Stabilizer applied to cationic curing composition as well as preparation method and application of stabilizer

Abstract

The invention discloses a stabilizer applied to a cationic curing composition as well as a preparation method and application thereof, and belongs to the technical field of high polymer materials. The stabilizer is a compound with a specific formula (I) structure. The stabilizer, cationic curable resin and a cationic curing agent are prepared into a composition, the viscosity increase of the composition in the storage period can be remarkably inhibited, the viscosity increase after 7-day room temperature storage can be controlled within 10%, the construction window is effectively prolonged, and meanwhile the curing efficiency and the mechanical property after curing are not affected. The action mechanism of the stabilizer is reversible dynamic stability instead of consuming active ingredients. The preparation method is simple, and raw materials are easily available. The composition is suitable for the fields of adhesives, electronic packaging materials, optical device adhesives and the like with high requirements on storage stability and reliability.

Description

Technical Field

[0001] This invention relates to the field of cationic curing materials technology, specifically to a stabilizer for use in cationic curing compositions, its preparation method, and its application. Background Technology

[0002] Cationic curing systems of epoxy resins, especially photo-thermal dual-curing systems, are widely used in high-end manufacturing fields such as electronic packaging, optical lens bonding, and precision automotive components due to their characteristics of low curing shrinkage, low internal stress, excellent resistance to damp heat, and superior electrical properties. The core of this system lies in the fact that the cationic initiator generates a strong protic acid under the action of light or heat, thereby initiating the ring-opening polymerization of epoxy groups.

[0003] Stabilizers, as core additives for regulating the overall performance of cationic curing compositions, have evolved from early "simple polymerization inhibition" to multi-dimensional regulation involving "targeted inhibition of specific degradation / crosslinking pathways," "compatibility with functional component activity," and "adaptation to multiple system curing mechanisms." However, existing technologies still have significant limitations in the "scenario-based adaptation" and "multi-performance balance" of storage stabilizers. Most existing stabilizers focus only on a single performance. For example, the hindered phenolic and phosphite stabilizers disclosed in Chinese invention patent CN112601770B primarily function as antioxidants and anti-aging agents, contributing very little to viscosity stability and thus failing to achieve their intended effect. To meet the viscosity control requirements during storage, the N-dodecylpyrrolidone stabilizer used in Chinese invention patent CN114736650B can temporarily stabilize free cations, but long-term storage will consume cations, leading to a decrease in curing speed. Moreover, its long-chain structure is not conducive to the use of automotive-grade adhesives, limiting its applicability. The borate ester stabilizer used in Chinese invention patent application CN118360018A requires a preemptive reaction to consume free cations to achieve stability. Not only is the addition amount as high as 0.5-5% and the raw materials expensive, but it may also affect the final bonding performance, resulting in poor economy and practicality.

[0004] Therefore, there is an urgent need to develop a new stabilizer solution that is compatible with different curing systems and can take into account weather resistance, low shrinkage, release compatibility and storage stability. Summary of the Invention

[0005] The purpose of this invention is to overcome the shortcomings of existing technologies and provide a stabilizer for use in cationic curing compositions, its preparation method, and its application. Through a non-deactivating stabilization mechanism, it significantly improves storage stability while ensuring high curing efficiency and excellent adhesive strength of the cationic curing composition. Furthermore, it requires a small dosage, has controllable costs, and is suitable for various application scenarios.

[0006] To achieve this objective, the present invention adopts the following technical solution: In a first aspect, the present invention provides a stabilizer for use in cationic curing compositions, which is a compound having the structure of formula (I): Formula (I); in: R1 and R2 are each independently selected from hydrogen, benzyl, or C1-C7 alkyl groups. R3 is selected from carboxyl, methyl, benzyl or C1-C7 alkyl; R4 is selected from methyl, C1-C7 alkyl, sulfonyl, formyl or acetyl; R5 is hydrogen, hydroxyl, benzyl, C1-C7 alkyl, or C1-C7 alkoxy.

[0007] Optionally, the raw materials for preparing the stabilizer include: aspartic acid or its derivatives, solvent, and amide condensation catalyst.

[0008] Optionally, the aspartic acid or its derivatives include one of aspartic acid, L-aspartic acid, D-aspartic acid, DL-aspartic acid, methylaspartic acid, 3-hydroxyaspartic acid, L-pyroglutamic acid, aspartic acid diester, L-aspartic acid benzyl ester, and aspartic acid ester.

[0009] The stabilizer of the present invention can introduce functional groups into the stabilizer molecule by selecting derivatives of different substituents, thereby regulating the hydrophilicity / hydrophobicity, thermal stability and compatibility with cationic curing systems of the final product.

[0010] The solvent includes one or more of toluene, xylene, methyl isobutyl ketone, butanone, acetone, dichloromethane, cyclohexane, or chloroform.

