One-component polyurethane low-temperature heat-curing structural adhesive and preparation method thereof

Abstract

The present application relates to a one-component polyurethane low-temperature heat-curing structural adhesive and a preparation method thereof. In parts by weight, every 100 parts of the one-component polyurethane low-temperature heat-curing structural adhesive comprises: 25 to 45 parts of terminal hydroxyl prepolymer, 10 to 20 parts of blocked diisocyanate curing agent, 25 to 40 parts of inorganic filler, 10 to 20 parts of plasticizer, 0.1 to 1 part of tackifying aid, and 0.1 to 1.5 parts of thermosensitive catalyst. The one-component polyurethane low-temperature heat-curing structural adhesive provided by the present application has the characteristics of long opening time, high storage stability, and low curing temperature, and the performance after curing can be adjusted by the design of the terminal hydroxyl prepolymer. The present invention can be applied to the bonding field of various materials, and the operation process is simple and the curing speed is fast.

Description

Technical Field

[0001] The present application relates to the technical field of single-component polyurethane structural adhesives, and in particular to a single-component polyurethane low-temperature heat-curing structural adhesive and a preparation method thereof. Background Art

[0002] With the development of the new energy vehicle industry, battery technology is also constantly improving, and the traditional CMP structure is gradually changing to a more advanced CTP / CTC structure. In the patent (CN210040322U) applied by CATL in 2020, the connection between the insulating component and the cylindrical battery cell is achieved through structural adhesive; in the patent (CN110165118B) applied by BYD in 2019, the single cells in the battery array are also bonded by structural adhesive to save space, reduce other structural parts to meet lightweight requirements, and improve energy density and production efficiency.

[0003] At present, the most widely used structural adhesives in the market include epoxy structural adhesives and polyurethane structural adhesives. Although epoxy structural adhesives may achieve higher bonding strength, they have poor toughness and are difficult to cope with various vibration and bumpy environments. Therefore, polyurethane structural adhesives are widely used in the power battery industry. Polyurethane structural adhesives are divided into single-component and two-component. Two-component polyurethane structural adhesives usually cure faster and have higher strength, but the operation process is more complicated and there is a risk of uneven mixing of the two components.

[0004] Traditional one-component polyurethane structural adhesives have the disadvantages of slow curing speed, short opening time and poor storage stability. Therefore, the current development direction of one-component polyurethane structural adhesives is high-temperature curing. For example, 4,4'-diphenylamine methane blocked with sodium chloride is used. The thermosetting adhesive achieved in this way can still react with moisture in the air to produce cross-linking, and the opening time can only be extended within a limited range. There is another type of thermosetting polyurethane adhesive, which does not contain isocyanate structure in its composition. It achieves cross-linking and curing by utilizing the principle that bicyclic urea compounds generate diisocyanates after heating, and the required reaction temperature is relatively high.

[0005] It can be seen that the thermosetting single-component polyurethanes currently available on the market usually have the disadvantages of high thermal curing temperature, low strength after curing, poor storage stability, etc., and are difficult to be used for continuous and rapid structural bonding needs. Summary of the invention

[0006] The embodiment of the present application provides a one-component polyurethane low-temperature heat-curing structural adhesive and a preparation method thereof, so as to solve the problems of slow curing speed, high curing temperature, short opening time, poor storage stability, and low curing strength and toughness of the one-component polyurethane low-temperature heat-curing structural adhesive in the related art.

[0007] The technical solutions provided by this application are as follows:

[0008] In a first aspect, the present application provides a one-component polyurethane low-temperature heat-curing structural adhesive, in parts by weight, where every 100 parts of the one-component polyurethane low-temperature heat-curing structural adhesive comprises:

[0009] 25-45 parts of terminal hydroxyl prepolymer, 10-20 parts of blocked diisocyanate curing agent, 25-40 parts of inorganic filler, 10-20 parts of plasticizer, 0.1-1 part of viscosity-increasing aid, and 0.1-1.5 parts of thermal catalyst.

[0010] In some embodiments, the blocked diisocyanate curing agent contains an isocyanate group blocked by a blocking agent, and the blocking agent includes one or more of 3,3′-dichloro-4,4′-diphenylmethanediamine, 3,5-diethyltoluenediamine, 4,4′-methylenebis(2,6-diethyl)aniline, and 4,4′-diaminodiphenylmethane.

