A carbon dioxide-based flame-retardant two-component polyurethane structural adhesive and its preparation method

Abstract

The present invention belongs to the field of polyurethane adhesives, and relates to a carbon dioxide-based flame-retardant two-component polyurethane structural adhesive and a preparation method thereof. The carbon dioxide-based flame-retardant two-component polyurethane structural adhesive comprises component A and component B; component A comprises an isocyanate double-terminated polyurethane prepolymer, a first flame retardant and optionally a first auxiliary agent, and the isocyanate double-terminated polyurethane prepolymer is obtained by subjecting a modified carbon dioxide-based polycarbonate diol, a castor oil polyol and a polyisocyanate to a nucleophilic addition reaction optionally in the presence of a first catalyst; component B comprises a polyether polyol, a polybutadiene polyol, a small molecule polyol, a second flame retardant and optionally a second catalyst and a second auxiliary agent. The carbon dioxide-based flame-retardant two-component polyurethane structural adhesive provided by the present invention has excellent bonding strength, fatigue resistance, vibration resistance and flame retardant performance at the same time.

Description

Technical Field

[0001] The present invention belongs to the field of polyurethane adhesives, and particularly relates to a carbon dioxide-based flame-retardant two-component polyurethane structural adhesive and a preparation method thereof. Background Art

[0002] In recent years, new energy vehicles have developed rapidly, and the rapid development of the new energy industry has promoted the development and improvement of related industries. Functional adhesive products play an important role in aspects such as the structural stability, vibration and noise reduction, sealing and rust prevention, heat insulation and noise elimination, fastening and loosening prevention, simplification of manufacturing processes, and reduction of vehicle body weight of new energy vehicle batteries. In terms of adhesives for battery PACK structure bonding, the surface materials of power battery PACK modules include various functional materials such as PET, PC, and aluminum alloy. It is required that the structural adhesive has good adhesion to various materials without surface treatment, and at the same time has a medium elastic modulus and excellent flame retardancy to meet the working conditions of high-frequency vibration of power batteries and adapt to the use requirements in extremely cold and high-temperature regions of vehicles.

[0003] In the prior art, although epoxy adhesives and acrylate adhesives have extremely high bonding strengths, they generally have problems such as high hardness, high modulus, and low tolerance to thermal shock and high-frequency vibration conditions. Two-component polyurethane adhesives have advantages such as a long storage period and adjustable modulus, and have gradually received attention in the structural bonding of lithium battery PACKs. However, on the one hand, most of the key raw materials - polyol polymers in traditional polyurethane adhesives come from limited fossil fuel resources, which greatly restricts the green and environmental protection development of polyurethane adhesives; on the other hand, the bonding strength of polyurethane adhesives prepared using conventional polyester polyols and polyether polyols still needs to be further improved.

[0004] In summary, in order to meet the growing demand of new energy vehicles in the field of lithium battery PACK structure bonding, how to prepare a two-component polyurethane adhesive that is green and environmentally friendly and has excellent bonding strength, fatigue resistance, vibration resistance, and flame retardancy has become an urgent problem to be solved. Summary of the Invention

[0005] The first object of the present invention is to provide a carbon dioxide-based flame-retardant two-component polyurethane structural adhesive having good bonding strength, fatigue resistance, vibration resistance, and flame retardancy.

[0006] The second object of the present invention is to provide a preparation method of the above carbon dioxide-based flame-retardant two-component polyurethane structural adhesive.

[0007] Specifically, the carbon dioxide-based flame-retardant two-component polyurethane structural adhesive provided by the present invention comprises component A and component B which are stored independently; component A comprises an isocyanate-capped polyurethane prepolymer, a first flame retardant and optionally a first auxiliary agent, and the isocyanate-capped polyurethane prepolymer is obtained by a nucleophilic addition reaction of a modified carbon dioxide-based polycarbonate diol, a castor oil polyol and a polyisocyanate optionally in the presence of a first catalyst; component B comprises a polyether polyol, a polybutadiene polyol, a small molecule polyol, a second flame retardant and optionally a second catalyst and a second auxiliary agent; the modified carbon dioxide-based polycarbonate diol contains simultaneously a structural unit represented by formula (I), a structural unit represented by formula (II) and a structural unit represented by formula (III):

[0008]

[0009] In a specific embodiment, the modified carbon dioxide-based polycarbonate diol is represented by formula (IV):

[0010]

[0011] In formula (IV), m and n represent the molar proportions of the corresponding structural units, wherein 0.92 ≤ n ≤ 0.98 (such as 0.92, 0.93, 0.94, 0.95, 0.96, 0.97, 0.98, etc.), and m + n = 1. It should be noted that in formula (IV), the content of the structural unit derived from propylene oxide is represented by n and the content of the structural unit derived from 1,2-epoxy-4-vinylcyclohexane is represented by m, aiming to reflect the molar proportions of different structural units. Formula (IV) is only used to represent the types and proportions of the respective structural units, and cannot reflect the copolymerization reaction type and the connection relationship between the respective structural units. The modified carbon dioxide-based polycarbonate diol can be a random copolymer or a block copolymer.

[0012] The number-average molecular weight of the modified carbon dioxide-based polycarbonate diol is preferably 1800 - 4000, such as 1800, 2000, 2200, 2500, 2800, 3000, 3200, 3500, 3800, 4000, etc., but is not limited to the listed values, and other unlisted combinations within this range are equally applicable.

[0013] In a preferred embodiment, the volume ratio of component A to component B is (1 - 2):1, such as 1:1, 1.1:1, 1.2:1, 1.3:1, 1.4:1, 1.5:1, 1.6:1, 1.7:1, 1.8:1, 1.9:1, 2:1 or any value therebetween.

