A photoinitiator, a preparation method thereof, an ultraviolet light-cured resin, and an ultraviolet light-cured inner liner hose

Abstract

The application discloses a photoinitiator and a preparation method thereof, an ultraviolet light curing resin, and an ultraviolet light curing inner lining hose. o The preparation method of the photoinitiator comprises the following steps: dissolving white solid product C in triethylamine dichloromethane to obtain a C solution, dissolving TPO-L acyl halide in an organic solvent to obtain a TPO-L acyl halide solution, adding the TPO-L acyl halide solution into the C solution drop by drop when the temperature of the C solution is 0 o stirring for 20-28 hours at room temperature, quenching the reaction, separating an organic phase, extracting a water phase, washing, filtering and purifying combined organic phases, and obtaining a trifunctional photoinitiator. The photoinitiator synthesized in the application contains four active groups, has high activity, improves the transfer efficiency of free radicals, is suitable for the curing of thick film products, has low migration and volatility, has low odor and toxicity, has good solubility in various resin monomers and diluents, and is especially suitable for the curing of ultraviolet light curing inner lining hoses.

Description

Technical Field

[0001] This invention relates to the field of photoinitiators, and in particular to a photoinitiator and its preparation method, a UV-curable resin, and a UV-curable inner lining tube. Background Technology

[0002] UV-curable lined hoses are composed of glass fiber and resin matrix. Under the action of photoinitiator, the resin can generate active free radicals after being irradiated by ultraviolet light, thereby promoting the polymerization and cross-linking between molecules to form a new composite resin lining hose with high strength. This type of UV-curable lined hose for whole-section trenchless pipeline repair has excellent macroscopic mechanical properties. During the curing repair, there is less wastewater and exhaust gas emission. Unlike thermosetting repair, the UV-curable lined hose curing process does not require hot water or steam to heat the lining hose, saving energy consumption. It is suitable for the repair of various types of underground pipelines and has become one of the mainstream products for trenchless underground pipeline repair.

[0003] Currently, the mainstream photoinitiators used in UV-cured inner lining hoses include 2-hydroxy-2-methyl-1-phenyl-1-propanone (1173), 1-hydroxycyclohexylphenyl methyl ketone (184), and deep-curing initiators such as ethyl 2,4,6-trimethylbenzoylphenylphosphonate (TPO-L), 2,4,6-trimethylbenzoyl-diphenylphosphine oxide (TPO), and phenylbis(2,4,6-trimethylbenzoyl)phosphine oxide (819). Among them, 1173 and TPO-L are highly efficient initiators with high initiation activity. Since they are liquid, they have good compatibility with the resin system and do not produce obvious yellowing after curing. However, it also has significant problems. Photoinitiators that do not decompose or participate in polymerization during the curing process, as well as photoinitiator fragments, are very easy to migrate and volatilize during use. This manifests as resin aging, abnormal irritating odors, and even toxicity. These irritating odors and toxicity not only affect the health of relevant workers but also cause environmental pollution through underground pipe networks.

[0004] Patent CN114394990A discloses an asymmetric macromolecular photoinitiator containing both α-aminoketone and organosilicon, its preparation method, and its applications, belonging to the field of new materials and organic chemicals technology. This asymmetric macromolecular photoinitiator I, containing both α-aminoketone and organosilicon, is prepared by a thiol-olefin click reaction of a small molecule photoinitiator PI containing double bonds (α-aminoketone), an organosilicon compound A containing double bonds, and a polythiol compound B. It not only overcomes the shortcomings of existing photoinitiators, exhibiting low migration and low irritating odor, but also demonstrates floating properties in common resins and good solubility in silicone resins.