[0011] In some embodiments, the hydroxyl-terminated prepolymer is prepared by reacting a polyol and a polyisocyanate in a weight ratio of 1 to 10:1, and the hydroxyl value of the hydroxyl-terminated prepolymer is 20 to 100 mg KOH / g and its viscosity at 25° C. is 30,000 to 100,000 mPa·s.

[0012] In some embodiments, the polyol includes one or more of polyester polyol, polyether polyol, polyolefin polyol, bio-based polyol, 1,3-propylene glycol, and 1,6-hexanediol.

[0013] In some embodiments, the polyisocyanate includes one or more of toluene diisocyanate, diphenylmethane diisocyanate, isophorone diisocyanate, polymethylene polyphenyl polyisocyanate, methylcyclohexyl diisocyanate, and dimethyl diphenylmethane diisocyanate.

[0014] In some embodiments, the thermosensitive catalyst comprises a thermosensitive organometallic catalyst.

[0015] In some embodiments, the inorganic filler includes one or more of light calcium carbonate, nano calcium carbonate, calcium oxide, and fumed silica.

[0016] In some embodiments, the plasticizer includes one or more of dioctyl phthalate, dibutyl phthalate, diisononyl phthalate, dioctyl adipate, diethyl adipate, and glycol benzoate.

[0017] In some embodiments, the adhesion promoter includes one or more of epoxy modified adhesion promoter, 3-aminopropyltriethoxysilane, 3-aminopropyltrimethoxysilane, and N-(2-aminoethyl)-3-aminopropyltrimethoxysilane.

[0018] In a second aspect, the present application provides a method for preparing the one-component polyurethane low-temperature heat-curing structural adhesive as described above, comprising the following steps:

[0019] Add blocked diisocyanate curing agent, inorganic filler, plasticizer, tackifier and thermosensitive catalyst to the terminal hydroxyl prepolymer, stir in vacuum, and react at below 40° C. for 2 to 3 hours to obtain a single-component polyurethane low-temperature heat-curing structural adhesive.

[0020] The beneficial effects of the technical solution provided by this application include:

[0021] (1) By using a blocked diisocyanate curing agent with blocked isocyanate groups in combination with a thermosensitive catalyst, the one-component polyurethane is rendered inactive at room temperature, having a longer opening time and better storage stability. The blocked diisocyanate can be unblocked at about 80°C, having the advantage of a low curing temperature. The thermosensitive catalyst then increases the crosslinking reaction activity and allows for rapid curing.

[0022] (2) The balance between strength and toughness in structural adhesives can be achieved through the design of hydroxyl-terminated prepolymers, and different performance requirements for structural adhesives in actual production can be met through different selections of prepolymer monomers;

[0023] (3) The use of terminal hydroxyl prepolymers does not require the addition of dehydrating agents during the glue making process. The requirements for moisture control in raw materials and process are not as strict as those for traditional moisture-curing polyurethanes, which reduces production costs and can be used in the fields of bonding and sealing of new energy, power batteries, and industrial buses. DETAILED DESCRIPTION

[0024] In order to make the purpose, technical scheme and advantages of the embodiments of the present application clearer, the technical scheme in the embodiments of the present application will be clearly and completely described below in combination with the embodiments of the present application. Obviously, the described embodiments are part of the embodiments of the present application, not all of the embodiments. Based on the embodiments in the present application, all other embodiments obtained by ordinary technicians in this field without making creative work are within the scope of protection of this application.

[0025] In a first aspect, an embodiment of the present application provides a one-component polyurethane low-temperature heat-curing structural adhesive, in parts by weight, where every 100 parts of the one-component polyurethane low-temperature heat-curing structural adhesive comprises:

[0026] 25-45 parts of terminal hydroxyl prepolymer, 10-20 parts of blocked diisocyanate curing agent, 25-40 parts of inorganic filler, 10-20 parts of plasticizer, 0.1-1 part of viscosity-increasing aid, and 0.1-1.5 parts of thermal catalyst.

[0027] The blocked diisocyanate curing agent is formed by the reaction of diisocyanate and a blocking agent. When exposed to the heating temperature of thermal curing, the blocking agent dissociates from the blocked isocyanate group and the isocyanate group is regenerated. Therefore, the blocked diisocyanate curing agent at room temperature does not have a reactive isocyanate group. The thermosensitive catalyst will only play a catalytic role after the temperature reaches a certain value. Therefore, no cross-linking reaction will occur at room temperature, and it has a longer opening time and storage stability.

