Thermocuring single-component polyurethane structural adhesive and preparation method thereof

Abstract

The invention relates to the technical field of polyurethane structural adhesives, in particular to a thermocuring single-component polyurethane structural adhesive and a preparation method thereof. The thermosetting single-component polyurethane structural adhesive is prepared from the following components in parts by weight: 10 to 30 parts of polyester polyol subjected to microcapsule sealing treatment, 60 to 80 parts of an isocyanate-terminated polymer, 5 to 20 parts of a plasticizer, 1 to 5 parts of a surface accelerant and 0.1 to 1 part of a catalyst. The prepared single-component polyurethane structural adhesive has excellent room-temperature long-range stability, and the problems of glue failure and shortened shelf life caused by long-time transportation and storage at high temperature in summer can be avoided; due to the normal-temperature low-viscosity characteristic, the colloid can be constructed at normal temperature and is convenient to use; good PC bonding capability is achieved, and the bonding requirements in multiple scenes can be met.

Description

Technical Field

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

[0002] In the adhesive industry, polyurethane structural adhesives occupy half of the market due to their excellent adhesion and applicability. Two-component polyurethane structural adhesives require a relatively complicated supporting construction process and strict ratios. The adhesive needs to be mixed thoroughly and evenly. If the mixing is uneven, the bonding performance will be greatly affected. Conventional reactive polyurethane hot melt adhesives require heating dispensing equipment, and the unit price of the glue is expensive. Under normal circumstances, it is not suitable for structural bonding; some single-component adhesives, such as single-component epoxy structural adhesives, need to be stored at low temperatures and transported at low temperatures, which increases transportation costs and greatly limits stability. At the same time, as people's awareness of environmental protection increases, some UV adhesives contain sensitizing monomers that increase skin irritation, and directly use acrylic monomers for UV-induced curing, which has defects such as strong odor, high sensitization, and environmental protection.

[0003] Therefore, developing a one-component structural adhesive that can be dispensed at room temperature, has good bonding properties, and can adapt to short-term, high-temperature, and long-distance transportation has great potential commercial value and prospects. Summary of the invention

[0004] In order to solve the above technical problems existing in the prior art, the present invention provides a thermally curing one-component polyurethane structural adhesive and a preparation method thereof, so as to solve the technical problems in the prior art that the structural adhesive has a high curing temperature, cannot achieve medium and low temperature curing, and is unstable at room temperature.

[0005] The technical solution of the present invention to solve the above technical problems is as follows:

[0006] The first aspect of the present invention is to provide a heat-curing one-component polyurethane structural adhesive, comprising the following components in parts by weight:

[0007] 10-30 parts of microcapsule-sealed polyester polyol, 60-80 parts of isocyanate-terminated polymer, 5-20 parts of plasticizer, 1-5 parts of surface accelerator and 0.1-1 parts of catalyst.

[0008] The above-mentioned heat-curing single-component polyurethane structural adhesive provided by the present invention can achieve medium and low temperature curing, and can be cured within 30 minutes at 80-100°C, and can immediately obtain a high bonding strength, which meets the rapid bonding and fixing requirements of conventional adhesives; and has excellent bonding performance, avoiding the problem of uneven bonding caused by inappropriate ratios, and taking into account the high reliability characteristics of polyurethane adhesives; at the same time, it can be transported over long distances at room temperature or even high temperature.

[0009] On the basis of the above technical solution, the present invention can also make the following improvements:

[0010] Further, the isocyanate-terminated polymer comprises the following components in parts by weight:

[0011] 40-60 parts of high molecular weight difunctional polyether polyol, 40-60 parts of high molecular weight trifunctional polyether polyol, 0.03-2 parts of stabilizer, 0.5-1 parts of anti-hydrolysis agent, 0.1-1 parts of defoaming agent, 10-20 parts of polyisocyanate, and 0.2-1 parts of silane coupling agent.

[0012] Furthermore, the synthesis of the isocyanate-terminated polymer includes the following steps: dehydrating the mixed stabilizer, anti-hydrolysis agent, defoamer, high molecular weight difunctional polyether polyol and high molecular weight trifunctional polyether polyol, and then heating and reacting with polyisocyanate and silane coupling agent to obtain the isocyanate-terminated polymer.

[0013] After synthesis, the isocyanate-terminated polymer needs to be kept in a sealed container to prevent moisture from forming.