[0005] Currently, the thickness of UV-curable inner lining tubes produced by existing technologies is insufficient, requiring compounding with thermal initiators to increase the thickness. While the photoinitiator developed in patent CN114394990A addresses the issues of low migration and low irritant odor associated with small-molecule photoinitiators, the thick UV-curable inner lining tubes produced by this patent require compounding with a thermal initiator. However, the presence of the thermal initiator necessitates low-temperature conditions for the transportation and storage of the inner lining tubes, increasing costs. Furthermore, there is a risk of premature curing during summer construction. Summary of the Invention

[0006] The technical problem to be solved by the present invention is to provide a photoinitiator and its preparation method to address the shortcomings of the existing technology. This method not only solves the problems of low migration and low irritating odor of small molecule photoinitiators, but also allows for the production of UV-cured inner lining hoses with a large curing thickness without the addition of thermal initiators.

[0007] This invention also discloses a UV-curable resin and a UV-curable inner lining hose, which not only solves the problems of low migration and low irritating odor of small molecule photoinitiators, but also allows for the production of UV-curable inner lining hoses with a large curing thickness without the addition of thermal initiators.

[0008] To solve the above-mentioned technical problems, the technical solution adopted by the present invention is: a method for preparing a photoinitiator, comprising the following steps:

[0009] After esterification of 4-(carboxymethyl)-3,5-dihydroxybenzoic acid and 2-hydroxy-2-methyl-1-phenyl-1-propanone, the organic phase was washed, separated, dried, and purified to obtain a white solid product C.

[0010] TPO-L is subjected to an acyl halide reaction to obtain TPO-L acyl halides;

[0011] The white solid product C was dissolved in dichloromethane containing triethylamine to obtain a C solution. The TPO-L acyl halide was dissolved in an organic solvent to obtain a TPO-L acyl halide solution. At 0°C, the TPO-L acyl halide solution was added dropwise to the C solution. The mixture was stirred at room temperature for 20-28 hours to quench the reaction. After separating the organic phase, the aqueous phase was extracted. The combined organic phases were washed, filtered, and purified to obtain a tetrafunctional photoinitiator.

[0012] This invention provides a novel macromolecular photoinitiator that ensures initiation activity while reducing the migration and volatility of the photoinitiator. It exhibits superior overall performance, including low odor, low toxicity, and excellent resin compatibility, making it suitable for use in UV-curable flexible tubes. The photoinitiator HHTT, a tetrafunctional photoinitiator containing two molecules of 1173 and two molecules of TPO-L, is obtained through esterification of 1173 and TPO-L acyl halides with 4-(carboxymethyl)-3,5-dihydroxybenzoic acid. The HHTT photoinitiator contains four active groups, exhibiting high activity and improved free radical transport efficiency. It combines the excellent surface curing properties of 1173 with the deep curing properties of TPO-L, offering significant advantages in preparing thick, high-quality UV-curable inner-lined flexible tubes.

[0013] In a preferred embodiment of the present invention, the method for preparing the white solid product C includes the following steps:

[0014] Under anhydrous and oxygen-free conditions, 4-(carboxymethyl)-3,5-dihydroxybenzoic acid and 2-hydroxy-2-methyl-1-phenyl-1-propanone were dissolved in an organic solvent, and 4-dimethylaminopyridine and 1-(3-dimethylaminopropyl-3-ethylcarbodiimide hydrochloride) were added. The reaction mixture was stirred at 35-45°C for 8-16 hours. After the reaction was completed, the organic phase was washed, separated, dried, and purified to obtain a white solid product C.

[0015] In a preferred embodiment of the present invention, the white solid product C is prepared by washing with saturated ammonium chloride aqueous solution and saturated brine in sequence, separating the organic phase and drying it, and then separating the crude product by column chromatography with an eluent to obtain the white solid product.

[0016] In the preparation of the white solid product C, the organic solvent is a mixed solution of triethylamine and dichloromethane. The volume ratio of the mixed solution of triethylamine and dichloromethane is 2:60-80.

[0017] The eluent is a mixed solvent of petroleum ether and ethyl acetate in a volume ratio of 1-3:1.

