Coating type modified hot melt adhesive, preparation method thereof and application of coating type modified hot melt adhesive in PEI bonding aluminum material

Abstract

The invention discloses a coating type modified hot melt adhesive, a preparation method of the coating type modified hot melt adhesive and application of the coating type modified hot melt adhesive in PEI bonding aluminum materials, and belongs to the technical field of new chemical materials. Comprising the following raw materials in parts by weight: 15-25 parts of a polyurethane adhesive, 45-55 parts of an epoxy modified polyurethane prepolymer, 2-6 parts of a closed curing agent, 1-5 parts of graphene, 5-10 parts of an adhesive, 1-3 parts of a heat stabilizer and 5-10 parts of nitrile rubber. And the effect of still maintaining a stable bonding state under the extreme temperature change is ensured.

Description

Technical Field

[0001] The invention relates to the technical field of new chemical materials, and in particular to a coatable modified hot melt adhesive and a preparation method thereof, and application thereof in PEI bonding aluminum materials. Background Art

[0002] Currently, high-performance engineering plastics such as polyetherimide (PEI) are widely used in the fields of electronics and aerospace due to their excellent high temperature resistance, wear resistance and insulation properties. However, the bonding of polyetherimide to metal parts such as aluminum plates has always been an industry problem. The reason is that both polyetherimide and aluminum are chemically very stable substances and are not easy to react chemically with other chemicals. In addition, existing hot melt adhesives are difficult to form sufficient adhesion, resulting in the risk of peeling of components formed by bonding polyetherimide and aluminum in extreme environments (minus 40℃-160℃).

[0003] The existing method for reducing the risk of peeling between polyetherimide and aluminum is to increase the content of hot melt adhesive, which not only leads to increased processing costs, but also slows down the curing speed of polyetherimide and aluminum, and cannot fundamentally improve the bonding stability between polyetherimide and aluminum. Summary of the invention

[0004] In order to solve the problems in the prior art, the present invention provides a coatable modified hot melt adhesive and a preparation method thereof and an application in PEI bonding aluminum, which can establish a stronger bonding force between polyetherimide and aluminum, ensuring that they still maintain a stable bonding state under extreme temperature changes.

[0005] The first aspect of the present invention provides a coatable modified hot melt adhesive, which adopts the following technical solution: A coatable modified hot melt adhesive comprises the following raw materials in parts by weight: 15-25 parts of a polyurethane adhesive, 45-55 parts of an epoxy-modified polyurethane prepolymer, 2-6 parts of a closed curing agent, 1-5 parts of graphene, 5-10 parts of an adhesive, 1-3 parts of a heat stabilizer, and 5-10 parts of nitrile rubber.

[0006] By adopting the above technical scheme, the present application effectively improves the adhesion between PEI and aluminum by adding epoxy-modified polyurethane prepolymer, adhesive and nitrile rubber to the polyurethane adhesive, and can maintain a stable bonding state even under reflow soldering. The addition of thermal stabilizer ensures the stable performance of the hot melt adhesive in a high temperature environment, and can work in a wider temperature range without performance degradation, thereby ensuring the stability of the bonding between PEI and aluminum at high temperatures. At the same time, the combination of nitrile rubber and epoxy-modified polyurethane prepolymer also effectively improves the processing performance and impact resistance of the hot melt adhesive. The addition of graphene as a functional filler not only improves the flame retardant properties of the hot melt adhesive, but also improves the mechanical strength of the hot melt adhesive after curing by combining it with epoxy-modified polyurethane prepolymer and nitrile rubber.

[0007] Preferably, the epoxy-modified polyurethane prepolymer is prepared by mixing a polyurethane prepolymer with an epoxy resin under a nitrogen atmosphere, reacting the mixture at a temperature of 80-85° C. with the addition of a catalyst, and then vacuum degassing the mixture to obtain the epoxy-modified polyurethane prepolymer.

[0008] Preferably, the weight ratio of the epoxy resin to the polyurethane prepolymer is 10:(2-8).

[0009] By adopting the above technical scheme, in the present application, the reaction temperature is controlled within the range of 80-85°C, so that the -NCO in the polyurethane prepolymer reacts with the secondary -OH group in the epoxy resin, thereby effectively improving the bonding performance and impact strength of the modified hot melt adhesive. Moreover, as the content of the polyurethane prepolymer increases, the proportion of flexible segments in the epoxy-modified polyurethane prepolymer increases, and the impact resistance improves. When the weight ratio of the epoxy resin to the polyurethane prepolymer exceeds 10:8, the epoxy-modified polyurethane prepolymer will cause the hardness of the modified hot melt adhesive to be greatly reduced. Therefore, in the present application, the epoxy-modified polyurethane prepolymer effectively improves the bonding performance of the modified hot melt adhesive by controlling the temperature and material ratio of the reaction of the epoxy resin and the polyurethane prepolymer.

