Preparation and application of benzophenone ketone enamine visible light initiator

Abstract

The invention provides preparation and application of a benzophenone ketone enamine visible light initiator. The benzophenone keto enamine is a compound with a structural formula as shown in a formula (I). The benzophenone keto enamine provided by the invention is an LED visible light initiator, can be used as a single-component photoinitiator and can also be compounded with other substances for initiation, and when the benzophenone keto enamine provided by the invention is used as the photoinitiator, the initiation effect is good, and the benzophenone keto enamine can be adapted to an LED light source of 405-470 nm.

Description

Technical Field

[0001] This invention relates to the field of photoinitiators, and more specifically, to the preparation and application of a benzophenone keteneamine visible light initiator. Background Technology

[0002] Photoinitiators are the core components of photopolymerization technology, and their performance directly determines the polymerization efficiency and product quality. They are widely used in coatings, inks, electronic materials, and other fields. 1,6-Hexanediol diacrylate (HDDA), as a commonly used bifunctional monomer, is widely used in coatings, inks, adhesives, and other fields due to its good reactivity and excellent mechanical properties after curing. HDDA molecules contain two acrylate groups, which can form a highly cross-linked network structure during photopolymerization, giving the cured product characteristics such as high rigidity, high modulus, and good solvent resistance. The photopolymerization reaction of HDDA usually needs to be carried out at low temperatures to avoid monomer decomposition or side reactions caused by high temperatures. The photopolymerization behavior of HDDA is closely related to the photoinitiator used; selecting a suitable initiator system is crucial for optimizing the polymerization process and the performance of the final product.

[0003] HDDA photoinitiators mainly include benzophenone photoinitiators and acylphosphide photoinitiators. Benzophenone photoinitiators have strong absorption in the ultraviolet region but weak absorption in the visible light region. Studies have also confirmed that substances containing chalcone structures can be used as photoinitiators for the free radical polymerization of HDDA. However, photoinitiators for HDDA polymerization still face challenges. For example, the bonding efficiency and uniformity of photoinitiators in HDDA and other polymerization systems still need optimization. Furthermore, the compatibility of photoinitiators with long-wavelength light sources urgently needs improvement. Developing photoinitiators capable of operating at visible light wavelengths remains a current research hotspot, as existing initiators have relatively low molar extinction coefficients in the visible light region. Summary of the Invention

[0004] The primary objective of this invention is to provide a benzophenone keteneamine with the structural formula shown in formula (I). This benzophenone keteneamine is a visible light initiator with a high molar extinction coefficient and good initiation effect.

[0005] Formula (I).

[0006] Another object of the present invention is to provide the application of benzophenone keteneamine having the structure shown in formula (I) in the preparation of visible light initiators.

[0007] The benzophenone ketene provided by this invention can be used as a single-component photoinitiator. When used as a single-component photoinitiator, its initiation effect is far superior to that of the benzophenone LED visible light initiator previously developed by the applicant.

[0008] In a preferred embodiment of the present invention, the visible light initiator is initiated under LED light. Preferably, the wavelength of the LED light can be 385nm~470nm, more preferably 405nm~470nm, and even more preferably 435nm~470nm. That is, under LED light of 435nm~470nm, the benzophenone keteneamine provided by the present invention has the best photoinitiation effect.

[0009] The benzophenone keteneamine provided by this invention, when used as a visible light initiator, can be used to initiate free radical polymerization, cationic polymerization, or free radical-cationic polymerization, such as the polymerization of acrylate monomers, and is preferably used to initiate the polymerization of HDDA. In a preferred embodiment of this invention, the mass of the benzophenone keteneamine visible light initiator provided by this invention is no more than 5 × 10⁻⁶ of the mass of the polymerizing monomer. -3 Preferably not higher than 2×10 -3 .

