Preparation and application of modified photoinitiator based on 2-hydroxy-2-methyl-1-phenyl-1-propanone

Abstract

The present invention relates to a modified photoinitiator based on 2-hydroxy-2-methyl-1-phenyl-1-acetone, which has high thermal stability and excellent migration stability and can be used to prepare PDMS membranes. The present invention also relates to a method for preparing the above-mentioned modified photoinitiator, which reacts alkyl chains of different lengths, namely hexyl isocyanate, dodecyl cyanate, and octadecyl isocyanate, with the hydroxyl group of 1173 photoinitiator through an isocyanate bond to introduce an alkyl group into the 1173 photoinitiator, thereby improving the thermal stability and migration stability of the photoinitiator. Through pervaporation testing, it was found that the PDMS membrane prepared with the modified photoinitiator has improved separation performance for butanol.

Description

Technical Field

[0001] The present invention belongs to the technical field of membrane separation, and in particular relates to a preparation method and application of a modified photoinitiator based on 2-hydroxy-2-methyl-1-phenyl-1-propanone. Background Art

[0002] Organic solvents are commonly used in manufacturing industries, such as chemical synthesis, semiconductor preparation, and drug synthesis. The recovery and reuse of organic solvents can effectively prevent water pollution, and recycled organic solvents emit less greenhouse gases than synthesizing new solvents. Reducing greenhouse gas emissions is one of the ways to alleviate global warming. As a common organic solvent, n-butanol is considered a promising biofuel due to its low volatility, low corrosiveness, high calorific value, and good compatibility with petroleum. However, n-butanol and water easily form azeotropes, and the traditional distillation recovery process consumes a lot of energy. Pervaporation, as a rapidly developing separation technology, has simple equipment, good separation effect, and excellent pollution resistance, and has great application potential in the separation process.

[0003] Traditional pervaporation separation membrane preparation methods rely on thermal crosslinking, making large-scale continuous production impossible and significantly polluting the environment. Photocuring, as a novel preparation method, offers extremely short curing times and enables continuous, green membrane preparation. The currently common photoinitiator, 2-hydroxy-2-methyl-1-phenyl-1-propanone (1173), decomposes at around 100°C. Under prolonged light exposure, the light energy causes the temperature to rise to extremely high levels, causing some of the photoinitiator 1173 to dissolve, leading to localized low content. Furthermore, the photoinitiator 1173 readily migrates into the solvent in the prepared membrane. This migrated photoinitiator poses a threat to the environment and personnel, and also reduces the content retained within the membrane. Therefore, low content within the membrane can easily lead to incomplete curing, posing a significant challenge to the compactness of the pervaporation membrane. This ultimately results in defects, loss of membrane separation performance, and extremely high biofuel production costs.

[0004] Therefore, it is crucial to prepare a photoinitiator with high thermal stability and excellent migration stability for the preparation of PDMS membranes. Summary of the Invention

[0005] The technical problem to be solved by the present invention is to provide a modified photoinitiator based on 2-hydroxy-2-methyl-1-phenyl-1-propanone to address the problems existing in the prior art. The modified photoinitiator has high thermal stability and excellent migration stability and can be used to prepare PDMS membranes.

[0006] The present invention also provides a method for preparing the modified photoinitiator based on 2-hydroxy-2-methyl-1-phenyl-1-propanone.

[0007] To this end, the first aspect of the present invention provides a modified photoinitiator based on 2-hydroxy-2-methyl-1-phenyl-1-propanone, the molecular structure of which is shown in formula (I):

[0008]

[0009] In formula (I), R includes one or more of n-hexyl, n-dodecyl and n-octadecyl.

[0010] The second aspect of the present invention provides a method for preparing a modified photoinitiator based on 2-hydroxy-2-methyl-1-phenyl-1-propanone as described in the first aspect of the present invention, which comprises reacting 2-hydroxy-2-methyl-1-phenyl-1-propanone with an alkyl isocyanate to prepare a modified photoinitiator based on 2-hydroxy-2-methyl-1-phenyl-1-propanone; wherein the alkyl isocyanate comprises one or more of hexyl isocyanate, dodecyl isocyanate and octadecyl isocyanate.

