Bend-resistant polyester resin, method of making and use in powder coatings
The flexurally resistant polyester resin prepared by esterification and polycondensation reaction introduces six-membered rings and urea groups, which solves the problem of insufficient flexibility and adhesion of polyester resins used in powder coatings. It achieves a combination of high hardness, good flexibility and strength, and enhances the adhesion between the coating and the substrate.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Patents(China)
- Current Assignee / Owner
- HENGYANG SHANTAI CHEM
- Filing Date
- 2026-03-31
- Publication Date
- 2026-07-14
AI Technical Summary
Existing polyester resins for powder coatings have low flexibility and adhesion properties, making it difficult to achieve both good strength and toughness.
A bend-resistant polyester resin was prepared by introducing polybasic acids such as isophorone dicarboxylic acid and terephthalic acid and polyols such as neopentyl glycol for esterification and polycondensation reactions. A six-membered ring and urea group were introduced to form a hydrogen bond network, which increased the intermolecular forces, and antioxidants were added to improve flexibility.
It improves the hardness and strength of polyester resin, while also enhancing flexibility and impact resistance, and strengthening the adhesion between the coating and the substrate. The coating's bending resistance and adhesion reach level 0-1.
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Abstract
Description
Technical Field
[0001] This invention relates to the field of polyester resin technology, specifically to a flexurally resistant polyester resin, its preparation method, and its application in powder coatings. Background Technology
[0002] Powder coatings are solid coatings that do not contain organic solvents. They are environmentally friendly, have good film-forming properties, high utilization rate, and are convenient to store and transport, making them widely used in home appliances, furniture, automotive industry, and construction manufacturing. Currently, the film-forming material of powder coatings is mainly polyester resin, which has good gloss, wear resistance, temperature resistance, and insulation properties. However, polyester resin has poor flexibility and is prone to cracking during long-term use, making it difficult to achieve both good strength and toughness.
[0003] Polyester resin is mainly obtained by esterification condensation reaction of polybasic acid monomers and polyol monomers. By controlling different monomers, polyester resin and its powder coatings can be endowed with unique properties. Patent CN112322155B discloses a polyester resin for powder coatings with low TGIC content and excellent low-temperature resistance, as well as its preparation method. Neopentyl glycol, isophorone diisocyanate, isophthalic acid, etc. are used as raw materials for reaction. The resulting polyester resin has good weather resistance, abrasion resistance, and low-temperature resistance. However, this patent does not improve the flexibility and bending resistance of polyester resin and powder coatings. Summary of the Invention
[0004] The technical problem solved by this invention is to address the issue of low toughness and adhesion performance of polyester resins used in powder coatings.
[0005] The technical solution of the present invention is: a flexurally resistant polyester resin, comprising the following raw materials in parts by weight: 34-42 parts polyol, 58-66 parts polyacid, 0.2-0.5 parts catalyst, and 0.3-0.5 parts antioxidant.
[0006] Furthermore, the polyols include neopentyl glycol, 3-methyl-1,5-pentyl glycol, 2,2,4-trimethyl-1,3-pentyl glycol, 2-butyl-2-ethyl-1,3-propanediol, and trimethylolpropane.
[0007] Furthermore, polybasic acids include terephthalic acid, isophthalic acid, and isophorone dibasic acids.
[0008] Furthermore, the catalyst is monobutyltin oxide.
[0009] Furthermore, antioxidants include antioxidant 1010 and antioxidant 168.
[0010] Furthermore, the preparation method of the flexurally resistant polyester resin is as follows:
[0011] (1) Add 100 parts isophorone diisocyanate and 148-176 parts 2-[2-(2-aminoethoxy)ethoxy]acetic acid to the reaction solvent by mass. Stir the reaction at 20-40℃ for 3-8h. Remove the solvent by rotary evaporation. Wash the product with petroleum ether and then recrystallize in ethanol to obtain isophorone dicarboxylic acid.