[0014] In a preferred embodiment, in component A, the content of the isocyanate - double - terminated polyurethane prepolymer is 55 - 110 parts by weight, such as 55, 60, 65, 70, 75, 80, 85, 90, 95, 100, 105, 110 parts by weight or any value therebetween; the content of the first flame retardant is 10 - 20 parts by weight, such as 10, 12, 15, 18, 20 parts by weight or any value therebetween; the content of the first additive is 0.1 - 5 parts by weight, such as 0.1, 0.5, 1, 2, 3, 4, 5 parts by weight or any value therebetween.

[0015] In a preferred embodiment, in component B, the content of the polyether polyol is 30 - 50 parts by weight, such as 30, 35, 40, 45, 50 parts by weight or any value therebetween; the content of the polybutadiene polyol is 20 - 35 parts by weight, such as 20, 22, 25, 28, 30, 32, 35 parts by weight or any value therebetween; the content of the small - molecule polyol is 1 - 5 parts by weight, such as 1, 2, 3, 4, 5 parts by weight or any value therebetween; the content of the second flame retardant is 10 - 20 parts by weight, such as 10, 12, 15, 18, 20 parts by weight or any value therebetween; the content of the second catalyst is 0 - 2 parts by weight, such as 0, 0.5, 1, 1.5, 2 parts by weight or any value therebetween; the content of the second additive is 0.1 - 5 parts by weight, such as 0.1, 0.5, 1, 2, 3, 4, 5 parts by weight or any value therebetween.

[0016] The modified carbon dioxide - based polycarbonate diol can be obtained by commercial purchase or prepared by various existing methods. In a preferred embodiment, the modified carbon dioxide - based polycarbonate diol is prepared by the following method:

[0017] S1. Place the third catalyst in a high - pressure reactor. Under the condition of 50 - 80 °C, evacuate and fill with CO2 in the high - pressure reactor for at least 2 h. Under the protection of CO2, add propylene oxide and 1,2 - epoxy - 4 - vinylcyclohexane into the high - pressure reactor, stir, and introduce CO2 into the reactor through a CO2 pressure regulator. The high - pressure reactor is placed in a constant - temperature bath at 28.5 - 32.0 atm for copolymerization reaction for 4 - 8 h. After the reaction, cool the high - pressure reactor to below 20 °C and slowly release the remaining CO2 to obtain the carbon dioxide - based polycarbonate diol;

[0018] S2. Add the carbon dioxide - based polycarbonate diol, cysteamine hydrochloride, free - radical photo - initiator and organic solvent into a reaction kettle and stir until the solid is completely dissolved, and then carry out the reaction under ultraviolet light irradiation to obtain the thiol - ene reaction product;

[0019] S3. Concentrate the thiol-ene reaction product, and then slowly add it to a non-solvent to precipitate the polymer. After filtration and drying, the modified carbon dioxide-based polycarbonate diol is obtained.

[0020] In a preferred embodiment, the molar ratio of the amount of the third catalyst to the total amount of propylene oxide and 1,2-epoxy-4-vinylcyclohexane is 1:(2000 - 7,000), such as 1:2000, 1:2500, 1:3000, 1:3500, 1:4000, 1:4500, 1:5000, 1:5500, 1:6000, 1:6500, 1:7000 or any value therebetween.

[0021] In a preferred embodiment, the molar ratio of 1,2-epoxy-4-vinylcyclohexane to propylene oxide is 1:(13 - 55), such as 1:13, 1:15, 1:20, 1:25, 1:30, 1:35, 1:40, 1:45, 1:50, 1:55 or any value therebetween.

[0022] In a preferred embodiment, the third catalyst is selected from one or more of a zinc carboxylate catalyst system, a zinc phenoxide catalyst system, a β-diketimine zinc catalyst system, a pyridine-zinc catalyst system, a porphyrin catalyst system, a SalenMX catalyst system, a rare earth catalyst system, a double metal cyanide catalyst system, and a supported catalyst system.

[0023] The radical photoinitiator can be various existing compounds that can absorb ultraviolet light energy to generate radicals, thereby initiating the thiol-ene click reaction between thiol groups and alkenyl groups. In a preferred embodiment, the radical photoinitiator is selected from 2-hydroxy-2-methyl-1-phenyl-1-propanone, 1-hydroxycyclohexyl phenyl ketone, 2-hydroxy-4-(2-hydroxyethoxy)-2-methylacetophenone, 2,4,6-trimethylbenzoyl-diphenylphosphine oxide, ethyl 2,4,6-trimethylbenzoyl phenylphosphinate, bis(2,4,6-trimethylbenzoyl)phenylphosphine oxide, 2-methyl-1-[4-(methylthio)phenyl]-2-(4-morpholinyl)-1-propanone, 2-benzyl-2-dimethylamino-1-(4-morpholinobenzylphenyl)butanone, 4-benzoyl-4'-methyl-diphenyl sulfide, 2-(4-methylbenzyl)-2-(dimethylamino)-1-(4-morpholinophenyl)-1-butanone, 1,1'-(methylenedi-4,1-phenylene)bis[2-hydroxy-2-methyl-1-propanone], 2,2-dimethoxy-2-phenylacetophenone, 2,2-diethoxy-1-phenylhexanone, bis(2,6-difluoro-3-pyrrolophenyl)titanocene, methyl benzoylformate, benzophenone, 4-methylbenzophenone, 4-phenylbenzophenone, 4-chlorobenzophenone, methyl o-benzoylbenzoate, ethyl 4-dimethylaminobenzoate, isooctyl 4-dimethylaminobenzoate, 4,4'-bis(diethylamino)benzophenone, isopropylthioxanthone, 2,4-diethylthioxanthone, and 2-ethylanthraquinone, or one or more of them.

