Synthesis method of hindered amine light stabilizer and application of hindered amine light stabilizer in preparation of membrane material

Abstract

The invention provides a synthesis method of a hindered amine light stabilizer and application of the hindered amine light stabilizer in preparation of a membrane material. The light stabilizer has a structure. The invention also provides a preparation method and application of the light stabilizer. The light stabilizer is simple in synthetic route, green and pollution-free, and can effectively solve the problem that the performance index of the membrane is reduced after long-time storage as an additive in the formula of the reverse osmosis membrane, and the storage time of the membrane is prolonged.

Description

Technical Field

[0001] This invention belongs to the field of organic synthesis, specifically relating to a method for synthesizing a hindered amine light stabilizer and its application in membrane material preparation. Background Technology

[0002] Ultraviolet (UV) radiation from sunlight is the primary cause of aging in polymer materials. Although UV radiation accounts for only about 5% of sunlight, it has a significant energy content. When polymer products absorb UV radiation, it is sufficient to trigger polymer self-oxidation and degradation, break the polymer's chemical bonds, causing them to break and cross-link. This leads to deterioration in the appearance and physical and mechanical properties of the polymer products, resulting in reduced strength and shortened lifespan.

[0003] Light stabilizers are additives used in polymer products (such as plastics, rubber, coatings, and synthetic fibers). They can shield or absorb the energy of ultraviolet rays, quench singlet oxygen, and decompose hydrogen peroxide into inactive substances. These functions enable polymers to eliminate or slow down the possibility of photochemical reactions under light radiation, and prevent or delay the photoaging process, thereby extending the service life of polymer products.

[0004] These types of light stabilizers can capture reactive free radicals generated in polymers, thereby inhibiting photo-oxidation processes and achieving photostability. Hindered amine light stabilizers (HALS) are a promising class of light stabilizers, with an average annual demand growth rate of 20% to 30% internationally.

[0005] For example, the ammonolysis synthesis route of acyl chloride mentioned in CN103508938B and the ammonolysis synthesis route of ester through nickel in CN107382828B; the use of acyl chloride and metal will lead to complicated post-processing, generate a large amount of wastewater, cause great environmental pollution, make pollution control difficult, and have poor long-term stability of performance indicators.

[0006] In summary, there is an urgent need in this field for a simple synthetic route that avoids the use of acyl chlorides and metal catalysts, and can effectively solve the problem of performance degradation of membranes after long-term storage, thereby extending the storage time of membranes. Summary of the Invention

[0007] To address the aforementioned technical problems, one of the objectives of this application is to provide a hindered amine light stabilizer. This light stabilizer has a simple and environmentally friendly synthesis route and can be used as an additive in reverse osmosis membrane formulations to effectively solve the problem of membrane performance degradation after long-term storage and extend the membrane's storage time.

[0008] To achieve the above-mentioned objectives, the present invention adopts the following technical solution:

[0009] A hindered amine light stabilizer having a structure as shown in formula (iii):

[0010]

[0011] Another object of the present invention is to provide a method for preparing hindered amine light stabilizers.

[0012] A method for preparing the above-mentioned hindered amine light stabilizer, the method comprising: reacting compound (i) and compound (ii) to obtain compound (iii):

[0013]

[0014] R1 and R2 are alkyl groups from C1 to C6, respectively.

[0015] In one embodiment of the present invention, the molar ratio of compound (i) to compound (ii) is 1:2-3.

[0016] In one embodiment of the present invention, the method is carried out in an organic solvent; preferably, the organic solvent is a polar organic solvent, more preferably one or more of methanol, acetonitrile, and N,N-dimethylformamide, and more preferably methanol. The reagents are commonly used in the art.

[0017] In one embodiment of the present invention, the reaction temperature in the method is 100-130°C, preferably 115-120°C.

[0018] In one embodiment of the present invention, the method involves extraction, drying, precipitation, and filtration after the reaction to obtain the product.

[0019] In this invention, the extraction solvent is a polar organic solvent, preferably one or more of ethyl acetate, dichloromethane, and petroleum ether, with dichloromethane being the most preferred. The reagents are commonly used in the art.

[0020] In this invention, the desiccant is a chemical desiccant, preferably one or more of anhydrous sodium sulfate, anhydrous calcium chloride, and anhydrous magnesium sulfate, with anhydrous sodium sulfate being the most preferred. The reagents are commonly used in the art.

