduces the proportion of soft segments in polyurethane, disrupts the regular arrangement of polymer molecular chains, and directly leads to a decrease in the material's mechanical properties. Furthermore, reactive flame retardants often have high hydroxyl values; excessive addition can severely alter the total amount of hydroxyl groups in the system, disrupting the original stoichiometric balance between hydroxyl groups and isocyanates. Therefore, it is difficult to achieve a good balance between the flame retardant and mechanical properties of the material. Summary of the Invention

[0008] To address the shortcomings of existing technologies, the purpose of this application is to provide a halogen-free flame-retardant modified two-component polyurethane adhesive and its preparation method. This aims to solve the technical problem that existing halogen-free flame-retardant two-component polyurethane adhesives use a large amount of reactive flame retardants, leading to an imbalance in the stoichiometry of hydroxyl and isocyanate esters in the polyurethane adhesive, making it difficult to balance flame-retardant and mechanical properties.

[0009] To achieve the above objectives, in a first aspect, this application provides a halogen-free flame-retardant modified two-component polyurethane adhesive, comprising a curing agent component A and a main agent component B; wherein, by weight parts, The curing agent component A comprises 50-80 parts of flame-retardant polyurethane prepolymer, 2-12 parts of isocyanate, and 15-35 parts of first auxiliary agent; The main component B includes 8-25 parts of hydroxy polyphosphate, 50-80 parts of polyether polyol, 5-30 parts of vegetable oil polyol, 0.1-2 parts of catalyst, and 1-10 parts of second auxiliary agent; The flame-retardant polyurethane prepolymer is obtained by polymerization of isocyanate, hydroxyl polyphosphate, and polyether polyol under the action of a catalyst; The hydroxy polyphosphate ester is a polyol with a phosphorus content of 15-25%, a hydroxyl value of 50-150 mgKOH / g, and an acid value not higher than 1.0 mgKOH / g.

[0010] Preferably, the preparation method of the flame-retardant polyurethane prepolymer includes the following steps: Mix 10-50 parts by weight of hydroxyl polyphosphate and 5-50 parts by weight of polyether polyol and heat to 100-120°C. After vacuum dehydration, cool to room temperature, add 45-55 parts by weight of isocyanate and 0-0.01 parts by weight of catalyst, heat to 80-90°C under nitrogen protection, maintain the temperature for 2-3 hours, cool to room temperature, discharge to obtain flame-retardant polyurethane prepolymer and seal for storage.

[0011] Preferably, the preparation method of the hydroxy polyphosphate ester includes the following steps: 30-45 parts by weight of a first diol and 10-20 parts by weight of a second diol are mixed, stirred, and cooled to 15-20°C; under nitrogen protection, 35-60 parts by weight of phosphorus pentoxide are slowly added in batches, and the temperature is continuously lowered during the reaction, controlled below 50°C; after the phosphorus pentoxide is added, the reaction temperature is gradually increased, first slowly raised to 70-80°C and maintained at this temperature for 1-2 hours, then raised to 100-110°C and maintained at this temperature for 2-3 hours; the temperature is lowered to 70-80°C, 2-5 parts by weight of a third diol are added for end-capping, and the reaction temperature is maintained at 70-80°C for 1-2 hours until the acid value decreases to below 1.0 mgKOH / g; the temperature is lowered to below 60°C, the hydroxy polyphosphate ester is discharged, and sealed for storage. The first diol, the second diol, and the third diol are selected from one or more of diethylene glycol, triethylene glycol, dipropylene glycol, butanediol, propylene glycol, ethylene glycol, and neopentyl glycol.

[0012] According to another aspect of the present invention, a method for preparing the polyurethane adhesive is provided, comprising the following steps: (1) Mix the flame-retardant polyurethane prepolymer, isocyanate monomer and first auxiliary agent evenly, degas under vacuum and seal to obtain component A; (2) The hydroxy polyphosphate, polyether polyol and vegetable oil polyol are dehydrated under vacuum at 100~120℃ for 1-3h respectively, and cooled to room temperature; the dehydrated hydroxy polyphosphate, polyether polyol, vegetable oil polyol and catalyst and second auxiliary agent are weighed according to the proportion, mixed evenly, degassed under vacuum and sealed to obtain component B. (3) When using, mix the components A and B at a mass ratio of 95~105:100, stir thoroughly and degas under vacuum, pour the mixed adhesive onto the device to be coated, and cure fully at room temperature or 60~80℃.

