A continuous preparation method of a benzotriazole light stabilizer intermediate

Abstract

The present invention provides a continuous preparation method of a benzotriazole light stabilizer intermediate. The preparation method includes: reacting molten o-amine with an acid solution to obtain a first reaction solution; atomizing and spraying the first reaction solution into water or an organic solvent to obtain a slurry containing o-amine salt; sequentially passing the slurry through a multi-stage pipeline reactor to carry out a diazotization reaction with a diazotizing reagent to obtain a second reaction solution; and adding the second reaction solution to a phenol solution to carry out a coupling reaction to obtain the product. The continuous preparation method provided by the present invention has simple process, high controllability, is green and environmentally friendly, can significantly improve the production efficiency of the benzotriazole light stabilizer intermediate and the final product, and reduce the production cost. Therefore, it has very important economic and social value.

Description

Technical Field

[0001] The present invention relates to the field of chemical intermediate manufacturing, and specifically relates to a continuous preparation method of a benzotriazole light stabilizer intermediate. Background Art

[0002] Ultraviolet rays in sunlight can cause oxidation reactions in polymer materials such as rubber and plastics, damage the structure of polymers, and accelerate their aging process. To avoid or slow down the photochemical and photophysical aging of polymer materials, it is necessary to use a certain amount of light stabilizers. Light stabilizers can prevent polymer materials from undergoing photo-oxidative aging and greatly improve their service life. Currently, in various products such as plastic products, fibers, rubber products, coatings, paints, adhesives, etc., light stabilizers are essential additive components. In the development of plasticization of automotive parts, the requirement for weather resistance is higher, and the demand for light stabilizers is also greater.

[0003] Benzotriazole (BZT) light stabilizers have excellent ultraviolet absorption ability, and also have advantages such as light color, low toxicity, low volatility, good oil resistance, and good compatibility with polymers. They are widely used in the photochemical modification of various synthetic polymer materials such as polypropylene, polyethylene, polyvinyl chloride, polyoxymethylene, polyamide, polystyrene, polyurethane, alkyd resin, etc. They are the type with the most varieties and the largest output currently, and their application in plastics is second only to hindered amines.

[0004] In the preparation process of BZT light stabilizers, an important intermediate compound (also called "parent compound") needs to be used, as shown in general formula (III). This parent compound contains two benzene rings, is connected by an N=N bond, and has a nitro group at the ortho position on one benzene ring. This parent compound belongs to a kind of azo compound, which is an important chemical product. It can be directly used as an azo dye or used as a raw material or intermediate for producing other products. Usually, as shown in synthesis route 1, the production method of this parent compound is to carry out a diazotization reaction between o-amine shown in formula (I) and sodium nitrite to generate a diazonium salt shown in formula (II), and then carry out a substitution reaction with the corresponding phenol to generate the parent compound shown in formula (III). This parent compound is then subjected to processes such as purification, reduction ring closure, and post-treatment to obtain the target product of BZT light stabilizers shown in formula (IV).

[0005]

[0006] Synthesis Route 1

[0007] In industrial production, this type of parent compound needs to go through the following reaction process: o-amine reacts with sulfuric acid to dissolve, water is added to cool down and the salt is precipitated, then it reacts with sodium nitrite solution to carry out diazotization reaction to form diazonium salt, and the diazonium salt reacts with the corresponding phenol under appropriate conditions to carry out electrophilic substitution reaction, and finally the target product is obtained after purification. Although this production process is technically mature, there are the following problems: (1) It needs to go through multiple process steps; (2) Each process step requires a large amount of machine time and equipment, and a large amount of raw material liquid or reaction liquid needs to be stored. The floor area and utilization rate of the equipment are low, and the production efficiency is low; (3) The o-amine acidic solution needs to be stored at high temperature and has strong corrosiveness, and the precipitated o-amine salt is easy to agglomerate and not suitable for long-term storage; (4) The generated diazonium salt is unstable, easy to decompose or even explode, with relatively large safety and environmental protection risks; (5) The diazotization reaction is violent, with a large amount of heat released instantaneously, and the reaction needs to be controlled under low-temperature conditions. It is easy to explode under high-temperature conditions and belongs to the national key dangerous process; (6) Due to the intermittent process of multiple process steps, the raw materials and reaction liquids need to be stored for a long time. At the same time, the batch reaction uses kettle equipment, which is large in volume and has poor mass transfer and heat transfer effects in the kettle. Therefore, there are differences between batches, resulting in lower quality and yield of the obtained parent compound, and it is less stable between batches; (7) Since the intermittent process requires long-term and large-scale storage of raw material liquid and reaction liquid, in order to avoid or reduce phenomena such as precipitation of raw material liquid and decomposition of reaction liquid, a large excess of acid needs to be used. These acids ultimately need to be neutralized into salts and become waste salts, which not only increases the production cost, but also increases the disposal equipment and costs of waste salts.

[0008] After comprehensively analyzing the many problems existing in the production process of the BZT type light stabilizer intermediate - the parent compound, it is not difficult to see that there is an urgent need to develop a method suitable for industrial production of this type of parent compound to improve the safety benefits, environmental benefits and economic benefits of the process. Summary of the Invention

[0009] To make up for the deficiencies in the existing technology, an object of the present invention is to provide a continuous preparation method for benzotriazole type light stabilizer intermediates. This preparation method can systematically integrate the original multi-step batch process into a continuous process, so it can achieve continuous operation and continuous production, improve production efficiency and reduce production costs.

[0010] Based on the problems such as poor mass transfer and heat transfer effects existing in batch reactions, especially the safety and environmental protection problems brought by fast reactions with high heat release, continuous flow technology has received more and more attention and has been extensively studied and applied. The No. 1 document of the State Administration of Work Safety in 2017 clearly states that for process hazards at levels 4 and 5, especially projects with high risks but that must be industrialized, efforts should be made to give priority to optimizing the process or changing the process method to reduce risks, such as completing reactions through microreactors and continuous flow.

[0011] Continuous flow chemistry refers to the continuous pumping of two (or more) reagents into a reactor (Flow Reactor), where mixing and reaction occur, and the reaction temperature is controlled by a heat exchange controller to achieve a chemical reaction and obtain the desired product. Continuous flow chemistry has been widely applied in the fields of large-scale chemical engineering and pharmaceutical chemical engineering. Compared with batch processes, it has advantages such as high process safety, precise process control, high selectivity and yield, multi-step continuous operation, high production efficiency, low production cost, and a clean working environment.

[0012] The present invention provides a method for continuously producing such parent compounds to achieve continuous production and enhance the safety, environmental, and economic benefits of the process.