[0012] (2) Nitrogen gas is introduced into the reactor, polyol, polyacid and catalyst are added, and the mixture is heated to 160-180℃ and stirred until water is produced. Then the temperature is raised to 240-250℃ and the reaction continues, and the generated water is discharged. When the temperature drops to 230-240℃, polyacid is added and the reaction continues until the acidity is 38-45mgKOH / g. The reactor is evacuated and the reaction continues until the acidity is 26-34mgKOH / g. Antioxidant is added and the mixture is cooled to obtain flexural polyester resin.
[0013] Furthermore, the reaction solvent is dichloromethane, trichloromethane, or toluene.
[0014] Furthermore, flexurally resistant polyester resins are used in powder coatings.
[0015] The beneficial technical effects of this invention are as follows: By subjecting polybasic acids such as isophorone dicarboxylic acid and terephthalic acid to polyols such as neopentyl glycol through esterification and polycondensation reactions, a flexurally resistant polyester resin is obtained. The polyester resin molecular chain contains a six-membered ring, which has high rigidity and structural stability, enabling the polyester resin and its coatings to have higher hardness and strength. At the same time, the introduced urea groups enable hydrogen bonding interactions and an ordered hydrogen bond network between the polyester resin molecular chains, enhancing the intermolecular forces and further improving the strength and mechanical properties of the polyester resin.
[0016] This invention introduces multiple flexible ether bonds into polyester resin, which can improve the flexibility, impact resistance and bending resistance of polyester resin, giving polyester resin and coatings both good strength and toughness.
[0017] The urea group of the polyester resin of this invention contains multiple amino groups, which form coordination forces with the surface of substrates such as tinplate, which is beneficial to improving the adhesion and bonding strength between the coating and the substrate. Detailed Implementation
[0018] The present invention will be further described in detail below with reference to specific embodiments. It should be understood that the following embodiments are merely illustrative and explanatory of the present invention and should not be construed as limiting the scope of protection of the present invention. All technologies implemented based on the above content of the present invention are covered within the scope of protection intended by the present invention.
[0019] Example 1 (1) 5 g of isophorone diisocyanate and 7.4 g of 2-[2-(2-aminoethoxy)ethoxy]acetic acid were added to 80 mL of dichloromethane and stirred at 25 °C for 8 h. The solvent was removed by rotary evaporation, the product was washed with petroleum ether, and then recrystallized in ethanol to obtain isophorone dicarboxylic acid. The reaction formula is as follows:
[0020] .
[0021] (2) Nitrogen gas was introduced into the reactor, and 286g neopentyl glycol, 64g 2-butyl-2-ethyl-1,3-propanediol, 25g trimethylolpropane, 367g terephthalic acid, 126g isophthalic acid, 20g isophorone dicarboxylic acid, and 3.4g catalyst monobutyltin oxide were added. The mixture was heated to 170°C and stirred until water was produced. Then the temperature was raised to 240°C and the reaction was continued, and the generated water was removed. The temperature was lowered to 230°C, and 112g isophthalic acid was added. The reaction was continued until the acidity was 40mgKOH / g. The reactor was evacuated and the reaction was continued until the acidity was 29mgKOH / g. 3.7g antioxidant 1010 was added and the mixture was cooled to obtain a flexurally resistant polyester resin.
[0022] Example 2 (1) 10g of isophorone diisocyanate and 17.6g of 2-[2-(2-aminoethoxy)ethoxy]acetic acid were added to 200mL of chloroform and stirred at 20°C for 8h. The solvent was removed by rotary evaporation, the product was washed with petroleum ether, and then recrystallized in ethanol to obtain isophorone dicarboxylic acid.
