Bi-component polyurethane structural adhesive as well as preparation method and application thereof

Abstract

The invention belongs to the technical field of binders, and relates to a two-component polyurethane structural adhesive as well as a preparation method and application thereof. The bi-component polyurethane structural adhesive comprises a component A and a component B, the component A comprises modified castor oil, bio-based polyol, a chain extender, a dewatering agent, a filler, a silane coupling agent, an anti-aging agent, a catalyst A and a catalyst B; the component B comprises polyisocyanate, a polyisocyanate polymer, a curing agent, a dewatering agent, fumed silica, a silane coupling agent and a plasticizer; the preparation method of the catalyst A comprises the following steps: mixing a sulfydryl-containing organic compound and an organic bismuth compound under an acidic condition, and carrying out a coordination reaction to obtain the catalyst A; the catalyst B comprises an organic metal compound. The structural adhesive disclosed by the invention can be quickly cured for 120-240 seconds at the temperature of 60-80 DEG C; the viscosity change rate is less than 20% after the structural adhesive in the mixing pipe is stood for 1 hour at room temperature.

Description

Technical Field

[0001] This invention belongs to the field of adhesive technology, and particularly relates to a two-component polyurethane structural adhesive, its preparation method, and its application. Background Technology

[0002] With the growing demand for lightweight vehicles, replacing steel with plastics in vehicle design has become a trend. The bonding of components such as door panels, lower door trim panels, spoilers, front and rear bulkheads, and plastic tailgates typically uses two-component polyurethane (PU) adhesives, which can withstand significant dynamic and static loads. With the substantial increase in automobile production, these component manufacturers mostly adopt hot-pressing processes to shorten processing time and increase yield. Hot-pressing requires ensuring rapid curing of the structural adhesive at 60-80℃ while maintaining smooth application. Generally, after passing through the mixing tube and standing at room temperature for 1 hour, the viscosity of the structural adhesive should increase by less than 20%.

[0003] Hot pressing is a process used in the automotive and furniture industries to bond exterior door panels together through hot pressing and bonding. Under specific temperature, pressure, and time conditions, hot pressing allows the adhesive to fully cure and the materials to bond tightly. The pressure should be adjusted according to factors such as the material's thickness and hardness, generally between 0.5 MPa and 5 MPa; the hot pressing time is typically between 60 s and 180 s, with the specific time needing to be determined experimentally based on actual conditions.

[0004] CN110114380A discloses a two-component polyurethane adhesive based on polyol component A and polyisocyanate component B. This adhesive is prepared by compounding polyetheramine with a catalyst containing Sn or Bi catalyst. While it exhibits rapid curing speed, good adhesion properties, and good durability, its short open time is unsuitable for practical applications, necessitating frequent replacement of the mixing tube. CN111704885A discloses a fast-curing two-component polyurethane structural adhesive, its preparation method, and its application. This fast-curing two-component polyurethane structural adhesive has an operating time of 10-15 min, a hot-pressing time of 10 min, and a strength of 2.0-3.0 MPa. However, its open time is too short, and its hot-pressing time is too long.

[0005] Existing technologies suffer from the drawback of being unable to simultaneously achieve high curing speed and low viscosity change rate in structural adhesives. They cannot meet the requirement of rapid curing at 60-80℃ for 120-240 seconds, and a viscosity change rate of less than 20% after standing at room temperature for 1 hour. Therefore, developing a two-component polyurethane structural adhesive that combines high curing speed and low viscosity change rate has become an urgent problem to be solved. Summary of the Invention

[0006] To address the aforementioned technical problems, the present invention aims to provide a two-component polyurethane structural adhesive, its preparation method, and its applications. The two-component polyurethane structural adhesive of the present invention can achieve rapid high-temperature curing while maintaining a low viscosity change rate. Even after aging, the structural adhesive exhibits excellent shear strength and adhesive properties. The structural adhesive of the present invention meets the requirements of hot-pressing processes, provides smooth application, and eliminates the need for frequent replacement of the mixing tube.

[0007] To achieve this objective, the present invention adopts the following technical solution:

[0008] In a first aspect, the present invention provides a two-component polyurethane structural adhesive, the two-component polyurethane structural adhesive comprising component A and component B; component A comprising modified castor oil, bio-based polyol, chain extender, dehydrating agent, filler, silane coupling agent, anti-aging agent, catalyst A and catalyst B; component B comprising polyisocyanate, polyisocyanate polymer, curing agent, dehydrating agent, fumed silica, silane coupling agent and plasticizer; catalyst A is a coordination compound formed by a mercapto-containing organic compound and an organobismuth compound; catalyst B comprises an organometallic compound.