[0013] The first aspect of the present invention provides a method for continuously preparing a benzotriazole light stabilizer intermediate, comprising the following steps:

[0014] S1: Reacting molten o - amine represented by formula (I) with an acid solution to obtain a first reaction solution;

[0015] S2: Atomizing and spraying the first reaction solution into water or an organic solvent to obtain a slurry containing o - amine salt;

[0016] S3: Sequentially passing the slurry through a multi - stage pipe reactor to carry out a diazotization reaction with a diazotizing reagent to obtain a second reaction solution containing a diazonium salt represented by formula (II);

[0017] S4: Adding the second reaction solution to a phenol solution represented by formula (I') to carry out a coupling reaction, thereby obtaining a benzotriazole light stabilizer intermediate represented by formula (III);

[0018]

[0019] Wherein, R1 represents hydrogen, a halogen, or a substituted or unsubstituted C1 - C6 alkyl; R2 represents hydrogen, a substituted or unsubstituted C1 - C10 alkyl, a substituted or unsubstituted C1 - C6 alkoxy, or a substituted or unsubstituted C6 - C20 aryl; R3 represents a substituted or unsubstituted C1 - C12 alkyl, a substituted or unsubstituted C1 - C6 alkoxy, or a substituted or unsubstituted C6 - C20 aryl;

[0020] When the above groups are substituted groups, the number of substituents is 1, 2, or 3, and each independently is selected from a halogen, -COO(C1 - C6 alkyl), C1 - C6 alkyl, C1 - C4 alkoxy, or C6 - C12 aryl.

[0021] Specifically, as Figure 1As shown, the continuous preparation method of the present invention uses an orthoamine as shown in formula (I) as a starting material, first melts it to form an orthoamine melt, and then reacts and dissolves it with an acid solution to obtain a first reaction liquid. The first reaction liquid is added to water or an organic solvent by atomization spraying, and the orthoamine acid salt in the first reaction liquid forms small particles and precipitates, thereby obtaining a slurry containing orthoamine acid salt particles. The slurry flows sequentially through a multi-stage pipeline reactor, and the multi-stage pipeline reactor is a pipeline reactor of 2-10 stages ( Figure 1 (a three-stage pipeline reactor is used as an example), the diazotizing agent is added to the multi-stage pipeline reactor according to different distribution ratios, and the o-ammonium salt and the diazotizing agent undergo a diazotization reaction, thereby obtaining a second reaction solution containing a diazonium salt represented by formula (II). Finally, the second reaction solution is added to a phenol solution represented by formula (I'), and the diazonium salt and the phenol raw material undergo a coupling reaction to prepare a benzotriazole light stabilizer intermediate represented by formula (III).

[0022] The continuous preparation method provided by the present invention integrates the original multi-step batch process into a continuous process, thereby enabling continuous production of benzotriazole light stabilizer intermediates with high production efficiency, high yield of target product, and low raw material residue. In the original batch process, diazonium salts usually require a long storage time, and diazonium salts are unstable and easily decomposed. Therefore, the amount of ortho-amine used is often excessive compared to phenol. At the same time, in order to reduce the decomposition of diazonium salts, a large amount of acid is required to maintain their stability. The continuous process provided by the present invention can significantly shorten the retention time of diazonium salts, avoid their decomposition, and thus can effectively reduce the amount of materials such as ortho-amine, acid, and base used to neutralize the acid.

[0023] In the existing intermittent process, the commonly used water-addition salt precipitation process precipitates millimeter-sized or larger crystalline particles, which may even form lumps, making it difficult to adapt to the continuous reaction of a multi-stage pipeline reactor and unfavorable for the diazotization reaction. The preparation method of the present invention can make the precipitated o-ammonium salt into micron-sized or even nanometer-sized particles through atomization spraying, thereby allowing the subsequent multi-stage pipeline reaction to proceed smoothly without causing blockage of pipelines or equipment. Moreover, the small particles of o-ammonium salt also have a large specific surface area, which can increase its contact with the diazotization reagent, thereby improving the reaction efficiency of the diazotization reaction.

[0024] The continuous preparation method of the present invention also uses a series of multi-stage tubular reactors for diazotization reaction, so that the reaction degree and heat release of each stage of the reaction can be accurately controlled, thus making the overall diazotization reaction effectively controllable and significantly reducing the safety risk of the process. In some preferred embodiments, the multi-stage tubular reactor can be a 2-5 stage tubular reactor. In the continuous preparation method provided by the present invention, the benzotriazole light stabilizer intermediate can be any common type in the art. In some preferred embodiments, R1 can represent hydrogen or chlorine. In some other preferred embodiments, R2 represents hydrogen, C1-C8 alkyl (for example, methyl, ethyl, propyl, isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl, 1,1-dimethyl-propyl, etc.), benzyl or cumyl. In still some other preferred embodiments, R3 represents hydrogen, C1-C10 alkyl (for example, methyl, ethyl, propyl, isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl, 1,1-dimethyl-propyl, tert-octyl, etc.), benzyl, cumyl or -(C1-C4 alkylene)COO(C1-C4 alkyl).

[0025] In the continuous preparation method provided by the present invention, the benzotriazole light stabilizer intermediate and its corresponding product can be further as shown in Table 1.

[0026] Table 1

[0027]

[0028] In the continuous preparation method provided by the present invention, in step S1, according to the melting point of different o-amine raw materials, the o-amine raw materials are heated to a temperature above the melting point (usually 5-10 °C higher than the melting point temperature) to melt them, and they are kept warm at the same temperature for use, thereby obtaining the molten o-amine raw materials.

[0029] In the continuous preparation method provided by the present invention, in step S1, the acid solution can be sulfuric acid or hydrochloric acid solution, and its mass concentration can be 35-90%, for example, it can be about 35%, about 40%, about 50%, about 60%, about 70%, about 80%, about 90% or any combined concentration range.

[0030] In the continuous preparation method provided by the present invention, in step S1, the molar ratio of the acid in the acid solution to the o-amine can be 1-5:1. In some preferred embodiments, the molar ratio of the acid in the acid solution to the o-amine can be 1.2-3:1.

[0031] In the continuous preparation method provided by the present invention, in step S1, according to different o-amine raw materials, the reaction temperature of the o-amine and the acid solution can be 60-120 °C, for example, it can be 60 °C, about 65 °C, about 70 °C, about 75 °C, about 80 °C, about 85 °C, about 90 °C, about 100 °C, about 110 °C, about 120 °C or any combined temperature range.

[0032] In the continuous preparation method provided by the present invention, in step S1, it is necessary to control the flow rates of the o-amine raw material and the acid solution so that the two react fully and the resulting first reaction solution is in a homogeneous liquid state.

