Yellowing-resistant epoxy resin adhesive and preparation method thereof

Abstract

The invention relates to the technical field of adhesives, and particularly discloses a yellowing-resistant epoxy resin adhesive and a preparation method thereof. The epoxy resin adhesive is prepared from the following components in parts by weight: 80-100 parts of alicyclic epoxy resin, 3-5 parts of poly-alpha-olefin, 8-15 parts of a diluent, 3-5 parts of an accelerant, 30-45 parts of a curing agent, 0.1-0.5 part of an antioxidant, 0.1-0.5 part of an ultraviolet light absorber and 3-7 parts of aluminum powder dispersion liquid, the viscosity of the poly alpha olefin at 40 DEG C is 1-4mm < 2 > / s, the kinematic viscosity at 100 DEG C is 5.5-15mm < 2 > / s, and the pour point is less than or equal to-55 DEG C. According to the epoxy resin adhesive provided by the invention, the alicyclic epoxy resin is taken as a matrix, and the moisture curing performance and the low-temperature resistance after curing are improved by adding the poly alpha olefin and the aluminum powder dispersion liquid; the obtained epoxy resin adhesive has excellent yellowing resistance and adhesive performance.

Description

Technical Field

[0001] The present application relates to the technical field of adhesives, and more specifically, to a yellowing-resistant epoxy resin adhesive and a preparation method thereof. Background Art

[0002] Epoxy resins are widely used in aerospace materials, electronic components, adhesive materials, coatings, composite materials, etc. due to their good thermal stability, chemical stability, dimensional stability, mechanical properties, insulation, adhesion, and molding processability. However, epoxy resins are sensitive to light and are prone to photochemical reactions, which can lead to degradation of epoxy resins, yellowing of resin materials, and reduced mechanical properties. In particular, in the field of special-purpose adhesives, there are strict restrictions on product color, making improving the anti-yellowing properties of epoxy resins a major research topic.

[0003] There are many factors that cause epoxy products to turn yellow, such as: ① The structure of aromatic epoxy resin bisphenol A is easily oxidized to produce carbonyl groups to form yellowing groups; ② The free amine components in the amine curing agent directly polymerize with the epoxy resin, resulting in local temperature rise and accelerated yellowing; ③ Tertiary amine accelerators and nonylphenol accelerators are prone to discoloration under thermal oxygen and UV irradiation; ④ The temperature is too high during the reaction process, and residual impurities and metal catalysts in the system will induce yellowing, etc.

[0004] At present, the existing technology usually selects alicyclic epoxy resin to replace bisphenol A or bisphenol F epoxy resin, selects alicyclic diamines, aliphatic diamines or polyamines to replace aromatic diamines, and adds ultraviolet absorbers, antioxidants, etc. to improve the yellowing resistance of epoxy resin glue.

[0005] Due to the poor reactivity of alicyclic epoxy resins and alicyclic amine curing agents, a large number of curing accelerators with aromatic rings are often used to assist in achieving room temperature curing, which makes the yellowing resistance of epoxy resin adhesives worse. In addition, adhesives made with alicyclic epoxy resins and alicyclic amine curing agents are difficult to cure under low temperature and humid conditions or the mechanical properties of the cured products are poor, which greatly limits the scope of application. Summary of the invention

[0006] In order to solve the above technical problems, the present application provides a yellowing-resistant epoxy resin glue and a preparation method thereof. The epoxy resin glue is based on alicyclic epoxy resin, and polyalphaolefin and aluminum powder dispersion are added to improve its moisture curing performance and low-temperature resistance after curing, so that the epoxy resin glue has excellent yellowing resistance and adhesive properties.

