A polyester resin, a method for preparing and using the same, and a thermosetting textured powder coating

Abstract

The application provides a polyester resin and a preparation method and application thereof and a thermosetting wrinkle powder coating, and relates to the technical field of wrinkle powder coating.The polyol and the polyacid with high symmetry structure are used as esterification monomers of the polyester resin, the polyester resin can be quickly textured during the curing process, the alkoxyl titanate and the dibutyltin dichloride are used as the esterification catalysts, the reaction activity of the polyester resin is improved, the naphthalene tetracarboxylic dianhydride with high reaction activity is used as the end-capped anhydride after the polycondensation reaction, the reaction activity of the polyester resin is high, the coating has good stereoscopic feeling after being textured, and the core-shell structure curing accelerator greatly improves the reaction activity of the polyester resin.The thermosetting wrinkle powder coating can be cured at a low temperature of 140 DEG C, the coating can be quickly textured during the curing process, the texture is clear, and the coating has outstanding stereoscopic feeling.

Description

Technical Field

[0001] This invention relates to the field of wrinkle powder coating technology, specifically to a polyester resin, its preparation method and application, and thermosetting wrinkle powder coatings. Background Technology

[0002] Thermosetting powder coatings are solid powder coatings composed of thermosetting synthetic resins as film-forming substances, along with curing agents, pigments, and fillers. After spraying, an irreversible chemical cross-linking reaction occurs upon heating, forming an insoluble and infusible hard protective coating. They offer advantages such as environmental friendliness, resource conservation, and excellent overall performance. However, compared to liquid coatings, thermosetting powder coatings typically have higher curing temperatures (180~200℃) and longer curing times (10~30min). This limits their application to heat-resistant metal substrates, making them unsuitable for heat-sensitive substrates such as wood, paper, and plastics. Furthermore, the high-temperature, long-duration curing process results in significant heat energy consumption, further restricting the application of thermosetting powder coatings. Therefore, the development of low-temperature curing thermosetting powder coatings is an urgent need.

[0003] Depending on the desired decorative effect, thermosetting powder coatings are categorized into planar powder coatings that produce a smooth finish and wrinkle-like powder coatings that create a textured effect. A related technology discloses a Primid-based low-temperature curing ultra-weather-resistant powder coating made of polyester resin, using a β-hydroxyalkylamide compound as a curing agent to prepare an ultra-weather-resistant powder coating capable of low-temperature curing at 140-160℃. However, this polyester resin can only be applied to planar powder coatings. When applied to wrinkle-like powder coatings, the resulting coating exhibits poor texture, small and unclear lines, and weak three-dimensionality, failing to meet the texture requirements of wrinkle-like powder coatings. Therefore, there is an urgent need for a thermosetting wrinkle-like powder coating that can cure at low temperatures and also provides a good textured effect. Summary of the Invention

[0004] In view of this, the object of the present invention is to provide a polyester resin, its preparation method and application, and a thermosetting wrinkle powder coating. When the polyester resin provided by the present invention is applied to a thermosetting wrinkle powder coating, the coating has a low curing temperature and a good wrinkle-inducing effect.

[0005] To achieve the above-mentioned objectives, the present invention provides the following technical solution: This invention provides a polyester resin, comprising, by weight, the following raw materials: The composition includes 7-10.5 parts of polyol, 8-10 parts of polyacid, 1.5-3 parts of end-capped anhydride, 0.02-0.06 parts of esterification catalyst, and 0.5-1.5 parts of curing accelerator. The structures of the polyols and polyacids are independently symmetrical about the C2 rotational axis; The esterification catalyst includes alkoxytitanate and dibutyltin dichloride; The curing accelerator has a core-shell structure; The capped anhydride includes naphthalenetetracarboxylic dianhydride; The gelation time of the polyester resin at 140°C is 120~140s.

[0006] Preferably, the polyol comprises the following components in parts by mass: 7-8 parts of 1,4-butanediol, 0-2 parts of neopentyl glycol, and 0-0.5 parts of 1,6-hexanediol.

[0007] Preferably, the polyacid comprises the following components in parts by mass: 8-9 parts of terephthalic acid, 0-1 parts of isophthalic acid, and 0-2 parts of adipic acid.

[0008] Preferably, the capped anhydride comprises the following components in parts by mass: 3-5 parts of naphthalenetetracarboxylic dianhydride and 0-2 parts of pyromellitic dianhydride.

[0009] Preferably, the curing accelerator comprises the following components in parts by weight: 2-5 parts of quaternary phosphonium salt type curing accelerator and 0-3 parts of tertiary amine type curing accelerator; The core of the quaternary phosphonium salt type curing accelerator is a quaternary phosphonium salt, and the shell comprises titanium dioxide and styrene-maleic anhydride alternating copolymers; the titanium dioxide and styrene-maleic anhydride alternating copolymers are grafted by covalent bonds; The core of the tertiary amine curing accelerator is a tertiary amine, and the shell is graphene nanosheets.

[0010] Preferably, the mass ratio of the alkoxytitanate to dibutyltin dichloride is 2~4:1~2.

