Photoinitiator as well as preparation method and application thereof

Abstract

The invention relates to a photoinitiator as well as a preparation method and application thereof, the photoinitiator comprises 2, 4, 6-trimethylbenzoyl phenyl methyl phosphonate, and the melting point of the photoinitiator is 53-57 DEG C. The photoinitiator disclosed by the invention has the characteristics of light appearance color, low yellowness value, small odor, good fluidity and high storage stability, has good solubility in a monomer and can also play a role of a dispersing agent, and a formed photocuring system is high in curing rate, high in adhesive force on the surfaces of different plastic base materials and excellent in comprehensive performance.

Description

Technical Field

[0001] The present invention relates to the technical field of photoinitiators, and in particular to a photoinitiator, a preparation method thereof and an application thereof. Background Art

[0002] A photoinitiator, also known as a photosensitizer or a photocuring agent, is a kind of compound that can absorb energy of a certain wavelength in the ultraviolet region (250-420 nm) or the visible light region (400-800 nm), generate free radicals, cations, etc., thereby initiating the polymerization and crosslinking curing of monomers.

[0003] Photoinitiators are classified into two major categories: free radical polymerization photoinitiators and cationic polymerization photoinitiators according to the photolysis mechanism, and free radical photoinitiators are the most widely used. Free radical photoinitiators can be divided into cleavage type photoinitiators and hydrogen abstraction type photoinitiators according to the mechanism of generating free radicals. An ideal photoinitiator should have the following advantages: (1) inexpensive and simple to synthesize; (2) the photoinitiator and its photolysis products should be non-toxic and odorless; (3) good stability for long-term storage; (4) the absorption spectrum of the photoinitiator must match the emission band of the radiation source and have a high molar extinction coefficient; (5) high initiation efficiency.

[0004] However, due to the problem of reproductive toxicity, currently mature photoinitiators such as photoinitiator 907, photoinitiator 369 and photoinitiator 379 are further controlled by the EU REACH regulation, resulting in a further reduction in the types of photoinitiators with excellent comprehensive performance. Therefore, it is crucial to develop a photoinitiator with excellent comprehensive performance. Summary of the Invention

[0005] Aiming at the deficiencies of the prior art, the purpose of the present invention is to provide a photoinitiator, a preparation method thereof and an application thereof. The photoinitiator has the characteristics of light appearance color, low yellowness value, small odor, good fluidity and high storage stability, and has good solubility in monomers, can also play the role of a dispersant, the formed photocuring system has a fast curing rate and high adhesion on the surfaces of different plastic substrates, and has excellent comprehensive performance.

[0006] To achieve this purpose, the present invention adopts the following technical solutions:

[0007] In the first aspect, the present invention provides a photoinitiator, which comprises methyl 2,4,6-trimethylbenzoyl phenylphosphonate;

[0008] The melting point of the photoinitiator is 53-57 °C, such as 53.5 °C, 54 °C, 54.5 °C, 55 °C, 55.5 °C, 56 °C, 56.5 °C, etc.

[0009] In the present invention, the photoinitiator has the characteristics of light appearance color, low yellowness value, small odor, good fluidity and high stability, good solubility in monomers, fast curing rate of the formed photocuring system, high adhesion on the surfaces of different plastic substrates, and excellent comprehensive performance.

[0010] In addition, based on its excellent self-photoinitiating performance, the photoinitiator of the present invention also has the function of a dispersant. In the photocuring composition, the photoinitiator of the present invention can reduce the usage amount of the dispersant, save costs, and reduce the adverse effects of excessive additives on the system.

[0011] Preferably, the morphology of the photoinitiator includes any one or a combination of at least two of cross-shaped, spherical, quasi-spherical or flaky. Among them, typical but non-limiting combinations include: the combination of cross-shaped and spherical, the combination of spherical, quasi-spherical and flaky, the combination of cross-shaped, spherical, quasi-spherical and flaky, etc. Further preferably, it is cross-shaped.

[0012] Preferably, the cross-shaped includes through-cross or non-through-cross.

[0013] Preferably, the cross-shaped is formed by at least two regular and / or irregular columns crossing each other.

[0014] In the present invention, typical but non-limiting examples of the column include cuboid, cube, prism, cylinder, quasi-cylinder, etc.

[0015] In the present invention, the morphology of the photoinitiator is preferably the above-mentioned morphology. The photoinitiator with such a morphology has good stability, better compatibility with other components in the photocuring composition, can better play the role of a dispersant, the formed photocuring composition has a fast curing rate, high adhesion on the surfaces of different plastic substrates, and excellent comprehensive performance.

[0016] Preferably, the particle size distribution of the photoinitiator is: D50 is 40 - 80 μm (such as 42 μm, 45 μm, 52 μm, 54 μm, 56 μm, 58 μm, 60 μm, 62 μm, 64 μm, 66 μm, 68 μm, 70 μm, 72 μm, 75 μm, 78 μm, etc.).

[0017] In the present invention, D50 refers to: based on the total volume of the particles being 100%, on the cumulative degree distribution curve of the particle size, the particle size corresponding to the point with a volume of 50%. The testing method used includes laser diffraction scattering method; D99 is the same by analogy.

[0018] In the present invention, the reason for controlling the particle size distribution of the photoinitiator within a preferred range is as follows: the interaction forces between the photoinitiator particles within this range reach a good balance, enabling the properties of the photoinitiator itself to be in the best state. When applied to the photocurable composition, it can better play the role of a dispersant, has a strong compatibility with other components, and exhibits excellent comprehensive properties. If the particle size is too small, it is prone to generating dust and static electricity, requires high equipment requirements, is inconvenient to use, and the specific surface area of the particle size product increases, resulting in reduced storage stability, shortened storage period, and decreased effective utilization rate of raw materials. If the particle size is too large, it has poor fluidity and poor solubility in monomers, making it difficult to play the role of a dispersant well, resulting in a slow curing rate of the formed photocurable system and poor adhesion on the surfaces of different plastic substrates.

[0019] In the present invention, the morphology and particle size distribution of the photoinitiator cooperate with each other, further enhancing the comprehensive performance of the photoinitiator.

[0020] Preferably, D99 of the photoinitiator ≤ 150 μm, such as 145 μm, 140 μm, 135 μm, 130 μm, 120 μm, 115 μm, etc.