[0033] In the continuous preparation method provided by the present invention, step S2 can be further: atomizing and spraying the first reaction solution into a container pre-added with the water or organic solvent to obtain a slurry containing o-amine salt. In some preferred embodiments, 50-70% of the volume of the container can be pre-added with water or organic solvent.

[0034] In the continuous preparation method provided by the present invention, in step S2, while atomizing and spraying the first reaction solution, the water or organic solvent can also be atomized and sprayed into the container, and this operation can further improve the efficiency of the cooling and precipitation of the o-amine salt. In some preferred embodiments, the mass ratio of the flow rate of the sprayed water or organic solvent to the flow rate of the o-amine raw material can be 1.5-5:1, for example, it can be 2-4:1.

[0035] In the continuous preparation method provided by the present invention, in step S2, the organic solvent can be selected from any common types in the art, as long as the o-amine salt can precipitate therein and does not chemically react with the raw materials. For example, it can be one or more of methanol, ethanol, isopropanol, C8-C12 straight-chain alkanes (such as octane, nonane, decane, etc., which can be a single solvent or a mixed alkane), toluene, and xylene. In some preferred embodiments, the o-amine salt precipitates in water.

[0036] In the continuous preparation method provided by the present invention, the temperature in step S2 can be 10-50 °C, for example, it can be about 10 °C, about 20 °C, about 25 °C, about 30 °C, about 35 °C, about 40 °C, about 50 °C or any combined temperature range. In some preferred embodiments, the temperature in step S2 can be 20-30 °C.

[0037] In the continuous preparation method provided by the present invention, in step S3, the diazotizing reagent can be a sodium nitrite solution or other common diazotizing reagents in the art. In some preferred embodiments, the mass concentration of the sodium nitrite solution can be 10-50%, for example, it can be about 10%, about 15%, about 20%, about 25%, about 30%, about 35%, about 40%, about 45%, about 50% or any combination of concentration ranges.

[0038] In the continuous preparation method provided by the present invention, in step S3, the molar ratio of the diazotizing reagent to the o-amine can be 1-1.3:1. In some preferred embodiments, the molar ratio of the diazotizing reagent to the o-amine can be 1-1.1:1.

[0039] In the continuous preparation method provided by the present invention, in step S3, the temperature in the tubular reactor can be 0-30°C, for example, it can be 0°C, about 5°C, about 10°C, about 15°C, about 20°C, about 25°C, about 30°C or any combination of temperature ranges. In some preferred embodiments, the temperature in the tubular reactor can be 5-15°C.

[0040] In the continuous preparation method provided by the present invention, in step S3, along the flow direction of the slurry, the distribution ratio of the diazotizing reagent in the multi-stage tubular reactor decreases or is equal step by step by mass; preferably, the distribution ratio of the diazotizing reagent in the three-stage tubular reactor by mass can be 40-70%:20-50%:5-15%. By controlling the distribution ratio of the diazotizing reagent in the multi-stage tubular reactor, the process of the diazotization reaction can be conveniently controlled, thereby better controlling the heat release of each stage of the reaction, making the overall diazotization reaction more stable and controllable, reducing the safety risk and improving the reaction efficiency. In some preferred embodiments, the distribution ratio of the diazotizing reagent in the three-stage tubular reactor by mass can be 50-60%:30-40%:8-12%.

[0041] In the continuous preparation method provided by the present invention, in step S4, the phenol solution can be an aqueous solution or an organic solvent solution of phenol, and the organic solvent can be any type that can dissolve the phenol raw material and does not affect the coupling reaction, such as organic alcohol or fatty alcohol solvents. In some preferred embodiments, the organic solvent can be selected from one or more of methanol, ethanol, and isopropanol.

[0042] In the continuous preparation method provided by the present invention, according to the coupling reaction process conditions of different target products, step S4 may further include adjusting the pH value of the reaction system of the coupling reaction, and the pH value is adjusted according to different product requirements. The adjustment method may be to pre-add an inorganic base as an auxiliary agent in the phenol solution, or to add an inorganic base solution (such as an inorganic base solution with a mass concentration of 5-50%) to the reaction system during the reaction process. In some preferred embodiments, the inorganic base may be sodium hydroxide or potassium hydroxide.

[0043] In the continuous preparation method provided by the present invention, in step S4, the reaction temperature of the coupling reaction may be 0-30°C, for example, it may be 0°C, about 5°C, about 10°C, about 15°C, about 20°C, about 25°C, about 30°C or any combination of temperature ranges. In some preferred embodiments, the reaction temperature of the coupling reaction may be 0-15°C.

[0044] The second aspect of the present invention provides a preparation method of a benzotriazole light stabilizer, which uses the continuous preparation method described in any one of the above technical solutions to obtain a benzotriazole light stabilizer intermediate shown in formula (III), and then obtains a benzotriazole light stabilizer shown in formula (IV) through a reduction reaction;

[0045]

[0046] Wherein, R1, R2 and R3 are each independently defined as in any one of the above technical solutions.

[0047] The reduction reaction of the benzotriazole is a method known in the art, and can be achieved by using a commonly used reduction method in the art.

[0048] In some preferred embodiments, the structural formula of the benzotriazole (BTZ) light stabilizer product of the present invention is shown in Table 1.

[0049] The above technical solutions provided by the present invention have the following advantages:

[0050] (1) The continuous preparation method of the present invention overcomes the defects of the batch process, such as large liquid holdup, large differences between different batches, high safety and environmental protection risks, etc. It can reduce the liquid holdup of each batch of the batch process from more than 10 cubic meters to less than 200L. At the same time, it can achieve precise control and stop the reaction at any time according to the actual reaction situation. The differences between different production batches have been significantly reduced, and the safety and environmental protection risks can also be greatly reduced.

[0051] (2) The continuous preparation method of the present invention can complete the transportation and reaction of raw materials and reaction liquids in a closed system, so it can realize full-process automatic control, reduce on-site personnel operations, and has a good working environment and high safety.

[0052] (3) The continuous preparation method of the present invention can significantly improve production efficiency, reduce production costs, and the target product obtained has a high yield and good quality.

[0053] (4) The continuous preparation method of the present invention can also significantly reduce the usage amounts of materials such as o - amine, acid, and base (about 10 - 40% can be reduced), and thus can also reduce the generation amount of waste salt (about 10 - 40% can be reduced). Therefore, it can further reduce production costs and relieve the treatment pressure of industrial waste.

