Low-alkalinity hindered amine light stabilizer as well as preparation method and application thereof

Abstract

The invention provides a low-alkalinity hindered amine light stabilizer as well as a preparation method and application thereof, and relates to the field of light stabilizers. The preparation method of the low-alkalinity hindered amine light stabilizer comprises the following steps: by taking dibasic acid dimethyl ester and 1, 2, 2, 6, 6-pentamethylpiperidinol as raw materials and an alkane solvent or a benzene solvent as a solvent, carrying out heating reaction in the presence of a catalyst to obtain a catalytic reaction solution; and neutralizing and washing the catalytic reaction liquid to obtain the low-alkalinity hindered amine light stabilizer. According to the preparation method of the low-alkalinity hindered amine light stabilizer, a decolorizing agent and the like do not need to be adopted for decolorizing treatment, ideal preparation effects (such as purity, yield and the like) are obtained, meanwhile, the chromaticity of the product is effectively reduced, and the problem that the product is prone to yellowing due to the fact that the hindered amine light stabilizer absorbs visible light is solved.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of light stabilizers, in particular to a low-alkaline hindered amine light stabilizer, a preparation method and applications. BACKGROUND

[0002] Light stabilizers are a class of compounds that can effectively inhibit photo-induced degradation physical and chemical processes, and are usually used as additives for polymer products (such as plastics, rubbers, paints, synthetic fibers, etc.). Light stabilizers can be mainly divided into: light shielding agents (such as carbon black, titanium dioxide, zinc oxide), ultraviolet absorbers (benzotriazole, benzophenone, triazine, salicylate), quenching agents (nickel organic complex), free radical trapping agents (mainly hindered amines) and the like according to the mechanism of action.

[0003] Among them, the hindered amine light stabilizer (HALS) has the advantages of small toxicity, large molecular weight and not easy to migrate, excellent light stabilizing performance and not easy to color, etc., and is widely used in the processing and preparation of plastic agricultural films, automobiles, plastic products and other polymer materials. In response to the problems of easy aging and cracking, performance reduction, dark color and the like in the use process of traditional polymer materials, the hindered amine light stabilizer exhibits excellent anti-aging, anti-extraction, low-volatility and anti-migration properties. The hindered amine light stabilizer has broad application prospects, and the demand is increasing year by year.

[0004] However, the conventional hindered amine light stabilizer (HALS) usually has obvious alkalinity, and the reason is that there is an N-H group on the piperidine ring; the alkalinity of the hindered amine light stabilizer leads to a significant antagonistic effect with acidic additives in acidic application scenarios (such as acidic resins, acidic complexing agents, etc.), directly affecting its application performance, and severely limiting the application range of the hindered amine light stabilizer. Low alkalinity is an important development direction of the hindered amine light stabilizer.

[0005] The low-alkaline hindered amine light stabilizer and its preparation method disclosed in the prior art have poor platinum-cobalt color, which directly affects the color of the product and is not conducive to its application in color-sensitive material fields (such as transparent plastics, optical materials); the prior art also discloses a technology of using a decolorizing agent to decolorize the crude hindered amine light stabilizer, but the decolorizing operation is complicated, the production efficiency is low, and the comprehensive cost of the decolorizing agent and its waste is high. Moreover, the existing low-alkaline hindered amine light stabilizer also has the problem of yellowing of the product due to absorption of visible light, which further limits the popularization and application of the low-alkaline hindered amine light stabilizer.

[0006] Therefore, a preparation method of a low-alkaline hindered amine light stabilizer is provided, which does not need to use a decolorizing agent for decolorizing treatment, effectively reduces the color of the product while obtaining ideal preparation effects (such as purity, yield, etc.), and overcomes the problem of yellowing of the product due to absorption of visible light by the hindered amine light stabilizer, which has important technical significance and research value. Summary of the Invention

[0007] To address the technical problems existing in the prior art, this invention provides a low-alkalinity hindered amine light stabilizer, its preparation method, and its application. It eliminates the need for decolorization treatment using decolorizing agents, effectively reduces product color while achieving ideal preparation results (such as purity and yield), and overcomes the problem that hindered amine light stabilizers cause products to yellow easily due to the absorption of visible light.