[0011] This invention provides a method for preparing the polyester resin described in the above technical solution, comprising the following steps: An esterification reaction is carried out by mixing polyol, polyacid and esterification catalyst to obtain an esterification solution; the acid value of the esterification solution is 30~34 mgKOH / g, and the viscosity at 175℃ is 1100~1300 mPa·s. The esterification solution is subjected to a polycondensation reaction to obtain a polycondensation solution; the acid value of the polycondensation solution is 16~18 mgKOH / g, and the viscosity at 200℃ is 1700~2300 mPa·s. The condensation solution and the end-capping anhydride are mixed to carry out an end-capping reaction to obtain an end-capping solution; the acid value of the end-capping solution is 48~52 mgKOH / g, and the viscosity at 200℃ is 1800~2400 mPa·s; The end-capping solution and curing accelerator are mixed to obtain a polyester resin.

[0012] Preferably, the temperature of the polycondensation reaction is 220~230℃; The polycondensation reaction is carried out under vacuum conditions; The vacuum conditions include a series of first, second, third, fourth, and fifth vacuum conditions. The vacuum degree of the first vacuum condition is -0.03 to -0.02 MPa, and the time is 10 to 30 minutes; The vacuum level of the second vacuum condition is -0.05 to -0.04 MPa, and the time is 10 to 30 minutes; The vacuum level of the third vacuum condition is -0.07 to -0.06 MPa, and the time is 10 to 30 minutes; The fourth vacuum condition has a vacuum level of -0.09 to -0.08 MPa and a duration of 10 to 30 minutes. The fifth vacuum condition has a vacuum level of -0.098 to -0.092 MPa and a duration of 1 to 3 hours.

[0013] This invention provides the application of the polyester resin described in the above technical solution or the polyester resin prepared by the above technical solution in thermosetting wrinkle powder coatings.

[0014] The present invention also provides a thermosetting wrinkle powder coating, comprising, by weight parts: The resin matrix consists of 520.8 to 651 parts, the curing agent consists of 39.2 to 49 parts, the wrinkle agent consists of 1 to 5 parts, the pigments and fillers consist of 87.3 to 157.3 parts, and the matting filler consists of 216.7 to 286.7 parts. The curing agent is a β-hydroxyalkylamide; The resin matrix is ​​the polyester resin described in the above technical solution or the polyester resin prepared by the preparation method described in the above technical solution.

[0015] This invention provides a polyester resin comprising, by weight, the following raw materials: 7-10.5 parts of polyol, 8-10 parts of polyacid, 1.5-3 parts of end-capping anhydride, 0.02-0.06 parts of esterification catalyst, and 0.5-1.5 parts of curing accelerator; wherein the structures of the polyol and polyacid are independently symmetrical about the C2 rotation axis; the esterification catalyst comprises alkoxytitanate and dibutyltin dichloride; the curing accelerator has a core-shell structure; the end-capping anhydride comprises naphthalenetetracarboxylic dianhydride; and the gelation time of the polyester resin at 140°C is 120-140 s. This invention employs polyols and polyacids with highly symmetrical structures (symmetric along the C2 rotation axis) as esterification monomers for polyester resins, improving the crystallinity of the polyester resin and enabling rapid texturing during curing. The use of a compound of alkoxytitanate and dibutyltin dichloride as an esterification catalyst gives the polyester resin a regular molecular structure and a narrow molecular weight distribution, making texturing easier during coating curing. The use of highly reactive naphthalenetetracarboxylic dianhydride as the end-capping anhydride after the polycondensation reaction enhances the activity of the end carboxyl groups of the polyester resin without altering the molecular chain symmetry, resulting in high reactivity and a good three-dimensional effect after texturing. The use of a core-shell structured curing accelerator enables conditional release, significantly improving the reactivity of the polyester resin. The polyester resin provided by this invention has a gelation time of 120~140s at 140℃ (tested according to GB / T16995-1997). When the polyester resin provided by this invention is used as a resin matrix in thermosetting wrinkle powder coatings, the high reactivity of the polyester resin enables the thermosetting wrinkle powder coatings to achieve low-temperature curing at 140℃ and complete curing in 15 minutes. Furthermore, the coating thickness remains good even when it exceeds 100μm. During the curing process, the polyester resin and wrinkle agent can fully wet and encapsulate each other, allowing the coating to quickly develop wrinkles with clear lines and a prominent three-dimensional effect. Moreover, when the polyester resin provided by this invention is used in thermosetting wrinkle powder coatings, the spraying application is not sensitive to oven temperature and heating rate, exhibiting high application tolerance and promising future prospects.

[0016] Furthermore, the method for preparing polyester resin described in the above-mentioned technical solution of the present invention removes the water vapor generated by the polycondensation reaction by carrying out the polycondensation reaction under step vacuum conditions, promotes the forward polycondensation reaction of the esterified monomer, and makes the obtained polyester resin have a regular molecular structure and a narrow molecular weight distribution width, thereby further improving the texture resistance of the coating. Detailed Implementation

[0017] This invention provides a polyester resin, comprising, by weight, the following raw materials: The composition includes 7-10.5 parts of polyol, 8-10 parts of polyacid, 1.5-3 parts of end-capped anhydride, 0.02-0.06 parts of esterification catalyst, and 0.5-1.5 parts of curing accelerator. The structures of the polyols and polyacids are independently symmetrical about the C2 rotational axis; The esterification catalyst includes alkoxytitanate and dibutyltin dichloride; The curing accelerator has a core-shell structure; The capped anhydride includes naphthalenetetracarboxylic dianhydride; The gelation time of the polyester resin at 140°C is 120~140s.