[0007] In a first aspect, the present application provides a yellowing-resistant epoxy resin adhesive and a preparation method thereof, which adopts the following technical scheme:

[0008] A yellowing-resistant epoxy resin adhesive is prepared from the following components in parts by weight: 80-100 parts of alicyclic epoxy resin, 3-5 parts of polyalphaolefin, 8-15 parts of diluent, 3-5 parts of accelerator, 30-45 parts of curing agent, 0.1-0.5 parts of antioxidant, 0.1-0.5 parts of ultraviolet light absorber, and 3-7 parts of aluminum powder dispersion;

[0009] The polyalphaolefin has a kinematic viscosity of 1-4 mm at 100°C. 2 / s, 40℃ kinematic viscosity is 5.5-15mm 2 / s, pour point ≤-55℃.

[0010] Alicyclic epoxy resin is used as the curing body because it does not contain easily oxidized groups such as benzene rings, which fundamentally improves the defect of easy yellowing. Then, by adding a certain amount of polyalphaolefin, the moisture curing performance of the epoxy system and the low temperature resistance of the cured product are improved. In addition, polyalphaolefin can replace the leveling agent and improve the leveling performance of the adhesive as a non-reactive leveling agent. The addition of aluminum powder dispersion can shield the light oxidation of the resin system by ultraviolet light by utilizing the physical reflection of aluminum powder, thereby improving the yellowing resistance. In addition, aluminum powder can also improve the strength of the cured product. Aluminum powder dispersion is suitable for epoxy systems with aromatic amines as curing agents.

[0011] Preferably, the aluminum powder dispersion is composed of a mixture of aluminum powder and a dispersant, and the dispersant is alkenyl succinic anhydride.

[0012] Preferably, the mass percentage of the aluminum powder and the dispersant is (80-90%):(10-20%), and more preferably, the mass percentage of the aluminum powder and the dispersant is 85%:15%.

[0013] Preferably, the aluminum powder is spherical aluminum powder and / or flake aluminum powder. More preferably, the aluminum powder is flake aluminum powder.

[0014] Aluminum powder has excellent reflectivity to ultraviolet light of 200-600nm. It can increase its strength when added to resin, and can reflect ultraviolet light, reduce the direct contact between epoxy resin and ultraviolet light, and greatly improve the yellowing resistance of the resin system. However, aluminum powder has poor dispersibility in the resin system and is prone to agglomeration. The prior art uses isopropanol to disperse it, and then removes the isopropanol by evaporation after adding it to the epoxy system. This method has the following objective disadvantages: ① The method of evaporating to remove isopropanol is time-consuming and energy-consuming, and is not suitable for large-scale industrial production; ② If the isopropanol is not completely evaporated, it will cause the epoxy system to increase the curing time, which has a negative impact on the bonding effect. This application uses alkenyl succinic anhydride instead of isopropanol as a dispersant for aluminum powder, which has a better dispersion effect, and does not need to be removed by evaporation after being added to the epoxy system. Its anhydride group can react with the epoxy group and can directly participate in the curing of the epoxy resin, realizing industrial-scale production.

[0015] Preferably, the curing agent is selected from one or more combinations of aliphatic amine curing agents, alicyclic amine curing agents, aromatic amine curing agents, polyamide curing agents, anhydride curing agents, and polyether amine curing agents. More preferably, the curing agent is alicyclic amine curing agents or aliphatic amine curing agents.

[0016] Preferably, the accelerator is selected from one or more combinations of phenol accelerators, imidazole accelerators, amine accelerators, and Lewis acid accelerators.

[0017] Among them, phenolic accelerators include but are not limited to phenol, resorcinol, nonylphenol, bisphenol A and 2,4,6-tris(dimethylaminomethyl)phenol, etc., amine accelerators include but are not limited to o-hydroxybenzyldimethylamine, triethylamine, triethanolamine, benzyldimethylamine and alkyltrimethylammonium bromide salts, etc., imidazole accelerators include but are not limited to 2-methylimidazole and 2-phenylimidazole, etc., Lewis acid accelerators include but are not limited to BF3, SnCl4, AlCl3, FeCl3, TiCl4 and ZnCl2, etc.

[0018] Preferably, the diluent is at least one of benzyl glycidyl ether, 1,4-butanediol diglycidyl ether, cyclohexanediol diglycidyl ether, resorcinol diglycidyl ether, o-cresyl glycidyl ether, cyclopentanediol diglycidyl ether, trimethylol triglycidyl ether, polypropylene glycol diglycidyl ether and ethylene glycol diglyceryl ether.