[0014] The beneficial effects of adopting the above-mentioned further technical scheme are: the use of high molecular weight trifunctional polyether polyols and polyisocyanates with near trifunctionality can produce higher crosslinking density, initial strength and maintain the flexibility of the glue; the use of high molecular weight difunctional polyether polyols provides a liquid component with lower viscosity, so that the synthesized prepolymer still has a very low viscosity at room temperature, which is convenient for mixing with other components.

[0015] Furthermore, the high molecular weight bifunctional polyether polyol is selected from any one or more of polyether polyols with molecular weights of 2000, 6000, and 8000, preferably one or two of DDL-8000D and DDL-6000D of Shangzheng New Materials.

[0016] The beneficial effect of adopting the above further technical solution is that the present invention adopts high molecular weight bifunctional polyether polyol to reduce the reaction activity, avoid the occurrence of explosion polymerization when synthesizing isocyanate-terminated polymers, and at the same time improve the toughness of the product and reduce the viscosity and modulus of the isocyanate-terminated polymers.

[0017] Furthermore, the high molecular weight trifunctional polyether polyol is selected from one or both of EP330NG of Bluestar Dongda and 3600H of Shangzheng New Materials.

[0018] Furthermore, the anti-hydrolysis agent is carbodiimide, the stabilizer is one or more of phosphoric acid or antioxidant 1010, the defoamer is one of BASF EFKA SI 2038 or Deqian 5500, the polyisocyanate is one or two of MDI, HDI, carbodiimide-modified MDI or PAPI, and the silane coupling agent is any one of KH550, KH602, and Maitu's A189.

[0019] Furthermore, the microcapsules of the polyester polyol treated by microcapsule encapsulation are selected from Hefei Xinneng Microcapsule R1208E. The preparation process of the polyester polyol treated by microcapsule encapsulation includes: first dissolving ABS (acrylonitrile-succinonitrile-styrene copolymer) and EC (ethyl cellulose) in dichloromethane to obtain a mixed solution, then adding the polyester polyol baked at 80°C dropwise to the mixed solution under stirring, then adding the inducer (polydimethylsiloxane) dropwise at a constant pressure, and then continuing to add n-heptane, stirring at 60°C for 1h, settling and filtering the precipitate to wash with water and n-heptane to obtain the polyester polyol treated by microcapsule encapsulation. The polyol content in the polyester polyol treated by microcapsule encapsulation after dehydration is 80%. The polyester polyol is any one of Evonik's 7360, Evonik's 7330, and Evonik's 7380.

[0020] Furthermore, the dehydration treatment is air drying at room temperature for 20 days and drying in a vacuum dryer for 10 days, or low-temperature centrifugal dehydration treatment.

[0021] Furthermore, the catalyst includes one or two of dibutyltin diisocyanate (T12), stannous octoate, and triethylenediamine; the surface promoter is selected from any one of isooctyl ether phosphate, lauryl alcohol polyoxyethylene ether phosphate or 2-hydroxyethyl methacrylate phosphate; the plasticizer is selected from any one of C5 petroleum resin, C9 petroleum resin, liquid petroleum resin PL1000s of Cologne Chemical, and EG1000 liquid petroleum resin of Ningbo Yonghua.

[0022] The beneficial effect of adopting the above further technical solution is: by adding surfactants and plasticizers to adjust the viscosity, the polyester polyol coating is dissolved and the initial bonding force is improved.

[0023] Another aspect of the present invention is to provide a method for preparing the above-mentioned heat-curing single-component polyurethane structural adhesive, comprising the following steps: adding a surface accelerator and a plasticizer that have been pre-dehydrated by molecular sieves into a stirring kettle under a nitrogen atmosphere at an ambient humidity of less than 40%, and after the temperature rises to 80-100° C. and stabilizes for 5-10 minutes, adding an isocyanate-terminated polymer under stirring conditions, controlling the temperature to 50-55° C., and adding a microcapsule-sealed polyester polyol under a nitrogen atmosphere while stirring, controlling the temperature to 50-55° C. and continuing to stir until all solids are dissolved, vacuum stirring for 1-2 hours, and finally adding a catalyst, continuing to vacuum stir for 0.5-2 hours, breaking the vacuum, discharging, and sealing and packaging to obtain the heat-curing single-component polyurethane structural adhesive.