[0028] In some embodiments, the blocked diisocyanate curing agent contains an isocyanate group blocked by a blocking agent, and the blocking agent includes one or more of 3,3′-dichloro-4,4′-diphenylmethanediamine, 3,5-diethyltoluenediamine, 4,4′-methylenebis(2,6-diethyl)aniline, and 4,4′-diaminodiphenylmethane.

[0029] The blocked diisocyanate curing agent provided in the present application can be unblocked at a low temperature of 80° C., so that the structural adhesive of the present application can be cured at a relatively low temperature.

[0030] Furthermore, it is preferred that the mass proportion of isocyanate in the blocked diisocyanate curing agent is 6 to 10 wt %.

[0031] In some embodiments, the hydroxyl-terminated prepolymer is prepared by reacting a polyol and a polyisocyanate in a weight ratio of 1 to 10:1, and the hydroxyl-terminated prepolymer has a hydroxyl value of 20 to 100 mg KOH / g and a viscosity of 30,000 to 100,000 mPa·s at 25°C.

[0032] In a preferred embodiment, the hydroxyl-terminated prepolymer is prepared by reacting a polyol and a polyisocyanate in a weight ratio of 1 to 3:1.

[0033] The hydroxyl-terminated prepolymer provided in the present application can meet different performance requirements for structural adhesives in actual production by selecting different combinations of polyols and isocyanates.

[0034] In some embodiments, the polyol includes one or more of polyester polyol, polyether polyol, polyolefin polyol, bio-based polyol, polycaprolactone polyol, 1,3-propylene glycol, 1,6-hexanediol.

[0035] In some embodiments, the polyisocyanate includes one or more of toluene diisocyanate, diphenylmethane diisocyanate, isophorone diisocyanate, polymethylene polyphenyl polyisocyanate, methylcyclohexyl diisocyanate, and dimethyl diphenylmethane diisocyanate.

[0036] Specifically, the preparation method of the hydroxyl-terminated prepolymer may include the following steps:

[0037] After vacuum dehydration of the polyol at 110-120°C for 1-1.5 hours, cool to 60°C, add isocyanate in 3-5 portions while maintaining high-speed stirring, stabilize the temperature at 60-80°C and react for 1-2 hours. The isocyanate content in the reactant is detected to be less than 0.1wt%, to obtain a terminal hydroxyl prepolymer.

[0038] In some embodiments, the thermosensitive catalyst comprises a thermosensitive organometallic catalyst.

[0039] Furthermore, it is preferred that the thermosensitive catalyst is a hydrolysis-resistant environmentally friendly organic metal catalyst, including but not limited to: an organic tin catalyst, an organic bismuth catalyst, a titanate catalyst and their composite products.

[0040] In a preferred embodiment, the one-component polyurethane low-temperature heat-curing structural adhesive further includes a non-heat-sensitive catalyst, for example, including but not limited to an organic tin catalyst and a tertiary amine catalyst.

[0041] By adding a conventional non-thermosensitive catalyst, the internal components of the structural adhesive react slowly, releasing heat, and the colloid temperature gradually rises, and this time is used to complete the gluing process; when the temperature rises to the threshold of the thermosensitive catalyst, the thermosensitive catalyst takes effect, causing the components to cure quickly, thereby achieving the purpose of rapid bonding.

[0042] In some embodiments, the inorganic filler includes one or more of light calcium carbonate, nano calcium carbonate, calcium oxide, and fumed silica.

[0043] In some embodiments, the plasticizer includes one or more of dioctyl phthalate, dibutyl phthalate, diisononyl phthalate, dioctyl adipate, diethyl adipate, and glycol benzoate.

[0044] In some embodiments, the adhesion promoter includes one or more of epoxy modified adhesion promoter, 3-aminopropyltriethoxysilane, 3-aminopropyltrimethoxysilane, and N-(2-aminoethyl)-3-aminopropyltrimethoxysilane.

[0045] In a second aspect, the present application also provides a method for preparing the one-component polyurethane low-temperature heat-curing structural adhesive as described above, comprising the following steps:

[0046] Add blocked diisocyanate curing agent, inorganic filler, plasticizer, tackifier and thermosensitive catalyst to the terminal hydroxyl prepolymer, stir in vacuum, and react at below 40° C. for 2 to 3 hours to obtain a single-component polyurethane low-temperature heat-curing structural adhesive.

[0047] The present application is further described below through specific examples.

[0048] The epoxy modified adhesion promoter used in the following examples and comparative examples is a JSC series product produced by Hangzhou Jessica Chemical Co., Ltd.

[0049] Example 1

[0050] This embodiment provides a one-component polyurethane low-temperature heat-curing structural adhesive and a preparation method thereof.

