A low migration polymerizable UV-LED photoinitiator and its preparation method and application

Abstract

The invention discloses a low migration polymerizable UV-LED photoinitiator and its preparation method and application; the invention dissolves hydroxyl-containing aldehyde derivatives and ketone derivatives in a solvent, drips an alkaline catalyst solution, stirs the reaction to generate a precipitate, and then separates and purifies the precipitate to an intermediate product; the intermediate product is dissolved in an organic solvent, an acid binding agent is added and mixed evenly, an organic solution of olefin acyl chloride compounds is dripped into the mixed solution, the reaction is stirred, and the reaction is monitored by TLC until the reaction is complete; the reaction is quenched, extracted and separated, and a low migration polymerizable UV-LED photoinitiator is purified. The photoinitiator of the present invention is a low migration, high initiation efficiency, high solubility, polymerizable ultraviolet light initiator, which is used as an ultraviolet light initiator for UV-LED light-cured coatings, inks and adhesives, and dental materials, and can achieve deep curing, and has a wide range of application prospects.

Description

Technical Field

[0001] The present invention relates to the technical field of photopolymerization, and in particular to a low migration polymerizable UV-LED photoinitiator and a preparation method and application thereof. Background Art

[0002] Photocuring can be divided into free radical type and cationic type. The essence of free radical photocuring is that the photoinitiator decomposes rapidly under light radiation to produce active free radicals, which trigger the chain reaction polymerization and crosslinking of the photocurable resin with double bonds and the active diluent. Among the many types of photoinitiators, hydroxyketone photoinitiators are the most commonly used type of photoinitiators in the field of photopolymerization. They have high initiation efficiency, good thermal stability, no yellowing phenomenon, and stable storage.

[0003] Currently available free radical II type photoinitiator ITX (thioxanthone), such as the product of my country's patent CN113861162A, is suitable for photocurable materials composed of unsaturated polyesters. Its advantage is that it has good miscibility with organic solvents. It is used for UV polymerization and curing of corresponding resins together with tertiary amine compounding agents. ITX can be used in colorless or colored systems and is widely used in conventional UV coatings. However, it has the problems of high mobility and low initiation efficiency when used in food packaging inks, cigarette packaging inks and dental materials. With the continuous development of photocuring technology, the mobility of photocurable coating initiators in various countries around the world has been continuously reduced, limiting the scope of use of such UV-LED photoinitiators.

[0004] The low migration of photoinitiators determines whether they can be used in UV photocuring systems for food packaging, cigarette packages, and dental materials. Liu Shanshan et al. conducted an in-depth analysis in the article "Research Progress on Photoinitiator Residues and Migration Laws in Food Contact Materials". Photoinitiators are an important component of UV-inks. Recent studies have found that after UV inks are cured, the residual photoinitiators can contaminate the food in the package through chemical migration or physical contact under certain conditions, thus causing potential harm to human health. Therefore, the study of low migration photoinitiators is the main development trend in the field of photocuring in the future. Summary of the invention

[0005] In view of the deficiencies in the prior art, the purpose of the present invention is to overcome the problems of high mobility and low initiation efficiency of photoinitiators in coatings, and to provide a low-migration polymerizable UV-LED photoinitiator and a preparation method and application thereof; the low-migration, high-initiation-efficiency, polymerizable UV-LED photoinitiator of the present invention is used for UV-LED light-cured coatings, has the advantages of low mobility, high initiation rate, polymerizability, etc., and the synthesis method has a high yield.

[0006] The photoinitiator with polymerizable groups of the present invention can be used as an initiator to copolymerize with oligomers to reduce the mobility of the photoinitiator.

[0007] The ketene photoinitiator developed by the present invention can effectively solve the problems of mobility and initiation efficiency, improve the application scope of the ketene photoinitiator, and has obvious advantages in environmental protection performance and economy.

[0008] To achieve the above object, the object of the present invention is achieved through the following technical solutions.

