Polymerizable benzophenone photoinitiator as well as synthesis method and application thereof

Abstract

The invention relates to the field of photoinitiators, and discloses a polymerizable benzophenone photoinitiator as well as a synthesis method and application thereof. The benzophenone photoinitiator provided by the invention can be polymerized into a curing system while initiating polymerization of the curing system, so that the problem of migration of fragments after photolysis of a traditional photoinitiator is solved, and the problems that the photolysis fragments migrate to the surface of a curing film, the surface performance is influenced, and the surface of the curing film is yellowed are solved. Ink added with the polymerizable benzophenone photoinitiator provided by the invention is excellent in curability, adhesive force and glossiness after being cured by ultraviolet light, is more excellent in alcohol resistance than the traditional photoinitiator 4, 4 '-bis (diethylamino) benzophenone (EMK), and does not migrate in alcohol.

Description

Technical Field

[0001] The invention relates to the field of photoinitiators, and in particular to a polymerizable benzophenone photoinitiator and a synthesis method and application thereof. Background Art

[0002] Photocuring refers to the curing process of monomers, oligomers or polymer matrices under light induction, which is generally used in the film-forming process. UV curing systems usually include photoinitiators, monomers, photocurable resins and other additives, among which photoinitiators are an important component in the system.

[0003] Photoinitiators are divided into two categories according to the photolysis mechanism: free radical polymerization photoinitiators and cationic polymerization photoinitiators, and free radical photoinitiators are the most widely used. Free radical photoinitiators can be divided into cleavage photoinitiators and hydrogen abstraction photoinitiators according to the mechanism of generating free radicals. Benzophenone or heterocyclic aromatic ketone compounds are the most commonly used and important types of hydrogen abstraction photoinitiators. However, when benzophenone or heterocyclic aromatic ketone compounds are used as photoinitiators, there are migration problems, such as migration to the surface of the curing material layer, affecting the performance of the curing material layer.

[0004] In order to solve the migration problem of photoinitiators, various technical methods have been developed and reported at home and abroad, mainly including copolymerizable photoinitiators and macromolecular photoinitiators. In order to overcome these problems, it is necessary to carefully consider the molecular weight adjustment and distribution of the starting site in the molecular chain, with better performance, such as high photoreactivity, good solubility in formulations, low odor and toxicity. The problem of darkening of the cured film due to the migration of residues in the cured film and the problem of good storage stability of the cured film have become important issues in the development of photoinitiators. Summary of the invention

[0005] In order to solve the above-mentioned migration problem of the photoinitiator, the present invention provides a polymerizable benzophenone photoinitiator and a synthesis method and application thereof.

[0006] The specific technical scheme of the present invention is: In a first aspect, the present invention provides a polymerizable benzophenone photoinitiator having the structural formula:

[0007] Benzophenone photoinitiators will produce specific photolytic fragments during the photolysis process, such as carbonyl radicals, etc. These photolytic fragments will migrate in the cured film, causing problems such as changes in the properties of the cured film and darkening of the cured film.

[0008] The benzophenone photoinitiator provided by the present invention can be polymerized into the curing system while initiating the polymerization of the curing system, thereby overcoming the migration problem of fragments of the traditional photoinitiator after photolysis, and solving the problem that the photolysis fragments migrate to the surface of the cured film, affect the surface properties, and cause the surface of the cured film to turn yellow. In the field of photocuring, the curing system usually includes a photoinitiator, a monomer, a photocuring resin and other additives. The system can initiate a polymerization reaction under ultraviolet light to cure.

[0009] In a second aspect, the present invention provides a method for synthesizing the benzophenone photoinitiator as described above, comprising the following steps: reacting bis(4-(piperazine-1-yl)phenyl)methanone and acryloyl chloride as raw materials under an inert gas atmosphere.

[0010] The present invention uses bis(4-(piperazine-1-yl)phenyl)methanone and acryloyl chloride as raw materials to synthesize the benzophenone photoinitiator described in formula (I), and can successfully synthesize the benzophenone photoinitiator described in formula (I) with a good yield.

[0011] As a preferred embodiment of the above synthesis method, the reaction is carried out in an organic solvent.

[0012] As a preferred embodiment of the above synthesis method, the organic solvent is one or more of dichloromethane, dichloroethane and tetrahydrofuran.

[0013] The polarity of the solvent, the solubility of the solvent in the raw materials, etc., have a significant effect on the reaction yield. Non-polar solvents are not conducive to electron transfer and may lead to a decrease in photopolymerization yield; while strong polar solvents may reduce the triplet quantum yield of the photoinitiator, which also leads to a decrease in yield. Among the synthetic raw materials of the present invention, selecting dichloromethane, dichloroethane, and tetrahydrofuran as solvents can give benzophenone photoinitiators a better yield, and the organic solvent is more preferably dichloromethane.