[0018] Unless otherwise specified, the materials and equipment used in this invention are all commercially available products in the field.

[0019] The polyester resin provided by this invention comprises 7 to 10.5 parts by weight, specifically 8, 9, or 10 parts of polyol. In this invention, the structure of the polyol is symmetrical about the C2 rotation axis.

[0020] In this invention, the polyol may include 7 to 8 parts of 1,4-butanediol, specifically 7.2, 7.5, or 7.8 parts by mass.

[0021] In this invention, based on 1 part by mass of the 1,4-butanediol, the polyol may include 0 to 2 parts of neopentyl glycol (i.e., the polyol may not include neopentyl glycol), specifically 0.5 parts, 1 part, or 1.5 parts.

[0022] In this invention, based on 1 part by mass of the 1,4-butanediol, the polyol may include 0 to 0.5 parts of 1,6-hexanediol, specifically 0.1, 0.2, or 0.3 parts.

[0023] Based on 1 part by mass of the polyol, the polyester resin provided by the present invention includes 8 to 10 parts of polyacid, specifically 8.5 parts, 9 parts or 9.5 parts.

[0024] In this invention, the polybasic acid may include 8-9 parts of terephthalic acid, specifically 8.2 parts, 8.5 parts or 8.8 parts, by mass.

[0025] In this invention, based on 1 part by mass of the terephthalic acid, the polybasic acid may include 0 to 1 part of isophthalic acid, specifically 0.2 parts, 0.5 parts or 0.8 parts.

[0026] In this invention, based on 1 part by mass of the terephthalic acid, the polyacid may include 0 to 2 parts of adipic acid, specifically 0.2 parts, 0.5 parts, or 0.8 parts.

[0027] Based on 1 part by mass of the polyol, the polyester resin provided by the present invention comprises 1.5 to 3 parts of end-capping anhydride, specifically 2 parts or 2.5 parts. In the present invention, the end-capping anhydride comprises naphthalenetetracarboxylic dianhydride.

[0028] In this invention, the capped anhydride may include 3 to 5 parts by mass, specifically 3.5 parts, 4 parts or 4.5 parts.

[0029] In this invention, based on 1 part by mass of the naphthalenetetracarboxylic dianhydride, the capping anhydride may include 0 to 2 parts of pyromellitic dianhydride, specifically 0.5 parts, 1 part, or 1.5 parts.

[0030] Based on 1 part by mass of the polyol, the polyester resin provided by the present invention includes 0.02 to 0.06 parts of esterification catalyst, specifically 0.03 parts, 0.04 parts, or 0.05 parts. In the present invention, the esterification catalyst includes alkoxytitanate and dibutyltin dichloride; the mass ratio of the alkoxytitanate and dibutyltin dichloride can be 2 to 4:1 to 2, specifically 1:1, 2:1, or 4:1.

[0031] Based on 1 part by mass of the polyol, the polyester resin provided by the present invention includes 0.5 to 1.5 parts of a curing accelerator, specifically 0.8 parts, 1 part, or 1.2 parts. In the present invention, the curing accelerator has a core-shell structure.

[0032] In this invention, the curing accelerator may comprise 2 to 5 parts, specifically 3 or 4 parts, of a quaternary phosphonium salt type curing accelerator by weight. In this invention, the core of the quaternary phosphonium salt type curing accelerator may be a quaternary phosphonium salt, and the shell may comprise an alternating copolymer of titanium dioxide and styrene-maleic anhydride; the alternating copolymer of titanium dioxide and styrene-maleic anhydride is grafted via covalent bonds.

[0033] In this invention, based on 1 part by mass of the quaternary phosphonium salt type curing accelerator, the curing accelerator may include 0 to 3 parts of a tertiary amine type curing accelerator, specifically 1 part or 2 parts. In this invention, the core of the tertiary amine type curing accelerator may be a tertiary amine, and the shell may be graphene nanosheets.

[0034] In this invention, the gelation time of the polyester resin at 140°C is 120~140s, specifically 125s, 130s, or 135s. The gelation time of the polyester resin at 140°C is tested according to GB / T16995-1997. The polyester resin provided by this invention has a short gelation time and high reactivity at 140°C. When used as a resin matrix in thermosetting wrinkle powder coatings, it enables the thermosetting wrinkle powder coatings to achieve low-temperature curing at 140°C.

[0035] This invention provides a method for preparing the polyester resin described in the above technical solution, comprising the following steps: An esterification reaction is carried out by mixing polyol, polyacid and esterification catalyst to obtain an esterification solution; the acid value of the esterification solution is 30~34 mgKOH / g, and the viscosity at 175℃ is 1100~1300 mPa·s. The esterification solution is subjected to a polycondensation reaction to obtain a polycondensation solution; the acid value of the polycondensation solution is 16~18 mgKOH / g, and the viscosity at 200℃ is 1700~2300 mPa·s. The condensation solution and the end-capping anhydride are mixed to carry out an end-capping reaction to obtain an end-capping solution; the acid value of the end-capping solution is 48~52 mgKOH / g, and the viscosity at 200℃ is 1800~2400 mPa·s; The end-capping solution and curing accelerator are mixed to obtain a polyester resin.