[0009] A method for preparing a low migration polymerizable UV-LED photoinitiator comprises the following steps:

[0010] (1) dissolving a hydroxyl-containing aldehyde derivative and a ketone derivative in a solvent, stirring and mixing them uniformly, then dropping a basic catalyst solution, stirring and reacting to generate a precipitate, and then separating and purifying the precipitate to obtain an intermediate product;

[0011] (2) dissolving the intermediate product in an organic solvent, adding an acid binding agent and mixing well, dropping an organic solution of an olefin chloride compound into the mixed solution, stirring to react, and monitoring the reaction by TLC until the reaction is complete; quenching the reaction, extracting and separating, and purifying to obtain a low migration polymerizable UV-LED photoinitiator.

[0012] Preferably, the structural formula of the hydroxyl-containing aldehyde derivative is as follows:

[0013]

[0014] Preferably, the structural formula of the ketone derivative is as follows:

[0015]

[0016] Preferably, the structural formula of the olefinic acid chloride compound is as follows:

[0017]

[0018] Preferably, in step (1), the molar ratio of the hydroxyl-containing aldehyde derivative to the ketone derivative is 2-3:1;

[0019] Further preferably, in step (1), the molar ratio of the hydroxyl-containing aldehyde derivative to the ketone derivative is 2:1;

[0020] Preferably, the molar amount of the alkaline catalyst in step (1) is 1-3:1 of the ketone derivative;

[0021] Preferably, the molar volume ratio of the hydroxyl aldehyde derivative to the solvent in step (1) is 1 mmol: 1-3 ml;

[0022] Preferably, the solvent in step (1) comprises one or more of ethanol, water, and methanol;

[0023] Preferably, the stirring reaction time in step (1) is 4h-8h;

[0024] Preferably, the stirring reaction temperature in step (1) is room temperature;

[0025] Preferably, the alkaline catalyst in step (1) comprises one or more of sodium hydroxide and potassium hydroxide.

[0026] Preferably, the concentration of the alkaline catalyst solution in step (1) is 1-5 mmol / ml.

[0027] Preferably, the molar ratio of the intermediate product to the olefinic acid chloride compound in step (2) is 1:2-3;

[0028] Preferably, the molar ratio of the olefin chloride compound to the acid binding agent in step (2) is 1:1-2;

[0029] Further preferably, the molar ratio of the olefin chloride compound to the acid binding agent in step (2) is 1:1;

[0030] Preferably, the molar volume ratio of the intermediate product to the organic solvent in step (2) is 1mmol:5-20ml.

[0031] Preferably, the solvent of the organic solution of the olefinic acid chloride compound in step (2) is one or both of dichloromethane and tetrahydrofuran;

[0032] Preferably, in the organic solution of the olefin acyl chloride compound in step (2), the dosage ratio of the olefin acyl chloride compound to the organic solution is 1 mmol: 0.5-2 ml.

[0033] Further preferably, in the organic solution of the olefin acyl chloride compound in step (2), the ratio of the amount of the olefin acyl chloride compound to the organic solution is 1 mmol:1 ml.

[0034] Preferably, the temperature for adding the olefin chloride compound dropwise in step (2) is 0°C-10°C;

[0035] Preferably, the stirring reaction temperature in step (2) is 0°C-6°C;

[0036] Preferably, the stirring reaction time in step (2) is 1h-3h;

[0037] Preferably, the organic solvent in step (2) is one or both of dichloromethane and tetrahydrofuran, and the acid binding agent is one or both of triethylamine and pyridine.

[0038] Preferably, the separation and purification in step (1) is washing with anhydrous ethanol, centrifuging, and drying to obtain an intermediate product;

[0039] Further preferably, the number of times of washing with anhydrous ethanol in step (1) is ≥ 3 times; the drying in step (1) is vacuum drying, and the drying temperature is 40-60°C;

[0040] Preferably, the quenching reaction in step (2) is to add an inorganic base to adjust the pH to 7-8;

[0041] Preferably, the extraction separation in step (2) is performed by adding ethyl acetate for extraction separation;

[0042] Preferably, the purification in step (2) is washing with saturated brine, drying with anhydrous sodium sulfate, removing the solvent by distillation under reduced pressure, and performing column chromatography with a mixture of petroleum ether and ethyl acetate as the mobile phase and 200-300 mesh silica gel as the stationary phase to obtain the final product.