[0018] In a preferred embodiment of the present invention, the method for preparing 4-(carboxymethyl)-3,5-dihydroxybenzoic acid includes the following steps:

[0019] Potassium fluoride was added to an organic solution of 3-oxoglutaric acid dimethyl ester, and the mixture was heated under reflux and concentrated under vacuum. The product was then poured into ice water for extraction, washing, drying, concentration, and recrystallization to obtain 2,4-dihydroxy-6-(2-methoxy-2-oxoethyl)isophthalate dimethyl ester.

[0020] Dimethyl 2,4-dihydroxy-6-(2-methoxy-2-oxoethyl)isophthalate was dissolved in concentrated sulfuric acid, heated to 60-70℃ and stirred to react. After the reaction was completed, it was poured into ice water, filtered to remove solid byproducts, and then extracted, washed, dried and concentrated to obtain 4-(carboxymethyl)-3,5-dihydroxybenzoic acid.

[0021] In a preferred embodiment of the present invention, potassium fluoride is added to an organic solution of dimethyl 3-oxoglutarate, and the mixture is heated under reflux for 20-28 hours.

[0022] In a preferred embodiment of the present invention, the method for preparing TPO-L acyl halide includes the following steps:

[0023] At room temperature, TPO-L is dissolved in an organic solvent, anhydrous sodium iodide is added, and the reaction yields a pale orange solution. The solution is heated to 50-70°C and stirred for 20-28 hours. The precipitate is then collected, filtered, and washed to obtain a white solid sodium salt of TPO-L.

[0024] Dissolve white solid TPO-L sodium salt in distilled water, adjust the pH of the solution to 1-2 with sulfuric acid, extract, and distill the organic phase under reduced pressure to obtain 2,4,6-trimethylbenzoylphenylphosphonic acid;

[0025] 2,4,6-Trimethylbenzoylphenylphosphonic acid was dissolved in an organic solvent, oxaloyl chloride was added and stirred, and a clear solution was prepared by reaction. The solution was then distilled under reduced pressure, and anhydrous toluene was added to the remaining oily substance. The solution was then distilled again at 45-55℃ to obtain a light brown oily TPO-L acyl halide.

[0026] In a preferred embodiment of the present invention, in the preparation method of TPO-L acyl halide, the stirring time for adding oxalyl chloride is 16-24 hours.

[0027] Dissolve TPO-L in an organic solvent, add anhydrous sodium iodide, and react to obtain a pale orange solution. The reaction time is 8-12 minutes.

[0028] The present invention also discloses a photoinitiator prepared by the above-described preparation method.

[0029] The present invention also discloses an ultraviolet curable resin, comprising the following raw materials in parts by weight: 80-100 parts of unsaturated resin, 2 parts of filler, and 1-3 parts of the photoinitiator.

[0030] The unsaturated resin comprises the following raw materials in parts by weight: 80-100 parts of unsaturated polyester resin and 30-40 parts of styrene.

[0031] The UV-curable resin prepared by this invention improves the photoinitiator's ability to utilize light energy, resulting in higher initiation activity, faster polymerization speed, and increased thickness.

[0032] The filler is selected from silica.

[0033] The present invention also discloses a UV-curable inner lining hose, which is made by injecting the above-mentioned UV-curable resin into a dry material tube.

[0034] The preparation method of photoinitiator specifically includes the following steps:

[0035] Step 1: Preparation of the linking group 4-(carboxymethyl)-3,5-dihydroxybenzoic acid

[0036] An organic solution (toluene or benzene) of dimethyl 3-oxoglutarate was added to a two-necked flask equipped with a Dean-Stark apparatus, along with potassium fluoride. The mixture was heated under reflux for 24 hours. After concentration under vacuum, the solution was poured into ice water and extracted with chloroform. The organic phase was washed with water, dried, concentrated, and recrystallized in diethyl ether-hexane to give dimethyl 2,4-dihydroxy-6-(2-methoxy-2-oxoethyl)isophthalate. The resulting product was dissolved in concentrated sulfuric acid and heated to 65°C with stirring overnight. After the reaction was complete, the solution was poured into ice water, filtered to remove solid byproducts, and the remaining filtrate was extracted with ethyl acetate. The organic phase was washed with saturated sodium chloride solution, dried, concentrated, and recrystallized in chloroform-ethyl acetate to give 4-(carboxymethyl)-3,5-dihydroxybenzoic acid.