[0023] (2) Nitrogen gas was introduced into the reactor, and 284g neopentyl glycol, 26g 3-methyl-1,5-pentanediol, 30g trimethylolpropane, 370g terephthalic acid, 134g isophthalic acid, 35g isophorone dicarboxylic acid, and 5g catalyst monobutyltin oxide were added. The mixture was heated to 160°C and stirred until water was produced. Then the temperature was raised to 250°C and the reaction was continued, and the generated water was removed. The temperature was lowered to 240°C and 121g isophthalic acid was added. The reaction was continued until the acidity was 38mgKOH / g. The reactor was evacuated and the reaction was continued until the acidity was 26mgKOH / g. 5g antioxidant 1010 was added and the mixture was cooled to obtain a flexurally resistant polyester resin.
[0024] Example 3 (1) 25g of isophorone diisocyanate and 38g of 2-[2-(2-aminoethoxy)ethoxy]acetic acid were added to 500mL of toluene and stirred at 40°C for 3h. The solvent was removed by rotary evaporation, the product was washed with petroleum ether, and then recrystallized in ethanol to obtain isophorone dicarboxylic acid.
[0025] (2) Nitrogen gas was introduced into the reactor, and 294g neopentyl glycol, 46g 2,2,4-trimethyl-1,3-pentanediol, 32g trimethylolpropane, 342g terephthalic acid, 124g isophthalic acid, 50g isophorone dicarboxylic acid, and 2.8g catalyst monobutyltin oxide were added. The mixture was heated to 170°C and stirred until water was produced. Then the temperature was raised to 245°C and the reaction was continued, and the generated water was removed. The temperature was lowered to 240°C and 112g isophthalic acid was added. The reaction was continued until the acidity was 45mgKOH / g. The reactor was evacuated and the reaction was continued until the acidity was 34mgKOH / g. 3g antioxidant 168 was added and the mixture was cooled to obtain a flexurally resistant polyester resin.
[0026] Example 4 (1) Nitrogen gas was introduced into the reactor, and 308g of neopentyl glycol, 75g of 3-methyl-1,5-pentanediol, 37g of trimethylolpropane, 307g of terephthalic acid, 108g of isophthalic acid, 70g of isophorone dicarboxylic acid (prepared according to the method of Example 3), and 2g of catalyst monobutyltin oxide were added. The mixture was heated to 180°C and stirred until water was generated. Then the temperature was raised to 240°C and the reaction was continued, and the generated water was removed. The temperature was lowered to 230°C, and 95g of isophthalic acid was added. The reaction was continued until the acidity was 45mgKOH / g. The reactor was evacuated and the reaction was continued until the acidity was 34mgKOH / g. 4.2g of antioxidant 168 was added and the mixture was cooled to obtain a flexurally resistant polyester resin.
[0027] Comparative Example 1 (1) Nitrogen gas was introduced into the reactor, and 286g of neopentyl glycol, 64g of 2-butyl-2-ethyl-1,3-propanediol, 25g of trimethylolpropane, 367g of terephthalic acid, 126g of isophthalic acid, 20g of 1,6-adipic acid, and 3.4g of catalyst monobutyltin oxide were added. The mixture was heated to 170°C and stirred until water was produced. Then the temperature was raised to 240°C and the reaction was continued, and the generated water was removed. The temperature was lowered to 230°C, and 112g of isophthalic acid was added. The reaction was continued until the acidity was 40mgKOH / g. The reactor was evacuated and the reaction was continued until the acidity was 29mgKOH / g. 3.7g of antioxidant 1010 was added and the mixture was cooled to obtain polyester resin.
[0028] Comparative Example 2 (1) Nitrogen gas was introduced into the reactor, and 286g of neopentyl glycol, 64g of 2-butyl-2-ethyl-1,3-propanediol, 25g of trimethylolpropane, 367g of terephthalic acid, 126g of isophthalic acid, 20g of 3,6,9-trioxaundecanoic acid (CAS No. 13887-98-4), and 3.4g of catalyst monobutyltin oxide were added. The mixture was heated to 170°C and stirred until water was produced. Then the temperature was raised to 240°C and the reaction was continued, and the generated water was removed. The temperature was lowered to 230°C, and 112g of isophthalic acid was added. The reaction was continued until the acidity was 40mgKOH / g. The reactor was evacuated and the reaction was continued until the acidity was 29mgKOH / g. 3.7g of antioxidant 1010 was added and the mixture was cooled to obtain polyester resin.
