Solvent-free two-component polyurethane structural adhesive as well as preparation method and application thereof

Abstract

The invention provides a solvent-free two-component polyurethane structural adhesive. The solvent-free two-component polyurethane structural adhesive is prepared by mixing a component A and a component B according to a volume ratio of 1: 1, the component A is prepared from the following components in parts by weight: 10 to 20 parts of high molecular weight and high functionality polyether polyol, 10 to 20 parts of low molecular weight and high functionality polyether polyol, 10 to 20 parts of random block copolymer of polycarbonate and polyether, 1 to 10 parts of chain extender, 20 to 50 parts of filler, 0.5 to 10 parts of water removal agent, 0.5 to 10 parts of thixotropic agent, 0.01 to 3 parts of pigment and 0.001 to 3 parts of catalyst; the component B is prepared from the following components in parts by weight: 20 to 50 parts of an isocyanate-terminated polyurethane prepolymer, 0 to 20 parts of isocyanate, 30 to 60 parts of filler, 0.1 to 10 parts of a water removal agent, 0.5 to 10 parts of a thixotropic agent and 0.01 to 5 parts of a silane coupling agent. The solvent-free bi-component polyurethane structural adhesive provided by the invention does not contain a solvent, is safe and environment-friendly, and is harmless to human health; the adhesive has good adhesion to different types of base materials, and is aging-resistant.

Description

Technical Field

[0001] The invention belongs to the technical field of polyurethane adhesives, and specifically relates to a solvent-free two-component polyurethane structural adhesive and a preparation method and application thereof. Background Art

[0002] Structural adhesives refer to adhesives that are used in bonding load-bearing structural parts, can withstand large dynamic loads, static loads and can be used for a long time. Structural adhesives are increasingly replacing bolts, rivets, welding and other forms to achieve effective connection of metals, plastics, etc. Structural adhesives can be mainly divided into epoxy resin structural adhesives, acrylate structural adhesives and polyurethane structural adhesives according to the type of matrix resin. Epoxy resin structural adhesives are hard and brittle, with poor toughness; acrylate structural adhesives have a strong odor, irritate the respiratory tract, and are not good for human health. Polyurethane structural adhesives, especially solvent-free polyurethane structural adhesives, are safe and environmentally friendly, with adjustable curing speed, strength and toughness, and have excellent adhesion, flexibility, low temperature resistance and other properties, and have been widely used.

[0003] With the development of lightweight in the automotive industry, composite materials such as SMC (sheet molding compound), RTM (resin transfer molding material), FRP (fiber reinforced composite material), especially SMC, are widely used in automobile manufacturing due to its high stiffness, excellent impact resistance, simple manufacturing process, low cost and other characteristics. However, the bonding of SMC often requires pre-grinding to achieve effective bonding. Pre-grinding increases production costs, pollutes the environment, and affects production efficiency. Therefore, there are many adhesives for SMC non-grinding bonding in the prior art.

[0004] The two-component polyurethane adhesive introduced in Chinese patent CN102559126B, although it realizes effective bonding of SMC without grinding, is achieved by significantly improving the body strength, which exceeds 20Mpa, sacrificing the unique toughness of polyurethane, resulting in low elongation at break and poor toughness. The two-component polyurethane adhesive introduced in Chinese patent CN111320959A, although it also realizes effective bonding of SMC without grinding, is achieved by adding organic solvents to dissolve the small molecule release agent remaining on the surface of SMC. The addition of such organic solvents is not conducive to environmental protection and harmful to human health. Summary of the invention

[0005] In view of this, the present invention provides a solvent-free two-component polyurethane structural adhesive and a preparation method and application thereof.