[0010] Preferably, the adhesive is an ethylene copolymer containing epoxy groups.

[0011] Preferably, the epoxy group-containing ethylene copolymer is prepared by mixing styrene, cyclohexane and tetrahydrofuran under argon protection, stirring and cooling to 0°C, adding n-butyl lithium and reacting at room temperature for 1 hour, then adding glycidyl methacrylate and reacting at a temperature of 10-15°C for 2 hours, filtering and drying to obtain the epoxy group-containing ethylene copolymer.

[0012] By adopting the above technical solution, when the adhesive is an ethylene copolymer containing epoxy groups, it can be combined with epoxy-modified polyurethane prepolymer to achieve chemical bonding with the surface of the substrate, effectively ensuring the bonding strength of the hot melt adhesive.

[0013] Preferably, the weight ratio of styrene to cyclohexane, tetrahydrofuran, n-butyl lithium and glycidyl methacrylate is 0.5:1:2.5:0.8:1.

[0014] Preferably, the particle size of the graphene is less than 1 μm.

[0015] Preferably, the thermal stabilizer is nano magnesium oxide.

[0016] By adopting the above technical solution, when nano magnesium oxide is selected as the heat stabilizer, the oxidation reaction of the modified hot melt adhesive at high temperature can be effectively inhibited, thereby ensuring the bonding strength of the modified hot melt adhesive to PEI and aluminum at high temperature and extending the service life of the modified hot melt adhesive.

[0017] Preferably, the nitrile rubber is hydroxy-terminated nitrile rubber.

[0018] The second aspect of the present invention is to provide a method for preparing the coatable modified hot melt adhesive as described above, comprising the following steps: mixing a polyurethane adhesive with an epoxy-modified polyurethane prepolymer to form a premix, then adding nitrile rubber and graphene and stirring and dispersing them evenly, and then adding an adhesive, a heat stabilizer, and a closed curing agent and stirring to obtain a modified hot melt adhesive.

[0019] The third aspect of the present invention is to provide the use of the modified hot melt adhesive obtained above in PEI bonding aluminum materials.

[0020] In summary, the present invention has the following beneficial effects: the present application introduces epoxy-modified polyurethane prepolymer, nitrile rubber, and adhesive into the polyurethane adhesive to improve the adhesion and impact resistance of the hot melt adhesive with PEI and aluminum. At the same time, by introducing a high-temperature resistant epoxy group into the hot melt adhesive, the stability of the hot melt adhesive at high temperatures is increased, and the risk of peeling between PEI and aluminum at high temperatures is reduced. At the same time, the addition of the epoxy group increases the reaction activity between the raw materials, so that the modified hot melt adhesive has strong adhesion to PEI and aluminum.

[0021] In addition, when the adhesive is an ethylene copolymer containing epoxy groups, it can not only strengthen the bonding strength between PEI and aluminum, but also improve the durability of the hot melt adhesive. Therefore, the modified hot melt adhesive obtained by the combination of various raw materials in the present application has good bonding strength, high temperature stability, and impact resistance, and due to the addition of the closed curing agent, the storage stability of the modified hot melt adhesive is also improved. DETAILED DESCRIPTION

[0022] The present invention is further described in detail below with reference to the embodiments.

[0023] A coatable modified hot melt adhesive comprises the following raw materials in parts by weight: 15-25 parts of a polyurethane adhesive, 45-55 parts of an epoxy-modified polyurethane prepolymer, 2-6 parts of a closed curing agent, 1-5 parts of graphene, 5-10 parts of an adhesive, 1-3 parts of a heat stabilizer, and 5-10 parts of nitrile rubber.

[0024] Preferably, the epoxy-modified polyurethane prepolymer is prepared by mixing a polyurethane prepolymer with an epoxy resin under a nitrogen atmosphere, reacting the mixture at a temperature of 80-85° C. with the addition of a catalyst, and then vacuum degassing the mixture to obtain the epoxy-modified polyurethane prepolymer.

[0025] Preferably, the weight ratio of the epoxy resin to the polyurethane prepolymer is 10:(2-8).

[0026] Preferably, the adhesive is an ethylene copolymer containing epoxy groups.