[0011] According to some embodiments of the present invention, the preparation method includes the step of preparing a modified photoinitiator, which includes adding a catalyst to an alkyl isocyanate solution in an argon atmosphere, and then dropwise adding 2-hydroxy-2-methyl-1-phenyl-1-propanone to obtain a crude modified photoinitiator.

[0012] In some embodiments of the present invention, in the step of preparing the modified photoinitiator, the alkyl isocyanate solution is formed by dissolving alkyl isocyanate in ethyl acetate; preferably, the concentration of the alkyl isocyanate solution is 1 mol / L.

[0013] In some embodiments of the present invention, in the step of preparing the modified photoinitiator, the molar ratio of the alkyl isocyanate to 2-hydroxy-2-methyl-1-phenyl-1-propanone is 1:1.

[0014] In some embodiments of the present invention, the molar ratio of the catalyst to the alkyl isocyanate is 1:150; preferably, the catalyst is dibutyltin dilaurate.

[0015] In some embodiments of the present invention, the reaction temperature is 50-100° C., preferably, the temperature is 75° C.; and the reaction time is 4 h.

[0016] According to some embodiments of the present invention, the preparation method further includes a step of separating and purifying the modified photoinitiator, which includes rinsing and dissolving the crude modified photoinitiator with a first solvent, removing the first solvent by rotary evaporation, and purifying the obtained solid product by recrystallization to obtain a pure modified photoinitiator.

[0017] In some embodiments of the present invention, the first solvent comprises ethyl acetate, and the second solvent used in the recrystallization method comprises n-hexane.

[0018] The third aspect of the present invention provides use of the modified photoinitiator according to the first aspect of the present invention or the modified photoinitiator according to the second aspect of the present invention in preparing a PDMS membrane.

[0019] The present invention introduces alkyl chains of different lengths, namely hexyl isocyanate, dodecyl isocyanate, and octadecyl isocyanate, into the hydroxyl group of the photoinitiator 1173 via an isocyanate bond to improve the thermal stability and migration stability of the photoinitiator. The pervaporation test found that the PDMS membrane prepared with the modified photoinitiator had an improved separation factor for butanol. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] The present invention will be further described in detail below with reference to the accompanying drawings:

[0021] Figure 1 The synthetic route of the modified initiator is shown.

[0022] Figure 2 The comparison results of Fourier transform infrared spectra of each monomer and initiator in Example 1 are shown.

[0023] Figure 3 The thermogravimetric analysis results of 1173, 6-methyl-1173, and 12-methyl-1173 are shown.

[0024] Figure 4 The migration percentages calculated for different photoinitiators in Example 1 are shown for precipitation in acetonitrile.

[0025] Figure 5 The reaction formula for preparing PDMS membrane material using the modified photoinitiator is shown.

[0026] Figure 6 Schematic diagram of the pervaporation device. DETAILED DESCRIPTION

[0027] To facilitate understanding of the present invention, the present invention will be described in detail below with reference to the accompanying drawings. However, before describing the present invention in detail, it should be understood that the present invention is not limited to the specific embodiments described. It should also be understood that the terminology used herein is for descriptive purposes only and is not intended to be limiting.

[0028] Unless otherwise defined, all terms used herein have the same meaning as commonly understood by those of ordinary skill in the art to which the present invention pertains. Although any methods and materials similar or equivalent to those described herein can also be used in the practice or testing of the present invention, preferred methods and materials are now described.

[0029] In the present invention, the so-called range of dosage concentration, temperature or other physical or chemical properties or characteristics covers or includes the upper limit and lower limit of the range unless otherwise specified.

[0030] I. Terminology

[0031] The term "N-methyl" as used herein represents an N-alkyl group, for example, (n-)hexyl, (n-)dodecyl, and (n-)octadecyl.

[0032] The term "1173" in the present invention refers to 1173 photoinitiator, namely 2-hydroxy-2-methyl-1-phenyl-1-propanone photoinitiator.

[0033] The term "PDMS" in the present invention refers to polydimethylsiloxane, which has the chemical formula (C2H6OSi) n , accordingly, the “PDMS membrane” refers to a polydimethylsiloxane membrane.