[0036] This invention involves mixing polyols, polyacids, and esterification catalysts to carry out an esterification reaction, thereby obtaining an esterification solution.

[0037] In this invention, the mixing process may further include preheating the polyol; the preheating temperature can be 110~120℃, specifically 112℃ or 115℃. This invention, by preheating the polyol, melts the solid polyol into a liquid state, facilitating subsequent reactions.

[0038] In this invention, the temperature of the esterification reaction can be 240~245℃, specifically 241℃, 242℃, 243℃, or 244℃. In this invention, the esterification reaction is completed when the top temperature of the reaction vessel containing the esterification feed solution reaches 80℃. This invention determines the endpoint of the esterification reaction by the top temperature of the reaction vessel. While the esterification reaction continues, the water vapor generated by the reaction continuously distills from the top of the reaction vessel, thus maintaining the top temperature at 100℃. When the esterification reaction is complete, no more water vapor evaporates from the top of the reaction vessel, and the top temperature decreases. When the top temperature drops to 80℃, the esterification reaction can be considered complete.

[0039] In this invention, the acid value of the esterification solution can be 30~34 mgKOH / g, specifically 31 mgKOH / g, 32 mgKOH / g, or 33 mgKOH / g; the viscosity of the esterification solution at 175°C can be 1100~1300 mPa·s, specifically 1150 mPa·s, 1200 mPa·s, or 1250 mPa·s. In this invention, the viscosity is measured using a cone-plate viscometer according to GB / T 9751.1-2008.

[0040] After obtaining the esterified solution, the present invention performs a polycondensation reaction on the esterified solution to obtain a polycondensation solution.

[0041] In this invention, the temperature of the polycondensation reaction can be 220~230℃, specifically 222℃, 225℃ or 228℃.

[0042] In this invention, the polycondensation reaction can be carried out under vacuum conditions; the vacuum conditions may include a first vacuum condition, a second vacuum condition, a third vacuum condition, a fourth vacuum condition, and a fifth vacuum condition.

[0043] The vacuum degree of the first vacuum condition is -0.03 to -0.02 MPa, and the time is 10 to 30 minutes; The vacuum level of the second vacuum condition is -0.05 to -0.04 MPa, and the time is 10 to 30 minutes; The vacuum level of the third vacuum condition is -0.07 to -0.06 MPa, and the time is 10 to 30 minutes; The fourth vacuum condition has a vacuum level of -0.09 to -0.08 MPa and a duration of 10 to 30 minutes. The fifth vacuum condition has a vacuum level of -0.098 to -0.092 MPa and a duration of 1 to 3 hours.

[0044] In this invention, the vacuum level of the first vacuum condition can be -0.03 to -0.02 MPa, specifically -0.028 MPa, -0.025 MPa, or -0.023 MPa; the duration of the first vacuum condition can be 10 to 30 minutes, specifically 15 minutes, 20 minutes, or 25 minutes; the vacuum level of the second vacuum condition can be -0.05 to -0.04 MPa, specifically -0.048 MPa, -0.045 MPa, or -0.043 MPa; the duration of the second vacuum condition can be 10 to 30 minutes, specifically 15 minutes, 20 minutes, or 25 minutes; the vacuum level of the third vacuum condition can be -0.07 to -0.06 MPa, specifically -0.068 MPa. The vacuum level of the third vacuum condition can be -0.065 MPa or -0.063 MPa; the duration of the third vacuum condition can be 10~30 min, specifically 15 min, 20 min or 25 min; the vacuum level of the fourth vacuum condition can be -0.09~-0.08 MPa, specifically -0.088 MPa, -0.085 MPa or -0.083 MPa; the duration of the fourth vacuum condition can be 10~30 min, specifically 15 min, 20 min or 25 min; the vacuum level of the fifth vacuum condition can be -0.098~-0.092 MPa, specifically -0.095 MPa or -0.093 MPa; the duration of the fifth vacuum condition can be 1~3 h, specifically 1.5 h, 2 h or 2.5 h. This invention removes water vapor generated during the polycondensation reaction by using a stepped vacuum condition, promoting the forward polycondensation reaction of the esterified monomers. This results in a polyester resin with a regular molecular structure and a narrow molecular weight distribution, further improving the reactivity of the polyester resin.

[0045] In this invention, the acid value of the polycondensation solution can be 16-18 mgKOH / g, specifically 16.5 mgKOH / g, 17 mgKOH / g, or 17.5 mgKOH / g; the viscosity of the polycondensation solution at 200°C can be 1700-2300 mPa·s, specifically 1800 mPa·s, 2000 mPa·s, or 2200 mPa·s. By controlling the viscosity of the polycondensation solution at 200°C to 1700-2300 mPa·s, this invention enables the polyester resin in the polycondensation solution to have a relatively low molecular weight, high reactivity, and better texturing effect.