[0043] Further preferably, the drying of anhydrous sodium sulfate in step (2) is performed by adding anhydrous sodium sulfate to ethyl acetate containing the final product, mixing and stirring evenly, and after observing that the sodium sulfate is a flowing powder, standing for 0.5-1h;

[0044] Further preferably, the volume ratio of the mixture of petroleum ether and ethyl acetate in step (2) is 1-3:1.

[0045] More preferably, the volume ratio of the mixture of petroleum ether and ethyl acetate in step (2) is 2:1.

[0046] A low migration polymerizable UV-LED photoinitiator is prepared by the above preparation method.

[0047] Preferably, the absorption wavelength of the low migration polymerizable UV-LED photoinitiator is 350-425 nm.

[0048] The application of the above-mentioned low migration polymerizable UV-LED photoinitiator in photocuring.

[0049] Compared with the prior art, the advantages and beneficial effects of the present invention are as follows:

[0050] (1) The photoinitiator of the present invention has the characteristics of low mobility, high initiation efficiency and polymerizability. In view of the shortcomings of ketene photoinitiators in terms of mobility and initiation efficiency, a low migration, high initiation efficiency and polymerizable UV-LED photoinitiator is provided. The UV-LED photocurable coating has the advantages of low mobility and high initiation rate, and effectively fills the gap in the application of ketene photoinitiators in certain fields.

[0051] (2) The present invention modifies the molecular structure, and the initiator itself contains C=C, which belongs to the polymerizable enone type UV-LED photoinitiator.

[0052] (3) The compound of the present invention is a low migration, high initiation efficiency, polymerizable UV-LED photoinitiator.

[0053] (4) The synthesis process of the compound of the present invention is simple and has high yield. BRIEF DESCRIPTION OF THE DRAWINGS

[0054] Figure 1 This is the mass spectrum of the photoinitiator in Example 2.

[0055] Figure 2 This is the H NMR spectrum of the photoinitiator in Example 2.

[0056] Figure 3 This is the NMR carbon spectrum of the photoinitiator in Example 2.

[0057] Figure 4 This is the UV-visible spectrum of the photoinitiator in Example 2.

[0058] Figure 5 Graph showing the C=C conversion rates of the photoinitiators in Examples 1-3 and the competitor ITX. DETAILED DESCRIPTION

[0059] The present invention is described in detail below in conjunction with the embodiments, but the protection scope of the present invention is not limited to the following embodiments.

[0060] The room temperature in the present invention is 20-30°C;

[0061] The room temperature in the following examples specifically refers to 25°C.

[0062] Example 1

[0063] A method for preparing a low migration polymerizable UV-LED photoinitiator comprises the following steps:

[0064] (1) m-Hydroxybenzaldehyde (20 mmol) and acetone (10 mmol) were dissolved in ethanol (40 ml), and 10 ml of sodium hydroxide aqueous solution (2.5 mmol / ml) was added dropwise to the reaction system. The mixture was stirred at room temperature for 4 h. A yellow precipitate appeared during the reaction. The precipitate was washed three times with anhydrous ethanol, purified by centrifugation, and vacuum dried to obtain an intermediate product with a yield of 79%.

[0065] (2) The product of the previous step (10 mmol) was dissolved in dichloromethane (100 ml), and the acid-binding agent triethylamine (40 mmol) was added and mixed evenly. After cooling to 0°C in an ice bath, a solution of acryloyl chloride (20 mmol, dilution ratio of 1 mmol: 1 ml, acryloyl chloride / dichloromethane) diluted with dichloromethane was added dropwise. The mixture was stirred at 0°C for 2 h and the reaction was completed after monitoring by TCL.

[0066] (3) adding an inorganic base to adjust the pH to 7-8 to quench the reaction; extracting with ethyl acetate, washing with saturated brine, drying with anhydrous sodium sulfate, and removing the solvent by distillation under reduced pressure. Column chromatography was performed using a mixture of petroleum ether and ethyl acetate as the mobile phase and 200-300 mesh silica gel as the stationary phase to obtain the final product CPBA-1 with a yield of 68%.