[0009] In this invention, by selecting a combination of catalyst A and catalyst B, rapid high-temperature curing is achieved while maintaining a low viscosity change rate. The structural adhesive of this invention also exhibits excellent shear, tensile, and adhesive properties. The principle is as follows: Catalyst A constructs a thermally reversible "dormant-activated" cycle. At room temperature, it is in a dormant state, with the highly efficient bismuth catalyst "locked" in inactive bismuth thiolate, preventing the major reaction between isocyanate (-NCO) and polyol (-OH), thus achieving a low viscosity change rate. At high temperatures, it undergoes reversible decomposition, re-releasing the active organic bismuth catalyst, which, combined with catalyst B, achieves rapid curing.

[0010] In this invention, if a silane coupling agent is not added, the shear strength, tensile strength, and interfacial adhesion of the structural adhesive will all deteriorate.

[0011] Preferably, component A comprises the following components in parts by weight: 15-30 parts modified castor oil, 30-40 parts bio-based polyol, 5-10 parts chain extender, 1-3 parts dehydrating agent, 20-35 parts filler, 0.5-2.5 parts silane coupling agent, 1-3 parts anti-aging agent, 1-5 parts catalyst A, and 0.1-1 parts catalyst B.

[0012] The modified castor oil may be present in parts by weight, for example, 18, 20, 23, 25, or 28 parts.

[0013] The weight percentages of the bio-based polyol may be, for example, 32, 34, 35, 36, or 38 parts.

[0014] The chain extender may be present in, for example, 6, 7, 8, or 9 parts by weight.

[0015] The weight percentage of the dehydrating agent can be, for example, 1.5 parts, 1.8 parts, 2 parts, 2.5 parts, or 2.8 parts.

[0016] The weight percentage of the filler can be, for example, 22 parts, 25 parts, 28 parts, 30 parts, or 32 parts.

[0017] The weight percentage of the silane coupling agent can be, for example, 0.8 parts, 1 part, 1.5 parts, 2 parts, or 2.3 parts.

[0018] The weight percentage of the anti-aging agent can be, for example, 1.5 parts, 1.8 parts, 2 parts, 2.5 parts, or 2.8 parts.

[0019] The catalyst A may be present in parts by weight, for example, 2 parts, 2.5 parts, 3 parts, 3.5 parts, or 4 parts.

[0020] The catalyst B can be present in parts by weight, for example, 0.2 parts, 0.4 parts, 0.5 parts, 0.6 parts, or 0.8 parts.

[0021] In this invention, both excessive and insufficient use of the silane coupling agent will cause a decrease in shear strength and tensile strength. Excessive use of catalyst B will increase the viscosity change rate.

[0022] Preferably, the modified castor oil includes any one or a combination of at least two of the following: Ito H-368 modified castor oil, Ito AC-009 modified castor oil, Ito AC-006 modified castor oil, Ito URICH-1830, URICH-1824, Vantrus T-400, or M-365 modified castor oil.

[0023] Preferably, the bio-based polyol includes any one or a combination of at least two of Sovermol805, Sovermol815, Sovermol819, Korean SKECOPROL H2000, or Korean SKECOPROL H1000.

[0024] Preferably, the chain extender comprises any one or a combination of at least two of ethylene glycol, butanediol, propylene glycol, glycerol, dipropylene glycol, 1,4-butanediol, 1,6-hexanediol, or 2-ethyl-1,3-hexanediol.

[0025] Preferably, the dehydrating agent in component A includes any one or a combination of at least two of calcium oxide, molecular sieve, or p-toluenesulfonate isocyanate.

[0026] Preferably, the filler comprises any one or a combination of at least two of kaolin, nano-calcium carbonate, light calcium carbonate, or talc.

[0027] Preferably, the silane coupling agent in component A comprises any one or a combination of at least two of γ-glycidyl etheroxypropylmethyltrimethoxysilane, γ-mercaptopropyltrimethoxysilane, γ-mercaptopropyltriethoxysilane, γ-aminopropyltrimethoxysilane, γ-aminopropyltriethoxysilane, aminoethylmethyltrimethoxysilane, anilinepropyltrimethoxysilane, 3-methacryloyloxypropyltrimethoxysilane, or thiosilicic acid, O,O,O-triethyl-thio-[3-(triethoxysilyl)propyl] ester.

