Preparation method and application of imide type light-cured unsaturated polyester resin

Abstract

The invention provides a preparation method and application of imide type light-cured unsaturated polyester resin. The method comprises the following steps: carrying out imidization reaction on trimellitic anhydride and diamine to prepare imide diacid; carrying out esterification and polycondensation reaction on the imide diacid, aromatic diacid and neopentyl glycol to prepare imide type polyester polyol; then reacting with maleic anhydride to introduce unsaturated double bonds, and matching with a photosensitizer to prepare the imide type light-cured unsaturated polyester resin. The resin has good flowability, dipping processability and storage stability and can be rapidly cured under the illumination condition, a cured product has high crosslinking strength, hardness, heat resistance and water-resistant stability, the comprehensive requirements of trenchless repair construction for curing speed, forming consistency and long-term service reliability can be met, and the application prospect is wide. The material is suitable for drainage, thermal and industrial pipeline CIPP repair projects with high requirements, especially can meet the requirement of thermal pipeline CIPP repair for long-term hot water medium resistance of lining materials, and has good application prospects.

Description

Technical Field

[0001] This invention relates to imide-type photocurable unsaturated polyester resins, and particularly to a method for preparing and applying an imide-type photocurable unsaturated polyester resin. Background Technology

[0002] CIPP (Cured-In-Place Pipe) pipeline repair technology is widely used for the repair of underground pipelines in municipal drainage, combined sewer systems, and industrial networks due to its advantages such as short construction period, minimal impact on traffic and the surrounding environment, and applicability to trenchless repair. This technology typically uses reinforced felt / fabric hoses as a carrier, impregnates the resin system within the hose, and introduces it into the pipeline to be repaired. Subsequently, the resin is rapidly cured by light to form a liner layer with load-bearing and sealing capabilities. For CIPP hoses using the light-curing method, the resin system not only needs to have suitable viscosity at room temperature to ensure impregnation and controllable resin content, but also needs to maintain good storage stability during transportation, storage, and construction. Simultaneously, it needs to achieve rapid, thorough, and uniform curing under on-site light conditions to ensure the molding quality and service reliability of the liner layer.

[0003] Among existing photocurable CIPP resin systems, unsaturated polyester resins are widely used due to their moderate cost and the ability to achieve cross-linking and curing by introducing unsaturated double bonds and combining them with photosensitizers. These systems typically rely on reactive diluents to reduce viscosity to meet impregnation process requirements and use polymerization inhibitors to improve storage stability. However, under long-term pipeline service conditions, the lining layer often faces the combined effects of continuous humidity, hot water erosion, acid, alkali, salt, and organic contaminant corrosion, the influence of microbial metabolites, and periodic temperature fluctuations. Conventional photocurable unsaturated polyester curing products may exhibit insufficient heat resistance, poor hydrolysis / media stability, and performance degradation due to long-term aging of the cross-linking network. On the other hand, increasing resin rigidity or cross-linking density to improve heat and media resistance can easily lead to increased system viscosity, impregnation difficulties, increased curing shrinkage and brittleness, and uneven curing—a contradiction between process and performance, thus affecting the CIPP field application window and the consistency of repair quality.

[0004] To address these issues, the industry typically employs methods such as increasing the proportion of aromatic diacids, introducing structural units like neopentyl glycol, and adjusting the content of unsaturated monomers and photoinitiation systems for modification. However, there may still be a trade-off between "limited improvement in heat and media resistance" and "decreased process compatibility." Furthermore, the introduction of some high-heat-resistant structures can increase the rigidity and polarity of the main chain, leading to increased viscosity of the resin system, decreased compatibility with diluents, decreased photocuring reaction rate, or insufficient curing depth. Consequently, it becomes difficult to meet the comprehensive requirements of CIPP hoses for "impregnation capability, storage capability, rapid curing capability, and long-term service capability."