[0024] Compared with the prior art, the present invention has the following technical effects:

[0025] The heat-curing one-component polyurethane structural adhesive provided by the present invention can be stored for a long time at room temperature because the polyol that reacts with the isocyanate group is enclosed in the microcapsule. If the outer packaging is well sealed, it can be stored for a long time at room temperature, and the viscosity and other properties remain basically unchanged or slightly increase.

[0026] The isocyanate-terminated prepolymer has low viscosity, providing the conditions for sizing at room temperature and good wetting with the interface;

[0027] When the ambient temperature reaches above 80 degrees, the microcapsules quickly break or melt, releasing the polyols involved in the reaction. With the participation of the catalyst, they quickly react with the isocyanate groups to provide bonding strength and quickly solidify.

[0028] The heat-curing single-component polyurethane structural adhesive of the present invention has the advantage of room-temperature gluing that ordinary polyurethane hot-melt adhesives do not have, and also has the high reliability characteristic of polyurethane hot-melt adhesives, thereby reducing the defects of ordinary two-component polyurethane structural adhesives such as poor bonding caused by inappropriate mixing ratios. DETAILED DESCRIPTION

[0029] The following specific embodiments illustrate the implementation of the present invention, and those skilled in the art can easily understand other advantages and effects of the present invention from the contents disclosed in this specification. Although the description of the present invention will be introduced in conjunction with the preferred embodiment, this does not mean that the features of this invention are limited to this implementation. On the contrary, the purpose of introducing the invention in conjunction with the implementation is to cover other options or modifications that may extend based on the claims of the present invention. In order to provide a deep understanding of the present invention, the following description will include many specific details. The present invention can also be implemented without using these details. In addition, in order to avoid confusion or blurring the focus of the present invention, some specific details will be omitted in the description. It should be noted that the embodiments of the present invention and the features in the embodiments can be combined with each other without conflict.

[0030] Example 1

[0031] Preparation of Isocyanate Terminated Polymers:

[0032] The isocyanate-terminated polymer includes the following components in parts by weight: 440 g of high molecular weight difunctional polyether polyol (Shangzheng New Materials DDL-6000D) and 440 g of high molecular weight trifunctional polyether polyol (Shangzheng New Materials 3600H), 0.3 g of stabilizer (phosphoric acid), 1 g of defoamer (Deqian 5500), 8 g of anti-hydrolysis agent (carbodiimide), 100 g of polyisocyanate (PAPI), and 2 g of silane coupling agent (Momentive's A189);

[0033] The synthesis process is as follows: add 440g of high molecular weight difunctional polyether polyol (Shangzheng New Materials DDL-6000D), 440g of high molecular weight trifunctional polyether polyol (Shangzheng New Materials 3600H), 0.3g of stabilizer (phosphoric acid), 1g of defoamer (Deqian 5500), and 8g of anti-hydrolysis agent (carbodiimide) into a reaction bottle and mix, dehydrate at 130°C for 2h in advance for use, cool to 80°C, add 100g of polyisocyanate (PAPI) into the reaction bottle, heat to 120°C, continue to react for 60min, then add 2g of silane coupling agent (Maitu A189) and react for 60min, break the vacuum with nitrogen, pour into a sealed container to isolate moisture for use, and record as prepolymer A-1.

[0034] Example 2

[0035] Preparation of Isocyanate Terminated Polymers:

[0036] The isocyanate-terminated polymer includes the following components in parts by weight: 480 g high molecular weight difunctional polyether polyol (Shangzheng New Materials DDL-6000D), 480 g high molecular weight trifunctional polyether polyol (Shangzheng New Materials 3600H), 0.3 g stabilizer (phosphoric acid), 1 g defoamer (Deqian 5500), 8 g anti-hydrolysis agent (carbodiimide), 126.8 g polyisocyanate (carbodiimide modified MDI), 4 g silane coupling agent (Maitu A189);

[0037] The synthesis process is as follows: 480g of high molecular weight difunctional polyether polyol (Shangzheng New Materials DDL-6000D), 480g of high molecular weight trifunctional polyether polyol (Shangzheng New Materials 3600H), 0.3g of stabilizer (phosphoric acid), 1g of defoamer (Deqian 5500), and 8g of anti-hydrolysis agent (carbodiimide) are added to a reaction bottle and mixed, and pre-dehydrated at 130°C for 2h for use, cooled to 80°C, 126.8g of polyisocyanate (carbodiimide modified MDI) is added to the reaction bottle, heated to 120°C, and the reaction is continued for 60min, and then 4g of silane coupling agent (Maitu A189) is added to react for 60min, the vacuum is broken by nitrogen, and the mixture is poured into a sealed container to isolate moisture for use, which is recorded as prepolymer A-2.