[0011] The amide condensation catalyst includes one or more of dicyclohexylcarbodiimide, diisopropylcarbodiimide, 1-(3-dimethylaminopropyl)-3-ethylcarbodiimide, and N,N'-carbonyldiimidazole.

[0012] Secondly, the present invention provides a method for preparing the above-mentioned stabilizer, characterized by comprising the following steps: (1) Dissolve aspartic acid or its derivatives in a solvent to form a reaction solution; (2) Add an amide condensation catalyst to the reaction solution to carry out the amide condensation reaction and obtain the mixture after the reaction; (3) The mixture after the reaction is separated and purified to obtain the stabilizer.

[0013] Thirdly, the present invention provides a cationic curing composition comprising: i) at least one cationic curable resin; ii) At least one cationic curing agent; iii) Includes at least the stabilizers described above.

[0014] Optionally, the amount of stabilizer added is 0.01% to 1% of the total weight of the composition.

[0015] Optionally, the cationic curing composition further includes fillers and / or additives.

[0016] Further optionally, the filler includes one or more of the following: FB-3SDC and FB-5SDC from Denka Co., Ltd., R202 from Evonik, SE6200 and SE4050 from Adema, M03C10 and M10C20 from Huafeng Electronics Technology Co., Ltd., SJS-0060SO*7 from Yishitong, or NQ1040G and NQ5050G from Lianrui.

[0017] Further optionally, the additives include one or more of antioxidants, adhesion promoters, thixotropic agents, and color pastes.

[0018] Further optionally, the antioxidant includes one or more of Lyon's 1135, 1010, 1520, and 1790.

[0019] Further optionally, the adhesion promoter includes one or more of BYK-4500 and BYK-4509 from BYK Corporation.

[0020] Further, optionally, the colorant includes one or more of ULOMGN07PG and ULOMNC 7499 from Shanghai Juncai Technology.

[0021] Further optionally, the cationic curable resin is a cationic polymeric resin containing epoxy groups, selected from one or more of alicyclic epoxy resins, glycidyl epoxy resins, epoxy modified polymers, and epoxy group condensation products.

[0022] Alternatively, the cationic curing agent may be composed of both a cationic and anionic components.

[0023] Fourthly, the present invention provides the application of the above-described cationic curing composition in adhesives, sealants, coatings, inks, dental materials, 3D printing resins, and optical or electronic device encapsulation materials.

[0024] Beneficial effects 1. The stabilizer of the present invention achieves a "non-deactivating stabilization" mechanism through the synergistic effect of the structure of formula (I) and specific substituents. It adsorbs free cations through coordination rather than consuming cations, thereby fundamentally inhibiting the viscosity growth of the cationic curing composition during the storage period.

[0025] 2. The stabilizer of this invention has strong synergistic effects with components such as cationic curable resin, cationic curing agent, and functional additives. While significantly improving storage stability, it does not affect the curing efficiency and final performance of the composition.

[0026] 3. The stabilizer of this invention can flexibly adjust its structure in various ways. R2 and R3 can form a cyclic structure through ethyl linkage. R1, R2, and R3 can serve as grafting sites for grafting with comb-type polymers, making it adaptable to various systems such as pure cationic curing and cationic-radical dual curing. The corresponding compositions can be widely used in adhesives, coatings, optical device packaging materials, electronic device packaging materials, etc., especially suitable for high-precision and high-reliability scenarios such as camera AA processes and automotive electronic fixation, solving the problem of poor scenario adaptability of existing stabilizers.

[0027] 4. The core raw materials of the stabilizer of this invention are amino acids such as aspartic acid, which are widely available. Its preparation method is a classic amide condensation reaction, which is simple, mild, and easy to scale up for production. Detailed Implementation

[0028] The claims of the present invention will be further described in detail below with reference to specific embodiments, but this does not constitute any limitation on the present invention. Any limited modifications made by any person within the scope of the claims of the present invention are still within the protection scope of the claims of the present invention.

[0029] Unless otherwise specified, the following embodiments are all conventional experimental methods and operating procedures in the art.