[0051] 1. Preparation of hydroxyl-terminated prepolymer

[0052] Prepare the raw materials according to the following ratio:

[0053]

[0054] 57 parts by weight of bisphenol A type polyether diol (bisphenol A type EO / PO copolymer polyether diol, molecular weight of 400, hydroxyl value of 280 mg KOH / g) and 15 parts by weight of diisononyl phthalate are added to a synthesis reaction kettle, heated to 120° C. and then vacuum-dehydrated for 30 minutes, cooled to 60° C. and then 28 parts by weight of diphenylmethane diisocyanate are added three times, mixed, heated to 70-75° C., and kept warm for 3 hours, during which the viscosity and isocyanate content are detected at regular intervals; when the measured viscosity is 33000±1000 mPa·s (25° C.) and the isocyanate group-NCO content is less than 0.1wt%, vacuum degassing is started, and the synthesis reaction is terminated after degassing for 10 minutes to obtain a hydroxyl-terminated prepolymer A having a hydroxyl value of 34.59 mg KOH / g;

[0055] 2. Preparation of one-component polyurethane low-temperature heat-curing structural adhesive

[0056] Prepare the raw materials according to the following ratio:

[0057]

[0058] 33 parts by weight of terminal hydroxyl prepolymer A, 17 parts by weight of blocked diisocyanate curing agent (the blocking agent is methyl ethyl ketoxime), 28.8 parts by weight of heavy calcium carbonate, 18 parts by weight of dioctyl phthalate, 0.2 parts by weight of epoxy modified adhesion promoter, 2 parts by weight of hydrophobic fumed silica, and 1 part by weight of thermosensitive catalyst (diisononyl phthalate is diluted to a concentration of 10%) are added to a planetary stirring mixer, and stirred for 1 hour under vacuum. During stirring, the kettle temperature is controlled between 10-20°C by a water-type mold temperature controller. When the reaction is completed, a one-component polyurethane low-temperature heat-curing structural adhesive with a solid content of 100 parts by weight is obtained.

[0059] Example 2

[0060] This embodiment provides a one-component polyurethane low-temperature heat-curing structural adhesive and a preparation method thereof.

[0061] 1. Preparation of hydroxyl-terminated prepolymer

[0062] Prepare the raw materials according to the following ratio:

[0063]

[0064] 52 parts by weight of polyoxypropylene-ethylene oxide copolymer polyol (molecular weight: 5000, hydroxyl value: 34), 22 parts by weight of castor oil derivative triol (Vertellus Company, USA, brand: T-400), and 8 parts by weight of diisononyl phthalate are added to a synthesis reaction kettle, heated to 120° C. and then vacuum-dehydrated for 30 minutes, cooled to 60° C. and then 18 parts by weight of diphenylmethane diisocyanate are added three times, mixed, heated to 70-75° C., and kept warm for reaction for 3 hours, during which the viscosity and isocyanate content are detected at regular intervals; when the measured viscosity is 31000±1000mPa·s (25° C.) and the isocyanate group-NCO content is less than 0.1wt%, vacuum degassing is started, and the synthesis reaction is terminated after degassing for 10 minutes to obtain a hydroxyl-terminated prepolymer B with a hydroxyl value of 29.72mg KOH / g;

[0065] 2. Preparation of one-component polyurethane low-temperature heat-curing structural adhesive

[0066] Prepare the raw materials according to the following ratio:

[0067]

[0068]

[0069] 34.5 parts by weight of terminal hydroxyl prepolymer B, 15.5 parts by weight of blocked diisocyanate curing agent (the blocking agent is methyl ethyl ketoxime), 33.8 parts by weight of heavy calcium carbonate, 15 parts by weight of diisononyl phthalate, 0.2 parts by weight of epoxy modified adhesion promoter, 2 parts by weight of hydrophobic fumed silica, and 1 part by weight of a thermosensitive catalyst (10%) are added to a planetary stirring mixer and stirred for 1 hour under vacuum. During stirring, the kettle temperature is controlled between 10 and 20° C. by a water-type mold temperature controller. When the reaction is completed, a one-component polyurethane low-temperature heat-curing structural adhesive with a solid content of 100 parts by weight is obtained.

[0070] Example 3

[0071] This embodiment provides a one-component polyurethane low-temperature heat-curing structural adhesive and a preparation method thereof.

