Epoxy adhesive as well as preparation method and application thereof

Abstract

The invention discloses an epoxy adhesive as well as a preparation method and application thereof. The adhesive comprises bisphenol A epoxy resin, liquid rubber, an amine curing agent and a filler, the amine curing agent consists of a polyamide curing agent and an alicyclic amine curing agent. Based on the synergistic effect of the components, the adhesive not only can realize low-temperature rapid curing, but also has better strength and toughness, is used for bonding a PMI foam board and a composite material skin, has excellent high and low temperature performance after bonding, is high in peel strength retention rate, reduces the swelling risk, and has a wider application range.

Description

Technical Field

[0001] The invention relates to an epoxy adhesive, in particular to a low-viscosity, low-temperature, fast-curing, solvent-free epoxy adhesive, and also to a preparation method and application thereof, belonging to the technical field of adhesives. Background Art

[0002] Epoxy adhesives are widely used in construction, automobile and other fields. Epoxy adhesives can be used to bond metal, wood and composite materials.

[0003] The epoxy adhesive ZJ-3 commonly used in the military field in the prior art adds a large amount of powder filler to increase the bonding strength. During construction, the adhesive has a high viscosity and is not easy to be evenly applied, resulting in unstable product quality and heavy parts. In addition, it has low heat resistance, poor impact resistance and low mechanical properties and cannot be used to bond PMI foam core materials and composite skins. Summary of the invention

[0004] In view of the above-mentioned technical problems existing in the epoxy adhesive ZJ-3 in the prior art, the first object of the present invention is to provide a low-viscosity, low-temperature, fast-curing, solvent-free epoxy adhesive. Based on the synergistic effect between the components, the adhesive not only achieves low-temperature curing, but also the heat resistance of the colloid after heating and curing for 1 hour reaches 100°C, and the adhesive strength can be quickly formed. Moreover, after bonding, it has excellent high and low temperature performance, high peel strength retention rate, and reduced bulging risk. It has a wider range of applications and can overcome the technical problems brought about by the use of the epoxy adhesive ZJ-3.

[0005] The second object of the present invention is to provide a method for preparing an epoxy adhesive, which has simple process, mild conditions, is green and environmentally friendly, does not require the addition of solvents during the entire preparation process, and the obtained product has high purity.

[0006] The third object of the present invention is to provide an application of an epoxy adhesive, which is used to bond PMI foam and glass fiber composite material skin, can achieve low-temperature rapid curing and molding, and has high final bonding strength, with a peel strength of up to 1.05N / cm, good high and low temperature performance, and reduces the risk of blistering.

[0007] In order to achieve the above technical objectives, the present invention provides an epoxy adhesive, which comprises bisphenol A epoxy resin, liquid rubber, an amine curing agent and a filler; the amine curing agent is composed of a polyamide curing agent and an alicyclic amine curing agent.

[0008] The amine curing agent used in the epoxy adhesive of the present invention is composed of a polyamide curing agent and an alicyclic amine curing agent. The two amine curing agents have a synergistic effect, can ensure that the epoxy resin is quickly cured at a low temperature, and can give it a higher bonding strength in a short time, and can improve various comprehensive properties of the epoxy adhesive. At the same time, after the polyamide curing agent participates in the curing, it can give the cured product higher bonding strength and weather resistance, and lower toxicity, while the alicyclic amine curing agent can improve the heat resistance and toughness of the cured product after participating in the curing.

[0009] The epoxy adhesive of the present invention uses liquid rubber to adjust the viscosity of epoxy resin. Viscosity is a very important index parameter for adhesives, which has a great influence on processability, degassing, etc. If the viscosity is too high, the fluidity of the adhesive is poor, affecting the bonding performance of the material. Therefore, conventional epoxy resin adhesives usually need to add a large amount of diluents and solvents to dilute the epoxy resin, thereby reducing the viscosity of the resin, but too much diluent added will affect the heat-resistant temperature and mechanical properties of the cured product. The present invention uses liquid rubber to mix with bisphenol A type epoxy resin, which can effectively reduce the viscosity of the adhesive, and the introduction of liquid rubber can also improve the bonding strength and toughness of the adhesive.