[0008] To solve the above technical problems, the technical solution adopted by the present invention is as follows: A method for preparing a low-alkalinity hindered amine light stabilizer involves using dimethyl diacid and 1,2,2,6,6-pentamethylpiperidinol as raw materials, and alkane solvents or benzene solvents as solvents. The reaction is carried out under catalytic conditions in an inert gas environment at a temperature of 100-150°C to obtain a catalytic reaction solution. The catalytic reaction solution is then neutralized and washed to obtain the low-alkalinity hindered amine light stabilizer. The dimethyl dicarboxylic acid is at least one of the following: dimethyl oxalate, dimethyl malonate, dimethyl succinate, dimethyl glutarate, dimethyl adipate, dimethyl heptaate, dimethyl octanoate, and dimethyl azelaate.

[0009] Preferably, the molar ratio of the dimethyl diacid to 1,2,2,6,6-pentamethylpiperidinol is 1:1-3.

[0010] Preferably, the volume of the solvent is 1-3 times the total volume of dimethyl dicarboxylate and 1,2,2,6,6-pentamethylpiperidinol.

[0011] Furthermore, the catalyst is at least one of the following: titanium-based catalyst, zinc-based catalyst, tin-based catalyst, zirconium-based catalyst, molybdenum-based catalyst, iron-based catalyst, chromium-based catalyst, vanadium-based catalyst, tungsten-based catalyst, and nickel-based catalyst; Preferably, the catalyst is used in an amount of 0.05-1% of the weight of dimethyl dicarboxylate.

[0012] Preferably, the alkane solvent is one or more of C6-C10 alkane solvents; the benzene solvent is toluene or xylene.

[0013] Furthermore, the neutralization and washing method involves controlling the temperature of the catalytic reaction solution at 75-80°C, adding an acid solution for a first wash, allowing the layers to separate, and collecting the upper organic phase material to obtain the first-washed material; controlling the temperature of the first-washed material at 75-80°C, adding deionized water for a second wash, allowing the layers to separate, and collecting the upper organic phase material to obtain the second-washed material; and filtering the second-washed material to remove impurities and solvents to obtain a low-alkalinity hindered amine light stabilizer.

[0014] Preferably, in the neutralization washing, the acid solution is one of the following: sulfuric acid, phosphoric acid, nitric acid, hydrochloric acid, acetic acid, citric acid; the concentration of the acid solution is 4-6 wt%.

[0015] Preferably, in the neutralization washing, the weight ratio of acid solution to catalytic reaction solution is 1-1.5:10; The weight ratio of deionized water to the primary washing material is 1-1.5:10.

[0016] A low-basicity hindered amine light stabilizer is prepared by the aforementioned method; the low-basicity hindered amine light stabilizer includes compounds of the following general formula (I): (I); Where n is any integer from 0 to 7.

[0017] Application of one of the aforementioned low-alkalinity hindered amine light stabilizers.

[0018] Compared with the prior art, the beneficial effects of the present invention are as follows: (1) The preparation method of the low-alkalinity hindered amine light stabilizer of the present invention uses a specific dicarboxylic acid dimethyl ester and 1,2,2,6,6-pentamethylpiperidinol as raw materials, and an alkane solvent or a benzene solvent as a solvent. Under the condition of a catalyst, the reaction is heated to obtain a catalytic reaction solution. The catalytic reaction solution is neutralized and washed to obtain the low-alkalinity hindered amine light stabilizer. The preparation method does not require the use of decolorizing agents or the like for decolorization treatment, which effectively avoids the problems of cumbersome decolorization operation, low production efficiency, high cost of decolorizing agents, and difficult post-processing in traditional processes. It can effectively reduce the color of the product while obtaining ideal preparation effects (such as purity, yield, etc.) and overcome the problem that hindered amine light stabilizers cause the product to yellow easily due to absorption of visible light.