[0005] Therefore, there is an urgent need for a photocurable unsaturated polyester resin system for CIPP pipeline repair, which maintains good impregnation processability and storage stability while also ensuring rapid curing and molding capabilities, and further improves the heat resistance and hydrolysis / media stability of the cured liner to enhance the long-term service reliability of the repair liner. This application proposes corresponding preparation routes and application schemes focusing on the introduction of imide structures, the construction of unsaturated sites, and the matching of photosensitive curing systems. Summary of the Invention

[0006] Based on the above analysis, the present invention aims to provide a method for preparing an imide-type photocurable unsaturated polyester resin and its application.

[0007] The objective of this invention is mainly achieved through the following technical solutions:

[0008] The present invention provides a method for preparing an imide-type photocurable unsaturated polyester resin in a first aspect, comprising the following steps:

[0009] S1: The imidization reaction of the anhydride with the diamine yields an imidized diacid;

[0010] S2: The imide diacid, isophthalic acid and neopentyl glycol are subjected to esterification and polycondensation reaction to obtain an imide-type polyester polyol;

[0011] S3: The imide-type polyester polyol is subjected to an esterification reaction with maleic anhydride to introduce unsaturated double bonds and obtain an imide-type unsaturated polyester.

[0012] S4: Add a photosensitizer to the imide-type unsaturated polyester to obtain an imide-type photocurable unsaturated polyester resin.

[0013] In one or more embodiments, the trimellitic anhydride is trimellitic tricarboxylic anhydride.

[0014] In one or more embodiments, the diamine is one or more of an aliphatic diamine, an alicyclic diamine, or an aromatic diamine.

[0015] In one or more embodiments, the molar ratio of meta-anhydride to diamine in step S1 is (1.8-2.2):1.

[0016] In one or more embodiments, the imidization reaction in step S1 is carried out at 120-220°C, and the reaction is directed toward the formation of imidic diacid by continuous dehydration.

[0017] In one or more embodiments, the ratio of the total molar amount of diacid to the molar amount of neopentyl glycol in step S2 is 1:(2.0-2.5), and the esterification and polycondensation reaction in step S2 is carried out at 180-240°C, and the imide-type polyester polyol is obtained by dehydration and / or reduced compression polycondensation.

[0018] In one or more embodiments, step S2 and / or step S3 are carried out in the presence of a catalyst, which is one or more of titanate catalysts, tin-based catalysts or antimony-based catalysts, and the amount of catalyst added is 0.01-0.5 wt% of the total mass of the reactants.

[0019] In one or more embodiments, the equivalent ratio of maleic anhydride in step S3 to the hydroxyl groups in the imide-type polyester polyol obtained in step S2 is (1.10-1.50):1, and step S3 is carried out at 120-200°C.

[0020] In one or more embodiments, the photosensitizer in step S4 is one or more of benzoyl, benzoin ether, α-hydroxy ketone or acylphosphine oxide, and the amount of photosensitizer added is 0.5-5 wt% of the total mass of the imide-type photocurable unsaturated polyester resin; and a reactive diluent and / or polymerization inhibitor are also added in step S4, wherein the amount of reactive diluent added is 40-60 wt% of the total mass of the resin, and the amount of polymerization inhibitor added is 50-1000 ppm.

[0021] In a second aspect, the present invention provides the application of an imide-type photocurable unsaturated polyester resin in a photocurable hose for CIPP pipe repair.

[0022] The technical solution of this invention can achieve at least one of the following effects:

[0023] (1) Synergistic reinforcement of the imide skeleton with the aromatic diacid and neopentyl glycol structure: In this invention, imide diacid is prepared by imidizing the anhydride and diamine in S1, and then imide diacid is esterified and polycondensed with isophthalic acid and neopentyl glycol in S2 to form an imide-type polyester polyol. The rigid ring structure of imide, the steric structure of aromatic segments and neopentyl glycol are introduced at the molecular skeleton level to achieve a comprehensive improvement in the thermal stability, structural stability and moisture resistance of the cured product, thereby alleviating the performance degradation and long-term reliability problems that traditional photocurable unsaturated polyesters are prone to in the CIPP service environment.