[0029] Comparative Example 3 (1) Nitrogen gas was introduced into the reactor, and 286g of neopentyl glycol, 64g of 2-butyl-2-ethyl-1,3-propanediol, 25g of trimethylolpropane, 367g of terephthalic acid, 126g of isophthalic acid, 20g of 1,4-cyclohexanedicarboxylic acid (CAS No. 1076-97-7), and 3.4g of catalyst monobutyltin oxide were added. The mixture was heated to 170°C and stirred until water was produced. Then the temperature was raised to 240°C and the reaction was continued, and the generated water was removed. The temperature was lowered to 230°C, and 112g of isophthalic acid was added. The reaction was continued until the acidity was 40mgKOH / g. The reactor was evacuated and the reaction was continued until the acidity was 29mgKOH / g. 3.7g of antioxidant 1010 was added and the mixture was cooled to obtain polyester resin.
[0030] Comparative Example 4 (1) 5 g of isophorone diisocyanate and 3.4 g of glycine were added to 80 mL of dichloromethane and stirred at 25 °C for 8 h. The solvent was removed by rotary evaporation, the product was washed with petroleum ether, and then recrystallized in ethanol to obtain isophorone dicarboxylic acid with the following structural formula: .
[0031] (2) Nitrogen gas was introduced into the reactor, and 286g neopentyl glycol, 64g 2-butyl-2-ethyl-1,3-propanediol, 25g trimethylolpropane, 367g terephthalic acid, 126g isophthalic acid, 20g diethylene glycol (CAS No. 110-99-6), and 3.4g catalyst monobutyltin oxide were added. The mixture was heated to 170°C and stirred until water was produced. Then the temperature was raised to 240°C and the reaction was continued, and the generated water was removed. The temperature was lowered to 230°C, and 112g of isophthalic acid was added. The reaction was continued until the acidity was 40mgKOH / g. The reactor was evacuated and the reaction was continued until the acidity was 29mgKOH / g. 3.7g antioxidant 1010 was added and the mixture was cooled to obtain polyester resin.
[0032] 1 kg of polyester resin prepared in each example and comparative example was weighed and mixed with 410 g of barium sulfate, 320 g of titanium dioxide, 12 g of leveling agent (Sago-3565), 7 g of benzoin, and 74 g of triglycidyl isocyanate. The mixture was melt-mixed and extruded through an extruder, and then crushed, ground, and sieved to obtain a powder coating. The powder coating was sprayed onto the surface of a tinplate substrate using an electrostatic sprayer and baked and cured at 190°C for 15 min to form a paint film coating. The performance of the paint film coating was tested according to standards HG-T 2006-2006, GB / T 20624.2-2006, and GB / T 30791-2014.
[0033] Table 1 Performance of Powder Coatings
[0034]
[0035] As shown in Table 1, isophorone dicarboxylic acid was added during the preparation of polyester resin in each embodiment. This introduced a six-membered ring, multiple urea groups, and flexible ether bonds into the polyester resin molecular chain. The six-membered ring has high rigidity and structural stability, which can give the polyester resin and its coatings higher hardness and strength. Simultaneously, the introduced urea groups form hydrogen bond interactions and an ordered hydrogen bond network between the polyester resin molecular chains, enhancing the intermolecular forces and further improving the strength and mechanical properties of the polyester resin. The introduction of multiple flexible ether bonds also improves the flexibility of the polyester resin, achieving a T-bend rating of 0-1T, indicating good impact resistance and bending resistance. Furthermore, the urea groups in the polyester resin contain multiple amino groups, forming coordination forces with substrates such as tinplate, which is beneficial for improving the adhesion and bonding strength between the coating and the substrate, achieving a cross-cut test rating of 0-1.