[0014] As a preferred embodiment of the above synthesis method, a base is added to the organic solvent.

[0015] As a preferred embodiment of the above synthesis method, the base is one or more of triethylamine, K2CO3, KOH, and sodium tert-butoxide.

[0016] More preferably, the base is triethylamine.

[0017] The type and concentration of the base directly affect the reaction. An appropriate base can promote the reaction. The base is preferably triethylamine.

[0018] The synthesis method of the present invention is carried out in an inert gas atmosphere, such as nitrogen, which can remove oxygen from the reaction system and prevent the raw materials from being oxidized, thereby ensuring the smooth progress of the reaction.

[0019] As a preferred embodiment of the above synthesis method, the ratio of the added amounts of bis(4-(piperazine-1-yl)phenyl)methanone, acryloyl chloride and base is 100:200-400:200-400 based on the amount of the substance.

[0020] As a preferred embodiment of the above synthesis method, the reaction temperature is 0 to 40° C. and the reaction time is 2 to 8 hours.

[0021] Temperature is an important factor affecting the rate of chemical reactions. Appropriate temperature can increase the reaction rate, but too high a temperature may lead to side reactions and reduce the yield.

[0022] As a preferred embodiment of the above-mentioned synthesis method, the preparation method of bis(4-(piperazine-1-yl)phenyl)methanone is as follows: under an inert gas atmosphere, 4,4'-difluorobenzophenone and anhydrous piperazine are added to an alkali-containing organic solvent to react to obtain bis(4-(piperazine-1-yl)phenyl)methanone. Wherein: The base is preferably K2CO3, Na2CO3, KOH, sodium tert-butoxide; the organic solvent is preferably dimethyl sulfoxide, N,N'dimethylformamide, N,N'dimethylacetamide; the molar ratio of 4,4'-difluorobenzophenone to anhydrous piperazine and base is preferably 100:200-400:200-500; the reaction temperature is 150-210°C, and the reaction time is 8-16 hours.

[0023] The following is the process of the synthesis method of the above-mentioned benzophenone photoinitiator: In a third aspect, the present invention provides the use of the benzophenone photoinitiator synthesized by the above synthesis method in photocuring.

[0024] The polymerizable benzophenone photoinitiator represented by formula (I) provided by the present invention can be used in photocuring, for example, can be used to prepare UV ink. In the embodiment of the present invention, after the ink to which the polymerizable benzophenone photoinitiator represented by formula (I) is added is cured by ultraviolet light, the curing property, adhesion and glossiness are excellent, and the alcohol resistance is better than that of the traditional photoinitiator 4,4'-bis(diethylamino)benzophenone (EMK), and there is no migration in alcohol, which solves the problems of easy migration and odor of the commonly used photoinitiators in the prior art.

[0025] Compared with the prior art, the present invention has the following technical effects: (1) The present invention provides a benzophenone photoinitiator, which can be polymerized into the curing system while initiating the polymerization of the curing system, thereby overcoming the problem of migration of fragments of traditional photoinitiators after photolysis, and solving the problem that the photolysis fragments migrate to the surface of the cured film, affect the surface properties, and cause yellowing of the cured film surface.

[0026] (2) The present invention successfully synthesizes the benzophenone photoinitiator described in formula (I) by using bis(4-(piperazine-1-yl)phenyl)methanone and acryloyl chloride as raw materials with a good yield. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] Figure 1 This is the H NMR spectrum of the polymerizable benzophenone photoinitiator prepared in Example 4; Figure 2 This is the NMR carbon spectrum of the polymerizable benzophenone photoinitiator prepared in Example 4. DETAILED DESCRIPTION

[0028] The present invention will be further described below in conjunction with embodiments. Those of ordinary skill in the art will be able to implement the present invention based on these descriptions. In addition, the embodiments of the present invention involved in the following description are generally only embodiments of a part of the present invention, rather than all embodiments. Therefore, based on the embodiments in the present invention, all other embodiments obtained by those of ordinary skill in the art without making creative work should belong to the scope of protection of the present invention.

[0029] Example 1 Synthesis of Bis(4-(Piperazine-1-yl)phenyl)methanone Add 50mmol of 4,4'-difluorobenzophenone, 150mmol of anhydrous piperazine, 125mmol of K2CO3 and 100mL of N,N-dimethylformamide to the reactor. Then replace the air in the reactor with nitrogen, so that the reaction in the reactor is carried out under nitrogen conditions. Then, heat the liquid in the reactor to 180°C under stirring conditions, react for 10 hours, and after cooling, directly perform vacuum distillation on the reaction liquid to obtain a crude product after removing the solvent. Dissolve the crude product fully with ethanol, separate by suction filtration, collect the filtrate containing the target compound, and evaporate the solvent to obtain the product bis(4-(piperazine-1-yl)phenyl)methanone, with a yield of 85%.

