Photoinitiator for UV-LED (Ultraviolet-Light Emitting Diode) as well as preparation and application of photoinitiator

Abstract

The invention relates to the technical field of photoinitiators, in particular to a photoinitiator for UV-LED and preparation and application thereof.The preparation method comprises the following steps that TPO-L acyl chloride is added into methylbenzene, morpholine or piperidine is added and mixed, temperature is controlled, stirring is conducted, triethylamine is dropwise added while stirring is conducted, then heating reaction is conducted, and the photoinitiator for UV-LED is obtained; after the reaction is finished, sequentially washing with water, diluted hydrochloric acid and a saturated sodium bicarbonate aqueous solution, drying with a drying agent, and performing reduced pressure distillation to obtain a product. A tertiary amine group (morpholine or piperidine) is introduced into the structure of the prepared photoinitiator, so that the absorption wavelength range of the photoinitiator is effectively widened, and particularly, the photoinitiator shows excellent application performance under the wavelength of 405 nm of a UV-LED (Ultraviolet-Light Emitting Diode).

Description

Technical Field

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

[0002] Photocuring technology is mainly used in the fields of fast-curing coatings, printing inks and adhesives. In the UV curing system, the photoinitiator absorbs energy of a specific wavelength and converts into active species, thereby triggering the polymerization reaction of the entire system. Photoinitiators are mainly divided into two categories: cleavage photoinitiators and hydrogen abstraction photoinitiators. After absorbing ultraviolet light energy, the cleavage photoinitiator will undergo an electronic transition to an excited state, and in this state, a bond will be broken to produce free radicals. The hydrogen abstraction photoinitiator mainly includes aromatic ketone compounds such as benzophenone, anthraquinone, and thioxanthone. Under light excitation, the hydrogen abstraction photoinitiator will be excited to a singlet state, and then transition to a more stable triplet state (T3) through intersystem crossing, and capture hydrogen atoms to achieve passivation; at the same time, the hydrogen donor forms an active free radical to trigger the subsequent polymerization reaction. Usually, the hydrogen donor is a tertiary amine compound, but it is easy to migrate in the cured product, causing the material to yellow or produce an unpleasant odor.

[0003] UV-LED (ultraviolet light emitting diode) is a semiconductor light emitting UV light source, which has the ability to directly convert electrical energy into light and radiation energy. Compared with traditional UV light sources such as mercury arc lamps and microwave electrodeless lamps, UV-LED has environmental protection characteristics such as long life, high efficiency, low voltage, low temperature operation, excellent safety, low operating cost, no mercury, no ozone generation, etc.

[0004] In the prior art, the degree of matching between the absorption spectrum of the photoinitiator and the emission spectrum of the UV-LED light source is poor. The maximum absorption wavelengths of the currently widely used photoinitiators in industrial applications, such as 1173, BP and 184, are located at 335nm, 345nm and 335nm, respectively. However, the emission wavelengths of industrial UV-LED light sources are mainly concentrated at 365nm, 385nm, 395nm and 405nm, so the spectral mismatch phenomenon significantly affects the photoinitiation efficiency. In addition, when the photoinitiator is excited to the triplet state, it is susceptible to the action of quenchers such as oxygen or monomers (such as styrene, unsaturated polyesters, etc.) and inactivated. This process reduces the generation of free radicals, thereby reducing the photoinitiation efficiency, especially the oxygen inhibition effect, which significantly weakens the photoinitiator's photoinitiator ability. In order to achieve a photoinitiator with low mobility, a method of increasing the molecular weight or introducing a polymerizable segment is usually adopted. However, increasing the molecular weight or introducing a polymerizable segment will increase the inert structure in the molecule, reduce the active part of the photoinitiator molecule that can effectively absorb light energy and trigger the polymerization reaction, thereby further reducing the photoinitiation efficiency. Summary of the invention

[0005] In order to solve the problems mentioned in the above background technology, the present invention provides a photoinitiator for UV-LED and its preparation and application.

[0006] In order to achieve the above object, the present invention adopts the following technical solutions:

[0007] A photoinitiator for UV-LED, the structural formula of which includes formula (I) and formula (II):

[0008]

[0009]

[0010] According to another aspect of the present invention, there is provided a method for preparing the above-mentioned photoinitiator, comprising the following steps:

[0011] Add TPO-L acyl chloride to toluene, add morpholine or piperidine and mix, control the temperature, add triethylamine dropwise while stirring, and then heat to react. After the reaction, wash with deionized water, acid wash with 5-10% dilute hydrochloric acid, and finally wash with saturated sodium bicarbonate aqueous solution, dry with a desiccant, and then distill under reduced pressure to obtain the product.