[0028] Preferably, the anti-aging agent includes any one or a combination of at least two of the following: antioxidant TP-10H, antioxidant 1076, antioxidant 245, antioxidant Irgafos168, antioxidant 1010, BASF TINUVIN 292, TINUVIN770DF, TINUVIN326, TINUVIN P, or TINUVIN622.

[0029] Preferably, the thiol-containing organic compound includes any one or a combination of at least two of bis(3-mercaptopropionic acid) ethylene glycol, pentaerythritol tetrakis(3-mercaptopropionic acid) ester or trimethylolpropane tri(3-mercaptopropionic acid) ester.

[0030] Preferably, the molar ratio of -SH in the thiol-containing organic compound to Bi in the organobismubium compound is (15-26):1, for example, it can be 16:1, 18:1, 20:1, 22:1, 24:1 or 25:1, etc.

[0031] In this invention, the molar ratio of -SH in the thiol-containing organic compound to Bi in the organic bismuth compound is simply referred to as the -SH:Bi ratio. Controlling the -SH:Bi ratio within a specific range can further improve the tensile strength and shear strength of the structural adhesive and reduce the viscosity change rate.

[0032] Preferably, the preparation method of catalyst A includes the following steps:

[0033] A thiol-containing organic compound and an organobismuth compound are mixed under acidic conditions to carry out a coordination reaction, thereby obtaining catalyst A.

[0034] Preferably, the coordination reaction is carried out under vacuum.

[0035] Preferably, the acidity is a weak acid.

[0036] In this invention, the reaction is carried out under weakly acidic conditions, which on the one hand can improve the reaction efficiency; on the other hand, it helps to reduce the viscosity change rate of the polyurethane structural adhesive.

[0037] Preferably, the preparation method of catalyst A includes the following steps:

[0038] (1) Mix the thiol-containing organic compound with the organobismuth compound, heat to the first temperature, and stir;

[0039] (2) Cool to the second temperature, add additives, stir, and obtain catalyst A.

[0040] Preferably, the first temperature is 70-80°C, for example, it can be 72°C, 74°C, 75°C, 76°C or 78°C.

[0041] Preferably, the stirring time in step (1) is 2-3 h, for example, it can be 2.2 h, 2.4 h, 2.5 h, 2.6 h or 2.8 h.

[0042] Preferably, the second temperature is 40-50°C, for example, it can be 42°C, 44°C, 45°C, 46°C or 48°C, etc.

[0043] Preferably, the stirring time in step (2) is 0.8-1.2 h, for example, it can be 0.85 h, 0.9 h, 0.95 h, 1 h or 1.1 h.

[0044] Preferably, the additive is a mixture of alkyl sulfonate phenyl ester and phosphoric acid.

[0045] Preferably, the mass content of phosphoric acid in the mixture of alkyl sulfonate phenyl ester and phosphoric acid is 0.01%-0.05%, for example, it can be 0.02%, 0.025%, 0.03%, 0.035% or 0.04%, etc.

[0046] Preferably, the alkyl sulfonate phenyl ester comprises Lanxess Chemical alkyl sulfonate phenyl ester MESAMOLL.

[0047] Preferably, the catalyst B comprises any one or a combination of at least two of the following: dibutyltin dichloride, dibutyltin dilaurate, stannous octoate, dibutyltin diacetate, or the Polycat SA series of thermosensitive catalysts.

[0048] Preferably, component A further includes 1-10 parts of toughening resin, for example, 2 parts, 4 parts, 5 parts, 6 parts or 8 parts, etc.

[0049] In this invention, adding toughening resin to component A can further improve tensile strength, especially tensile strength after aging.

[0050] Preferably, the toughening resin comprises bisphenol A polyoxyethylene ether and / or bisphenol A polyoxypropylene ether.

[0051] Preferably, component B comprises the following components in parts by weight: 15-25 parts of polyisocyanate, 35-55 parts of polyisocyanate polymer, 2-5 parts of curing agent, 0.01-5 parts of dehydrating agent, 1-5 parts of fumed silica, 0.5-2.5 parts of silane coupling agent, and 15-30 parts of plasticizer.

[0052] The weight parts of the polyisocyanate may be, for example, 16 parts, 18 parts, 20 parts, 22 parts, or 24 parts.