[0072] 1. Preparation of hydroxyl-terminated prepolymer

[0073] Prepare the raw materials according to the following ratio:

[0074]

[0075] 69 parts by weight of polyoxypropylene-ethylene oxide copolymer polyol (molecular weight: 5000, hydroxyl value: 34), 10 parts by weight of poly-ε-lactone polyester diol (molecular weight: 400, hydroxyl value: 280), and 13 parts by weight of diisononyl phthalate are added to a synthesis reaction kettle, heated to 120° C. and then vacuum-dehydrated for 30 minutes, cooled to 60° C. and then 6 parts by weight of diphenylmethane diisocyanate are added three times, mixed, heated to 70-75° C., and kept warm for reaction for 3 hours, during which the viscosity and isocyanate content are detected at regular intervals; when the measured viscosity is 38000±1000mPa·s (25° C.) and the isocyanate group-NCO content is less than 0.1wt%, vacuum degassing is started, and the synthesis reaction is terminated after degassing for 10 minutes to obtain a hydroxyl-terminated prepolymer C having a hydroxyl value of 24.67mg KOH / g;

[0076] 2. Preparation of one-component polyurethane low-temperature heat-curing structural adhesive

[0077] Prepare the raw materials according to the following ratio:

[0078]

[0079] 36 parts by weight of terminal hydroxyl prepolymer C, 12.8 parts by weight of blocked diisocyanate curing agent (the blocking agent is methyl ethyl ketoxime), 33 parts by weight of nano calcium carbonate, 17 parts by weight of diisononyl phthalate, 0.2 parts by weight of epoxy modified adhesion promoter, and 1 part by weight of thermosensitive catalyst (10%) are added into a planetary stirring mixer, and stirred for 1 hour under vacuum. During stirring, the kettle temperature is controlled between 10-20° C. by a water-type mold temperature controller. When the reaction is completed, a one-component polyurethane low-temperature heat-curing structural adhesive with a solid content of 100 parts by weight is obtained.

[0080] Example 4

[0081] This embodiment provides a one-component polyurethane low-temperature heat-curing structural adhesive.

[0082] It includes most of the operating steps of Example 1, except that the hydroxyl-terminated prepolymer is prepared as follows:

[0083]

[0084] Example 5

[0085] This embodiment provides a one-component polyurethane low-temperature heat-curing structural adhesive.

[0086] It includes most of the operating steps of Example 1, except that the hydroxyl-terminated prepolymer is prepared as follows:

[0087]

[0088] Comparative Example 1

[0089] This comparative example provides a one-component polyurethane heat-curing structural adhesive.

[0090] The method includes most of the operation steps of Example 1, with the only difference being that the raw material of the one-component polyurethane heat-curing structural adhesive does not include a blocked diisocyanate curing agent, but uses diphenylmethane diisocyanate as a substitute.

[0091] Comparative Example 2

[0092] This comparative example provides a one-component polyurethane heat-curing structural adhesive.

[0093] The method includes most of the operation steps of Example 1, with the only difference being that the blocking agent in the blocked diisocyanate curing agent is caprolactam.

[0094] Comparative Example 3

[0095] This comparative example provides a one-component polyurethane heat-curing structural adhesive.

[0096] It includes most of the steps of Example 1, except that:

[0097] The weight portion of the blocked diisocyanate curing agent is 5 parts.

[0098] Comparative Example 4

[0099] This comparative example provides a one-component polyurethane heat-curing structural adhesive.

[0100] It includes most of the steps of Example 1, except that:

[0101] The weight portion of the blocked diisocyanate curing agent is 25 parts.

[0102] Performance Testing

[0103] The following performance tests were performed on the one-component polyurethane heat-curing structural adhesives prepared in Examples 1-5 and Comparative Examples 1-4.

[0104] Operation time: refer to the viscosity method in GB / T-7123.1, the test temperature is 23±2℃, the humidity is 50±5% RH;

[0105] Bond strength: Use and test at 23±2℃. The bond strength of the performance test is the room temperature shear strength. The bonding method is aluminum-aluminum bonding. The solid conditions are: curing at 90℃ for 30min or 160℃ for 60min. The sample curing method refers to the curing method of the 23℃ test sample in JC / T-2560.

[0106] Damage type: Described in accordance with the provisions of GB / T-16997;

[0107] Storage stability: Place the structural adhesive together with the packaging in a 60°C oven for 7 days. Test the viscosity of the structural adhesive before and after placement. The storage stability value is the ratio of the viscosity after placement to the viscosity before placement. The viscosity test method refers to GB / T-2794. The speed is set to 10rpm and the reading is taken when the torque is adjusted to 40-60%.

