Crosslinkable alpha-hydroxyacetophenone photoinitiator

Abstract

The invention provides a crosslinkable efficient alpha-hydroxyacetophenone photoinitiator which has a double-benzene-ring structure, a benzene ring on one side has an alpha-hydroxyacetophenone structure, and a benzene ring on the other side has a polymerizable carbon-carbon double bond. Due to the structural design, free radical active sites can be generated under illumination, and two ends can participate in photopolymerization, so that the photoinitiator can serve as a cross-linking agent in a polymerization system, and the photoinitiator has the characteristic of low migration.

Description

Technical Field

[0001] The invention belongs to the field of photopolymerization and relates to a high-efficiency photoinitiator with cross-linking ability. background

[0003] Photopolymerization refers to the process in which some substances in the system absorb light energy to generate active species that initiate the polymerization of oligomers or monomers. After a long period of development, it is no longer limited to the relatively basic fields such as coatings, printing and adhesives, but is also widely used in new fields such as microelectronics, biomedicine, photoresist, 3D printing, and new energy. It is the theoretical basis for many hot scientific research fields today. Photopolymerization technology is highly favored in today's society because of its advantages such as "energy saving, economy, environmental friendliness, high efficiency, and wide adaptability", and is considered a green technology.

[0004] However, some events in recent years (Nestle toxic milk powder, toxic breakfast milk, toxic oatmeal, etc.) have impacted the development of photopolymerization technology. A large number of facts and studies have shown that the important component of the photopolymerization system, the photoinitiator, can migrate from the photocurable product to the environment. The migration of photoinitiators has attracted the attention of the industry, the scientific research community and ordinary people. Nestle has established relevant guidelines (Nestle Guidance Note on Packaging Inks) based on the Swiss Regulation 817.023.21V2016 to regulate and restrict the use of photoinitiators. The European Union has also issued relevant laws and regulations, which explicitly prohibit the use of some photoinitiators in the field of food packaging. Many studies in recent years have further found the presence of photoinitiators in the human living environment, blood, and breast milk of pregnant women. As a new technology, photopolymerization has been widely used in real life. How to effectively reduce or eliminate the migration rate of its photoinitiator to make photopolymer products more green and safe is an urgent issue to be solved.

[0005] The migration problem of photoinitiators has created a huge obstacle to the development of photopolymerization, and the application fields of some high-efficiency photoinitiators are strictly restricted. In order to solve this problem, enterprises and academia have made great efforts and have successively launched a variety of new photoinitiators such as macromolecular photoinitiators HMPP-1, HMPP-2, Ominopol BP, Ominopol TX, Ominopol ASA, Ominopol SZ, Ominopol 910, etc. However, they still have problems, such as poor compatibility with monomers or resins, easy to cause excessive local cross-linking density, poor photoinitiation efficiency, high cost of use, etc., and cannot meet the requirements of actual use. Therefore, it is an urgent problem to develop a photoinitiator with high monomer / resin compatibility, low mobility and high initiation activity.

[0006] The present invention designs a small molecule α-hydroxyacetophenone photoinitiator structure which has both polymerizable carbon-carbon double bonds and high photoinitiating activity, and has excellent monomer resin compatibility. Due to the special structural design, the photoinitiator can both generate active sites for initiating polymerization and participate in the polymerization reaction, so it can act as a crosslinking agent in the system, and the photoinitiator migration rate of the cured product obtained therefrom is extremely low. Summary of the invention

[0007] The purpose of the present invention is to provide a preparation method and application of a photoinitiator having both cross-linking ability and high efficiency.

[0008] In order to achieve the above-mentioned purpose, the first part proposes the following general structure of the photoinitiator, which is characterized by having a double benzene ring structure, one benzene ring of which has an α-hydroxyacetophenone structure, and the other benzene ring has a polymerizable (meth)acrylate structure.