[0038] Example 3

[0039] Preparation of Isocyanate Terminated Polymers:

[0040] The isocyanate-terminated polymer includes the following components in parts by weight: 520 g high molecular weight difunctional polyether polyol (Shangzheng New Materials DDL-8000D), 520 g high molecular weight trifunctional polyether polyol (Bluestar Dongda EP3300NG), 2 g stabilizer (phosphoric acid), 3 g defoamer (Deqian 5500), 10 g anti-hydrolysis agent (carbodiimide), 150 g polyisocyanate (PAPI), 6 g silane coupling agent (Momentive's A189);

[0041] The synthesis process is as follows: 520g of high molecular weight difunctional polyether polyol (Shangzheng New Materials DDL-8000D), 520g of high molecular weight trifunctional polyether polyol (Bluestar Dongda EP3300NG), 2g of stabilizer (phosphoric acid), 3g of defoamer (Deqian 5500), and 10g of anti-hydrolysis agent (carbodiimide) are added to a reaction bottle and mixed, and pre-dehydrated at 130°C for 2h for use, cooled to 80°C, 150g of polyisocyanate (PAPI) is added to the reaction bottle, heated to 120°C, and the reaction is continued for 60min, and then 6g of silane coupling agent (Maitu A189) is added to react for 60min, the vacuum is broken by nitrogen, and the mixture is poured into a sealed container to isolate moisture for use, which is recorded as prepolymer A-3.

[0042] Example 4

[0043] Preparation of Isocyanate Terminated Polymers:

[0044] The isocyanate-terminated polymer includes the following components in parts by weight: 560 g of high molecular weight difunctional polyether polyol (Shangzheng New Materials DDL-6000D), 560 g of high molecular weight trifunctional polyether polyol (Bluestar Dongda EP3300NG), 5 g of stabilizer (phosphoric acid), 1 g of defoamer (Deqian 5500), 8 g of anti-hydrolysis agent (carbodiimide), 180 g of polyisocyanate (MDI), and 8 g of silane coupling agent (Maitu A189);

[0045] The synthesis process is as follows: 560g of high molecular weight difunctional polyether polyol (Shangzheng New Materials DDL-6000D), 560g of high molecular weight trifunctional polyether polyol (Bluestar Dongda EP3300NG), 5g of stabilizer (phosphoric acid), 1g of defoamer (Deqian 5500), and 8g of anti-hydrolysis agent (carbodiimide) are added to a reaction bottle and mixed, and pre-dehydrated at 130°C for 2h for use, cooled to 80°C, 180g of polyisocyanate (MDI) is added to the reaction bottle, heated to 120°C, and the reaction is continued for 60min, and then 8g of silane coupling agent (Maitu A189) is added to react for 60min, the vacuum is broken by nitrogen, and the mixture is poured into a sealed container to isolate moisture for use, which is recorded as prepolymer A-4.

[0046] Comparative Example 1

[0047] Preparation of Isocyanate Terminated Polymers:

[0048] The isocyanate-terminated polymer includes the following components in parts by weight: 440 g high molecular weight difunctional polyether polyol (Shangzheng New Materials DDL-6000D), 440 g low molecular weight difunctional polyether polyol (Bluestar Dongda DL-2000D), 0.3 g stabilizer (phosphoric acid), 1 g defoamer (Deqian 5500), 8 g anti-hydrolysis agent (carbodiimide), 148.98 g polyisocyanate (PAPI), 10 g silane coupling agent (KH590);

[0049] The synthesis process is as follows: 440g of high molecular weight difunctional polyether polyol (Shangzheng New Materials DDL-6000D), 440g of low molecular weight difunctional polyether polyol (Bluestar Dongda DL-2000D), 0.3g of stabilizer (phosphoric acid), 1g of defoamer (Deqian 5500), and 8g of anti-hydrolysis agent (carbodiimide) are added to a reaction bottle and mixed, and pre-dehydrated at 130°C for 2h for use, cooled to 80°C, 148.98g of polyisocyanate (PAPI) is added to the reaction bottle, heated to 120°C, and the reaction is continued for 60min, and then 10g of silane coupling agent (KH590) is added to react for 60min, the vacuum is broken by nitrogen, and the mixture is poured into a sealed container to isolate moisture for use, which is recorded as prepolymer A-5.