[0053] The weight parts of the polyisocyanate polymer can be, for example, 37 parts, 39 parts, 42 parts, 45 parts, 50 parts, or 53 parts.

[0054] The curing agent may be present in parts by weight, for example, 2.5 parts, 3 parts, 3.5 parts, 4 parts, or 4.5 parts.

[0055] The weight percentage of the dehydrating agent can be, for example, 1 part, 2 parts, 3 parts, 4 parts, or 4.5 parts.

[0056] The weight parts of the fumed silica can be, for example, 2 parts, 2.5 parts, 3 parts, 3.5 parts, or 4 parts.

[0057] The weight percentage of the silane coupling agent can be, for example, 1 part, 1.5 parts, 1.8 parts, 2 parts, or 2.3 parts.

[0058] The plasticizer may be present in parts by weight of, for example, 18, 20, 23, 25, or 28 parts.

[0059] In this invention, insufficient use of polyisocyanate leads to decreased interfacial adhesion. Excessive or insufficient use of silane coupling agent results in a decrease in shear strength and tensile strength.

[0060] Preferably, the polyisocyanate includes any one or a combination of at least two of Yantai Wanhua MDI100L, MDI-50, modified MDI8219, PM200, or Huntsman Suprasec® 2647.

[0061] Preferably, the polyisocyanate polymer comprises polyurethane obtained by reacting isocyanate with polyol.

[0062] Preferably, the NCO content of the polyurethane obtained by reacting the isocyanate with the polyol is 10%-15%, for example, it can be 11%, 12%, 13%, 14% or 14.5%, etc.

[0063] Preferably, the curing agent includes any one or a combination of at least two of Wanhua HT200, Wanhua HT100, Covestro Desmodur N3300 or Desmodur N3200.

[0064] Preferably, the dehydrating agent in component B includes any one or a combination of at least two of calcium oxide, molecular sieve, or p-toluenesulfonate isocyanate.

[0065] Preferably, the fumed silica includes any one or a combination of at least two of Wacker H18, Wacker H20, Evonik R974, Evonik R202, or Cabot TS720.

[0066] Preferably, the silane coupling agent in component B comprises any one or a combination of at least two of γ-glycidyl etheroxypropylmethyltrimethoxysilane, γ-mercaptopropyltrimethoxysilane, γ-mercaptopropyltriethoxysilane, γ-aminopropyltrimethoxysilane, γ-aminopropyltriethoxysilane, aminoethylmethyltrimethoxysilane, anilinepropyltrimethoxysilane, 3-methacryloyloxypropyltrimethoxysilane, or thiosilicic acid, O,O,O-triethyl-thio-[3-(triethoxysilyl)propyl] ester.

[0067] Preferably, the plasticizer comprises any one or a combination of at least two of dipropylene glycol dibenzoate, alkyl sulfonate, diisononyl phthalate, diisooctyl phthalate, or diisodecyl phthalate.

[0068] In a second aspect, the present invention provides a method for preparing a two-component polyurethane structural adhesive as described in the first aspect, the method comprising the preparation of component A and component B.

[0069] The preparation of component A includes the following steps: mixing modified castor oil, bio-based polyol, chain extender, dehydrating agent, filler, silane coupling agent, aging agent, catalyst A, catalyst B and optional toughening resin to obtain component A.

[0070] The preparation of component B includes the following steps: mixing polyisocyanate, polyisocyanate polymer, curing agent, dehydrating agent, fumed silica, silane coupling agent and plasticizer to obtain component B.

[0071] Thirdly, the present invention provides a method for using the two-component polyurethane structural adhesive as described in the first aspect, the method comprising the following steps: mixing component A and component B, applying the mixture to the surface of the substrate to be bonded, and curing the mixture to complete the use of the two-component polyurethane structural adhesive.

[0072] Preferably, the volume ratio of component A to component B is (0.9-1.1):1, for example, it can be 0.95:1, 0.98:1, 1:1, 1.02:1 or 1.05:1, etc.

[0073] Fourthly, the present invention provides an application of the two-component polyurethane structural adhesive as described in the first aspect in the bonding of automotive parts.

[0074] Compared with the prior art, the present invention has at least the following beneficial effects:

[0075] The structural adhesive of this invention cures rapidly in 120-240 seconds at a temperature of 60-80°C; the viscosity change rate of the structural adhesive in the mixing tube after standing at room temperature for 1 hour is less than 20%. Detailed Implementation

[0076] To facilitate understanding of the present invention, the following embodiments are provided. Those skilled in the art should understand that these embodiments are merely illustrative and should not be construed as limiting the scope of the invention.