[0067] Example 2

[0068] A method for preparing a low migration polymerizable UV-LED photoinitiator comprises the following steps:

[0069] (1) 5-Hydroxymethylfurfural (20 mmol) and acetone (10 mmol) were dissolved in ethanol (40 ml), and 10 ml of sodium hydroxide aqueous solution (2.5 mmol / ml) was added dropwise to the reaction system. The mixture was stirred at room temperature for 4 h. A yellow precipitate appeared during the reaction. The precipitate was washed three times with anhydrous ethanol, purified by centrifugation, and vacuum dried to obtain an intermediate product with a yield of 76%.

[0070] (2) The product of the previous step (10 mmol) was dissolved in dichloromethane (100 ml), and the acid-binding agent triethylamine (40 mmol) was added and mixed evenly. After cooling to 0°C in an ice bath, a solution of acryloyl chloride (20 mmol, dilution ratio of 1 mmol: 1 ml, acryloyl chloride / dichloromethane) diluted with dichloromethane was added dropwise. The mixture was stirred at 0°C for 2 h and the reaction was completed after monitoring by TCL.

[0071] (3) adding an inorganic base to adjust the pH to 7-8 to quench the reaction; extracting with ethyl acetate, washing with saturated brine, drying with anhydrous sodium sulfate, and removing the solvent by distillation under reduced pressure. Column chromatography was performed using a mixture of petroleum ether and ethyl acetate as the mobile phase and 200-300 mesh silica gel as the stationary phase to obtain the final product CPBA-2 with a yield of 74.6%.

[0072] The synthesis route of the photoinitiator of this embodiment is as follows:

[0073]

[0074] Figure 1 This is the mass spectrum of the photoinitiator in Example 2.

[0075] Figure 2 This is the H NMR spectrum of the photoinitiator in Example 2.

[0076] Figure 3 This is the NMR carbon spectrum of the photoinitiator in Example 2.

[0077] Figure 4 This is the UV-visible spectrum of the photoinitiator in Example 2.

[0078] from Figure 1 It can be seen that the molecular weight of the initiator in Example 2 meets the expected design; Figure 2 It can be seen that the hydrogen spectrum of the initiator molecule of Example 2 is consistent with the number of hydrogen in different environments and the molecular structure; Figure 3 It can be seen that the carbon spectrum of the initiator molecule of Example 2 is consistent with the number of carbons in different environments and the molecular structure; Figure 4 It can be seen that the UV-LED effective absorption of the photoinitiator in Example 2 is between 300-425 nm.

[0079] Example 3

[0080] A method for preparing a low migration polymerizable UV-LED photoinitiator comprises the following steps:

[0081] (1) 5-Methylsalicylaldehyde (20 mmol) and acetone (10 mmol) were dissolved in ethanol (40 ml), and 10 ml of sodium hydroxide aqueous solution (2.5 mmol / ml) was added dropwise to the reaction system. The mixture was stirred at room temperature for 4 h. A yellow precipitate appeared during the reaction. The precipitate was washed three times with anhydrous ethanol, purified by centrifugation, and vacuum dried to obtain an intermediate product 81%.

[0082] (2) The product of the previous step (10 mmol) was dissolved in dichloromethane (100 ml), and the acid-binding agent triethylamine (40 mmol) was added and mixed evenly. After cooling to 0°C in an ice bath, a solution of acryloyl chloride (20 mmol, dilution ratio of 1 mmol: 1 ml, acryloyl chloride / dichloromethane) diluted with dichloromethane was added dropwise. The mixture was stirred at 0°C for 2 h and the reaction was completed after monitoring by TCL.

[0083] (3) adding an inorganic base to adjust the pH to 7-8 to quench the reaction; extracting with ethyl acetate, washing with saturated brine, drying with anhydrous sodium sulfate, and removing the solvent by distillation under reduced pressure. Column chromatography was performed using a mixture of petroleum ether and ethyl acetate as the mobile phase and 200-300 mesh silica gel as the stationary phase to obtain the final product CPBA-3, with a final yield of 64.56%.