[0024] In a preferred embodiment, in the preparation process of the isocyanate double-capped polyurethane prepolymer, the dosage of the modified carbon dioxide-based polycarbonate diol is 30-55 parts by weight, such as 30, 35, 40, 45, 50, 55 parts by weight or any value between them; the dosage of the castor oil polyol is 10-20 parts by weight, such as 10, 12, 15, 18, 20 parts by weight or any value between them; the dosage of the polyisocyanate is 15-25 parts by weight, such as 15, 18, 20, 22, 25 parts by weight or any value between them; the dosage of the first catalyst is 0-2 parts by weight, such as 0, 0.5, 1, 1.2, 1.5, 1.8, 2 parts by weight or any value between them.

[0025] The polyisocyanate is a compound with two or more isocyanate groups at the molecular chain terminals, and specifically can be an aromatic isocyanate and / or an aliphatic isocyanate. Specific examples include but are not limited to: toluene-2,4-diisocyanate, 4,4'-diphenylmethane diisocyanate, hexamethylene diisocyanate, cyclohexyl diisocyanate, isophorone diisocyanate, lysine diisocyanate, liquefied diphenylmethane diisocyanate, low-viscosity HDI trimer, and polymethylene polyphenyl polyisocyanate, or one or more of them.

[0026] In a preferred embodiment, the polyether polyol is selected from one or more of polyethylene glycol, polypropylene glycol, polytetrahydrofuran glycol, and their copolymer diols.

[0027] In a preferred embodiment, the number average molecular weight of the polyether polyol is 400 - 1000, such as 400, 500, 600, 700, 800, 900, 1000, or any value therebetween.

[0028] In a preferred embodiment, the polybutadiene polyol is selected from one or more of hydroxyl-terminated polybutadiene polyol, hydrogenated hydroxyl-terminated polybutadiene polyol, and hydroxyl-terminated polybutadiene-acrylonitrile polyol.

[0029] In a preferred embodiment, the number average molecular weight of the polybutadiene polyol is 1000 - 3000, such as 1000, 1200, 1500, 1800, 2000, 2200, 2500, 2800, 3000, or any value therebetween.

[0030] In a preferred embodiment, the small molecule polyol is selected from one or more of propylene glycol, butylene glycol, pentylene glycol, hexylene glycol, neopentyl glycol, cyclohexanedimethanol, glycerol, trimethylolpropane, and triethanolamine.

[0031] In a preferred embodiment, the first catalyst and the second catalyst are each independently selected from one or more of dibutyltin dilaurate, 2,2-dimorpholinodiethyl ether, organobismuth catalyst, and stannous octoate.

[0032] In a preferred embodiment, the first flame retardant and the second flame retardant are each independently selected from one or more of aluminum hydroxide, magnesium hydroxide, and antimony trioxide.

[0033] In a preferred embodiment, the first additive and the second additive are each independently selected from one or more of an interfacial treatment agent, an antifoaming agent, a thixotropic agent, a stabilizer, a water remover, a diluent, a toughening agent, an anti-aging agent, a pigment, and a filler. Among them, specific examples of the interfacial treatment agent include, but are not limited to, one or more of γ-aminopropyltrimethoxysilane, γ-aminopropyltriethoxysilane, N-β-(aminoethyl)-γ-aminopropyltrimethoxysilane, anilinomethyltriethoxysilane, γ-(2,3-epoxypropoxy)propyltrimethoxysilane, β-(3,4-epoxycyclohexyl)ethyltrimethoxysilane, and γ-ureidopropyltriethoxysilane. Specific examples of the antifoaming agent include, but are not limited to, one or more of a polymer-type antifoaming agent, a silicone antifoaming agent, and a mineral oil antifoaming agent. In addition, the thixotropic agent, the stabilizer, the water remover, the diluent, the toughening agent, the anti-aging agent, the pigment, and the filler can all be conventional selections in the art, and those skilled in the art are aware of this and will not be elaborated here.

[0034] The preparation method of the carbon dioxide-based flame-retardant two-component polyurethane structural adhesive provided by the present invention comprises the following steps:

[0035] Preparation of Component A: Put the modified carbon dioxide-based polycarbonate diol and castor oil polyol into a reaction kettle, heat up to 110 - 130 °C, stir and mix evenly under the condition that the vacuum degree is lower than -0.085 MPa, and carry out dehydration treatment for 1 - 2 hours. Then cool down to room temperature and introduce dry nitrogen to restore normal pressure. Add polyisocyanate and the first catalyst, heat and stir simultaneously, continue to react for 3 - 5 hours under nitrogen protection after heating up to 70 - 80 °C. Then add the first flame retardant and optionally the first additive, and stir and mix evenly while evacuating to obtain Component A;

[0036] Preparation of Component B: Stir and mix evenly the polyether polyol, polybutadiene polyol, small molecule polyol, the second flame retardant, and optionally the second catalyst and the second additive. Then heat up to 110 - 130 °C and carry out dehydration treatment under the condition that the vacuum degree is lower than -0.085 MPa. After cooling down to room temperature, introduce dry nitrogen to restore normal pressure to obtain Component B.