[0021] Preferably, the molar extinction coefficient of the photoinitiator is 200 - 2500 L·mol -1 ·cm -1 For example, 400 L·mol -1 ·cm -1 、600 L·mol -1 ·cm -1 、800 L·mol -1 ·cm -1 、1000 L·mol -1 ·cm -1 、1200 L·mol -1 ·cm -1 、1400 L·mol -1 ·cm -1 、1600 L·mol -1 ·cm -1 、2000 L·mol -1 ·cm -1 、2200 L·mol -1 ·cm -1 、2400 L·mol -1 ·cm -1 etc.

[0022] In the present invention, the test method for the molar extinction coefficient is as follows: Dissolve the photoinitiator in a solvent (including but not limited to methylcyclohexane) to prepare a solution with a concentration of 1 mol / L. Place the solution in a cuvette and use an ultraviolet spectrophotometer to measure the ultraviolet absorbance of the solution between 200 nm and 500 nm (such as 250 nm, 270 nm, 290 nm, 370 nm, etc.). Use Formula 1 to calculate the molar extinction coefficient at different wavelengths:

[0023] A = ε·l·c Formula 1

[0024] Wherein, A is the absorbance; ε is the molar extinction coefficient, with the unit of L·mol -1 ·cm -1 ; l is the optical path length, which is taken as 1 cm here; c is the concentration, which is taken as 1 mol / L here.

[0025] Exemplarily, when the wavelength is 270 nm, the molar extinction coefficient of the photoinitiator is 2380 - 2440 L·mol -1 ·cm -1 , such as 2385 L·mol -1 ·cm -1 , 2391 L·mol -1 ·cm -1 , 2395 L·mol -1 ·cm -1 , 2400 L·mol -1 ·cm -1 , 2410 L·mol -1 ·cm -1 , 2420 L·mol -1 ·cm -1 , 2430 L·mol -1 ·cm -1 etc.

[0026] Exemplarily, when the wavelength is 290 nm, the molar extinction coefficient of the photoinitiator is 2160 - 2210 L·mol -1 ·cm -1 , such as 2165 L·mol -1 ·cm -1 , 2170 L·mol -1 ·cm -1 , 2180 L·mol -1 ·cm -1 , 2190 L·mol -1 ·cm -1 , 2200 L·mol -1 ·cm -1 etc.

[0027] Exemplarily, when the wavelength is 370 nm, the molar extinction coefficient of the photoinitiator is 285 - 295 L·mol -1 ·cm -1 , such as 286 L·mol -1 ·cm -1 , 287 L·mol -1 ·cm -1 , 288 L·mol -1 ·cm -1 , 289 L·mol -1 ·cm -1 , 291 L·mol -1 ·cm -1 , 292 L·mol -1 ·cm -1 , 293 L·mol -1 ·cm -1 , 294 L·mol -1 ·cm -1 and so on.

[0028] In the present invention, the reason for controlling the molar extinction coefficient of the photoinitiator within the above range is that the photoinitiator within this range has the characteristics of light appearance color, low yellowness value, small odor, good fluidity, and high storage stability, and has good solubility in monomers. Further, the formed photocurable composition has a fast curing rate and high adhesion on the surfaces of different plastic substrates, and excellent comprehensive properties.

[0029] In a second aspect, the present invention provides a preparation method of the photoinitiator according to the first aspect, and the preparation method includes the following steps:

[0030] Mix dimethylphenylphosphonate and 2,4,6-trimethylbenzoyl chloride, react and perform melt crystallization to obtain the photoinitiator.

[0031] Preferably, the temperature of the reaction is 40 - 60 °C, such as 42 °C, 44 °C, 46 °C, 48 °C, 50 °C, 52 °C, 54 °C, 56 °C, 58 °C, etc.

[0032] Preferably, the reaction time is 1 - 3 h, such as 1.2 h, 1.4 h, 1.6 h, 1.8 h, 2 h, 2.2 h, 2.4 h, 2.6 h, 2.8 h, etc.

[0033] Preferably, the melt crystallization process includes melting, crystallization, sweating, and remelting.

[0034] Preferably, the melting includes operations of heating and heat preservation.

[0035] Preferably, the heating is to 60 - 65 °C, such as 61 °C, 62 °C, 63 °C, 64 °C, etc.

[0036] Preferably, the heat preservation time is 30 - 60 min, such as 35 min, 40 min, 45 min, 50 min, 55 min, etc.

[0037] Preferably, the crystallization is carried out in a crystallization device, and its structural schematic diagram is as Figure 7 shown. The crystallization device includes a crystallization tank 2, an outer jacket 3 arranged on the outer surface of the crystallization tank, and an inner jacket 1 arranged inside the crystallization tank; the crystallization device also includes a liquid outlet 4.

[0038] In the present invention, the liquid outlet is used to discharge the reaction liquid, product or by - product in the reaction as needed, and the number of the liquid outlets is set as needed, such as 1 - 3.

[0039] In the present invention, the crystallization device also includes auxiliary units such as a temperature control system, which is not shown in the schematic diagram and is set as needed.

[0040] Preferably, during the crystallization, the reaction liquid is placed in the crystallization tank, the temperature of the outer jacket is controlled, and the temperature of the inner jacket is adjusted for the first time to carry out crystallization.

[0041] Preferably, the temperature of the outer jacket is controlled to 40 - 60 °C, such as 45 °C, 50 °C, 55 °C, etc.

[0042] Preferably, the temperature of the inner jacket is adjusted for the first time to 10 - 45 °C, such as 15 °C, 20 °C, 25 °C, 30 °C, 35 °C, 40 °C, etc., and more preferably 35 - 45 °C.

[0043] In the present invention, controlling the temperature of the inner jacket adjusted for the first time within the preferred range is conducive to forming a photo - initiator with a particle size within the preferred range and a cross - shaped morphology.

[0044] Preferably, the time taken for the first adjustment of the temperature of the inner jacket to the above temperature is 30 - 120 min, such as 40 min, 60 min, 80 min, 100 min, etc.

[0045] Preferably, after the first adjustment of the temperature of the inner jacket to the above temperature, it is maintained for 30 - 240 min, such as 40 min, 60 min, 80 min, 100 min, 120 min, 140 min, 160 min, 180 min, 200 min, 220 min, etc.

[0046] Preferably, the sweating includes discharging the reaction liquid after crystallization, adjusting the temperature of the inner jacket for the second time, and reducing the pressure.