[0009]

[0010] Wherein R1 is a carbon-carbon single bond, a methylene group, an oxygen atom, or a sulfur atom;

[0011] The structure of R2 is selected from any one of the following structures:

[0012]

[0013] Wherein R3 is a methyl group or a hydrogen atom.

[0014] The above-mentioned photoinitiator has a photoactive group hydroxyacetophenone structure on one side and a polymerizable double bond on the other side, which can participate in the polymerization reaction and has the characteristics of self-polymerization. The photoactivity of the hydroxyacetophenone structure is not affected, and after being irradiated, it can quickly undergo α-cleavage to generate free radicals to initiate polymerization. On the other hand, the free radical active site and the carbon-carbon double bond can serve as crosslinking points to participate in the photopolymerization reaction of the polymer chain.

[0015] The second part of the present invention also provides a curing composition, which comprises the photoinitiator described in the first part, characterized in that it is not necessary to add a traditional multifunctional monomer / resin as a crosslinking agent, and only the photoinitiator can make the system chemically crosslinked. The molar proportion of the crosslinking agent type photoinitiator in the curing composition is 0.5-50mol%, preferably 1.5mol%, 2mol%, and the selected monomer is a single-tube monomer / resin. DETAILED DESCRIPTION

[0016] Example 1

[0017] Specifically, 1,1'-(methylenedi-4,1-phenylene)bis[2-hydroxy-2-methyl-1-propanone] (5mmol, 1.7021g) was added to a three-necked flask, followed by 4-dimethylaminopyridine (DMAP, 1mmol, 0.1222g), followed by dicyclohexylcarbodiimide (DCC, 5mmol, 2.0316), followed by 80ml of dichloromethane, magnetic stirring was turned on, and stirring was carried out for 30min; acrylic acid (AC, 5mmol, 0.3203g) was weighed and quickly added to the three-necked flask; the reaction was carried out at room temperature for 48h. After the reaction was completed, the reaction solution was filtered to remove the solid in the system; the filtrate was washed three times with saturated saline, saturated sodium bicarbonate aqueous solution, and saturated saline, and then anhydrous sodium sulfate was added to the organic phase and allowed to stand overnight to remove water; after filtering to remove anhydrous sodium sulfate, rotary evaporation was performed, and column chromatography was used for purification, and the ratio of the chromatographic liquid was petroleum ether: ethyl acetate = 10:1 (v / v). Finally, product A is obtained.

[0018] The structural formula of the compound obtained in this example is

[0019]

[0020] Example 2

[0021] Specifically, 1,1'-(methylenedi-4,1-phenylene)bis[2-hydroxy-2-methyl-1-propanone] (5mmol, 1.7021g) was added to a three-necked flask, and then a certain amount of toluene was added. The magnetic stirring was turned on under ice-salt bath conditions, and stirred for 30min, and then a small amount of concentrated sulfuric acid was added; acrylic anhydride (AAD, 5mmol, 0.6305g) was weighed and slowly added dropwise using a constant pressure funnel; after the addition was completed, stirring was continued for 5min and then the ice-salt bath was removed, and the reaction was carried out at room temperature for 2-4h. After the reaction was completed, 100ml of deionized water was quickly added to the reaction bottle; after separation, anhydrous sodium sulfate was added to the organic phase and allowed to stand overnight to remove water; after suction filtration to remove anhydrous sodium sulfate, rotary evaporation was performed, and column chromatography was used for purification, and the ratio of the chromatographic liquid was petroleum ether: ethyl acetate = 10:1. Finally, compound A was obtained.