[0036] Compared to Example 1, Comparative Example 1 used conventional 1,6-adipic acid instead of isophorone dicarboxylic acid. The polyester resin and its coating did not contain a six-membered ring, multiple urea groups, or flexible ether bonds, resulting in poor impact resistance, hardness, flexural strength, and adhesion. Comparative Example 2 used 3,6,9-trioxaundecanoic acid, which did not contain a six-membered ring or multiple urea groups, resulting in poor impact resistance, hardness, and adhesion. Comparative Example 3 used 1,4-cyclohexanedicarboxylic acid, which did not contain multiple urea groups or flexible ether bonds, resulting in poor impact resistance, hardness, flexural strength, and adhesion. Comparative Example 4 used isophorone dicarboxylic acid, which did not contain multiple ether bonds, resulting in poor impact resistance and flexural strength.
[0037] The above embodiments are preferred embodiments of the present invention, but the embodiments of the present invention are not limited to the above embodiments. Any changes, modifications, substitutions, combinations, or simplifications made without departing from the spirit and principle of the present invention shall be considered equivalent substitutions and shall be included within the protection scope of the present invention.
Claims
1. A flexurally resistant polyester resin, characterized in that, The flexurally resistant polyester resin comprises the following raw materials in parts by weight: 34-42 parts polyol, 58-66 parts polyacid, 0.2-0.5 parts catalyst, and 0.3-0.5 parts antioxidant. Polybasic acids include isophorone dicarboxylic acids, which are prepared by the following method: isophorone diisocyanate and 2-[2-(2-aminoethoxy)ethoxy]acetic acid are added to the reaction solvent, the reaction is stirred, the solvent is removed by rotary evaporation, the product is washed with petroleum ether, and then recrystallized in ethanol to obtain isophorone dicarboxylic acids. The polyols include one or more of neopentyl glycol, 3-methyl-1,5-pentyl glycol, 2,2,4-trimethyl-1,3-pentyl glycol, 2-butyl-2-ethyl-1,3-propanediol, and trimethylolpropane. The polybasic acid also includes one or more of terephthalic acid and isophthalic acid.
2. The flexurally resistant polyester resin according to claim 1, characterized in that, The catalyst is monobutyltin oxide, and the antioxidant includes one or more of antioxidant 1010 and antioxidant 168.
3. The flexurally resistant polyester resin according to claim 1, characterized in that, The reaction solvent is dichloromethane, trichloromethane, or toluene.
4. The flexurally resistant polyester resin according to claim 1, characterized in that, The isophorone diisocyanate comprises 100 parts by mass and 2-[2-(2-aminoethoxy)ethoxy]acetic acid comprises 148-176 parts by mass.
5. The flexurally resistant polyester resin according to claim 1, characterized in that, The reaction temperature is 20-40℃, and the reaction time is 3-8h.
6. A method for preparing the flexurally resistant polyester resin according to any one of claims 1-5, characterized in that, The preparation method is as follows: nitrogen gas is introduced into the reaction vessel, polyol, polyacid, and catalyst are added, and the mixture is heated to 160-180℃ and stirred until water is produced. Then the temperature is raised to 240-250℃ and the reaction continues, and the generated water is discharged. The temperature is lowered to 230-240℃, polyacid is added, and the reaction continues until the acidity is 38-45 mg KOH / g. The reaction vessel is evacuated, and the reaction continues until the acidity is 26-34 mg KOH / g. An antioxidant is added, and the mixture is cooled to obtain a flexurally resistant polyester resin.
7. The application of a flexurally resistant polyester resin obtained by the preparation method as described in claim 6 in powder coatings.