[0108] Table 1 Performance test results of one-component polyurethane heat-curing structural adhesive

[0109]

[0110] Among them, C-1 represents cohesive failure and A-1 represents interfacial failure.

[0111] From the performance test results of the one-component polyurethane low-temperature heat-curing structural adhesives prepared in Examples 1 to 5 shown in Table 1, it can be seen that:

[0112] 1. The one-component polyurethane low-temperature heat-curing structural adhesive prepared in Examples 1 to 3 is not cured after being opened for more than 18 hours at room temperature, and has important value in practical applications; however, if the polyol content in the terminal hydroxyl prepolymer is too low, the operation time will be shortened (Examples 4 and 5), which may be related to the reduction of the molecular weight of the terminal hydroxyl prepolymer;

[0113] 2. The one-component polyurethane low-temperature heat-curing structural adhesive prepared in Examples 1 to 3: The shear strength of more than 6 MPa can be achieved by curing at 90°C for 30 minutes. After the prepolymer is modified by introducing castor oil polyol or caprolactone, the shear strength can reach more than 7.5 MPa; or the shear strength of the modified formula can reach more than 8.5 MPa by curing at 160°C*60 minutes. The failure form of all the shear specimens described above is 100% cohesive failure;

[0114] 3. The one-component polyurethane low-temperature heat-curing structural adhesive prepared in Examples 1 to 3 was verified under accelerated aging conditions at 60°C. The viscosity increased by no more than 10% after being placed for 7 days, indicating that the product has excellent storage stability; after the blocked diisocyanate curing agent was replaced with diphenylmethane diisocyanate (Comparative Example 1), or the proportion of the blocked diisocyanate curing agent was increased (Comparative Examples 3 and 4), the storage stability was significantly deteriorated; after the blocking agent of the blocked diisocyanate curing agent was replaced with caprolactam (Comparative Example 2), the adhesive was basically not cured at 90°C and was not completely cured at 160°C.

[0115] In summary, the present invention prepares a polyurethane structural adhesive that can be quickly cured under low temperature conditions, has good viscosity for aluminum substrates, and is resistant to storage and can be used without being affected after being opened for a long time.

[0116] The above description is only a specific implementation of the present application, so that those skilled in the art can understand or implement the present application. Various modifications to these embodiments will be apparent to those skilled in the art, and the general principles defined herein can be implemented in other embodiments without departing from the spirit or scope of the present application. Therefore, the present application will not be limited to the embodiments shown herein, but will conform to the widest range consistent with the principles and novel features applied for herein.

Claims

1. A one-component polyurethane low-temperature heat-curing structural adhesive, characterized in that: In parts by weight, every 100 parts of the one-component polyurethane low-temperature heat-curing structural adhesive is composed of 33 parts of terminal hydroxyl prepolymer A, 17 parts of blocked diisocyanate curing agent, 28.8 parts of heavy calcium carbonate, 18 parts of dioctyl phthalate, 0.2 parts of epoxy modified adhesion promoter, 2 parts of hydrophobic fumed silica, and 1 part of thermal catalyst; The blocking agent of the blocked diisocyanate curing agent is methyl ethyl ketoxime; The hydroxyl-terminated prepolymer A is prepared by reacting 57 parts of bisphenol A type polyether diol, 28 parts of diphenylmethane diisocyanate, and 15 parts of diisononyl phthalate, wherein the hydroxyl value of the hydroxyl-terminated prepolymer A is 34.59 mg KOH / g, and the viscosity at 25° C. is 33000±1000 mPa·s; The one-component polyurethane low-temperature heat-curing structural adhesive is prepared by the following preparation method: 33 parts by weight of terminal hydroxyl prepolymer A, 17 parts by weight of blocked diisocyanate curing agent, 28.8 parts by weight of heavy calcium carbonate, 18 parts by weight of dioctyl phthalate, 0.2 parts by weight of epoxy modified adhesion promoter, 2 parts by weight of hydrophobic fumed silica, and 1 part by weight of thermosensitive catalyst are added into a planetary stirring mixer, and stirred for 1 hour under vacuum state, and the kettle temperature is controlled between 10-20° C. by a water-type mold temperature controller during stirring to obtain the one-component polyurethane low-temperature heat-curing structural adhesive.

2. The one-component polyurethane low-temperature heat-curing structural adhesive according to claim 1, characterized in that: The thermosensitive catalyst includes a thermosensitive organometallic catalyst.

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