[0019] Preferably, the antioxidant includes at least one of a hindered amine antioxidant, a hindered phenol antioxidant, a sulfur-containing antioxidant, and a phosphorus-containing antioxidant.

[0020] Among them, hindered amine antioxidants include but are not limited to bis(1-octyloxy-2,2,6,6-tetramethyl-4-piperidinyl) sebacate, bis(1,2,2,6,6-pentamethyl-4-piperidinyl) sebacate, etc.; hindered phenol antioxidants include but are not limited to 4-[(4,6-dioctylthio-1,3,5-triazine-2-yl)amino]-2,6-di-tert-butylphenol, etc.; sulfur-containing antioxidants include but are not limited to thiodithiophene. Dilauryl propionate (DLTDP), di(tridecanol) thiodipropionate, di(tetradecyl) 3,3'-thiodipropionate (DMTDP), dioctadecyl thiodipropionate (DSTDP), etc.; phosphorus-containing antioxidants include but are not limited to triphenyl phosphite TPP, tris[2,4-di-tert-butylphenyl] phosphite (antioxidant 168), V76-P, V78-P, V85-P, V95-P, etc.

[0021] Preferably, the ultraviolet light absorber includes at least one of UV-531, UV-9, UV-P, UV-329, UV-326, UV-327, UV-320, UV-328, UV-234, UV-1130, UV-0, and UV-284.

[0022] Antioxidants and UV absorbers can reduce the yellowing of epoxy systems caused by ultraviolet rays. In addition, the two can also work together to reduce the possibility of yellowing caused by the generation of oxidative free radicals in the system to a certain extent, greatly improving the anti-yellowing effect of the adhesive.

[0023] In a second aspect, the present application provides a method for preparing a yellowing-resistant epoxy resin adhesive, which adopts the following technical solution:

[0024] A method for preparing yellowing-resistant epoxy resin adhesive comprises the following steps:

[0025] (1) using alkenyl succinic anhydride as a solvent, ball milling aluminum powder with a ball mill to remove aluminum oxide on the surface of the aluminum powder, and ultrasonically dispersing the obtained aluminum powder-alkenyl succinic anhydride mixture to obtain an aluminum powder dispersion, wherein the mass percentage of aluminum powder to alkenyl succinic anhydride is (80-90%):(10-20%);

[0026] (2) Taking alicyclic epoxy resin as a matrix, adding poly-alpha-olefin, diluent, accelerator, antioxidant, ultraviolet light absorber and curing agent, as well as the aluminum powder dispersion prepared in step (1), and mechanically stirring them to obtain the yellowing-resistant epoxy resin adhesive.

[0027] In summary, this application has the following beneficial effects:

[0028] (1) The present application uses alicyclic epoxy resin as the main component to reduce the yellowing possibility of epoxy resin glue, and adopts the method of adding a small amount of poly-alpha-olefin to improve the defects of poor moisture curing performance and low temperature resistance of alicyclic epoxy resin glue system;

[0029] (2) The poly-alpha-olefin added in the present application can replace the leveling agent and improve the workability of the epoxy system without adding the leveling agent;

[0030] (3) The present application can improve the defect of yellowing of epoxy adhesive system when aromatic amine is used as curing agent by adding aluminum powder dispersion;

[0031] (4) In the present application, aluminum powder is dispersed with alkenyl succinic anhydride. After adding it to the epoxy system, there is no need to evaporate and remove the solvent. Alkenyl succinic anhydride can directly participate in the epoxy curing reaction, and industrial production can be realized. DETAILED DESCRIPTION

[0032] The following describes the implementation of the present application through specific examples, and those skilled in the art can easily understand other advantages and effects of the present application from the contents disclosed in this specification. The present application can also be implemented or applied through other different specific implementations, and the details in this specification can also be modified or changed in various ways based on different viewpoints and applications without departing from the spirit of the present application.