[0010] As a preferred solution, the bisphenol A epoxy resin is a bisphenol A epoxy resin with an epoxy equivalent of 180 to 240. The bisphenol A epoxy resin with an epoxy equivalent of 180 to 240 has a relatively low viscosity and good compatibility with liquid rubber, and can be further adjusted to an appropriate viscosity range, and the use of diluents and solvents can be avoided.

[0011] As a more preferred solution, the bisphenol A epoxy resin is composed of bisphenol A epoxy resin with an epoxy equivalent of 185 to 190 and bisphenol A epoxy resin with an epoxy equivalent of 210 to 240, with a mass percentage of 60 to 90%: 10 to 40%. The bisphenol A epoxy resin with an epoxy equivalent of 185 to 190 has a relatively low viscosity, is easy to level, has good wettability to the substrate, and can increase the thermal deformation temperature of the colloid; the bisphenol A epoxy resin with an epoxy equivalent of 210 to 240 has a larger molecular weight, a lower shrinkage rate of the colloid during the reaction, less internal stress accumulated inside the colloid, and a higher tensile shear strength. The use of two epoxy resins with different equivalents can effectively adjust the viscosity of the adhesive, improve the bonding strength and heat resistance temperature of the system, etc. If the proportion of bisphenol A epoxy resin with an epoxy equivalent of 185-190 is too high, the viscosity of the entire system will be too low, and the amount of glue during bonding will be too low and the bonding effect will be poor. If the proportion of bisphenol A epoxy resin with an epoxy equivalent of 185-190 is too low, the viscosity of the entire system will be too high, and it will be difficult to apply evenly during bonding.

[0012] As a preferred solution, the liquid rubber is hydroxyl-terminated polybutadiene and / or hydroxyl-terminated polyester-based polybutadiene. The preferred liquid rubber can not only adjust the viscosity of the epoxy resin well with bisphenol A type, but also can give the cured product higher bonding strength and weather resistance after being introduced into the cured product. A further preferred liquid rubber is hydroxyl-terminated polybutadiene. Hydroxyl-terminated polybutadiene has the advantages of low viscosity, high transparency, good oil resistance, volatility resistance, aging resistance, low temperature performance and good processing fluidity. Its cross-linked product is wear-resistant, low temperature-resistant, oil-resistant, water-resistant and acid-base-resistant, and has the advantages of excellent mechanical properties and good electrical insulation, which can meet the use requirements of epoxy adhesives.

[0013] As a preferred solution, the alicyclic amine curing agent is an alicyclic amine curing agent containing two or more active hydrogens. As a more preferred solution, the alicyclic amine curing agent is at least one of diaminomethylcyclohexane, menthanediamine and 4,4'-diaminodicyclohexylmethane. A further preferred alicyclic amine curing agent is menthanediamine (MDA).

[0014] As a preferred solution, the amine curing agent is composed of a polyamide curing agent and an alicyclic amine curing agent in a mass percentage of 40-60%:40-60%. If the proportion of the alicyclic amine curing agent is too high, although the heat resistance of the system can be increased, the viscosity is too low and the curing speed is too fast, which is not conducive to the bonding of the system. Therefore, the two are used in a proper proportion to give it good heat resistance while maintaining good bonding performance.

[0015] As a preferred solution, the mass ratio of the bisphenol A epoxy resin to the liquid rubber is 80-100:5-20. If the amount of liquid rubber added is too much, it is not easy to disperse evenly in the system, resulting in unstable products, while if the amount of liquid rubber added is too low, the bonding strength of the product is affected. When the amount of liquid rubber added to the epoxy resin system reaches the preferred ratio, the toughness and bonding strength of the system can be effectively improved, which is more conducive to the use of the epoxy resin adhesive of the present invention for bonding PMI foam and glass fiber composite materials, and helps to improve the quality of the product.

[0016] As a preferred solution, the mass ratio of the bisphenol A epoxy resin to the amine curing agent is 80-100:40-60.