[0047] Preferably, the temperature of the second adjustment of the inner jacket is adjusted to 10 - 50 °C, such as 15 °C, 20 °C, 25 °C, 30 °C, 35 °C, 40 °C, 45 °C, etc., and more preferably 37 - 50 °C.

[0048] In the present invention, controlling the temperature of the second adjustment of the inner jacket within the preferred range is beneficial to form a photoinitiator with a particle size within the preferred range and a cross-shaped morphology.

[0049] Preferably, the time taken for the second adjustment of the inner jacket to the temperature is 30 - 240 min, such as 40 min, 60 min, 80 min, 100 min, 120 min, 140 min, 160 min, 180 min, 200 min, 220 min, etc.

[0050] Preferably, after the second adjustment of the inner jacket to the temperature, it is maintained for 30 - 240 min, such as 40 min, 60 min, 80 min, 100 min, 120 min, 140 min, 160 min, 180 min, 200 min, 220 min, etc.

[0051] Preferably, the pressure is reduced to 0.01 - 0.1 MPa, such as 0.02 MPa, 0.04 MPa, 0.06 MPa, 0.08 MPa, etc.

[0052] Preferably, after the pressure is reduced to 0.01 - 0.1 MPa (such as 0.02 MPa, 0.04 MPa, 0.06 MPa, 0.08 MPa, etc.), it is maintained for 30 - 240 min, such as 40 min, 60 min, 80 min, 100 min, 120 min, 140 min, 160 min, 180 min, 200 min, 220 min, etc.

[0053] Preferably, after sweating, the crystals on the surface of the inner jacket are collected and melted.

[0054] Preferably, the melting temperature is 60 - 65 °C, such as 61 °C, 62 °C, 63 °C, 64 °C, etc.

[0055] Preferably, after the melt crystallization, it further includes solvent treatment and drying.

[0056] Preferably, the solvent treatment includes dissolving the material in a good solvent and then precipitating it in a poor solvent.

[0057] In the present invention, the good solvent refers to a solvent that has good solubility in the material after melt crystallization. The determination criterion in the present invention is that at 30 °C, the material and the good solvent are mixed at a mass ratio of 1:2, and can be completely dissolved within half an hour; the poor solvent refers to a solvent that has poor solubility in the material after melt crystallization. The determination criterion in the present invention is that at 30 °C, the material and the good solvent are mixed at a mass ratio of 1:10, and cannot be completely dissolved within half an hour.

[0058] Preferably, based on the mass of the material after melt crystallization being 100%, the mass of the good solvent is 25%-45%, such as 25%, 30%, 35%, 40%, 45%, etc.

[0059] In the present invention, based on the mass of the material after melt crystallization being 100%, controlling the mass of the good solvent within the preferred range is beneficial to forming a photoinitiator with a particle size within the preferred range and a cross-shaped morphology.

[0060] Preferably, the mass ratio of the good solvent to the poor solvent is 1:(1-10), where 1-10 can be 2, 4, 6, 8, etc., and further preferably 1:(1-5).

[0061] In the present invention, controlling the mass ratio of the good solvent to the poor solvent within the preferred range is beneficial to forming a photoinitiator with a particle size within the preferred range and a cross-shaped morphology.

[0062] Preferably, the good solvent includes any one or a combination of at least two of toluene, methanol, ethyl acetate, butyl acetate, isopropyl acetate or n-propyl acetate. Among them, typical but non-limiting combinations include: a combination of toluene and methanol, a combination of ethyl acetate, butyl acetate and isopropyl acetate, a combination of butyl acetate, isopropyl acetate and n-propyl acetate, etc.

[0063] Preferably, the poor solvent includes any one or a combination of at least two of water, petroleum ether, methylcyclohexane, n-heptane or n-hexane. Among them, typical but non-limiting combinations include: a combination of water and petroleum ether, a combination of petroleum ether, n-heptane and n-hexane, a combination of methylcyclohexane, water, petroleum ether, n-heptane and n-hexane, etc.

[0064] As a preferred technical solution, the preparation method includes the following steps:

[0065] (1) Mix dimethyl phenylphosphonate and 2,4,6-trimethylbenzoyl chloride, and react at 40-60 °C for 1-3 h;

[0066] (2) Subject the material obtained in step (1) to melt crystallization; the melt crystallization specifically includes the following process:

[0067] 1) Melting: Heat the material obtained in step (1) to 60 - 65°C and keep it warm for 30 - 60 min;

[0068] 2) Crystallization: Place the material obtained in step 1) in a crystallization device, which includes a crystallization tank, an outer jacket arranged on the outer surface of the crystallization tank, and an inner jacket arranged inside the crystallization tank;

[0069] During the crystallization, place the reaction solution in the crystallization tank, control the temperature of the outer jacket to 40 - 60°C, adjust the temperature of the inner jacket to 10 - 45°C within 30 - 120 min, and maintain for 30 - 240 min;

[0070] 3) Sweating: Drain the reaction solution after crystallization, adjust the temperature of the inner jacket to 10 - 45°C within 30 - 240 min, reduce the pressure to 0.01 - 0.1 MPa, and maintain for 30 - 240 min;

[0071] 4) Collect the crystals on the surface of the inner jacket and melt them at 60 - 65°C;

[0072] (3) Dissolve the material obtained in step (2) in a good solvent, then precipitate it in a poor solvent, and dry it after the solvation treatment. Among them, based on the mass of the material after melt crystallization being 100%, the mass of the good solvent is 25% - 45%, and control the mass ratio of the good solvent to the poor solvent to be 1:(1 - 10) to obtain the photoinitiator.

[0073] In a third aspect, the present invention provides a photocurable composition, which includes a resin, a monomer, and the photoinitiator described in the first aspect.

[0074] Compared with the prior art, the present invention has the following beneficial effects:

[0075] (1) The photoinitiator described in the present invention has the characteristics of light appearance color, low yellowness value, small odor, good fluidity, and high storage stability, and has good solubility in monomers. The formed photocurable system has a fast curing rate, high adhesion on the surfaces of different plastic substrates, and excellent comprehensive performance;

[0076] The photoinitiator described in the present invention can act as a dispersant. In the photocurable composition, the amount of the dispersant can be reduced without affecting the relevant performance.