[0037] The key of the present invention lies in introducing, on the basis of traditional polyurethane adhesives, a modified carbon dioxide-based polycarbonate diol having a structural unit derived from propylene oxide, a six-membered ring, a flexible sulfur-containing group, and an amino group. This special structure can significantly improve the bonding strength and flexibility of polyurethane structural adhesives. With the use of flame retardants, the finally obtained polyurethane structural adhesives have excellent bonding strength, fatigue resistance, vibration resistance, and flame retardant properties. In addition, the modified carbon dioxide-based polycarbonate diol uses carbon dioxide as a raw material, and the corresponding polyurethane adhesives have the advantages of environmental friendliness, greenness, low cost, etc., which contribute to carbon emission reduction, conform to the concept of sustainable development, and meet economic and social benefits. Detailed implementation manners

[0038] The present invention will be described in detail below through examples.

[0039] In the following preparation examples, propylene oxide is selected from P109309 of Shanghai Aladdin Biochemical Technology Co., Ltd.; 1,2-epoxy-4-vinylcyclohexane is selected from Celloxide 2000 of Daicel Corporation of Japan; the photoinitiator DMPA is selected from 01049771 of Shanghai Titan Technology Co., Ltd.

[0040] In the following examples and comparative examples, castor oil polyol is selected from URIC AC008 of Ito Oil Co., Ltd. of Japan; polyether polyol is purchased from Guodu Chemical Co., Ltd., with the brand name GY420; polybutadiene polyol is purchased from Nippon Soda Co., Ltd. of Japan, with the brand name G-2000; the small molecule polyol is 1,4-butanediol, purchased from A040124 of Anychem Co., Ltd.; the polyisocyanate is polymethylene polyphenyl polyisocyanate, selected from PM-2025 of Wanhua Chemical Co., Ltd.; the first catalyst and the second catalyst are both 2,2-dimorpholinodiethyl ether, selected from B802012 of Shanghai Macklin Biochemical Co., Ltd.; the flame retardants are aluminum hydroxide and magnesium hydroxide micropowders. The aluminum hydroxide micropowder is selected from H-42 of Showa Denko K.K. of Japan, and the magnesium hydroxide micropowder is selected from MAGNIFIN-H5 of Albemarle Corporation of the United States; the interfacial treatment agent is γ-aminopropyltrimethoxysilane, selected from KBM-903 of Shin-Etsu Chemical Co., Ltd. of Japan; the defoaming agent is purchased from BYK Co., with the brand name BYK535; the thixotropic agent is fumed silica purchased from Cabot Corporation, with the brand name TS720.

[0041] In the following examples and comparative examples, the amounts of all raw materials are in parts by weight.

[0042] Preparation Example 1

[0043] This preparation example is used to illustrate the preparation of the modified carbon dioxide-based polycarbonate diol. The specific reaction steps are as follows:

[0044] Step 1: Place 0.68 g of SalenCo(Ⅲ)NO3 catalyst in a high-pressure reactor. Vacuumize and fill with CO2 the reactor at 60 °C for 2 h. Under the protection of CO2, add 209 g of propylene oxide and 29.8 g of 1,2-epoxy-4-vinylcyclohexane into the reactor, stir, and introduce CO2 into the reactor through a CO2 pressure regulator. The high-pressure reactor is placed in a constant-temperature bath at 28.5 - 32.0 atm for copolymerization reaction for 6 h. After the reaction is completed, cool the reactor to below 20 °C and slowly release the remaining CO2 to obtain 397 g of carbon dioxide-based polycarbonate diol;

[0045] Step 2: Add 350 g of carbon dioxide-based polycarbonate diol, 16.50 g of cysteamine hydrochloride, 2.68 g of free radical photoinitiator DMPA, and 500 mL of tetrahydrofuran into the reactor. Then stir the mixture until the solids are completely dissolved, and irradiate the reaction under ultraviolet light for 8 h to obtain a thiol-ene reaction product;

[0046] Step 3: Concentrate the thiol-ene reaction product, and then slowly add it to non-solvent methanol to dissolve and precipitate the polymer. After filtration and drying, a modified carbon dioxide-based polycarbonate diol with a number-average molecular weight of 3500 is obtained.

[0047] Preparation Example 2

[0048] This preparation example is used to illustrate the preparation of the modified carbon dioxide-based polycarbonate diol. The specific reaction steps are as follows:

[0049] Step 1: Place 0.11 g of SalenCo(Ⅲ)NO3 catalyst in a high-pressure reactor. Vacuumize and fill with CO2 the reactor at 60 °C for 2 h. Under the protection of CO2, add 209 g of propylene oxide and 29.8 g of 1,2-epoxy-4-vinylcyclohexane into the reactor, stir, and introduce CO2 into the reactor through a CO2 pressure regulator. The high-pressure reactor is placed in a constant-temperature bath at 28.5 - 32.0 atm for copolymerization reaction for 6 h. After the reaction is completed, cool the reactor to below 20 °C and slowly release the remaining CO2 to obtain 244 g of carbon dioxide-based polycarbonate diol;

[0050] Step 2: Add 200 g of carbon dioxide-based polycarbonate diol, 19.19 g of cysteamine hydrochloride, 3.10 g of free radical photoinitiator DMPA, and 300 mL of tetrahydrofuran into the reactor. Then stir the mixture until the solids are completely dissolved, and irradiate the reaction under ultraviolet light for 8 h to obtain a thiol-ene reaction product;

[0051] Step 3: Concentrate the thiol-ene reaction product, and then slowly add it to non-solvent methanol to dissolve and precipitate the polymer. After filtration and drying, a modified carbon dioxide-based polycarbonate diol with a number-average molecular weight of 1800 is obtained.