[0017] As a preferred solution, the mass ratio of the filler to the bisphenol A epoxy resin is 2-5:80-100. The present invention can improve the bonding strength on the basis of greatly reducing the filler, thereby effectively avoiding the influence of excessively high proportion of filler on the mechanical properties of the cured body. As a more preferred solution, the filler is white carbon black. The total mass ratio of the filler to the bisphenol A epoxy resin to the liquid rubber is further preferably 2-3:90-100.

[0018] As a preferred solution, the low-viscosity, low-temperature, fast-curing solvent-free epoxy adhesive further includes an additive, wherein the additive is at least one of a coupling agent (e.g., K560), a release agent (e.g., DT-3799), a dispersant (e.g., BYK-W996), a defoamer (e.g., BYK-A350), and an accelerator (e.g., K54). Further preferably, the additive is a defoamer (e.g., BYK-A350). Since solvent additives cannot be added to the epoxy adhesive, only a siloxane defoamer (e.g., BYK-A350) is selected to achieve the purpose of defoaming the system.

[0019] The present invention also provides a method for preparing a low-viscosity, low-temperature, fast-curing solvent-free epoxy adhesive, which comprises fully mixing components including bisphenol A epoxy resin and liquid rubber, and then adding components including an amine curing agent and mixing them evenly to obtain the adhesive.

[0020] The preparation method of the present invention does not require the use of solvent-assisted reactions throughout the entire process, has no waste gas or waste liquid emissions, and also avoids the influence of solvents on product purity.

[0021] As a preferred solution, the bisphenol A epoxy resin and the liquid rubber are mixed by stirring at a speed of 300 to 5000 r / min for 150 to 300 min. More preferably, the stirring rate is 1000 to 4000 r / min for 180 to 300 min. If the stirring speed is too low, the two components are not mixed evenly, which will have an adverse effect on the subsequent product and reduce the preparation efficiency. If the stirring speed is too fast, the device is unstable.

[0022] The present invention also provides an application of a low-viscosity, low-temperature, fast-curing solvent-free epoxy adhesive, which is used for bonding a PMI foam board and a composite material skin.

[0023] As a preferred solution, the epoxy adhesive is evenly coated on the bonding surface of the PMI foam board and / or the composite material skin, and then bonded and cured under pressure to obtain the product.

[0024] As a preferred solution, the curing includes room temperature curing or heating curing. The conditions for heating curing are: pressure 5-15MPa, temperature 60-80°C, and time 0.5-1.5h; the conditions for room temperature curing are: pressure 5-15MPa, room temperature, and time 36-60h.

[0025] The cured product of the low-viscosity, low-temperature, fast-curing solvent-free epoxy adhesive of the present invention has excellent mechanical properties, such as a flexural strength of 320-360 MPa, a flexural modulus of 5100-7000 MPa, a tensile strength of 240-260 MPa, and a tensile modulus of 180-200 MPa.

[0026] The preferred formula of the low-viscosity, low-temperature, fast-curing solvent-free epoxy adhesive provided by the present invention comprises the following parts by weight:

[0027] 80-100 parts of bisphenol A epoxy resin (including 60-90% of bisphenol A epoxy resin with an epoxy equivalent of 185-190 and 10-40% of bisphenol A epoxy resin with an epoxy equivalent of 210-240);

[0028] Liquid rubber: 5-20 parts;

[0029] Additives: 0.5-2 parts;

[0030] Amine curing agent: 40-60 parts (including 40-60% polyamide curing agent and 40-60% alicyclic amine curing agent);

[0031] White carbon black: 2-5 parts.

[0032] A further preferred formula of the low-viscosity, low-temperature, fast-curing solvent-free epoxy adhesive comprises the following components in parts by weight:

[0033] 90-100 parts of bisphenol A epoxy resin (including 75-85% of bisphenol A epoxy resin with an epoxy equivalent of 185-190 and 15-25% of bisphenol A epoxy resin with an epoxy equivalent of 210-240);

[0034] Liquid rubber: 5-15 parts;

[0035] Additives: 0.5-1.5 parts;

[0036] Amine curing agent: 45-55 parts (including 45-55% polyamide curing agent and 45-55% alicyclic amine curing agent;

[0037] White carbon black: 2-4 parts.