[0010] In an optional embodiment of the present invention, benzophenone ketene amine provided by the present invention can be used as a single-component visible light initiator to initiate the polymerization reaction of HDDA. Alternatively, benzophenone ketene amine provided by the present invention can be used in combination with initiators such as N-methyldiethanolamine to initiate the polymerization reaction of HDDA. When using a combination of N-methyldiethanolamine and the benzophenone ketene amine visible light initiator provided by the present invention, the mass ratio of N-methyldiethanolamine to the benzophenone ketene amine visible light initiator is 3:1 to 1:1. Within this ratio range, the initiation efficiency is the highest. Furthermore, the applicant has also found that when benzophenone ketene amine provided by the present invention is used as a single-component visible light initiator to initiate the polymerization reaction of HDDA, the best photoinitiation effect is observed under LED light at 405nm to 470nm. When benzophenone ketene amine provided by the present invention is used in combination with initiators such as N-methyldiethanolamine to initiate the polymerization reaction of HDDA, the best photoinitiation effect is observed under LED light at 435nm to 470nm.

[0011] In an optional embodiment of the present invention, the light intensity of the polymerization reaction can be 60~250mW / cm². 2 For example, it can be 67W / cm 2 82W / cm 2 120mW / cm 2 128mW / cm 2 150mW / cm 2 wait.

[0012] The preparation method of benzophenone keteneamine (also known as benzophenone keteneamine visible light initiator) provided by the present invention is simple.

[0013] Another object of the present invention is to provide a method for preparing the above-mentioned benzophenone keteneamine (also known as benzophenone keteneamine visible light initiator), comprising the following steps: Trimethylol-resorcinol, 4-aminobenzophenone and solvent are mixed, refluxed, and filtered to obtain the final product.

[0014] The synthetic route for the above-mentioned benzophenone ketene amine provided by the present invention is shown in (II): (II) In a preferred embodiment of the present invention, the molar ratio of the phloroglucinol triformyl to the 4-aminobenzophenone is 1:(3~3.3). Within this ratio range, the target substance can be successfully synthesized with a high yield. In the preparation method provided in this invention, the yield of the target product is not less than 90%, preferably not less than 93%.

[0015] In an optional embodiment of the present invention, the solvent may be ethanol, methanol, tetrahydrofuran, isopropanol, N,N-dimethylformamide, toluene, 1,4-dioxane, etc., preferably ethanol. The amount of solvent used can be conventional, for example, the volume ratio of solvent to phloroglucinol is 300-450 mL / g, within which the reaction rate is optimal. In a specific embodiment of the present invention, in the above-described preparation method of benzophenone keteneamine, the reaction time can be 12 h to 48 h.

[0016] The benzophenone ketene amine provided by this invention is a visible light initiator that can be used as a single-component photoinitiator or in combination with other substances for initiation. It exhibits excellent initiation effects under LED light (with a relatively fast initiation speed; compared to existing initiators (such as 4-dimethylaminobenzophenone), when combined with other initiators, it has no induction period for monomer polymerization under 405nm~470nm LED illumination, and polymerization can be initiated immediately upon illumination) and a high conversion rate in a short time). When using the benzophenone ketene amine provided by this invention as a photoinitiator, it has a high molar extinction coefficient, good initiation effect, and is suitable for LED light sources in the range of 405nm~470nm (preferably 435nm~470nm). Attached Figure Description