[0037] Step 2: Preparation of TPO-L acyl halides

[0038] At room temperature, TPO-L was dissolved in 2-butanone, and anhydrous sodium iodide was added with stirring. After 10 minutes, a pale orange solution was obtained. This solution was heated to 60°C in an oil bath and stirred for 24 hours. About 10 minutes after the product began to precipitate, the suspension was cooled to room temperature, filtered, washed with ice-cold 2-butanone and diethyl ether, and air-dried to obtain a white solid TPO-L sodium salt. The TPO-L sodium salt was vigorously stirred in distilled water at room temperature, and diluted sulfuric acid was added to adjust the pH of the solution to approximately 1, with the precipitate added gradually during this process. Ethyl acetate was added to the resulting suspension, and the phases were separated after vigorous mixing. The aqueous phase was further extracted with ethyl acetate, and the organic phases were combined, washed with distilled water, dried, and distilled under reduced pressure to obtain 2,4,6-trimethylbenzoylphenylphosphonic acid. 2,4,6-trimethylbenzoylphenylphosphonic acid was dissolved in dichloromethane and stirred at room temperature, with oxaloyl chloride added in small portions. The mixture was stirred at room temperature for 20 hours, during which time it gradually became a clear solution. Distilled under reduced pressure, anhydrous toluene (50 mL) was added to the remaining oily substance, and the mixture was distilled again at 50 °C to dryness to obtain a light brown oily TPO-L acyl halide.

[0039] Step 3:

[0040] Under anhydrous and oxygen-free conditions, the product from step 1 and 1173 were dissolved in a mixed solution of anhydrous triethylamine and dichloromethane. Then, 4-dimethylaminopyridine and 1-(3-dimethylaminopropyl-3-ethylcarbodiimide hydrochloride) were added, and the reaction mixture was stirred at 40°C for 12 hours. After the reaction was complete, the mixture was washed successively with saturated ammonium chloride aqueous solution and saturated brine. The organic phase was separated and dried, and all volatiles were removed by rotary evaporation. The crude product was separated by column chromatography using petroleum ether:ethyl acetate = 2:1 eluent to obtain a white solid product.

[0041] Step 4: Dissolve the TPO-L acyl halide obtained in Step 2 in 10 mL of dichloromethane, and add it dropwise to dichloromethane containing the product from Step 3 and triethylamine at 0 °C. Stir the mixture at room temperature for 24 hours. After quenching the reaction with saturated sodium bicarbonate aqueous solution, transfer the mixture to a separatory funnel to separate the organic phase. Extract the aqueous phase with dichloromethane. Combine the organic phases and wash with saturated brine, dry and filter, and then remove the solvent under vacuum. Purify the crude product by column chromatography using petroleum ether:ethyl acetate = 3:1 as the eluent to obtain a macromolecular photoinitiator for UV-curable inner lining tubing.

[0042] The reaction equation for the photoinitiator in this invention is as follows:

[0043]

[0044] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0045] (1) This invention combines two molecules of 1173 and two molecules of TPO-L to prepare a tetrafunctional macromolecular photoinitiator. The increased functionality enhances the photoinitiator's light absorption capacity and its ability to utilize light energy, resulting in higher initiation activity and faster polymerization. Under the same curing conditions, the resin containing the photoinitiator of this invention has the largest cured thickness. Under 600W ultraviolet light irradiation, the curing time for a 600mm diameter, 6mm thick ultraviolet-cured flexible tube is 4 minutes, demonstrating fast curing speed and excellent curing effect.

[0046] (2) Increasing the molecular weight of photoinitiators increases their steric hindrance, hindering the termination of coupling between free radicals, thereby increasing the lifetime of primary free radicals and improving the free radical transport efficiency. At the same time, high molecular weight photoinitiators are less volatile than small molecular weight photoinitiators, thus having the advantage of low odor; the initiator groups are less likely to precipitate or migrate, resulting in lower toxicity.