[0052] Preparation Example 3

[0053] 10.0 mg of DMC catalyst and 25.0 g of sebacic acid chain transfer agent were placed in a high-pressure reactor. The reactor was evacuated and filled with CO2 at 60 °C for 2 h. Under the protection of CO2, 100 g of propylene oxide was added to the reactor, stirred, and CO2 was introduced into the reactor through a CO2 pressure regulator. The high-pressure reactor was placed in a constant-temperature bath at 28.5 - 32.0 atm for copolymerization reaction for 6 h. After the reaction, the reactor was cooled to below 20 °C to slowly release the remaining CO2, and 90 mg of tris(pentafluorophenyl)borane and 10 g of propylene oxide were added to the reactor, and the temperature was raised to 100 °C and the reaction continued for 2 h. After the reaction, the reactor used for the polymerization reaction was cooled to room temperature with a cold water bath at 12 - 15 °C, and the unreacted propylene oxide was distilled off. The residue was dried to a constant weight in a vacuum drying oven at 40 °C, and thus 126.9 g of poly(carbonate-ether) diol with a number-average molecular weight of 1500 was obtained.

[0054] Preparation of Carbon Dioxide-Based Flame-Retardant Two-Component Polyurethane Structural Adhesive in Example 1

[0055] Preparation of Component A: 45 parts of the modified carbon dioxide-based polycarbonate diol prepared in Preparation Example 1 and 15 parts of castor oil polyol were put into a reaction kettle, heated to 120 °C, stirred and mixed evenly under the condition that the vacuum degree was lower than -0.085 MPa, and dehydrated for 2 hours. Then it was cooled to room temperature and dried nitrogen was introduced to restore normal pressure. 20 parts of polyisocyanate and 1 part of the first catalyst were added, heated and stirred, and the temperature was raised to 75 °C and the reaction continued for 4 hours under nitrogen protection. Then 7.5 parts of aluminum hydroxide and 7.5 parts of magnesium hydroxide, 1 part of γ-aminopropyltrimethoxysilane, 0.2 part of defoaming agent BYK535 and 2 parts of fumed silica TS720 were added, and stirred and mixed for 1 hour while evacuating, to obtain Component A;

[0056] Preparation of Component B: 40 parts of polyether polyol, 30 parts of polybutadiene polyol and 3 parts of small molecule polyol were put into another reaction kettle, then 1 part of the second catalyst, 7.5 parts of aluminum hydroxide and 7.5 parts of magnesium hydroxide, 1 part of γ-aminopropyltrimethoxysilane, 0.2 part of defoaming agent BYK535 and 2 parts of fumed silica TS720 were added, stirred and mixed, then heated to 120 °C, and dehydrated for 2 hours under the condition that the vacuum degree was lower than -0.085 MPa, cooled and dried nitrogen was introduced to restore normal pressure, to obtain Component B;

[0057] The volume ratio of Component A to Component B in the carbon dioxide-based flame-retardant two-component polyurethane structural adhesive is 1:1, and Component A and Component B are stored independently.

[0058] Preparation of Carbon Dioxide-based Flame Retardant Two-component Polyurethane Structural Adhesive in Example 2

[0059] Preparation of Component A: Put 30 parts of the modified carbon dioxide-based polycarbonate diol prepared in Preparation Example 1 and 10 parts of castor oil polyol into a reaction kettle, heat up to 120°C, stir and mix evenly under the condition that the vacuum degree is lower than -0.085 MPa, and carry out dehydration treatment for 2 hours. Then cool down to room temperature and introduce dry nitrogen to restore normal pressure. Add 15 parts of polyisocyanate and 0.7 part of the first catalyst, stir while heating, continue to react for 4 hours under nitrogen protection after heating up to 75°C. Then add 5 parts of aluminum hydroxide, 5 parts of magnesium hydroxide, 0.7 part of γ-aminopropyltrimethoxysilane, 0.1 part of defoamer BYK535 and 2 parts of fumed silica TS720, stir and mix under vacuum for 1 hour to obtain Component A;

[0060] Preparation of Component B: Put 30 parts of polyether polyol, 20 parts of polybutadiene polyol and 2 parts of small molecule polyol into another reaction kettle, then add 0.7 part of the second catalyst, 5 parts of aluminum hydroxide, 5 parts of magnesium hydroxide, 0.7 part of γ-aminopropyltrimethoxysilane, 0.1 part of defoamer BYK535 and 2 parts of fumed silica TS720, stir and mix. Then heat up to 120°C and carry out dehydration treatment for 2 hours under the condition that the vacuum degree is lower than -0.085 MPa. Cool down and introduce dry nitrogen to restore normal pressure to obtain Component B;

[0061] The volume ratio of Component A to Component B in the carbon dioxide-based flame retardant two-component polyurethane structural adhesive is 2:1, and Component A and Component B are stored independently.

[0062] Preparation of Carbon Dioxide-based Flame Retardant Two-component Polyurethane Structural Adhesive in Example 3

[0063] Preparation of Component A: Put 55 parts of the modified carbon dioxide-based polycarbonate diol prepared in Preparation Example 1 and 20 parts of castor oil polyol into a reaction kettle, heat up to 120°C, stir and mix evenly under the condition that the vacuum degree is lower than -0.085 MPa, and carry out dehydration treatment for 2 hours. Then cool down to room temperature and introduce dry nitrogen to restore normal pressure. Add 25 parts of polyisocyanate and 1.3 parts of the first catalyst, stir while heating, continue to react for 4 hours under nitrogen protection after heating up to 75°C. Then add 10 parts of aluminum hydroxide, 10 parts of magnesium hydroxide, 1.4 parts of γ-aminopropyltrimethoxysilane, 0.3 part of defoamer BYK535 and 2 parts of fumed silica TS720, stir and mix under vacuum for 1 hour to obtain Component A;