[0017] Figure 1 The 1H NMR spectrum of benzophenone keteneamine (BP-A) obtained in Example 1 is shown below. Figure 2 The infrared spectra of benzophenone keteneamine (BP-A) (top), raw material phloroglucinol (middle), and raw material 4-aminobenzophenone (bottom) obtained in Example 1 are shown. Figure 3The UV-Vis absorption spectrum of benzophenone keteneamine obtained in Example 1 is shown below. Figure 4 Photopolymerization kinetics curves of HDDA polymerization initiated by benzophenone keteneamine (BP-A) / N-methyldiethanolamine (MDEA) and benzophenone (BP) / MDEA under LED@405nm are shown ((a) is the time-conversion curve, (b) is the time-conversion rate curve). Figure 5 The photopolymerization kinetics curves of HDDA polymerization initiated by benzophenone keteneamine (BP-A) / N-methyldiethanolamine (MDEA), 4-dimethylaminobenzophenone (BPNMe2) / MDEA, and benzophenone (BP) / MDEA obtained in Example 1 at LED@435nm are shown ((a) time-conversion curve, (b) time-conversion rate curve). Figure 6 Photopolymerization kinetics curves of HDDA polymerization initiated by benzophenone keteneamine (BP-A) / N-methyldiethanolamine (MDEA) and 4-dimethylaminobenzophenone (BPNMe2) / MDEA obtained in Example 1 at LED@450nm ((a) is the time-conversion curve, (b) is the time-conversion rate curve). Figure 7 Photopolymerization kinetics curves of HDDA polymerization initiated by LED at 470 nm using benzophenone keteneamine (BP-A) / N-methyldiethanolamine (MDEA) obtained in Example 1 ((a) is the time-conversion curve, (b) is the time-conversion rate curve). Figure 8 Photopolymerization kinetics curves of HDDA polymerization initiated by benzophenone keteneamine (BP-A), 4-dimethylaminobenzophenone (BPNMe2), and benzophenone (BP) obtained in Example 1 at LED@405nm are shown ((a) is the time-conversion curve, and (b) is the time-conversion rate curve). Figure 9 The photopolymerization kinetics curves of HDDA polymerization initiated by LED@435nm using benzophenone keteneamine (BP-A) and 4-dimethylaminobenzophenone (BPNMe2) obtained in Example 1 are shown ((a) is the time-conversion curve, (b) is the time-conversion rate curve). Figure 10 Photopolymerization kinetics curves of HDDA polymerization initiated by benzophenone keteneamine (BP-A) obtained in Example 1 at LED@450nm and LED@470nm. Detailed Implementation

[0018] The specific embodiments of the present invention will be described in further detail below with reference to the examples. These examples are used to illustrate the present invention, but are not intended to limit the scope of the invention.

[0019] Example 1 Preparation method of benzophenone keteneamine (BP-A) as shown in structural formula (I) Weigh (0.42 g, 2 mmol) of 2,4,6-tricarboxymethyl phloroglucinol into a 150 ml single-necked flask, add (1.242 g, 6.3 mmol) of 4-aminobenzophenone and 16 g of ethanol, add a stir bar, attach a reflux condenser, and heat to 80 °C under reflux for 24 hours. Cool, filter, and obtain a yellow solid. Dry to obtain 1.40 g of a yellow powder. The yield (actual product mass / theoretical mass * 100%) is 94%.

[0020] The 1H NMR spectrum of the yellow solid obtained in this embodiment is shown below. Figure 1 The proton NMR data are 1 H NMR (CDCl3, 500MHz): 13-14 (d, J=12.5 Hz, 3H, NH), 8.66-8.99 (d, J=13Hz, 3H, C=CH), 7.89-7.99 (m, 6H), 7.75-7.82 (m, 6H), 7.59-7.66 (m, 3H), 7.49-7.56 (m,6H), 7.38-7.47 (m, 6H).

[0021] In the infrared spectrum of the benzophenone ketene obtained in this embodiment, as shown... Figure 2 As shown, 2900cm -1 Aldehyde CH stretching vibration peak and 3200-3500 cm⁻¹ -1 The corresponding NH stretching vibration peak within the range disappeared significantly, indicating that the aldehyde and amine underwent a condensation reaction, and the peak was observed at 1567 cm⁻¹. -1 A strong stretching vibration peak of the ketene amine C=C double bond appeared, confirming the formation of the ketene amine bond.

[0022] The obtained benzophenone keteneamine was dissolved in THF to prepare a solution with a concentration of 8 × 10⁻⁶. -6 A solution of mol / L was used for measurement, and the results are as follows: Figure 3 As shown in the UV-Vis absorption spectrum of benzophenone ketene obtained in this embodiment, the main absorption wavelength is 417 nm, M = 747 g / mol; the concentration is 8 × 10⁻⁶. -6 mol / L.