[0019] (2) The preparation method of the low-alkalinity hindered amine light stabilizer of the present invention has a yield of 98.0-98.4% and a high yield. The purity of the obtained low-alkalinity hindered amine light stabilizer is 99.5-99.6 wt%, the platinum-cobalt color can reach 5 hazen, the transmittance (λ=425nm) can reach 99%, and the transmittance (λ=500nm) can reach 99%. The obtained hindered amine light stabilizer has a high effective content, low color, and high transmittance. It will not affect the color of downstream products and will not absorb visible light to cause yellowing of products. It can be effectively used in the field of color-sensitive materials (such as transparent plastics and optical materials).

[0020] (3) The preparation method of the low-alkalinity hindered amine light stabilizer of the present invention has a simple process flow, the reaction process is easy to control, and it is conducive to large-scale industrial production. Detailed Implementation

[0021] To provide a clearer understanding of the technical features, objectives, and effects of this invention, specific embodiments are now described. It should be noted that the following detailed descriptions are exemplary and intended to provide further explanation of the invention. Unless otherwise specified, all technical and scientific terms used in this invention have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains.

[0022] It should be noted that the terminology used herein is for the purpose of describing particular embodiments only and is not intended to limit the exemplary embodiments of the present invention. As used herein, "first," "second," etc., are used to distinguish similar objects and are not used to describe a particular order or sequence. Furthermore, it should be understood that when the terms "comprising" and / or "including" are used in this specification, they indicate the presence of features, steps, operations, devices, components, and / or combinations thereof.

[0023] This invention provides a method for preparing a low-alkalinity hindered amine light stabilizer, which uses dimethyl diacid and 1,2,2,6,6-pentamethylpiperidinol as raw materials, and alkane solvents or benzene solvents as solvents. The reaction is carried out under catalytic conditions and in an inert gas environment to obtain the low-alkalinity hindered amine light stabilizer.

[0024] In the preparation method of the low-alkalinity hindered amine light stabilizer, the dimethyl dicarboxylic acid is at least one of the following: dimethyl oxalate, dimethyl malonate, dimethyl succinate, dimethyl glutarate, dimethyl adipate, dimethyl heptaate, dimethyl octanoate, and dimethyl azelaate.

[0025] The method for preparing a low-alkalinity hindered amine light stabilizer according to embodiments of the present invention uses dimethyl diacid and 1,2,2,6,6-pentamethylpiperidinol as raw materials, and alkane solvents or benzene solvents as solvents. Under catalytic conditions, the reaction is carried out at elevated temperature to obtain a catalytic reaction solution. The catalytic reaction solution is neutralized and washed to obtain the low-alkalinity hindered amine light stabilizer. The preparation method does not require decolorization treatment with decolorizing agents, and can effectively reduce the color of the product while obtaining ideal preparation effects (such as purity, yield, etc.), and overcomes the problem that hindered amine light stabilizers cause the product to yellow easily due to absorption of visible light.

[0026] Preferably, the dimethyl dicarboxylic acid is one of the following: dimethyl adipate; a combination of dimethyl succinate, dimethyl glutarate and dimethyl adipate; or a combination of dimethyl octanoate and dimethyl malonate.

[0027] Preferably, when the dimethyl succinate is a combination of dimethyl succinate, dimethyl glutarate and dimethyl adipate, the weight ratio of dimethyl succinate, dimethyl glutarate and dimethyl adipate is 0.4-0.5:1:0.4-0.5.

[0028] Preferably, when the dimethyl dicarboxylate is a combination of dimethyl octanoate and dimethyl malonate, the molar ratio of dimethyl octanoate to dimethyl malonate is 0.8-1:0.8-1.

[0029] In the preparation method of the low-alkalinity hindered amine light stabilizer, the catalyst is at least one of the following: titanium-based catalyst, zinc-based catalyst, tin-based catalyst, zirconium-based catalyst, molybdenum-based catalyst, iron-based catalyst, chromium-based catalyst, vanadium-based catalyst, tungsten-based catalyst, nickel-based catalyst; preferably a titanium-based catalyst; more preferably at least one of the following: tetrapropyl titanate, tetraisopropyl titanate, n-butyl titanate, composite titanium-based catalyst.