[0046] After obtaining the condensation solution, the present invention mixes the condensation solution with the end-capping anhydride to carry out the end-capping reaction, thereby obtaining the end-capping solution.

[0047] In this invention, the temperature of the end-capping reaction can be 210~220℃, specifically 212℃, 215℃, or 218℃; the time of the end-capping reaction can be 0.5~1.5h, specifically 0.8h, 1h, or 1.2h. In this invention, the end-capping reaction is completed when the top temperature of the reaction vessel containing the end-capping feed solution is <50℃.

[0048] In this invention, the acid value of the end-capping solution can be 48~52 mgKOH / g, specifically 49 mgKOH / g, 50 mgKOH / g or 51 mgKOH / g; the viscosity of the end-capping solution at 200℃ can be 1800~2400 mPa·s, specifically 2000 mPa·s or 2200 mPa·s.

[0049] After obtaining the end-capping solution, the present invention mixes the end-capping solution with a curing accelerator to obtain a polyester resin. In the present invention, the mixing temperature can be 200~205℃, specifically 201℃, 202℃ or 203℃; the mixing time can be 0.2~1h, specifically 0.4h, 0.6h or 0.8h.

[0050] This invention provides the application of the polyester resin described in the above technical solution or the polyester resin prepared by the above technical solution in thermosetting wrinkle powder coatings.

[0051] The present invention also provides a thermosetting wrinkle powder coating, comprising, by weight parts: The resin matrix consists of 520.8 to 651 parts, the curing agent consists of 39.2 to 49 parts, the wrinkle agent consists of 1 to 5 parts, the pigments and fillers consist of 87.3 to 157.3 parts, and the matting filler consists of 216.7 to 286.7 parts. The resin matrix is ​​the polyester resin described in the above technical solution or the polyester resin prepared by the preparation method described in the above technical solution.

[0052] In this invention, the curing agent is β-hydroxyalkylamide; the wrinkle-reducing agent can be cellulose acetate butyrate; the pigments and fillers can be one or more of titanium dioxide, carbon black, iron oxide yellow, and titanium cyanine green; the mass ratio of titanium dioxide to carbon black can be 120~150:0.1~0.3, specifically 120:0.3, 130:0.2, 150:0.2, or 150:0.1; the mass ratio of titanium dioxide to iron oxide yellow can be 120~150:1~2, specifically 120:2, 130:2, 150:2, or 150:1; the mass ratio of titanium dioxide to titanium cyanine green can be 120~150:0.1~0.5, specifically 120:0.5, 130:0.3, 140:0.2, or 150:0.1; and the matting filler can be matting barium.

[0053] In a specific embodiment of the present invention, the thermosetting wrinkle powder coating comprises, by weight parts: 520.8 parts resin matrix, 39.2 parts curing agent, 1 part wrinkle agent, 150 parts titanium dioxide, 0.2 parts carbon black, 2 parts iron oxide yellow, 0.1 parts titanium cyanine green, and 286.7 parts matting barium. To further illustrate the present invention, the solutions provided by the present invention will be described in detail below with reference to the embodiments, but they should not be construed as limiting the scope of protection of the present invention.

[0054] In all embodiments of the present invention, terephthalic acid was purchased from Yisheng Dahua Petrochemical Co., Ltd. Isophthalic acid was purchased from Beijing Yanshan Petrochemical Co., Ltd. Adipic acid was purchased from Shandong Hualu Hengsheng Chemical Co., Ltd. 1,4-Butanediol was purchased from Shandong Jinyueyuan New Materials Co., Ltd. Neopentyl glycol was purchased from Wanhua Chemical (Yantai) Petrochemical Co., Ltd. 1,6-Hexanediol was purchased from Yuanli Chemical Group Co., Ltd. Alkoxy titanate was purchased from Nanjing Xuanhao New Materials Technology Co., Ltd. Dibutyltin dichloride was purchased from Nantong Haotai Chemical Products Co., Ltd. Naphthalenetetracarboxylic dianhydride was purchased from Shanghai Lingkai Technology Co., Ltd. Pyromellitic anhydride was purchased from Linyi Liuhuan Chemical Co., Ltd. The quaternary phosphonium salt type curing accelerator was purchased from Hubei Topband Chemical Co., Ltd. Its core is a quaternary phosphonium salt, and its shell consists of alternating copolymers of titanium dioxide and styrene-maleic anhydride; the alternating copolymers of titanium dioxide and styrene-maleic anhydride are grafted via covalent bonds. The tertiary amine type curing accelerator was purchased from Shandong Fuster Oil Technology Co., Ltd., with a tertiary amine core and a graphene nanosheet shell. The curing agent was T105 (β-hydroxyalkylamide), purchased from Ningbo Nanhai Chemical Co., Ltd. The wrinkle-reducing agent is cellulose acetate butyrate, purchased from Eastman Chemical Company, USA. The titanium dioxide was purchased from CNNC Huayuan Titanium Dioxide Co., Ltd. The carbon black was purchased from Shanxi Yangquan Carbon Black Co., Ltd. Iron yellow pigment was purchased from Tianjin Jifa Pigment Co., Ltd. Titanium cyanide was purchased from Shanghai Kaiyin Chemical Co., Ltd. The barium sulfate for matting was purchased from Guangdong Xinmei New Materials Co., Ltd. The viscosity of the liquid in each step was measured using a Boller Feinberg cone-plate viscometer, and the testing standard was GB / T 9751.1-2008.