[0013] Overall, the technical solutions conceived in this application have the following beneficial effects compared with the prior art: This invention provides a halogen-free flame-retardant modified two-component polyurethane adhesive comprising two components, A and B. Component A consists of a flame-retardant polyurethane prepolymer, isocyanate monomer, and additives. Component B consists of hydroxyl polyphosphate, polyether polyol, vegetable oil polyol, catalyst, and additives. The hydroxyl polyphosphate is a self-made long-chain phosphorus-containing polyol with a phosphate ester backbone and hydroxyl-terminated ends. It can not only replace part of the polyether polyol in the reaction with isocyanate to obtain a phosphorus-doped flame-retardant prepolymer, but can also be added to component B to participate in the curing reaction after mixing components A and B, further increasing the phosphorus content in the polyurethane and thus improving its flame-retardant performance. Its high phosphorus content and low hydroxyl value allow it to introduce a large amount of flame-retardant phosphorus into the polyurethane without disrupting the uniform distribution of soft and hard segments in the polyurethane structure or the stoichiometric balance of hydroxyl and isocyanate in the system. Therefore, the resulting polyurethane adhesive can achieve excellent flame retardant properties and maintain good mechanical properties. The phosphorus, which is covalently bonded to the polyurethane, can also reduce migration problems during long-term use and improve the durability of material properties. Detailed Implementation

[0014] To make the objectives, technical solutions, and advantages of this application clearer, the following detailed description is provided in conjunction with embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the scope of this application.

[0015] This invention provides a halogen-free flame-retardant modified two-component polyurethane adhesive, comprising a curing agent component A and a main agent component B; wherein, by weight, The curing agent component A comprises 50-80 parts of flame-retardant polyurethane prepolymer, 2-12 parts of isocyanate, and 15-35 parts of first auxiliary agent; The main component B comprises 8-25 parts of hydroxy polyphosphate ester, 50-80 parts of polyether polyol, 5-30 parts of vegetable oil polyol, 0.1-2 parts of catalyst, and 1-10 parts of a second excipient; the hydroxy polyphosphate ester is a polyol with a phosphorus content of 15-25%, a hydroxyl value of 50-150 mgKOH / g, and an acid value not exceeding 1.0 mgKOH / g. More preferably, the hydroxyl value of the hydroxy polyphosphate ester is 100-150 mgKOH / g; and the polyether polyol in the main component B is 50-70 parts.

[0016] The flame-retardant polyurethane prepolymer is obtained by polymerizing isocyanate, hydroxyl polyphosphate, and polyether polyol under the action of a catalyst; the prepolymer contains a high content of phosphorus, thus obtaining excellent intrinsic flame-retardant properties.

[0017] The curing agent A component of this invention contains isocyanate, and isocyanate is also used in the preparation of flame-retardant polyurethane prepolymer. The isocyanates used in these two places can be the same or different. In some embodiments, the isocyanates used in the curing agent component A and the preparation of the flame-retardant polyurethane prepolymer are both aromatic polyisocyanates with a functionality ≥2, each independently selected from one or more of phenyl diisocyanate, toluene diisocyanate, diphenylmethane diisocyanate, carbodiimide-modified diphenylmethane diisocyanate, biphenyl diisocyanate, polymethylene polyphenyl isocyanate, polymethylene polyphenyl isocyanate, and naphthalene diisocyanate; similarly, the polyether polyols in the main agent component B and the polyether polyols used in the preparation of the flame-retardant polyurethane prepolymer both meet the following requirements: hydroxyl value of 20~360mgKOH / g, molecular weight of 500-5000, functionality of 2-3, each independently selected from one or more of the following polyols: glycerol-based polyether polyol, polypropylene oxide polyol, polyethylene oxide polyol, polytetrahydrofuran polyol, or copolyols of two or more of the above. The catalyst is an organometallic catalyst, selected from one or more of dibutyltin dilaurate, stannous octoate, zinc neodecanoate, bismuth neodecanoate, and bismuth isooctanoate.