[0024] (2) The unsaturated sites are controllably introduced and matched with the photosensitive curing system to achieve rapid curing and high crosslinking strength. In S3, maleic anhydride is used to esterify the imide-type polyester polyol to introduce unsaturated double bonds. Then, in S4, a photosensitizer is added to trigger photocuring crosslinking, so that the density of unsaturated sites and the photoinitiation efficiency are matched. This ensures that the resin can quickly change from a flow state to a gel state and complete surface drying under light conditions, while obtaining a high degree of crosslinking and curing strength. Combined with the test system set in this application, it can show a shorter gel time (or the time of exothermic peak appearance) and a higher Barcol hardness, which is beneficial to shorten the on-site curing time of CIPP, improve the molding consistency and reduce the risk of lining defects caused by insufficient curing.

[0025] (3) The synergistic design of dilution-polymerization inhibition-process window takes into account both impregnation processability and storage stability. In S4, the present invention allows the introduction of reactive diluents and polymerization inhibitors, and standardizes the photosensitizer addition system, so that the resin can obtain more controllable storage stability and construction window while meeting the flowability required for CIPP hose impregnation. Combined with the established viscosity and storage stability evaluation method, the viscosity of the resin at room temperature can be kept in a suitable processing range and the viscosity growth at 60℃ for 48h can be controlled. At the same time, the water absorption rate of the cured product is at a low level, thereby achieving a synergistic balance between "impregnation, storage, rapid curing and long-term service", solving the problem that processability and stability are difficult to balance in the existing system.

[0026] In this invention, the above-described technical solutions can be combined with each other to achieve more preferred combinations. Other features and advantages of this invention will be set forth in the following description, and some advantages may become apparent from the description or be learned by practicing the invention. The objects and other advantages of this invention can be realized and obtained from the description and drawings, which are particularly pointed out. Attached Figure Description

[0027] The accompanying drawings are for illustrative purposes only and are not intended to limit the invention. Throughout the drawings, the same reference numerals denote the same parts.

[0028] Figure 1 This is a flowchart of the preparation process of the present invention. Detailed Implementation

[0029] The technical solution of the present invention will be further described below with reference to specific embodiments. However, the present invention should not be limited to these embodiments. Unless specifically stated otherwise, all features can be replaced by other equivalent or similar features. Unless specifically stated otherwise, each feature is only one example of a series of equivalent or similar features. The terminology used in the present invention, unless otherwise stated, generally has the meaning commonly understood by those skilled in the art. In the following embodiments, unless otherwise stated, concentration % refers to mass percentage; all substances used are commercially available.

[0030] Example 1

[0031] Preparation of imide-type photocurable unsaturated polyester resin

[0032] S1: Preparation of imidic acid

[0033] 90.0 g (0.468 mol) of trimellitic anhydride and 150.0 g of xylene were added to a reactor equipped with a stirrer, thermometer, nitrogen protection, and water separator. The mixture was heated to 120 °C and stirred to disperse. 46.5 g (0.234 mol) of 4,4'-diaminodiphenylmethane (MDA) was added in batches at 130 °C. After the addition was complete, the mixture was heated to 145 °C and refluxed for 4 h. The mixture was continuously dehydrated and approximately 8.4 g of water was collected. After the reaction was completed, the temperature was lowered to 140 °C, and xylene was removed under reduced pressure at 20 kPa to obtain imide diacid.

[0034] S2: Preparation of imide-type polyester polyols

[0035] Weigh 136.5 g (0.234 mol) of the imide diacid obtained from S1, add 156.5 g (0.942 mol) of isophthalic acid, 270.0 g (2.592 mol) of neopentyl glycol, 20.0 g (0.262 mol) of propylene glycol and 0.73 g of tetrabutyl titanate; stir under nitrogen and heat to 210 °C for 2 h while continuously dehydrating; then heat to 235 °C and reduce the system pressure to 15 kPa, polycondense for 2 h to obtain imide-type polyester polyol.