[0077] (2) The appearance color of the photoinitiator described in the present invention is white, the yellowness value is between 1.62 - 1.80, the odor grade is B level, the fluidity is between 38.3° - 44.8°, the storage stability grade is between 9 - 10, and the curing energy is between 66.9 - 77.8 mj·cm 2Between them, the solubility in the monomer is between 50% and 65%, and the adhesion on the surfaces of different plastic substrates is between Grade 1 and Grade 2. Description of the Drawings

[0078] Figure 1 is the enlarged morphology diagram of the photoinitiator described in Example 1;

[0079] Figure 2 is the morphology diagram of the photoinitiator described in Example 1;

[0080] Figure 3 is the enlarged morphology diagram of the photoinitiator described in Example 7;

[0081] Figure 4 is the morphology diagram of the photoinitiator described in Example 7;

[0082] Figure 5 is the enlarged morphology diagram of the photoinitiator described in Example 8;

[0083] Figure 6 is the standard judgment diagram for adhesion test;

[0084] Figure 7 is the structural schematic diagram of the crystallization device described in the present invention;

[0085] Among them, 1 - inner jacket; 2 - crystallization tank; 3 - outer jacket; 4 - liquid outlet. Detailed Embodiments

[0086] To facilitate the understanding of the present invention, the following examples are listed. Those skilled in the art should understand that the said examples are only for helping to understand the present invention and should not be regarded as specific limitations to the present invention.

[0087] Example 1

[0088] This example provides a white solid photoinitiator, and the photoinitiator is methyl 2,4,6 - trimethylbenzoyl phenylphosphonate; the melting point of the photoinitiator is 55°C - 57°C.

[0089] The morphology of the photoinitiator is cross - shaped, and its enlarged morphology diagram and morphology diagram are respectively as Figure 1 and Figure 2 shown.

[0090] The particle size distribution of the photoinitiator is: D50 is 61μm, and D99 is 124μm.

[0091] The molar extinction coefficient of the photoinitiator is 2420 L·mol -1 ·cm -1 (270 nm).

[0092] The preparation method of the photoinitiator is obtained by the following preparation method, and the preparation method includes the following steps:

[0093] (1) Mix 170 g of dimethyl phenylphosphonate and 182 g of 2,4,6-trimethylbenzoyl chloride, and react at 50 °C for 3 h;

[0094] (2) Subject the material obtained in step (1) to melt crystallization. The process of melt crystallization is as follows:

[0095] 1) Melting: Heat the material obtained in step (1) to 62 °C and keep it warm for 50 min;

[0096] 2) Crystallization: Place the material obtained in step 1) in a crystallization device. The crystallization device includes a crystallization tank, an outer jacket provided on the outer surface of the crystallization tank, and an inner jacket provided inside the crystallization tank;

[0097] During the crystallization, place the reaction solution in the crystallization tank. Control the temperature of the outer jacket to 45 °C within 60 min, and adjust the temperature of the inner jacket to 40 °C in 60 min, and keep it for 120 min;

[0098] 3) Sweating: Drain the reaction solution after crystallization, adjust the temperature of the inner jacket to 45 °C in 60 min, reduce the pressure to 0.04 MPa, and keep it for 60 min; Drain the sweat;

[0099] 4) Collect the crystals on the surface of the inner jacket, melt them at 60 °C, and collect;

[0100] (3) Dissolve the material obtained in step (2) in ethyl acetate, then add petroleum ether to precipitate it. After completing the solvation treatment, dry it. Among them, control the mass ratio of the material obtained in step (2) to ethyl acetate to be 1:0.3, and the mass ratio of ethyl acetate to petroleum ether to be 1:3 to obtain the photoinitiator.

[0101] Example 2

[0102] This example provides a white solid photoinitiator, and the photoinitiator is methyl 2,4,6-trimethylbenzoyl phenylphosphonate; the melting point of the photoinitiator is 53 - 56 °C.

[0103] The morphology of the photoinitiator includes a cross shape.

[0104] The particle size distribution of the photoinitiator is: D50 is 42 μm, and D99 is 104 μm.

[0105] The molar extinction coefficient of the photoinitiator is 2423 L·mol -1 ·cm -1 (270 nm).

[0106] The preparation method of the photoinitiator is obtained by the following preparation method, and the preparation method includes the following steps:

[0107] (1) Mix 170 g of dimethyl phenylphosphonate and 182 g of 2,4,6-trimethylbenzoyl chloride, and react at 50 °C for 4 h;

[0108] (2) Perform melt crystallization on the material obtained in step (1). The process of melt crystallization is as follows:

[0109] 1) Melting: Heat the material obtained in step (1) to 60 °C and keep it warm for 60 min;

[0110] 2) Crystallization: Place the material obtained in step 1) in a crystallization device. The crystallization device includes a crystallization tank, an outer jacket arranged on the outer surface of the crystallization tank, and an inner jacket arranged inside the crystallization tank;

[0111] During the crystallization, place the reaction solution in the crystallization tank. Control the temperature of the outer jacket to 45 °C within 60 min, and adjust the temperature of the inner jacket to 35 °C in 120 min and keep it for 180 min;

[0112] 3) Sweating: Drain the reaction solution after crystallization, adjust the temperature of the inner jacket to 37 °C in 60 min, reduce the pressure to 0.06 MPa, and keep it for 180 min; Drain the sweat;

[0113] 4) Collect the crystals on the surface of the inner jacket, melt them at 65 °C, and collect them;

[0114] (3) Dissolve the material obtained in step (2) in ethyl acetate, then add petroleum ether to precipitate, and dry after the solventization treatment. Among them, control the mass ratio of the material obtained in step (2) to ethyl acetate to be 1:0.25, and the mass ratio of ethyl acetate to petroleum ether to be 1:2 to obtain the photoinitiator.

[0115] Example 3

[0116] This example provides a white solid photoinitiator, and the photoinitiator is methyl 2,4,6-trimethylbenzoyl phenylphosphonate; the melting point of the photoinitiator is 56 - 57 °C.

[0117] The morphology of the photoinitiator includes a cross shape.

[0118] The particle size distribution of the photoinitiator is: D50 is 79 μm, and D99 is 148 μm.

[0119] The molar extinction coefficient of the photoinitiator is 2419 L·mol -1 ·cm -1 (270 nm).