[0021] In this invention, the precipitation solvent is an ether-based organic solvent, preferably one or more of diethyl ether, isopropyl ether, and petroleum ether, more preferably diethyl ether. The reagents are commonly used in the art.

[0022] In this invention, the addition of this light-stabilizing agent effectively enhances the antioxidant performance of the membrane. The presence of the pyridine ring matrix ensures the forward and complete reaction, thereby guaranteeing that important indicators such as water flux and desalination rate of the membrane do not change significantly after long-term storage or use. The hindered amine additive with the pyridine ring as the matrix can serve as an effective acid-binding agent in the production of polyamide membranes, absorbing acids generated during the reaction and reducing their impact on the reaction equilibrium. Simultaneously, the hindered amine functional group belongs to the alicyclic amine structure, which, after absorbing light energy in an aerobic state, can be converted into nitroxide radicals (NO·). These nitroxide radicals not only capture alkyl reactive radicals generated during the photo-oxidative degradation of polymer materials but also have a regenerative function during the light stabilization process, thereby inhibiting chain reactions and achieving the protective purpose.

[0023]

[0024] Another object of the present invention is to provide the use of a hindered amine light stabilizer.

[0025] Use of a hindered amine light stabilizer, wherein the light stabilizer is the light stabilizer described above or the light stabilizer prepared by the above method, and the light stabilizer is used in the fields of plastics, rubber, coatings, synthetic fibers, and reverse osmosis membranes, preferably in the field of reverse osmosis membranes.

[0026] Another object of the present invention is to provide a reverse osmosis membrane.

[0027] A reverse osmosis membrane, wherein the reverse osmosis membrane uses the light stabilizer described above, or a light stabilizer prepared by the method described above, wherein the reverse osmosis membrane is one or more of a low-pressure reverse osmosis membrane, a high-flux reverse osmosis membrane, and an anti-fouling reverse osmosis membrane, preferably a low-pressure reverse osmosis membrane; preferably, the amount of hindered amine light stabilizer added to the reverse osmosis membrane is 0.01-0.1 wt%, more preferably 0.02-0.04 wt%, based on the mass of the oil phase solvent.

[0028] In one embodiment of the present invention, the method for preparing a reverse osmosis membrane as described below is preferred. The method includes adding an appropriate amount of formula (iii). A hindered amine light stabilizer is prepared by adjusting the aqueous phase concentration according to the formula, followed by interfacial polymerization and post-treatment on a base film to obtain a film. The oil phase solvent includes one or a mixture of any of n-decane, n-heptane, and n-hexane, preferably n-decane. The oil phase solute is tribenzoyl chloride with a concentration of 0.1%-0.2%. The oil phase solute is m-phenylenediamine with a concentration of 1%-2%. The amount of hindered amine light stabilizer of formula (iii) added is 0.02wt%-0.04wt%. The post-treatment is oven curing to form a film at a temperature of 20-30℃ for 3-8 minutes. The light irradiation wavelength is 300-380 nm.

[0029] Compared with the prior art, the present invention has the following positive effects:

[0030] (1) The synthetic route is simple and no metal catalyst is used;

[0031] (2) The nitrogen oxide free radicals generated by the multi-site hindered amine conversion can effectively degrade alkane free radicals in polymer materials, have a significant anti-photooxidation effect, and can also act as an acid binder to effectively absorb the hydrochloric acid generated in the reaction and promote the positive progress of the interfacial reaction. Attached Figure Description

[0032] Figure 1 This is the 1H NMR spectrum of the hindered amine light stabilizer compound of formula (iii) in Example 1 of this invention;

[0033] Figure 2 This is the carbon NMR spectrum of the hindered amine light stabilizer compound of formula (iii) in Example 1 of this invention. Detailed Implementation

[0034] The present invention will be described in detail below through specific embodiments. However, the uses and purposes of these exemplary embodiments are only for illustrating the present invention and do not constitute any limitation on the actual protection scope of the present invention, nor are they intended to limit the protection scope of the present invention to these embodiments.