[0012] The reaction equation is:

[0013]

[0014] Furthermore, the molar ratio of toluene, TPO-L chloride, morpholine or piperidine and triethylamine is 5:1:(1-1.1):(1-1.2), wherein toluene, TPO-L chloride (molecular formula: C 16 H 16 O2PCl), morpholine (molecular formula C4H9NO) and triethylamine in a mass ratio of 460:310:(71-78.1):(101-121.2), toluene, TPO-L chloride (molecular formula C 16 H 16 O2PCl), piperidine (molecular formula is C5H 11 The mass ratio of N) and triethylamine is 460:310.5:(85-93.5):(101-121.2).

[0015] Furthermore, the desiccant includes one or more of anhydrous sodium sulfate, anhydrous magnesium sulfate or anhydrous calcium chloride, and the mass ratio of the desiccant to toluene is 1:8.

[0016] Furthermore, the stirring speed is 100-200 rpm, the stirring time is 10-30 min, and the temperature during stirring is 30-35°C.

[0017] Furthermore, the heating temperature is 30-40° C., and the reaction time is 2-10 h.

[0018] Further, TPO-L acyl chloride is prepared by the following steps:

[0019] TPO-L acid (molecular formula C 16 H 17 O3P, CAS No. 85073-04-7) was dispersed in toluene, thionyl chloride was added dropwise at room temperature, reacted at room temperature for 2-3 hours, and then heated to 40-45°C to react for 2-3 hours. After the reaction, toluene was evaporated, and the substrate was dried with toluene 2-3 times to obtain an oily product.

[0020] The reaction equation is:

[0021]

[0022] Further, the molar ratio of TPO-L acid, toluene and thionyl chloride is (0.2-0.3):1.6:(0.3-0.4), wherein the mass ratio of TPO-L acid, toluene and thionyl chloride is (57.6-86.4):147.2:(23.5-31.4).

[0023] According to another aspect of the present invention, there is provided an application of the above-mentioned photoinitiator, wherein the photoinitiator is applied to a UV-LED with a wavelength of 405 nm, 395 nm, 385 nm, 375 nm or 365 nm.

[0024] Compared with the prior art, the present invention has the following beneficial effects:

[0025] 1. The photoinitiator prepared by the present invention introduces a tertiary amine group (morpholine or piperidine) into its structure, which effectively broadens the absorption wavelength range of the photoinitiator, especially exhibiting excellent application performance at the 405nm wavelength of UV-LED. In addition, by introducing the tertiary amine group into the structure of the photoinitiator, the problem of unpleasant odor that may be generated by the photoinitiator during the photolysis process is effectively suppressed, thereby improving the safety and environmental protection of the product, which is more in line with the development requirements of modern green chemistry.

[0026] 2. The preparation method of the present invention is simple to operate and easy to realize industrial-scale production. The prepared photoinitiator can be more easily excited to a free radical state when exposed to light, which promotes the rapid cross-linking reaction, significantly improves the curing efficiency, accelerates the curing process of the polymer, and shows excellent application potential.

[0027] 3. The present invention not only broadens the absorption wavelength by introducing a tertiary amine group into the photoinitiator structure, but also enhances the resistance of the photoinitiator to the quencher by changing the electron distribution and stability inside the molecule, thereby reducing the deactivation phenomenon and improving the photoinitiator efficiency.

[0028] 4. The photoinitiator prepared by the present invention has both a lower mobility and a higher photoinitiating activity. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0030] Figure 1 is the H-NMR spectrum of the product obtained in Example 1 of the present invention;

[0031] Figure 2 The H-NMR spectrum of the product obtained in Example 4 of the present invention. DETAILED DESCRIPTION

[0032] The technical solution of the present invention will be clearly and completely described below in conjunction with the embodiments of the present invention. Obviously, the described embodiments are part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0033] Unless otherwise specified, the raw materials used in the present invention are all conventional products purchased from the market.

[0034] Preparation Example 1

[0035] TPO-L acyl chloride comprises the following steps to prepare:

[0036] Add 57.6-86.4g of TPO-L acid into 147.2g of toluene and disperse. Add 23.5-31.4g of thionyl chloride dropwise at room temperature. React at room temperature for 2-3h, then heat to 40-45℃ and react for 2-3h. After the reaction, evaporate the toluene and dry the substrate with toluene 2-3 times to obtain an oily product.