[0030] In the preparation method of the low-alkalinity hindered amine light stabilizer, the alkane solvent is one or more of C6-C10 alkane solvents; preferably, the alkane solvent is n-hexane or n-heptane; and the benzene solvent is toluene or xylene.

[0031] In the preparation method of the low-alkalinity hindered amine light stabilizer, dimethyl diacid and 1,2,2,6,6-pentamethylpiperidinol are added in a molar ratio of 1:1-3; preferably, the molar ratio of dimethyl diacid to 1,2,2,6,6-pentamethylpiperidinol is 1:1.6-2.2.

[0032] In the preparation method of the low-alkalinity hindered amine light stabilizer, the volume of the solvent used is 1-3 times the total volume of dimethyl diacidate and 1,2,2,6,6-pentamethylpiperidinol.

[0033] In the preparation method of the low-alkalinity hindered amine light stabilizer, the weight of the catalyst is 0.05-1% of the weight of dimethyl diacid ester; preferably, the weight of the catalyst is 0.3-0.6% of the weight of dimethyl diacid ester.

[0034] In the preparation method of the low-alkalinity hindered amine light stabilizer, the reaction temperature is 100-150℃.

[0035] Specifically, the preparation method of the low-alkalinity hindered amine light stabilizer consists of the following steps: catalytic reaction, neutralization and washing.

[0036] The catalytic reaction method involves adding dimethyl diacid and 1,2,2,6,6-pentamethylpiperidinol to a solvent, stirring and heating the mixture to 100-150°C under a nitrogen atmosphere, adding a catalyst, and maintaining the temperature until no methanol is generated, thereby obtaining a catalytic reaction solution.

[0037] The neutralization and washing method is as follows: the temperature of the catalytic reaction solution is controlled at 75-80℃, an acid solution is added for a first wash until the pH is 9-10, and after standing and separation, the upper organic phase material is obtained by separation, which is the first wash material; the first wash material is heated to 75-80℃, deionized water is added for a second wash, and after standing and separation, the upper organic phase material with a 1,2,2,6,6-pentamethylpiperidinol content <0.1wt% is obtained by separation, which is the second wash material; after filtering to remove impurities, the second wash material is desolventized under negative pressure until no fraction is distilled out, cooled, and a low-alkalinity hindered amine light stabilizer is obtained.

[0038] In the first washing, the acid solution used is one of the following: sulfuric acid, phosphoric acid, nitric acid, hydrochloric acid, acetic acid, citric acid; the concentration of the acid solution is 4-6 wt%.

[0039] In the first washing, the weight ratio of acid solution to catalytic reaction solution is 1-1.5:10.

[0040] In the aforementioned washing cycle, the washing time is 20-30 minutes, and the settling time is 20-30 minutes.

[0041] In the secondary washing process, the weight ratio of deionized water to the material washed in the primary washing process is 1-1.5:10.

[0042] In the secondary washing, the washing time is 20-30 minutes, and the settling time is 20-30 minutes.

[0043] The lower aqueous phase obtained from the stratification during the secondary washing process can be used as washing water for repeated secondary washing.

[0044] This invention also provides a low-alkalinity hindered amine light stabilizer prepared by the aforementioned method. The low-alkalinity hindered amine light stabilizer includes compounds of the following general formula (I): (I); Where n is any integer from 0 to 7.

[0045] This invention also provides the application of the low-alkalinity hindered amine light stabilizer.

[0046] The present invention will be further described below with reference to some specific embodiments.