[0055] The mass of the raw materials added in each step of Examples 1-5 is shown in Table 1, where 0 indicates that no raw material was added.

[0056] Table 1. Mass of raw materials added in each step of Examples 1-5 (unit: g)

[0057] Example 1 1,4-Butanediol and neopentyl glycol were added to the reactor and heated to 110°C to melt them. After melting, stirring was started, and terephthalic acid, isophthalic acid, alkoxytitanate and dibutyltin dichloride were added. The temperature was raised to 240°C to carry out the esterification reaction until the top temperature of the reactor dropped to 80°C, and the esterified solution was obtained with an acid value of 32 mg KOH / g and a viscosity of 1150 mPa·s at 175°C.

[0058] The obtained esterification solution was cooled to 230℃ and subjected to a polycondensation reaction under a stepped vacuum condition. The stepped vacuum condition program was as follows: 15 min under a vacuum condition of -0.02MPa, 15 min under a vacuum condition of -0.04MPa, 15 min under a vacuum condition of -0.06MPa, 15 min under a vacuum condition of -0.08MPa, and 1 h under a vacuum condition of -0.098MPa. The resulting polycondensation solution had an acid value of 16 mg KOH / g and a viscosity of 2250 mPa·s at 200℃.

[0059] The obtained polycondensation solution was cooled to 220℃, and naphthalene tetracarboxylic acid dianhydride was added. The end-capping reaction was carried out for 1.5 hours until the temperature at the top of the reactor dropped below 50℃, resulting in an end-capping solution with an acid value of 50 mg KOH / g and a viscosity of 2300 mPa·s at 200℃.

[0060] The obtained end-capping solution was cooled to 200~205℃, a quaternary phosphonium salt type curing accelerator was added, and the mixture was stirred for 0.5h to obtain polyester resin (denoted as polyester resin A).

[0061] Example 2 1,4-Butanediol, neopentyl glycol, and 1,6-hexanediol were added to the reactor and heated to 110°C to melt them. After melting, stirring was started, and terephthalic acid, isophthalic acid, alkoxytitanate, and dibutyltin dichloride were added. The temperature was raised to 245°C to carry out the esterification reaction until the top temperature of the reactor dropped to 80°C, resulting in an esterified solution with an acid value of 34 mg KOH / g and a viscosity of 1250 mPa·s at 175°C.

[0062] The obtained esterification solution was cooled to 225℃ and subjected to a polycondensation reaction under a stepped vacuum condition. The stepped vacuum condition program was as follows: 15 min under a vacuum condition of -0.02MPa, 15 min under a vacuum condition of -0.04MPa, 15 min under a vacuum condition of -0.06MPa, 15 min under a vacuum condition of -0.08MPa, and 3 h under a vacuum condition of -0.09MPa. The resulting polycondensation solution had an acid value of 18 mg KOH / g and a viscosity of 2350 mPa·s at 200℃.

[0063] The obtained polycondensation solution was cooled to 210℃, and naphthalene tetracarboxylic dianhydride and pyromellitic tetracarboxylic anhydride were added. The end-capping reaction was carried out for 1.5 hours until the temperature at the top of the reactor dropped below 50℃, and the end-capping solution was obtained with an acid value of 52 mg KOH / g and a viscosity of 2400 mPa·s at 200℃.

[0064] The obtained end-capping solution was cooled to 200~205℃, and quaternary phosphonium salt type curing accelerator and tertiary amine type curing accelerator were added. The mixture was stirred for 0.5h to obtain polyester resin (denoted as polyester resin B).

[0065] Example 3 1,4-Butanediol, neopentyl glycol, and 1,6-hexanediol were added to the reactor and heated to 110°C to melt them. After melting, stirring was started, and terephthalic acid, isophthalic acid, alkoxytitanate, and dibutyltin dichloride were added. The temperature was raised to 242°C to carry out the esterification reaction until the top temperature of the reactor dropped to 80°C, resulting in an esterified solution with an acid value of 33.5 mg KOH / g and a viscosity of 1200 mPa·s at 175°C.

[0066] The obtained esterification solution was cooled to 220℃ and subjected to a polycondensation reaction under a stepped vacuum condition. The stepped vacuum condition program was as follows: 15 min under a vacuum condition of -0.02MPa, 15 min under a vacuum condition of -0.04MPa, 15 min under a vacuum condition of -0.06MPa, 15 min under a vacuum condition of -0.08MPa, and 1.5 h under a vacuum condition of -0.095MPa. The resulting polycondensation solution had an acid value of 16.5 mgKOH / g and a viscosity of 2380 mPa·s at 200℃.

[0067] The obtained polycondensation solution was cooled to 215℃, and naphthalene tetracarboxylic dianhydride and pyromellitic tetracarboxylic anhydride were added. The end-capping reaction was carried out for 1.5 hours until the temperature at the top of the reactor dropped below 50℃, and the end-capping solution was obtained with an acid value of 49.5 mgKOH / g and a viscosity of 2400 mPa·s at 200℃.

