An antioxidant polydithiocarbamate adhesive, its preparation method and application

Abstract

This invention discloses an antioxidant polydisulfide carbamate adhesive, its preparation method, and its application. The preparation method includes adding 0.10% to 0.20% (by mass of bis[3,5-bis(trifluoromethyl)phenyl]diselener) to the polydisulfide carbamate adhesive reaction system. This invention uses bis[3,5-bis(trifluoromethyl)phenyl]diselener as a free radical absorber to add to the MP-type polydisulfide carbamate adhesive system. This free radical absorber can capture free radicals generated during long-term use of the adhesive system, inhibiting oxidative chain reactions, thereby improving the antioxidant properties and long-term bonding stability of the adhesive. Samples can remain bonded even after more than 100 days without falling off. It is suitable for long-term bonding of stainless steel and other metal substrates, as well as hard substrates such as glass and ceramics.

Description

Technical Field

[0001] This invention relates to adhesive materials technology, specifically to an antioxidant polydisulfide urethane adhesive, its preparation method, and its application. Background Technology

[0002] Adhesives are widely used for connecting and fixing metals, glass, electronic devices, optical materials, and structural components. Compared with mechanical joining methods, adhesives have advantages such as uniform stress distribution, ease of operation, and a wide range of applicable substrates. However, some sulfur-containing adhesives are susceptible to oxidative aging due to the influence of air, heat, oxygen, or free radicals during long-term use, leading to discoloration, embrittlement, powdering, or decreased adhesive performance, thus limiting their long-term stability.

[0003] Polydithiocarbamates are typically prepared by reacting isothiocyanate compounds with mercapto-containing compounds. These materials contain abundant sulfur-containing structures, exhibiting good adhesive properties and structural designability, thus showing potential application in functional adhesives. However, the sulfur-containing structures may be affected by oxidation during long-term use, leading to a decline in adhesive performance. Therefore, improving the oxidation resistance and long-term stability of polydithiocarbamate adhesives while maintaining their good adhesive properties is a problem that needs to be solved for further application of these materials. Summary of the Invention

[0004] To address the current issues of insufficient antioxidant properties and long-term stability of polydisulfide carbamate adhesives, this invention provides an antioxidant polydisulfide carbamate adhesive, its preparation method, and its application. By adding bis[3,5-bis(trifluoromethyl)phenyl]diselenes to the MP-type polydisulfide carbamate adhesive system, the antioxidant properties of the adhesive are improved.

[0005] To achieve the above objectives, the present invention provides a method for preparing an antioxidant polydisulfide carbamate adhesive, comprising: adding 0.10% to 0.20% of bis[3,5-bis(trifluoromethyl)phenyl]diselenes by mass of the total mass of the adhesive system to the polydisulfide carbamate adhesive reaction system.

[0006] bis[3,5-bis(trifluoromethyl)phenyl]diselenoether is a selenium-containing organic compound with Se-Se bonds and fluorinated aromatic groups in its structure. It can act as a free radical absorber to capture free radicals in the system. The trifluoromethyl group enhances its hydrophobicity and improves material properties; on the other hand, the strong electron-withdrawing group increases its polarity, which is beneficial for enhancing adhesion. This invention introduces this diselenoether compound into a polydisulfide urethane adhesive system, thereby inhibiting the oxidative aging of the adhesive system and improving long-term bonding stability.

[0007] Preferably, the amount of bis[3,5-bis(trifluoromethyl)phenyl]diselelenide is 0.13% to 0.16% of the total mass of the adhesive system.

[0008] More preferably, the amount of bis[3,5-bis(trifluoromethyl)phenyl]diselelenide is 0.15% of the total mass of the adhesive system.

[0009] Specifically, the polydithiocarbamate adhesive reaction system includes 1,3-propanediisothiocyanate and pentaerythritol tetra-3-mercaptopropionate in a molar ratio of (1.8 to 2.1):1, and the amount of catalyst used is 1 to 1.2% of the total molar amount of the adhesive system.

[0010] Specifically, the preparation method of the antioxidant polydisulfide carbamate adhesive includes the following steps: 1,3-propanediisothiocyanate, pentaerythritol tetra-3-mercaptopropionate, and catalyst are mixed, and then bis[3,5-bis(trifluoromethyl)phenyl]diselenes are added and uniformly dispersed to allow the mixed system to undergo addition and crosslinking reactions to obtain the antioxidant polydisulfide carbamate adhesive.

[0011] In the above technical solution, 1,3-propanediisothiocyanate (C3-DITC) and PETMP are used as the main reaction components, and the catalyst is tris(2-ethylhexyl)amine (EHA). The two form a polydithiocarbamate crosslinked network through the addition reaction between isothiocyanate groups and mercapto groups.

[0012] Add bis[3,5-bis(trifluoromethyl)phenyl]diselenoether to the above-mentioned basic adhesive system at an amount of 0.1% to 0.2% of the total mass of the adhesive system, preferably 0.15%. This free radical absorber can capture free radicals generated in the adhesive system during long-term use, inhibit oxidative chain reactions, thereby improving the antioxidant properties and long-term bonding stability of the adhesive.