[0047] Example 1 This embodiment provides a method for preparing a low-alkalinity hindered amine light stabilizer, the specific steps of which are as follows: (1) Add 750g of n-heptane, 752g of 1,2,2,6,6-pentamethylpiperidinol (PMP), and 348g of dimethyl adipic acid ester (DMA) to a 3L reactor and stir until homogeneous. Then, start heating in a nitrogen atmosphere. (2) After the temperature rises to 120°C, add 2.0g of tetraisopropyl titanate catalyst and keep warm to catalyze the transesterification reaction; (3) Keep the catalytic reaction at the temperature until no methanol is generated, and the content of monoester in the reaction system is <0.5wt% to obtain the catalytic reaction solution, and transfer it to the neutralization and washing process; (4) Heat the catalytic reaction solution to 80°C, add 185g of acetic acid solution with a concentration of 5wt%, stir for 20min, let stand for 20min to separate the layers, and then separate the liquid to obtain the upper organic phase material with a pH of 9-10, which is the first washing material. (5) Heat the material washed once to 80°C, add 200g of deionized water, stir for 20min, let stand for 20min to separate the layers, and then separate the liquid to obtain the upper organic phase material with 1,2,2,6,6-pentamethylpiperidinol content <0.1wt%, which is the material washed twice. (6) After the secondary washing material is filtered to remove impurities, the filtrate is subjected to negative pressure desolventizing, the desolventizing temperature is controlled at 150℃, and the desolventizing is carried out until no distillate is distilled out. After cooling, the liquid in the reaction vessel is poured out to obtain a low-alkaline hindered amine light stabilizer.

[0048] In the preparation of the low-alkalinity hindered amine light stabilizer in this embodiment, the effective component obtained is a compound with the following molecular structural formula: .

[0049] The low-alkalinity hindered amine light stabilizer has a yield of 98.4%, a purity of 99.6 wt%, a melting point of 65 °C, a platinum-cobalt color of 5 hazen, a transmittance (λ=425 nm) of 99%, and a transmittance (λ=500 nm) of 99%.

[0050] This embodiment also provides a low-alkalinity hindered amine light stabilizer prepared by the aforementioned method.

[0051] This embodiment also provides the application of the aforementioned low-alkalinity hindered amine light stabilizer.

[0052] Example 2 This embodiment provides a method for preparing a low-alkalinity hindered amine light stabilizer, the specific steps of which are as follows: (1) Add 700g of n-hexane, 685g of 1,2,2,6,6-pentamethylpiperidinol (PMP), 73g of dimethyl succinate (DMS), 160g of dimethyl glutarate (DMG), and 87g of dimethyl adipate (DMA) to a 3L reactor and stir until homogeneous. Then, start heating in a nitrogen atmosphere. (2) After the temperature rises to 110℃, add 2.0g of tetraisopropyl titanate catalyst and keep warm to catalyze the transesterification reaction; (3) Keep the catalytic reaction at the temperature until no methanol is generated, and the content of monoester in the reaction system is <0.5wt% to obtain the catalytic reaction solution, and transfer it to the neutralization and washing process; (4) Heat the catalytic reaction solution to 80°C, add 185g of 5wt% hydrochloric acid solution, stir for 20min, let stand for 20min to separate the layers, and then separate the liquid to obtain the upper organic phase material with pH 9-10, which is the first washing material. (5) Heat the material washed once to 80°C, add 200g of deionized water, stir for 20min, let stand for 20min to separate the layers, and then separate the liquid to obtain the upper organic phase material with 1,2,2,6,6-pentamethylpiperidinol content <0.1wt%, which is the material washed twice. (6) After the secondary washing material is filtered to remove impurities, the filtrate is subjected to negative pressure desolventizing, the desolventizing temperature is controlled at 140℃, and the desolventizing is carried out until no distillate is distilled out. After cooling, the liquid in the reaction vessel is poured out to obtain a low-alkaline hindered amine light stabilizer.

[0053] In the preparation of the low-alkalinity hindered amine light stabilizer in this embodiment, the effective components obtained are the compounds in general formula I with n=3 and the compounds in general formula I with n=4. The yield of the low-alkalinity hindered amine light stabilizer is 98.1%, the purity is 99.5 wt%, the platinum-cobalt colorimetry is 5 hazen, the transmittance (λ=425 nm) is 99%, and the transmittance (λ=500 nm) is 99%.

[0054] This embodiment also provides a low-alkalinity hindered amine light stabilizer prepared by the aforementioned method.

[0055] This embodiment also provides the application of the aforementioned low-alkalinity hindered amine light stabilizer.