[0068] The obtained end-capping solution was cooled to 200~205℃, and quaternary phosphonium salt type curing accelerator and tertiary amine type curing accelerator were added. The mixture was stirred for 0.5h to obtain polyester resin (denoted as polyester resin C).

[0069] Example 4 1,4-Butanediol and 1,6-hexanediol were added to the reactor and heated to 110°C to melt them. After melting, stirring was started, and terephthalic acid, alkoxytitanate, and dibutyltin dichloride were added. The temperature was raised to 245°C to carry out the esterification reaction until the top temperature of the reactor dropped to 80°C, resulting in an esterified solution with an acid value of 32.5 mg KOH / g and a viscosity of 1100 mPa·s at 175°C.

[0070] The obtained esterification solution was cooled to 210℃ and subjected to a polycondensation reaction under a stepped vacuum condition. The stepped vacuum condition program was as follows: 15 min under a vacuum condition of -0.02MPa, 15 min under a vacuum condition of -0.04MPa, 15 min under a vacuum condition of -0.06MPa, 15 min under a vacuum condition of -0.08MPa, and 3 h under a vacuum condition of -0.092MPa. The resulting polycondensation solution had an acid value of 17 mgKOH / g and a viscosity of 1750 mPa·s at 200℃.

[0071] The obtained polycondensation solution was cooled to 210℃, and naphthalene tetracarboxylic dianhydride and pyromellitic tetracarboxylic anhydride were added. The end-capping reaction was carried out for 1.5 hours until the temperature at the top of the reactor dropped below 50℃, and the end-capping solution was obtained with an acid value of 51 mg KOH / g and a viscosity of 1800 mPa·s at 200℃.

[0072] The obtained end-capping solution was cooled to 200~205℃, and quaternary phosphonium salt type curing accelerator and tertiary amine type curing accelerator were added. The mixture was stirred for 0.5h to obtain polyester resin (denoted as polyester resin D).

[0073] Example 5 1,4-Butanediol and neopentyl glycol were added to the reactor and heated to 110°C to melt them. After melting, stirring was started, and terephthalic acid, isophthalic acid, alkoxytitanate and dibutyltin dichloride were added. The temperature was raised to 240°C to carry out the esterification reaction until the top temperature of the reactor dropped to 80°C, and the esterified solution was obtained with an acid value of 33 mg KOH / g and a viscosity of 1180 mPa·s at 175°C.

[0074] The obtained esterification solution was cooled to 225℃ and subjected to a polycondensation reaction under a stepped vacuum condition. The stepped vacuum condition program was as follows: 15 min at a vacuum of -0.02 MPa, 15 min at a vacuum of -0.04 MPa, 15 min at a vacuum of -0.06 MPa, 15 min at a vacuum of -0.08 MPa, and 2.5 h at a vacuum of -0.094 MPa. The resulting polycondensation solution had an acid value of 17.5 mg KOH / g and a viscosity of 2000 mPa·s at 200℃.

[0075] The obtained polycondensation solution was cooled to 210℃, and naphthalene tetracarboxylic dianhydride and pyromellitic tetracarboxylic anhydride were added. The end-capping reaction was carried out for 1.5 hours until the temperature at the top of the reactor dropped below 50℃, and the end-capping solution was obtained with an acid value of 48.5 mgKOH / g and a viscosity of 2000 mPa·s at 200℃.

[0076] The obtained end-capping solution was cooled to 200~205℃, and quaternary phosphonium salt type curing accelerator and tertiary amine type curing accelerator were added. The mixture was stirred for 0.5h to obtain polyester resin (denoted as polyester resin E).

[0077] Comparative Example 1 Commercially available polyester resin, model number Qingtian NH-6353.

[0078] Table 2. Performance test results of the polyester resins prepared in Examples 1-5 and the polyester resin in Comparative Example 1.

[0079] Table 2 shows the performance test results of the polyester resins prepared in Examples 1-5 and the polyester resin in Comparative Example 1. As can be seen from Table 2, compared with the polyester resin in Comparative Example 1, the polyester resins prepared in Examples 1-5 have lower viscosity, lower molecular weight, and smaller molecular weight distribution width. The coating is more prone to cracking during the curing reaction.

[0080] The polyester resins obtained in Examples 1-5 and the polyester resin in Comparative Example 1 were sequentially applied to thermosetting wrinkle powder coatings. The polyester resin, curing agent, wrinkle agent, titanium dioxide, carbon black, iron oxide yellow, phthalocyanine green and barium sulfate were mixed according to the formulation shown in Table 3. The resulting thermosetting wrinkle powder coatings were sequentially labeled as coating 1, coating 2, coating 3, coating 4, coating 5 and coating 6 (where 0 indicates that the component was not added).

[0081] The obtained thermosetting wrinkle powder coating was extruded and pressed into sheets by a twin-screw extruder, then cooled, crushed, sieved, and electrostatically sprayed. The resulting coating was baked at 140℃ for 15 minutes. The resulting coatings were successively named coating 1, coating 2, coating 3, coating 4, coating 5, and coating 6.

[0082] Table 3. Distribution ratios of coatings 1-6 (unit: g)

[0083] The properties of the prepared coatings 1 to 6 were tested, and the test results are shown in Table 4.