[0050] Example 6

[0051] Preparation of one-component thermosetting polyurethane structural adhesive:

[0052] When the ambient humidity is below 40%, 37 g of lauryl alcohol polyoxyethylene ether phosphate (Haishan, MOA-3P) pre-dehydrated with molecular sieves and 80 g of liquid petroleum resin (Cologne Chemical PL1000S) are added to a stirring kettle under a nitrogen atmosphere. After the temperature rises to 100° C. and stabilizes for 10 minutes, 720 g of the isocyanate-terminated prepolymer A-1 synthesized in Example 1 is added under stirring. The temperature is controlled to 50-55° C. Under a nitrogen atmosphere, 160 g of microcapsule-treated polyester polyol is quickly added while stirring. The temperature is controlled to 50-55° C. and stirring is continued until all solids are dissolved. The mixture is vacuum stirred for 2 h under -0.098 MPa. Finally, 3 g of catalyst (T12) is added, and vacuum stirring is continued for 1 h. The vacuum is broken with nitrogen, the material is discharged, and the single-component thermosetting polyurethane structural adhesive B1 is obtained by sealing and packaging.

[0053] Example 7

[0054] Preparation of heat-curing one-component polyurethane structural adhesive:

[0055] When the ambient humidity is below 40%, 10 g of lauryl alcohol polyoxyethylene ether phosphate (Haishan, MOA-3P) pre-dehydrated with molecular sieves and 50 g of liquid petroleum resin (Cologne Chemical PL1000S) are added to a stirring kettle under a nitrogen atmosphere. After the temperature rises to 100°C and stabilizes for 10 minutes, 600 g of isocyanate-terminated prepolymer A-2 synthesized in Example 2 is added under stirring. The temperature is controlled to 50-55°C. Under a nitrogen atmosphere, 120 g of microcapsule-treated polyester polyol is quickly added while stirring. The temperature is controlled to 50-55°C and stirring is continued until all solids are dissolved. The mixture is vacuum stirred for 2 h under -0.098 MPa. Finally, 2 g of catalyst (T12) is added and vacuum stirred for 1 h. The vacuum is broken with nitrogen. The material is discharged and sealed and packaged to obtain a single-component thermosetting polyurethane structural adhesive B2.

[0056] Example 8

[0057] Preparation of heat-curing one-component polyurethane structural adhesive:

[0058] When the ambient humidity is below 40%, 18 g of lauryl alcohol polyoxyethylene ether phosphate (Haishan, MOA-3P) pre-dehydrated with molecular sieves and 150 g of liquid petroleum resin (Cologne Chemical PL1000S) are added to a stirring kettle under a nitrogen atmosphere. After the temperature rises to 100°C and stabilizes for 10 minutes, 640 g of the isocyanate-terminated prepolymer A-3 synthesized in Example 3 is added under stirring. The temperature is controlled to 50-55°C. Under a nitrogen atmosphere, 210 g of microcapsule-treated polyester polyol is quickly added while stirring. The temperature is controlled to 50-55°C and stirring is continued until all solids are dissolved. The mixture is vacuum stirred for 2 h at -0.098 MPa. Finally, 4.5 g of catalyst (T12) is added and vacuum stirred for 1 h. The vacuum is broken with nitrogen. The mixture is discharged and sealed and packaged to obtain a single-component thermosetting polyurethane structural adhesive B3.

[0059] Example 9

[0060] Preparation of heat-curing one-component polyurethane structural adhesive:

[0061] When the ambient humidity is below 40%, 48 g of lauryl alcohol polyoxyethylene ether phosphate (Haishan, MOA-3P) pre-dehydrated with molecular sieves and 190 g of liquid petroleum resin (Cologne Chemical PL1000S) are added to a stirring kettle under a nitrogen atmosphere. After the temperature rises to 100°C and stabilizes for 10 minutes, 800 g of the isocyanate-terminated prepolymer A-4 synthesized in Example 4 is added under stirring. The temperature is controlled to 50-55°C. Under a nitrogen atmosphere, 260 g of microcapsule-treated polyester polyol is quickly added while stirring. The temperature is controlled to 50-55°C and stirring is continued until all solids are dissolved. The mixture is vacuum stirred for 2 h under -0.098 MPa. Finally, 1 g of catalyst (T12) is added and vacuum stirred for 1 h. The vacuum is broken with nitrogen. The material is discharged and sealed and packaged to obtain a single-component thermosetting polyurethane structural adhesive B4.