[0037] Preparation Example 2

[0038] TPO-L acyl chloride comprises the following steps to prepare:

[0039] 72g of TPO-L acid was dispersed in 147.2g of toluene, and 27.4g of thionyl chloride was added dropwise at room temperature. The mixture was reacted at room temperature for 2.5h, and then the temperature was raised to 42°C and reacted for 2.5h. After the reaction, the toluene was evaporated and the substrate was dried with toluene twice to obtain an oily product.

[0040] Preparation Example 3

[0041] TPO-L acyl chloride comprises the following steps to prepare:

[0042] 80g of TPO-L acid was dispersed in 147.2g of toluene, and 29g of thionyl chloride was added dropwise at room temperature. The mixture was reacted for 3h at room temperature, and then heated to 43°C for 3h. After the reaction, the toluene was evaporated and the substrate was dried with toluene for 3 times to obtain an oily product.

[0043] Preparation Example 4

[0044] TPO-L acyl chloride comprises the following steps to prepare:

[0045] 86.4g of TPO-L acid was dispersed in 147.2g of toluene, and 31.4g of thionyl chloride was added dropwise at room temperature. The mixture was reacted at room temperature for 3h, and then heated to 45°C for 3h. After the reaction, the toluene was evaporated and the substrate was dried with toluene for 3 times to obtain an oily product.

[0046] Example 1

[0047] A method for preparing a photoinitiator for UV-LED comprises the following steps:

[0048] Add 310g of TPO-L acyl chloride obtained in Preparation Example 1 to 460g of toluene, add 71g of morpholine and mix, control the temperature to stir at 30°C, add 101g of triethylamine dropwise at a speed of 100rpm while stirring, stir for 10min, then raise the temperature to 30°C and react for 2h. After the reaction, wash with 20mL of water, 20mL of 5% dilute hydrochloric acid, saturated sodium bicarbonate aqueous solution, and 20mL of water twice to obtain an organic layer, spin-dry the toluene, dry with a desiccant, and then distill under reduced pressure to obtain a solid product photoinitiator.

[0049] Example 2

[0050] A method for preparing a photoinitiator for UV-LED comprises the following steps:

[0051] Add 310g of TPO-L acyl chloride obtained in Preparation Example 2 to 460g of toluene, add 74g of morpholine and mix, control the temperature to stir at 30°C, add 110g of triethylamine dropwise at a speed of 150rpm while stirring, stir for 20min, then raise the temperature to 35°C and react for 6h. After the reaction, wash with 20mL of water, 20mL of 5% dilute hydrochloric acid, saturated sodium bicarbonate aqueous solution, and 20mL of water twice to obtain an organic layer, spin-dry the toluene, dry with a desiccant, and then distill under reduced pressure to obtain a solid product photoinitiator.

[0052] Example 3

[0053] A method for preparing a photoinitiator for UV-LED comprises the following steps:

[0054] Add 310g of TPO-L acyl chloride obtained in Preparation Example 3 to 460g of toluene, add 78.1g of morpholine and mix, control the temperature to stir at 35°C, add 121.2g of triethylamine dropwise at a speed of 200rpm while stirring, stir for 30min, then raise the temperature to 40°C and react for 10h. After the reaction, wash with 20mL of water, 20mL of 10% dilute hydrochloric acid, saturated sodium bicarbonate aqueous solution, and 20mL of water twice to obtain an organic layer, spin-dry the toluene, dry with a desiccant, and then distill under reduced pressure to obtain a solid product photoinitiator.

[0055] Example 4

[0056] A method for preparing a photoinitiator for UV-LED comprises the following steps:

[0057] Add 310g of TPO-L acyl chloride obtained in Preparation Example 4 to 460g of toluene, add 85g of piperidine and mix, control the temperature to stir at 30°C, add 121.2g of triethylamine dropwise at a speed of 100rpm while stirring, stir for 10min, then raise the temperature to 30°C and react for 2h. After the reaction, wash with 20mL of water, 20mL of 10% dilute hydrochloric acid, saturated sodium bicarbonate aqueous solution, and 20mL of water twice to obtain an organic layer, spin-dry the toluene, dry with a desiccant, and then distill under reduced pressure to obtain a solid product photoinitiator.