[0084] Example 4

[0085] (1) Migration test

[0086] The synthesized CPBAs series photoinitiator (1%), co-initiator (2wt% TEOA, 2wt% Iod) and TMPTA monomer (95%) were mixed and stirred evenly according to the mass ratio, and the coating was prepared and cured after standing. The cured coating was crushed and placed in 10ml acetonitrile solvent, and soaked in the dark at room temperature for 48h. After filtering and washing, the solution was diluted to 50ml, and the absorbance of the maximum absorption peak of the photoinitiator was measured with a UV-visible spectrophotometer. The mobility of the photoinitiator was quantitatively calculated according to the Lambert-Beer law (Table 1), and the formula is as follows:

[0087] Migration ratio = (A × M × V solution ) / (ε×b×m0)

[0088] Where A is the absorbance, M is the relative atomic mass of the photoinitiator, V solution is the total volume of the solution, ε is the molar absorption coefficient of the photoinitiator in the solution, b is the optical path length, and m0 is the mass of the photoinitiator added to the cured film.

[0089] Table 1 Photoinitiator mobility

[0090] Photoinitiator Mobility Competitor ITX 14.6％ Example 1 1.24％ Example 2 0.24％ Example 3 1.73％

[0091] It can be seen from Table 1 that the mobility of the photoinitiators in the embodiments of the present invention is lower than that of the competing product ITX. There are three reasons for this:

[0092] 1) The present invention introduces a -C=C- double bond into the molecule, providing multiple sites for the initiator to participate in photopolymerization, so that the initiator partially participates in the double bond polymerization reaction, and the reaction is cured in the paint film, thereby reducing the migration of the initiator;

[0093] 2) The molecular weight of the photoinitiator of the present invention is greater than that of ITX, and the chance of the molecules diffusing and precipitating from the coating is reduced, thereby reducing the mobility of the initiator;

[0094] 3) Influence of molecular structure and groups. For example, the molecular weight of the photoinitiators in Examples 1 and 2 is relatively smaller than that in Example 3, but the mobility is lower than that in Example 3.

[0095] (2) Double bond conversion rate

[0096] A real-time infrared spectrometer was used to detect the photopolymerization performance of the synthesized photoinitiator in situ. The signal measured by the infrared was an absorption signal. The test time was 300s, and the real-time infrared spectrum recording range was 4000-600cm-1. The light source for photopolymerization was an LED light source with an emission wavelength of 365nm (light intensity of 100mW / cm2). A uniform mixture of different formulations of the CPBAs series was prepared, and the mixture was evenly coated on a polyvinyl chloride (PVC) film, and then covered with a layer of PVC film to prevent oxygen inhibition during the test. The changes in the sample with increasing illumination time were measured by infrared spectroscopy, and the changes in the stretching vibration of the double bond at 810cm-1 were determined, and the C=O bond at 1720cm-1 was used as the standard. The calculation method of the carbon-carbon double bond conversion rate (Table 2) is as follows:

[0097] DC(%)=[1-(A 810 / A 1720 ) t / (A 810 / A 1720 )0]×100%

[0098] Where (A 810 / A 1720 )0 and (A 810 / A 1720 ) t They are the peak area ratios of C=C and C=O bonds before curing and at curing time t, respectively.

[0099] Table 2 shows the C=C conversion rate of the photoinitiator and the competitive product ITX in Examples 1-3

[0100] Photoinitiator C=C conversion rate Competitor ITX 54.7％ Example 1 52.3％ Example 2 51.89％ Example 3 52.98％

[0101] Figure 5 Graph showing the C=C conversion rates of the photoinitiators in Examples 1-3 and the competitor ITX.

[0102] From Table 2 and Figure 5 It can be seen that when the amount of photoinitiator added in the embodiment of the present invention is 1wt%, the C=C conversion rate of the initiated monomer polymerization is close to that of the commercially available product ITX, and the photoinitiation efficiency is relatively high. The raw materials used in the product of the present invention are widely available, cheap, and simple to synthesize. The use of the photoinitiator of the present invention can reduce the cost of the formulation materials.