[0006] In order to achieve the above object, the present invention adopts the following technical solutions:

[0007] A solvent-free two-component polyurethane structural adhesive, wherein the solvent-free two-component polyurethane structural adhesive is prepared by mixing component A and component B in a volume ratio of 1:1;

[0008] The component A comprises the following components in weight: 10-20 parts of high molecular weight high functionality polyether polyol, 10-20 parts of low molecular weight high functionality polyether polyol, 10-20 parts of random block copolymer of polycarbonate and polyether, 1-10 parts of chain extender, 20-50 parts of filler, 0.5-10 parts of dewatering agent, 0.5-10 parts of thixotropic agent, 0.01-3 parts of pigment, and 0.001-3 parts of catalyst;

[0009] The component B comprises the following components in parts by weight: 20 to 50 parts of isocyanate-terminated polyurethane prepolymer, 0 to 20 parts of isocyanate, 30 to 60 parts of filler, 0.1 to 10 parts of dewatering agent, 0.5 to 10 parts of thixotropic agent, and 0.01 to 5 parts of silane coupling agent;

[0010] Wherein, the high molecular weight and high functionality polyether polyol has a molecular weight of 4000≤Mn≤15000 and a functionality ≥3;

[0011] The low molecular weight and high functionality polyether polyol has a molecular weight of 300≤Mn<4000 and a functionality ≥3;

[0012] The random block copolymer of polycarbonate and polyether has a molecular weight of 200≤Mn≤10000 and a functionality ≥2, and its main chain contains both carbonate and ether structures, wherein the carbonate structure content is ≥20%;

[0013] The isocyanate-terminated polyurethane prepolymer is obtained by reacting a polyester polyol with an isocyanate, wherein the mass content of 3-hydroxymethyl-1,5-pentanediol in the synthetic raw material of the polyester polyol is ≥30%, and the isocyanate group (NCO-) content in the isocyanate-terminated polyurethane prepolymer is 3% to 30%;

[0014] The silane coupling agent is a silane coupling agent containing an isocyanate group.

[0015] In some specific embodiments, preferably, the isocyanate group (NCO-) content in the isocyanate-terminated polyurethane prepolymer is 10% to 25%;

[0016] Furthermore, the chain extender is selected from small molecule polyols with a molecular weight Mn<300 and a functionality ≥2.

[0017] In some specific embodiments, preferably, the chain extender is selected from at least one of ethylene glycol, propylene glycol, 1,4-butanediol, neopentyl glycol, 1,6-hexanediol, glycerol, trimethylolpropane, diethylene glycol, dipropylene glycol, 2-ethyl-1,3-hexanediol, 2-butyl-2-ethyl-1,3-propanediol, 2,4-diethyl-1,5-pentanediol, and 2,2,4-trimethyl-1,3-pentanediol.

[0018] Furthermore, the fillers in the component A and the component B are respectively selected from at least one of calcium carbonate, silicon powder, barium sulfate, calcium oxide, aluminum hydroxide, aluminum oxide, and talc.

[0019] Furthermore, the dehydrating agents in the components A and B are both selected from molecular sieve powders.

[0020] Furthermore, the thixotropic agent in the component A and the component B is selected from at least one of fumed silica and organic bentonite.

[0021] Furthermore, the pigment is selected from at least one of carbon black and iron black.

[0022] Furthermore, the catalyst is selected from at least one of an organic tin catalyst and an organic bismuth catalyst.

[0023] Furthermore, the isocyanate in the isocyanate-terminated polyurethane prepolymer prepared in the component B and the separate isocyanate component are respectively selected from at least one of toluene diisocyanate, diphenylmethane diisocyanate, carbodiimide-modified diphenylmethane diisocyanate, isophorone diisocyanate, hexamethylene diisocyanate, dicyclohexylmethane diisocyanate, naphthalene diisocyanate, p-phenylene diisocyanate, 1,4-cyclohexane diisocyanate, xylene diisocyanate, cyclohexane dimethylene diisocyanate, trimethyl-1,6-hexamethylene diisocyanate, and polymethylene polyphenyl polyisocyanate.

[0024] A method for preparing the above structural adhesive comprises the following steps:

[0025] First, mix the components in component A evenly for later use;

[0026] Then, the components included in component B are mixed evenly for standby use; wherein, the method for synthesizing the isocyanate-terminated polyurethane prepolymer is to first dehydrate the polyester polyol to make the water content less than 500ppm, then add the isocyanate and mix evenly, and control the temperature between 70 and 90°C until the reaction is complete;

[0027] Finally, the A and B components are mixed evenly in a volume ratio of 1:1 to obtain the structural adhesive.

[0028] The above structural adhesives are used in the bonding of SMC, RTM, FRP, plastics and metal materials.