[0018] In some embodiments, the preparation method of the flame-retardant polyurethane prepolymer includes the following steps: mixing 10-50 parts by weight of hydroxy polyphosphate and 5-50 parts by weight (more preferably 10-40 parts by weight) of polyether polyol and heating to 100-120°C, removing water under vacuum and then cooling to room temperature, adding 45-55 parts by weight of isocyanate and 0-0.01 parts by weight of catalyst, heating to 80-90°C under nitrogen protection, maintaining the temperature for 2-3 hours, cooling to room temperature, discharging to obtain the flame-retardant polyurethane prepolymer and sealing for storage.

[0019] In order to balance excellent mechanical properties and flame retardant effect, the proportion of hydroxyl polyphosphate in the total mass of curing agent A component and main agent B component in the halogen-free flame retardant modified two-component polyurethane adhesive of the present invention is preferably 10wt%-30wt%, more preferably 15wt%-30wt%, and most preferably 15wt%-20wt%.

[0020] This invention synthesizes hydroxy polyphosphates using phosphorus pentoxide as the phosphorus source through a staged reaction with different types of diols. In some embodiments, the preparation method includes the following steps: 30-45 parts by weight of a first diol and 10-20 parts by weight of a second diol are mixed, stirred, and cooled to 15-20°C; under nitrogen protection, 35-60 parts by weight of phosphorus pentoxide are slowly added in batches, while continuously cooling the mixture to below 50°C during the reaction; after the phosphorus pentoxide addition is complete, the reaction temperature is gradually increased, first slowly to 70-80°C and maintained at this temperature for 1-2 hours, then further increased to 100-110°C and maintained at this temperature for 2-3 hours; the temperature is then lowered to 70-80°C, and 2-5 parts by weight of a third diol are added for end-capping, maintaining the reaction at 70-80°C for 1-2 hours until the acid value decreases to 1.0. The concentration of KOH in the sample is below mg / g; the temperature is lowered to below 60°C, and the hydroxyl polyphosphate is discharged and sealed for storage. The first, second, and third diols are each independently selected from one or more of diethylene glycol, triethylene glycol, dipropylene glycol, butanediol, propylene glycol, ethylene glycol, and neopentyl glycol.

[0021] In some embodiments, the vegetable oil polyol is a polyol with a hydroxyl value of 150-200 mg KOH / g and a functionality of 2-3, selected from castor oil polyol and / or palm oil polyol.

[0022] The excipients and additives of this invention can be selected from common additives in the field of polyurethane adhesives. In some embodiments, the first excipient and additive is a plasticizer, and the second excipient and additive is one or more of defoamers, chain extenders, crosslinking agents, antioxidants, and coupling agents. The plasticizer is selected from one or more of dioctyl terephthalate, diisononyl phthalate, diisodecyl phthalate, and dioctyl terephthalate. The defoamer includes, but is not limited to, mineral oils, polyethers, silicones, polyether-modified silicones, and non-silicone polymer defoamers; the chain extender includes, but is not limited to, 1,4-butanediol and neopentyl glycol; the crosslinking agent includes, but is not limited to, glycerol and triethanolamine; the antioxidant includes, but is not limited to, hindered phenols, phosphites, and aromatic amines; and the coupling agent is a silane coupling agent or other commonly used coupling agents in the art.

[0023] The present invention also provides a method for preparing the polyurethane adhesive, comprising the following steps: (1) Mix the flame-retardant polyurethane prepolymer, isocyanate monomer and first auxiliary agent evenly, degas under vacuum and seal to obtain component A; (2) The hydroxy polyphosphate, polyether polyol and vegetable oil polyol are dehydrated under vacuum at 100~120℃ for 1-3h respectively, and cooled to room temperature; the dehydrated hydroxy polyphosphate, polyether polyol, vegetable oil polyol and catalyst and second auxiliary agent are weighed according to the proportion, mixed evenly, degassed under vacuum and sealed to obtain component B. (3) When using, mix the components A and B at a mass ratio of 95~105:100, stir thoroughly and degas under vacuum, pour the mixed adhesive onto the device to be coated, and cure fully at room temperature or 60~80℃.