[0034] II. Implementation Plan

[0035] As mentioned above, the currently common photoinitiator 2-hydroxy-2-methyl-1-phenyl-1-propanone (1173) will decompose at around 100°C. The photoinitiator 1173 in the prepared film is easy to migrate into the solvent and is easily decomposed under long-term light exposure. In view of this, the present inventors have conducted extensive research on 2-hydroxy-2-methyl-1-phenyl-1-propanone (1173).

[0036] The present inventors have discovered that by modifying 2-hydroxy-2-methyl-1-phenyl-1-propanone with alkyl isocyanate, a modified photoinitiator based on 2-hydroxy-2-methyl-1-phenyl-1-propanone (1173) can be prepared. The modified photoinitiator has high thermal stability and excellent migration stability and can be used to prepare PDMS membranes.

[0037] Therefore, the molecular structure of the modified photoinitiator based on 2-hydroxy-2-methyl-1-phenyl-1-propanone involved in the first aspect of the present invention is shown in formula (I):

[0038]

[0039] In formula (I), R includes one or more of n-hexyl, n-dodecyl and n-octadecyl.

[0040] The modified photoinitiator based on 2-hydroxy-2-methyl-1-phenyl-1-propanone described in the present invention is also referred to as "modified photoinitiator 1173"; when R is n-hexyl, the modified photoinitiator 1173 is recorded as "6-methyl-1173", representing the 6-methyl-modified photoinitiator 1173; when R is n-dodecyl, the modified photoinitiator 1173 is recorded as "12-methyl-1173", representing the 12-methyl-modified photoinitiator 1173; when R is n-octadecyl, the modified photoinitiator 1173 is recorded as "18-methyl-1173", representing the 18-methyl-modified photoinitiator 1173.

[0041] In the second aspect of the present invention, the synthesis route of the modified photoinitiator based on 2-hydroxy-2-methyl-1-phenyl-1-propanone of the present invention is as shown in formula (I), from Figure 1 It can be seen that the preparation method of the modified photoinitiator based on 2-hydroxy-2-methyl-1-phenyl-1-propanone described in the first aspect of the present invention includes preparing a modified photoinitiator based on 2-hydroxy-2-methyl-1-phenyl-1-propanone (referred to as modified photoinitiator in the present invention) by reacting 2-hydroxy-2-methyl-1-phenyl-1-propanone with an alkyl isocyanate; wherein the alkyl isocyanate includes one or more of hexyl isocyanate, dodecyl isocyanate and octadecyl isocyanate.

[0042] Alkyl chains of different lengths were introduced into the initiator 1173 by reacting the hydroxyl group on 1173 with the isocyanate bond on hexyl isocyanate, dodecyl isocyanate or octadecyl isocyanate. The modified initiators 1173 are represented in this article as 6-methyl-1173, 12-methyl-1173 and 18-methyl-1173, respectively.

[0043] For example, when the alkyl isocyanate is hexyl isocyanate, when R is n-hexyl, the modified photoinitiator 1173 is recorded as "6-methyl-1173", which represents the 6-methyl modified photoinitiator 1173; when the alkyl isocyanate is dodecyl isocyanate, when R is n-dodecyl, the modified photoinitiator 1173 is recorded as "12-methyl-1173", which represents the 12-methyl modified photoinitiator 1173; when the alkyl isocyanate is octadecyl isocyanate, when R is n-octadecyl, the modified photoinitiator 1173 is recorded as "18-methyl-1173", which represents the 18-methyl modified photoinitiator 1173.

[0044] Specifically, the preparation method of the modified photoinitiator based on 2-hydroxy-2-methyl-1-phenyl-1-propanone includes:

[0045] (1) preparing a modified photoinitiator, comprising adding a catalyst to an alkyl isocyanate solution in an argon atmosphere, and then dropwise adding 2-hydroxy-2-methyl-1-phenyl-1-propanone to obtain a crude modified photoinitiator having the appearance of a white gel-like solid;

[0046] (2) The step of separating and purifying the modified photoinitiator comprises washing and dissolving the crude modified photoinitiator with the first solvent, removing the first solvent by rotary evaporation, and purifying the obtained gel-like solid product by recrystallization to obtain the pure modified photoinitiator.

[0047] In the above steps of preparing the modified photoinitiator:

[0048] (1) The alkyl isocyanate solution is formed by dissolving alkyl isocyanate in ethyl acetate; preferably, the concentration of the alkyl isocyanate solution is 1 mol / L.