[0120] The preparation method of the photoinitiator is obtained by the following preparation method, and the preparation method includes the following steps:

[0121] (1) Mix 170 g of dimethyl phenylphosphonate and 182 g of 2,4,6-trimethylbenzoyl chloride, and react at 60 °C for 2 h;

[0122] (2) Perform melt crystallization on the material obtained in step (1), and the process of melt crystallization is as follows:

[0123] 1) Melting: Heat the material obtained in step (1) to 65 °C and keep it warm for 30 min;

[0124] 2) Crystallization: Place the material obtained in step 1) in a crystallization device, and the crystallization device includes a crystallization tank, an outer jacket provided on the outer surface of the crystallization tank, and an inner jacket provided inside the crystallization tank;

[0125] During the crystallization, the reaction solution is placed in the crystallization tank. Control the temperature of the outer jacket to 60 °C within 45 min, and adjust the temperature of the inner jacket to 45 °C in 45 min, and keep it for 90 min;

[0126] 3) Sweating: Drain the reaction solution after crystallization, adjust the temperature of the inner jacket to 50 °C in 60 min, reduce the pressure to 0.02 MPa, and keep it for 120 min; drain the sweat;

[0127] 4) Collect the crystals on the surface of the inner jacket, melt them at 62 °C, and collect them;

[0128] (3) Dissolve the material obtained in step (2) in ethyl acetate, then add petroleum ether to precipitate. After the solventization treatment, dry it. Among them, control the mass ratio of the material obtained in step (2) to ethyl acetate to be 1:0.45, and the mass ratio of ethyl acetate to petroleum ether to be 1:5 to obtain the photoinitiator.

[0129] Example 4

[0130] This example provides a white solid photoinitiator, which is different from Example 1 in particle size distribution: D50 is 35 μm, and D99 is 92 μm; the rest are the same as in Example 1.

[0131] The preparation method of the photoinitiator is obtained by the following preparation method, and the preparation method includes the following steps:

[0132] (1) Mix 170 g of dimethyl phenylphosphonate and 182 g of 2,4,6-trimethylbenzoyl chloride, and react at 50 °C for 3 h;

[0133] (2) Perform melt crystallization on the material obtained in step (1), and the process of melt crystallization is as follows:

[0134] 1) Melting: Heat the material obtained in step (1) to 62°C and keep it at this temperature for 50 min;

[0135] 2) Crystallization: Place the material obtained in step 1) in a crystallization device, which includes a crystallization tank, an outer jacket arranged on the outer surface of the crystallization tank, and an inner jacket arranged inside the crystallization tank;

[0136] During the crystallization, place the reaction solution in the crystallization tank, control the temperature of the outer jacket to 45°C within 60 min, and adjust the temperature of the inner jacket to 38°C within 60 min, and keep it for 120 min;

[0137] 3) Sweating: Drain the reaction solution after crystallization, adjust the temperature of the inner jacket to 40°C within 60 min, reduce the pressure to 0.04 MPa, and keep it for 60 min; Drain the sweat;

[0138] 4) Collect the crystals on the surface of the inner jacket, melt them at 60°C, and collect them;

[0139] (3) Dissolve the material obtained in step (2) in ethyl acetate, then add petroleum ether to precipitate it. After completing the solvation treatment, dry it. Among them, control the mass ratio of the material obtained in step (2) to ethyl acetate to be 1:0.2, and the mass ratio of ethyl acetate to petroleum ether to be 1:3 to obtain the photoinitiator.

[0140] Example 5

[0141] This example provides a white solid photoinitiator, which is different from Example 1 in terms of particle size distribution: D50 is 83 μm, and D99 is 149 μm; the rest are the same as in Example 1.

[0142] The preparation method of the photoinitiator is obtained by the following preparation method, and the preparation method includes the following steps:

[0143] (1) Mix 170 g of dimethyl phenylphosphonate and 182 g of 2,4,6-trimethylbenzoyl chloride, and react at 50°C for 3 h;

[0144] (2) Perform melt crystallization on the material obtained in step (1), and the process of melt crystallization is as follows:

[0145] 1) Melting: Heat the material obtained in step (1) to 62°C and keep it at this temperature for 50 min;

[0146] 2) Crystallization: Place the material obtained in step 1) in a crystallization device, which includes a crystallization tank, an outer jacket arranged on the outer surface of the crystallization tank, and an inner jacket arranged inside the crystallization tank;

[0147] During crystallization, the reaction solution is placed in a crystallization tank. The temperature of the outer jacket is controlled to 45°C within 60 minutes, and the temperature of the inner jacket is adjusted to 41°C over 60 minutes and maintained for 120 minutes.

[0148] 3) Sweating: Drain the reaction solution after crystallization, adjust the temperature of the inner jacket to 44°C over 60 minutes, reduce the pressure to 0.04 MPa, and maintain for 60 minutes; drain the sweat.

[0149] 4) Collect the crystals on the surface of the inner jacket, melt them at 60°C, and collect.

[0150] (3) Dissolve the material obtained in step (2) in ethyl acetate, then add petroleum ether to precipitate. After completing the solvation treatment, dry it. Among them, the mass ratio of the material obtained in step (2) to ethyl acetate is controlled to be 1:0.5, and the mass ratio of ethyl acetate to petroleum ether is 1:3 to obtain the photoinitiator.

[0151] Example 6

[0152] This example provides a white solid photoinitiator, which is different from Example 1 in particle size distribution: D50 is 85 μm, D99 is 154 μm; the rest are the same as in Example 1; the rest are the same as in Example 1.

[0153] The preparation method of the photoinitiator is obtained by the following preparation method, and the preparation method includes the following steps:

[0154] (1) Mix 170 g of dimethyl phenylphosphonate and 182 g of 2,4,6-trimethylbenzoyl chloride and react at 50°C for 3 hours.

[0155] (2) Perform melt crystallization on the material obtained in step (1). The process of melt crystallization is as follows:

[0156] 1) Melting: Heat the material obtained in step (1) to 62°C and keep it warm for 50 minutes.

[0157] 2) Crystallization: Place the material obtained in step 1) in a crystallization device. The crystallization device includes a crystallization tank, an outer jacket provided on the outer surface of the crystallization tank, and an inner jacket provided inside the crystallization tank.

[0158] During crystallization, the reaction solution is placed in the crystallization tank. The temperature of the outer jacket is controlled to 45°C within 60 minutes, and the temperature of the inner jacket is adjusted to 42°C over 60 minutes and maintained for 120 minutes.