[0027] Preferably, the epoxy group-containing ethylene copolymer is prepared by mixing styrene, cyclohexane and tetrahydrofuran under argon protection, stirring and cooling to 0°C, adding n-butyl lithium and reacting at room temperature for 1 hour, then adding glycidyl methacrylate and reacting at a temperature of 10-15°C for 2 hours, filtering and drying to obtain the epoxy group-containing ethylene copolymer.

[0028] Preferably, the weight ratio of styrene to cyclohexane, tetrahydrofuran, n-butyl lithium and glycidyl methacrylate is 0.5:1:2.5:0.8:1.

[0029] Preferably, the particle size of the graphene is less than 1 μm.

[0030] Preferably, the thermal stabilizer is nano magnesium oxide.

[0031] Preferably, the nitrile rubber is hydroxy-terminated nitrile rubber.

[0032] The second aspect of the present invention is to provide a method for preparing the coatable modified hot melt adhesive as described above, comprising the following steps: mixing a polyurethane adhesive with an epoxy-modified polyurethane prepolymer to form a premix, then adding nitrile rubber and graphene and stirring and dispersing them evenly, and then adding an adhesive, a heat stabilizer, and a closed curing agent and stirring to obtain a modified hot melt adhesive.

[0033] Unless otherwise specified, the raw materials used in this application are commercially available.

[0034] Preparation Example 1.1 The preparation method of epoxy modified polyurethane prepolymer comprises the following steps: Under a nitrogen atmosphere, the vacuum-dehydrated epoxy resin was added to the polyurethane prepolymer at a weight ratio of 10:2, and 0.5% of dibutyltin dilaurate by weight of the epoxy resin was added dropwise. After reacting at 80-85°C for 2h, the epoxy-modified polyurethane prepolymer was vacuum-degassed for 0.5h to obtain the epoxy-modified polyurethane prepolymer, wherein the performance parameters of the polyurethane prepolymer are: NCO content of 6.3±0.2%, viscosity of 500±100mPa·s at 80°C, and appearance of a colorless, transparent, viscous liquid at room temperature.

[0035] Preparation Example 1.2 The preparation method of epoxy modified polyurethane prepolymer comprises the following steps: Under a nitrogen atmosphere, the vacuum-dehydrated epoxy resin was added to the polyurethane prepolymer at a weight ratio of 10:5, and 0.5% of dibutyltin dilaurate by weight of the epoxy resin was added dropwise. After reacting at 80-85°C for 2h, the epoxy-modified polyurethane prepolymer was vacuum-degassed for 0.5h to obtain the epoxy-modified polyurethane prepolymer, wherein the performance parameters of the polyurethane prepolymer are: NCO content of 6.3±0.2%, viscosity of 500±100mPa·s at 80°C, and appearance of a colorless, transparent, viscous liquid at room temperature.

[0036] Preparation Example 1.3 The preparation method of epoxy modified polyurethane prepolymer comprises the following steps: Under a nitrogen atmosphere, the vacuum-dehydrated epoxy resin was added to the polyurethane prepolymer at a weight ratio of 10:8, and 0.5% of dibutyltin dilaurate by weight of the epoxy resin was added dropwise. After reacting at 80-85°C for 2h, the epoxy-modified polyurethane prepolymer was vacuum-degassed for 0.5h to obtain the epoxy-modified polyurethane prepolymer, wherein the performance parameters of the polyurethane prepolymer are: NCO content of 6.3±0.2%, viscosity of 500±100mPa·s at 80°C, and appearance of a colorless, transparent, viscous liquid at room temperature.

[0037] Preparation Example 2 The preparation method of the ethylene copolymer containing epoxy group comprises the following steps: Under nitrogen protection, styrene, cyclohexane and tetrahydrofuran are mixed and stirred according to a weight ratio of styrene to cyclohexane, tetrahydrofuran, n-butyl lithium and glycidyl methacrylate of 0.5:1:2.5:0.8:1, and then cooled to 0°C. Then n-butyl lithium is added, stirred and reacted at room temperature for 1 hour, and then glycidyl methacrylate is added and reacted at a temperature of 10-15°C for 2 hours. Then a small amount of methanol is added to terminate the reaction, and finally the polymer is precipitated in anhydrous ethanol, filtered out, and dried in a vacuum drying oven at 50°C to constant weight to obtain an ethylene copolymer containing epoxy groups.