[0077] Information on some of the raw materials used in the following examples.

[0078] The modified castor oil in component A is H-368 modified castor oil selected from Itoh.

[0079] The bio-based polyol in component A is Sovermol 805, selected from BASF.

[0080] The toughening resin bisphenol A polyoxypropylene ether in component A is selected from Royal Madrid Technology HMP604B.

[0081] The chain extender in component A is 2-ethyl-1,3-hexanediol, selected from Jiangsu Runfeng Synthetic Technology Co., Ltd.

[0082] The dehydrating agent in component A is 4A molecular sieve activated powder selected from Suzhou Xiaoyou New Materials Co., Ltd.

[0083] The kaolin used as filler in component A is B-95, selected from Shanxi Jinyu Kelin Technology Co., Ltd.

[0084] The silane coupling agent in component A is 3-methacryloyloxypropyltrimethoxysilane selected from Evonik Degussa.

[0085] Catalyst A in component A is self-made.

[0086] Catalyst B in component A is Polycat SA1, selected from Evonik Degussa.

[0087] The polyisocyanate Suprasec® 2647 in component B is selected from Huntsman.

[0088] The polyisocyanate polymer in component B is self-made.

[0089] The curing agent in component B is Desmodur N3200, selected from Covestro.

[0090] The dehydrating agent in component B is p-toluenesulfonate isocyanate TI, selected from Ark Chemical.

[0091] The fumed silica in component B is R202, selected from Evonik.

[0092] The silane coupling agent in component B is thiosilicic acid, O,O,O-triethyl-thio-[3-(triethoxysilyl)propyl] ester, selected from Shandong Silicon Science.

[0093] The plasticizer in component B is MESAMOLL, an alkyl sulfonate sourced from Lanxess Chemicals (China) Co., Ltd.

[0094] Preparation Example 1

[0095] Preparation of catalyst A1: 366 g of pentaerythritol tetrakis(3-mercaptopropionic acid) and 500 g of organobismuth Bi.-Octoat 8.2 (purchased from Leading Specialty Chemicals, USA, brand name K-KAT® 348) were added to a 2000 mL three-necked flask, heated to 75 °C, and stirred under vacuum for 2.5 h to remove water, then cooled to 45 °C. Then, 2.0 g of a 0.02% (w / w) solution of alkyl sulfonate phenyl phosphate (MESAMOLL) was added, and the mixture was stirred under vacuum for 1 h to remove water, then sealed and stored for later use to obtain catalyst A1.

[0096] Preparation Example 2

[0097] Preparation of catalyst A2: 488 g of pentaerythritol tetrakis(3-mercaptopropionic acid) and 500 g of organobismuth Bi.-Octoat 8.2 were added to a 2000 mL three-necked flask, heated to 75 °C, and stirred under vacuum for 2.5 h to remove water. The mixture was then cooled to 45 °C. Next, 2.3 g of a 0.02% (w / w) solution of alkyl sulfonate phenyl ester (MESAMOLL) of phosphoric acid was added, and the mixture was stirred under vacuum for 1 h to remove water. The solution was then sealed and stored for later use to obtain catalyst A2.

[0098] Preparation Example 3

[0099] Preparation of catalyst A3: 610 g of pentaerythritol tetrakis(3-mercaptopropionic acid) and 500 g of organobismuth Bi.-Octoat 8.2 were added to a 2000 mL three-necked flask, heated to 75 °C, and stirred under vacuum for 2.5 h to remove water, then cooled to 45 °C. Then, 2.6 g of a 0.02% (w / w) solution of alkyl sulfonate phenyl ester (MESAMOLL) of phosphoric acid was added, and the mixture was stirred under vacuum for 1 h to remove water, then sealed and stored for later use to obtain catalyst A3.

[0100] Preparation Example 4

[0101] Preparation of the polyisocyanate polymer: 750 g of polyether polyol C2020 was added to a 2000 mL three-necked flask, heated to 115 °C, and stirred under vacuum for 2.5 hours to remove water. After confirming that the moisture content was less than 200 ppm, the temperature was lowered to 60 °C and 600 g of isocyanate Suprasec® 2647 was added. The mixture was heated to 80 °C and reacted for 3 hours to obtain a polyisocyanate polymer with an NCO content of 11.8%. The polymer was sealed and stored for later use.