[0159] 3) Sweating: Drain the reaction solution after crystallization, adjust the temperature of the inner jacket to 45°C over 60 minutes, reduce the pressure to 0.04 MPa, and maintain for 60 minutes; drain the sweat.

[0160] 4) Collect the crystals on the surface of the inner jacket, melt them at 60 °C, and collect them.

[0161] (3) Dissolve the material obtained in step (2) in ethyl acetate, then add petroleum ether to precipitate it. After the solvation treatment is completed, dry it. Among them, control the mass ratio of the material obtained in step (2) to ethyl acetate to be 1:0.55, and the mass ratio of ethyl acetate to petroleum ether to be 1:3 to obtain the photoinitiator.

[0162] Example 7

[0163] This example provides a white solid photoinitiator, which is different from Example 1 in that its morphology is spherical-like. The enlarged morphology diagram and the morphology diagram are respectively as Figure 3 and Figure 4 shown; the particle size distribution of the photoinitiator is: D50 is 63 μm, D99 is 124 μm, and the molar extinction coefficient of the photoinitiator is 2429 L·mol -1 ·cm -1 (270 nm), and the rest are the same as in Example 1.

[0164] The preparation method of the photoinitiator is obtained by the following preparation method, and the preparation method includes the following steps:

[0165] (1) Mix 170 g of dimethylphenylphosphonate and 182 g of 2,4,6-trimethylbenzoyl chloride, and react at 50 °C for 3 h.

[0166] (2) Perform melt crystallization on the material obtained in step (1). The specific process of melt crystallization is as follows:

[0167] 1) Melting: Heat the material obtained in step (1) to 62 °C and keep it warm for 50 min.

[0168] 2) Crystallization: Place the material obtained in step 1) in a crystallization device. The crystallization device includes a crystallization tank, an outer jacket provided on the outer surface of the crystallization tank, and an inner jacket provided inside the crystallization tank.

[0169] During the crystallization, the reaction solution is placed in the crystallization tank. Control the temperature of the outer jacket to 45 °C within 60 min, and adjust the temperature of the inner jacket to 20 °C within 60 min and keep it for 200 min.

[0170] 3) Sweating: Drain the crystallized reaction solution, adjust the temperature of the inner jacket to 24 °C within 60 min, reduce the pressure to 0.04 MPa, and keep it for 60 min; drain the sweat.

[0171] 4) Collect the crystals on the surface of the inner jacket, melt them at 60 °C, and collect them.

[0172] (3) Dissolve the material obtained in step (2) in ethyl acetate, then add petroleum ether to precipitate it. After the solvation treatment is completed, dry it. Among them, control the mass ratio of the material obtained in step (2) to ethyl acetate to be 1:0.34, and the mass ratio of ethyl acetate to petroleum ether to be 1:9 to obtain the photoinitiator.

[0173] Example 8

[0174] This example provides a white solid photoinitiator, which is different from that in Example 1 in that its morphology is flaky, and the enlarged view of its morphology is as Figure 5 shown; the particle size distribution of the photoinitiator is: D50 is 60 μm, D99 is 122 μm, and the molar extinction coefficient of the photoinitiator is 2417 L·mol -1 ·cm -1 (270 nm), and the rest are the same as in Example 1.

[0175] The preparation method of the photoinitiator is obtained by the following preparation method, and the preparation method includes the following steps:

[0176] (1) Mix 170 g of dimethylphenylphosphonate and 182 g of 2,4,6-trimethylbenzoyl chloride, and react at 55 °C for 3 h;

[0177] (2) Perform melt crystallization on the material obtained in step (1), and the process of melt crystallization is as follows:

[0178] 1) Melting: Heat the material obtained in step (1) to 62 °C and keep it warm for 50 min;

[0179] 2) Crystallization: Place the material obtained in step 1) in a crystallization device, and the crystallization device includes a crystallization tank, an outer jacket arranged on the outer surface of the crystallization tank, and an inner jacket arranged inside the crystallization tank;

[0180] During the crystallization, place the reaction solution in the crystallization tank, control the temperature of the outer jacket to 45 °C within 60 min, and adjust the temperature of the inner jacket to 28 °C within 60 min, and keep it for 240 min;

[0181] 3) Sweating: Drain the reacted solution after crystallization, adjust the temperature of the inner jacket to 31 °C within 60 min, reduce the pressure to 0.04 MPa, and keep it for 60 min; drain the sweat;

[0182] 4) Collect the crystals on the surface of the inner jacket, melt them at 60 °C, and collect them;

[0183] (3) Dissolve the material obtained in step (2) in ethyl acetate, then add petroleum ether to precipitate it. After completing the solvation treatment, dry it. Among them, control the mass ratio of the material obtained in step (2) to ethyl acetate to be 1:0.28, and the mass ratio of ethyl acetate to petroleum ether to be 1:7 to obtain the photoinitiator.

[0184] Example 9

[0185] This example provides a photoinitiator, which is different from that in Example 1 in that its morphology is oily, and the rest are the same as those in Example 1.

[0186] The preparation method of the photoinitiator is obtained by the following preparation method, and the preparation method includes the following steps:

[0187] Mix 170 g of dimethyl phenylphosphonate and 182 g of 2,4,6-trimethylbenzoyl chloride, react at 50 °C for 3 h, dissolve the obtained material in ethyl acetate, then add petroleum ether to precipitate it. After completing the solvation treatment, dry it. Control the mass ratio of the obtained material to ethyl acetate to be 1:0.3, and the mass ratio of ethyl acetate to petroleum ether to be 1:3. Heat the obtained solid to melt it into a liquid, and then let it stand for 48 h and it is still a liquid to obtain the photoinitiator.

[0188] Comparative Example 1

[0189] This comparative example provides a photoinitiator: ethyl 2,4,6-trimethylbenzoyl phenylphosphonate.

[0190] Comparative Example 2

[0191] This comparative example provides a photoinitiator, and the photoinitiator is methyl 2,4,6-trimethylbenzoyl phenylphosphonate, and its melting point is 50 - 52 °C, and it is a yellow solid (reference: Example 4 of US 4298738A).

[0192] Comparative Example 3

[0193] This comparative example provides a photoinitiator TPO: diphenyl-(2,4,6-trimethylbenzoyl)phosphine oxide.