[0054] (5) The continuous preparation method of the present invention does not require the use of complex devices or equipment. The floor area of the whole production system is greatly reduced, and it can operate stably for a long time with strong industrial practicability. In summary, the preparation method provided by the present invention has a simple process, high controllability, is green and environmentally friendly, can significantly improve the production efficiency of benzotriazole - type light stabilizer intermediates and end - products, and reduce their production costs. Therefore, it has very important economic and social values. BRIEF DESCRIPTION OF THE DRAWINGS

[0055] Figure 1 is the process flow chart of the continuous preparation method described in the present invention.

[0056] Figure 2 is the schematic diagram of the structural composition of the continuous preparation device used in the examples of the present invention;

[0057] Among them, the reference numerals are as follows:

[0058] 1, Reactor 1#; 2, Reactor 2#; 3, Reactor 3#; 4, Combined pipeline reactor; 4 - 1, First - stage pipeline reactor; 4 - 2, Second - stage pipeline reactor; 4 - 3, Third - stage pipeline reactor;

[0059] A, Molten o - amine raw material; B, Acid solution; C, Water or organic solvent; D, Diazotizing reagent; E, Inorganic base solution. DETAILED DESCRIPTION OF THE INVENTION

[0060] TERMS

[0061] As used herein, "C1-Cn" includes C1-C2, C1-C3, …… C1-Cn. For example, the group "C1-C10" means that this part has 1 to 10 carbon atoms, that is, the group contains 1 carbon atom, 2 carbon atoms, 3 carbon atoms, 4 carbon atoms, 5 carbon atoms, 6 carbon atoms, 7 carbon atoms, 8 carbon atoms, 9 carbon atoms or 10 carbon atoms. Therefore, for example, "C1-C4 alkyl" means an alkyl group containing 1 to 4 carbon atoms, that is, the alkyl group is selected from methyl, ethyl, propyl, isopropyl, n-butyl, isobutyl, sec-butyl and tert-butyl. The numerical ranges in this article, such as "1-6", refer to each integer in the given range.

[0062] The term "alkyl" used alone or in combination herein refers to an optionally substituted straight-chain or optionally substituted branched-chain saturated aliphatic hydrocarbon. The "alkyl" herein preferably may have 1 to 12 carbon atoms, for example, 1 to 10 carbon atoms, or 1 to 8 carbon atoms, or 1 to 6 carbon atoms, or 1 to 5 carbon atoms, or 1 to 4 carbon atoms, or 1-3 carbon atoms. Non-limiting examples of alkyl include methyl, ethyl, n-propyl, isopropyl, 2-methyl-1-propyl, 2-methyl-2-propyl, 2-methyl-1-butyl, 3-methyl-1-butyl, 2-methyl-3-butyl, 2,2-dimethyl-1-propyl, 2-methyl-1-pentyl, 3-methyl-1-pentyl, 4-methyl-1-pentyl, 2-methyl-2-pentyl, 3-methyl-2-pentyl, 4-methyl-2-pentyl, 2,2-dimethyl-1-butyl, 3,3-dimethyl-1-butyl, 2-ethyl-1-butyl, n-butyl, isobutyl, sec-butyl, tert-butyl, n-pentyl, isopentyl, neopentyl, tert-pentyl and hexyl, and longer alkyl groups such as heptyl and octyl, etc. When a numerical range appears for a group defined herein, such as "alkyl", for example, "C1-C6 alkyl" means an alkyl group that can be composed of 1 carbon atom, 2 carbon atoms, 3 carbon atoms, 4 carbon atoms, 5 carbon atoms or 6 carbon atoms. The alkyl groups herein also include cases where no numerical range is specified.

[0063] "Alkyl" used in combination herein refers to an alkyl group connected to other groups. For example, the alkyl group in alkoxy has the same definition as when used alone.

[0064] The term "alkoxy" used alone or in combination herein refers to an alkyl ether group, represented as "alkyl-O-". Non-limiting examples of alkoxy include methoxy, ethoxy, n-propoxy, isopropoxy, n-butoxy, isobutoxy, sec-butoxy, tert-butoxy, etc.

[0065] As used herein, the term "aryl" alone or in combination refers to an optionally substituted aromatic hydrocarbon group having 6 to 20, such as 6 to 12 or 6 to 10 ring carbon atoms, which may be a monocyclic aryl, bicyclic aryl or polycyclic aryl. The bicyclic aryl or polycyclic aryl may be a monocyclic aryl fused with other independent rings, such as an alicyclic ring or an aromatic ring. Non-limiting examples of monocyclic aryl include phenyl; non-limiting examples of bicyclic aryl include naphthyl; non-limiting examples of polycyclic aryl include phenanthryl, anthryl, fluorenyl, azulyl.

[0066] As used herein, the term "halogen" alone or in combination refers to fluorine (F), chlorine (Cl), bromine (Br) or iodine (I).

[0067] The technical solutions of the present invention will be further described in detail below in conjunction with specific embodiments.

[0068] The raw materials or reagents used in the examples and comparative examples of the present invention are all commercially available products unless otherwise specified.

[0069] The percentages used in the examples and comparative examples of the present invention are all mass percentages unless otherwise specified.

[0070] The continuous preparation device used in the examples of the present invention is as Figure 2 shown. The main body includes a 1# reactor 1, a 2# reactor 2, a combined pipeline reactor 4 (which is composed of a first-stage pipeline reactor 4-1, a second-stage pipeline reactor 4-2 and a third-stage pipeline reactor 4-3 connected in series in the order of material flow), and a 3# reactor 3 connected in sequence. Among them, the 1# reactor is respectively connected to the molten o-amine raw material A (denoted as RM-1) and the acid solution B (denoted as RM-2), the 2# reactor is connected to the water or organic solvent C (denoted as RM-3) for precipitating o-amine salt, the three-stage pipeline reactor is respectively connected to the diazotizing reagent D (such as sodium nitrite solution, denoted as RM-4), and the 3# reactor is connected to the inorganic base solution E (such as sodium hydroxide solution, denoted as RM-5) for adjusting the pH value of the coupling reaction.

[0071] In the above device, the pipe length of the pipeline reactor 4 is 150 cm (50 cm for each stage, spiral coil, coil diameter is 2 - 3 cm), the pipe diameter is 3 mm, the 1# reactor is a reaction tube of about 6 mL (tube length is 80 cm, pipe diameter is 3 mm), the 2# reactor is a 50 mL four-necked round-bottom flask with a bottom outlet, and the 3# reactor is a 1000 mL four-necked flask. The above device may also include pipelines, pumps, valves, flow meters, stirring devices, heat exchange devices, atomizing nozzles, etc. commonly used in the art as needed.