[0038] Compared with the prior art, the beneficial technical effects of the present invention are as follows:

[0039] 1) The low-viscosity, low-temperature, fast-curing solvent-free epoxy adhesive provided by the present invention not only realizes low-temperature curing and rapid prototyping of materials based on the synergistic effect of various components, but also greatly improves the bonding strength. It is used for bonding PMI foam boards and composite skins. The peel strength after curing can reach up to 1.05N / cm, and it has good high and low temperature stability, reducing the risk of blistering.

[0040] 2) The preparation method of the low-viscosity, low-temperature, fast-curing solvent-free epoxy adhesive provided by the present invention has simple process, mild conditions, and is green and environmentally friendly. No solvent needs to be added during the entire preparation process, and the obtained product has high purity.

[0041] 3) The low-viscosity, low-temperature, fast-curing solvent-free epoxy adhesive provided by the present invention uses a combination of bisphenol A epoxy resin and liquid rubber. Based on the synergistic effect between the two, the toughness and bonding performance of the material are greatly improved. After testing, the tensile strength of the adhesive can reach 69MPa, the bending strength can reach 108MPa, the elongation at break is 5.6%, and the tensile-shear strength is 16MPa (aluminum-aluminum).

[0042] 4) The low-viscosity, low-temperature, fast-curing solvent-free epoxy adhesive provided by the present invention adopts a polyamide curing agent and an alicyclic amine curing agent in combination. The two amine curing agents have a synergistic effect, which can ensure that the epoxy resin is quickly cured at low temperatures, give it a higher bonding strength in a short time, and improve the comprehensive performance of the epoxy adhesive. At the same time, after the polyamide curing agent participates in the curing, it can give the cured product a higher bonding strength and weather resistance, and lower toxicity, while the alicyclic amine curing agent can improve the heat resistance and toughness of the cured product after participating in the curing. DETAILED DESCRIPTION

[0043] The present invention is further described below by means of specific examples. These embodiments are only intended to illustrate the present invention but are not intended to limit the scope of the present invention.

[0044] The raw materials involved in the following specific examples are all commercially available conventional raw materials.

[0045] Example 1

[0046] Take 80g of bisphenol A epoxy resin with an epoxy equivalent of 180, 10g of bisphenol A epoxy resin with an epoxy equivalent of 220, 10g of terminal hydroxyl polybutadiene rubber (McLean reagent: hydroxyl value 0.71-0.80mmol / g) and 1g of defoaming agent (BYK-A350), mix them and mechanically stir them for 180 minutes at a stirring speed of 3000 rpm, and set them aside after stirring.

[0047] Take 25 g of polyamide curing agent (650), 24 g of menthane diamine curing agent and 2 g of white carbon black (A300), mix them, and stir them mechanically for 60 minutes at a stirring speed of 2600 rpm. After stirring, set them aside.

[0048] The two mixed liquids are placed in packaging containers for later use, and are subsequently used to bond the PMI foam core material to the glass fiber composite material skin.

[0049] Example 2

[0050] Take 78g of bisphenol A epoxy resin with an epoxy equivalent of 180, 12g of bisphenol A epoxy resin with an epoxy equivalent of 220, 12g of terminal hydroxyl polybutadiene rubber (McLean reagent: hydroxyl value 0.71-0.80mmol / g) and 1g of defoaming agent (BYK-A350), mix them and mechanically stir them for 180 minutes at a stirring speed of 3000 rpm. After stirring, set them aside.

[0051] Take 25 g of polyamide curing agent (650), 24 g of menthane diamine curing agent and 2 g of white carbon black (A300), mix them, and stir them mechanically for 60 minutes at a stirring speed of 2600 rpm. After stirring, set them aside.

[0052] The two mixed liquids are placed in packaging containers for later use, and are subsequently used to bond the PMI foam core material to the glass fiber composite material skin.