[0194] Performance test

[0195] Perform the following tests on the photoinitiators described in Examples 1 - 9 and Comparative Examples 1 - 3:

[0196] (1) Appearance: Observe its color by visual inspection; test its morphology by an electron microscope with a magnification of 200 - 400, the magnification of the enlarged morphology diagram is 380 - 400, and the magnification of the schematic diagram of the morphology diagram is 200 - 220.

[0197] (2) Yellowing resistance:

[0198] ① Weigh the metered photoinitiator, resin, and monomer according to the ratio in Table 1, and use ultrasonic stirring to mix them evenly. Based on the total mass of the mixed coating being 100%, the mass ratio of the photoinitiator is 5%. Coat the mixed coating on a glass slide with a film applicator with a thickness of 10 μm, and place it under a mercury lamp for irradiation once to cure into a film.

[0199] ② Then use a 20-μm wire bar coater to apply the photocuring system on a white test card, expose it under a mercury lamp source to completely cure the sample, and finally use a color density meter to measure the surface yellowness value b.

[0200] Table 1

[0201] Component Volume percentage Epoxy acrylate resin E51 30％ 1,6 - Hexanediol diacrylate (HDDA) 10％ Trimethylolpropane triacrylate (TMPTA) 13％ Dispersant 3800 (dispersant, selected from Huihong additives) 2％ Titanium dioxide 40％ Photoinitiator (Examples 1 - 9 and Comparative Examples 1 - 3) 5％

[0202] (3) Odor: Ten odor judges evaluate the odor of the completely cured sample according to five levels: A - odorless, B - slightly odorous, C - odorous, D - pungent, and E - very pungent. The final average value is the test result.

[0203] (4) Solubility: Dissolve the photoinitiator in trimethylolpropane triacrylate (TMPTA), dipropylene glycol diacrylate (TPGDA), or 1,6 - hexanediol diacrylate (HDDA) to prepare samples with a concentration increment of 5%. After ultrasonic dissolution, let it stand in the dark at 40 °C for 72 h. Take no obvious precipitation as the standard to obtain the solubility of the initiator.

[0204] (5) Curing energy: Weigh the photoinitiator, resin, and monomer according to the ratio in Table 1 to form a photocuring system, use ultrasonic stirring to mix them evenly, coat the mixed coating on a white test card with a wire bar coater with a thickness of 10 μm, place it under a mercury lamp source for irradiation once to cure into a film. Press a 1 - kg weight on an A4 paper and pull it back and forth three times on the cured film. Take no scratch as the complete curing standard, and use a UV energy meter to record the energy required for curing.

[0205] (6) Adhesion: Prepare a photocuring system according to the ratio in Table 1, then use a 10-μm wire bar coater to apply the photocuring system on plastic substrates of different materials (polystyrene PS, polyvinyl chloride PVC, polyethylene terephthalate PET, polycarbonate PC), and expose it under a mercury lamp source to completely cure the sample. Then use the cross - cut method to test the adhesion. Use a wallpaper knife to evenly apply force perpendicular to the material surface and smoothly draw 6 parallel cutting lines, then draw 6 parallel lines perpendicular to the cutting lines at a 90° angle to form a grid pattern. Then stick a tape in the center of the formed grid, and quickly peel it off 10 times at an angle of about 60°. Observe the phenomenon of film peeling, and make a judgment according to the standard corresponding to the state of the grids in the cross - cut. Figure 6 for determination.

[0206] (7) Fluidity - Angle of repose test: 50 g of the powder is allowed to flow naturally from the funnel opening at a height of 10 cm. After flowing and coming to rest, the angle between the inclined plane of the powder cone formed on the plane and the horizontal plane is measured, which is the angle of repose °.

[0207] (8) Storage stability: Packed in 10 - kg cartons, 10 cartons are stacked and placed for one month. After opening, the number of cartons in which the powder remains relatively loose and does not caking is calculated.

[0208] (9) Substitutability of the dispersant: 5% of the photoinitiators in Examples 1, 7, 8, 9 and Comparative Examples 1 - 2 are respectively added to 1,6 - hexanediol diacrylate. 2% of the dispersant is added to each in System 1, and 1.5% of the dispersant is added to each in System 2. After the systems are mixed evenly, they are coated on a glass slide with a wire bar coater with a thickness of 10 μm, placed under a mercury lamp light source for irradiation, and the attenuation of double - bond groups with irradiation time during the photopolymerization process is monitored online by real - time infrared, and the infrared absorption intensity of key groups at each irradiation time is tracked to obtain the final double - bond conversion rate.

[0209] The test results are summarized in Table 2 - Table 4 and Figures 1 - 5 in.

[0210] Table 2

[0211]

[0212] Table 3

[0213]

[0214]

[0215] Table 4

[0216]

[0217] Analyzing the data in Table 2 and Table 3, it can be seen that the appearance color of the photoinitiator described in the present invention is white, the yellowness value is between 1.62 - 1.80, the odor grade is B, the fluidity is between 38.3° - 44.8°, the storage stability grade is between 9 - 10, the curing energy is between 66.9 - 77.8 mj·cm 2 ; the solubility in the monomer is between 50% - 65%, and the adhesion on the surfaces of different plastic substrates is between Grade 1 - Grade 2. The photoinitiator described in the present invention has the characteristics of light appearance color, low yellowness value, small odor, good fluidity and high storage stability, and has good solubility in the monomer, the formed photocuring system has a fast curing rate, high adhesion on the surfaces of different plastic substrates, and excellent comprehensive performance.

[0218] Analysis of the data in Table 4 shows that in the present invention, taking the double bond conversion rate as an example for experimental verification, it is proved that the photoinitiator described in the present invention can function as a dispersant. In the photocurable composition, the amount of the dispersant can be reduced without affecting the relevant properties.

[0219] Analysis of Comparative Example 1 and Example 1 shows that the performance of Comparative Example 1 is inferior to that of Example 1, proving that the photoinitiator with the structure described in the present invention has better performance.

[0220] Analysis of Comparative Example 2 and Example 1 shows that the performance of Comparative Example 2 is inferior to that of Example 1, proving that the photoinitiator with the structure described in the present invention has better performance in controlling the melting point within the range of 53 - 57 °C.

[0221] Analysis of Comparative Example 3 and Example 1 shows that the performance of Comparative Example 3 is inferior to that of Example 1 or basically the same as that of Example 1, proving that the photoinitiator described in the present invention also has advantages over the industrially mature photoinitiators.