[0064] Preparation of Component B: Charge 50 parts of polyether polyol, 35 parts of polybutadiene polyol, and 4 parts of small molecule polyol into another reaction kettle, then add 1.3 parts of the second catalyst, 10 parts of aluminum hydroxide, 10 parts of magnesium hydroxide, 1.4 parts of γ-aminopropyltrimethoxysilane, 0.3 part of defoamer BYK535, and 2 parts of fumed silica TS720, stir and mix, then heat up to 120 °C, and conduct dehydration treatment for 2 hours under the condition that the vacuum degree is lower than -0.085 MPa, cool down and introduce dry nitrogen to restore normal pressure to obtain Component B;

[0065] The volume ratio of Component A to Component B in the carbon dioxide-based flame-retardant two-component polyurethane structural adhesive is 1.5:1, wherein Component A and Component B are stored independently.

[0066] Example 4

[0067] Prepare the carbon dioxide-based flame-retardant two-component polyurethane structural adhesive according to the method of Example 1, except that the modified carbon dioxide-based polycarbonate diol obtained from Preparation Example 1 is replaced with the modified carbon dioxide-based polycarbonate diol obtained from Preparation Example 2 in the same weight parts, and the other conditions are the same as those in Example 1 to obtain the carbon dioxide-based flame-retardant two-component polyurethane structural adhesive.

[0068] Example 5

[0069] Prepare the carbon dioxide-based flame-retardant two-component polyurethane structural adhesive according to the method of Example 2, except that the modified carbon dioxide-based polycarbonate diol obtained from Preparation Example 1 is replaced with the modified carbon dioxide-based polycarbonate diol obtained from Preparation Example 2 in the same weight parts, and the other conditions are the same as those in Example 2 to obtain the carbon dioxide-based flame-retardant two-component polyurethane structural adhesive.

[0070] Example 6

[0071] Prepare the carbon dioxide-based flame-retardant two-component polyurethane structural adhesive according to the method of Example 3, except that the modified carbon dioxide-based polycarbonate diol obtained from Preparation Example 1 is replaced with the modified carbon dioxide-based polycarbonate diol obtained from Preparation Example 2 in the same weight parts, and the other conditions are the same as those in Example 3 to obtain the carbon dioxide-based flame-retardant two-component polyurethane structural adhesive.

[0072] Comparative Example 1

[0073] Prepare the carbon dioxide-based flame-retardant two-component polyurethane structural adhesive according to the method of Example 1, except that the modified carbon dioxide-based polycarbonate diol obtained from Preparation Example 1 is replaced with the poly(carbonate-ether) diol obtained from Preparation Example 3 in the same weight parts, and the other conditions are the same as those in Example 1 to obtain the carbon dioxide-based flame-retardant two-component polyurethane structural adhesive.

[0074] Comparative Example 2

[0075] The carbon dioxide-based flame-retardant two-component polyurethane structural adhesive was prepared according to the method of Example 2, except that the modified carbon dioxide-based polycarbonate diol obtained from Preparation Example 1 was replaced with the poly(carbonate-ether) diol obtained from Preparation Example 3 in the same weight portion, and the remaining conditions were the same as those in Example 2, to obtain the carbon dioxide-based flame-retardant two-component polyurethane structural adhesive.

[0076] Comparative Example 3

[0077] The carbon dioxide-based flame-retardant two-component polyurethane structural adhesive was prepared according to the method of Example 3, except that the modified carbon dioxide-based polycarbonate diol obtained from Preparation Example 1 was replaced with the poly(carbonate-ether) diol obtained from Preparation Example 3 in the same weight portion, and the remaining conditions were the same as those in Example 3, to obtain the carbon dioxide-based flame-retardant two-component polyurethane structural adhesive.

[0078] Comparative Example 4

[0079] The flame-retardant two-component polyurethane structural adhesive was prepared according to the method of Example 1, except that the modified carbon dioxide-based polycarbonate diol obtained from Preparation Example 1 was replaced with the commercial polyester diol (Dynacoll 7250 from Evonik) in the same weight portion, and the remaining conditions were the same as those in Example 1, to obtain the flame-retardant two-component polyurethane structural adhesive.

[0080] Test Example

[0081] The samples obtained in Examples 1-6 and Comparative Examples 1-4 were respectively subjected to the following performance tests:

[0082] (1) Adhesive performance (tensile shear strength): Tested according to the standard GB / T 7124-2008 "Determination of Tensile Shear Strength of Adhesives (Rigid Material to Rigid Material)". Specifically, aluminum plates with dimensions of 100 mm × 25 mm × 2 mm were selected. Two aluminum plates were overlapped, and the bonding area was 12.5 mm × 25 mm, and the thickness of the adhesive layer was ensured to be 0.2 mm. The overlapped splines were placed in a constant temperature and humidity chamber at 25 °C and 50% RH for room temperature curing for seven days, and the tensile shear strength was tested using a universal material tensile force testing machine with a tensile speed of 5 mm / min. The obtained results are shown in Table 1.

[0083] (2) Elongation at break: Tested according to Standard GB / T 1040.3-2006. First, the two-component polyurethane adhesive is mixed through a static mixer and then injected into a tetrafluoroethylene mold with a thickness of 2 mm, leveled, and placed in a constant temperature and humidity chamber at 25°C and 50% RH for room temperature curing for 7 days. A dumbbell-shaped cutter with dimensions of 6 mm × 115 mm is used to cut the cured adhesive film to prepare specimens. A WDW3020 type electronic universal testing machine is used to conduct a tensile test on the specimens at room temperature, and the elongation at break data is recorded. The tensile speed is 10 mm / min. The obtained results are shown in Table 1.