[0062] Comparative Example 2

[0063] Preparation of heat-curing one-component polyurethane structural adhesive:

[0064] When the ambient humidity is below 40%, 37 g of lauryl alcohol polyoxyethylene ether phosphate (Haishan, MOA-3P) pre-dehydrated with molecular sieves and 80 g of liquid petroleum resin (Cologne Chemical PL1000S) are added to a stirring kettle under a nitrogen atmosphere. After the temperature rises to 100°C and stabilizes for 10 minutes, 720 g of the isocyanate-terminated prepolymer A-5 synthesized in Example 5 is added under stirring. The temperature is controlled to 50-55°C. Under a nitrogen atmosphere, 160 g of microcapsule-treated polyester polyol is quickly added while stirring. The temperature is controlled to 50-55°C and stirring is continued until all solids are dissolved. Vacuum stirring is carried out under -0.098 MPa for 2 h. Finally, 3 g of catalyst (T12) is added and vacuum stirring is continued for 1 h. The vacuum is broken with nitrogen. The material is discharged and sealed and packaged to obtain a single-component thermosetting polyurethane structural adhesive B5.

[0065] Comparative Example 3

[0066] Preparation of heat-curing one-component polyurethane structural adhesive:

[0067] When the ambient humidity is below 40%, 37 g of lauryl alcohol polyoxyethylene ether phosphate (Haishan, MOA-3P) pre-dehydrated with molecular sieves and 80 g of liquid petroleum resin (Cologne Chemical PL1000S) are added to a stirring kettle under a nitrogen atmosphere. After the temperature rises to 100° C. and stabilizes for 10 minutes, 720 g of the isocyanate-terminated prepolymer A-1 synthesized in Example 1 is added under stirring. The temperature is controlled to 50-55° C. and stirring is continued until all the solids are dissolved. The mixture is vacuum stirred for 2 h at -0.098 MPa. Finally, 3 g of catalyst (T12) is added and vacuum stirring is continued for 1 h. The vacuum is broken with nitrogen, the material is discharged, and the single-component thermosetting polyurethane structural adhesive B6 is obtained by sealing and packaging.

[0068] Comparative Example 4

[0069] This comparative example is based on comparative example 3, and 126g of polyester polyol 7360 that has not been subjected to microcapsule sealing treatment is added. Due to the lack of sealing protection, the free NCO groups in the polyester polyol and the prepolymer A-1 react to cross-link, and the reaction viscosity is too large. Until the stirring stops, the glue solidifies in the reaction container and no effective colloid can be obtained. Therefore, the comparative glue cannot be used for subsequent testing.

[0070] The codes and components of the prepolymer and the corresponding thermal curing one-component polyurethane structural adhesive are summarized in Table 1.

[0071] Table 1 Prepolymers used in the colloid and the corresponding hot melt adhesive numbers obtained

[0072] Prepolymer A1 A2 A3 A4 A5 A1 The obtained structural adhesive B1 B2 B3 B4 B5 B6 Polyols with epoxy end capping have have none none none have Polyols have three functional groups have have have have none have Isocyanate functionality 2.7 2.2 2.7 2.0 2.7 2.7

[0073] Note: The difference between B1 and B6 is whether microcapsule-encapsulated crystalline polyester polyol is added.

[0074] Performance Testing

[0075] 1. Samples, substrates and curing conditions

[0076] Selected substrates: PC+20% GF vs PC+20% GF;

[0077] Shear strength test: 3mm diameter dot;

[0078] Colloid thickness: 0.15mm;

[0079] Pressing area: 25*5mm;

[0080] Stretching speed: 10mm / min;

[0081] Curing conditions: 90°C, 30min;

[0082] Test environment temperature: 25℃.

[0083] 2. Strength test

[0084] Prepolymer shear strength: Apply a 3mm diameter glue dot to the substrate surface, add a 0.15mm gap sheet, press on the second sheet, use a 1kg weight to press for 20 minutes, and use a tensile testing machine to test the shear strength.