[0022] Example 3

[0023] Specifically, 1,1'-(methylenedi-4,1-phenylene)bis[2-hydroxy-2-methyl-1-propanone] (5mmol, 1.7021g) was added to a three-necked flask, followed by 80ml of dichloromethane, followed by triethylamine (TEA, 5mmol, 0.5024g), magnetic stirring was turned on, and stirring was continued for 30min; methacryloyl chloride (MAC, 5mmol, 0.4305g) was weighed, dissolved in 20ml of dichloromethane, and slowly added dropwise using a constant pressure funnel; the reaction was continued at room temperature for 2-4h. After the reaction was completed, the reaction solution was filtered to remove the solids in the system; the filtrate was washed three times with saturated saline, saturated sodium bicarbonate aqueous solution, and saturated saline, and then anhydrous sodium sulfate was added to the organic phase and allowed to stand overnight to remove water; after filtering to remove anhydrous sodium sulfate, rotary evaporation was performed, and column chromatography was used for purification, and the ratio of the chromatographic solution was petroleum ether: ethyl acetate = 10:1 (v / v). Finally, compound II was obtained.

[0024] The structural formula of compound B obtained in this example is

[0025]

[0026] Example 4

[0027] Specifically, 2-hydroxy-1-[4-[4-(2-hydroxy-2-methylpropionyl)phenoxy]phenyl]-2-methylpropanone (5mmol, 1.7119g) was added to a three-necked flask, followed by 80ml of dichloromethane, followed by triethylamine (TEA, 5mmol, 0.5024g), magnetic stirring was turned on, and stirring was continued for 30min; acryloyl chloride (AC, 5mmol, 0.4305g) was weighed, dissolved in 20ml of dichloromethane, and slowly added dropwise using a constant pressure funnel; the reaction was continued at room temperature for 2-4h. After the reaction was completed, the reaction solution was filtered to remove the solids in the system; the filtrate was washed three times with saturated saline, saturated sodium bicarbonate aqueous solution, and saturated saline, and then anhydrous sodium sulfate was added to the organic phase and allowed to stand overnight to remove water; after filtering to remove anhydrous sodium sulfate, rotary evaporation was performed, and column chromatography was used for purification, and the ratio of the chromatographic solution was petroleum ether: ethyl acetate = 10:1 (v / v). Finally, compound III was obtained.

[0028] The structural formula of compound C obtained in this example is

[0029]

[0030] Example 5

[0031] Specifically, 2-hydroxy-1-(4-(3-(hydroxymethyl)phenoxy)phenyl)-2-methyl-1-propanone (5mmol, 1.4317g) was added to a three-necked flask, followed by 80ml of dichloromethane, followed by triethylamine (TEA, 5mmol, 0.5024g), magnetic stirring was turned on, and stirring was continued for 30min; acryloyl chloride (AC, 5mmol, 0.4305g) was weighed, dissolved in 20ml of dichloromethane, and slowly added dropwise using a constant pressure funnel; the reaction was allowed to react for 2-4h at room temperature. After the reaction was completed, the reaction solution was filtered to remove the solids in the system; the filtrate was washed three times with saturated saline, saturated sodium bicarbonate aqueous solution, and saturated saline, and then anhydrous sodium sulfate was added to the organic phase and allowed to stand overnight to remove water; after filtering to remove anhydrous sodium sulfate, rotary evaporation was performed, and column chromatography was used for purification, and the ratio of the chromatographic liquid was petroleum ether: ethyl acetate = 10:1 (v / v). Finally, compound IV was obtained.

[0032] The structural formula of compound D obtained in this example is

[0033]

[0034] Example 6

[0035] Specifically, 2-hydroxy-1-(4-(4-hydroxyphenoxy)phenyl)-2-methyl-1-propanone (5mmol, 1.3615g) was added to a three-necked flask, followed by 80ml of dichloromethane, followed by triethylamine (TEA, 5mmol, 0.5024g), magnetic stirring was turned on, and stirring was continued for 30min; acryloyl chloride (AC, 5mmol, 0.4305g) was weighed, dissolved in 20ml of dichloromethane, and slowly added dropwise using a constant pressure funnel; the reaction was allowed to react for 2-4h at room temperature. After the reaction was completed, the reaction solution was filtered to remove the solids in the system; the filtrate was washed three times with saturated saline, saturated sodium bicarbonate aqueous solution, and saturated saline, and then anhydrous sodium sulfate was added to the organic phase and allowed to stand overnight to remove water; after filtering to remove anhydrous sodium sulfate, the mixture was rotary evaporated and purified using column chromatography, and the ratio of the chromatographic solution was petroleum ether: ethyl acetate = 10:1 (v / v). Finally, compound V was obtained.