[0049] (2) The molar ratio of the alkyl isocyanate to 2-hydroxy-2-methyl-1-phenyl-1-propanone is 1:1.

[0050] (3) The molar ratio of the catalyst to the alkyl isocyanate is 1:150; preferably, the catalyst is dibutyltin dilaurate.

[0051] (4) The reaction temperature is 50-100°C, preferably 75°C; the reaction time is 4 hours.

[0052] In the step of separating and purifying the modified photoinitiator, the first solvent includes ethyl acetate, and the second solvent used in the recrystallization method includes n-hexane.

[0053] The third aspect of the present invention involves the use of the modified photoinitiator as described in the first aspect of the present invention or the modified photoinitiator prepared by the preparation method as described in the second aspect of the present invention in the preparation of PDMS membrane, which can be understood as a method for preparing a PDMS membrane using the modified photoinitiator as described in the first aspect of the present invention or the modified photoinitiator prepared by the preparation method as described in the second aspect of the present invention.

[0054] The reaction formula for preparing PDMS membrane material using modified photoinitiator 1173 is as follows: Figure 5 shown.

[0055] III. Examples

[0056] The present invention is described in detail below through specific examples. The experimental methods described below, unless otherwise specified, are all routine laboratory methods. The experimental materials described below, unless otherwise specified, can all be obtained from commercial channels.

[0057] Example 1: 1173 modification

[0058] (1) Synthesis of 6-methyl-1173: 0.03 mol of hexyl isocyanate was added to 30 ml of ethyl acetate (solvent I), followed by 0.12 g of dibutyltin dilaurate. 0.03 mol of 2-hydroxy-2-methyl-1-phenyl-1-propanone (1173) photoinitiator was added dropwise under the condition of heating in an oil bath at 75°C. The reaction was allowed to proceed for a total of 4 hours, while maintaining an argon atmosphere. A white liquid was obtained, and the solvent I (ethyl acetate) was removed by rotary evaporation to obtain a white gel-like solid. The obtained gel-like solid product was purified by recrystallization from n-hexane (solvent II).

[0059] (2) Synthesis of 12-methyl-1173: 0.03 mol of dodecyl isocyanate was added to 30 ml of ethyl acetate (solvent I), followed by 0.12 g of dibutyltin dilaurate. 0.03 mol of 2-hydroxy-2-methyl-1-phenyl-1-propanone (1173) photoinitiator was added dropwise under the condition of heating in an oil bath at 75°C. The reaction was continued for a total of 4 hours under an argon atmosphere. A white gel-like solid was obtained. The solvent I (ethyl acetate) was removed by rotary evaporation to obtain a white gel-like solid. The obtained gel-like solid product was purified by recrystallization from n-hexane (solvent II).

[0060] (3) Synthesis of 18-methyl-1173: 0.03 mol of octadecyl isocyanate was added to 30 ml of ethyl acetate (solvent I), followed by 0.12 g of dibutyltin dilaurate. 0.03 mol of 2-hydroxy-2-methyl-1-phenyl-1-propanone (1173) photoinitiator was added dropwise under the condition of heating in an oil bath at 75°C. The reaction was continued for 4 hours under an argon atmosphere. A white gel-like solid was obtained. The solvent I (ethyl acetate) was removed by rotary evaporation to obtain a white gel-like solid. The obtained gel-like solid product was purified by recrystallization from n-hexane (solvent II).

[0061] Alkyl chains of varying lengths were introduced into the 1173 initiator by reacting the hydroxyl group on the 1173 with the isocyanate bonds on hexyl isocyanate, dodecyl isocyanate, and octadecyl isocyanate. The modified initiators are represented herein as 6-methyl-1173, 12-methyl-1173, and 18-methyl-1173, respectively.

[0062] The successfully synthesized photoinitiator was characterized by Fourier infrared (instrument manufacturer: Thermo Scientific, model: Nicolet 8700), and the test results were as follows: Figure 2 As shown; Figure 2The weakening or even disappearance of the -NCO peak and the appearance of the -NH bond peak prove the successful combination of the hydroxyl group on 1173 and the isocyanate bond on the alkyl isocyanate monomer, further illustrating the successful synthesis of the modified initiator.

