A dual-cure fluorine-containing epoxy adhesive

Abstract

The present application relates to a kind of dual-curing fluorine-containing epoxy adhesives, for the dual-curing fluorine-containing epoxy adhesives of ultraviolet light solid and heat solid, it has low refractive index, high transmittance, high glass transition temperature, low viscosity, excellent resistance to humid heat aging performance and so on.The adhesive includes the following components by weight parts: (a) epoxy resin 30-60 parts (b) fluorine-containing epoxy resin 30-50 parts (c) cationic photo-initiator 0.5-3 parts (d) cationic thermal initiator 0.5-3 parts (e) auxiliary 0.2-4 parts.The dual-curing adhesive of the present application has low refractive index, high transmittance, high glass transition temperature, low viscosity, excellent resistance to humid heat aging performance.

Description

Technical Field

[0001] This invention belongs to the field of adhesives, specifically relating to a dual-curing fluorinated epoxy adhesive, and more specifically, a method for preparing a dual-curing adhesive that is both UV-cured and thermosetting. Background Technology

[0002] In the field of optical communication, adhesives are typically required to have a low refractive index to minimize light loss during propagation. Simultaneously, the operating environment of the product demands that the adhesive possess good heat resistance and excellent resistance to damp heat aging. Most existing low-refractive-index adhesives are prepared using fluorinated acrylic resins or silicone as raw materials.

[0003] Due to the presence of ester bonds and carboxylic acid groups in the molecular chain of acrylic resins, the cured adhesives exhibit poor resistance to humid heat aging. Although fluorinated acrylics possess extremely strong hydrophobicity, which can effectively improve the resistance to humid heat aging of cured adhesives, it is still far from meeting the requirements for applications in optical communication. Furthermore, acrylic adhesives are generally cured by free radical photocuring, resulting in significant volume shrinkage before and after curing, which may cause displacement and lead to substantial light loss during optical coupling.

[0004] Silicone-based low-refractive-index adhesives have excellent resistance to humid heat aging, but they also have drawbacks such as poor adhesive strength, poor bonding effect, and low glass transition temperature. Summary of the Invention

[0005] The purpose of this invention is to address the problems of poor refractive index and resistance to humid heat aging in existing technologies by providing a dual-curing fluorinated epoxy adhesive, specifically a dual-curing adhesive with low refractive index, high light transmittance, high glass transition temperature, low viscosity, and excellent resistance to humid heat aging.

[0006] The objective of this invention can be achieved through the following methods:

[0007] This invention provides a dual-curing fluorinated epoxy adhesive, which comprises the following components in parts by weight:

[0008]

[0009] As one embodiment of the present invention, the epoxy resin includes one or more of the following: 3,4-epoxycyclohexylcarboxylate-3',4'-epoxycyclohexylmethyl ester (2021P), bis((3,4-epoxycyclohexyl)methyl)adipate (TTA26), 3,4-epoxycyclohexylmethyl methacrylate (TTA15), vinylcyclohexene dioxide (TTA22), dipentene dioxide (TTA20), 3-ethyl-3-hydroxymethyloxetane (TTA-202), 3,3-(oxybismethylene)bis((3-ethyl)oxetane) (TTA201), 3-ethyl-3-(-methacryloyloxymethyl)oxetane (TTA101), and epoxy-modified polybutadiene (605E). The epoxy resin is preferably one or more of 3,4-epoxycyclohexylcarboxylic acid-3',4'-epoxycyclohexylmethyl ester (2021P) and vinyl cyclohexene dioxide (TTA22).

[0010] As one embodiment of the present invention, the fluorine content of the fluorinated epoxy resin is 20%-65%.

[0011] As one embodiment of the present invention, the fluorinated epoxy resin is selected from 3-(perfluorobutane)-1,2-epoxypropane. 3-[(2-perfluorohexyl)ethoxy]-1,2-epoxypropane 1,2-Epoxy-3-(2,2,2-trifluoroethoxy)-propane Epoxyfluoropropane One of them. The FPO series resins used in this invention, the fluorine content, refractive index, and structural formula of the fluorinated resins are shown in the table below:

[0012] Refractive index, fluorine content and structural formula of various FPO resins

[0013]

[0014] The preferred option is FPO-3, which has a fluorine content of 36.5% and a refractive index of 1.363.

[0015] As one embodiment of the present invention, the cationic photoinitiator includes one or more of aryl diazonium salts, diaryl iodonium salts, and ferrocene salts. Diaryl iodonium salts include one or more of bis(4-dodecylbenzene)iodonium hexafluoroantimonate, 4,4'-xylyliodonium hexafluorophosphate (TR-PAG-30101), long-chain alkyl diphenyliodonium salts, di-tert-butylbenzeneiodonium hexafluorophosphate (TR-PAG-30201), and triphenylthionium salts such as diphenyl[4-(phenylthio)phenyl]-hexafluoroantimonate, bis(4,4'-thioether triphenylthionium)hexafluoroantimonate, and phenyl[4-(phenylthio)phenyl]-trifluorophosphate (CPI-200K); ferrocene salts include one or more of cumene ferrocene hexafluorophosphate (261). The preferred cationic photoinitiator is phenyl[4-(phenylthio)phenyl]-trifluorophosphate (CPI-200K).