[0036] The structural formula of compound E obtained in this example is

[0037]

[0038] Example 7

[0039] 2-Hydroxy-1-(4-(3-(hydroxymethyl)phenoxy)phenyl)-2-methyl-1-propanone (5mmol, 1.3615g) and 31.0mg dibutyltin dilaurate (DBTDL, 1.5% of the total mass) were added to a four-necked flask, 0.7057g of ethyl isocyanate acrylate and 15g of ethyl acetate were weighed and added to a constant pressure funnel, a condensation reflux device was installed on the four-necked flask, and cooling water was passed for condensation reflux. A magnetic stirring device was used during the reaction, and a thermometer was inserted below the liquid level of the flask to measure the temperature inside the system. The reaction system was heated by oil bath heating. When the internal temperature rose to 40°C, the ethyl isocyanate acrylate solution was dripped into the four-necked flask at a uniform speed (1-2 drops / s) using a constant pressure funnel. After the addition was completed, the reaction was carried out at a constant temperature for 3h.

[0040] The structural formula of compound F obtained in this example is

[0041]

[0042] Example 8

[0043] 2-Hydroxy-1-(4-(4-hydroxyphenoxy)phenyl)-2-methyl-1-propanone (5mmol, 1.4317g) and 33.1mg dibutyltin dilaurate (DBTDL, 1.5% of the total mass) were added to a four-necked flask, 0.7758g of ethyl isocyanate methacrylate and 15g of ethyl acetate were weighed and added to a constant pressure funnel, a condensation reflux device was installed on the four-necked flask, and cooling water was passed for condensation reflux. A magnetic stirring device was used during the reaction, and a thermometer was inserted below the liquid level of the flask to measure the temperature in the system. The reaction system was heated by oil bath heating. When the internal temperature rose to 40°C, the ethyl isocyanate methacrylate solution was dripped into the four-necked flask at a uniform speed (1-2 drops / s) using a constant pressure funnel. After the addition was completed, the reaction was carried out at a constant temperature for 3h.

[0044] The structural formula of compound G obtained in this example is

[0045]

[0046] Example 9

[0047] 1,1'-(methylenedi-4,1-phenylene)bis[2-hydroxy-2-methyl-1-propanone] (5mmol, 1.7021g), 57.3mg dibutyltin dilaurate (DBTDL, 1.5% of the total mass) were added to a four-necked flask, 2.1170g ethyl isocyanate acrylate and 30g ethyl acetate were weighed and added to a constant pressure funnel, a condensation reflux device was installed on the four-necked flask, and cooling water was passed for condensation reflux. A magnetic stirring device was used during the reaction, and a thermometer was inserted below the liquid level of the flask to measure the temperature in the system. The reaction system was heated by oil bath heating. When the internal temperature rose to 60°C, the ethyl isocyanate acrylate solution was dripped into the four-necked flask at a uniform speed (1-2 drops / s) using a constant pressure funnel. After the addition was completed, the reaction was kept at a constant temperature for 3h.

[0048] The structural formula of compound H obtained in this example is

[0049]

[0050] Example 10

[0051] 2-Hydroxy-1-(4-(4-hydroxybenzyl)phenyl)-2-methyl-1-propanone (5mmol, 1.3517g) and 52.0mg dibutyltin dilaurate (DBTDL, 1.5% of the total mass) were added to a four-necked flask, 2.1170g of ethyl isocyanate acrylate and 30g of ethyl acetate were weighed and added to a constant pressure funnel, a condensation reflux device was installed on the four-necked flask, and cooling water was passed for condensation reflux. A magnetic stirring device was used during the reaction, and a thermometer was inserted below the liquid level of the flask to measure the temperature in the system. The reaction system was heated by oil bath heating. When the internal temperature rose to 60°C, the ethyl isocyanate acrylate solution was dripped into the four-necked flask at a uniform speed (1-2 drops / s) using a constant pressure funnel. After the addition was completed, the reaction was carried out at a constant temperature for 3h.