[0102] Examples 1-9

[0103] A two-component polyurethane structural adhesive includes component A and component B, the specific composition of which is shown in Table 1. The amounts of each component in Table 1 are all "parts by weight".

[0104] Table 1

[0105] The preparation method of the two-component polyurethane structural adhesive includes:

[0106] (1) Mix the components of component A according to the amounts specified in Table 1 to obtain component A;

[0107] (2) Mix the components of component B according to the amounts in Table 1 to obtain component B.

[0108] Comparative Examples 1-5

[0109] A two-component polyurethane structural adhesive includes component A and component B, the specific composition of which is shown in Table 2. The amounts of each component in Table 2 are all "parts by weight".

[0110] Table 2

[0111] The preparation method of the two-component polyurethane structural adhesive includes:

[0112] (1) Mix the components of component A according to the amounts specified in Table 1 to obtain component A;

[0113] (2) Mix the components of component B according to the amounts in Table 1 to obtain component B.

[0114] Test methods

[0115] In this invention, standard conditions refer to: temperature (23±2)℃, relative humidity (50±5)%.

[0116] Viscosity change rate: Using a MIPACTM DP2X400 pneumatic glue gun with an air pressure of 0.40±0.05 MPa and a static mixing tube model 13-24, the initial pressure viscosity was measured. After standing at (23±2)℃ for 1 hour, the pressure viscosity after standing was measured. Viscosity change rate = (initial pressure viscosity - pressure viscosity after standing) / initial pressure viscosity.

[0117] Shear strength determination: Specimens were prepared according to GB / T 29755-2013. The test substrate was 3.0-5.0 mm thick (PP-LGF40)+(PP+EPDM-TD30). A MIPACTM DP2X400 pneumatic glue gun was used, with the air pressure adjusted to 0.40±0.05MPa and a static mixing tube of type 13-24. Extrusion was performed in one uniform pass. The width of the sheared specimen was 12.5 mm, and the glue layer thickness was (2.0±0.2) mm. The prepared specimens were placed under standard test conditions for 168 h before testing at a speed of (20±2) mm / min.

[0118] Tensile strength test: The test shall be conducted in accordance with the provisions of GB / T 528-2009, using type 2 dumbbell-shaped specimens.

[0119] High temperature environment: After the test piece is placed under standard test conditions for 168 hours, it is stored at 90℃ or 120℃ for 30 minutes and then directly subjected to shear test under the same conditions, or the test is completed within 5 minutes after it is removed.

[0120] 90℃ heat aging: After the specimens are placed under standard test conditions for 168 h, they are placed in a high-temperature oven at 90±2℃ for 336 h. After the specimens are removed and placed under standard test conditions for 24 h, a shear test is performed.

[0121] 120℃ heat aging: After the specimens are placed under standard test conditions for 168 h, they are placed in a high-temperature oven at 90±2℃ for 72 h. After the specimens are removed and placed under standard test conditions for 24 h, a shear test is performed.

[0122] Low temperature aging: After the test piece is placed under standard test conditions for 168 hours, it is stored at -30℃ for 30 minutes and then directly subjected to shear test under the same conditions or the test is completed within 5 minutes after being removed.

[0123] Water aging resistance: After the specimen is placed under standard test conditions for 168 h, it is immersed in a constant temperature water bath at 40℃ for 240 h. After the specimen is removed and placed under standard test conditions for 24 h, a shear test is performed.

[0124] Humid heat aging: After the specimen was placed under standard test conditions for 168 h, it was placed in an environment with a temperature of 60±2℃ and a relative humidity of 90% for 336 h. After the specimen was removed and placed under standard test conditions for 24 h, a shear test was performed.

[0125] High and low temperature alternation: After the test piece is placed under standard test conditions for 168 hours, proceed with the following steps:

[0126] a) Place the sample in a low-temperature chamber that has been adjusted to (-40±2)℃ for 6 h;

[0127] b) Remove the sample and place it under standard conditions for 1 hour;

[0128] c) Store the sample in a constant temperature oven at (90±2)℃ for 1 h;

[0129] d) Remove the sample and place it under standard conditions for 1 hour;

[0130] e) Place the sample in a constant temperature and humidity test chamber at 40℃ and 95% relative humidity for 90 h;

[0131] f) Remove the sample and place it under standard conditions for 6 hours;

[0132] g) Repeat af for a total of 10 cycles; remove the sample, place it under standard test conditions for 24 h, and then perform a shear test.