[0056] Example 3 This embodiment provides a method for preparing a low-alkalinity hindered amine light stabilizer, the specific steps of which are as follows: (1) Add 870g of xylene, 685g of 1,2,2,6,6-pentamethylpiperidinol PMP, 202g of dimethyl octanoate DMSub and 132g of dimethyl malonate to a 3L reactor and stir until homogeneous. Then, start heating in a nitrogen atmosphere. (2) After the temperature rises to 110℃, add 3.0g of tetraisopropyl titanate catalyst and keep warm to catalyze the transesterification reaction; (3) Keep the catalytic reaction at the temperature until no methanol is generated, and the content of monoester in the reaction system is <0.5wt% to obtain the catalytic reaction solution, and transfer it to the neutralization and washing process; (4) Heat the catalytic reaction solution to 80°C, add 185g of sulfuric acid solution with a concentration of 5wt%, stir for 20min, let stand for 20min to separate the layers, and then separate the liquid to obtain the upper organic phase material with a pH of 9-10, which is the first washing material. (5) Heat the material washed once to 80°C, add 200g of deionized water, stir for 20min, let stand for 20min to separate the layers, and then separate the liquid to obtain the upper organic phase material with 1,2,2,6,6-pentamethylpiperidinol content <0.1wt%, which is the material washed twice. (6) After the secondary washing material is filtered to remove impurities, the filtrate is subjected to negative pressure desolventizing, the desolventizing temperature is controlled at 140℃, and the desolventizing is carried out until no distillate is distilled out. After cooling, the liquid in the reaction vessel is poured out to obtain a low-alkaline hindered amine light stabilizer.

[0057] In the preparation of the low-alkalinity hindered amine light stabilizer in this embodiment, the effective components obtained are the compounds in general formula I when n=1 and the compounds in general formula I when n=6. The yield of the low-alkalinity hindered amine light stabilizer is 98.0%, the purity is 99.6 wt%, the platinum-cobalt colorimetry is 10 hazen, the transmittance (λ=425 nm) is 98%, and the transmittance (λ=500 nm) is 99%.

[0058] This embodiment also provides a low-alkalinity hindered amine light stabilizer prepared by the aforementioned method.

[0059] This embodiment also provides the application of the aforementioned low-alkalinity hindered amine light stabilizer.

[0060] The application performance of the low-alkalinity hindered amine light stabilizers of Examples 1 and 3 were tested and compared with those of existing light stabilizers 770 and 292. Specifically, samples were prepared using polypropylene (PP) as the base material, and various additives were added according to the weight ratios shown in the table below. Light stabilizer 770 is bis(2,2,6,6-tetramethyl-4-piperidinyl) sebacate; light stabilizer 292 is a mixture of bis(1,2,2,6,6-pentamethyl-4-piperidinyl) sebacate and mono(1,2,2,6,6-pentamethyl-4-piperidinyl) sebacate; the weight ratio of bis(1,2,2,6,6-pentamethyl-4-piperidinyl) sebacate to mono(1,2,2,6,6-pentamethyl-4-piperidinyl) sebacate is 3:7. Antioxidant B215 is a mixture of antioxidant 1010 and antioxidant 168; the weight ratio of antioxidant 1010 to antioxidant 168 is 1:2. The specific amounts of raw materials used in each sample are shown in the table below:

[0061] After blending and extruding according to the raw material dosages in the table above, standard test strips were prepared according to national standards, and the mechanical properties of each test strip were tested. Ultraviolet accelerated aging performance tests were also conducted. The tensile properties were tested according to national standard GB / T1040.1-2018; the ultraviolet aging performance was tested according to American standard ASTM G154-2016. The initial tensile properties of each sample (i.e., before ultraviolet aging) are shown in the table below:

[0062] Furthermore, after subjecting each sample to UV aging for 100 hours using the aforementioned testing method, the tensile properties of each test were tested. The specific results are shown in the table below:

[0063] Furthermore, after subjecting each sample to UV aging for 150 hours according to the aforementioned testing method, the tensile properties of each test were tested, and the specific results are shown in the table below:

[0064] Furthermore, using the samples before UV aging as a benchmark, the color difference changes of the samples after 100 hours of UV aging and after 150 hours of UV aging were measured. The testing method followed the American standard ASTM D2244. The specific results are shown in the table below:

[0065] It can be seen that the low-alkalinity hindered amine light stabilizer of the present invention can effectively improve the light stability of the material, enabling polypropylene material to maintain good mechanical properties and color difference during ultraviolet aging. Its light stability performance is significantly better than that of existing light stabilizer products, and it can better extend the service life of the material.