[0052] The structural formula of compound I obtained in this example is

[0053]

[0054] Example 11

[0055] 2-Hydroxy-1-(4-(3-(hydroxymethyl)benzyl)phenyl)-2-methyl-1-propanone (5mmol, 1.4218g) and 53.1mg dibutyltin dilaurate (DBTDL, 1.5% of the total mass) were added to a four-necked flask, 2.1170g ethyl isocyanate acrylate and 30g ethyl acetate were weighed and added to a constant pressure funnel, a condensation reflux device was installed on the four-necked flask, and cooling water was passed for condensation reflux. A magnetic stirring device was used during the reaction, and a thermometer was inserted below the liquid level of the flask to measure the temperature in the system. The reaction system was heated by oil bath heating. When the internal temperature rose to 60°C, the ethyl isocyanate acrylate solution was dripped into the four-necked flask at a uniform speed (1-2 drops / s) using a constant pressure funnel. After the addition was completed, the reaction was carried out at a constant temperature for 3h.

[0056] The structural formula of compound J obtained in this example is

[0057]

[0058] Test Method

[0059] In the photoinitiator performance test, the preferred monomer is tripropylene glycol diacrylate (TPGDA), and the preferred photoinitiator concentration is 1.5 mol%. The photoinitiator kinetics are tested using a real-time infrared method, and the results are shown in Table 1;

[0060] In the crosslinking performance test, the preferred monomer is butyl acrylate (BA), and the preferred photoinitiator concentration is 2 mol%. The above-mentioned photocuring system is prepared in a sample bottle, and ultrasonicated in a dark place for 0.5 h to make it fully dissolved, and then cured in a nitrogen atmosphere for 4 min. After curing, it is inverted for 15 min. If the system flows, it is considered to have no crosslinking ability, and if the system does not flow, it is considered to be crosslinkable.

[0061] The preferred monomer for the mobility test is TPGDA, and the preferred photoinitiator concentration is 1.5 mol%. The photocured film is immersed in an acetonitrile solution for 3 days, and the concentration is tested by ultraviolet light.

[0062] The above tests use a mercury lamp or LED lamp as the light source, with a light intensity of 5-100mW / cm -2 The results are shown in Table 2.

[0063] Table 1: Photoinitiator performance, crosslinking ability, and mobility of example photoinitiators

[0064]

[0065]

[0066] Note: Conversion double bond conversion rate; R p(max) : Maximum polymerization rate; t (max): time required to reach the maximum polymerization rate; t (induction) : Induction period

[0067] From the test results, it can be seen that the photoinitiator proposed in the present invention has extremely high photoinitiating performance when used, and in this test, the monofunctional monomer can be cross-linked after polymerization, that is, the photoinitiator proposed in the present invention can act as a cross-linking agent in the photopolymerization system, fix itself to the polymer network, and thus have low mobility, which also explains the phenomenon of extremely low mobility of the photoinitiator in the example.

Claims

1. A cross-linkable α-hydroxyacetophenone photoinitiator, characterized in that There are two benzene ring structures, and one benzene ring has an α-hydroxyacetophenone structure, and the other benzene ring has a polymerizable carbon-carbon double bond structure. The general structural formula is as follows: R1 is one of a carbon bond, a methylene group, an oxygen atom, and a sulfur atom; R2 is selected from one of the following structures: R3 is a hydrogen atom or a methyl group.

2. A cross-linkable α-hydroxyacetophenone photoinitiator according to claim 1, characterized in that Can be used as UV photoinitiator.

3. A cross-linkable α-hydroxyacetophenone photoinitiator according to claim 1, characterized in that Can be used as a photopolymerization crosslinking agent.

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