[0029] Compared with the prior art, the present invention has the following beneficial effects:

[0030] (1) The solvent-free two-component polyurethane structural adhesive provided by the present invention does not contain solvent, is safe and environmentally friendly, and does not harm human health.

[0031] (2) The solvent-free two-component polyurethane structural adhesive provided by the present invention has good mechanical properties, a hardness of 57 to 65 Shore D, a bulk strength of 16 to 20 MPa, and an elongation at break of 135% to 148%, achieving a balance between high strength and high flexibility.

[0032] (3) The solvent-free two-component polyurethane structural adhesive provided by the present invention has a wide range of bonding applications and has good adhesion to different types of substrates. Specifically, for materials such as SMC, plastic, and metal, direct bonding can achieve good bonding effects without the need for pretreatment such as grinding, flame, plasma, primer, and electrophoresis.

[0033] (4) The solvent-free two-component polyurethane structural adhesive provided by the present invention has excellent aging resistance, which is specifically manifested in that after aging at high temperature, high and low temperature impact, and high temperature and high humidity, the bonding strength does not decrease significantly. DETAILED DESCRIPTION

[0034] The present invention is further described in detail below in conjunction with specific embodiments so that those skilled in the art can understand the present invention more clearly.

[0035] Sources and physical and chemical parameters of key test materials:

[0036] Example 1

[0037] This embodiment provides a solvent-free two-component polyurethane structural adhesive, and its material composition and preparation method are as follows:

[0038] Component A is composed of the following array parts by weight: 15 parts of a polyether polyol with a molecular weight of Mn=7000 and a functionality of 4, 15 parts of a polyether polyol with a molecular weight of Mn=500 and a functionality of 3, 15 parts of a random block copolymer of polycarbonate and polyether with a molecular weight of Mn=3000 and a functionality of 3 (the main chain contains both carbonate and ether structures, wherein the carbonate structure content is 30%), 5 parts of DPG (dipropylene glycol), 40 parts of calcium carbonate, 5 parts of 3A molecular sieve (alkali metal aluminosilicate), 5 parts of fumed silica, 2 parts of carbon black, and 1 part of dibutyltin dilaurate.

[0039] Component B is composed of the following parts by weight: 40 parts of isocyanate-terminated polyurethane prepolymer, 10 parts of HDI (hexamethylene diisocyanate), 40 parts of calcium carbonate, 3 parts of 3A molecular sieve, 2 parts of fumed silica, and 0.5 parts of Momentive A-Link 35 silane coupling agent.

[0040] Preparation of isocyanate-terminated polyurethane prepolymer in component B: first dehydrate the polyester polyol to make the water content less than 500ppm, then add isocyanate (MDI-50) and mix evenly, and control the temperature at 80°C until the reaction is complete; wherein the (NCO-) content of the isocyanate-terminated polyurethane prepolymer is 20%, the mass content of 3-hydroxymethyl-1,5-pentanediol in the synthetic raw material of the polyester polyol is 35%, and the molecular weight of the polyester polyol is Mn=2000 and the functionality is 2.

[0041] Preparation of the structural adhesive: first, the components included in component A are mixed evenly for later use; then the components included in component B are mixed evenly for later use; finally, the evenly mixed components A and B are mixed evenly in a volume ratio of 1:1 to obtain the structural adhesive.

[0042] Example 2

[0043] This embodiment provides a solvent-free two-component polyurethane structural adhesive, whose material composition and preparation method are basically the same as those of Example 1, except that: the functionality of the random block copolymer of polycarbonate and polyether in component A is 2, and the (NCO-) content of the isocyanate-terminated polyurethane prepolymer in component B is 15%, and the rest remain unchanged.

[0044] Example 3

[0045] This embodiment provides a solvent-free two-component polyurethane structural adhesive, and its material composition and preparation method are basically the same as those of Example 1, except that: the molecular weight of the polyester polyol in the raw material for preparing the isocyanate-terminated polyurethane prepolymer in component B is Mn=4000, and the rest remains unchanged.