[0024] This invention involves a staged reaction of phosphorus pentoxide with various diols to prepare a long-chain hydroxyl polyphosphate with a phosphate ester backbone and hydroxyl-terminated ends. This polyphosphate is then used to replace part of the polyether polyol in the reaction with isocyanate to obtain a flame-retardant polyurethane prepolymer. The advantages of this method are that, unlike common small-molecule phosphorus-containing reactive flame retardants, the self-made hydroxyl polyphosphate molecules are longer and can be considered soft segments embedded in the polyurethane chain, which helps maintain the material's mechanical properties. Furthermore, the hydroxyl polyphosphate has a lower hydroxyl value, close to that of polyether polyols, making it easier to introduce into the polyurethane system without disrupting stoichiometric equilibrium. In addition, the presence of multiple phosphorus atoms in the hydroxyl polyphosphate molecule allows for a more effective increase in the flame-retardant element content within the polyurethane structure.

[0025] The embodiments of the present invention are implemented under the premise of the technical solution of the present invention, and detailed implementation methods and processes are given. However, the protection scope of the present invention is not limited to the following embodiments. The process parameters in the following embodiments that do not specify specific conditions are generally in accordance with conventional conditions.

[0026] The endpoints and any values ​​of the ranges disclosed in this invention are not limited to the precise ranges or values, and these ranges or values ​​should be understood to include values ​​close to these ranges or values. For numerical ranges, the endpoint values ​​of the various ranges, the endpoint values ​​of the various ranges and individual point values, and individual point values ​​can be combined with each other to obtain one or more new numerical ranges, which should be considered as specifically disclosed in this invention.

[0027] In the embodiments of this invention, percentages refer to mass percentages, and parts refer to parts by mass. All raw materials used in this invention are commercially available.

[0028] The following are examples and comparative examples: The preparation of the two-component polyurethane adhesive in the following examples and comparative examples includes the following steps: Preparation of hydroxyl polyphosphate S1: 37.6 parts of diethylene glycol and 14 parts of propylene glycol were added to a reactor, stirred and mixed, protected with nitrogen gas and cooled to 15-20°C; under nitrogen protection, 45 parts of phosphorus pentoxide were slowly added in batches. The reaction was exothermic, and the temperature was controlled below 50°C during this process; after the phosphorus pentoxide was added, the temperature was slowly raised to 70-80°C and maintained in this temperature range for 1 hour, then the temperature was raised to 100-110°C and maintained in this temperature range for 2.5 hours; the temperature was lowered to 70-80°C, and 3.4 parts of ethylene glycol were added. The reaction temperature was maintained at 70-80°C for 1.5 hours until the acid value obtained by sampling test decreased to below 1.0 mg KOH / g; after the reaction was completed, the temperature was lowered. When the temperature dropped to below 60°C, the product was discharged to obtain hydroxyl polyphosphate S1, which was then sealed and stored. The obtained hydroxyl polyphosphate had a phosphorus content of 20% and a hydroxyl value of 135 mg KOH / g.

[0029] Preparation of hydroxyl polyphosphate S2: 24 parts diethylene glycol and 26 parts propylene glycol were added to a reactor, stirred and mixed, protected with nitrogen gas and cooled to 15-20°C; under nitrogen protection, 45 parts phosphorus pentoxide were slowly added in batches. The reaction was exothermic, and the temperature was controlled below 50°C during this process; after the phosphorus pentoxide was added, the temperature was slowly raised to 70-80°C and maintained in this temperature range for 1 hour, then the temperature was raised to 100-110°C and maintained in this temperature range for 2.5 hours; the temperature was lowered to 70-80°C, 5 parts ethylene glycol were added, and the reaction was maintained at 70-80°C for 1.5 hours until the acid value obtained by sampling test decreased to below 1.0 mg KOH / g; after the reaction was completed, the temperature was lowered, and the product was discharged when the temperature dropped below 60°C to obtain hydroxyl polyphosphate S2, which was then sealed and stored. The obtained hydroxyl polyphosphate had a phosphorus content of 20% and a hydroxyl value of 195 mg KOH / g.