[0222] Analysis of Examples 4 - 6 and Example 1 shows that the performance of Examples 4 - 6 is inferior to that of Example 1, proving that the photoinitiator described in the present invention has better performance in controlling the particle size distribution within the preferred range.

[0223] Analysis of Examples 7 - 9 and Example 1 shows that the performance of Example 9 is inferior to that of Example 1 and Examples 7 - 8, proving that the photoinitiator described in the present invention has better performance in controlling the morphology within the preferred range.

[0224] The applicant declares that the present invention uses the above - mentioned examples to illustrate the detailed method of the present invention, but the present invention is not limited to the above - mentioned detailed method, that is, it does not mean that the present invention must rely on the above - mentioned detailed method to be implemented. Those skilled in the art should understand that any improvement of the present invention, the equivalent substitution of each raw material of the product of the present invention, the addition of auxiliary components, the selection of specific methods, etc., all fall within the protection scope and the disclosure scope of the present invention.

Claims

1. A photoinitiator, characterized in that, The photoinitiator includes methyl 2,4,6-trimethylbenzoyl phenylphosphonate: The melting point of the photoinitiator is 53 - 57 °C.

2. The photoinitiator according to claim 1, wherein The morphology of the photoinitiator includes any one or a combination of at least two of cross-shaped, spherical, quasi-spherical or flaky; Preferably, the cross-shaped includes through-cross or non-through-cross; Preferably, the cross-shaped is formed by the cross of at least two regular and / or irregular columns.

3. The photoinitiator according to claim 1 or 2, characterized in that, The particle size distribution of the photoinitiator is: D50 is 40 - 80 μm.

4. The photoinitiator according to any one of claims 1-3, characterized in that, The D99 of the photoinitiator ≤ 150 μm.

5. The photoinitiator according to any one of claims 1-4, characterized in that, The molar extinction coefficient of the photoinitiator is 200 - 2500 L·mol -1 ·cm -1 .

6. A method for preparing a photoinitiator according to any one of claims 1-5, characterized in that, The preparation method includes the following steps: Mix dimethyl phenylphosphonate and 2,4,6-trimethylbenzoyl chloride, react and perform melt crystallization to obtain the photoinitiator.

7. The preparation method according to claim 6, characterized in that The temperature of the reaction is 40 - 60 °C; Preferably, the reaction time is 1 - 3 h.

8. The preparation method according to claim 6 or 7, characterized in that, The process of melt crystallization includes melting, crystallization, sweating and melting; Preferably, the melting includes operations of heating and heat preservation; Preferably, the temperature is raised to 60 - 65 °C; Preferably, the heat preservation time is 30 - 60 min; Preferably, the crystallization is carried out in a crystallization device, and the crystallization device includes a crystallization tank, an outer jacket arranged on the outer surface of the crystallization tank and an inner jacket arranged inside the crystallization tank; Preferably, during crystallization, the reaction liquid is placed in the crystallization tank, the temperature of the outer jacket is controlled, and the temperature of the inner jacket is adjusted for the first time to perform crystallization; Preferably, the temperature of the outer jacket is controlled to 40 - 60 °C; Preferably, the temperature of the inner jacket is adjusted for the first time to 10 - 45 °C; Preferably, the time taken to adjust the inner jacket to the temperature for the first time is 30 - 120 min; Preferably, after the inner jacket is adjusted to the temperature for the first time, it is maintained for 30 - 240 min; Preferably, the sweating includes discharging the reaction liquid after crystallization, adjusting the temperature of the inner jacket for the second time and reducing the pressure; Preferably, the temperature of the inner jacket is adjusted for the second time to 10 - 50 °C; Preferably, the time taken to adjust the inner jacket to the temperature for the second time is 30 - 240 min; Preferably, after the inner jacket is adjusted to the temperature for the second time, it is maintained for 30 - 240 min; Preferably, the pressure is reduced to 0.01 - 0.1 MPa; Preferably, after the pressure is reduced to 0.01 - 0.1 MPa, it is maintained for 30 - 240 min; Preferably, after sweating, the crystals on the surface of the inner jacket are collected and melted; Preferably, the melting temperature is 60 - 65 °C; Preferably, after melt crystallization, it also includes solvation treatment and drying; Preferably, the solvation treatment includes dissolving the material in a good solvent and then precipitating it in a poor solvent; Preferably, based on the mass of the material after melt crystallization being 100%, the mass of the good solvent is 25% - 45%; Preferably, the mass ratio of the good solvent to the poor solvent is 1:(1 - 10); Preferably, the good solvent includes any one or a combination of at least two of toluene, methanol, ethyl acetate, butyl acetate, isopropyl acetate or n-propyl acetate; Preferably, the poor solvent includes any one or a combination of at least two of water, petroleum ether, methylcyclohexane, n-heptane or n-hexane.

9. The preparation method according to any one of claims 6-8, characterized in that, The preparation method includes the following steps: (1) Mix dimethylphenylphosphonate and 2,4,6-trimethylbenzoyl chloride and react at 40-60 °C for 1-3 h; (2) Carry out melt crystallization on the material obtained in step (1); the melt crystallization specifically includes the following process: 1) Melting: Heat the material obtained in step (1) to 60-65 °C and keep it warm for 30-60 min; 2) Crystallization: Place the material obtained in step 1) in a crystallization device, which includes a crystallization tank, an outer jacket provided on the outer surface of the crystallization tank, and an inner jacket provided inside the crystallization tank; During the crystallization, the reaction solution is placed in the crystallization tank, the temperature of the outer jacket is controlled to 40-60 °C, and the temperature of the inner jacket is adjusted to 10-45 °C within 30-120 min and maintained for 30-240 min; 3) Sweating: Drain the reaction solution after crystallization, adjust the temperature of the inner jacket to 10-50 °C within 30-240 min, reduce the pressure to 0.01-0.1 MPa, and maintain for 30-240 min; 4) Collect the crystals on the surface of the inner jacket and melt them at 60-65 °C; (3) Dissolve the material obtained in step (2) in a good solvent, then precipitate it in a poor solvent, dry it after completing the solvation treatment, wherein, based on the mass of the material after melt crystallization being 100%, the mass of the good solvent is 25%-45%, and the mass ratio of the good solvent to the poor solvent is controlled to be 1:(1-10) to obtain the photoinitiator.

10. A photocurable composition, characterized in that, The photocurable composition includes a resin, a monomer, and the photoinitiator according to any one of claims 1-5.

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