[0046] Example 4

[0047] This embodiment provides a solvent-free two-component polyurethane structural adhesive, whose material composition and preparation method are basically the same as those of Example 1, except that: the functionality of the random block copolymer of polycarbonate and polyether in component A is 2, the (NCO-) content of the isocyanate-terminated polyurethane prepolymer in component B is 15%, and the molecular weight of the polyester polyol in the raw material for preparing the isocyanate-terminated polyurethane prepolymer is Mn=4000, and the rest remain unchanged.

[0048] Example 5

[0049] This embodiment provides a solvent-free two-component polyurethane structural adhesive, and its material composition and preparation method are as follows:

[0050] Component A is composed of the following array parts by weight: 20 parts of a polyether polyol with a molecular weight of Mn=5000 and a functionality of 3, 10 parts of a polyether polyol with a molecular weight of Mn=3500 and a functionality of 3, 20 parts of a random block copolymer of polycarbonate and polyether with a molecular weight of Mn=400 and a functionality of 3 (the main chain contains both carbonate and ether structures, wherein the carbonate structure content is 80%), 1 part of ethylene glycol, 50 parts of aluminum hydroxide, 1 part of 3A molecular sieve (alkali metal aluminosilicate), 10 parts of organic bentonite, 0.5 parts of iron black, and 3 parts of bismuth laurate.

[0051] Component B is composed of the following parts by weight: 20 parts of isocyanate-terminated polyurethane prepolymer, 20 parts of toluene diisocyanate, 30 parts of calcium oxide, 10 parts of 3A molecular sieve, 0.5 parts of fumed silica, and 5 parts of Momentive A-Link 35 silane coupling agent.

[0052] The preparation of the isocyanate-terminated polyurethane prepolymer in component B is the same as in Example 1.

[0053] The method for preparing the structural adhesive is the same as that in Example 1.

[0054] Example 6

[0055] This embodiment provides a solvent-free two-component polyurethane structural adhesive, and its material composition and preparation method are as follows:

[0056] Component A is composed of the following array parts by weight: 10 parts of a polyether polyol with a molecular weight of Mn=13000 and a functionality of 4, 20 parts of a polyether polyol with a molecular weight of Mn=300 and a functionality of 3, 10 parts of a random block copolymer of polycarbonate and polyether with a molecular weight of Mn=8000 and a functionality of 3 (the main chain contains both carbonate and ether structures, wherein the carbonate structure content is 20%), 10 parts of DPG (dipropylene glycol), 20 parts of calcium carbonate, 10 parts of 3A molecular sieve (alkali metal aluminosilicate), 1 part of fumed silica, 3 parts of carbon black, and 0.5 parts of dibutyltin dilaurate.

[0057] Component B is composed of the following parts by weight: 50 parts of isocyanate-terminated polyurethane prepolymer, 5 parts of HDI (hexamethylene diisocyanate), 60 parts of calcium carbonate, 0.5 parts of 3A molecular sieve, 10 parts of fumed silica, and 1 part of Momentive A-Link 35 silane coupling agent.

[0058] The preparation of the isocyanate-terminated polyurethane prepolymer in component B is the same as in Example 1.

[0059] The method for preparing the structural adhesive is the same as that in Example 1.

[0060] Comparative Example 1

[0061] This comparative example provides a solvent-free two-component polyurethane structural adhesive, whose material composition and preparation method are basically the same as those of Example 1, except that the random block copolymer of polycarbonate and polyether is removed from component A, and the rest remain unchanged.

[0062] Comparative Example 2

[0063] This comparative example provides a solvent-free two-component polyurethane structural adhesive, whose material composition and preparation method are basically the same as those of Example 1, except that the carbonate structure content in the random block copolymer of polycarbonate and polyether in component A is 10%, and the rest remains unchanged.

[0064] Comparative Example 3

[0065] This comparative example provides a solvent-free two-component polyurethane structural adhesive, whose material composition and preparation method are basically the same as those of Example 1, except that: the low molecular weight and high functionality polyether polyol (Mn=500, functionality is 3) in component A is replaced by an equal amount of high molecular weight and high functionality polyether polyol (Mn=7000, functionality is 4), and the rest remain unchanged.