[0072] When the above-mentioned device is in operation, the molten o-amine raw material and the acid solution are first fed into the 1# reactor for reaction and dissolution to obtain the first reaction solution. The first reaction solution is sprayed into the 2# reactor through an atomizing nozzle. A certain amount of water or organic solvent is pre-added to the 2# reactor. Meanwhile, water or organic solvent can also be sprayed through another nozzle as needed. The o-amine salt in the first reaction solution precipitates in the form of nano-scale or micro-scale fine particles to obtain a slurry containing o-amine salt. The slurry flows through three-stage pipe reactors in sequence, and the diazotizing reagent is added to the three-stage pipe reactors according to different distribution ratios. The o-amine salt reacts with the diazotizing reagent to obtain a second reaction solution containing diazonium salt. Finally, the second reaction solution is fed into the 3# reactor which has been added with a phenol solution (a solution formed by dissolving the phenol raw material in water or an organic solvent). The diazonium salt reacts with the phenol raw material to prepare the parent compound. According to the reaction conditions required for different target products, inorganic bases such as sodium hydroxide can also be added to the phenol solution as an auxiliary agent, or an inorganic base solution can be added to the reaction system during the reaction to adjust the pH value of the reaction system.

[0073] Example 1 Synthesis of the parent compound of 2-(2'-hydroxy-5'-methylphenyl) benzotriazole (UV-P)

[0074] Take 69.76 g (99%, 0.5 mol) of o-nitroaniline in a round-bottom flask, heat it to 80 °C until it completely melts, and keep it warm for use, denoted as RM-1 (total mass 69.76 g);

[0075] Take 100.00 g (98%, 1 mol) of sulfuric acid and 100.00 g (5.56 mol) of water in a beaker, prepare a solution, and keep it warm at 70 °C for use, denoted as RM-2 (total mass 200 g);

[0076] Take 150 g (8.33 mol) of water in a beaker for use, denoted as RM-3 (total mass 150 g);

[0077] Take 42.00 g (98.5%, 0.6 mol) of sodium nitrite and 95 g (5.28 mol) of water in a beaker, prepare a solution for use, denoted as RM-4 (total mass 137 g);

[0078] Take 60 g (99%, 1.5 mol) of sodium hydroxide and 180 g (10 mol) of water in a beaker, prepare a solution for use, denoted as RM-5 (total mass 240 g).

[0079] According to Figure 2Set up the device as shown and connect accessories such as pumps, pipelines, and valves. Add 100 g of water to the 2# reactor and start stirring. Add 55.00 g (98.5%, 0.5 mol) of p-cresol, 150 g (8.33 mol) of water, and 20 g (99%, 0.5 mol) of sodium hydroxide to the 3# reactor, start stirring to completely dissolve them, and cool down to 0 - 5 °C with ice melting.

[0080] Place the prepared raw material liquids on their respective electronic balances, connect the feeding pipelines, start the raw material pump and the pipeline reactor feeding pump, and set the flow rates as follows: RM-1 is 1.16 g / min, RM-2 is 3.33 g / min, RM-3 is 2.5 g / min, RM-4 is 2.28 g / min. At the same time, adjust the valves so that the flow rate ratio of RM-4 in the pipeline reactors of the first to third stages is 6:3:1 by mass. Keep the inlet and outlet flow rates of the 2# reactor and each stage of the pipeline reactor balanced. Control the temperature of the 1# reactor at 70 - 75 °C, the temperature of the 2# reactor at 25 - 30 °C, the temperature of the pipeline reactors of the first to third stages at 5 - 15 °C, and the temperature of the 3# reactor at 0 - 5 °C. Adjust the addition time and flow rate of RM-5 to control the pH of the material in the 3# reactor to be 8 - 10.

[0081] After the feeding of each raw material is completed, transfer all the materials in the 1# reactor, 2# reactor, and pipeline reactor to the 3# reactor, continue the heat preservation reaction for 1 - 2 h, then filter, wash the filter cake three times with hot water at 70 - 80 °C, dry it, weigh it, and test it. The test results are shown in Table 2.

[0082] Example 2 Synthesis of UV-P Parent Compound

[0083] RM-2 becomes 400 g of hydrochloric acid (35 - 37%, 1.47 mol), with a total mass of 400 g; the flow rate of RM-2 is 6.67 g / min; the flow rate of RM-3 is 0 g / min; the rest is the same as in Example 1. The test results are shown in Table 2.

[0084] Example 3 Synthesis of UV-P Parent Compound

[0085] RM-2 becomes take 65.00 g (98%, 0.65 mol) of sulfuric acid and 50.00 g (2.78 mol) of water in a beaker, prepare a solution, and keep it at 70 °C for later use, with a total mass of 115 g; the flow rate of RM-2 becomes 1.92 g / min; the rest is the same as in Example 1. The test results are shown in Table 2.

[0086] Example 4 Synthesis of UV-P Parent Compound

[0087] The flow rate ratio of the first to third-stage pipe reactors is adjusted to 5:4:1; the temperature of the first to third-stage pipe reactors is controlled at 15 - 20 °C; the rest is the same as in Example 1, and the test results are shown in Table 2.

[0088] Example 5 Synthesis of UV-P parent compound

[0089] The flow rate ratio of the first to third-stage pipe reactors is adjusted to 8:1:1; the temperatures of the first to third-stage pipe reactors are respectively controlled at 20 - 30 °C, 0 - 10 °C, 0 - 10 °C (due to the flow rate distribution of the diazotizing reagent in the third-stage pipe reactor, the local reaction in the first-stage reactor is intense, the temperature is out of control, and it is difficult to control at a low temperature), the rest is the same as in Example 1, and the test results are shown in Table 2.

[0090] Example 6 Synthesis of 2-(2’-hydroxy-3’-tert-butyl-5’-methylphenyl)-5-chlorobenzotriazole (UV-326) parent compound

[0091] Take 87.59 g (98.5%, 0.5 mol) of p-chloro-o-nitroaniline in a round-bottom flask, heat it to 125 - 130 °C until it completely melts, and keep it warm for use, denoted as RM-1 (total mass 87.59 g);

[0092] Take 100.00 g (98%, 1.0 mol) of sulfuric acid and 10.00 g (0.56 mol) of water in a beaker, prepare a solution, and keep it warm at 70 °C for use, denoted as RM-2 (total mass 110 g);

[0093] Take 150 g (8.33 mol) of water in a beaker for use, denoted as RM-3 (total mass 150 g);

[0094] Take 40.00 g (98.5%, 0.57 mol) of sodium nitrite and 90 g (5 mol) of water in a beaker, prepare a solution for use, denoted as RM-4 (total mass 130 g).

[0095] Press Figure 2 As shown, set up the device and connect accessories such as pumps, pipelines, and valves. Add 100 g of water to the 2# reactor and start stirring. Add 84.00 g (99%, 0.5 mol) of p-methyl-o-tert-butylphenol and 300 g (9.38 mol) of methanol to the 3# reactor, start stirring to completely dissolve it, and cool it to 0 - 5 °C with an ice-water bath.