[0030] Preparation of polyurethane prepolymer: Weigh the self-made hydroxy polyphosphate S1 or S2 and polyether polyol (DL-1000D) according to the designed stoichiometry, add them to the reactor and stir to mix. Vacuum the reactor and heat it to 100~120℃ to remove water for 2 hours. After water removal, cool it to room temperature. Add diphenylmethane diisocyanate (MDI-50) and a trace amount of dibutyltin dilaurate catalyst (0.005% of the total mass of reactants) according to the designed stoichiometry. Heat the reactor to 80~90℃ under nitrogen protection and maintain the temperature for 2.5 hours. Cool it to room temperature, discharge the polyurethane prepolymer and seal it for storage. The proportions of reactants added to synthesize polyurethane prepolymers P0-P3 according to the above steps are shown in Table 1 (the proportions are mass percentages, and are based on the total of hydroxy polyphosphate, polyether polyol and isocyanate being 100%).

[0031] Table 1. Reactant ratios for preparing polyurethane prepolymers P0-P3 in comparative examples and embodiments.

[0032] Preparation of component A: According to the formulation design of component A, the self-made polyurethane prepolymer, carbodiimide-modified diphenylmethane diisocyanate (CDMDI-100L), and plasticizer diisononyl phthalate were weighed and added to a container. The container was then placed in a vacuum mixer for mixing and degassing to obtain component A. The mixture was then discharged, sealed, and stored. The formulation composition of the prepared components A0-A3 is shown in Table 2 (the proportions are by mass percentage).

[0033] Table 2 Formulation table for preparing component A0-A3 in comparative examples and embodiments

[0034] Preparation of component B: Self-made hydroxy polyphosphate, polyether polyol (DL-1000D), and castor oil were dehydrated separately at 110℃ under vacuum for 2 hours, and then cooled to room temperature. The dehydrated hydroxy polyphosphate, polyether polyol (DL-1000D), castor oil, mineral oil defoamer 2410, coupling agent KH550, hindered phenolic antioxidant 1790, and dibutyltin dilaurate catalyst were weighed according to the formulation of component B and added to a container. The container was then placed in a vacuum mixer for mixing and degassing to obtain component B, which was then discharged and sealed for storage. The formulation components of the prepared components B0-B3 are shown in Table 3 (proportions are by mass percentage).

[0035] Table 3 Formulation table for preparing component B0-B3 in comparative examples and embodiments

[0036] The components A and B of each embodiment and comparative example were mixed at a mass ratio of 1:1 and the following performance tests were conducted. The test results are shown in Table 4.

[0037] (1) Tensile test: Mix components A and B and pour the adhesive to make a 2mm sample. After curing at room temperature (RT) for 72h, cut the sample into dumbbell-shaped strips according to the GB / T 528-2009 test standard and test according to the standard to obtain the elongation at break and tensile strength.

[0038] (2) Flame retardancy rating test: After mixing components A and B, the mixture is poured into a 3mm sample strip and cured at room temperature (RT) for 72 hours. The flame retardancy performance is then tested according to the UL-94 standard. The same sample strip is placed in a constant temperature and humidity chamber at 85℃ and 85%RH for 500 hours of double 85 aging treatment. After being taken out and placed in a standard environment at 23℃ and 50%RH for 24 hours, the flame retardancy performance is tested again.

[0039] Table 4. Tensile and flame retardant test results of two-component polyurethane adhesives A and B after curing in different comparative examples and embodiments.