[0085] Shear strength of structural adhesive: Apply a 3mm diameter glue dot to the surface of the substrate, add a 0.15mm gap sheet, press on the second sheet, use a 1kg weight to press for 10s, remove the weight, put the sample into a 90℃ oven to cure for 30min, take it out and cool it to room temperature before measuring.

[0086] 3. Viscosity test

[0087] Instrument used: Haake RS6000 rheometer

[0088] Use rotor: C20 rotor

[0089] Speed: 10 -1 rpm -1

[0090] 4. Stability test

[0091] Instrument used: Haake RS6000 rheometer

[0092] Use rotor: C20 rotor

[0093] Speed: 10 -1 rpm -1

[0094] Test duration: 1 day, 7 days, 30 days, 60 days

[0095] Storage environment: 40℃, sealed and dry place.

[0096] The polyurethane structural adhesives obtained in the examples and comparative examples were subjected to the above performance tests, and the test results are shown in Table 2.

[0097] Table 2 Test results of viscosity and shear strength of polyurethane structural adhesive

[0098] Structural adhesive number B1 B2 B3 B4 B5 B6 Shear strength / Mpa 10.24 9.46 7.74 6.25 5.38 0.62 Viscosity / mpas(25℃) 60500 57000 49600 44000 32700 6100

[0099] It can be seen from the test results in Table 2 and the composition of the structural adhesive in Table 1 that, in the present invention, the structural adhesive (B1 and B2) containing the epoxy-terminated trifunctional polyol 3600H exhibits higher bonding strength than the non-epoxy-terminated trifunctional polyol EP330NG (B3 and B4); at the same time, the structural adhesive (B1, B2, B3 and B4) containing the trifunctional polyol has much higher bonding strength than the structural adhesive (B5) containing only the difunctional polyol, because the multifunctional polyol reacts with the multifunctional isocyanate, has a large crosslinking density and a high bulk strength; at the same time, it can be seen that the higher the isocyanate functionality, the higher the shear strength, that is, the shear strength B1>B2>B4; due to the lack of the important reaction of the polyester polyol and the isocyanate group, the strength of the comparative example B6 comes from the reaction of some NCO groups in the prepolymer with moisture and the strength of plasticizers such as phosphate esters and petroleum resins, which cannot meet the bonding requirements. In addition, due to the reduction of the influence of the high-viscosity blocked isocyanate, the viscosity of the comparative example B6 at room temperature is very low. The viscosity is 6100-60500cps at 25℃, and the obtained structural adhesives can meet the process requirements of air pressure dispensing at room temperature.

[0100] Table 3 Storage stability test data of various structural adhesives (viscosity characterization / 40°C)

[0101] Number / Storage Time 1 day 7 days 30 days 60 days 60-day viscosity growth rate B1 60500 62000 65600 68000 12.40％ B2 57000 59000 62800 66000 15.79％ B3 49600 51300 54000 58100 17.14％ B4 44000 46100 49000 51300 16.59％ B5 32700 34000 36100 38000 16.21％ B6 6100 7000 8400 12300 101.64％

[0102] Table 3 shows the storage stability performance of each structural adhesive. It can be seen from the test results in Table 3 that each structural adhesive of the embodiments (B1, B2, B3, B4) and the comparative example (B5) of the present invention has a small viscosity increase (<20%) at a relatively high storage temperature of 40°C, which can meet the storage stability requirements. This excellent stability can be attributed to the polyester polyol treated with microcapsule sealing, which has a good sealing effect on the polyol at 40°C, and the sealed polyol is in a solid state (softening point is about 62°C), which slows down the rate of seepage from the microcapsule. Considering that part of the moisture enters the colloid during the sizing test, part of the colloid reacts with the isocyanate group and trace water vapor, resulting in a slow increase in viscosity. Therefore, the structural adhesive of the present invention can accept the short-term slightly high temperature transportation demand during the 40-50°C transportation process, without the need for refrigeration or air conditioning temperature control, thereby reducing transportation costs.

[0103] The one-component thermosetting polyurethane structural adhesive prepared in the present invention has both high bonding strength and stability in short-term slightly high-temperature storage, which can reduce poor bonding caused by two-component ratio problems and has the characteristics of high reliability of polyurethane structural adhesive. In addition, it can meet the needs of the electronic packaging field, environmental protection, low odor, and rapid fixing and bonding.

[0104] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principle of the present invention should be included in the protection scope of the present invention.