[0096] Place the prepared raw material liquids on their respective electronic balances, connect the feeding pipelines, start the raw material pumps and the feeding pump for the pipeline reactor, and set the flow rates as follows: RM-1 is 1.46 g / min, RM-2 is 1.83 g / min, RM-3 is 2.5 g / min, RM-4 is 2.17 g / min. At the same time, adjust the valves so that the flow rate ratio of RM-4 in the pipeline reactors of the first to the third stages is 6:3:1. Keep the in-and-out flow balance of the 2# reactor and the pipeline reactors at all levels. Control the temperature of the 1# reactor at 100 - 110 °C, the temperature of the 2# reactor at 25 - 30 °C, the temperature of the pipeline reactors of the first to the third stages at 5 - 15 °C, and the temperature of the 3# reactor at 10 - 15 °C.

[0097] After the feeding of each raw material is completed, transfer all the materials in the 1# reactor, 2# reactor, and the pipeline reactor to the 3# reactor, continue the heat preservation reaction for 1 - 2 h, then filter, wash the filter cake three times with hot water at 70 - 80 °C, dry it, weigh it, and conduct tests. The test results are shown in Table 2.

[0098] Example 7 Synthesis of 2-(2'-hydroxy-5'-tert-octylphenyl)-benzotriazole (UV-329) parent compound

[0099] Take 69.76 g (99%, 0.5 mol) of o-nitroaniline in a round-bottom flask, heat it to 80 °C until it completely melts, keep it warm for use, and denote it as RM-1 (total mass 69.76 g);

[0100] Take 75.00 g (98%, 0.75 mol) of sulfuric acid and 100.00 g (5.56 mol) of water in a beaker, prepare a solution, and keep it warm at 70 °C for use, and denote it as RM-2 (total mass 175 g);

[0101] Take 150 g (8.33 mol) of water in a beaker for use, and denote it as RM-3 (total mass 150 g);

[0102] Take 42.00 g (98.5%, 0.6 mol) of sodium nitrite and 95 g (5.28 mol) of water in a beaker, prepare a solution for use, and denote it as RM-4 (total mass 137 g);

[0103] Take 60 g (99%, 1.5 mol) of sodium hydroxide and 180 g (10 mol) of water in a beaker, prepare a solution for use, and denote it as RM-5 (total mass 240 g).

[0104] According to Figure 2Set up the device as shown and connect accessories such as pumps, pipelines, and valves. Add 100 g of water to the 2# reactor and start stirring. Add 104.57 g (98.5%, 0.5 mol) of p-tert-octylphenol, 200 g (4.35 mol) of ethanol, 50 g (2.78 mol) of water, and 20 g (99%, 0.5 mol) of sodium hydroxide to the 3# reactor, start stirring to dissolve it, and cool it down to 0 - 5 °C with ice.

[0105] Place the prepared raw material liquids on their respective electronic balances, connect the feed pipelines, start the raw material pump and the feed pump of the pipeline reactor, and set the flow rates as follows: RM-1 is 1.16 g / min, RM-2 is 2.91 g / min, RM-3 is 2.5 g / min, RM-4 is 2.28 g / min. At the same time, adjust the valves so that the flow rate ratio of RM-4 in the pipeline reactors of the first to third stages is 6:3:1. Maintain the balance of the inlet and outlet flows of the 2# reactor and each stage of the pipeline reactor. Control the temperature of the 1# reactor at 80 - 90 °C, the temperature of the 2# reactor at 25 - 30 °C, the temperature of the pipeline reactors of the first to third stages at 5 - 15 °C, and the temperature of the 3# reactor at 0 - 5 °C. Adjust the addition time and flow rate of RM-5 to control the pH of the material in the 3# reactor to be 8 - 10.

[0106] After the feeding of each raw material is completed, transfer all the materials in the 1# reactor, 2# reactor, and pipeline reactor to the 3# reactor, continue the heat preservation reaction for 1 - 2 h, then filter, wash the filter cake three times with hot water at 70 - 80 °C, dry it, weigh it, and detect it. The detection results are shown in Table 2.

[0107] Example 8 Synthesis of 2-(2'-hydroxy-3',5'-di-tert-butylphenyl)-benzotriazole (UV-234) parent compound

[0108] Take 69.76 g (99%, 0.5 mol) of o-nitroaniline in a round-bottom flask, heat it to 80 °C to make it all melt, keep it warm for use, and record it as RM-1 (total mass 69.76 g);

[0109] Take 85.00 g (98%, 0.85 mol) of sulfuric acid and 100.00 g (5.56 mol) of water in a beaker, prepare a solution, and keep it warm at 70 °C for use, and record it as RM-2 (total mass 185 g);

[0110] Take 150 g (8.33 mol) of water in a beaker for use, and record it as RM-3 (total mass 150 g);

[0111] Take 42.00 g (98.5%, 0.6 mol) of sodium nitrite and 95 g (5.28 mol) of water in a beaker, prepare a solution for use, and record it as RM-4 (total mass 137 g).

[0112] Press Figure 2 Set up the device as shown, and connect accessories such as pumps, pipelines, and valves. Add 100 g of water to its Reactor 2, and start stirring. Add 160.00 g (98%, 0.47 mol) of 3,5-dicumylphenol, 300 g (9.38 mol) of ethanol, 50 g (2.78 mol) of water, and 100 g (99%, 2.5 mol) of sodium hydroxide to Reactor 3, start stirring to dissolve it, and cool it down to 0 - 5 °C with ice melting.

[0113] Place the prepared raw material liquids on their respective electronic balances, connect the feeding pipelines, start the raw material pump and the feeding pump of the pipeline reactor, and set the flow rates as follows: RM-1 is 1.16 g / min, RM-2 is 3.08 g / min, RM-3 is 2.5 g / min, RM-4 is 2.28 g / min. At the same time, adjust the valves so that the flow rate ratio of RM-4 in the pipeline reactors of the first to third stages is 6:3:1. Keep the in-and-out flow balance of Reactor 2 and each stage of the pipeline reactor. Control the temperature of Reactor 1 at 60 - 70 °C, the temperature of Reactor 2 at 25 - 30 °C, the temperature of the pipeline reactors of the first to third stages at 5 - 15 °C, and the temperature of Reactor 3 at 0 - 5 °C.

[0114] After the feeding of each raw material is completed, transfer all the materials in Reactor 1, Reactor 2, and the pipeline reactor to Reactor 3, continue the heat preservation reaction for 1 - 2 h, then filter, wash the filter cake three times with hot water at 70 - 80 °C, dry it, weigh it, and detect it. The detection results are shown in Table 2.