[0063] The thermal stability of the above-mentioned photoinitiator was tested by thermogravimetric analysis using a synchronous thermal analyzer (NETZSCH STA 449F3, NETZSCH). The test conditions were nitrogen atmosphere, temperature range 40-600℃, heating rate 10℃ / min, and the thermal stability results were as follows: Figure 3 shown.

[0064] from Figure 3 It can be seen that the 1173 photoinitiator begins to decompose at less than 100°C, the modified photoinitiator 6-methyl-1173 begins to decompose at 150-200°C, and the temperature at which 12-methyl-1173 begins to decompose is higher than 200°C. As the alkyl chain grows, the temperature at which the initiator begins to decompose increases.

[0065] Small molecule initiators often migrate easily from the membrane, causing damage to the human body and the environment. The migration rate of the photoinitiator was measured using a UV-visible spectrophotometer (UV1700PC, Shanghai Aoxi Scientific Instrument Co., Ltd.). To calculate the specific migration amount, the following calculation was performed:

[0066] The migration mass of the initiator is calculated according to formula 1:

[0067]

[0068] Wherein, M is the relative molecular mass of the photoinitiator, A is the maximum absorption value of the ultraviolet absorption spectrum, ε is the molar extinction coefficient at the maximum absorption peak of the photoinitiator, and l is the optical path length.

[0069] The calculation of ε is based on formula 2:

[0070] A=cεl(2)

[0071] Where A is the maximum absorption wavelength of different initiators, c is the initiator concentration, ε is the molar extinction coefficient at the maximum absorption peak of the photoinitiator, and l is the optical path length.

[0072] After calculating the mass of the migrating initiator, the initiator migration percentage is calculated according to Formula 3.

[0073]

[0074] Calculate the migration percentage of each initiator as Figure 4 shown.

[0075] from Figure 4It can be seen that the mobility of the modified photoinitiators is lower than that of the 1173 photoinitiator, and the mobility decreases continuously with the growth of the alkyl chain, which proves the effectiveness of initiator modification on mobility degradation.

[0076] Example 2:

[0077] (1) Preparation of a casting solution: The modified initiator prepared in Example 1 was added to ethyl acetate, followed by 4 g of polydimethylsiloxane (PDMS), with the modified initiator accounting for 5 wt% of the total system. The casting solution was stirred in the dark for a period of time, and then vacuumed to remove any bubbles from the solution.

[0078] (2) Scraping: Pour the degassed casting solution onto the PVDF base film and scrape the film with a scraper. Adjust the scraper thickness to 10-40 μm to obtain a liquid film layer.

[0079] (3) Curing: Transfer the liquid film layer to a UV lamp for 2-5 minutes to obtain a PDMS film with a solid surface.

[0080] (4) Pervaporation test: The obtained cured membrane was heated at 60° C. and the separation performance of 1.5 wt % butanol was tested using a pervaporation device.

[0081] The pervaporation performance of butanol was tested using laboratory-made equipment at a test temperature of 60°C and a butanol liquid concentration of 1.5 wt%. Figure 6 shown.

[0082] Pervaporation performance of initiators modified with different alkyl chain lengths (all at 5 wt% initiator content): At the same mass fraction, increasing the alkyl chain length of the modified initiator improves the separation factor, but the flux decreases slightly due to a "synergistic effect." This decrease in flux can be explained by the fact that as the length of the grafted alkyl chain on photoinitiator 1173 increases, its migration stability increases, reducing the amount of photoinitiator migrating to the membrane surface and increasing the number of photoinitiator molecules remaining within the membrane to participate in the curing reaction, resulting in a more rigid membrane structure and a decrease in flux. Increasing the alkyl chain length of the modified initiator also increases the butanol concentration on the permeate side. This phenomenon can be explained by the fact that increasing the alkyl chain length of the modified initiator increases its thermal stability. As a result, the number of photoinitiators that are inactivated by light decreases, while the number of photoinitiator molecules participating in the curing reaction increases, resulting in a denser membrane. Due to the "size exclusion effect," water molecules are excluded from the membrane channels, improving the membrane's separation performance and increasing the butanol concentration on the permeate side and the membrane's selectivity for butanol.