[0040] The flame retardancy test results of two-component polyurethane adhesives with different formulations are shown in Table 4. In Comparative Example 1 (A0-B0), no self-made hydroxyl polyphosphate was used in the preparation of components A and B. The reaction of isocyanate was only carried out by polyether polyol and castor oil. Therefore, none of the components in the formulation had flame retardant properties, resulting in a poor flame retardancy rating (V2). In Comparative Examples 2 and 3, A1-B0 and A0-B1 respectively used hydroxyl polyphosphate S1 in the prepolymer of component A and component B. However, the amount of hydroxyl polyphosphate used in either component A or B was limited, so the flame retardancy rating of the resulting polyurethane was not significantly improved. On the other hand, when hydroxyl polyphosphate S1 was used in both components A and B simultaneously, the flame retardancy rating of the resulting polyurethane was improved. In Example 1 (A1-B1), the amount of hydroxy polyphosphate S1 used in the preparation process of components A and B accounted for 10.2% of the total mass of A and B, and its flame retardancy rating was V1. Examples 2 and 3 (A1-B2 and A2-B1) increased the amount of hydroxy polyphosphate S1 in components B and A, respectively, increasing the proportion of hydroxy polyphosphate S1 in the total mass of A and B to over 15%, and further improving the flame retardancy rating of the material to V0. In addition, the materials of each example were subjected to double 85 aging treatment and then flame retardancy testing. It was found that the flame retardancy performance of the materials did not change compared with that before aging, indicating that the phosphorus element introduced into the polyurethane by hydroxy polyphosphate is strongly bonded to the material through chemical bonds, and therefore will not be released during the aging process, thus preventing a decrease in flame retardancy performance.

[0041] According to the tensile test results, Comparative Example 1 (A0-B0) did not use hydroxyl polyphosphate in its A and B components, and the resulting polyurethane material had an elongation at break and a tensile strength of 73% and 0.91 MPa, respectively. In Examples 1 to 3 (A1-B1, A1-B2, A2-B1), hydroxyl polyphosphate S1 with a lower hydroxyl value and longer molecular chain was used in both A and B components, and the elongation at break and tensile strength of the resulting polyurethane material did not change significantly compared to Comparative Example 1 (A0-B0). However, Comparative Example 4 (A3-B3) used hydroxyl polyphosphate S2 with the same phosphorus content but a higher hydroxyl value and shorter molecular chain, and the elongation at break of the resulting polyurethane was significantly reduced. It can be seen that when hydroxyl polyphosphate is used to replace part of the polyether polyol in the reaction with isocyanate, the molecular chain of the hydroxyl polyphosphate must be long enough to avoid deteriorating the mechanical properties of the material.

[0042] The above results demonstrate that by synthesizing long-chain hydroxyl polyphosphates with phosphate ester as the backbone and hydroxyl end capping, and replacing part of the polyether polyol, the flame retardant properties of two-component polyurethane adhesives can be effectively improved and they can have long-term weather resistance, without negatively affecting the mechanical properties of the material.

[0043] The above description is merely a specific embodiment of this application, but the scope of protection of this application is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art within the scope of the technology disclosed in this application should be included within the scope of protection of this application. Therefore, the scope of protection of this application should be determined by the scope of the claims.

Claims

1. A halogen-free flame-retardant modified two-component polyurethane adhesive, characterized in that, It includes curing agent component A and main agent component B; wherein, by mass parts, The curing agent component A comprises 50-80 parts of flame-retardant polyurethane prepolymer, 2-12 parts of isocyanate, and 15-35 parts of first auxiliary material; The main component B includes 8-25 parts of hydroxy polyphosphate, 50-80 parts of polyether polyol, 5-30 parts of vegetable oil polyol, 0.1-2 parts of catalyst, and 1-10 parts of second auxiliary agent; The flame-retardant polyurethane prepolymer is obtained by polymerization of isocyanate, hydroxyl polyphosphate, and polyether polyol under the action of a catalyst; The hydroxy polyphosphate ester is a polyol with a phosphorus content of 15-25%, a hydroxyl value of 50-150 mgKOH / g, and an acid value not higher than 1.0 mgKOH / g.

2. The polyurethane adhesive as described in claim 1, characterized in that, The isocyanate is an aromatic polyisocyanate with a functionality ≥2, selected from one or more of phenyl diisocyanate, toluene diisocyanate, diphenylmethane diisocyanate, carbodiimide-modified diphenylmethane diisocyanate, biphenyl diisocyanate, polymethylene polyphenyl isocyanate, polymethyl polyphenyl isocyanate, and naphthalene diisocyanate.