[0047] (3) This macromolecular structure is less likely to produce quinone structural substances after ultraviolet light irradiation, which can reduce resin yellowing. Detailed Implementation

[0048] Example 1: Preparation of HHTT, a photoinitiator for UV-curable flexible tubes

[0049] (1) To a two-necked flask equipped with a Dean-Stark apparatus, add 500 mL of a toluene solution containing 40 g (230 mmol) of dimethyl 3-oxoglutarate and 29 g (500 mmol) of potassium fluoride. Heat under reflux for 24 hours. Concentrate under vacuum and pour into ice water. Extract with chloroform. Wash the organic phase with water, dry, concentrate, and recrystallize in diethyl ether-hexane solution to obtain 25 g of white needle-like crystals of dimethyl 2,4-dihydroxy-6-(2-methoxy-2-oxoethyl)isophthalate. Dissolve the obtained product in 50 mL of concentrated sulfuric acid and heat to 65 °C with stirring overnight. After the reaction is complete, pour into ice water, filter to remove solid byproducts, and extract the remaining filtrate with ethyl acetate. Wash the organic phase with saturated sodium chloride solution, dry and concentrate. Recrystallize the obtained substance in chloroform-ethyl acetate to obtain 11 g of white crystals of 4-(carboxymethyl)-3,5-dihydroxybenzoic acid.

[0050] (2) At room temperature, 15 g (47.4 mmol) of TPO-L was dissolved in 80 mL of 2-butanone, and 7.8 g (52.2 mmol) of anhydrous sodium iodide was added with stirring. After 10 minutes, a pale orange solution was obtained. The solution was heated to 60 °C in an oil bath and stirred for 24 hours. About 10 minutes after the product began to precipitate, the suspension was cooled to room temperature, filtered, washed with ice-cold 2-butanone and diethyl ether, and air-dried to obtain 11.8 g of white solid TPO-L sodium salt. 9.4 g (30.2 mmol) of TPO-L sodium salt was vigorously stirred in distilled water at room temperature, and diluted sulfuric acid (0.5 M) was added to adjust the pH of the solution to about 1, with the precipitate added gradually during this process. Ethyl acetate was added to the resulting suspension, and the phases were separated after vigorous mixing. The aqueous phase was extracted with ethyl acetate, the organic phases were combined, washed with distilled water and dried, and distilled under reduced pressure to obtain 8 g of pale yellow solid 2,4,6-trimethylbenzoylphenylphosphonic acid. 8 g (27.7 mmol) of 2,4,6-trimethylbenzoylphenylphosphonic acid was dissolved in 60 mL of dichloromethane and stirred at room temperature. 7 g (55.4 mmol) of oxaloyl chloride was added in small portions. The mixture was stirred at room temperature for 20 hours, during which time it gradually became a clear solution. The solution was distilled under reduced pressure, and anhydrous toluene (50 mL) was added to the remaining oil. The mixture was then redistilled at 50 °C to dryness, yielding 8.3 g of a pale brown oily TPO-L acyl halide.

[0051] (3) Under anhydrous and anaerobic conditions, 2.33 g (11 mmol) of 4-(carboxymethyl)-3,5-dihydroxybenzoic acid and 4.83 g (30 mmol) of 1173 were dissolved in a mixture of 2 mL of anhydrous triethylamine and 70 mL of dichloromethane. Then, 0.37 g (3 mmol) of 4-dimethylaminopyridine and 6.33 g (33 mmol) of 1-(3-dimethylaminopropyl-3-ethylcarbodiimide hydrochloride) were added, and the reaction mixture was stirred at 40 °C for 12 hours. After the reaction was completed, the reactants were washed successively with saturated ammonium chloride aqueous solution and saturated brine. The organic phase was separated and dried over anhydrous sodium sulfate to remove all volatiles. The crude product was separated by column chromatography using petroleum ether:ethyl acetate = 2:1 as eluent to obtain 4.56 g of a white solid product.