[0066] Comparative Example 4

[0067] This comparative example provides a solvent-free two-component polyurethane structural adhesive, whose material composition and preparation method are basically the same as those of Example 1, except that: the high molecular weight and high functionality polyether polyol (Mn=7000, functionality is 4) in component A is replaced by an equal amount of low molecular weight and high functionality polyether polyol (Mn=500, functionality is 3), and the rest remain unchanged.

[0068] Comparative Example 5

[0069] This comparative example provides a solvent-free two-component polyurethane structural adhesive, whose material composition and preparation method are basically the same as those of Example 1, except that: the Maitu A-Link 35 silane coupling agent in component B is replaced by an equal amount of KH560 silane coupling agent, and the rest remain unchanged.

[0070] Comparative Example 6

[0071] This comparative example provides a solvent-free two-component polyurethane structural adhesive, whose material composition and preparation method are basically the same as those of Example 1, except that the polyester polyol in the raw material for preparing the isocyanate-terminated polyurethane prepolymer in component B is replaced by a polyether polyol of equal amount, molecular weight and functionality, and the rest remains unchanged.

[0072] Comparative Example 7

[0073] This comparative example provides a solvent-free two-component polyurethane structural adhesive, whose material composition and preparation method are basically the same as those of Example 1, except that the mass content of 3-hydroxymethyl-1,5-pentanediol in the raw material of the polyester polyol used to prepare the isocyanate-terminated polyurethane prepolymer in component B is 15%, and the rest remains unchanged.

[0074] Furthermore, in order to understand the specific performance of the polyurethane structural adhesives prepared in the above embodiments and comparative examples, the following tests were also conducted.

[0075] The mechanical properties test results of the polyurethane structural adhesive are shown in Table 1.

[0076] Table 1 Mechanical properties of various polyurethane structural adhesives

[0077]

[0078]

[0079] The test results of the bonding performance of the polyurethane structural adhesive are shown in Table 2. The polyurethane structural adhesive prepared in the above embodiments and comparative examples is directly coated on a substrate and pressed, and the substrate is not subjected to any pretreatment such as grinding, flame, plasma, primer and electrophoresis, and after being completely cured, a tensile shear strength test is performed.

[0080] Table 2 Bonding strength of various polyurethane structural adhesives

[0081]

[0082] Furthermore, in order to understand the anti-aging performance of the above polyurethane structural adhesives, the tensile shear specimens prepared by the same method as above were aged respectively, and the specific aging conditions were as follows:

[0083] 1. High temperature aging: 85℃ for 300 hours;

[0084] 2. High and low temperature impact aging: -40~85℃ cycle 300 times;

[0085] 3. High temperature and high humidity aging: 85°C, RH=85% for 300 hours.

[0086] After the aging treatment, the samples were taken out and placed at room temperature for 24 hours, and then the tensile shear strength test was performed. The results are shown in Table 3.

[0087] Table 3 Adhesion strength of various polyurethane structural adhesives after aging

[0088]

[0089] From the experimental results in Table 1, Table 2 and Table 3, it can be seen that the polyurethane structural adhesive provided by Examples 1-6 shows higher hardness, bulk strength and elongation at break than Comparative Examples 1-7; it can be directly bonded to different types of substrates without treatment, and the bonding effect is excellent. Specifically, it is manifested in higher bonding strength, better failure mode, that is, substrate destruction or colloid cohesive destruction or substrate fracture, rather than interface destruction, and has excellent anti-aging performance.

[0090] The present invention prepares a solvent-free two-component polyurethane structural adhesive by compounding high-functionality polyether polyols with high and low molecular weights, adding random block copolymers of polycarbonate and polyether, polyurethane prepolymers prepared with polyester polyols containing 3-hydroxymethyl-1,5-pentanediol and isocyanate, and silane coupling agents containing isocyanate groups, and reasonably matching with other components. The structural adhesive can directly bond different types of substrates without treatment, and the bonding effect is excellent. Specifically, it is manifested in higher bonding strength, better failure mode, that is, substrate destruction or colloid cohesive destruction or substrate fracture, rather than interface destruction, and has excellent anti-aging performance.

[0091] The raw materials not specifically described in the present invention are all existing materials and can be directly purchased from the market.

[0092] The above are only preferred embodiments of the present invention and are not intended to limit the protection scope of the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention should be included in the protection scope of the present invention.