[0013] Specifically, the reaction conditions are: 20–30 h at room temperature.

[0014] The second aspect of the present invention provides an antioxidant polydithiocarbamate adhesive prepared by the above-described preparation method.

[0015] A third aspect of the present invention provides the application of the above-described antioxidant polydisulfide urethane adhesive in bonding rigid substrates.

[0016] Preferably, the rigid substrate is metal, glass, or ceramic.

[0017] More preferably, the metal substrate is stainless steel.

[0018] Through the above technical solution, the present invention achieves the following beneficial effects: 1. This invention adds bis[3,5-bis(trifluoromethyl)phenyl]diselelenide as a free radical absorber to the MP type polydisulfide urethane adhesive system. This free radical absorber can capture free radicals generated in the adhesive system during long-term use, inhibit the oxidation chain reaction, thereby improving the antioxidant properties and long-term bonding stability of the adhesive, and can ensure that the sample does not fall off after more than 100 days.

[0019] 2. This invention does not require the addition of large amounts of antioxidants, and the amount added is low, which has little impact on the composition and preparation process of the basic adhesive system. It is suitable for long-term bonding of metal substrates such as stainless steel and hard substrates such as glass and ceramics, and has application prospects in the fields of electronic device fixing, equipment component bonding, and aging-resistant structural adhesive materials. Attached Figure Description

[0020] Figure 1 The FTIR spectrum of the pre-reaction mixture of C3-DITC / MP / EHA / bis[3,5-bis(trifluoromethyl)phenyl]diselelenide; Figure 2 The FTIR spectrum of the solid sample of C3-DITC / MP / EHA / bis[3,5-bis(trifluoromethyl)phenyl]diselenes after reaction at 25°C for 24 h. Figure 3 This is a diagram showing the state of the adhesive forming a bonding layer on the surface of a stainless steel block. Figure 4 This is an experimental diagram showing the stability test of an inverted bonding after a stainless steel block is glued to the top of the device using adhesive. Detailed Implementation

[0021] The specific embodiments of the present invention will be described in detail below with reference to examples. It should be understood that the specific embodiments described herein are for illustration and explanation only and are not intended to limit the present invention.

[0022] The CAS Registry Numbers and purchase channels of the reagents used in the following examples are shown in Table 1.

[0023] Table 1. CAS Registry Numbers and Purchase Channels of Reagents Used in the Experiment

[0024] 1,3-Propanediisothiocyanate (C3-DITC) can be synthesized according to the method reported in the literature for preparing isothiocyanates from primary amines via dithiocarbamate intermediates (DOI: 10.1055 / s-0037-1612303). In the following examples, 1,3-propanediamine was used as a starting material, and a dithiocarbamate intermediate was formed by the reaction of carbon disulfide, ethyl chloroformate, and triethylamine. Subsequently, the intermediate was heated under reflux in 1,4-dioxane to obtain C3-DITC.

[0025] Example 1 1 mol of C3-DITC was mixed with 0.5 mol of PETMP, followed by the addition of 0.015 mol of catalyst EHA and 0.10% by mass of bis[3,5-bis(trifluoromethyl)phenyl]diselenes, allowing the isothiocyanate groups to undergo an addition reaction with the mercapto groups. The mixture was stirred thoroughly and then allowed to react and cure at 25°C to obtain an antioxidant polydisulfide urethane adhesive.

[0026] The FTIR test was performed on the system before the reaction, and the results are as follows: Figure 1 As shown. FTIR tests were performed on the adhesive system after 24 hours of reaction, and the results are as follows. Figure 2 As shown in the figure, characteristic absorption peaks such as NH, CN, C=S and CS, which are related to the structure of polydisulfurethane, appear in the spectrum after the reaction, indicating that C3-DITC and PETMP undergo an addition reaction to form a polydisulfurethane adhesive system.

[0027] Example 2 0.9 mol C3-DITC and 0.5 mol PETMP were mixed, followed by the addition of 0.0168 mol EHA catalyst and 0.10% (by mass) of bis[3,5-bis(trifluoromethyl)phenyl]diselenes, allowing the isothiocyanate groups to undergo an addition reaction with the mercapto groups. The mixture was stirred thoroughly and then allowed to react and cure at 25°C to obtain an antioxidant polydisulfide carbamate adhesive.

[0028] Example 3 1.05 mol C3-DITC and 0.5 mol PETMP were mixed, followed by the addition of 0.017 mol EHA catalyst and 0.10% (by mass) of bis[3,5-bis(trifluoromethyl)phenyl]diselenes to allow the isothiocyanate groups to undergo an addition reaction with the mercapto groups. The mixture was stirred thoroughly and then allowed to react and cure at 25°C to obtain an antioxidant polydisulfide urethane adhesive.