[0030] Cationic curable resins The cationic curable resin of the present invention is selected from epoxy compounds having epoxy groups, and can be used alone or in combination of two or more. Specifically, the cationic curable resin includes, but is not limited to, the following general formula compounds and specific substances: (1) General-type cationic curable resin The cationic curable resin may be selected from compounds represented by the following general formulas S1, S2 or S3: S1

[0031] Where R is hydrogen or C3-C 12 Alkanes; S2

[0032] Where R represents hydrogen, C3-C 12 One of the following: alkane, polyethylene glycol structure, or cyclohexyl group; S3

[0033] Where R is H or methyl; (2) Specific categories and examples As a preferred embodiment, the cationic curable resin may be selected from one or more of epoxide resins, glycidyl ether resins, glycidyl amine resins, and glycidyl ester resins, as exemplified below: 1) Ester ring resins: can be selected from TTA800, TTA21, TTA22, TTA20, TTA3150, TTA27, TTA26, TTA12 from Tetel Chemicals; one or more of CELLOXIDE 2021P, CELLOXIDE 8010, CELLOXIDE 3150 from Daicel; Donghua S-06E; Dow UVR6105, UVR6110; diglycidyl tetrahydrophthalate; and diglycidyl hexahydrophthalate. 2) Glycidyl ether, glycidyl amino, glycidyl ester resins: can be selected from bisphenol F diglycidyl ether, bisphenol F diglycidyl ether and mixtures of other resins; specific examples include one or more of Dow's DER337, DER331, E-44 resin, E-51 resin, Kaneka MX-154, MX555.

[0034] 3) Special forms of cationic curable resins In addition to the resins listed above, the cationic curable resin may also be a polycondensation product of any of the above-mentioned epoxy compounds, acidic compounds, oligomers and their derivatives; wherein the acidic compounds and their derivatives may be selected from carboxylic acids, alcohols and / or thiols. As a particularly preferred embodiment, the polycondensation product may be an adduct of reactive liquid rubber and epoxy, specifically an adduct of amino-terminated nitrile rubber and epoxy, or an adduct of carboxyl-terminated nitrile rubber and epoxy.

[0035] It should be noted that at least one of the cationic curable resins selected in this invention is a bifunctional or higher-functionality epoxy-containing compound; combinations of two or more epoxy-containing compounds of different functionalities and types are also within the scope of protection of this invention.

[0036] cationic curing agent The cationic curing agent selected in this invention consists of a cationic portion and an anionic portion. Only the cationic portion is listed in the cationic curing agent, and the anionic portion can be selected from the structure shown in the following general formula S4. The cationic portion and the anionic portion can be combined in pairs to form the cationic curing agent. A mixture of two or more of the cationic curing agents can also be used in the embodiments of this invention.

[0037] (1) General structure of cationic curing agents 1) S4 anion portion:

[0038] 2) S5 cation moiety:

[0039]

[0040] In general formula S5, R can be a hydrogen atom, methyl, ethyl, acetyl, or isopropyl.

[0041] (2) Specific categories and examples As a preferred embodiment, the cationic curing agent may be selected from the following specific substances: CXC-1621 and CXC-1821 from King's Chemical; TA-100, TA-100FG, AA-01, IK-1, IK-1FG, IK-20B, or UVI-6976 and UVI-6992 from SAN-APRO.

[0042] In addition to the cationic curing agents listed above, products obtained by modifying compounds with the structures shown in general formulas S4 and S5 can also be used as cationic curing agents of the present invention. For example, modified products obtained by replacing the side groups of the benzene ring in the above structure with derivatives can achieve a curing effect similar to that of the above cationic curing agents, and such modified products are also within the protection scope of the present invention.

[0043] Example The grades and suppliers of the raw materials used in specific embodiments 1-11 and comparative examples 1-3 are shown in Table 1. Table 1

[0044] The formulations of specific embodiments 1-11 and comparative examples 1-3 are shown in Table 2: Table 2

[0045] Preparation method of cationic curing stabilizer A The cationic curing stabilizer A involved in this invention is synthesized by the following method, the specific steps of which are as follows: 1) Weigh 33g of DL-aspartic acid as raw material. Prepare a 0.5mol% sodium hydroxide aqueous solution for later use; 2) Dissolve the above-mentioned DL-aspartic acid in 500 mL of dichloromethane, which contains the aforementioned dilute NaOH alkaline solution (whose mass is 1% of the mass of dichloromethane), to prepare a reaction solution with a DL-aspartic acid mass concentration of approximately 5 wt%, and stir at room temperature for 2 h until the DL-aspartic acid is completely dissolved.

[0046] 3) Add 50g of dicyclohexylcarbodiimide to the completely dissolved solution and stir to react; control the reaction temperature at 20-30℃ and stir at 50r / min for 6-8h.

[0047] 4) After the reaction is complete, filter the reaction solution to remove insoluble matter. Then add an equal volume of petroleum ether (boiling range 60-90℃) to the filtrate and stir for 1 hour to allow the product to fully separate. After standing and separating the liquid, collect the lower precipitate, filter, and obtain the solid crude product.

[0048] 5) The solid product is vacuum dried at 80-150℃ to obtain an amber-colored solid product, denoted as stabilizer A. To obtain a higher purity product, the above solid can be redissolved in dichloromethane and precipitated again with petroleum ether. This purification process is repeated 3 times.