[0023] Experimental Example HDDA polymerization reaction 1. Preparation of samples for the two-component photoinitiation system: Weigh the following components sequentially using a 1 / 10,000 analytical balance: BP-A 0.0200 g, 4-dimethylaminobenzophenone (BPNMe2) 0.0200 g, or benzophenone (BP) 0.0200 g, and N-methyldiethanolamine (MDEA) 0.0200 g (5 × 10⁻⁶ g). -4 Transfer 10.00 g of 1,6-hexanediol diacrylate (HDDA) to a 15 mL centrifuge tube and mix thoroughly by sonication.

[0024] Steps for real-time infrared detection of photoinitiation kinetics: The photocuring kinetics of the above samples were detected using real-time infrared spectroscopy, with LED light source at 405nm and illumination intensity of 82mW / cm². 2 LED at 435nm, illuminance 67mW / cm² 2 LED at 450nm, illuminance of 128 mW / cm² 2 LED at 470nm, illuminance of 120mW / cm² 2 The conversion rate-time curves of the carbon-carbon double bonds of acrylate monomers as a function of time were obtained, and the conversion rate-time curve was obtained by differentiation.

[0025] Figure 4 This is a photopolymerization kinetic curve of HDDA polymerization initiated by photoinitiator BP-A or a combination of benzophenone BP and N-methyldiethanolamine (MDEA) at LED@405nm. From... Figure 4 It can be seen that, in the presence of the co-initiator N-methyldiethanolamine (MDEA), with an LED light source at 405nm, the benzophenone-keteneamine visible light initiator (BP-A / MDEA) provided in this invention reaches its maximum photoinitiation rate of 5.32% / s at 12.5s, while the benzophenone system (BP / MDEA) reaches its maximum photoinitiation rate of 0.85% / s at 39.7s. Therefore, the BP-A system reaches its maximum photoinitiation rate the fastest, exhibiting the highest initiation speed. This is faster and has a higher conversion rate than the system using the benzophenone initiator.

[0026] Figure 5 Photopolymerization kinetics curves of HDDA polymerization initiated by photoinitiators BP-A, 4-dimethylaminobenzophenone, or a combination of benzophenone and N-methyldiethanolamine (MDEA) at LED@435nm. (From...) Figure 5It is known that in the presence of the co-initiator N-methyldiethanolamine (MDEA), and with an LED light source at 435 nm, the benzophenone-ketene-amine visible light initiation system provided by this invention has no induction period; HDDA polymerization is initiated immediately upon irradiation, reaching a maximum photoinitiation rate of 5.94% / s in 7.1 s. The BPNMe2 system has an induction period of 77.8 s, reaching a maximum photoinitiation rate of 1.58% / s after 110.5 s of illumination. The benzophenone system cannot initiate HDDA polymerization under these conditions. At 60 s, the HDDA double bond conversion rate in the BP-A system is 69.2%, while the HDDA in the BPNMe2 system has not yet begun polymerization. At 300 s, the HDDA double bond conversion rate in both the BP-A and BPNMe2 systems is 74.7%.

[0027] Figure 6 This image shows the photopolymerization kinetics of HDDA polymerization initiated by photoinitiators BP-A or a combination of 4-dimethylaminobenzophenone and N-methyldiethanolamine (MDEA) at LED@450nm. Figure 6 It can be seen that, in the presence of the co-initiator N-methyldiethanolamine (MDEA), and with an LED light source at 450 nm, the benzophenone keteneamine visible light initiation system provided by this invention still exhibits a relatively fast initiation rate and a high double bond conversion rate. It reaches a maximum photoinitiation rate of 5.50% / s at 12.5 s, a HDDA double bond conversion rate of 68.3% at 60 s, and a double bond conversion rate of 72.8% at 300 s. At this point, the BPNMe2 system no longer possesses photoinitiation activity.