[0052] (4) 5.44 g (17.7 mmol) of TPO-L acyl halide was dissolved in 20 mL of dichloromethane, and then added dropwise at 0 °C to 50 mL of dichloromethane containing 3.03 g (6 mmol) of the above-obtained compound and 2.5 mL of triethylamine. The mixture was stirred at room temperature for 24 hours. After quenching the reaction with saturated sodium bicarbonate aqueous solution, the mixture was transferred to a separatory funnel to separate the organic phase, and the aqueous phase was extracted with dichloromethane. The combined organic phases were washed with saturated brine, dried, filtered, and the solvent was removed under vacuum. The crude product was purified by column chromatography using petroleum ether:ethyl acetate = 3:1 as the eluent to give 4.26 g of product.

[0053] Example 2: The prepared initiator was applied to a UV-curable inner lining tube. In this specific example, three 150mL transparent containers were prepared, and 80g of unsaturated polyester resin was weighed into each container. Photoinitiator 1173, TPO-L, and HHTT were added respectively, at a mass percentage of 2% of the unsaturated polyester resin mass. After uniform stirring for 15 minutes, air bubbles were removed under vacuum. The liquid level in each of the three containers was 30mm. The containers were placed on a lifting platform 30cm away from the UV lamp and irradiated with a 1000W UV lamp for 4 minutes. The thickness of the cured product was measured from the side of the containers using a ruler. A current drawback of UV-curable materials is insufficient curing depth; increasing the thickness of the UV-curable material can improve its mechanical properties.

[0054] 1173 4.0 TPO-L 8.0 HHTT 11.0

[0055] Example 3: The prepared photoinitiator was applied to a UV-cured inner lining hose. In this specific example, 100 parts by weight of unsaturated polyester resin, 35 parts by weight of styrene, 2 parts by weight of photoinitiator, and 2 parts by weight of silica were mixed at high speed to obtain a resin mother liquor for later use. In this example, styrene and silica were added to prepare the hose.

[0056] A dry material hose is made from an UV-resistant film, a resin impermeable membrane, an inner membrane, and six layers of fiberglass cloth. The aforementioned resin mother liquor is injected into the dry material hose using a vacuum infusion process, and then extruded using a resin roller to ensure the resin fully and evenly impregnates the fiberglass cloth, thus creating a UV-curable inner lining hose.

[0057] The aforementioned UV-curable inner lining tubing is cured under UV lamp radiation, with a UV lamp power of 600W and a distance of 30cm from the UV lamp.

[0058] Curing time measurement: The time it takes for the hose to reach its highest temperature during the curing process.

[0059] Hardness testing: The hardness of the front and back sides of the UV-curable tubing was tested using a Barcol hardness tester.

[0060] Odor testing: The nose is used to determine the intensity of an odor. A lower number indicates a weaker odor.

[0061] The test results for the photoinitiator HHTT are as follows (photoinitiators 1173 and TPO-L were selected as comparison items).

[0062]

[0063] As can be seen from the data in the table, the photoinitiator HHTT of this invention performs better than photoinitiators 1173 and TPO-L in the performance test.

[0064] It has a faster curing speed and curing thickness, and the large molecular structure also makes the odor less after curing.