[0033] In addition, it should be understood that one or more method steps mentioned in the present application do not exclude the existence of other method steps before or after the combination step or the insertion of other method steps between the steps explicitly mentioned, unless otherwise specified. Moreover, unless otherwise specified, the numbering of each method step is only a convenient tool for identifying each method step, and is not intended to limit the order of arrangement of each method step or the scope of implementation of the present application. Changes or adjustments in their relative relationships shall also be regarded as the scope of implementation of the present application without substantially changing the technical content.

[0034] If the specific experimental conditions are not specified in the examples, they are usually based on the conventional conditions in the field or the conditions recommended by the reagent company; the materials, reagents, etc. used in the examples can be purchased through commercial channels unless otherwise specified.

[0035] The properties of the polyalphaolefins used in the examples and comparative examples of the present application are shown in the following table, and they can all be purchased through commercial channels, such as Shanghai Doppler Chemical Co., Ltd., Apexone Technology (Hangzhou) Co., Ltd., ExxonMobil Corporation, etc.

[0036] Table 1

[0037]

[0038] The epoxy resin used in the present application specifically adopts CER-170 alicyclic glycerol ether epoxy resin, which is a saturated alicyclic structure containing two epoxy groups. The molecular structure contains polar structures such as ether bonds and structures such as hydroxyl groups, so it has good adhesion. It does not contain a benzene ring structure and is a saturated alicyclic structure. It is resistant to ultraviolet light and has excellent weather resistance, heat resistance and aging resistance.

[0039] The curing agent used in the present application is aliphatic amine curing agent and aromatic amine curing agent. The aliphatic amine curing agent specifically adopts 593 curing agent, and the aromatic amine curing agent specifically adopts 113 curing agent.

[0040] The diluent used in the present application is cyclohexanediol diglycidyl ether; the accelerator is an amine accelerator, specifically triethylamine; the antioxidant is a sulfur-containing antioxidant, specifically dioctadecyl thiodipropionate (DSTDP); and the ultraviolet light absorber is UV-531.

[0041] The aluminum powder used in the present application is flake aluminum with a diameter of 600 mesh and a diameter-to-thickness ratio of 100:1.

[0042] The solvent for dispersing aluminum powder in the present application is alkenyl succinic anhydride, specifically octadecenyl succinic anhydride (ODSA) and dodecenyl succinic anhydride (DDSA).

[0043] Preparation of aluminum powder dispersion:

[0044] Example 1 Preparation of aluminum powder dispersion: Using ODSA as solvent, the aluminum powder was ball-milled in a high-energy ball mill to remove the oxide film on its surface. The obtained aluminum powder-ODSA mixture was ultrasonically dispersed at a frequency of 40KHz for 0.5h to obtain a filtrate dispersion with a mass percentage of: aluminum powder 85%, ODSA 15%.

[0045] Example 2 Preparation of aluminum powder dispersion: The preparation method is the same as that of Example 1. The final aluminum powder dispersion has a mass percentage composition of: aluminum powder 80%, ODSA 20%.

[0046] Example 3 Preparation of aluminum powder dispersion: The preparation method is the same as that of Example 1. The final aluminum powder dispersion has a mass percentage composition of: aluminum powder 90%, ODSA 10%.

[0047] Example 4 Preparation of aluminum powder dispersion: Aluminum powder was ball-milled with DDSA as solvent. The preparation method was the same as that of Example 1. The final aluminum powder dispersion had a mass percentage composition of: aluminum powder 85%, ODSA 15%.

[0048] Preparation of epoxy resin glue:

[0049] Example 5 Preparation of yellowing-resistant epoxy resin glue: The amount of each raw material is shown in Table 2. CER-170 epoxy resin, mPAO2, cyclohexanediol diglycidyl ether diluent, triethylamine accelerator, DSTDP antioxidant, UV-531 ultraviolet light absorber and 593 curing agent, as well as the aluminum powder dispersion prepared in Example 1 are added to a stirring tank in sequence, and after stirring evenly, the yellowing-resistant epoxy resin glue is obtained.