[0053] Example 3

[0054] Take 78g of bisphenol A epoxy resin with an epoxy equivalent of 180, 12g of bisphenol A epoxy resin with an epoxy equivalent of 220, 12g of terminal hydroxyl polybutadiene rubber (McLean reagent: hydroxyl value 0.71-0.80mmol / g) and 1g of defoaming agent (BYK-A350), mix them and mechanically stir them for 180 minutes at a stirring speed of 3000 rpm. After stirring, set them aside.

[0055] 15 g of polyamide curing agent (650), 35 g of 4,4'-diaminodicyclohexylmethane (PACM) and 2 g of white carbon black (A300) were mixed and mechanically stirred for 60 minutes at a stirring speed of 2600 rpm. The mixture was set aside after stirring.

[0056] The two mixed liquids are placed in packaging containers for later use, and are subsequently used to bond the PMI foam core material to the glass fiber composite material skin.

[0057] Comparative Example 1

[0058] Take 90g of bisphenol A epoxy resin with an epoxy equivalent of 180, 10g of terminal hydroxyl polybutadiene rubber (McLean reagent: hydroxyl value 0.71-0.80mmol / g) and 1g of defoaming agent (BYK-A350), mix them and mechanically stir them for 180 minutes at a stirring speed of 3000 rpm, and set them aside after stirring.

[0059] Take 25 g of polyamide curing agent (650), 24 g of menthane diamine curing agent and 2 g of white carbon black (A300), mix them, and stir them mechanically for 60 minutes at a stirring speed of 2600 rpm. After stirring, set them aside.

[0060] The two mixed liquids are placed in packaging containers for later use, and are subsequently used to bond the PMI foam core material to the glass fiber composite material skin.

[0061] Comparative Example 2

[0062] Take 80g of bisphenol A epoxy resin with an epoxy equivalent of 180, 10g of bisphenol A epoxy resin with an epoxy equivalent of 220, 10g of terminal hydroxyl polybutadiene rubber (McLean reagent: hydroxyl value 0.71-0.80mmol / g) and 1g of defoaming agent (BYK-A350), mix them and mechanically stir them for 180 minutes at a stirring speed of 3000 rpm, and set them aside after stirring.

[0063] Take 50g of polyamide curing agent (650) and 2g of white carbon black (A300), mix them, and stir them mechanically for 60 minutes at a stirring speed of 2600 rpm. After stirring, set them aside.

[0064] The two mixed liquids are placed in packaging containers for later use, and are subsequently used to bond the PMI foam core material to the glass fiber composite material skin.

[0065] The epoxy resin system glue prepared in Example 1, Example 2, Example 3, Comparative Example 1 and Comparative Example 2 was poured into a mold for curing. The curing process was: 70°C, 1h. The mechanical properties of the cured specimens were then tested. The test method was based on GB / T3354-1999 and GB / T7124-2008.

[0066] Table 1 Performance indicators of splines

[0067]

[0068] It can be seen from Table 1 that the tensile-shear strength of the low-viscosity, low-temperature, fast-curing solvent-free epoxy adhesives prepared in Examples 1, 2 and 3 of the present invention is significantly enhanced than that of the resins in Comparative Example 1 and Comparative Example 2, and the Tg of the epoxy resin system prepared in Example 1 of the present invention is higher than that in Comparative Example 1 and Comparative Example 2. It can be seen that changing the resin / curing agent ratio causes various properties to decrease to varying degrees.

[0069] The epoxy resin system adhesives prepared in Example 1, Example 2, Example 3, Comparative Example 1, and Comparative Example 2 were used to bond the PMI foam core material to the glass fiber composite material skin. The curing process was: curing at 70°C for 1 hour, and then the cured panels were subjected to a peel strength test. The test method was based on GJB 103.8A-2021.