[0036] S3: Preparation of imide-type unsaturated polyester

[0037] Weigh 600.0g of the imide-type polyester polyol obtained from S2, add 0.15g of hydroquinone monomethyl ether, and then add 112.0g (1.142mol) of maleic anhydride. Stir and react at 165℃ for 2h to make the maleic anhydride to hydroxyl equivalent ratio 1.10:1, and obtain the imide-type unsaturated polyester.

[0038] S4: Preparation of imide-type photocurable unsaturated polyester resin

[0039] Weigh 585.0g of the imide-type unsaturated polyester obtained from S3, cool it to 60℃, add 390.0g of styrene, stir for 30min to make the solid content 60wt%; add 0.30g of hydroquinone monomethyl ether, then add 30.0g of photosensitizer TPO, stir for 20min, filter to obtain imide-type photocurable unsaturated polyester resin.

[0040] Example 2:

[0041] Preparation of imide-type photocurable unsaturated polyester resin

[0042] S1: Preparation of imidic acid

[0043] 90.0 g (0.468 mol) of trimellitic anhydride and 150.0 g of xylene were added to a reactor equipped with a stirrer, thermometer, nitrogen protection, and water separator. The mixture was heated to 120 °C and stirred to disperse. 40.0 g (0.235 mol) of isophorone diamine (IPDA) was added in batches at 130 °C. After the addition was complete, the mixture was heated to 145 °C and refluxed for 4 h. The mixture was continuously dehydrated and approximately 8.4 g of water was collected. After the reaction was completed, the temperature was lowered to 140 °C, and xylene was removed under reduced pressure at 20 kPa to obtain imide dicarboxylic acid.

[0044] S2: Preparation of imide-type polyester polyols

[0045] Weigh 108.9 g (0.235 mol) of the imide diacid obtained from S1, add 156.5 g (0.942 mol) of isophthalic acid, 270.0 g (2.592 mol) of neopentyl glycol, 35.0 g (0.261 mol) of dipropylene glycol and 0.73 g of tetrabutyl titanate; stir under nitrogen and heat to 210 °C for 2 h while continuously dehydrating; then heat to 235 °C and reduce the system pressure to 12-15 kPa, polycondense for 2 h to obtain imide-type polyester polyol.

[0046] S3: Preparation of imide-type unsaturated polyester

[0047] Weigh 600.0g of the imide-type polyester polyol obtained from S2, add 0.15g of hydroquinone monomethyl ether, and then add 108.0g of maleic anhydride. Stir and react at 165℃ for 2h to make the maleic anhydride to hydroxyl equivalent ratio 1.10:1, and obtain the imide-type unsaturated polyester.

[0048] S4: Preparation of imide-type photocurable unsaturated polyester resin

[0049] Weigh 585.0 g of the imide-type unsaturated polyester obtained from S3, cool it to 60℃, add 390.0 g of styrene, stir for 30 min to make the solid content 60 wt%; add 0.30 g of hydroquinone monomethyl ether, then add 26.0 g of photosensitizer bis(2,4,6-trimethylbenzoyl)phenylphosphine oxide (BAPO), stir for 20 min, filter to obtain imide-type photocurable unsaturated polyester resin.

[0050] Example 3

[0051] Preparation of imide-type photocurable unsaturated polyester resin

[0052] S1: Preparation of imidic acid

[0053] 120.0 g (0.625 mol) of trimellitic anhydride and 200.0 g of xylene were added to a reactor equipped with a stirrer, thermometer, nitrogen protection, and water separator. The mixture was heated to 120 °C and stirred to disperse. 51.0 g (0.299 mol) of isophorone diamine (IPDA) was added in batches at 130 °C. After the addition was complete, the mixture was heated to 145 °C and refluxed for 4 h. The mixture was continuously dehydrated and approximately 11.3 g of water was collected. After the reaction was completed, the mixture was cooled to 140 °C, and xylene was removed under reduced pressure at 20 kPa to obtain imide dicarboxylic acid.