[0115] Synthesis of UV-P parent compound in Comparative Example 1 (batch process)

[0116] Add 100.00 g (98%, 1 mol) of sulfuric acid and 100.00 g (5.56 mol) of water to a 500 ml four-necked flask, then add 69.76 g (99%, 0.5 mol) of o-nitroaniline, heat up to dissolve, then add 150 g of water to precipitate o-amine salt, and cool it down to 0 - 5 °C. Then quickly add the sodium nitrite solution (an aqueous solution prepared from 42.00 g of sodium nitrite and 95 g of water), keep the reaction at 0 - 5 °C for 1 h, and then filter to obtain the diazonium solution for later use.

[0117] Add 55.00 g (98.5%, 0.5 mol) of p-cresol, 150 g (8.33 mol) of water, and 20 g (99%, 0.5 mol) of sodium hydroxide to a 1000 ml four-necked flask, start stirring to completely dissolve it, and cool it down to 0 - 5 °C with ice melting. Then dropwise add the prepared diazonium solution to it, and control the pH of the reaction system at 8 - 10 with a 25% sodium hydroxide aqueous solution. Control the temperature at 0 - 5 °C during the reaction process.

[0118] After the addition of the diazo solution is completed, continue the heat preservation reaction for 1 - 2 h, filter, wash the filter cake three times with hot water at 70 - 80 °C, dry, weigh, and detect. The detection results are shown in Table 2.

[0119] Synthesis of UV-P parent compound in Comparative Example 2

[0120] The sulfuric acid solution becomes 65.00 g of sulfuric acid (98%, 0.65 mol) and 50.00 g of water (2.78 mol), and the rest is the same as in Comparative Example 1; the detection results are shown in Table 2.

[0121] Synthesis of UV-P parent compound in Comparative Example 3

[0122] The amount of o-nitroaniline used becomes 76.74 g (99%, 0.55 mol), and the sulfuric acid solution becomes 137.50 g of sulfuric acid (98%, 1.375 mol) and 137.5 g of water (7.64 mol), and the rest is the same as in Comparative Example 1; the detection results are shown in Table 2.

[0123] Synthesis of UV-326 parent compound in Comparative Example 4 (batch process)

[0124] Add 100.00 g of sulfuric acid (98%, 1.0 mol) and 10.00 g of water (0.56 mol) to a 500 ml four-necked flask, then add 87.59 g of p-chloro-o-nitroaniline (98.5%, 0.5 mol), heat up to dissolve, then add 150 g of water to precipitate the o-amine salt, and cool down to 0 - 5 °C. Then quickly add the sodium nitrite solution (an aqueous solution prepared from 40.00 g of sodium nitrite and 90 g of water), keep the reaction at 0 - 5 °C for 1 h, and then filter to obtain the diazo solution for use.

[0125] Add 84.00 g of p-methyl-o-tert-butylphenol (99%, 0.5 mol) and 300 g of methanol (9.38 mol) to a 1000 ml four-necked flask, start stirring to completely dissolve it, and cool it down to 0 - 5 °C with ice. Then add the prepared diazo solution dropwise, and control the temperature at 0 - 5 °C during the reaction process.

[0126] After the addition of the diazo solution is completed, continue the heat preservation reaction for 1 - 2 h, filter, wash the filter cake three times with hot water at 70 - 80 °C, dry, weigh, and detect. The detection results are shown in Table 2.

[0127] Synthesis of UV-326 parent compound in Comparative Example 5

[0128] The sulfuric acid solution becomes 120.00 g of sulfuric acid (98%, 1.2 mol) and 12.00 g of water (0.67 mol), and the rest is the same as in Comparative Example 4; the detection results are shown in Table 2.

[0129] Synthesis of UV-329 parent compound in Comparative Example 6 (batch process)

[0130] Add 100.00 g of sulfuric acid (98%, 1 mol) and 100.00 g of water (5.56 mol) into a 500 ml four-necked flask, then add 69.76 g of o-nitroaniline (99%, 0.5 mol). Heat up to dissolve, then add 150 g of water to precipitate o-amine salt, and cool down to 0 - 5 °C. Then quickly add sodium nitrite solution (an aqueous solution prepared from 42.00 g of sodium nitrite and 95 g of water), keep the temperature at 0 - 5 °C for reaction for 1 h, and then filter to obtain the diazonium solution for later use.

[0131] Add 104.57 g of p-tert-octylphenol (98.5%, 0.5 mol), 200 g of ethanol (4.35 mol), 50 g of water (2.78 mol) and 20 g of sodium hydroxide (99%, 0.5 mol) into a 1000 ml four-necked flask. Start stirring to completely dissolve it, and cool it down to 0 - 5 °C with ice bath. Then dropwise add the prepared diazonium solution into it, and control the pH of the reaction system to be 8 - 10 with 25% sodium hydroxide aqueous solution. Keep the temperature at 0 - 5 °C during the reaction process.

[0132] After the addition of the diazonium solution is completed, continue to keep the temperature for reaction for 1 - 2 h, then filter, wash the filter cake three times with hot water at 70 - 80 °C, dry it, weigh it, and detect. The detection results are shown in Table 2.

[0133] Synthesis of UV-234 parent compound in Comparative Example 7 (batch process)

[0134] Add 85.00 g of sulfuric acid (98%, 0.85 mol) and 100.00 g of water (5.56 mol) into a 500 ml four-necked flask, then add 69.76 g of o-nitroaniline (99%, 0.5 mol). Heat up to dissolve, then add 150 g of water to precipitate o-amine salt, and cool down to 0 - 5 °C. Then quickly add sodium nitrite solution (an aqueous solution prepared from 42.00 g of sodium nitrite and 95 g of water), keep the temperature at 0 - 5 °C for reaction for 1 h, and then filter to obtain the diazonium solution for later use.

[0135] Add 160 g of 3,5-dicumylphenol (98%, 0.47 mol), 300 g of ethanol (9.83 mol), 50 g of water (2.78 mol) and 100 g of sodium hydroxide (99%, 2.5 mol) into a 1000 ml four-necked flask. Start stirring to completely dissolve it, and cool it down to 0 - 5 °C with ice bath. Then dropwise add the prepared diazonium solution into it, and keep the temperature at 0 - 5 °C during the reaction process.

[0136] After the addition of the diazonium solution is completed, continue to keep the temperature for reaction for 1 - 2 h, then filter, wash the filter cake three times with hot water at 70 - 80 °C, dry it, weigh it, and detect. The detection results are shown in Table 2.