[0084] (3) Young's modulus: At room temperature, the two-component polyurethane adhesive is mixed through a static mixer and then dispensed onto a release paper, and then laminated with another release paper, and then film-pressed to control the film thickness to 0.3 mm. The prepared adhesive film is placed in a constant temperature and humidity chamber (25°C / 50% RH) and left to cure at room temperature for 7 days. Then, the cured adhesive film is cut into a dumbbell shape and clamped onto a tensile testing machine for tensile testing, and the Young's modulus data is recorded. The obtained results are shown in Table 1.

[0085] (4) Flame retardant performance: First, the two-component polyurethane adhesive is mixed through a static mixer and then injected into a standard tetrafluoroethylene mold, leveled, and placed in a constant temperature and humidity chamber at 25°C and 50% RH for room temperature curing for 7 days. Then, the cured specimens are taken out and tested according to the UL94-2012 material vertical burning rating standard, and the flame retardant rating data is recorded. The obtained results are shown in Table 1.

[0086] Table 1

[0087]

[0088] As can be seen from the results in Table 1, the carbon dioxide-based flame retardant two-component polyurethane structural adhesive provided by the present invention has extremely excellent bonding strength, can reach the UL94 V0 flame retardant rating, and at the same time has a relatively high elongation at break and a relatively low modulus, so it has good flexibility, enabling it to meet the stringent requirements of the power battery high-frequency vibration working conditions for fatigue resistance and shock resistance. In addition, the modified carbon dioxide-based polycarbonate diol uses carbon dioxide as a raw material, and the corresponding two-component polyurethane structural adhesive has the advantages of environmental friendliness, greenness, low cost, etc., which helps to achieve carbon emission reduction, conforms to the concept of sustainable development, and conforms to economic and social benefits.

[0089] Although the embodiments of the present invention have been shown and described above, it can be understood that the above embodiments are exemplary and should not be construed as limiting the present invention. Those of ordinary skill in the art can make changes, modifications, substitutions, and variations to the above embodiments within the scope of the present invention without departing from the principles and purposes of the present invention.

Claims

1. A carbon dioxide-based flame-retardant two-component polyurethane structural adhesive, characterized in that, It includes component A and component B stored independently; component A includes isocyanate double-capped polyurethane prepolymer, the first flame retardant, and optionally the first auxiliary agent. The isocyanate double-capped polyurethane prepolymer is obtained by nucleophilic addition reaction of modified carbon dioxide-based polycarbonate diol, castor oil polyol, and polyisocyanate in the presence of a first catalyst; component B includes polyether polyol, polybutadiene polyol, small molecule polyol, the second flame retardant, and optionally the second catalyst and the second auxiliary agent; the modified carbon dioxide-based polycarbonate diol contains the structural unit shown in formula (Ⅰ), the structural unit shown in formula (Ⅱ), and the structural unit shown in formula (Ⅲ) at the same time: The volume ratio of component A to component B is (1 - 2):1; in component A, the content of the isocyanate double-capped polyurethane prepolymer is 55 - 110 parts by weight, the content of the first flame retardant is 10 - 20 parts by weight, and the content of the first auxiliary agent is 0.1 - 5 parts by weight; in component B, the content of the polyether polyol is 30 - 50 parts by weight, the content of the polybutadiene polyol is 20 - 35 parts by weight, the content of the small molecule polyol is 1 - 5 parts by weight, the content of the second flame retardant is 10 - 20 parts by weight, the content of the second catalyst is 0 - 2 parts by weight, and the content of the second auxiliary agent is 0.1 - 5 parts by weight.

2. The carbon dioxide-based flame-retardant two-component polyurethane structural adhesive according to claim 1, characterized in that, The modified carbon dioxide-based polycarbonate diol is prepared by the following method: S1. Place the third catalyst in a high-pressure reactor. Under the condition of 50 - 80 °C, evacuate and fill with CO2 in the high-pressure reactor for at least 2 h. Under the protection of CO2, add propylene oxide and 1,2-epoxy-4-vinylcyclohexane into the high-pressure reactor, stir, and introduce CO2 into the reactor through a CO2 pressure regulator. The high-pressure reactor is placed in a constant temperature bath at 28.5 - 32.0 atm for copolymerization reaction for 4 - 8 h. After the reaction is completed, cool the high-pressure reactor to below 20 °C and slowly release the remaining CO2 to obtain carbon dioxide-based polycarbonate diol; S2. Add the carbon dioxide-based polycarbonate diol, cysteamine hydrochloride, free radical photoinitiator, and organic solvent into the reactor and stir until the solid is completely dissolved. Then carry out the reaction under ultraviolet light irradiation to obtain a thiol-ene reaction product; S3. Concentrate the thiol-ene reaction product, and then slowly add it to a non-solvent to precipitate the polymer. After filtration and drying, the modified carbon dioxide-based polycarbonate diol is obtained.

3. The carbon dioxide-based flame-retardant two-component polyurethane structural adhesive according to claim 2, characterized in that, The molar ratio of the dosage of the third catalyst to the total dosage of propylene oxide and 1,2-epoxy-4-vinylcyclohexane is 1:(2000 - 7000); the molar ratio of 1,2-epoxy-4-vinylcyclohexane to propylene oxide is 1:(13 - 55).