[0133] Heat curing time: Apply the adhesive evenly to the test plate, ensuring a uniform thickness (approximately 3 mm) and a length of approximately 150 mm. Place in an oven at 65±2℃ and record the start time. Wait a few moments according to the product specifications, then gently touch the sample surface with a polyethylene film (ensuring no repeated contact). If any sample is lifted from the polyethylene film, repeat this step every minute until no sample is lifted from the polyethylene film; record the end time. Report the total duration in minutes.

[0134] Interfacial adhesion: An appropriate amount of sealant was evenly applied to the test substrate, approximately 100 mm long, 10 mm wide, and 3 mm thick. After complete curing for 168 h, the sealant was peeled off from one end and pulled at a 90° angle. The percentage of cohesive failure (CF) area between the sealant and the test substrate was observed and recorded.

[0135] The test results are shown in Tables 3 and 4.

[0136] Table 3

[0137] Table 4

[0138] The test results show that:

[0139] (1) As can be seen from Examples 1-9, the present invention achieves high-temperature rapid curing while maintaining a low viscosity change rate by selecting a combination of catalyst A and catalyst B.

[0140] (2) As can be seen from Examples 1-3, the present invention improves the tensile strength and shear strength of the structural adhesive by further changing the -SH:Bi ratio of catalyst A. By adjusting the -SH:Bi ratio, a wider range of viscosity change rates can also be obtained.

[0141] (3) By comparing Example 2 with Examples 4-7, it can be seen that the present invention can further improve the performance of structural adhesive by further changing the amount of silane coupling agent, polyisocyanate or catalyst B.

[0142] (4) By comparing Example 2 and Example 8, it can be seen that the present invention improves the tensile strength of the structural adhesive after aging by further adding toughening resin to component A.

[0143] (5) By comparing Example 2 and Example 9, it can be seen that the modified castor oil and bio-based polyol of the present invention can be replaced within a certain range.

[0144] (6) By comparing Example 2 with Comparative Examples 1-4, it can be seen that the catalyst A of the present invention, in combination with catalyst B, can achieve high-temperature rapid curing while maintaining a low viscosity change rate. The technical effect of the present invention cannot be achieved by using catalyst A or catalyst B alone. By comparing Example 2 with Comparative Example 5, it can be seen that the lack of silane coupling agent in components A and B will lead to a decrease in shear strength and interfacial adhesion.

[0145] In summary, this invention achieves rapid high-temperature curing while maintaining a low viscosity change rate by preparing a two-component polyurethane structural adhesive. After aging, the structural adhesive of this invention also exhibits excellent shear strength and adhesion performance, especially under high-temperature conditions, and the substrate adhesion reaches cohesive failure.

[0146] The above description is only a specific embodiment of the present invention, but the protection scope of the present invention is not limited thereto. Those skilled in the art should understand that any changes or substitutions that can be easily conceived by those skilled in the art within the technical scope disclosed in the present invention fall within the protection and disclosure scope of the present invention.

Claims

1. A two-component polyurethane structural adhesive characterized in that, The two-component polyurethane structural adhesive comprises an A component and a B component; The A component comprises modified castor oil, bio-based polyol, chain extender, water scavenger, filler, silane coupling agent, anti-aging agent, catalyst A and catalyst B; The B component comprises polyisocyanate, polyisocyanate polymer, curing agent, water scavenger, fumed white carbon black, silane coupling agent and plasticizer; The catalyst A is a coordination compound formed by a mercapto-containing organic compound and an organic bismuth compound; The catalyst B comprises an organic metal compound.

2. The two-component polyurethane structural adhesive according to claim 1, characterized in that, The A component comprises the following components in parts by weight: modified castor oil 15-30 parts, bio-based polyol 30-40 parts, chain extender 5-10 parts, water scavenger 1-3 parts, filler 20-35 parts, silane coupling agent 0.5-2.5 parts, aging agent 1-3 parts, catalyst A 1-5 parts and catalyst B 0.1-1 part.