[0054] S2: Preparation of imide-type polyester polyols

[0055] Weigh 138.9 g (0.299 mol) of the imide diacid obtained from S1, add 133.0 g (0.80 mol) of isophthalic acid, 270.0 g (2.592 mol) of neopentyl glycol, 35.0 g (0.261 mol) of dipropylene glycol and 0.73 g of tetrabutyl titanate; stir under nitrogen and heat to 215 °C for 2 h and continuously dehydrate; then heat to 238 °C and reduce the system pressure to 10-15 kPa, polycondense for 2 h to obtain imide-type polyester polyol.

[0056] S3: Preparation of imide-type unsaturated polyester

[0057] Weigh 650.0g of the imide-type polyester polyol obtained from S2, add 0.20g of hydroquinone monomethyl ether, and then add 112.0g (1.142mol) of maleic anhydride. Stir and react at 170℃ for 2h to make the maleic anhydride to hydroxyl equivalent ratio 1.20:1, and obtain the imide-type unsaturated polyester.

[0058] S4: Preparation of imide-type photocurable unsaturated polyester resin

[0059] Weigh 585.0g of the imide-type unsaturated polyester obtained from S3, cool it to 60℃, add 390.0g of styrene, stir for 30min to make the solid content 60wt%; add 0.30g of hydroquinone monomethyl ether, then add 30.0g of photosensitizer TPO, stir for 20min, filter to obtain imide-type photocurable unsaturated polyester resin.

[0060] The performance of the imide-type photocurable unsaturated polyester resins prepared in Examples 1-3 was tested.

[0061] Detection indicators and methods

[0062] (1) Acid value (mgKOH / g)

[0063] The resin acid value was tested according to GB / T 2895.

[0064] (2) Viscosity at 25℃ (mPa·s)

[0065] The resin viscosity at 25℃ should be tested according to GB / T 7193. To meet the requirements for UV-cured CIPP impregnation and resin content control, the resin viscosity should be controlled within the range of 500-1000 mPa·s.

[0066] (3) Temperature and time of exothermic peak of photocuring

[0067] Weigh 10g ± 0.01g of resin sample into a test tube and fix it in a test tube rack; keep the ultraviolet lamp 25cm away from the test tube; use a 365nm ultraviolet light source (power density 1000mW / cm²), adjust the power of the ultraviolet lamp to 70% (about 400-650W), and record the exothermic peak temperature and the time of the exothermic peak appearance.

[0068] (4) Bending properties of the casting (bending strength / bending modulus)

[0069] After the resin is cast and cured, its flexural strength and flexural modulus are tested according to ISO 178.

[0070] (5) Storage stability (proportion of viscosity increase at 60℃ for 48 hours)

[0071] The resin was sealed and protected from light and placed in a constant temperature environment of 60℃ for 48 hours. The initial viscosity η0 and the viscosity η48 after 48 hours were measured. The viscosity increase ratio was calculated as (η48 / η0−1).

[0072] (6) Glass fiber wettability (sinking time)

[0073] Cut a 100cm² piece of fiberglass cloth, weigh 600mL of resin and place it in a beaker. Lay the fiberglass cloth flat on the surface of the resin and record the time required for the fiberglass cloth to be completely immersed in the resin.

[0074] The test results are as follows:

[0075] Table 1 Performance Test Results

[0076]

[0077] Data Analysis

[0078] (1) The acid value is 11.8–13.2 mgKOH / g, which is comparable to that of commercially available UV-CIPP UPR (11 mgKOH / g), indicating that the esterification / condensation reaction is well controlled and the residual acid groups in the system are at a controllable level, which is conducive to obtaining stable viscosity and consistency of subsequent curing. The viscosity at 25℃ is 674–819 mPa·s, which is within the 500–1000 mPa·s window that is more suitable for UV-cured CIPP resins, which facilitates the impregnation of hoses / felts and the control of resin content, while reducing the risk of insufficient impregnation caused by high viscosity.