[0035]

[0036] Equipment Information Model / Manufacturer 1H NMR spectrum AM-400 (400MHz) / Bruker Carbon NMR Spectroscopy AM-400(100MHZ) / Bruker Pressure-resistant pipe 100ml / 15#

[0037] Example 1

[0038] At room temperature, 20 ml of methanol, 10 mmol of dimethyl 2,6-pyridinedicarboxylate and 25 mmol of 2,2,6,6-tetramethylpiperidineamine were added to a pressure-resistant tube. The pressure-resistant tube was then purged with nitrogen, and the temperature was raised to 115 °C with stirring. The reaction was continued at this temperature for 13 hours with stirring.

[0039] After the reaction was completed, the mixture was extracted with 10 ml of dichloromethane, dried over anhydrous sodium sulfate, concentrated under reduced pressure using a rotary evaporator, and precipitated with 20 ml of diethyl ether to obtain compound (iii) as a white solid, i.e., the hindered amine light stabilizer. Its characterization data are as follows (see attached graphs). Figure 1 and Figure 2 ):

[0040] 1HNMR (400MHz, CDCl3) δ8.35(d,J=7.8Hz,2H),8.02(t,J=7.8Hz,1H),7.45(d,J=8.3Hz,2H),4.48(m,J =12.2,8.0,3.8Hz,2H),1.99(dd,J=12.5,3.8Hz,4H),1.28(s,12H),1.14(s,12H),1.13–1.09(m,4H). 13 CNMR (101MHz, CDCl3) δ162.80,149.12,139.16,125.23,51.21,45.14,43.06,35.09,28.79,22.96.

[0041] Example 2

[0042] At room temperature, 40 ml of methanol, 20 mmol of dimethyl 2,6-pyridinedicarboxylate and 58 mmol of 2,2,6,6-tetramethylpiperidineamine were added to a pressure-resistant tube. The pressure-resistant tube was then purged with nitrogen, and the temperature was raised to 115 °C with stirring. The reaction was continued at this temperature for 13 hours with stirring.

[0043] After the reaction was completed, the product was extracted with 20 ml of dichloromethane, dried with anhydrous sodium sulfate, concentrated under reduced pressure by rotary evaporation, and precipitated with 40 ml of diethyl ether to obtain compound (iii) as a white solid, namely the hindered amine light stabilizer, with a yield of 54%.

[0044] Example 3

[0045] At room temperature, 40 ml of acetonitrile, 20 mmol of dibutyl 2,6-pyridinedicarboxylate and 58 mmol of 2,2,6,6-tetramethylpiperidineamine were added to a pressure-resistant tube. The pressure-resistant tube was then purged with nitrogen, and the temperature was raised to 115 °C with stirring. The reaction was continued at this temperature for 12 hours with stirring.

[0046] After the reaction was completed, the product was extracted with 20 ml of dichloromethane, dried over anhydrous sodium sulfate, concentrated under reduced pressure using a rotary evaporator, and precipitated with 40 ml of diethyl ether to obtain a white solid compound of formula (iii).

[0047] Example 4

[0048] At room temperature, 40 ml of acetonitrile, 20 mmol of methylpropylpyridine-2,6-dicarboxylate and 58 mmol of 2,2,6,6-tetramethylpiperidineamine were added to a pressure-resistant tube. The pressure-resistant tube was then purged with nitrogen, and the temperature was raised to 115 °C with stirring. The reaction was continued at this temperature for 13 hours with stirring.

[0049] After the reaction was completed, the product was extracted with 20 ml of dichloromethane, dried over anhydrous sodium sulfate, concentrated under reduced pressure using a rotary evaporator, and precipitated with 40 ml of diethyl ether to obtain a white solid compound of formula (iii).

[0050] Example 5

[0051] A pre-prepared solution of 3 wt% m-phenylenediamine aqueous phase and 0.09 wt% trimesoyl chloride n-decane oil phase (containing 0.03 wt% light stabilizer prepared in Example 1) was used. The polysulfone porous support layer used in the experiment was the base film. The base film was fixed in the prepared mold and immersed in the aqueous phase solution for 5 seconds. After the remaining solution was poured out, the water on the film surface was dried. The pre-prepared oil phase solution was poured onto the film surface of the mold, and interfacial polymerization was carried out at room temperature for 1 minute. After the reaction was completed, the film surface was dried and placed in a 27°C oven for 5 minutes to obtain film 1.