[0050] Example 6 Preparation of yellowing-resistant epoxy resin adhesive: The aluminum powder dispersion prepared in Example 2 was used, and the rest was the same as Example 5.

[0051] Example 7 Preparation of yellowing-resistant epoxy resin adhesive: The aluminum powder dispersion prepared in Example 3 was used, and the rest was the same as in Example 5.

[0052] Example 8 Preparation of yellowing-resistant epoxy resin adhesive: The aluminum powder dispersion prepared in Example 4 was used, and the rest was the same as in Example 5.

[0053] Example 9 Preparation of yellowing-resistant epoxy resin adhesive: The amount of each raw material used is different from that in Example 5, see Table 2 for details.

[0054] Example 10 Preparation of yellowing-resistant epoxy resin adhesive: The amount of each raw material used is different from that in Example 5, see Table 2 for details.

[0055] Example 11 Preparation of yellowing-resistant epoxy resin adhesive: The polyalphaolefin used is mPAO3.5, and the rest is the same as Example 5.

[0056] Example 12 Preparation of yellowing-resistant epoxy resin adhesive: the curing agent used is 113 curing agent, and the rest is the same as Example 5.

[0057] Table 2 Amount of each raw material component in Examples 5-11 (0.01kg)

[0058]

[0059]

[0060] Comparative Example 1 Preparation of epoxy resin adhesive: no poly-alpha-olefin was added, and the rest was the same as Example 5.

[0061] Comparative Example 2: Preparation of epoxy resin adhesive: The polyalphaolefin used is mPAO40, and the rest is the same as Example 5.

[0062] Comparative Example 3: Preparation of epoxy resin adhesive: No aluminum powder dispersion was added, and the rest was the same as Example 5.

[0063] Performance testing

[0064] Moisture curing performance and low temperature resistance test: The epoxy resin glue prepared in each embodiment and comparative example was evenly coated on the surface of the polished aluminum specimen, and two aluminum specimens were bonded together. After curing for 24 hours at a temperature of 25°C and a humidity of 80%, a test sample was made and the shear strength at 25°C and after freezing at -20°C for 12 hours was tested.

[0065] Yellowing resistance test: The epoxy resin glue prepared in each embodiment and comparative example was coated on the surface of a 20×20 mm high-transmittance glass sheet, cured at room temperature for 24 hours, and aged under 1 kW ultraviolet light for 72 hours. The DE value was then tested. The smaller the color difference DE value, the better the yellowing resistance.

[0066] The specific test results are shown in Table 2.

[0067] Table 2 Test results

[0068]

[0069]

[0070] Comparing the test results of Examples 5, 6 and 7, it can be seen that when the mass ratio of aluminum powder to alkenyl succinic anhydride in the aluminum powder dispersion is 85:15, the use effect is best, and the obtained epoxy resin glue has the best mechanical properties and yellowing resistance.

[0071] Comparing the test results of Example 5 and Comparative Examples 1 and 2, it can be seen that the addition of poly-alpha-olefin can significantly improve the moisture curing performance and low temperature resistance of the adhesive prepared with alicyclic epoxy resin as the matrix.

[0072] Comparing the test results of Example 5 and Comparative Example 3, it can be seen that the aluminum powder dispersion prepared with alkenyl succinic anhydride as the dispersing solvent can significantly improve the yellowing resistance of the epoxy resin glue and enhance the strength of the epoxy resin glue to a certain extent.

[0073] In addition, during the construction process, the epoxy resin glue prepared in the present application has high coating efficiency and good fluidity. The surface after curing is flat and smooth, without defects such as bubbles and pinholes. This shows that the yellowing-resistant epoxy resin glue of the present application still has high leveling performance without the addition of a leveling agent, and is suitable for filling and covering small gaps and concave and convex objects, thereby further broadening the scope of application.