[0079] (2) Under the conditions of 365nm and 1000mW / cm², the time of the exothermic peak is 5m18s–6m20s, which is shorter than the 7m37s of commercial resin, indicating that the initiation system and the unsaturated sites are well matched and the curing reaction starts quickly; the exothermic peak temperature is 210–224℃, which is comparable to or slightly higher than that of commercial resin (about 209℃), reflecting higher curing reaction activity and crosslinking degree.

[0080] (3) The flexural strength of the cured casting is 134–153 MPa and the flexural modulus is 4.4–5.2 GPa, both of which are higher than those of commercially available UV-CIPP UPR (120 MPa, 3.6 GPa), indicating that the resin cured product of the present invention has advantages in load-bearing and deformation resistance, and can improve the support of the inner lining structure and the reliability of long-term service.

[0081] (4) The viscosity increase rate after 48 hours of sealed storage at 60℃ and protected from light was 12%–16%, which is comparable to that of commercially available resin (15%). This indicates that the viscosity increase of the system is controllable under accelerated storage conditions and can meet the storage requirements before transportation and on-site construction. The sinking time of the glass fiber cloth was 25–34 seconds, indicating that the resin has good wettability to the reinforcing material, which is beneficial to obtaining a uniform resin content and fewer defects in the inner lining layer.

[0082] The above description is only a preferred embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any changes or substitutions that can be easily conceived by those skilled in the art within the scope of the technology disclosed in the present invention should be included within the scope of protection of the present invention.

Claims

1. A method for preparing an imide type photo-curable unsaturated polyester resin, characterized by, The method comprises the following steps: S1: imidization reaction of trimellitic anhydride and diamine to prepare imide diacid; S2: esterification and polycondensation reaction of the imide diacid, isophthalic acid and neopentyl glycol to prepare imide polyester polyol; S3: esterification reaction of the imide polyester polyol and maleic anhydride to introduce unsaturated double bonds to prepare imide unsaturated polyester; S4: adding photosensitizer to the imide unsaturated polyester to obtain imide photocurable unsaturated polyester resin.

2. The method of claim 1, wherein, The trimellitic anhydride is trimellitic anhydride.

3. The method of claim 1, wherein, The diamine is one or more of aliphatic diamine, alicyclic diamine or aromatic diamine.

4. The method of claim 1, wherein, The molar ratio of trimellitic anhydride to diamine in step S1 is (1.8-2.2):

1.

5. The method of claim 1, wherein, The imidization reaction in step S1 is carried out at 120-220℃, and the reaction is carried out in the direction of generating imide diacid by continuous dehydration.

6. The method of claim 1, wherein, The ratio of total moles of diacid to moles of neopentyl glycol in step S2 is 1:(2.0-2.5), and the esterification reaction temperature is 180-220℃ and the polycondensation reaction temperature is 220-260℃.

7. The method of claim 1, wherein, Step S2 and / or step S3 is carried out in the presence of a catalyst, which is one or more of titanate catalyst, tin-based catalyst or antimony-based catalyst, and the addition amount of the catalyst is 0.01-0.5wt% of the total mass of the reactants.

8. The method of claim 1, wherein, The equivalent ratio of maleic anhydride to hydroxyl groups in the polyester polyol obtained in step S2 in step S3 is (1.10-1.50):1, and the reaction temperature of step S3 is 130-200℃.

9. The method of claim 1, wherein, The photosensitizer in step S4 is one or more of benzoyl, benzoin ether, α-hydroxy ketone or acyl phosphine oxide, and the addition amount of the photosensitizer is 0.5-5wt% of the total mass of the resin; and further adding reactive diluent and / or polymerization inhibitor, wherein the addition amount of the reactive diluent is 40-60wt% of the total mass of the resin, and the addition amount of the polymerization inhibitor is 50-1000ppm.

10. Application of imide photocurable unsaturated polyester resin in photocurable soft tube for CIPP pipe repair.

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