[0052] Example 6

[0053] A pre-prepared solution of 3 wt% m-phenylenediamine aqueous phase and 0.09 wt% trimesoyl chloride n-decane oil phase (containing 0.03 wt% light stabilizer prepared in Example 3) was used. The polysulfone porous support layer used in the experiment was the base film. The base film was fixed in the prepared mold and immersed in the aqueous phase solution for 5 seconds. After pouring out the remaining solution, the water on the film surface was dried. The pre-prepared oil phase solution was poured onto the film surface of the mold, and interfacial polymerization was carried out at room temperature for 1 minute. After the reaction was completed, the film surface was dried and placed in a 27°C oven for 5 minutes to obtain film 2.

[0054] Example 7

[0055] A pre-prepared solution of 3 wt% m-phenylenediamine aqueous phase and 0.09 wt% trimesoyl chloride n-decane oil phase (containing 0.08 wt% light stabilizer prepared in Example 4) was used. The polysulfone porous support layer used in the experiment was the base film. The base film was fixed in the prepared mold and immersed in the aqueous phase solution for 5 seconds. After the remaining solution was poured out, the water on the film surface was dried. The pre-prepared oil phase solution was poured onto the film surface of the mold, and interfacial polymerization was carried out at room temperature for 1 minute. After the reaction was completed, the film surface was dried and placed in a 27°C oven for 5 minutes to obtain film 3.

[0056] Comparative Example 1

[0057] Compared with Example 5, the only difference is the replacement of the light stabilizer. After the reaction was completed, membrane 4 was obtained.

[0058] Comparative Example 2

[0059] Compared with Example 5, the only difference is that the light stabilizer is replaced with benzophenone, and the reaction produces film 5.

[0060]

[0061]

[0062] Comparison results of membranes 1, 4, and 5: Compared with membrane 1, membranes 4 and 5, which contain other types of light stabilizers, showed greater changes in water flux and desalination rate after 15 days of rest. This indicates that the light stabilizers involved in this invention can effectively solve the problem of unprocessable hydrochloric acid generated during the interfacial reaction, promote the forward reaction, and thus improve membrane performance.

[0063] It is readily understood that the above embodiments are merely illustrative examples for clear explanation and do not imply that the invention is limited thereto. Those skilled in the art will recognize that other variations or modifications can be made based on the above description. It is neither necessary nor possible to exhaustively list all possible implementations here. However, obvious variations or modifications derived therefrom are still within the scope of protection of this invention.

Claims

1. A hindered amine light stabilizer, characterized in that, The light stabilizer has a structure as shown in formula (iii):

2. A method for preparing the hindered amine light stabilizer according to claim 1, characterized in that, The method is as follows: reacting compound (i) and compound (ii) to obtain compound (iii): R1 and R2 are alkyl groups from C1 to C6, respectively.

3. The method according to claim 2, characterized in that, In the method, the molar ratio of compound (i) to compound (ii) is 1:2-3; And / or, the method is carried out in an organic solvent; Preferably, the organic solvent is a polar organic solvent, preferably one or more of methanol, acetonitrile, and N,N-dimethylformamide, more preferably methanol; And / or, the reaction temperature in the method is 100-130°C, preferably 115-120°C; And / or, in the method, the product is obtained by extraction, drying, precipitation and filtration after the reaction.

4. Use of a hindered amine light stabilizer, wherein the light stabilizer is the light stabilizer according to claim 1, or the light stabilizer prepared by the method according to claim 2 or 3, and the light stabilizer is used in the fields of plastics, rubber, coatings, synthetic fibers, and reverse osmosis membranes, preferably in the field of reverse osmosis membranes.

5. A reverse osmosis membrane, wherein the reverse osmosis membrane uses the light stabilizer described in claim 1, or the light stabilizer prepared by the method described in claim 2 or 3, wherein the reverse osmosis membrane is one or more of a low-pressure reverse osmosis membrane, a high-flux reverse osmosis membrane, and an anti-fouling reverse osmosis membrane, preferably a low-pressure reverse osmosis membrane; Preferably, the amount of hindered amine light stabilizer added to the reverse osmosis membrane is 0.01-0.1 wt%, more preferably 0.02-0.04 wt%, based on the mass of the oil phase solvent.

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