[0084] Table 4 Performance test results of coatings 1-6

[0085] As shown in Table 4, the polyester resins prepared in Examples 1-5, when used as thermosetting wrinkle powder coatings, exhibit high reactivity, good adhesion to the substrate, large and clear texture, strong three-dimensionality, excellent bending and impact resistance, and low-temperature curing at 140℃ / 15min. They can be used for coating on heat-sensitive substrates such as medium-density fiberboard and have good application prospects.

[0086] The above description is only a preferred embodiment of the present invention. It should be noted that for those skilled in the art, several improvements and modifications can be made without departing from the principle of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. A polyester resin, characterized in that, The preparation materials include the following ingredients in parts by weight: The composition includes 7-10.5 parts of polyol, 8-10 parts of polyacid, 1.5-3 parts of end-capped anhydride, 0.02-0.06 parts of esterification catalyst, and 0.5-1.5 parts of curing accelerator. The structures of the polyols and polyacids are independently symmetrical about the C2 rotational axis; The esterification catalyst includes alkoxytitanate and dibutyltin dichloride; The curing accelerator has a core-shell structure; The capped anhydride includes naphthalenetetracarboxylic dianhydride; The gelation time of the polyester resin at 140°C is 120~140s.

2. The polyester resin according to claim 1, characterized in that, The polyol comprises the following components in parts by mass: 7-8 parts of 1,4-butanediol, 0-2 parts of neopentyl glycol, and 0-0.5 parts of 1,6-hexanediol.

3. The polyester resin according to claim 1, characterized in that, The polybasic acid comprises the following components in parts by mass: 8-9 parts terephthalic acid, 0-1 part isophthalic acid, and 0-2 parts adipic acid.

4. The polyester resin according to claim 1, characterized in that, The capped anhydride comprises the following components in parts by weight: 3-5 parts of naphthalenetetracarboxylic dianhydride and 0-2 parts of pyromellitic dianhydride.

5. The polyester resin according to claim 1, characterized in that, The curing accelerator comprises the following components in parts by weight: 2-5 parts of quaternary phosphonium salt type curing accelerator and 0-3 parts of tertiary amine type curing accelerator; The core of the quaternary phosphonium salt type curing accelerator is a quaternary phosphonium salt, and the shell comprises titanium dioxide and styrene-maleic anhydride alternating copolymers; the titanium dioxide and styrene-maleic anhydride alternating copolymers are grafted by covalent bonds; The core of the tertiary amine curing accelerator is a tertiary amine, and the shell is graphene nanosheets.

6. The polyester resin according to claim 1, characterized in that, The mass ratio of the alkoxytitanate to dibutyltin dichloride is 2~4:1~2.

7. A method for preparing the polyester resin according to any one of claims 1 to 6, characterized in that, Includes the following steps: An esterification reaction is carried out by mixing polyol, polyacid and esterification catalyst to obtain an esterification solution; the acid value of the esterification solution is 30~34 mgKOH / g, and the viscosity at 175℃ is 1100~1300 mPa·s. The esterification solution is subjected to a polycondensation reaction to obtain a polycondensation solution; the acid value of the polycondensation solution is 16~18 mgKOH / g, and the viscosity at 200℃ is 1700~2300 mPa·s. The condensation solution and the end-capping anhydride are mixed to carry out an end-capping reaction to obtain an end-capping solution; the acid value of the end-capping solution is 48~52 mgKOH / g, and the viscosity at 200℃ is 1800~2400 mPa·s; The end-capping solution and curing accelerator are mixed to obtain a polyester resin.

8. The preparation method according to claim 7, characterized in that, The temperature of the polycondensation reaction is 220~230℃; The polycondensation reaction is carried out under vacuum conditions; The vacuum conditions include a series of first, second, third, fourth, and fifth vacuum conditions. The vacuum degree of the first vacuum condition is -0.03 to -0.02 MPa, and the time is 10 to 30 minutes; The vacuum level of the second vacuum condition is -0.05 to -0.04 MPa, and the time is 10 to 30 minutes; The vacuum level of the third vacuum condition is -0.07 to -0.06 MPa, and the time is 10 to 30 minutes; The fourth vacuum condition has a vacuum level of -0.09 to -0.08 MPa and a duration of 10 to 30 minutes. The fifth vacuum condition has a vacuum level of -0.098 to -0.092 MPa and a duration of 1 to 3 hours.

9. The use of the polyester resin according to any one of claims 1 to 6 or the polyester resin prepared by the preparation method according to any one of claims 7 to 8 in thermosetting wrinkle powder coatings.

10. A thermosetting wrinkle powder coating, characterized in that, By weight, it includes: The resin matrix consists of 520.8 to 651 parts, the curing agent consists of 39.2 to 49 parts, the wrinkle agent consists of 1 to 5 parts, the pigments and fillers consist of 87.3 to 157.3 parts, and the matting filler consists of 216.7 to 286.7 parts. The curing agent is a β-hydroxyalkylamide; The resin matrix is ​​the polyester resin according to any one of claims 1 to 6 or the polyester resin prepared by the preparation method according to any one of claims 7 to 8.

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