Claims

1. A method for preparing a photoinitiator, characterized in that... Includes the following steps: (1) Add 500 mL of a toluene solution containing 40 g of dimethyl 3-oxoglutarate to a two-necked flask equipped with a Dean-Stark apparatus, along with 29 g of potassium fluoride. Heat under reflux for 24 hours. Concentrate under vacuum and pour into ice water. Extract with chloroform. Wash the organic phase with water, dry, concentrate, and recrystallize in diethyl ether-hexane solution to obtain 25 g of white needle-like crystals of dimethyl 2,4-dihydroxy-6-(2-methoxy-2-oxoethyl)isophthalate. Dissolve the obtained product in 50 mL of concentrated sulfuric acid and heat to 65 °C. o C. Stir overnight; after the reaction is complete, pour it into ice water, filter to remove solid byproducts, and extract the remaining filtrate with ethyl acetate; wash the organic phase with saturated sodium chloride solution, dry and concentrate, and recrystallize the obtained substance in chloroform-ethyl acetate to give 11g of white crystals of 4-(carboxymethyl)-3,5-dihydroxybenzoic acid. (2) At room temperature, 15 g of TPO-L was dissolved in 80 mL of 2-butanone, and 7.8 g of anhydrous sodium iodide was added with stirring. After 10 minutes, a pale orange solution was obtained. The solution was heated to 60 °C in an oil bath and stirred for 24 hours. After the product began to precipitate, the suspension was cooled to room temperature and filtered. It was washed with ice-cold 2-butanone and diethyl ether, and air-dried to obtain 11.8 g of white solid TPO-L sodium salt. 9.4 g of TPO-L sodium salt was stirred vigorously in distilled water at room temperature, and 0.5 M diluted sulfuric acid was added to bring the pH of the solution to 1. During this period, the precipitate was gradually added. Ethyl acetate was added to the obtained suspension, and the phases were separated after vigorous mixing. The aqueous phase was extracted with ethyl acetate separately, the organic phases were combined, washed with distilled water and dried, and distilled under reduced pressure to obtain 8 g of pale yellow solid 2,4,6-trimethylbenzoylphenylphosphonic acid. 8 g of TPO-L sodium salt was then added to the solution. 2,4,6-Trimethylbenzoylphenylphosphonic acid was dissolved in 60 mL of dichloromethane and stirred at room temperature. 7 g of oxaloyl chloride was added in small portions. The mixture was stirred at room temperature for 20 hours, during which time it gradually became a clear solution. The mixture was distilled under reduced pressure, and 50 mL of anhydrous toluene was added to the remaining oil. The mixture was then distilled again at 50 °C to dryness to give 8.3 g of light brown oily TPO-L acyl halide. (3) Under anhydrous and oxygen-free conditions, 2.33 g of 4-(carboxymethyl)-3,5-dihydroxybenzoic acid and 4.83 g of 1173 were dissolved in a mixture of 2 mL of anhydrous triethylamine and 70 mL of dichloromethane; then 0.37 g of 4-dimethylaminopyridine and 6.33 g of 1-(3-dimethylaminopropyl-3-ethylcarbodiimide hydrochloride) were added, and the reaction mixture was heated at 40 °C. o Stirred at C for 12 hours; after the reaction was completed, the reactants were washed successively with saturated ammonium chloride aqueous solution and saturated brine; the organic phase was separated and dried with anhydrous sodium sulfate to remove all volatiles; the crude product was separated by column chromatography with petroleum ether: ethyl acetate = 2:1 eluent to obtain 4.56 g of white solid product; (4) Dissolve 5.44 g of TPO-L acyl halide in 20 mL of dichloromethane, and at 0 o Add the above-obtained compound (3.03 g) and 2.5 mL of triethylamine dropwise to 50 mL of dichloromethane at room temperature; stir the mixture at room temperature for 24 hours; quench the reaction with saturated sodium bicarbonate aqueous solution, transfer the mixture to a separatory funnel, separate the organic phase, and extract the aqueous phase with dichloromethane; combine the organic phases and wash with saturated brine, dry and filter, and then remove the solvent under vacuum; purify the crude product by column chromatography using petroleum ether:ethyl acetate = 3:1 as eluent to give 4.26 g of product; The structural formula of the product is shown below: 。 2. A photoinitiator prepared using the preparation method of claim 1.

3. A UV-curable resin, characterized in that, The raw materials include the following parts by weight: 80-140 parts of unsaturated resin, 2 parts of filler, and 1-3 parts of the photoinitiator as described in claim 2.

4. A UV-curable inner lining flexible tube, characterized in that, It is prepared by injecting the UV-curable resin described in claim 3 into a dry material tube.

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