[0083] Comparative Example 1:

[0084] (1) Preparation of casting solution: Add 1173 photoinitiator to ethyl acetate, then add 4g PDMS, with the mass ratio of 1173 photoinitiator to the whole system being 5wt%. After stirring for a period of time in the dark, vacuum is applied to remove bubbles in the casting solution.

[0085] (2) Scraping: Pour the degassed casting solution onto the PVDF base film and scrape the film with a scraper. Adjust the scraper thickness to 10-40 μm to obtain a liquid film layer.

[0086] (3) Curing: Transfer the liquid film layer to a UV lamp for 2-5 minutes to obtain a PDMS film with a solid surface.

[0087] (3) Pervaporation test: The obtained cured membrane was heated at 60° C. and tested for separation performance of 1.5 wt % butanol using a pervaporation device.

[0088] From the above, it can be seen that the modified photoinitiator provided by the present invention has better thermal stability than 1173 and has a smaller mobility, indicating that it has better migration stability. In addition, the permeation flux of the PDMS membrane obtained in the embodiment at a certain temperature is 818.01-1396.44gm -2 h -1 , with a separation factor of 37.8-54.1. Test results show that the modified initiator-cured PDMS membrane improves the butanol separation factor, permeate butanol concentration, and butanol selectivity. With the growth of grafted alkyl chains, the pervaporation separation factor increases by 46% compared to the control, and the permeate concentration increases by 22%.

[0089] It should be noted that the embodiments described above are only preferred embodiments of the present invention and are used to explain the present invention and do not constitute any limitation to the present invention. The present invention has been described with reference to typical embodiments, but it should be understood that the words used therein are descriptive and explanatory words, rather than restrictive words. The present invention may be modified as specified within the scope of the claims of the present invention, and the present invention may be revised without departing from the scope and spirit of the present invention. Although the present invention described therein relates to specific methods, materials and embodiments, it does not mean that the present invention is limited to the specific examples disclosed therein. On the contrary, the present invention can be extended to all other methods and applications with the same function.

Claims

1. A modified photoinitiator based on 2-hydroxy-2-methyl-1-phenyl-1-propanone, whose molecular structure is shown in formula (I): ； In formula (I), R is n-octadecyl.

2. A method for preparing a modified photoinitiator based on 2-hydroxy-2-methyl-1-phenyl-1-propanone as claimed in claim 1, comprising reacting 2-hydroxy-2-methyl-1-phenyl-1-propanone with an alkyl isocyanate to prepare the modified photoinitiator based on 2-hydroxy-2-methyl-1-phenyl-1-propanone; wherein: The alkyl isocyanate is octadecyl isocyanate; The preparation method includes the steps of preparing a modified photoinitiator, which includes adding a catalyst to an alkyl isocyanate solution in an argon atmosphere, and then dropwise adding 2-hydroxy-2-methyl-1-phenyl-1-propanone to obtain a crude modified photoinitiator; The concentration of the alkyl isocyanate solution is 1 mol / L; The molar ratio of the catalyst to the alkyl isocyanate is 1:150; The reaction temperature is 75° C. and the reaction time is 4 hours.

3. The preparation method according to claim 2, characterized in that In the step of preparing the modified photoinitiator, the alkyl isocyanate solution is formed by dissolving alkyl isocyanate in ethyl acetate.

4. The preparation method according to claim 2, characterized in that In the step of preparing the modified photoinitiator, the molar ratio of the alkyl isocyanate to 2-hydroxy-2-methyl-1-phenyl-1-propanone is 1:1; and the catalyst is dibutyltin dilaurate.

5. The preparation method according to any one of claims 2 to 4, characterized in that The preparation method also includes the step of separating and purifying the modified photoinitiator, which includes dissolving the crude modified photoinitiator with the first solvent, removing the first solvent by rotary evaporation, and purifying the obtained solid product by recrystallization to obtain a pure modified photoinitiator.

6. The preparation method according to claim 5, characterized in that The first solvent includes ethyl acetate, and the second solvent used in the recrystallization method includes n-hexane.

7. Use of the modified photoinitiator according to claim 1 or the modified photoinitiator prepared by the preparation method according to any one of claims 2 to 6 in the preparation of PDMS membrane.

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