Claims

1. A heat-curing one-component polyurethane structural adhesive, characterized in that: The composition comprises the following components in parts by weight: 10-30 parts of microcapsule-sealed polyester polyol, 60-80 parts of isocyanate-terminated polymer, 5-20 parts of plasticizer, 1-5 parts of surface accelerator and 0.1-1 parts of catalyst.

2. The heat-curing one-component polyurethane structural adhesive according to claim 1, characterized in that: The isocyanate-terminated polymer comprises the following components in parts by weight: 40-60 parts of high molecular weight difunctional polyether polyol, 40-60 parts of high molecular weight trifunctional polyether polyol, 0.03-2 parts of stabilizer, 0.5-1 parts of anti-hydrolysis agent, 0.1-1 parts of defoaming agent, 10-20 parts of polyisocyanate, and 0.2-1 parts of silane coupling agent.

3. The heat-curing one-component polyurethane structural adhesive according to claim 2, characterized in that: The synthesis of the isocyanate-terminated polymer comprises the following steps: dehydrating the mixed stabilizer, anti-hydrolysis agent, defoamer, high molecular weight bifunctional polyether polyol and high molecular weight trifunctional polyether polyol, and then heating and reacting with polyisocyanate and silane coupling agent to obtain the isocyanate-terminated polymer.

4. The heat-curing one-component polyurethane structural adhesive according to claim 2 or 3, characterized in that: The high molecular weight bifunctional polyether polyol is selected from any one or more of polyether polyols having molecular weights of 2000, 6000, and 8000.

5. The heat-curing one-component polyurethane structural adhesive according to claim 2 or 3, characterized in that: The high molecular weight trifunctional polyether polyol is selected from one or both of EP330NG of Bluestar Dongda and 3600H of Shangzheng New Materials.

6. The heat-curing one-component polyurethane structural adhesive according to claim 2 or 3, characterized in that: The anti-hydrolysis agent is carbodiimide, the stabilizer is one or more of phosphoric acid or antioxidant 1010, the defoamer is one of BASFEFKA SI 2038 or Deqian 5500, the polyisocyanate is one or two of MDI, HDI, carbodiimide-modified MDI, hydrogenated MDI or PAPI, and the silane coupling agent is any one of KH550, KH602 and Maitu's A189.

7. The heat-curing one-component polyurethane structural adhesive according to claim 1, characterized in that: The microcapsules of the polyester polyol treated by microcapsule sealing are selected from Hefei Xinneng Microcapsule R1208E. The microcapsules are dehydrated before use. After the dehydration treatment, the polyol content in the polyester polyol treated by microcapsule sealing is 80%.

8. The heat-curing one-component polyurethane structural adhesive according to claim 7, characterized in that: The dehydration treatment includes air drying at room temperature for 20 days and drying in a vacuum dryer for 10 days, or low-temperature centrifugal dehydration treatment.

9. The heat-curing one-component polyurethane structural adhesive according to claim 1, characterized in that: The catalyst includes one or two of dibutyltin diisocyanate (T12), stannous octoate, and triethylenediamine; the surface promoter is selected from any one of isooctyl ether phosphate, lauryl alcohol polyoxyethylene ether phosphate or 2-hydroxyethyl methacrylate phosphate; the plasticizer is selected from any one of C5 petroleum resin, C9 petroleum resin, liquid petroleum resin PL1000s of Cologne Chemical, and EG1000 liquid petroleum resin of Ningbo Yonghua.

10. A method for preparing the heat-curing one-component polyurethane structural adhesive according to any one of claims 1 to 9, characterized in that: The method comprises the following steps: adding a surface accelerator and a plasticizer treated by molecular sieve pre-dehydration into a stirring kettle under a nitrogen atmosphere when the ambient humidity is below 40%, and after the temperature rises to 80-100°C and stabilizes for 5-10 minutes, adding an isocyanate-terminated polymer under stirring conditions, controlling the temperature to 50-55°C, adding a microcapsule-sealed polyester polyol under a nitrogen atmosphere while stirring, controlling the temperature to 50-55°C and continuing to stir until all solids are dissolved, stirring in a vacuum for 1-2 hours, finally adding a catalyst, continuing to stir in a vacuum for 0.5-2 hours, breaking the vacuum, discharging the material, and sealing and packaging to obtain a heat-curing single-component polyurethane structural adhesive.