[0049] Preparation of cationic curing composition samples First, add the cationic curable resin to the container, then add the stabilizer A prepared above and fumed silica, and disperse it for 120s using a homogenizer at a speed of 2500 r / min and a vacuum of -0.1 MPa; then add spherical silica, and disperse it for 120s at the same speed of 2500 r / min and a vacuum of -0.1 MPa; after cooling to below 40°C, add the cationic curing agent dissolved in propylene carbonate at 50%, and mix evenly to obtain the cationic curing composition sample.

[0050] Performance testing 1. Viscosity testing: Anton Paar MCR302 rotational rheometer was used, with a PP40 rotor and a 500μm gap. The shear rate was tested at 10. - Viscosity at ¹s, in cps, with the viscosity 6 hours after sample preparation as the initial value (0d viscosity), the viscosity after 3d and 7d storage at room temperature was tested respectively, and the viscosity increase ratio at 7d was calculated (viscosity increase ratio = (7d viscosity - 0d viscosity) / 0d viscosity × 100%).

[0051] 2. Bond strength test: The specimens were cured by pure heat curing (100℃, 30min), and after cooling for 24h, tensile tests were performed according to ISO527 standard. Tensile specimens were made from 100mm×25mm×2mm aluminum sheets, with a bonding area of ​​25mm×12.5mm², a tensile speed of 5mm / min, and the bond strength (unit: MPa) was recorded.

[0052] The performance test results of each embodiment and comparative sample are shown in Table 3 below: Table 3

[0053] As can be seen from Table 3, The system without cationic curing agent and stabilizer (Comparative Example 1) showed slow viscosity growth but failed to cure. The system containing cationic curing agent but without stabilizer (Comparative Example 2) showed a dramatic viscosity increase of 420.63% after 7 days of storage, indicating extremely poor storage stability.

[0054] After adding stabilizers A or B of the present invention (Examples 1, 2, 5, 6), the storage stability of the composition was greatly improved, with the 7-day thickening rate all below 13%, and even slightly decreased in the dual-curing system (Example 5), demonstrating excellent stability. Meanwhile, the bond strength after curing remained at a high level, significantly improved compared to the unstable system (Comparative Example 2, strength 5.32 MPa), proving that the stabilizer did not impair the curing performance.

Claims

1. A stabilizer for use in cationic curing compositions, characterized in that, The stabilizer applied to the cationic curing composition is a compound having the following structure (I): Equation (I); in: R1 and R2 are each independently selected from hydrogen, benzyl, or C1-C7 alkyl groups. R3 is selected from carboxyl, methyl, benzyl or C1-C7 alkyl; R4 is selected from methyl, C1-C7 alkyl, sulfonyl, formyl or acetyl; R5 is hydrogen, hydroxyl, benzyl, C1-C7 alkyl, or C1-C7 alkoxy.

2. The stabilizer according to claim 1, characterized in that, The raw materials for preparing the stabilizer include: aspartic acid or its derivatives, solvent, and amide condensation catalyst.

3. The stabilizer according to claim 2, characterized in that, The aspartic acid or its derivatives include one of aspartic acid, L-aspartic acid, D-aspartic acid, DL-aspartic acid, methylaspartic acid, 3-hydroxyaspartic acid, L-pyroglutamic acid, aspartic acid diester, L-aspartic acid benzyl ester, and aspartic acid ester.

4. The stabilizer according to claim 2, characterized in that, The solvent includes one or more of toluene, xylene, methyl isobutyl ketone, butanone, acetone, dichloromethane, cyclohexane, or chloroform.

5. The stabilizer according to claim 2, characterized in that, The amide condensation catalyst includes one or more of dicyclohexylcarbodiimide, diisopropylcarbodiimide, 1-(3-dimethylaminopropyl)-3-ethylcarbodiimide, and N,N'-carbonyldiimidazole.

6. A method for preparing the stabilizer according to any one of claims 1-5, characterized in that, Includes the following steps: (1) Dissolve aspartic acid or its derivatives in a solvent to form a reaction solution; (2) Add an amide condensation catalyst to the reaction solution to carry out the amide condensation reaction and obtain the mixture after the reaction; (3) The mixture after the reaction is separated and purified to obtain the stabilizer.

7. A cationic curing composition, characterized in that, include: i) at least one cationic curable resin; ii) At least one cationic curing agent; iii) Includes at least the stabilizer as described in any one of claims 1-5.

8. The cationic curing composition according to claim 7, characterized in that, The amount of stabilizer added is 0.01-1% of the total weight of the cationic curing composition.

9. The cationic curing composition according to claim 7, characterized in that, The cationic curing composition further includes fillers and / or additives.

10. The application of a cationic curing composition according to any one of claims 7-9, characterized in that, Application of the cationic curing composition in adhesives, coatings, inks, dental materials, printing resins, optical device encapsulation materials, or electronic device encapsulation materials.

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