4. The carbon dioxide-based flame-retardant two-component polyurethane structural adhesive according to claim 2, wherein The third catalyst is selected from one or more of a zinc carboxylate catalyst system, a zinc phenoxide catalyst system, a β-diketimine zinc catalyst system, a pyridine-zinc catalyst system, a porphyrin catalyst system, a SalenMX catalyst system, a rare earth catalyst system, a double metal cyanide catalyst system, and a supported catalyst system.

5. The carbon dioxide-based flame-retardant two-component polyurethane structural adhesive according to claim 2, characterized in that, The radical photoinitiator is selected from one or more of 2-hydroxy-2-methyl-1-phenyl-1-propanone, 1-hydroxycyclohexyl phenyl ketone, 2-hydroxy-4-(2-hydroxyethoxy)-2-methylpropiophenone, 2,4,6-trimethylbenzoyl-diphenylphosphine oxide, ethyl 2,4,6-trimethylbenzoyl phenylphosphinate, bis(2,4,6-trimethylbenzoyl)phenylphosphine oxide, 2-methyl-1-[4-(methylthio)phenyl]-2-(4-morpholinyl)-1-propanone, 2-benzyl-2-dimethylamino-1-(4-morpholinobenzylphenyl)butanone, 4-benzoyl-4'-methyl-diphenyl sulfide, 2-(4-methylbenzyl)-2-(dimethylamino)-1-(4-morpholinophenyl)-1-butanone, 1,1'-(methylenedi-4,1-phenylene)bis[2-hydroxy-2-methyl-1-propanone], 2,2-dimethoxy-2-phenylacetophenone, 2,2-diethoxy-1-phenylhexanone, bis(2,6-difluoro-3-pyrrolidinophenyl)titanocene dichloride, methyl benzoylformate, benzophenone, 4-methylbenzophenone, 4-phenylbenzophenone, 4-chlorobenzophenone, methyl o-benzoylbenzoate, ethyl 4-dimethylaminobenzoate, isooctyl 4-dimethylaminobenzoate, 4,4'-bis(diethylamino)benzophenone, isopropylthioxanthone, 2,4-diethylthioxanthone, and 2-ethylanthraquinone.

6. The carbon dioxide-based flame-retardant two-component polyurethane structural adhesive according to claim 1, characterized in that, In the preparation process of the isocyanate double-capped polyurethane prepolymer, the dosage of the modified carbon dioxide-based polycarbonate diol is 30-55 parts by weight, the dosage of the castor oil polyol is 10-20 parts by weight, the dosage of the polyisocyanate is 15-25 parts by weight, and the dosage of the first catalyst is 0-2 parts by weight.

7. The carbon dioxide-based flame-retardant two-component polyurethane structural adhesive according to claim 1, characterized in that, The polyether polyol is selected from one or more of polyethylene glycol, polypropylene glycol, polytetrahydrofuran glycol, and their copolymer diols; the number-average molecular weight of the polyether polyol is 400-1000.

8. The carbon dioxide-based flame-retardant two-component polyurethane structural adhesive according to claim 1, wherein The polybutadiene polyol is selected from one or more of hydroxyl-terminated polybutadiene polyol, hydrogenated hydroxyl-terminated polybutadiene polyol, and hydroxyl-terminated polybutadiene-acrylonitrile polyol; the number-average molecular weight of the polybutadiene polyol is 1000-3000.

9. The carbon dioxide-based flame-retardant two-component polyurethane structural adhesive according to claim 1, characterized in that, The small molecule polyol is selected from one or more of propylene glycol, butylene glycol, pentylene glycol, hexylene glycol, neopentyl glycol, cyclohexanedimethanol, glycerol, trimethylolpropane, and triethanolamine.

10. The carbon dioxide-based flame-retardant two-component polyurethane structural adhesive according to claim 1, characterized in that, The first catalyst and the second catalyst are each independently selected from one or more of dibutyltin dilaurate, 2,2-dimorpholinodiethylether, organic bismuth catalyst, and stannous octoate.

11. The carbon dioxide-based flame-retardant two-component polyurethane structural adhesive according to claim 1, characterized in that, The first flame retardant and the second flame retardant are each independently selected from one or more of aluminum hydroxide, magnesium hydroxide, and antimony trioxide.

12. The carbon dioxide-based flame-retardant two-component polyurethane structural adhesive according to claim 1, characterized in that, The first auxiliary agent and the second auxiliary agent are each independently selected from one or more of surface treatment agent, defoaming agent, thixotropic agent, stabilizer, water remover, diluent, toughening agent, anti-aging agent, pigment, and filler.

13. The preparation method of the carbon dioxide-based flame-retardant two-component polyurethane structural adhesive according to any one of claims 1-12, characterized in that, This method comprises the following steps: Preparation of Component A: Put the modified carbon dioxide-based polycarbonate diol and castor oil polyol into a reaction kettle, heat up to 110 - 130 °C, stir and mix evenly under the condition that the vacuum degree is lower than -0.085 MPa, and carry out dehydration treatment for 1 - 2 hours. Then cool down to room temperature and introduce dry nitrogen to restore normal pressure. Add polyisocyanate and the first catalyst, stir while heating, heat up to 70 - 80 °C and continue to react for 3 - 5 hours under nitrogen protection. Then add the first flame retardant and optionally the first auxiliary agent, stir and mix evenly while evacuating, and obtain Component A; Preparation of Component B: Stir and mix evenly the polyether polyol, polybutadiene polyol, small molecule polyol, the second flame retardant, and optionally the second catalyst and the second auxiliary agent. Then heat up to 110 - 130 °C and carry out dehydration treatment under the condition that the vacuum degree is lower than -0.085 MPa. After cooling to room temperature, introduce dry nitrogen to restore normal pressure to obtain Component B.

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