[0103] The above embodiments are only preferred implementation modes of the present invention and are only used to explain the present invention rather than to limit the present invention. Any changes, substitutions, modifications, etc. made by those skilled in the art without departing from the spirit of the present invention should fall within the scope of protection of the present invention.

Claims

1. A low migration polymerizable UV-LED photoinitiator, characterized in that: The structural formula is as follows: 。 2. The method for preparing the low migration polymerizable UV-LED photoinitiator according to claim 1, characterized in that: The following steps are involved: (1) dissolving a hydroxyl-containing aldehyde derivative and a ketone derivative in a solvent, dropping an alkaline catalyst solution, stirring the reaction to generate a precipitate, and then separating and purifying the precipitate to obtain an intermediate product; The structural formula of the hydroxyl-containing aldehyde derivative is as follows: The structural formula of the ketone derivative is as follows: (2) dissolving the intermediate product in an organic solvent, adding an acid-binding agent and mixing evenly, dropping an organic solution of an olefin chloride compound into the mixed solution, stirring the reaction, and monitoring the reaction by TLC until the reaction is complete; quenching the reaction, extracting and separating, and purifying to obtain a low migration polymerizable UV-LED photoinitiator; The structural formula of the olefinic acid chloride compound is as follows: 。 3. The method for preparing the low migration polymerizable UV-LED photoinitiator according to claim 2, characterized in that: In step (1), the molar ratio of the hydroxyl-containing aldehyde derivative to the ketone derivative is 2-3:1, the molar ratio of the alkaline catalyst to the ketone derivative is 1-3:1, and the molar volume ratio of the hydroxyl-containing aldehyde derivative to the solvent is 1 mmol:1-3 ml; The solvent in step (1) includes one or more of ethanol, water, and methanol; the stirring reaction time is 4 hours to 8 hours; the stirring reaction temperature is room temperature; and the alkaline catalyst includes one or more of sodium hydroxide and potassium hydroxide.

4. The method for preparing a low migration polymerizable UV-LED photoinitiator according to claim 2, characterized in that: In step (2), the molar ratio of the intermediate product to the olefin chloride compound is 1:2-3; the molar ratio of the olefin chloride compound to the acid binding agent is 1:1-2; and the molar volume ratio of the intermediate product to the organic solvent is 1 mmol:5-20 ml.

5. The method for preparing the low migration polymerizable UV-LED photoinitiator according to claim 2, characterized in that: The temperature for dropwise addition of the olefin chloride compound in step (2) is 0°C-10°C; the temperature for stirring the reaction in step (2) is 0°C-6°C; the time for stirring the reaction in step (2) is 1h-3h; In step (2), the organic solvent is one or both of dichloromethane and tetrahydrofuran, and the acid binding agent is one or both of triethylamine and pyridine.

6. The method for preparing the low migration polymerizable UV-LED photoinitiator according to claim 2, characterized in that: The separation and purification in step (1) is washing with anhydrous ethanol, centrifuging, and drying to obtain an intermediate product; The quenching reaction in step (2) is to add an inorganic base to adjust the pH to 7-8; The extraction separation in step (2) is performed by adding ethyl acetate for extraction separation; The purification in step (2) is washing with saturated brine, drying with anhydrous sodium sulfate, removing the solvent by distillation under reduced pressure, and performing column chromatography with a mixture of petroleum ether and ethyl acetate as the mobile phase and 200-300 mesh silica gel as the stationary phase to obtain the final product.

7. The method for preparing the low migration polymerizable UV-LED photoinitiator according to claim 6, characterized in that: The number of times of washing with anhydrous ethanol in step (1) is ≥ 3 times; the drying in step (1) is vacuum drying, and the drying temperature is 40-60°C; The anhydrous sodium sulfate drying in step (2) is to add anhydrous sodium sulfate to ethyl acetate containing the final product, mix and stir evenly, observe that the sodium sulfate is a flowing powder, and then let it stand for 0.5-1h; The volume ratio of the mixture of petroleum ether and ethyl acetate in step (2) is 1-3:

1.

8. Use of the low migration polymerizable UV-LED photoinitiator according to claim 1 in photocuring.

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