[0028] Figure 7 This is a photopolymerization kinetic curve of HDDA polymerization initiated by a combination of photoinitiator BP-A and N-methyldiethanolamine (MDEA) at LED@470nm. From... Figure 7 It can be seen that, in the presence of the co-initiator N-methyldiethanolamine (MDEA) and with an LED light source at 470 nm, the benzophenone keteneamine visible light initiation system provided by this invention still exhibits a relatively fast initiation rate and a high double bond conversion rate. The maximum photoinitiation rate of 5.37% / s is reached at 12.5 s, the HDDA double bond conversion rate is 69.2% at 60 s, and the double bond conversion rate is 73.4% at 300 s.

[0029] 2. Preparation of samples for single-component photoinitiation systems Weigh 0.0200g of photoinitiator, 0.0200g of 4-dimethylaminobenzophenone, or 0.0200g of benzophenone sequentially using a 1 / 10 ...

[0030] Figure 8Photopolymerization kinetics curves of HDDA polymerization initiated by photoinitiators BP-A, 4-dimethylaminobenzophenone, or benzophenone alone at LED@405nm. From... Figure 8 It is known that when the light source is LED@405nm, the benzophenone keteneamine visible light initiator (BP-A) provided by this invention reaches its maximum photoinitiation rate of 0.81% / s at 39.7s, while the commercially available 4-dimethylaminobenzophenone (BPNMe2) reaches its maximum photoinitiation rate of 4.57% / s at 23.4s. The single-component benzophenone system (BP) cannot initiate the polymerization of HDDA. It is also known that the single-component BP-A system can initiate the polymerization of HDDA, but its photoinitiation rate is slower than that of the BPMe2 system. The benzophenone system cannot initiate polymerization.

[0031] Figure 9 Photopolymerization kinetics curves of HDDA polymerization initiated separately by photoinitiators BP-A or 4-dimethylaminobenzophenone at LED@435nm. From... Figure 9 It is known that when the light source is LED@435nm, the BP-A visible light initiation system of benzophenone keteneamine provided by this invention can initiate the polymerization of HDDA, while the BPNMe2 system cannot initiate the polymerization of HDDA.

[0032] Figure 10 Photopolymerization kinetics curves of HDDA polymerization initiated individually by photoinitiator BP-A at LED@450nm and LED@470nm, respectively. Figure 10 It is known that when the light source is LED@450nm and LED@470nm, the BP-A benzophenone keteneamine visible light initiation system provided by this invention still has initiation activity.

[0033] Finally, the method of this invention is merely a preferred embodiment and is not intended to limit the scope of protection of this invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of this invention should be included within the scope of protection of this invention.

Claims

1. A benzophenone keteneamine, characterized in that, The structural formula of the benzophenone keteneamine is shown in formula (I) below: Formula (I).

2. The application of the benzophenone keteneamine according to claim 1 in the preparation of visible light initiators.

3. The application according to claim 2, characterized in that, The visible light initiator is initiated under LED light.

4. The application according to claim 3, characterized in that, The wavelength of the LED light is 405nm~470nm.

5. The application according to claim 4, characterized in that, The wavelength of the LED light is 435nm~470nm.

6. The application according to any one of claims 2 to 5, characterized in that, The visible light initiator is a single-component visible light initiator.

7. The application according to any one of claims 2 to 5, characterized in that, The visible light initiator is used to initiate HDDA polymerization.

8. The method for preparing benzophenone keteneamine according to claim 1, characterized in that, Includes the following steps: Trimethylol-resorcinol, 4-aminobenzophenone and solvent are mixed, refluxed, and filtered to obtain the final product.

9. The preparation method according to claim 8, characterized in that, The molar ratio of the phloroglucinol to the 4-aminobenzophenone is 1:(3~3.3).

10. The preparation method according to claim 8, characterized in that, The solvent is ethanol.

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