[0038] Example 1 A method for preparing a coatable modified hot melt adhesive comprises the following steps: 1.5 kg of a polyurethane adhesive and 4.5 kg of an epoxy-modified polyurethane prepolymer obtained in Preparation Example 1.1 are stirred and mixed at a temperature of 130 ± 5 ° C to form a premix, and then 0.5 kg of terminal hydroxyl nitrile rubber and 0.1 kg of graphene with a particle size of <1 μm are added at this temperature and stirred and dispersed evenly, and then 0.5 kg of an ethylene copolymer containing epoxy groups obtained in Preparation Example 2, 0.1 kg of nano magnesium oxide, and 0.2 kg of a blocked isocyanate curing agent are added and stirred for 50 minutes to obtain a modified hot melt adhesive, wherein the technical indicators of the blocked isocyanate curing agent are: solid content 75 ± 0.5%, viscosity 300 ± 100 mPa·s, unblocking temperature ≥ 110 ° C, and flash point 45 ° C.

[0039] Example 2 A method for preparing a coatable modified hot melt adhesive comprises the following steps: stirring and mixing 2.0 kg of a polyurethane adhesive and 5.0 kg of an epoxy-modified polyurethane prepolymer obtained in Preparation Example 1.1 at a temperature of 130±5°C to form a premix, then adding 0.8 kg of terminal hydroxyl nitrile rubber and 0.3 kg of graphene with a particle size of <1 μm at this temperature and stirring and dispersing them uniformly, then adding 0.8 kg of an ethylene copolymer containing epoxy groups obtained in Preparation Example 2, 0.2 kg of nano magnesium oxide, and 0.4 kg of a blocked isocyanate curing agent and stirring for 50 minutes to obtain a modified hot melt adhesive, wherein the technical indicators of the blocked isocyanate curing agent are: solid content 75±0.5%, viscosity 300±100 mPa·s, unblocking temperature ≥110°C, and flash point 45°C.

[0040] Example 3 A method for preparing a coatable modified hot melt adhesive comprises the following steps: stirring and mixing 2.5 kg of a polyurethane adhesive and 5.5 kg of an epoxy-modified polyurethane prepolymer obtained in Preparation Example 1.1 at a temperature of 130 ± 5 ° C to form a premix, then adding 1.0 kg of terminal hydroxyl nitrile rubber and 0.5 kg of graphene with a particle size of <1 μm at this temperature and stirring and dispersing them uniformly, then adding 1.0 kg of an ethylene copolymer containing epoxy groups obtained in Preparation Example 2, 0.3 kg of nano magnesium oxide, and 0.6 kg of a blocked isocyanate curing agent and stirring for 50 minutes to obtain a modified hot melt adhesive, wherein the technical indicators of the blocked isocyanate curing agent are: solid content 75 ± 0.5%, viscosity 300 ± 100 mPa·s, unblocking temperature ≥ 110 ° C, and flash point 45 ° C.

[0041] Example 4 A method for preparing a coatable modified hot melt adhesive is different from Example 2 in that the epoxy-modified polyurethane prepolymer uses the epoxy-modified polyurethane prepolymer obtained in Preparation Example 1.2, and the other uniformities are the same as Example 2.

[0042] Example 5 A method for preparing a coatable modified hot melt adhesive is different from Example 2 in that the epoxy-modified polyurethane prepolymer uses the epoxy-modified polyurethane prepolymer obtained in Preparation Example 1.3, and the other uniformities are the same as Example 2.

[0043] Comparative Example 1 A method for preparing a coatable modified hot melt adhesive is different from that of Example 2 in that the raw materials do not contain an ethylene copolymer adhesive containing epoxy groups, and the rest are the same as those of Example 2.

[0044] Comparative Example 2 A method for preparing a coatable modified hot melt adhesive is different from that of Example 2 in that the raw material contains terminal hydroxylated nitrile rubber, and the rest is the same as that of Example 2.

[0045] Comparative Example 3 A method for preparing a coatable modified hot melt adhesive, which is different from Example 2 in that there is no graphene in the raw materials, and the rest is the same as Example 2.

[0046] Comparative Example 4 A method for preparing a coatable modified hot melt adhesive is different from that of Example 2 in that the raw material does not contain heat stabilizer nano magnesium oxide, and the rest is the same as that of Example 2.

[0047] Performance Testing The hot melt adhesive obtained in the above embodiments and comparative examples was coated on PEI, rolled up, and then hot pressed on aluminum at 150±5°C to achieve bonding between PEI and aluminum. The bonding performance between PEI and aluminum was then tested, and the test results are shown in Table 1.

[0048] Table 1 Hot melt adhesive test results Note: 200℃ peel strength is measured after the samples are kept at 200℃ for 2 hours, and 350℃ peel strength is measured after the samples are kept at 350℃ for 60 seconds.