3. The two-component polyurethane structural adhesive according to claim 1, characterized in that, The chain extender comprises any one or a combination of at least two of ethylene glycol, butanediol, propylene glycol, glycerol, dipropylene glycol, 1,4-butanediol, 1,6-hexanediol or 2-ethyl-1,3-hexanediol; The water scavenger in the A component comprises any one or a combination of at least two of calcium oxide, molecular sieve or p-methylbenzenesulfonic acid isocyanate; The filler comprises any one or a combination of at least two of kaolin, nano calcium carbonate, light calcium carbonate or talc powder; The silane coupling agent in the A component comprises any one or a combination of at least two of γ-glycidoxypropyltrimethoxysilane, γ-mercaptopropyltrimethoxysilane, γ-mercaptopropyltriethoxysilane, γ-aminopropyltrimethoxysilane, γ-aminopropyltriethoxysilane, aminoethylmethyltrimethoxysilane, anilinopropyltrimethoxysilane, 3-methacryloyloxypropyltrimethoxysilane or thiosilicic acid, O, O, O-triethyl-sulfide-[3-(triethoxysilyl)propyl] ester.

4. The two-component polyurethane structural adhesive according to claim 1, characterized in that, The mercapto-containing organic compound comprises any one or a combination of at least two of bis(3-mercaptopropionic acid)ethylene glycol, tetra(3-mercaptopropionic acid) pentaerythritol ester or trimethylolpropane tri(3-mercaptopropionate). The molar ratio of -SH in the mercapto-containing organic compound to Bi in the organic bismuth compound is (15-26):1; The preparation method of the catalyst A comprises the following steps: mixing the mercapto-containing organic compound and the organic bismuth compound under acidic conditions to perform a coordination reaction to obtain the catalyst A; The coordination reaction is performed under vacuum; The catalyst B comprises any one or a combination of at least two of dibutyltin dichloride, dibutyltin dilaurate, stannous octoate, dibutyltin diacetate or Polycat SA series of heat-sensitive catalysts; The A component further comprises 1-10 parts of toughening resin; The toughening resin comprises bisphenol A polyoxyethylene ether and / or bisphenol A polyoxypropylene ether.

5. The two-component polyurethane structural adhesive according to claim 1, wherein The B component comprises components in the following weight proportions: 15-25 parts of polyisocyanate, 35-55 parts of polyisocyanate polymer, 2-5 parts of curing agent, 0.01-5 parts of water removal agent, 1-5 parts of fumed white carbon black, 0.5-2.5 parts of silane coupling agent, and 15-30 parts of plasticizer.

6. The two-component polyurethane structural adhesive according to claim 1, wherein The polyisocyanate polymer comprises a polyurethane prepared by reacting isocyanate with polyol; The polyurethane prepared by reacting isocyanate with polyol has an NCO content of 10%-15%; The water removal agent in the B component comprises any one or a combination of at least two of calcium oxide, molecular sieve, or p-methylbenzenesulfonic acid isocyanate; The silane coupling agent in the B component comprises any one or a combination of at least two of γ-glycidoxypropyltrimethoxysilane, γ-mercaptopropyltrimethoxysilane, γ-mercaptopropyltriethoxysilane, γ-aminopropyltrimethoxysilane, γ-aminopropyltriethoxysilane, aminoethylmethyltrimethoxysilane, anilinopropyltrimethoxysilane, 3-methacryloyloxypropyltrimethoxysilane, or thiosilicic acid, O, O, O-triethyl-sulfur-[3-(triethoxysilyl)propyl] ester; The plasticizer comprises any one or a combination of at least two of dipropylene glycol dibenzoate, alkyl sulfonate phenyl ester, diisononyl phthalate, diisooctyl phthalate, or diisodecyl phthalate.

7. A process for the preparation of a two-component polyurethane structural adhesive according to any one of claims 1 to 6, characterized in that, The preparation method comprises preparation of the A component and preparation of the B component; The preparation of the A component comprises the following steps: mixing modified castor oil, bio-based polyol, chain extender, water removal agent, filler, silane coupling agent, aging agent, catalyst A, catalyst B, and optional toughening resin to obtain the A component; The preparation of the B component comprises the following steps: mixing polyisocyanate, polyisocyanate polymer, curing agent, water removal agent, fumed white carbon black, silane coupling agent, and plasticizer to obtain the B component.

8. A method of using the two-component polyurethane structural adhesive according to any one of claims 1 to 6, characterized in that, The use method comprises the following steps: mixing the A component and the B component, coating on the surface of the substrate to be bonded, curing, and completing the use of the two-component polyurethane structural adhesive.

9. The method of use of claim 8, wherein, The volume ratio of the A component to the B component is (0.9-1.1):

1.

10. Use of the two-component polyurethane structural adhesive according to any one of claims 1-6 in bonding of automobile parts.

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