Claims

1. A solvent-free two-component polyurethane structural adhesive, characterized in that: The solvent-free two-component polyurethane structural adhesive is prepared by mixing component A and component B in a volume ratio of 1:1; The component A comprises the following components in weight: 10-20 parts of high molecular weight high functionality polyether polyol, 10-20 parts of low molecular weight high functionality polyether polyol, 10-20 parts of random block copolymer of polycarbonate and polyether, 1-10 parts of chain extender, 20-50 parts of filler, 0.5-10 parts of dewatering agent, 0.5-10 parts of thixotropic agent, 0.01-3 parts of pigment, and 0.001-3 parts of catalyst; The component B comprises the following components in parts by weight: 20 to 50 parts of isocyanate-terminated polyurethane prepolymer, 0 to 20 parts of isocyanate, 30 to 60 parts of filler, 0.1 to 10 parts of dewatering agent, 0.5 to 10 parts of thixotropic agent, and 0.01 to 5 parts of silane coupling agent; Wherein, the high molecular weight and high functionality polyether polyol has a molecular weight of 4000≤Mn≤15000 and a functionality ≥3; The low molecular weight and high functionality polyether polyol has a molecular weight of 300≤Mn<4000 and a functionality ≥3; The random block copolymer of polycarbonate and polyether has a molecular weight of 200≤Mn≤10000 and a functionality ≥2, and its main chain contains both carbonate and ether structures, wherein the carbonate structure content is ≥20%; The isocyanate-terminated polyurethane prepolymer is obtained by reacting polyester polyol with isocyanate, wherein the mass content of 3-hydroxymethyl-1,5-pentanediol in the synthetic raw material of polyester polyol is ≥30%, and the isocyanate content of the isocyanate-terminated polyurethane prepolymer is 3% to 30%; The silane coupling agent is a silane coupling agent containing an isocyanate group.

2. The structural adhesive according to claim 1, characterized in that: The chain extender is selected from small molecule polyols with a molecular weight Mn of less than 300 and a functionality of ≥2.

3. The structural adhesive according to claim 1, characterized in that: The fillers in the components A and B are respectively selected from at least one of calcium carbonate, silicon powder, barium sulfate, calcium oxide, aluminum hydroxide, aluminum oxide and talc.

4. The structural adhesive according to claim 1, characterized in that: The dehydrating agents in the components A and B are both selected from molecular sieve powder.

5. The structural adhesive according to claim 1, characterized in that: The thixotropic agent in the component A and the component B is selected from at least one of fumed silica and organic bentonite.

6. The structural adhesive according to claim 1, characterized in that: The pigment is selected from at least one of carbon black and iron black.

7. The structural adhesive according to claim 1, characterized in that: The catalyst is selected from at least one of an organic tin catalyst and an organic bismuth catalyst.

8. The structural adhesive according to claim 1, characterized in that: The isocyanate in the isocyanate-terminated polyurethane prepolymer prepared in the component B and the separate isocyanate component are respectively selected from at least one of toluene diisocyanate, diphenylmethane diisocyanate, carbodiimide-modified diphenylmethane diisocyanate, isophorone diisocyanate, hexamethylene diisocyanate, dicyclohexylmethane diisocyanate, naphthalene diisocyanate, p-phenylene diisocyanate, 1,4-cyclohexane diisocyanate, xylene diisocyanate, cyclohexane dimethylene diisocyanate, trimethyl-1,6-hexamethylene diisocyanate, and polymethylene polyphenyl polyisocyanate.

9. A method for preparing the structural adhesive according to any one of claims 1 to 8, characterized in that: The following steps are involved: First, mix the components in component A evenly for later use; Then, the components included in component B are mixed evenly for standby use; wherein, the method for synthesizing the isocyanate-terminated polyurethane prepolymer is to first dehydrate the polyester polyol to make the water content less than 500ppm, then add the isocyanate and mix evenly, and control the temperature between 70 and 90°C until the reaction is complete; Finally, the A and B components are mixed evenly in a volume ratio of 1:1 to obtain the structural adhesive.

10. Use of the structural adhesive according to any one of claims 1 to 8 in bonding SMC, RTM, FRP, plastics and metal materials.

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