[0070] Table 2 Bonding performance test

[0071] Detection indicators Peel strength Mixing viscosity Plate surface condition Example 1 1.05N / cm 12314cp No bulge, no bubble Example 2 0.98N / cm 15263cp No bulge, no bubble Example 3 0.92N / cm 14236cp No bulge, no bubble Comparative Example 1 0.76N / cm 8254cp A small amount of bulge Comparative Example 2 0.43N / cm 16460cp There is a large area of ​​bulge

[0072] It can be seen from the test results in Table 2 that the peel strength of the sheets bonded by the epoxy adhesives prepared in Example 1, Example 2 and Example 3 is greatly improved compared with that of Comparative Example 1 and Comparative Example 2, and the viscosity of Comparative Example 1 is low and the adhesive content is small, which makes the sheet easy to bulge after curing, while the viscosity of Comparative Example 2 is too high, and only one curing agent is used, the adhesion is poor, and the peel strength is obviously low, resulting in large-area bulging of the sheet. It shows that the peel strength and processability of the epoxy adhesive of the present invention can meet the construction requirements on site.

[0073] The present invention has been described in detail above in conjunction with specific implementations and exemplary examples, but these descriptions cannot be understood as limiting the present invention. Those skilled in the art understand that, without departing from the spirit and scope of the present invention, a variety of equivalent substitutions, modifications or improvements may be made to the technical solution of the present invention and its implementation methods, all of which fall within the scope of the present invention. The scope of protection of the present invention shall be subject to the attached claims.

Claims

1. An epoxy adhesive, characterized in that: Contains bisphenol A type epoxy resin, liquid rubber, amine curing agent and filler; The amine curing agent consists of a polyamide curing agent and an alicyclic amine curing agent.

2. An epoxy adhesive according to claim 1, characterized in that: The bisphenol A epoxy resin is a bisphenol A epoxy resin with an epoxy equivalent of 180 to 240.

3. An epoxy adhesive according to claim 2, characterized in that: The bisphenol A epoxy resin is composed of a bisphenol A epoxy resin with an epoxy equivalent of 185 to 190 and a bisphenol A epoxy resin with an epoxy equivalent of 210 to 240 in a weight percentage of 60 to 90%:10 to 40%.

4. The epoxy adhesive according to claim 1, characterized in that: The liquid rubber is hydroxyl-terminated polybutadiene and / or hydroxyl-terminated polyester-based polybutadiene.

5. The epoxy adhesive according to claim 1, characterized in that: The alicyclic amine curing agent is an alicyclic amine curing agent containing two or more active hydrogens.

6. An epoxy adhesive according to claim 5, characterized in that: The alicyclic amine curing agent is at least one of diaminomethylcyclohexane, menthanediamine and 4,4'-diaminodicyclohexylmethane.

7. An epoxy adhesive according to claim 1, 5 or 6, characterized in that: The amine curing agent is composed of a polyamide curing agent and an alicyclic amine curing agent in a mass percentage of 40-60%:40-60%.

8. An epoxy adhesive according to any one of claims 1 to 4, characterized in that: The mass ratio of the bisphenol A epoxy resin to the liquid rubber is 80-100:5-20.

9. An epoxy adhesive according to claim 1, 5 or 6, characterized in that: The mass ratio of the bisphenol A epoxy resin to the amine curing agent is 80-100:40-60.

10. An epoxy adhesive according to any one of claims 1 to 6, characterized in that: The mass ratio of the filler to the bisphenol A epoxy resin is 2-5:80-100.

11. An epoxy adhesive according to claim 10, characterized in that: The filler is white carbon black.

12. The method for preparing an epoxy adhesive according to claim 11, characterized in that: The components including bisphenol A epoxy resin and liquid rubber are fully mixed, and then the components including amine curing agent are added and mixed evenly to obtain the product.

13. The use of an epoxy adhesive according to any one of claims 1 to 11, characterized in that: Used for bonding PMI foam panels and composite skins.

14. The use of an epoxy adhesive according to claim 13, characterized in that: The epoxy adhesive is evenly coated on the bonding surface of the PMI foam board and / or the composite material skin, and then bonded and cured under pressure to obtain the product.

15. The use of an epoxy adhesive according to claim 14, characterized in that: The curing conditions are: pressure 5-15 MPa, temperature 60-80° C., time 0.5-1.5 h, or pressure 5-15 MPa, room temperature, time 36-60 h.

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