[0058] Example 5

[0059] A method for preparing a photoinitiator for UV-LED comprises the following steps:

[0060] Add 310g of TPO-L acyl chloride obtained in Preparation Example 1 to 460g of toluene, add 89g of piperidine and mix, control the temperature to stir at 32°C, add 110g of triethylamine dropwise at a speed of 150rpm while stirring, stir for 20min, then raise the temperature to 35°C and react for 6h. After the reaction, wash with 20mL of water, 20mL of 5% dilute hydrochloric acid, saturated sodium bicarbonate aqueous solution, and 20mL of water twice to obtain an organic layer, spin-dry the toluene, dry with a desiccant, and then distill under reduced pressure to obtain a solid product photoinitiator.

[0061] Example 6

[0062] A method for preparing a photoinitiator for UV-LED comprises the following steps:

[0063] Add 310g of TPO-L acyl chloride obtained in Preparation Example 2 to 460g of toluene, add 93.5g of piperidine and mix, control the temperature to stir at 35°C, add 121.2g of triethylamine dropwise at a speed of 200rpm while stirring, stir for 30min, then raise the temperature to 40°C and react for 10h. After the reaction, wash with 20mL of water, 20mL of 5% dilute hydrochloric acid, saturated sodium bicarbonate aqueous solution, and 20mL of water twice to obtain an organic layer, spin-dry the toluene, dry with a desiccant, and then distill under reduced pressure to obtain a solid product photoinitiator.

[0064] (I) Mobility test: 1 part by weight of the photoinitiator sample prepared in Example 1-6 was mixed with 99 parts by weight of 1,6-diacetoxyhexane (HDDA), stirred to dissolve, and a pre-cured sample was obtained; the pre-cured sample was evenly coated on a test plate, irradiated with a UV-LED point light source with a wavelength of 405 nm for 120 seconds to ensure complete curing, the cured film was crushed into powder, the cured film was weighed and added to 5 mL of acetonitrile, stirred for 48 hours, and filtered to obtain an extract, which was fixed to 10 mL. The absorbance of the extract was tested, and the concentration of the photoinitiator extract was calculated according to the Lambert-Beer formula, and the mobility of the photoinitiator was calculated. The calculation formula of the mobility is as follows:

[0065]

[0066] Wherein, A is the absorbance of the extract at the maximum absorption wavelength of the photoinitiator, Mr is the relative molecular mass of the photoinitiator, V is the volume of the extract, ε is the molar extinction coefficient at the maximum absorption wavelength of the photoinitiator, l is the optical path (1 cm), m0 is the mass of the cured film powder, and b is the mass percentage of the photoinitiator.

[0067] Another control group was set up, and the photoinitiator used commercially available 2,4,6-trimethylbenzoylphenylphosphonic acid ethyl ester (TPO-L). The mobility results are shown in Table 1:

[0068] Table 1. Migration rates of Examples 1-6 and the control group

[0069] serial number Migration rate / % Example 1 0.06 Example 2 0.08 Example 3 0.06 Example 4 0.06 Example 5 0.04 Example 6 0.08 Control group 0.3

[0070] (II) Photopolymerization efficiency test: Mix 1 part of each photoinitiator with 99 parts of HDDA, spread a drop of the mixture evenly on a polypropylene film, press a layer of polypropylene film on the upper surface to isolate oxygen, and the coating thickness is about 40μm. Irradiate with a UV-LED light source with a wavelength of 385nm and 405nm. After the real-time infrared spectrometer is turned on for 10s, turn on the light source, the illumination time is 170s, and the light intensity is 100mW / cm 2 In this experiment, 1720cm -1 The C=O stretching vibration at 810 cm was used as the internal standard. -1 The bending vibration peak of the C=C double bond changes. The photopolymerization efficiency (DC%) of the photoinitiator is calculated as follows:

[0071]

[0072] Where A0 is the peak area before light curing, and At is the peak area at time t after the real-time infrared is turned on.

[0073] Another control group was set up, and the photoinitiator used commercially available 2,4,6-trimethylbenzoylphenylphosphonic acid ethyl ester (TPO-L). The photopolymerization efficiency results are shown in Table 2:

[0074] Table 2. Photopolymerization efficiency of Examples 1-6 and the control group

[0075] serial number <![CDATA[DC 120 (385nm) / %]]> <![CDATA[DC 120 (405nm) / %]]> Example 1 51.57 67.27 Example 2 55.82 68.24 Example 3 53.23 65.45 Example 4 53.27 63.84 Example 5 59.75 69.25 Example 6 58.36 65.98 Control group 52.54 51.09