[0074] The above is only a preferred embodiment of the present invention, and is not any formal or substantial limitation of the present invention. It should be pointed out that ordinary technicians in this technical field can make several improvements and supplements without departing from the method of the present invention, and these improvements and supplements should also be regarded as the protection scope of the present invention. Any technician familiar with this profession, without departing from the spirit and scope of the present invention, can make some changes, modifications and evolutions of the technical content disclosed above, which are equivalent embodiments of the present invention; at the same time, any changes, modifications and evolutions of any equivalent changes made to the above embodiments based on the essential technology of the present invention are still within the scope of the technical solution of the present invention.

Claims

1. A yellowing-resistant epoxy resin adhesive, characterized in that: The invention is prepared from the following components in parts by weight: 80-100 parts of alicyclic epoxy resin, 3-5 parts of polyalphaolefin, 8-15 parts of diluent, 3-5 parts of accelerator, 30-45 parts of curing agent, 0.1-0.5 parts of antioxidant, 0.1-0.5 parts of ultraviolet light absorber and 3-7 parts of aluminum powder dispersion; The polyalphaolefin has a kinematic viscosity of 1-4 mm at 100°C. 2 / s, 40℃ kinematic viscosity is 5.5-15mm 2 / s, pour point ≤-55℃.

2. The yellowing-resistant epoxy resin adhesive according to claim 1, characterized in that: The aluminum powder dispersion is composed of a mixture of aluminum powder and a dispersant, and the dispersant is alkenyl succinic anhydride.

3. The yellowing-resistant epoxy resin adhesive according to claim 2, characterized in that: The mass percentage of the aluminum powder and the dispersant is (80-90%):(10-20%).

4. The yellowing-resistant epoxy resin adhesive according to claim 3, characterized in that: The mass percentage of the aluminum powder and the dispersant is 85%:15%.

5. The yellowing-resistant epoxy resin adhesive according to claim 1, characterized in that: The curing agent is selected from one or more combinations of aliphatic amine curing agents, alicyclic amine curing agents, aromatic amine curing agents, polyamide curing agents, acid anhydride curing agents, and polyether amine curing agents.

6. The yellowing-resistant epoxy resin adhesive according to claim 1, characterized in that: The accelerator is selected from one or more combinations of phenol accelerators, imidazole accelerators, amine accelerators, and Lewis acid accelerators.

7. The yellowing-resistant epoxy resin adhesive according to claim 1, characterized in that: The diluent is at least one of benzyl glycidyl ether, 1,4-butanediol diglycidyl ether, cyclohexanediol diglycidyl ether, resorcinol diglycidyl ether, o-cresyl glycidyl ether, cyclopentanediol diglycidyl ether, trimethylol triglycidyl ether, polypropylene glycol diglycidyl ether and ethylene glycol diglyceryl ether.

8. The yellowing-resistant epoxy resin adhesive according to claim 1, characterized in that: The antioxidant is at least one of a hindered amine antioxidant, a hindered phenol antioxidant, a sulfur-containing antioxidant, and a phosphorus-containing antioxidant.

9. The yellowing-resistant epoxy resin adhesive according to claim 1, characterized in that: The ultraviolet light absorber is at least one of UV-531, UV-9, UV-P, UV-329, UV-326, UV-327, UV-320, UV-328, UV-234, UV-1130, UV-0, and UV-284.

10. A method for preparing the yellowing-resistant epoxy resin adhesive according to any one of claims 1 to 9, characterized in that: The following steps are involved: (1) using alkenyl succinic anhydride as a solvent, ball milling aluminum powder with a ball mill to remove aluminum oxide on the surface of the aluminum powder, and ultrasonically dispersing the obtained aluminum powder-alkenyl succinic anhydride mixture to obtain an aluminum powder dispersion, wherein the mass percentage of aluminum powder to alkenyl succinic anhydride is (80-90%):(10-20%); (2) Taking alicyclic epoxy resin as a matrix, adding poly-alpha-olefin, diluent, accelerator, antioxidant, ultraviolet light absorber and curing agent, as well as the aluminum powder dispersion prepared in step (1), and mechanically stirring them to obtain the yellowing-resistant epoxy resin adhesive.

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