[0137] Synthesis of UV-234 Parent Compound in Comparative Example 8

[0138] The sulfuric acid solution becomes 100.00 g of sulfuric acid (98%, 1 mol) and 100.00 g of water (5.56 mol). The amount of 5-nitroaniline used becomes 80.92 g (99%, 0.58 mol). The rest is the same as in Comparative Example 7. The test results

[0139] See Table 2.

[0140] Test Results of Examples and Comparative Examples in Table 2

[0141] Example Product content (%) Product weight yield (%) Phenol residue (%) Example 1 95.8 94.5 0.15 Example 2 93.6 93.7 0.28 Example 3 94.9 95.2 0.10 Example 4 96.2 95.0 0.08 Example 5 93.1 92.5 1.15 Example 6 97.1 94.3 0.12 Example 7 94.3 95.1 0.09 Example 8 93.6 95.2 0.89 Comparative Example 1 90.7 91.8 1.43 Comparative Example 2 88.5 89.5 2.04 Comparative Example 3 93.4 93.2 0.65 Comparative Example 4 92.5 90.1 2.79 Comparative Example 5 96.5 93.2 1.21 Comparative Example 6 87.5 92.2 3.54 Comparative Example 7 88.6 84.3 5.21 Comparative Example 8 92.4 93.1 2.12

[0142] It can be seen from the results in Table 2 that under the same raw material dosage, the product yield obtained by the continuous preparation method of the present invention is significantly higher than that of the batch process (Comparative Examples 1, 2, 4, 6, and 7), and the phenol residue is also much lower than that of the batch process.

[0143] In Comparative Examples 3, 5, and 8, the amount of o-amine raw material and / or sulfuric acid was increased, and the reaction results were improved to a certain extent, but they were still significantly inferior to the continuous preparation method of the present invention. This is because although excessive raw materials can increase the product yield, they are more likely to cause side reactions, which affect the product purity, and more difficult-to-treat waste salts will also be generated.

[0144] Unless otherwise specified, the terms used in the present invention have the meanings commonly understood by those skilled in the art.

[0145] The embodiments described in the present invention are for illustrative purposes only and are not intended to limit the protection scope of the present invention. Those skilled in the art can make various other substitutions, changes, and improvements within the scope of the present invention. Therefore, the present invention is not limited to the above embodiments and is only defined by the claims.

Claims

1. A continuous preparation method of a benzotriazole-based light stabilizer intermediate, characterized in that, Comprising the following steps: S1: Reacting a molten o - amine as shown in formula (I) with an acid solution to obtain a first reaction solution; S2: Atomizing and spraying the first reaction solution into water or an organic solvent to obtain a slurry containing o - amine salt; S3: Subjecting the slurry to a diazotization reaction with a diazotizing reagent successively through a three - stage pipe reactor to obtain a second reaction solution containing a diazonium salt as shown in formula (II). According to the flow direction of the slurry, the mass distribution ratio of the diazotizing reagent in the three - stage pipe reactor is 40 - 70%:20 - 50%:5 - 15%; S4: Adding the second reaction solution to a phenol solution as shown in formula (I') to carry out a coupling reaction, thereby preparing a benzotriazole - type light stabilizer intermediate as shown in formula (III); Wherein, R1 represents hydrogen, a halogen, or a substituted or unsubstituted C1 - C6 alkyl; R2 represents hydrogen, a substituted or unsubstituted C1 - C10 alkyl, a substituted or unsubstituted C1 - C6 alkoxy, or a substituted or unsubstituted C6 - C20 aryl; R3 represents a substituted or unsubstituted C1 - C12 alkyl, a substituted or unsubstituted C1 - C6 alkoxy, or a substituted or unsubstituted C6 - C20 aryl; When the above groups are substituted groups, the number of substituents is 1, 2, or 3, and each independently selected from a halogen, -COO(C1 - C6 alkyl), C1 - C6 alkyl, C1 - C4 alkoxy, or C6 - C12 aryl.

2. The continuous preparation method according to claim 1, characterized in that, Said R1 represents hydrogen or chlorine; and / or Said R2 represents hydrogen, a C1 - C8 alkyl, benzyl, or cumyl; and / or Said R3 represents hydrogen, a C1 - C10 alkyl, benzyl, cumyl, or -(C1 - C4 alkylene)COO(C1 - C4 alkyl).

3. The continuous preparation method according to claim 1 or 2, characterized in that, Said acid solution is sulfuric acid or hydrochloric acid solution, and its mass concentration is 35 - 90%; and / or The molar ratio of the acid in the acid solution to the o - amine is 1 - 5:

1.

4. The continuous preparation method according to claim 1 or 2, characterized in that, The reaction temperature for the reaction of the o - amine with the acid solution is 60 - 120 °C.

5. The continuous preparation method according to claim 1 or 2, characterized in that, Said step S2 is further: Atomizing and spraying the first reaction solution into a container pre - added with the water or the organic solvent to obtain a slurry containing o - amine salt.

6. The continuous preparation method according to claim 5, characterized in that, While atomizing and spraying the first reaction solution, atomizing and spraying the water or the organic solvent into the container.

7. The continuous preparation method according to claim 6, wherein, Said organic solvent is selected from one or more of methanol, ethanol, isopropanol, C8 - C12 linear alkanes, toluene, and xylene.

8. The continuous preparation method according to claim 1 or 2, characterized in that, Said diazotizing reagent is sodium nitrite solution, and its mass concentration is 10 - 50%.

9. The continuous preparation method according to claim 8, wherein, The molar ratio of the diazotizing reagent to the o - amine is 1 - 1.3:

1.

10. The continuous preparation method according to claim 1 or 2, characterized in that, The temperature inside the pipe reactor is 0 - 30 °C.

11. The continuous preparation method according to claim 1 or 2, characterized in that, According to the flow direction of the slurry, the mass distribution ratio of the diazotizing reagent in the three - stage pipe reactor is 50 - 60%:30 - 40%:8 - 12%.

12. The continuous preparation method according to claim 1 or 2, characterized in that, Said phenol solution is an aqueous solution or an organic solvent solution of phenol; and / or The reaction temperature of the coupling reaction is 0 - 30 °C.

13. The continuous preparation method according to claim 12, characterized in that, Said organic solvent is selected from one or more of methanol, ethanol, and isopropanol.

14. A preparation method of a benzotriazole light stabilizer, characterized in that, The intermediate of the benzotriazole light stabilizer shown in formula (III) is prepared by the continuous preparation method according to any one of claims 1-13, and then the benzotriazole light stabilizer shown in formula (IV) is prepared through a reduction reaction; wherein, R1, R2 and R3 are each independently defined as in any one of claims 1-13.

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