[0076] As can be seen from Table 1, the mobility of the photoinitiator samples prepared in Examples 1-6 is significantly lower than that of the control group (commercially available TPO-L). Specifically, the mobility of the photoinitiators in the examples is between 0.04% and 0.08%, while the mobility of the control group TPO-L is 0.3%. This indicates that the photoinitiator prepared by the present invention has a lower mobility in the cured film, which is significantly better than the commercially available product. The photoinitiators prepared in Examples 1-6 may increase the interaction between the photoinitiator molecules and the substrate of the curing system, making it more difficult to migrate out of the cured film. In addition, it may also be related to the reactivity of the photoinitiator during the curing process and its ability to bind to the polymer network.

[0077] As can be seen from Table 2, under the irradiation of 385nm and 405nm UV-LED light sources, the photopolymerization efficiency (DC%) of the photoinitiators prepared in Examples 1-6 is higher than that of the control group (commercially available TPO-L), especially under the 405nm light source. The photopolymerization efficiency of TPO-L at 405nm is lower than that of the photoinitiators prepared in Examples 1-6. The photoinitiators prepared in Examples 1-6 may broaden the absorption wavelength range of the photoinitiator and improve its absorption efficiency under the UV-LED light source by introducing tertiary amine groups. They may also enhance the resistance of the photoinitiator to quenchers and reduce the deactivation of free radicals by changing the electron distribution and stability within the molecule. Therefore, under the same lighting conditions, the photoinitiators in the examples can produce more free radicals, thereby improving the photopolymerization efficiency.

[0078] In summary, the photoinitiators prepared in Examples 1-6 not only have lower mobility but also maintain higher photopolymerization efficiency.

[0079] In the description of the specification, the description with reference to the terms "preparation example", "embodiment", "various embodiments" and the like means that the specific features, structures, materials or characteristics described in conjunction with the embodiment or preparation example are included in at least one embodiment or preparation example of the present invention. In this specification, the schematic representation of the above terms does not necessarily refer to the same embodiment or preparation example. Moreover, the specific features, structures, materials or characteristics described can be combined in any one or more embodiments or preparation examples in a suitable manner.

[0080] The above description is only a preferred specific implementation manner of the present invention, but the protection scope of the present invention is not limited thereto. Any technician familiar with the technical field can make equivalent replacements or changes according to the technical scheme and inventive concept of the present invention within the technical scope disclosed by the present invention, which should be covered by the protection scope of the present invention.

Claims

1. A photoinitiator for UV-LED, characterized in that: Its structural formula includes formula (I) and formula (II):

2. A method for preparing a photoinitiator as claimed in claim 1, characterized in that: The following steps are involved: Add TPO-L acyl chloride to toluene, add morpholine or piperidine, mix, control the temperature and stir, add triethylamine dropwise while stirring, and then heat to react. After the reaction, wash with water, dilute hydrochloric acid, and saturated sodium bicarbonate aqueous solution in sequence, dry with a desiccant, and then distill under reduced pressure to obtain the product.

3. The preparation method according to claim 2, characterized in that: The molar ratio of toluene, TPO-L chloride, morpholine or piperidine and triethylamine is 5:1:(1-1.1):(1-1.2).

4. The preparation method according to claim 2, characterized in that: The desiccant includes one or more of anhydrous sodium sulfate, anhydrous magnesium sulfate or anhydrous calcium chloride, and the mass ratio of the desiccant to toluene is 1:

8.

5. The preparation method according to claim 2, characterized in that: The stirring speed is 100-200 rpm, the stirring time is 10-30 min, and the stirring temperature is 30-35°C.

6. The preparation method according to claim 2, characterized in that: The temperature is raised to 30-40°C and the reaction time is 2-10h.

7. The preparation method according to claim 2, characterized in that: TPO-L acyl chloride comprises the following steps to prepare: Add TPO-L acid to toluene and disperse it, add thionyl chloride dropwise at room temperature, react at room temperature for 2-3 hours, then heat to 40-45°C and react for 2-3 hours. After the reaction, evaporate the toluene, and dry the substrate with toluene 2-3 times to obtain an oily product.

8. The preparation method according to claim 6, characterized in that: The molar ratio of TPO-L acid, toluene and thionyl chloride is (0.2-0.3):1.6:(0.3-0.4).

9. A use of the photoinitiator as claimed in claim 1, characterized in that: The photoinitiator is applied to UV-LED with a wavelength of 405nm, 395nm, 385nm, 375nm or 365nm.

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