[0066] Unless otherwise stated, all percentages used in this invention are mass percentages.

[0067] Finally, it should be noted that the above descriptions are merely preferred embodiments of the present invention and are not intended to limit the present invention. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art can still modify the technical solutions described in the foregoing embodiments or make equivalent substitutions for some of the technical features. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A process for the preparation of a low-alkaline hindered amine light stabilizer, characterized in that, The low-alkaline hindered amine light stabilizer is prepared by the following steps: taking dimethyl dicarboxylate and 1,2,2,6,6-pentamethylpiperidinol as raw materials, an alkane solvent or a benzene solvent as a solvent, and a catalyst, and then reacting in an inert gas environment at a temperature of 100-150 DEG C; and then neutralizing and washing the catalytic reaction liquid to obtain the low-alkaline hindered amine light stabilizer. The dimethyl dicarboxylate is at least one of dimethyl oxalate, dimethyl malonate, dimethyl succinate, dimethyl glutarate, dimethyl adipate, dimethyl pimelate, dimethyl suberate, and dimethyl azelate.

2. The process for the preparation of a low-alkaline hindered amine light stabilizer according to claim 1, characterized in that, The molar ratio of the dimethyl dicarboxylate to the 1,2,2,6,6-pentamethylpiperidinol is 1:1-3.

3. The method of preparing a low base hindered amine light stabilizer according to claim 1, characterized by, The volume of the solvent is 1-3 times the total volume of the dimethyl dicarboxylate and the 1,2,2,6,6-pentamethylpiperidinol.

4. The process for the preparation of low base hindered amine light stabilizer according to claim 1, characterized in that, The catalyst is at least one of a titanium catalyst, a zinc catalyst, a tin catalyst, a zirconium catalyst, a molybdenum catalyst, an iron catalyst, a chromium catalyst, a vanadium catalyst, a tungsten catalyst, and a nickel catalyst. The weight amount of the catalyst is 0.05-1% of the weight of the dimethyl dicarboxylate.

5. The method of preparing a low base hindered amine light stabilizer according to claim 1, characterized by, The alkane solvent is one or more of C6-C10 alkane solvents; and the benzene solvent is toluene or xylene.

6. The method of preparing a low base hindered amine light stabilizer according to claim 1, characterized by, The method of the neutralization and washing is as follows: controlling the temperature of the catalytic reaction liquid to be 75-80 DEG C, adding an acid solution for primary washing, collecting the upper organic phase material after static stratification, obtaining the primary washing material; controlling the temperature of the primary washing material to be 75-80 DEG C, adding deionized water for secondary washing, collecting the upper organic phase material after static stratification, obtaining the secondary washing material; and then filtering the secondary washing material to remove impurities and remove the solvent, obtaining the low-alkaline hindered amine light stabilizer.

7. The process for the preparation of a low-alkaline hindered amine light stabilizer according to claim 6, characterized in that, In the neutralization and washing, the acid solution is one of sulfuric acid, phosphoric acid, nitric acid, hydrochloric acid, acetic acid, and citric acid; and the concentration of the acid solution is 4-6 wt%.

8. The process for the preparation of a low-alkaline hindered amine light stabilizer according to claim 6, characterized in that, In the neutralization and washing, the weight ratio of the acid solution to the catalytic reaction liquid is 1-1.5:

10. The weight ratio of the deionized water to the primary washing material is 1-1.5:

10.

9. A low-alkaline hindered amine light stabilizer characterized by, The low-alkaline hindered amine light stabilizer is prepared by the preparation method of any one of claims 1-8. The low-alkaline hindered amine light stabilizer comprises a compound of the following general formula (I): （I）； In the formula, n is any integer from 0 to 7.

10. Use of the low-alkaline hindered amine light stabilizer of claim 9.

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