[0016] As one embodiment of the present invention, the cationic thermal initiator includes one or more of TR-TAG-50102, TR-TAG-50108, TR-TAG-50302 (Changzhou Qiangli Electronic New Materials Co., Ltd.), and CXC1612 (King Industries). CXC1612 is preferred as the cationic thermal initiator.

[0017] The additives include adhesion promoters and antioxidants. The adhesion promoter is KH560; the antioxidant is L-20; the mass ratio of the two additives is 2:1.

[0018] This invention also provides a method for preparing a dual-curing fluorinated epoxy adhesive, the preparation method being as follows:

[0019] Mix 30-60 parts by weight of epoxy resin, 30-50 parts by weight of fluorinated epoxy resin, 0.5-3 parts by weight of cationic photoinitiator, 0.5-3 parts by weight of cationic photoinitiator, and 0.2-4 parts of additives; stir in the dark to homogenize the mixture, then degas it. After degassing, filter and inject into a syringe.

[0020] The components are placed in a mixer in the dark to homogenize the mixture, then degassed, filtered, and injected into a syringe. During the manufacturing process, especially during homogenization, the heat in the composition must be kept as low as possible. Preferably, the temperature of the composition during manufacturing is no more than 25°C.

[0021] Compared with the prior art, the present invention has the following beneficial effects:

[0022] (1) Specifically, this invention is a dual-curing adhesive with low refractive index, high light transmittance, and excellent resistance to humid heat aging.

[0023] (2) This invention utilizes the advantages of epoxy adhesives, such as good adhesion and a high glass transition temperature after curing, by selecting synthetic fluorinated epoxy resins to reduce the refractive index of the entire adhesive system and improve the adhesive's resistance to humid heat aging after curing. This invention is a dual-curing adhesive with low refractive index, high light transmittance, high glass transition temperature, low viscosity, and excellent resistance to humid heat aging. This adhesive has a refractive index below 1.430, light transmittance greater than 95%, a glass transition temperature above 100℃, an adhesion strength greater than 2.5 kgf, and an adhesion strength attenuation of less than 30% after 1000 hours of high temperature and high humidity. Detailed Implementation

[0024] The present invention will now be described in detail with reference to specific embodiments. The following examples are implemented under the premise of the technical solution of the present invention, providing detailed implementation methods and specific operating procedures, which will help those skilled in the art to further understand the present invention. It should be noted that the scope of protection of the present invention is not limited to the following embodiments; any adjustments and improvements made under the concept of the present invention are all within the scope of protection of the present invention.

[0025] The adhesive described in this invention is tested using the following method:

[0026] LED curing: The adhesive thickness is 0.15mm, and the curing energy is 3000mJ / cm² under a 365nm LED UV lamp. 2 .

[0027] Thermosetting: Apply adhesive to a thickness of 0.15mm and bake in an oven at 80℃ for 1 hour.

[0028] Viscosity: The viscosity of the adhesive at 25°C was tested using a Brookfield CP52 viscometer.

[0029] Refractive index before curing: The refractive index of the wet adhesive at 25°C was measured using an Abbe refractometer.

[0030] Bond strength: Test chip-glass shear strength, bonding area 1mm*1mm.

[0031] Glass transition temperature: The glass transition temperature of the cured adhesive is tested using DMA.

[0032] Volume shrinkage rate: The shrinkage rate of the adhesive before and after curing was tested using the density method.

[0033] Transmittance: The transmittance of the cured adhesive in the wavelength range of 380nm-800nm ​​was tested using a spectrophotometer (sample thickness 0.45mm).

[0034] Humid heat aging: The bonded samples were placed in an environment of 85°C and 85%RH for 1000 hours, and after being placed at room temperature for 4 hours, the bond strength of the adhesive was tested and compared with the samples that had not undergone humid heat aging.

[0035] Epoxy resins can generally be divided into aromatic epoxy resins and alicyclic epoxy resins. Aromatic epoxy resins, due to the presence of benzene rings, typically have a high refractive index, making them difficult to meet the requirements for applications in optical communication. Alicyclic epoxy resins have a relatively lower refractive index, but it is still generally above 1.460. Fluorine-modified epoxy resins can significantly reduce the refractive index of the resin itself, meeting the requirement of a refractive index below 1.430 in optical communication applications.

[0036] However, adhesives cured with a single fluorinated epoxy resin generally have low adhesion to the substrate. This necessitates the use of a mixture of fluorinated epoxy resin and conventional epoxy resin. Due to the low surface energy and polarity of fluorinated epoxy resin, compatibility issues arise with conventional epoxy resins. Since commercially available photocurable low-refractive-index epoxy resins are extremely rare, this invention selects a fluorinated epoxy resin, FPO.