3. The polyurethane adhesive as described in claim 1, characterized in that, The polyether polyol has a hydroxyl value of 20-360 mgKOH / g, a molecular weight of 500-5000, and a functionality of 2-3, and is selected from one or more of the following polyols: glycerol-based polyether polyol, polypropylene oxide polyol, polyethylene oxide polyol, polytetrahydrofuran polyol, or copolyols of two or more of the above.

4. The polyurethane adhesive as described in claim 1, characterized in that, The catalyst is an organometallic catalyst, selected from one or more of dibutyltin dilaurate, stannous octoate, zinc neodecanoate, bismuth neodecanoate, and bismuth isooctanoate.

5. The polyurethane adhesive as described in claim 1, characterized in that, The preparation method of the flame-retardant polyurethane prepolymer includes the following steps: Mix 10-50 parts by weight of hydroxyl polyphosphate and 5-50 parts by weight of polyether polyol and heat to 100-120°C. After vacuum dehydration, cool to room temperature, add 45-55 parts by weight of isocyanate and 0-0.01 parts by weight of catalyst, heat to 80-90°C under nitrogen protection, maintain the temperature for 2-3 hours, cool to room temperature, discharge to obtain flame-retardant polyurethane prepolymer and seal for storage.

6. The polyurethane adhesive as described in claim 1, characterized in that, The preparation method of the hydroxy polyphosphate ester includes the following steps: 30-45 parts by weight of a first diol and 10-20 parts by weight of a second diol are mixed, stirred, and cooled to 15-20°C; under nitrogen protection, 35-60 parts by weight of phosphorus pentoxide are slowly added in batches, and the temperature is continuously lowered during the reaction, controlled below 50°C; after the phosphorus pentoxide is added, the reaction temperature is gradually increased, first slowly raised to 70-80°C and maintained at this temperature for 1-2 hours, then raised to 100-110°C and maintained at this temperature for 2-3 hours; the temperature is lowered to 70-80°C, 2-5 parts by weight of a third diol are added for end-capping, and the reaction temperature is maintained at 70-80°C for 1-2 hours until the acid value decreases to below 1.0 mgKOH / g; the temperature is lowered to below 60°C, the hydroxy polyphosphate ester is discharged, and sealed for storage. The first diol, the second diol, and the third diol are selected from one or more of diethylene glycol, triethylene glycol, dipropylene glycol, butanediol, propylene glycol, ethylene glycol, and neopentyl glycol.

7. The polyurethane adhesive as described in claim 1, characterized in that, The plant oil polyol is a polyol with a hydroxyl value of 150~200mgKOH / g and a functionality of 2~3, selected from castor oil polyol and / or palm oil polyol.

8. The polyurethane adhesive as described in claim 1, characterized in that, The first excipient is a plasticizer, and the second excipient is one or more of the following: defoamer, chain extender, crosslinking agent, antioxidant, and coupling agent.

9. The polyurethane adhesive as described in claim 8, characterized in that, The plasticizer is selected from one or more of dioctyl terephthalate, diisononyl phthalate, diisodecyl phthalate, and dioctyl terephthalate.

10. The method for preparing the polyurethane adhesive according to any one of claims 1 to 9, characterized in that, Includes the following steps: (1) Mix the flame-retardant polyurethane prepolymer, isocyanate monomer and first auxiliary agent evenly according to the mixing ratio, and seal after vacuum degassing to obtain component A; (2) The hydroxy polyphosphate, polyether polyol and vegetable oil polyol were dehydrated under vacuum at 100~120℃ for 1-3h and cooled to room temperature. The dehydrated hydroxy polyphosphate, polyether polyol, vegetable oil polyol, catalyst and second auxiliary agent were weighed according to the proportion, mixed evenly, degassed under vacuum and sealed to obtain component B. (3) When using, mix the components A and B at a mass ratio of 95~105:100, stir thoroughly and degas under vacuum, pour the mixed adhesive onto the device to be coated, and cure fully at room temperature or 60~80℃.

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