[0049] From Table 1 above, we can see that: The modified hot melt adhesive obtained in Examples 1-3 of the present application can effectively bond PEI and aluminum at a high temperature of 200°C, and can last for 60 seconds at a high temperature of 350°C, indicating that the modified hot melt adhesive obtained in the present application still has stable bonding ability to PEI and aluminum at high temperatures, and can effectively reduce the risk of peeling between PEI and aluminum at high temperatures.

[0050] Compared with Example 2, when the epoxy-modified polyurethane prepolymer is used in the hot melt adhesive with the increase of the polyurethane prepolymer content in Example 4-5, the peel strength of the modified hot melt adhesive obtained in Example 4-5 at room temperature is significantly improved, and the peel strength at 200°C and 350°C is also significantly improved compared with Example 2, indicating that the increase in the polyurethane prepolymer content in the epoxy-modified polyurethane prepolymer of the present application can further improve the bonding performance of the modified hot melt adhesive.

[0051] Compared with Example 2, when the raw materials lack the ethylene copolymer containing epoxy groups, the bonding strength of the modified hot melt adhesive obtained in Comparative Example 1 at both room temperature and high temperature is significantly reduced compared with that in Example 2, indicating that the addition of the ethylene copolymer containing epoxy groups in the hot melt adhesive can increase the reaction activity of the modified hot melt adhesive, thereby improving the chemical bonding ability between the modified hot melt adhesive and the substrate.

[0052] Compared with Example 2, when the raw materials lack end-hydroxylated nitrile rubber or graphene or heat stabilizer nano magnesium oxide, the peel strength of the modified hot melt adhesive obtained in Comparative Examples 2-4 at room temperature and high temperature is significantly reduced. It can be seen that the combined use of the raw materials in the present application can effectively improve the bonding performance of the hot melt adhesive to PEI and aluminum.

[0053] The embodiments of this specific implementation method are all preferred embodiments of the present invention, and are not intended to limit the protection scope of the present invention. Therefore, any equivalent changes made based on the structure, shape, and principle of the present invention should be included in the protection scope of the present invention.

Claims

1. A coatable modified hot melt adhesive, characterized in that: The invention comprises the following raw materials in parts by weight: 15-25 parts of polyurethane adhesive, 45-55 parts of epoxy modified polyurethane prepolymer, 2-6 parts of closed curing agent, 1-5 parts of graphene, 5-10 parts of adhesive, 1-3 parts of heat stabilizer and 5-10 parts of nitrile rubber.

2. The coatable modified hot melt adhesive according to claim 1, characterized in that: The epoxy-modified polyurethane prepolymer is prepared by mixing the polyurethane prepolymer with epoxy resin under a nitrogen atmosphere, reacting the mixture at a temperature of 80-85° C. with the addition of a catalyst, and then vacuum degassing the mixture to obtain the epoxy-modified polyurethane prepolymer.

3. The coatable modified hot melt adhesive according to claim 2, characterized in that: The weight ratio of the epoxy resin to the polyurethane prepolymer is 10:(2-8).

4. The coatable modified hot melt adhesive according to claim 1, characterized in that: The adhesive is an ethylene copolymer containing epoxy groups.

5. The coatable modified hot melt adhesive according to claim 4, characterized in that: The epoxy group-containing ethylene copolymer is prepared by mixing styrene, cyclohexane and tetrahydrofuran under argon protection, stirring and cooling to 0°C, adding n-butyl lithium and reacting at room temperature for 1 hour, then adding glycidyl methacrylate and reacting at a temperature of 10-15°C for 2 hours, filtering and drying to obtain the epoxy group-containing ethylene copolymer.

6. The coatable modified hot melt adhesive according to claim 5, characterized in that: The weight ratio of the styrene to cyclohexane, tetrahydrofuran, n-butyl lithium and glycidyl methacrylate is 0.5:1:2.5:0.8:

1.

7. The coatable modified hot melt adhesive according to claim 1, characterized in that: The particle size of the graphene is less than 1 μm.

8. The coatable modified hot melt adhesive according to claim 1, characterized in that: The heat stabilizer is nano magnesium oxide, and the nitrile rubber is hydroxy-terminated nitrile rubber.

9. A method for preparing the coatable modified hot melt adhesive according to any one of claims 1 to 8, characterized in that: The method comprises the following steps: mixing a polyurethane adhesive with an epoxy modified polyurethane prepolymer to form a premix, then adding nitrile rubber and graphene and stirring and dispersing them uniformly, and then adding an adhesive, a heat stabilizer and a closed curing agent and stirring to obtain a modified hot melt adhesive.

10. Use of the modified hot melt adhesive obtained as claimed in claim 9 in PEI bonding aluminum materials.

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