[0037] The fluorine content and refractive index of fluorinated resin FPO are shown in the table below:

[0038] Refractive index, fluorine content and structural formula of various FPO resins

[0039]

[0040] The commercially available fluorinated epoxy resin 3-(perfluorooctyl)-1,2-epoxypropane (T8-EP) has a refractive index of 1.32 and a fluorine content of 67.8%.

[0041] Examples 1-10

[0042] The comparison of Examples 1-10 is shown in Table 1 below. As the refractive index of the fluorinated resin decreases, its compatibility with general epoxy resins deteriorates. Only the fluorinated epoxy resins FPO-3 and FPO-4 are compatible with the general epoxy resins we selected. This is mainly because the lower the refractive index, the higher the fluorine content of the resin, the lower the surface energy of the fluorinated resin, and the worse its compatibility with general epoxy resins.

[0043] Table 1. Compatibility of Fluorinated Epoxy Resins

[0044]

[0045] FPO-3 and FPO-4 were identified as potential resins for the application through compatibility testing.

[0046] Examples 11-16

[0047] The components of Examples 11-16 are shown in Table 2 below, comparing the effects of different amounts of FPO-3 and FPO-4 on the adhesive performance. Example 16 did not contain any fluorinated epoxy resin, and the refractive index and resistance to damp heat aging of the adhesive significantly failed to meet the application requirements in the optical communication field. As the amount of fluorinated epoxy resin FPO-4 increased from 36 parts to 56 parts, the refractive index of the prepared adhesive decreased from 1.463 to 1.435, but the adhesive strength decreased significantly, from 4.28 kgf to 1.19 kgf. This shows that as the amount of FPO-4 increases, when the refractive index of the adhesive is adjusted below 1.430, the adhesive strength will be far below the application requirements.

[0048] According to Example 15: when the amount of fluorinated epoxy resin FPO-3 added is 46 parts, the resulting adhesive has a refractive index of 1.425, a bonding strength of 3.92 kgf, a glass transition temperature of 115°C, a decay of 9.2% after 1000 hours of damp heat aging, and a light transmittance of 96%, which meets the application requirements in the field of optical communication.

[0049] Although Embodiment 15 is disclosed above with reference to a preferred embodiment, it is not intended to limit the present invention. Any person skilled in the art can make some modifications and improvements without departing from the technology and scope of the present invention. Therefore, the scope of protection of the present invention shall be defined by the claims.

[0050] Table 2. Performance tests of different formulation ratios The specific embodiments of the present invention have been described above. It should be understood that the present invention is not limited to the specific embodiments described above, and those skilled in the art can make various modifications or variations within the scope of the claims, which do not affect the essence of the present invention.

Claims

1. A dual-curing fluorinated epoxy adhesive, characterized in that, The dual-curing fluorinated epoxy adhesive comprises the following components in parts by weight: The epoxy resin includes one or more of the following: 3,4-epoxycyclohexylcarboxylate-3',4'-epoxycyclohexylmethyl ester, bis((3,4-epoxycyclohexyl)methyl)adipate, 3,4-epoxycyclohexylmethyl methacrylate, vinylcyclohexene dioxide, dipentene dioxide (TTA20), 3-ethyl-3-hydroxymethyloxetane, 3,3-(oxybismethylene)bis((3-ethyl)oxetane), 3-ethyl-3(-methacryloyloxymethyl)oxetane, and epoxy-modified polybutadiene; The fluorinated epoxy resin is one of 1,2-epoxy-3-(2,2,2-trifluoroethoxy)-propane and epifluoropropane.

2. The dual-curing fluorinated epoxy adhesive according to claim 1, characterized in that, The fluorine content of the fluorinated epoxy resin is 20%-65%.

3. The dual-curing fluorinated epoxy adhesive according to claim 1, characterized in that, The cationic photoinitiator includes one or more of aryl diazonium salts, diaryl iodonium salts, and ferrocene salts.

4. The dual-curing fluorinated epoxy adhesive according to claim 1, characterized in that, The cationic thermal initiator includes one or more of TR-TAG-50102, TR-TAG-50108, TR-TAG-50302, and CXC1612.

5. The dual-curing fluorinated epoxy adhesive according to claim 1, characterized in that, Additives include adhesion promoters and antioxidants.

6. The dual-curing fluorinated epoxy adhesive according to claim 5, characterized in that, The adhesion promoter mentioned is KH560.

7. The dual-curing fluorinated epoxy adhesive according to claim 6, characterized in that, The antioxidant mentioned is L-20.

8. A method for preparing the dual-curing fluorinated epoxy adhesive as described in claim 1, characterized in that, The preparation method is as follows: Mix 30-60 parts by weight of epoxy resin, 30-50 parts by weight of fluorinated epoxy resin, 0.5-3 parts by weight of cationic photoinitiator, 0.5-3 parts by weight of cationic photoinitiator, and 0.2-4 parts of additives; stir in the dark to homogenize the mixture, and then degas to obtain the final product.

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