[0029] Examples 4-7 Other conditions are the same as in Example 1, except that the amount of bis[3,5-bis(trifluoromethyl)phenyl]diselelenide added is 0.13%, 0.15%, 0.16%, and 0.20% of the total mass of the adhesive system.

[0030] Comparative Example Other conditions are the same as in Example 1, except that bis[3,5-bis(trifluoromethyl)phenyl]diselenoether is not added.

[0031] The adhesives obtained in the examples and comparative examples were used in the inverted bonding experiment of stainless steel blocks. The specific method was as follows: 0.1 g of adhesive was applied to the surface of the stainless steel block and bonded to the top of the device, so that the stainless steel block was in an inverted state, and the time required for the stainless steel block to fall from the top of the device was recorded. The results are shown in Table 2.

[0032] Table 2 Test results of adhesive stability at the top of stainless steel block

[0033] Table 2 shows that the control group (comparative example) without bis[3,5-bis(trifluoromethyl)phenyl]diselenoether detached after 22 days; when the amount of bis[3,5-bis(trifluoromethyl)phenyl]diselenoether added was 0.10 wt%, the stainless steel block detached after 75 days; when the amount of bis[3,5-bis(trifluoromethyl)phenyl]diselenoether added was 0.13 wt%, the stainless steel block detached after 97 days; and when the amount of bis[3,5-bis(trifluoromethyl)phenyl]diselenoether added was 0.15–0.20 wt%, the stainless steel block did not detach after more than 100 days. This indicates that the diselenoether compound can exert free radical absorption at low addition levels, inhibiting the oxidative aging of the adhesive system during long-term use, thereby significantly improving the long-term bonding stability of the adhesive. Among them, when the addition amount of bis[3,5-bis(trifluoromethyl)phenyl]diselenoether is 0.15 wt%, the content of free radical absorber is relatively low, and the ability to capture free radicals generated during long-term use of the adhesive system is relatively insufficient, resulting in limited antioxidant protection, but the effect is relatively good. When its addition amount is higher than 0.15 wt%, further increasing the amount of free radical absorber does not significantly improve the antioxidant performance, and may affect the uniform mixing and crosslinking network formation between C3-DITC and MP-type crosslinking agent, as well as increase material costs. Therefore, considering the free radical absorption effect, system compatibility, crosslinking structure stability, and economy, about 0.15 wt% is determined to be the preferred addition amount, such as 0.13 to 0.16 wt%.

[0034] The preferred embodiments of the present invention have been described in detail above. However, the present invention is not limited to the specific details in the above embodiments. Within the scope of the technical concept of the present invention, various simple modifications can be made to the technical solution of the present invention, and these simple modifications all fall within the protection scope of the present invention.

[0035] It should also be noted that the various specific technical features described in the above specific embodiments can be combined in any suitable manner without contradiction. In order to avoid unnecessary repetition, the present invention will not describe the various possible combinations separately.

[0036] Furthermore, various different embodiments of the present invention can be combined in any way, as long as they do not violate the spirit of the present invention, they should also be regarded as the content disclosed by the present invention.

Claims

1. A method for preparing an antioxidant polydithiocarbamate adhesive, characterized in that, include: Add 0.10% to 0.20% of bis[3,5-bis(trifluoromethyl)phenyl]diselenes by mass of the total adhesive system to the polydisulfide urethane adhesive reaction system.

2. The preparation method according to claim 1, characterized in that, The amount of the bis[3,5-bis(trifluoromethyl)phenyl]diselenoether is 0.13% to 0.16% of the total mass of the adhesive system.

3. The preparation method according to claim 2, characterized in that, The amount of the bis[3,5-bis(trifluoromethyl)phenyl]diselenoether used is 0.15% of the total mass of the adhesive system.

4. The preparation method according to claim 1, characterized in that, The polydithiocarbamate adhesive reaction system includes 1,3-propanediisothiocyanate and pentaerythritol tetra-3-mercaptopropionate in a molar ratio of (1.8 to 2.1):1, and the amount of catalyst used is 1 to 1.2% of the total molar amount of the adhesive system.

5. The preparation method according to claim 1, characterized in that, The process includes the following steps: mixing 1,3-propanediisothiocyanate with pentaerythritol tetra-3-mercaptopropionate and a catalyst, then adding bis[3,5-bis(trifluoromethyl)phenyl]diselenes and dispersing them uniformly, allowing the mixture to undergo addition and crosslinking reactions to obtain the antioxidant polydisulfide carbamate adhesive.

6. The preparation method according to claim 5, characterized in that, The reaction conditions were: 20–30 h at room temperature.

7. The antioxidant polydithiocarbamate adhesive prepared by any one of claims 1 to 6.

8. The application of the antioxidant polydithiocarbamate adhesive of claim 7 in bonding rigid substrates.

9. The application according to claim 8, characterized in that, The rigid substrate is a metal substrate, a glass substrate, or a ceramic substrate.

10. The application according to claim 9, characterized in that, The metal substrate is stainless steel.

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