[0030] The product was subjected to NMR analysis, and the results were as follows: 1 HNMR (400M, CDCl3): δ7.77(d,J=8.8Hz,4H), 6.91(d,J=8.8Hz,4H), 6.58-6.65(m,2H), 6.36(dd,J1=16. 8Hz, J2=1.6Hz, 2H), 5.77 (dd, J1=10.6Hz, J2=1.8Hz, 2H), 3.81 (d, J=43.5Hz, 8H), 3.40 (t, J=5.3Hz, 8H).

[0031] 13CNMR (100M, CDCl3): δ194.0,153.9,132.0,128.4,113.4,48.7,45.9.

[0032] Example 2 Synthesis of Bis(4-(Piperazine-1-yl)phenyl)methanone The difference between this embodiment and embodiment 1 is that the reaction temperature is 200° C. The other conditions are the same as those of embodiment 1.

[0033] The yield of the product bis(4-(piperazine-1-yl)phenyl)methanone in this example is 91%.

[0034] Example 3 Synthesis of Bis(4-(Piperazine-1-yl)phenyl)methanone The difference between this embodiment and embodiment 1 is that the reaction temperature is 200° C. and the reaction solvent is dimethyl sulfoxide. The rest is the same as embodiment 1.

[0035] The yield of the product bis(4-(piperazine-1-yl)phenyl)methanone in this example is 95%.

[0036] Example 4 Synthesis of polymerizable benzophenone photoinitiator (I) 50 mmol of bis(4-(piperazine-1-yl)phenyl)methanone, 150 mmol of acryloyl chloride, 150 mmol of triethylamine and 100 mL of tetrahydrofuran were added to the reactor, and then the air in the reactor was replaced with nitrogen. The reaction was stirred at 25° C. for 4 h. The reaction solution was directly mixed with silica gel and separated by column chromatography. The eluate containing the target compound was collected and the solvent was evaporated to obtain the product, a polymerizable benzophenone photoinitiator (I), with a yield of 61%.

[0037] The structural formula of the polymerizable benzophenone photoinitiator is shown in formula (I):

[0038] The product was taken for NMR analysis. The NMR hydrogen spectrum and carbon spectrum were shown in Figure 1 and 2 , the spectrum data are as follows: 1 HNMR (400M, CDCl3): δ7.72(d,J=8.8Hz,4H), 6.87(d,J=8.8Hz,4H), 3.28(t,J=4.8Hz,8H), 3.00(t,J=4.4Hz,8H).

[0039] 13 CNMR (100M, CDCl3): δ193.9,165.4,153.0,132.0,129.0,128.5,127.1,113.9,47.9,47.5,45.3,41.5.

[0040] Example 5 Synthesis of polymerizable benzophenone photoinitiator The difference between this embodiment and embodiment 4 is that tetrahydrofuran is replaced by dichloromethane. The other parts are the same as those of embodiment 4.

[0041] The yield of the product benzophenone photoinitiator in this example is 75%.

[0042] Example 6 Synthesis of polymerizable benzophenone photoinitiator The difference between this embodiment and embodiment 4 is that tetrahydrofuran is replaced by ethylene dichloride. The other parts are the same as those of embodiment 4.

[0043] The yield of the product benzophenone photoinitiator in this example is 69%. Others are the same as those in Example 4.

[0044] Example 7 Synthesis of polymerizable benzophenone photoinitiator The difference between this embodiment and embodiment 4 is that the reaction temperature is 40° C. The other conditions are the same as those of embodiment 4.

[0045] The yield of the product benzophenone photoinitiator in this example is 63%.

[0046] Example 8 Synthesis of polymerizable benzophenone photoinitiator The difference between this embodiment and embodiment 4 is that the reaction temperature is 0° C. The other conditions are the same as those of embodiment 4.

[0047] The yield of the product benzophenone photoinitiator in this example is 40%.

[0048] Example 9 Synthesis of polymerizable benzophenone photoinitiator The difference between this embodiment and embodiment 4 is that the reaction temperature is 10° C. The other conditions are the same as those of embodiment 4.

[0049] The yield of the product benzophenone photoinitiator in this example is 69%.

[0050] Example 10 Synthesis of polymerizable benzophenone photoinitiator The only difference between this embodiment and embodiment 4 is that tetrahydrofuran is replaced by dichloromethane and the reaction temperature is 10° C. The rest is the same as embodiment 4.

[0051] The yield of the benzophenone photoinitiator product in this example is 81%.

[0052] Example 11 Evaluation of the Photoinitiating Performance of the Polymerizable Benzophenone Photoinitiator (I) (1) A UV-curable ink sample was prepared using the benzophenone photoinitiator (I) prepared in Example 4 as a photoinitiator, and the method was as follows: 60% of UV ink prepolymer (a mixture of rosin-modified epoxy acrylate and ditrimethylolpropane tetraacrylate in a mass ratio of 1:1), 5% of TMPTA, 3% of TPO-L, 3% of DETX, 20% of carbon black, 4% of wax powder, 2% of kaolin and 3% of polymerizable benzophenone photoinitiator (I) were prepared by mass fraction, and the mixture was finely dispersed on a three-roll mill for 3 times to obtain a UV-curable ink sample A with a fineness of ≤12.5 μm.

[0053] (2) A UV-curable ink sample was prepared using the conventional photoinitiator 4,4'-bis(diethylamino)benzophenone (EMK) as a photoinitiator, as follows: the 3% polymerizable benzophenone photoinitiator (I) in step (1) was replaced with 3% conventional photoinitiator 4,4'-bis(diethylamino)benzophenone (EMK), and the proportions of other raw materials remained unchanged, to prepare a UV-curable ink sample B.

[0054] (3) Performance test comparison of sample A and sample B: Referring to "CY / T127-2015 Preparation method for testing volatile organic compounds in printed materials for paper printed products", the sample A was tested at 128g / m 2 Color development on coated paper to obtain printed proofs, with a power density of 10W / cm 2 The samples were cured under UV light to obtain coated paper prints. The results showed that the curing properties, adhesion and glossiness of samples A and B were similar.

[0055] Furthermore, the alcohol resistance of the photoinitiator was tested on coated paper prints. The method is: soak the coated paper prints in a 20% concentration (v / v) alcohol solution for 1 to 13 days, and test their specific migration on the 1st, 5th, 9th, and 13th days respectively. The migration test results are shown in Table 1, where ND stands for no migration. The migration test refers to GB 31604.1-2015.

[0056] Table 1 Alcohol migration test results The results of the alcohol resistance test show that sample A has no migration, while sample B has a migration rate of 1.29 mg / m on the 13th day of immersion. 2 It can be seen that sample A has better alcohol migration resistance than sample B.

[0057] The raw materials and equipment used in the present invention, unless otherwise specified, are all commonly used raw materials and equipment in the art; the methods used in the present invention, unless otherwise specified, are all conventional methods in the art.

[0058] The above description is only a preferred embodiment of the present invention and does not limit the present invention in any way. Any simple modification, change and equivalent transformation made to the above embodiment based on the technical essence of the present invention still falls within the protection scope of the technical solution of the present invention.

Claims

1. A polymerizable benzophenone photoinitiator, characterized in that: Its structural formula is:

2. The method for synthesizing a benzophenone photoinitiator according to claim 1, wherein: The following steps are involved: Under an inert gas atmosphere, the reaction is carried out using bis(4-(piperazin-1-yl)phenyl)methanone and acryloyl chloride as raw materials.

3. The method for synthesizing a benzophenone photoinitiator according to claim 2, wherein: The reaction is carried out in an organic solvent.

4. The method for synthesizing a benzophenone photoinitiator according to claim 3, wherein: The organic solvent is one or more of dichloromethane, dichloroethane and tetrahydrofuran.

5. The method for synthesizing a benzophenone photoinitiator according to claim 3, wherein: A base is added to the organic solvent.

6. The method for synthesizing a benzophenone photoinitiator according to claim 5, wherein: The base is one or more of triethylamine, K2CO3, KOH, and sodium tert-butoxide.

7. The method for synthesizing a benzophenone photoinitiator according to claim 6, wherein: Calculated by the amount of substance, the ratio of the added amounts of bis(4-(piperazine-1-yl)phenyl)methanone, acryloyl chloride and alkali is 100:200-400:200-400.

8. The method for synthesizing a benzophenone photoinitiator according to claim 2, wherein: The reaction temperature is 0-40° C., and the reaction time is 2-8 hours.

9. The method for synthesizing a benzophenone photoinitiator according to claim 2, wherein: The preparation method of the bis(4-(piperazine-1-yl)phenyl)methanone is as follows: under an inert gas atmosphere, 4,4'-difluorobenzophenone and anhydrous piperazine are added to an alkali-containing organic solvent for reaction to obtain bis(4-(piperazine-1-yl)phenyl)methanone.

10. Use of the benzophenone photoinitiator according to claim 1, or the benzophenone photoinitiator synthesized by the synthesis method according to any one of claims 2 to 9 in photocuring.

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